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BACKGROUND: Cardiovascular disease (CVD) risk factor awareness and knowledge are believed to be prerequisites for adopting healthy lifestyle behaviors. The purpose of this study was to examine knowledge of CVD risk factors and risk perception among individuals with high CVD risk. METHODS: The sample consisted of inner city and rural medically underserved patients at high risk of CVD. To be eligible for the trial, subjects were required to have a 10% or greater CVD risk on the Framingham risk score. Knowledge of CVD was assessed with a 29-item questionnaire created for this study. Subjects also rated their perception of risk as compared with individuals of their own sex and age. RESULTS: Data were collected from 465 subjects (mean [SD] age, 60.5 [10.1] years; mean [SD] Framingham risk score, 17.3% [9.5%]). The mean (SD) CVD knowledge score was 63.7% (14.6%), and mean (SD) level of risk perception was 0.35 (1.4). Men and women had similar Framingham risk scores, but women perceived their risk to be significantly higher than that of their male counterparts. Women were also more knowledgeable than men about CVD. Urban participants had significantly higher actual risks than did their rural counterparts (18.2% [10.7%] vs 16.0% [8.9%], respectively; P = .01) but were significantly less knowledgeable about heart disease and also perceived their risk to be lower. CONCLUSIONS: These results indicate a low perception of risk and cardiovascular knowledge especially among men and inner city residents. Innovative educational strategies are needed to increase risk factor knowledge and awareness among at-risk individuals. [ABSTRACT FROM AUTHOR]

We examined the frequency of use by patients of a web-based reporting system to monitor and control cardiovascular disease (CVD) risk factors. A total of 192 patients with intermediate or high CVD risk were categorized into four quartiles based on their frequency of use of the telemedicine reporting system over one year. The lowest frequency users (Quartile I) averaged 17 reporting days in one year and the highest frequency users (Quartile IV) averaged 211 reporting days in one year. Factors associated with more frequent use were overall knowledge of CVD (P = 0.014), blood lipids (P = 0.017), smoking (P = 0.036), higher scores in medication self-efficacy (P = 0.016) and higher income (P = 0.002). All quartiles showed trends of decreasing systolic blood pressure from hypertensive (≥140 mm Hg) to pre-hypertensive (<140) ranges. Patients were able to lower CVD risk with as few as two transmissions per month using the telemedicine system. Telemedicine reporting coupled with self-assessment of health status can promote a strong patient-provider partnership for managing the chronic risk factors of CVD.

Background: We evaluated an Internet- and telephone-based telemedicine system for reducing blood pressure (BP) in underserved subjects with hypertension., Methods: A total of 241 patients with systolic BP ≥140 mm Hg were randomized to usual care (C; n = 121) or telemedicine (T; n = 120). The T group reported BP, heart rate, weight, steps/day, and tobacco use twice weekly. The primary outcome was BP control at 6 months., Results: Average age was 59.6 years, average body mass index was 33.7 kg/m(2), 79% were female, 81% were African American, 15% were white, 53% were at or below the federal poverty level, 18% were smokers, and 32% had diabetes. Six-month follow-up was achieved in 206 subjects (C: 107, T: 99). Goal BP was achieved in 52.3% in C and 54.5% in T (P = .43). Systolic BP change (C: -13.9 mm Hg, T: -18.2; P = .118) was similar in both groups. Subjects in the T group reported BP 7.7 ± 6.9 d/mo. Results were not affected by age, sex, ethnicity, education, or income. In nondiabetic T subjects, goal BP was achieved in 58.2% compared with 45.2% of diabetic T subjects (P = .024). Nondiabetic T subjects demonstrated a greater reduction in systolic BP (T: -19 ± 20 mm Hg, C: -12 ± 19 mm Hg; P = .037). No difference in BP response between C and T was noted in patients with diabetes., Conclusion: In hypertensive subjects, engagement in a system of care with or without telemedicine resulted in significant BP reduction. Telemedicine for nondiabetic patients resulted in a greater reduction in systolic BP compared with usual care. Telemedicine may be a useful tool for managing hypertension particularly among nondiabetic subjects., (Copyright © 2013 Mosby, Inc. All rights reserved.)

Aim: Clinical measures of cardiovascular disease risk (CVD) are important tools for establishing therapy to lower CVD risk. Risk assessment has come under criticism because clinical measures can underestimate or overestimate CVD risk. We assessed CVD risk in 252 subjects without evidence of CVD to establish therapy of one or more risk factors from clinical indications. The subjects all had intermediate CVD risk using the Framingham score., Results: Average age was 59.1 years. 23.8% were smokers, 59.1% were hypertensive, 65.1% had hyperlipidemia. BMI was greater than 30 kg/M(2) in 56% and diabetes was present in 43.7%. In this cohort, 86.9% required therapy for hypertension or hyperlipidemia, and this proportion increased to 95.6% when subjects with diabetes were included. Of the remaining 4.4% (11 subjects), 7 reached intermediate risk based on cigarette smoking and 4 based on age >65 years old. Among diabetics, 94/110 had another risk factor and would require statin and ACE or ARB therapy., Conclusions: Of subjects at intermediate risk for CVD, 98.4% would not require further testing to decide on therapy to lower CVD risk. Although 16 diabetic subjects had no other risk factors, current guidelines suggest that these subjects should be treated to reduce CVD risk.

Objectives: The aim of this study is to evaluate methods for lowering cardiovascular disease (CVD) risk in asymptomatic urban and rural underserved subjects., Background: Medically underserved populations are at increased CVD risk, and systems to lower CVD risk are needed. Nurse management (NM) and telemedicine (T) systems may provide low-cost solutions for this care., Methods: We randomized 465 subjects without overt CVD, with Framingham CVD risk >10% to NM with 4 visits over 1 year, or NM plus T to facilitate weight, blood pressure (BP), and physical activity reporting. The study goal was to reduce CVD risk by 5%., Results: Three hundred eighty-eight subjects completed the study. Cardiovascular disease risk fell by ≥ 5% in 32% of the NM group and 26% of the T group (P, nonsignificant). In hyperlipidemic subjects, total cholesterol decreased (NM -21.9 ± 39.4, T -22.7 ± 41.3 mg/dL) significantly. In subjects with grade II hypertension (systolic BP ≥ 160 mm Hg, 24% of subjects), both NM and T groups had a similar BP response (average study BP: NM 147.4 ± 17.5, T 145.3. ± 18.4, P is nonsignificant), and for those with grade I hypertension (37% of subjects), T had a lower average study BP compared to NM (NM 140.4 ± 16.9, T 134.6 ± 15.0, P = .058). In subjects at high risk (Framingham score ≥ 20%), risk fell 6.0% ± 9.9%; in subjects at intermediate risk (Framingham score ≥ 10, < 20), risk fell 1.3% ± 4.5% (P < .001 compared to high-risk subjects). Medication adherence was similar in both high- and intermediate-risk subjects., Conclusions: In 2 underserved populations, CVD risk was reduced by a nurse intervention; T did not add to the risk improvement. Reductions in BP and blood lipids occurred in both high- and intermediate-risk subjects with greatest reductions noted in the high-risk subjects. Frequent communication using a nurse intervention contributes to improved CVD risk in asymptomatic, underserved subjects with increased CVD risk. Telemedicine did not change the effectiveness of the nurse intervention., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Purpose: The purpose of this study was to examine gender-based differences in cardiovascular risk factors and risk perception among individuals with diabetes., Methods: The sample consisted of patients with an established history of diabetes who were enrolled in a telemedicine trial to reduce cardiovascular disease (CVD) risk. All subjects had a 10% or greater risk on the Framingham risk index. Assessments included blood pressure, A1C, lipid profile, medication history, and knowledge and risk perception surveys., Results: Data were available for 211 individuals with type 2 diabetes (88 men and 123 women). The women and men did not differ in age, body mass index, or Framingham risk. Only 37.4% of women and 40.9% of men were at an A1C target of <7%. Total cholesterol levels were significantly higher among women, and fewer women were at low-density lipoprotein or blood pressure targets. Knowledge of CVD was similar between the 2 sexes. However, women perceived their risk for CVD to be significantly higher than did men., Conclusion: Less favorable cardiovascular risk profiles are observed among women with diabetes as compared with their male counterparts. Multifaceted approaches to both diabetes management and education are needed to target CVD risk reduction among individuals with diabetes.

In underserved populations, inadequate surveillance and treatment allows hypertension to persist until actual cardiovascular events occur. Thus, we developed an Internet-based telemedicine system to address the suboptimal control of hypertension and other modifiable risk factors. To minimize cost, the subjects used home monitors for blood pressure (BP) measurements and entered these values into the telemedicine system. We hypothesized that patients could accurately measure their BP and transmit these values via a telemedicine system. Inner city and rural subjects (N = 464; 42% African-American or Hispanic) with 10% or greater 10-year risk of cardiovascular disease and with treatable risk factors were randomized into two groups, control group (CG) and telemedicine group (TG). Each subject received a home sphygmomanometer with memory. The TG recorded and entered BP at least weekly. During office visits, the BP meters were downloaded and recorded BP compared to BP values transmitted via telemedicine. The telemedicine (T) BP values were similar to the meter recorded (R) values (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and R: systolic/diastolic BP 136.4 +/- 11.9.4/79.7 +/- 7.5 mm Hg). The percent error was <1% for both systolic (-0.02 +/- 0.04%) and diastolic (-0.03 +/- 0.04%) BP. Lastly, the telemedicine BP values were similar to the office (O) BP values for systolic and diastolic BP (T: systolic/diastolic BP 133.4 +/- 11.1/77.5 +/- 6.8 mm Hg, and O: systolic/diastolic BP 136.3 +/- 20.5/78.1 +/- 10.5 mm Hg). In underserved populations, this inexpensive approach of patients using a home monitor and entering these values into a telemedicine system provided accurate BP data.

Background: Managing patients with heart failure (HF) is labor intensive, and follow-up is often inadequate to detect day-to-day changes that ultimately lead to decompensation. We tested the effect of an Internet-based telemedicine (T) system that provides frequent surveillance and increased communicate between HF patients and their provider on frequency of hospitalization in a cohort of patients with advanced HF., Methods and Results: HF patients in NYHA Class II-IV were randomized to usual care (UC, n = 24) or T (T plus UC, n = 24) and followed for 1 year. Office visits, emergency department visits, hospitalizations, telephone calls, and number of Internet communications were measured over the 1-year period. Left ventricular ejection fraction (EF) was assessed by echocardiography in both groups. For T, mean age was 53.2 +/- 2.0 years (72% male, 61% Caucasian, 39% African American). For UC, mean age was 54.1 +/- 2.6 years (76% male, 72% Caucasian, 14% African American, and 14% Hispanic). HF etiologies and EF were similar in both groups. During the 12-month period, UC had 74 total phone calls to the practice, whereas T had 88 telephone calls plus 1887 telemedicine data messages (6.5 messages/patient/month). ER visits were lower in the T group (T 5, UC 12; P < .05). Hospital admissions (T 24, C 40; P = .025) and total hospital days (T 84, UC 226 days; P < .005) were lower in T. Unscheduled clinic visits (T 13, UC 13; P = NS) and scheduled clinic visits (T 78, UC 94; P = NS) were similar in both groups., Conclusions: Frequent monitoring and patient management using a telemedicine system may help to reduce hospitalizations, hospital days, and emergency department visits.

Objective: The thermodilution technique provides a convenient means to monitor cardiac output, right ventricular (RV) ejection fraction (EF), and volumes at the bedside. To calculate RVEF from the pulmonary artery temperature curve, the bolus thermodilution technique assumes that right atrial (RA) temperature returns to baseline value within 1 beat following the cold saline injection. The authors hypothesized that this assumption is the reason why the thermodilution technique consistently underestimates RVEF., Design: A theoretical analysis and animal study., Setting: Laboratory, university, multi-institutional., Participants: Animals., Interventions: Cold saline injections., Measurements and Main Results: In 2 porcine experiments, after a rapid injection of cold saline into right atrium, RA temperature took several heartbeats to return to baseline. In a theoretical analysis, if after the cold saline injection RA temperature returned to baseline in 1 beat (RAEF = 1), then thermodilution-derived RVEF(T) = actual RVEF(A). In contrast, if RA temperature took several beats to return to baseline (RAEF = RVEF), then RVEF(T) consistently underestimated RVEF(A). A least square fit of RVEF(A) versus RVEF(T) resulted in RVEF(A) = 1.0 x RVEF(T) + 0.11. Applying this correction (adding 0.11 to RVEF(T)) to the data gave relatively small errors in estimating RVEF over a wide EF range., Conclusions: After injecting cold saline into the right atrium, RA temperature takes several heart beats to return to baseline temperature, leading to underestimating RVEF and overestimating RV volumes. The pulsed thermal energy approach by injecting heat into the RV avoids these problems, but the impact of its small temperature signal on RVEF measurements needs to be determined.

A toolbox for Matlab Simulink (trademark of Mathworks corp. etc.) was developed to simulate various models of flow in the cardiovascular system and study effects of different pathological conditions. The toolbox was based on well-known analog lumped models of blood flow in vessels, the varying elastance heart model, blood flow through vessels, shunts, and valves as well as models of oxygen exchange at lungs and tissue. The toolbox is modular providing the basic building blocks of the cardiovascular system. Parameters for the individual components may be set by the user to adapt the component to the simulated system. Several examples are shown. This modeling system is described and is also available for downloading as an open source for free use. The authors see this as the basis for wide collaboration and standardization in modeling. A web site will be available for accepting contributions from other researchers and to create a free exchange.

Background: Internet technology has been proven to be a successful tool for the management of patients with multiple medical conditions. The purpose of this study was to demonstrate the feasibility of monitoring glucose control in indigent women with gestational diabetes mellitus (GDM) over the Internet., Methods: Women with GDM were randomized to either the Internet group (n = 32) or the control group (n = 25). Patients in the Internet group were provided with computers and/or Internet access if needed. A website was established for documentation of glucose values and communication between the patient and the health care team. Women in the control group maintained paper logbooks, which were reviewed at each prenatal visit. Maternal feelings of diabetes self-efficacy were assessed at study entry and again before delivery., Results: Women in the Internet group accessed the system and sent on average 21.8 (+/- 16.9) sets of data. There was no difference between the two groups in regards either fasting or post-prandial blood glucose values, although more women in the Internet group received insulin therapy (31% vs. 4%; P <0.05). There were also no significant differences in pregnancy and neonatal outcomes between the two groups. Women in the Internet group demonstrated significantly higher feelings of self-efficacy at the study's end., Conclusions: The benefit of monitoring blood glucose in indigent women with GDM via the Internet was limited by their infrequent use of the telemedicine system. Although system use was not associated with improved pregnancy outcomes, women in the telemedicine group did experience enhanced feelings of diabetes psychosocial self-efficacy.

Cardiovascular disease is the leading cause of morbidity and mortality in the USA. Disease management programs, while successful, are intensive and expensive. Follow-up is often inadequate, incomplete, and inconsistent. To address these problems, we developed an Internet-Telemedicine system. Patients send/receive data to/from their care provider via the Internet. The system optimizes function and minimizes cost (all hardware is off the shelf and FDA approved). We are currently using this Telemedicine system in a prospective, randomized clinical trial, to reduce CVD risk in medically underserved populations. Over an 8-month time interval, we found very high rates of usage of the Telemedicine system (92%). This rate of self-monitoring greatly exceeded the self-monitoring rate in controls (48%). The patient-entered Telemedicine blood pressure values were similar to the meter recorded values and to the office values.

An Internet-based store-and-retrieval telemedicine system to communicate between patients and their healthcare provider was tested. The system requires no specialized equipment, is Web-based, and allows frequent surveillance of the health status of the patients with heart failure (HF). Thirty six patients were recruited to evaluate a Web-based telemedicine system for reducing care encounters. Eighteen patients were randomized to the telemedicine arm (group T), and 18 were given usual clinical care (group C) in our HF center. Patients in group T reported three times weekly via a secure Internet site for telemedicine intervention. We studied patients with HF with New York Heart Association (NYHA) class 2 to 4 with hospitalization within past 6 months. Mean age was 56.1 +/- 12.6 years (66.7% male; 66.7% Caucasian, 27.8% African American, and 5.6% Hispanic). Mean ejection fraction (EF) was 23.9% +/- 17.6% in group T and 26.6% +/- 16.4% in group C. Over an 8-month period, unscheduled (group T-3; group C-5), and scheduled clinic visits (group T-11, group C-7) were similar (p = NS); one group T patient was transplanted, one group C patient died. Total hospital days were lower with group T (44 days) compared to group C (133 days), p < 0.05. An Internet-based telemedicine system was able to closely monitor patients with HF. Surveillance through Internet-based telemedicine resulted in less hospitalization compared to control patients. This system may be helpful in reducing the cost of HF patient care.

Heart failure (HF) continues to place significant demands on health care resources because of the large number of hospital admissions for HF, the growth of the elderly population with HF, and the improved survival of patients with chronic heart disease who develop HF that requires continuous care. Because HF is best managed using a disease management approach, frequent communication is an important component of care. A variety of studies using the telephone to maintain communication have demonstrated reduced hospital admissions and improved morbidity rate. Hardware monitoring systems that can record vital signs and transmit information from the home to a data center have also demonstrated their value in HF care, but such systems become expensive when considered for large populations of HF patients. Most HF patients can transmit their vital signs, weight, and symptoms to a practice data center using the Internet with no specialized hardware other than a sphygmomanometer and a scale. We have used such a system to monitor HF patients and have provided care instructions using the same system. With use of an Internet communication system, it is possible to reduce hospitalizations and maintain a stable HF status without frequent office visits.

For underserved populations, telemedicine can address the high prevalence and suboptimal control of cardiovascular disease (CVD) risk factors. However, Internet access issues may limit the successful application of telemedicine. We tested the hypothesis that computer skills, and not access per se, was the main obstacle to using the Internet for health care. After informed consent, 44 participants with little or no computer experience received 2 hours of training covering 14 basic computer use skills, Internet access, and our telemedicine system. The telemedicine system enables reporting blood pressure, weight, physical activity, cigarette use, provider feedback, personal medication information, and educational information about CVD risk factors. The patient population included 12 males and 32 females. Of this total were 23 African Americans. The average patient age was 60.4 +/- 3 years, and 64% had annual family incomes under 25,000 dollars. Eighty-two percent of the participants averaged 4 or higher (on a scale of 1 to 5) on basic computer skills. Only 11% had an average score below 3. Thirty-seven of 44 participants reported on their health status from a local Internet access site within 10 days. Participants' successful use of the telemedicine system was not correlated with age, gender, education level, or ownership of a computer. Computer skill score had a positive effect on system use. Underserved populations without computer experience or skills and at increased risk for CVD can be educated to use an Internet telemedicine system to communicate health status to their health care providers. Ownership of a computer was not a factor that predicted system use.

Heart failure constitutes the most frequent and expensive hospital discharge diagnosis in the United States, costing annually over $10 billion. Optimal care requires an understanding of their illness, participating in clinical decisions, and frequent communication. Current surveillance is labor intensive and expensive. Follow-up is often inadequate, incomplete, and inconsistent. To address these problems, we developed an Internet-based telemedicine system, consisting of a secure server and database. Patients send or receive data to or from their care provider via the Internet. The system optimizes function and minimizes cost (all hardware is off the shelf and FDA approved). This paper describes our initial experience with this system. We are currently using this telemedicine system in a prospective, randomized clinical trial, comparing Class III or IV heart failure patients with standard care versus standard care plus telemedicine.

Background: We tested whether the CardioClasp, a passive non-blood-contacting device could decrease excessive geometric burden in dilated cardiomyopathy and improve left ventricular systolic function and contractility by reshaping the left ventricle (LV) and by decreasing LV wall stress (LVWS) without decreasing arterial blood pressure., Methods: In mongrel dogs (n = 6, the early group; n = 6, the chronic group; 25-27 kg), 4 weeks of rapid right ventricular pacing (210 to 240 bpm) induced dilated cardiomyopathy with heart failure. In the early group, we used hemodynamic data and echocardiography to evaluate LV systolic function immediately after placing the CardioClasp device. In the chronic group, we also evaluated LV systolic function immediately after placing the device on dilated hearts and then left the device in place for 30 days. At the end of 30 days, before explantation of the device, we again assessed LV systolic function. We measured fractional area of contraction (FAC), LVWS, and hemodynamic data in both groups., Results: In the early group, use of the CardioClasp device decreased the LV end-diastolic anterior-to-posterior dimension by 27.8% +/- 2.6% at implantation (p < 0.05). In the chronic group, use of the CardioClasp decreased the LV end-diastolic anterior-to-posterior dimension by 19.4% +/- 2.0% at implantation (p < 0.05) and by 22.0% +/- 3.10% at explantation (p < 0.05). Use of the CardioClasp did not alter LV end-diastolic and peak pressure, LV dP/dts, or cardiac output at implantation or at explantation. In the early group, use of the CardioClasp decreased the LVWS by 43.4% +/- 3.1% at implantation (p < 0.05). In the chronic group, LVWS decreased by 28.8% +/- 2.1% at implantation (p < 0.05) and by 43.3% +/- 5.2% at explantation (p < 0.05). In the early group, FAC increased significantly, by 28.9% +/- 7.8% at implantation (p < 0.05). In the chronic group, FAC increased significantly, by 18% +/- 12% at implantation (p < 0.05) and by 19% +/- 12% at explantation (p < 0.05)., Conclusions: As expected, use of the CardioClasp device increased FAC and decreased LVWS by reshaping the LV. Use of the CardioClasp device maintained cardiac output and arterial pressure. In 30-day experiments, the increased FAC and decreased LVWS were maintained at explantation.

Background: In dilated cardiomyopathy (DCM), eliminating or reducing extra-geometric burden to the myocardial cells would directly reduce myocardial wall stress leading to improved LV systolic performance. In acute experiments, we tested whether a passive non-blood contacting CardioClasp device, which employs two indenting bars to reshape the left ventricle (LV), could reduce extra-geometric burden, LV wall stress (LVWS) and improve LV systolic function and contractility without decreasing arterial blood pressure., Methods: In mongrel dogs (n = 5), 4 weeks of right ventricular pacing (210-220-230-240 ppm) induced DCM with severe heart failure. After placing the CardioClasp device, LV performance was evaluated immediately by measuring hemodynamics, echocardiography, and Sonometrics crystal data. Eleven sonometric crystals were placed into endocardial positions (8 in anterior, posterior, mid-anterior, mid-posterior, apex, base, free and septal wall) and in myocardial (2 as regional) and epicardial (1) positions to assess the LV end-systolic pressure-segment length relationships (ESPSR) and cross-sectional area (ESPAR) relationship., Results: CardioClasp decreased the LV end-diastolic anterior-posterior (A-P) dimensions at two levels (15% and 25%). With CardioClasp, LVWS decreased from 93.1 +/- 7.2 to 59.1 +/- 3.2 g/cm2 (P < 0.05) and fractional area of contraction (FAC) increased from 27.6 +/- 3.8 to 33.1 +/- 3.7% (P < 0.01). Peak LV and arterial pressures, LV +dP/dt, LV -dP/dt, and cardiac output were unaltered with CardioClasp. CardioClasp placement significantly increased the slopes of LV pressure versus anterior-posterior segment relationship from 7.3 +/- 0.6 to 15.8 +/- 1.8 mmHg/mm and septal-free wall segment relationship from 6.3 +/- 0.9 to 9.8 +/- 0.5 mmHg/mm. At both 15% and 25% LV A-P dimension reductions, the slopes of ESPAR showed significant steepening and increased from 10.1 +/- 0.7 (baseline) to 15.5 +/- 1.7 (15% reduction) and 19.0 +/- 1.4 mmHg/cm2 (25% reduction). The larger the reduction, the greater was the steepening of the slopes of ESPSR and ESPAR., Conclusions: CardioClasp reduced LV diameter and thereby decreased LVWS and increased FAC. CardioClasp was able to reshape the left ventricle, while preserving the contractile mass, which increased the slopes of ESPSR and ESPAR. This reshaping was associated with maintained systolic pressures, cardiac output, and increased contractility.

Objective: If the geometric distortion during dilated heart failure could be corrected, the tension on the myocytes would be decreased, thereby leading to an improvement in left ventricular systolic function. We tested the effects of the CardioClasp (CardioClasp Inc, Pine Brook, NJ), a left ventricular reshaping device, on the failing heart, and our empirical data were compared with computationally derived data., Methods: Heart failure was induced by 4-week rapid cardiac pacing. At the terminal experiment, an isolated failing heart preparation (isovolumic contraction, n = 5) or an intact failing heart in vivo (n = 7) was used. The effects of the reshaping device on left ventricular performance were assessed by the slopes (Ees) of the left ventricular end-systolic pressure-volume relations, hemodynamics, and echocardiograph before and after placing the CardioClasp on the heart. The change in Ees as the result of left ventricular reshaping was also estimated from computed theoretical analysis and compared with empirical data., Results: There was a significant change in left ventricular dimension after placing the CardioClasp on the heart. In isolated heart preparation, Ees significantly increased from 1.40 +/- 0.44 mm Hg/mL to 2.42 +/- 0.63 mm Hg/mL after placing the device on the heart but returned to the baseline level (1.46 +/- 0.27 mm Hg) after removing it. Left ventricular developed pressure and left ventricular fractional area shortening were significantly increased as the result of left ventricular reshaping. Ees derived from computed theoretical analysis was highly correlated with confirming empirical data., Conclusions: The CardioClasp can reshape the left ventricle and improve left ventricular systolic performance in failing hearts.

Objective: We tested whether the CardioClasp device (CardioClasp, Inc, Cincinnati, Ohio), a non-blood contact device, would improve left ventricular contractility by acutely reshaping the left ventricle and reducing left ventricular wall stress., Methods: In dogs (n = 6) 4 weeks of ventricular pacing (210-240 ppm) induced severe heart failure. Left ventricular function was evaluated before and after placement of the CardioClasp device, which uses 2 indenting bars to reshape the left ventricle. Hemodynamics, echocardiography, and Sonometrics crystals dimension (Sonometrics Corporation, London, Ontario, Canada) were measured at steady state and during inferior vena caval occlusion., Results: The CardioClasp device decreased the left ventricular end-diastolic anterior-posterior dimension by 22.8% +/- 1.9%, decreased left ventricular wall stress from 97.3 +/- 22.8 to 67.2 +/- 7.7 g/cm(2) (P =.003), and increased the fractional area of contraction from 21.3% +/- 10.5% to 31.3% +/- 18.1% (P =.002). The clasp did not alter left ventricular end-diastolic pressure, left ventricular pressure, left ventricular dP/dt, or cardiac output. With the CardioClasp device, the slope of the end-systolic pressure-volume relationship was increased from 1.87 +/- 0.47 to 3.22 +/- 1.55 mm Hg/mL (P =.02), the slope of preload recruitable stroke work versus end-diastolic volume was increased from 28.4 +/- 11.0 to 44.1 +/- 23.5 mm Hg (P =.02), and the slope of maximum dP/dt versus end-diastolic volume was increased from 10.6 +/- 4.6 to 18.6 +/- 7.4 mm Hg x s(-1) x mL(-1) (P =.01). The CardioClasp device increased the slope of the end-systolic pressure-volume relationship by 68.0% +/- 21.7%, the slope of preload recruitable stroke work versus end-diastolic volume by 50.7% +/- 18.1%, and the slope of maximum dP/dt versus end-diastolic volume by 85.7% +/- 28.9%., Conclusions: The CardioClasp device decreased left ventricular wall stress and increased the fractional area of contraction by reshaping the left ventricle. The CardioClasp device was able to maintain cardiac output and arterial pressure. The clasp increased global left ventricular contractility by increasing the slope of the end-systolic pressure-volume relationship, the slope of preload recruitable stroke work versus end-diastolic volume, and the slope of maximum dP/dt versus end-diastolic volume. In patients with heart failure, the CardioClasp device might be effective for clinical application.

In dilated heart failure, geometric distortions place an extra load on the myocardial cells. If this extra burden can be eliminated, the myocardial wall stress would decrease leading to improved systolic ventricular performance. In a dilated heart failure model, we wanted to see whether the CardioClasp (which uses two indenting bars to reshape the left ventricle [LV] as two widely communicating "lobes" of reduced radius) could improve systolic performance by passively reshaping the LV and reducing the wall stress. In mongrel dogs (n = 7; 25-27 kg), rapid ventricular pacing (210 ppm 1st week to 240 ppm 4th week) induced dilated heart failure. After 4 weeks, LV performance was evaluated at baseline and with the CardioClasp by measuring LV end-diastolic and peak LV systolic pressure, LV +dP/dt, LV -dP/ dt, and cardiac output. With the Clasp on, LV wall stress was reduced to 58.6+/-3.5 from 108.3+/-8.2 g/cm2. The fractional area of contraction (FAC) with the Clasp on (28.4+/-4.4) was significantly increased (p < 0.05) from baseline (20.8+/-4.6) and consistent with improved systolic performance. Cardiac output, LV peak systolic and end-diastolic pressures, and regional myocardial blood flow were unaltered. The Clasp was able to acutely reshape the left ventricle, while preserving the contractile mass, and reduced the tension on the myocardial cells and increased the fractional area of contraction without decreasing the systolic blood pressure.

We hypothesized that a two-stage vascular delay procedure followed by 5 weeks of conditioning of the latissimus dorsi muscle (LDM) could benefit the heart during the training period and greatly increase cardiac assistance when examined with maximum potential. In mongrel dogs (n = 10), left ventricle (LV) dysfunction was induced by intracoronary injections of latex microspheres [90 +/- 2 micro diameter]. Vascular delay of the LDM was performed in one group (n = 6), whereas the other group (control, n = 4) did not undergo vascular delay. After 2 weeks, CMP was performed in all animals followed by LDM conditioning. After 5 weeks of muscle training, we examined left ventricular function at 20 Hz-4 volts, 33 Hz-4 volts, and 50 Hz-10 volts stimulation by assessing peak aortic pressure (AoP), left ventricular pressure (LVP), maximum LV +dP/dt, stroke volume (SV), stroke work (SW), stroke power (SP), and aortic flow. LDM assisted beats were compared with nonstimulated beats. LDM stimulation caused significant increases in pressure and flow in the vascular delay group. At 20 Hz-4 volts, absolute increases were LVP (10.2 +/- 0.6) mm Hg, AoP (9.8 +/- 1.7) mm Hg, SV (1.8 +/- 0.4) ml, SW (5.3 +/- 1.0) gm x m, SP (40.8 +/- 12.7) gm x m/sec, max LV dP/dt (104.8 +/- 53.2) mm Hg/sec, and peak aortic flow (0.9 +/- 0.3) L/min. At 33 Hz-4 volts, the absolute increases were LVP (13.6 +/- 1.3) mm Hg, AoP (12.1 +/- 2.4) mm Hg, SV (2.7 +/- 0.7) ml, SW (7.4 +/- 1.4) gm x m, SP (72.7 +/- 16.5) gm x m/sec, max LV dP/dt (294 +/- 19) mm Hg/sec, and peak aortic flow (1.8 +/- 0.5) L/min. At 50 Hz-10 volts, the absolute increases were LVP (17.7 +/- 0.7) mm Hg, AoP (21.1 +/- 1.9) mm Hg, SV (6.0 +/- 1.1) ml, SW (14.6 +/- 2.2) gm.m, SP (128.2 +/- 15.3) gm x m/sec, max LV dP/dt (352 +/- 62) mm Hg/sec, and peak aortic flow (3.3 +/- 0.4) l/min (p < 0.05). The percentage increases were significantly larger in the vascular delay group compared with controls at 50 Hz-10 volts LDM stimulation. By using a two-stage vascular delay procedure, LDM stimulation can provide meaningful cardiac assistance during training periods. Furthermore, brief periods of maximal potential benefit (demand cardiomyoplasty) can be achieved during the training period.

Background: The goal of this study was to obtain physiologically significant increases in peak left ventricular (LV) systolic pressure and stroke volume with latissimus dorsi muscle (LDM) stimulation in cardiomyoplasty (CMP). We hypothesized that preserving LDM integrity by vascular delay and intermittent stimulation would significantly increase LDM cardiac assistance., Methods: In 4 control dogs and 12 dogs that had undergone a vascular delay (VD) procedure, LV dysfunction was induced by intracoronary microsphere injections. Cardiomyoplasty surgery was performed 14 days later, followed by progressive LDM conditioning. In the control dogs and in 6 of the VD dogs, the LDM was stimulated 24 hours per day (VD plus constant stimulation [CS]). In the other 6 VD dogs, LDMs were stimulated on a daily schedule of 10 hours on and 14 hours off (VD plus interrupted stimulation [IS]). Latissimus dorsi muscle stimulated beats were compared with nonstimulated beats 9 weeks later., Results: In the control dogs, LDM stimulation had minimal effects. In VD + CS and VD + IS, LDM stimulation increased peak LV pressure, stroke volume, stroke work, and stroke power (p < 0.05). However, these changes were greater in the VD + IS group, in which LDM stimulation increased peak aortic pressure by 17.6 +/- 1.7 mm Hg, peak LV pressure by 19.7 +/- 1.1 mm Hg, peak positive LV dp/dt by 398 +/- 144 mm Hg per second, stroke volume by 5.1 +/- 0.7 mL, stroke work by 10.9 +/- 0.9 gm.m, and stroke power by 122.7 +/- 11.6 gm.m per second (p < 0.05 compared with VD + CS). Quantitative morphometric analysis showed minimal LDM degeneration in the VD + IS group (7.5% +/- 1.1%), and VD + CS group (10.5% +/- 4.5%) compared with the control group (29.5% +/- 4.5%, p < 0.05)., Conclusions: VD and IS considerably increased the LV assistance with LDM stimulation. Further studies of this combined approach to CMP should be planned.

Hypothesis: Transmyocardial laser revascularization (TMLR) will not denervate the heart, because it does not destroy all of the afferents. This study was designed to determine if stimulation of cardiac sympathetic and vagal afferents from an area of the left ventricle treated with TMLR could evoke reflex effects, and thus whether TMLR would denervate the heart., Methods: The effect of TMLR on reflexes evoked by chemically stimulating cardiac afferents was examined in 9 dogs. Bradykinin and capsaicin were applied topically or injected into the left anterior descending coronary artery before and after TMLR and after bilateral vagotomy and sympathectomy. Aortic (AoP) and left ventricular pressures (LVP) and electrocardiography were monitored. The first derivatives of LVP (dP/dt) were calculated., Results: Topical bradykinin elicited variable hemodynamic responses. Topical capsaicin evoked pressor responses, increasing mean (+/- SEM) AoP (105+/-9 to 115+/-9 mm Hg; P<.001) and positive dP/dt (+dP/dt) (1032+/-81 to 1159+/-10 mm Hg/s; P<.01) before TMLR. Intracoronary capsaicin evoked a depressor response before TMLR. Pressor responses remained intact after TMLR with increases in mean AoP and +dP/dt (115+/-6 to 128+/-5 mm Hg and 1039+/-98 to 1136+/-100 mm Hg/s, respectively; P<.01). Depressor responses also remained intact after TMLR (91+/-10 vs 101+/-11 mm Hg [P<.02], and 865+/-104 vs 931+/-104 mm Hg/s [P<.05], respectively). Hemodynamic responses were diminished after bilateral vagotomy and abolished after bilateral sympathectomy., Conclusion: Since activation of cardiac afferent nerves and reflex responses remained intact after TMLR, but changed after vagotomy or sympathectomy, TMLR does not denervate the heart sufficiently to be the cause of improved angina after TMLR.

Objective: Dynamic aortomyoplasty using Latissimus Dorsi muscle (LDM) has been shown to improve myocardial function. However, systematic examination of the effects of stimulation parameters on aortic wrap function has not been done. Thus, the present study measures the direct effect of stimulation voltage, pulse train duration, frequency of the pulses, and the duration of the stimulation delay from R wave on the aortic wrap function., Methods: In eight female goats, the left LDM was wrapped around the descending aorta. The muscle was then subjected to electrical stimulation, altering frequency of stimulation pulses (16.6, 20, 25, 33 and 50 Hz), amplitude (2, 4, 6, 8 and 10 V), and number of pulses (2, 4, 6, 8 and 10 pulses) in a train stimulation. Left ventricular, aortic pressure, and pressure generated by LDM on aorta (wrap pressure) was measured. The changes in hemodynamic parameters mentioned above were calculated and compared for different stimulation parameters during unassisted and assisted cardiac cycles., Results: Aortomyoplasty counterpulsation using LDM provided significant improvement in wrap pressure (78 mmHg +/- 2), aortic diastolic pressure, and changes in aortic diastolic pressure from 2 to 4 V (P < 0.05). Further increase in amplitude did not make any significant improvements of the above mentioned parameters. Significant augmentation of wrap pressure (82 mmHg +/- 2), aortic diastolic pressure (79 mmHg +/- 3) and changes in aortic diastolic pressure (12 mmHg +/- 1) occurred at 6 pulses (P < 0.05). Other changes in number of pulses did not show any significant improvements. Significant improvement of wrap pressure (80 mmHg +/- 2), aortic diastolic pressure (73 mmHg +/- 3) and changes in aortic diastolic pressure (12 mmHg +/- 1) was observed with a frequency of 33 Hz. To examine a wide range of delays from the onset of the QRS complex to LDM stimulation, stimulation was delivered randomly. The exact delay was determined from the ECG signal and superimposed LDM stimulation pulses., Conclusions: In this study we present a new measurement, wrap pressure. We also present that in aortomyoplasty using LDM, the most significant improvement in wrap pressure, aortic diastolic pressure and changes in aortic diastolic pressure occurs when the stimulation consists of an amplitude of 4 V, a frequency of 33 Hz and a train stimulation of 6 pulses.

A common concern in cardiomyoplasty is whether latissimus dorsi muscle (LDM) stimulation impairs diastolic function. This study determined the time course of left ventricular (LV) contraction and relaxation and their relationship to the diastolic function. Ten mongrel dogs underwent vascular delay of the left latissimus dorsi muscle 2 weeks before cardiomyoplasty. Fourteen to 18 days later, the effects of LDM stimulation were evaluated. Our study demonstrated that LDM stimulation significantly increased peak LV systolic pressure (131.3 +/- 7.5 to 152.0 +/- 7.5* mm Hg), +dP/dt (1585 +/- 151 to 2088 +/- 176 x mm Hg/s), stroke volume (10.8 +/- 1.5 to 13.8 +/- 1.9* ml), stroke work (17.2 +/- 2.7 to 25.6 +/- 3.8* gm x m), and peak aortic flow (4751 +/- 698 to 6712 +/- 926* ml/min), and significantly decreased the pre-ejection time (113.9 +/- 12.6 to 92.3 +/- 7.8* ms) and total systolic time (366.0 +/- 26.9 to 333.6 +/- 21.3* ms) (*p < 0.05). As for diastolic function, LDM stimulation decreased -dP/dt (-1462 +/- 116 to -1781 +/-116* mm Hg/s) and tau (64.0 +/- 6.1 to 52.1 +/- 2.9* ms). The diastolic filling time (Tdf) was significantly longer (177.9 +/- 17.6 to 213.7 +/- 18.7* ms) during the beat immediately after LDM stimulation. These changes reflected an overall stronger contraction and faster relaxation. Our results imply that with vascular delay, stimulation of LDM not only assists systolic function but also improves diastolic function in cardiomyoplasty.

Objectives: Dynamic cardiomyoplasty (CMP) as a surgical treatment for chronic heart failure improves functional class status for most patients. However, significant hemodynamic improvement with latissimus dorsi muscle (LDM) stimulation has not been consistent. The current protocols do not allow early LDM stimulation after CMP surgery. We hypothesized that vascular delay of LDM would increase myocardial assistance after CMP and allow early (48-h) LDM stimulation after CMP., Methods: Mongrel dogs (n = 24) were divided in four groups: 1) controls (n = 6), single-stage CMP; 2) Group ES (n = 6), single-stage CMP with early LDM stimulation beginning 48 h, postoperatively; 3) Group VD (n = 6), vascular delay of the LDM followed by CMP without early LDM stimulation, and 4) Group VDES (n = 6), vascular delay of LDM (14-18 days), followed by CMP with early stimulation (48 h postoperatively). Two weeks after CMP, global cardiac dysfunction was induced by injecting microspheres into the left coronary artery. LDM-assisted (S) beats were compared with nonstimulated beats (NS) by measuring aortic pressure (AoP), LV pressure, aortic flow, and by calculating first derivative of LV contraction (+/-dP/dt), stroke volume (SV), and stroke work (SW)., Results: In ES, LDM stimulation had no effect on the hemodynamic parameters. In the other groups, LDM stimulation significantly (p < 0.05) increased AoP, LVP, dP/dt, SV, and SW. However, these increases were much larger in VD and VDES. In VD, LDM stimulation increased peak AoP by 21.5+/-3.8 mm Hg, LVP by 22.1+/-4.1 mm Hg, dP/dt by 512+/-163 mm Hg/sec, SV by 10.4+/-2.3 mL, and SW by 22.1+/-5.4 g/m(-1). Similarly, in VDES, LDM stimulation increased peak AoP by 24.1+/-4.7 mm Hg, LVP by 26.2+/-4.3 mm Hg, dP/dt by 619+/-47 mm Hg/sec, SV by 6.5+/-0.7 mL, and SW by 16.7+/-4.1 g/m(-1)., Conclusions: In dogs with global LV dysfunction, CMP after vascular delay resulted in a significant improvement in hemodynamic function measured 2 weeks after surgery. This improvement was not provided by single-stage CMP with or without early stimulation. Vascular delay of the LDM before surgery may play an important role for early benefit after CMP, shorten the overall muscle training period, as well as increase hemodynamic response to LDM stimulation.

Background: The management of neonates with complex congenital anomalies depends on careful interpretation of arterial blood gas values. Improved interpretation of these oxygen parameters may allow clinicians to avoid unexpected cardiovascular events. This study examined whether systemic oxygen delivery (DO2) can be maximized by the use of indices derived from oxygen saturation measurements in neonates with hypoplastic left heart syndrome., Methods and Results: For the single-ventricle heart with both circulations in parallel, we used a previously developed computer simulation to obtain DO2 as a function of systemic arterial (SaO2) and venous (SvO2) oxygen saturation, arteriovenous oxygen difference (Sa-vO2), or pulmonary-to-systemic flow ratio (Qp/Qs). We also examined the oxygen excess factor, SaO2/Sa-vO2 (Omega). We found that (1) slight increases in SaO2 may be associated with large decreases in DO2. (2) Low values for SvO2 indicate low values for DO2. (3) Curves for Sa-vO2 and Qp/Qs are redundant in the data provided. (Qp/Qs, however, provides these data in more physiologically relevant terms.) (4) High values for Qp/Qs (>4) are associated with low DO2. (5) Estimating Qp/Qs from oxygen saturation measurements may result in errors when pulmonary venous oxygen saturation is not available. (6) Maximizing DO2 is extremely difficult using SaO2, SvO2, and Qp/Qs. (7) A linear relationship exists between Omega and DO2, and this linear relationship is not altered by changes in cardiac output., Conclusions: Patients with low SvO2 values require attention. Ideally, after reducing Qp/Qs to <1.5, Omega might be a better index to guide further therapy and maximize DO2. Interventions that increased Omega would be considered beneficial, whereas interventions that decreased Omega would be considered detrimental.

Objectives: In standard single stage cardiomyoplasty (CMP), the latissimus dorsi muscle (LDM) is not preconditioned prior to surgery. We hypothesized that latissimus dorsi preconditioning by vascular delay or by chronic electrical stimulation would result in an improved LV hemodynamic function early (14 days) after CMP., Methods: Mongrel dogs had preconditioning of the latissimus dorsi by a vascular delay procedure followed by CMP 14-18 days later (group I VD). Dogs in group II underwent 4 weeks of chronic stimulation (CS) of the latissimus dorsi (2 V/30 Hz, six bursts/min) followed by CMP. The latissimus dorsi muscle was fully stimulated from 48 h after cardiomyoplasty in both groups (2 V/30 Hz, three bursts/min). Two weeks after myoplasty, injecting 2.0-3.0 x 10(5) 90 microm latex microspheres in the left main coronary artery induced global cardiac dysfunction. Hemodynamic function was then evaluated for latissimus dorsi muscle assisted (S) beats and non-stimulated beats (NS) in each group by measuring peak systolic aortic pressure (AOP), left ventricular pressure (LVP) and end diastolic pressure (LVEDP), and by calculating maximum and minimum dP/dt., Results: Dogs with vascular delay of the latissimus dorsi showed a marked increase for all hemodynamic indices (AOP: 23.9+/-2.5%, LVP: 23.5+/-2.2%, max dP/dt: 49.4+/-3.3%) for LDM assisted (S) beats compared to non-stimulated beats (P < 0.001). Animals with chronic electrical training did not demonstrate a significant increase in any hemodynamic parameter with LDM stimulation., Conclusion: Preconditioning the LDM may play an important role in providing early cardiac assistance in CMP. Preconditioning the LDM with vascular delay resulted in improving performance of the LDM with consistent increases in LV hemodynamics. This was not observed after preconditioning with chronic electrical stimulation. Vascular delay of the latissimus dorsi can significantly improve muscle performance in CMP and could provide hemodynamic assistance early after surgery.

A univentricle with parallel pulmonary and systemic circulations is inherently inefficient because mixing of pulmonary and systemic venous return occurs. Thus a cavopulmonary anastomosis is used as a staged palliative procedure to reduce volume overload in patients with cyanotic congenital heart disease. On the basis of oxygen uptake and consumption, an equation was derived that related cardiac output, pulmonary venous oxygen saturation, upper body oxygen consumption, and superior-to-inferior vena caval blood flow ratio (QSVC/QIVC) to oxygen delivery. The primary findings were as follows. 1) As QSVC/QIVC increases, total body oxygen delivery and arterial and superior vena caval oxygen saturations increase. 2) As QSVC/QIVC increases, lower body oxygen delivery and inferior vena caval oxygen saturation initially increase, then peak, and then decrease. 3) As the percentage of lower body oxygen consumption increases, oxygen delivery and saturation decrease. 4) A cavopulmonary anastomosis decreases the required cardiac output for a given oxygen delivery. Thus we concluded that a high systemic arterial oxygen saturation after cavopulmonary anastomosis requires a high percentage of upper body oxygen consumption and a high QSVC/QIVC and that the cavopulmonary anastomosis reduces the volume load on the single ventricle.

A versatile, microprocessor-based stimulator for skeletal muscle cardiac assist (SMCA) has been designed, constructed, and used in several studies. The stimulator uses multiple bipolar electrodes to deliver arbitrarily specified electrical stimulus sequences to three nerve branches of the latissimus dorsi muscle. The electrodes are electrically isolated to effect regional stimulation of the muscle. The width, amplitude, and interpulse interval of each pulse in the stimulus sequence are independently variable, and the three channels are independently programmable, allowing a wide variety of stimulus patterns. Battery powered units have been used in studies for up to one year. In this paper, the stimulator and sample applications in SMCA are described.

This article reviews diastolic and systolic ventricular interaction, and clinical pathophysiological conditions involving ventricular interaction. Diastolic ventricular interdependence is present on a moment-to-moment, beat-to-beat basis, and the interactions are large enough to be of physiological and pathophysiological importance. Although always present, ventricular interdependence is most apparent with sudden postural and respiratory changes in ventricular volume. Left ventricular function significantly affects right ventricular systolic function. Experimental studies have shown that about 20% to 40% of the right ventricular systolic pressure and volume outflow result from left ventricular contraction. This dependency of the right ventricle on the left ventricle helps to explain the right ventricular response to volume overload, pressure overload, and myocardial ischemia. The septum and its position are not the sole mechanism for ventricular interdependence. Ventricular interdependence causes overall ventricular deformation, and is probably best explained by the balance of forces at the interventricular sulcus, the material properties, and cardiac dimensions.

Management of pulmonary vascular resistance in neonates with congenital heart disease is important for stabilization before and after surgical interventions. Thus, we determined which combination of positive end-expiratory pressure ventilation and fraction of oxygen in the inspired air increases pulmonary vascular resistance without compromising delivery of oxygen to the tissue. Eight piglets were anesthetized, intubated and ventilated. Pulmonary flow and pulmonary arterial and left atrial pressures were monitored continuously. At all levels of inspired oxygen (1.00, 0.21 and 0.15), ventilation at a pressure of 15 cm of water increased pulmonary vascular resistance. At all levels of positive pressure ventilation, a fraction of 0.15 of inspired oxygen increased pulmonary vascular resistance. The combination of a ventilatory pressure of 15 cm of water and inspired oxygen of 1.00, or ventilatory pressure at 5 cm of water and oxygen delivery of 0.15, produced similar changes in pulmonary vascular resistance (19.1 +/- 2.8 vs. 20.0 +/- 3.8 mmHg/(L/min)) and cardiac output (0.78 +/- 0.07 vs. 0.93 +/- 0.10 L/min) but, the higher level of positive pressure plus 1.00 inspired oxygen gave a significantly higher arterial oxygen saturation (0.99 +/- 0.03 vs. 0.72 +/- 0.19%) and delivery of oxygen to the tissues (13.7 +/- 2.9 vs. 7.4 +/- 1.5 ml O2/min, p < 0.05). Thus, both high positive pressure ventilation and hypoxia increase pulmonary vascular resistance. Only high pressure ventilation plus high concentrations of inspired oxygen, however, increased pulmonary vascular resistance without compromising delivery of oxygen, suggesting that this combination is a superior means of increasing pulmonary vascular resistance.

This article compares conventional indices of contractile function in the right and left ventricles. The low operating pressures and left ventricles. The low operating pressures and complex geometry complicate evaluation of right ventricular function. However, when the characteristics of its vascular load are taken into account, the complex right ventricular chamber has pump properties that are similar to the high pressure left ventricular chamber.

Cardiomyoplasty (CMP) has been considered as a possible treatment for patients with heart failure. Symptomatic improvements occur almost uniformly among survivors with CMP, but changes in left peak ventricular systolic pressure (PVSP) and stroke volume vary in patients. This study examined whether there is variability present shortly after cardiomyoplasty surgery. Cardiomyoplasty was performed in 11 mongrel dogs with normal ventricular function. Nine to twelve days after CMP, left ventricular (LV) function was evaluated by simultaneously measuring LV volume (conductance catheter) and pressure (Millar catheter). The latissimus dorsi muscle (LDM) was stimulated synchronously with ventricular systole in a ratio of 1:4 to 1:7 to avoid muscle fatigue. Data were analyzed on a beat by beat basis. The PVSP, and maximum dP/dt (+dP/dt) increased, but the absolute value of minimum dP/dt (-dP/dt) decreased in stimulated beats in 7 dogs while 4 dogs did not respond. The net changes in stimulated beats versus nonstimulated beats of PVSP were 6.1 +/- 1.8 mm Hg (4.3%), of stroke work was 4.5 +/- 1.9 gm x m (29.5%), of +dP/dt was 185 +/- 47 mm Hg/s (8%), and of -dP/dt was 168 +/- 43 mm Hg/s (7.8%) (p < 0.05) for all these net changes in the responding group while these variations were not significant in the nonresponding group. From the results of our study, active LDM assist improves left ventricular systolic function, occurring in only 7 of 11 experiments. This improvement is inconsistent and varied individually. The integrity of the LDM, tightness of wrapping, and adhesions might contribute to the variability which is present early after surgery and before the LDM is converted into a fatigue resistance muscle.

Background: Right ventricular failure can lead to circulatory collapse while on left ventricular assist device support. By shunting blood from the femoral vein to the left ventricular assist device, cardiac output can be increased, but arterial oxygen saturation will decrease., Methods: To determine the effects on O2 delivery, a model was developed on the basis of O2 uptake in the lungs and whole body O2 consumption. An equation was derived that related cardiac output, pulmonary venous O2 saturation, O2 consumption, and the ratio of shunt-to-systemic blood flow to systemic O2 delivery., Results: When total cardiac output increases, the shunt will increase systemic O2 delivery while decreasing arterial O2 saturation and leaving systemic venous O2 saturation unaltered. When total output does not increase, the shunt will decrease systemic O2 delivery, arterial O2 saturation, and systemic venous O2 saturation., Conclusions: The analysis suggests that measuring systemic venous oxygen saturation may be a useful way to monitor patient safety. A decrease in systemic venous O2 saturation when creating the shunt implies an inadequate increase in cardiac output.

Unlabelled: Surgeons have traditionally relied on ring preparations to predict how arterial bypass conduits will behave in the postoperative circulation., Objective: This study compared pharmacologic [norepinephrine (NE) challenge] and physiologic [arterial preload] responses of gastroepiploic (GEA) and internal thoracic (ITA) arteries in a standard static ring preparation and a dynamic perfusion system., Methods: Six GEAs (1.0-1.5 mm dia.) and six ITAs (1.5-2.0 mm dia.) 11 cm long were harvested from adult pigs and mounted on a computer controlled perfusion system. Inflow pressure was set at 80 mmHg and outflow resistance was adjusted to simulate high (80-90 ml/min) and low (15-20 ml/min) flow demands. NE response (10(-9)-10(-5) M) was measured under low flow conditions and at high flow conditions when distal arterial pressure (load) was reduced. NE response (10(-9)-10(-5) M) was also evaluated in arterial rings (ITA N = 6, GEA N = 6) with tensions adjusted to simulate the loads occurring at low flow (80 mmHg) and high flow (60 mmHg) situations., Results: In the static ring preparation, NE response [ED50] was similar for both GEA and ITA and was not affected by load. The dynamic preparation demonstrated that the GEAs were significantly more responsive to NE than the ITAs [ED50 high flow ITA 6.1 +/- 0.3**, GEA 7.2 +/- 0.3***; *P < 0.05 versus baseline, **P < 0.05 versus low flow values, ***P < 0.05 versus ITA]. Furthermore, in the dynamic preparation, NE response was profoundly affected by reduced load which occurs under high flow conditions [7.18 +/- 0.3 versus 6.1 +/- 0.3 under high flow and 5.8 +/- 0.1 versus no response under low flow conditions]., Conclusion: Static ring preparations do not discern differences between ITA and GEA susceptibility to spasm and fail to detect the effect of load. The dynamic preparation demonstrated significant differences between the GEA and ITA potential to spasm which is consistent with widespread clinical experience. Furthermore a dynamic preparation is highly sensitive to reduced load which occurs under high flow conditions. Although it is more demanding, the dynamic preparation provides superior information to the surgeon in predicting the behavior of arterial bypass grafts.

In cardiomyoplasty, the latissimus dorsi muscle (LDM) is wrapped around the heart ventricles and electrically activated with a constant-frequency train (CFT). This study tested the hypotheses that increased mechanical performance from the LDM could be achieved by activating the muscle with variable-frequency trains (VFTs) of shorter duration or containing fewer stimulus pulses than the CFT now used. The mechanical performance of the canine LDM (n = 7) during shortening contractions was measured while the muscle was stimulated with 5- and 6-pulse CFTs (of duration 132 and 165 ms, respectively) and 5- and 6-pulse VFTs (of duration 104 and 143 ms, respectively) that were designed to take advantage of the catchlike property of skeletal muscle. Measurements were made from fresh and fatigued muscles. For the fresh muscles, the VFTs elicited significantly greater peak power than did the 6-pulse CFT. When the muscles were fatigued, VFT stimulation significantly improved both the peak and mean power produced compared with stimulation by CFTs. These results show that stimulation of the LDM with shorter duration VFTs is potentially useful for application in cardiomyoplasty.

This study examined the effects of cardiomyoplasty with vascular delay on canine normal and depressed left ventricular (LV) function. To improve viability of the latissimus dorsi muscle (LDM), vascular delay was performed 2 weeks before cardiomyoplasty in 10 mongrel dogs. Two weeks after cardiomyoplasty, LV function was evaluated by simultaneously measuring LV and aortic pressure, and aortic flow. The LDM was stimulated at a ratio of 1:4-1:7 synchronously with ventricular systole. Microspheres (90 mu) were sequentially injected into the left coronary artery to depress LV function. Data were acquired and analyzed on a beat to beat basis. Results were as follows: LDM stimulation significantly augmented LV systolic pressure (LVSP) from 138 +/- 2 to 161 +/- 2* mmHg, the peak rate of change of LV pressure (+dP/dt) from 1888 +/- 46 to 2584 +/- 43* mmHg/sec, aortic systolic pressure (AoSP) from 140 +/- 2 to 159 +/- 2* mmHg, stroke volume (SV) from 11.2 +/- 0.3 to 13.3 +/- 0.3* ml, stroke work (SW) from 19 +/- 1 to 26 +/- 1* gm.m, peak aortic flow (P Qa) from 5542 +/- 142 to 7190 +/- 161* ml/min, and decreased -dP/dt from -1683 +/- 31 to -1689 +/- 49* mmHg/sec (* = p < 0.05). Microsphere injections depressed LV function, but did not affect the magnitude of the net changes between stimulated and nonstimulated beats. However, the percent changes significantly increased. Preconditioning of LDM with vascular delay augments cardiac function in LDM assisted beats. This improved performance was present in both normal as well as depressed LV function groups. Thus, investigations of cardiomyoplasty may not necessarily require a model of severe myocardial dysfunction. Vascular delay offers an important preconditioning method of LDM to augment cardiac function in cardiomyoplasty.

Unlabelled: The gastroepiploic artery (GEA) is a highly vasoactive artery gaining wider acceptance as a conduit for coronary artery bypass surgery. A variety of agents are used to dilate the GEA prior to grafting; however, little is known about the duration of their effect in the immediate postoperative period. This study evaluated three calcium channel blockers and papaverine in preventing graft spasm., Methods: Porcine GEA segments (10-12 cm in length) were connected to a computer-controlled perfusion system with a constant in-flow pressure and distal resistance to simulate bypass flow (80-100 ml/min). Norepinephrine (NE; 10(-9) to 10(-5) M) was given in incremental doses at baseline before the vasodilator, immediately after (0 hr), and again at 2 hr after the vasodilator. Changes in flow and ED50 were recorded. Group INT (N = 25) received papaverine (PAP), diltiazem, nifedipine (NFP), or verapamil (VPL) intraluminally, while group EXT (N = 25) received the same dilators externally., Results: All arteries showed dose-dependent vasoconstriction to NE prior to treatment. Immediately after receiving the vasodilator, arteries in both groups (INT and EXT) showed initial protection against NE-induced spasm with the exception of arteries receiving NFD externally. However, at 2 hr, for group INT, only VPL and NFD prevented NE-induced graft spasm (VPL: 40.4 +/- 6.8 ml/min vs 17.9 +/- 3.3 ml/min and NFD: 27.0 +/- 6.5 ml/min vs 13.1 +/- 0.9 ml/min, P < 0.02). In group EXT, after 2 hr, only VPL- and PAP-treated grafts showed resistance to NE-induced vasospasm (VPL: 35.6 +/- 7.3 ml/min vs 15.0 +/- 6.9 ml/min and PAP: 47.4 +/- 15.1 ml/min vs 8.0 +/- 2.0 ml/min, P < 0.001)., Conclusions: Papaverine, a lipophilic vasodilator, when given externally on the perivascular fat of the GEA, prevented graft spasm for up to 2 hr. In contrast, intraluminally applied papaverine did not show graft protection against NE-induced spasm. Nifedipine prevented NE-induced spasm only when given intraluminally. Verapamil proved to be the most potent and versatile vasodilator with effective graft protection of up to 2 hr whether applied externally or internally and was the preferred agent for protecting against GEA spasm.

Cardiomyoplasty is a new surgical treatment for heart failure in which skeletal muscle assists the heart. However, for the first 2 weeks postoperatively, the latissimus dorsi muscle (LDM) remains unstimulated, and during the next 2 weeks, the LDM is stimulated with only one pulse every other heart beat. Thus, for the initial 4 postoperative weeks, minimal systolic assistance is provided. The present study determined if the LDM is capable of providing early assistance. Cardiomyoplasty surgery involves severing the perforating intercostal arteries to the LDM, detaching the LDM from its distal insertion, and wrapping it around the heart. At each of these steps, we measured LDM force development, shortening, and blood flow in six dogs. At control, LDM shortening, work, and power decreased during a 2 min fatigue test: fatigue indices (final/ initial value) for shortening, work, and power were 47.6 +/- 6.9%, 47.5 +/- 7.1%, and 46.9 +/- 6.6%, respectively. Blood flow increased in the proximal (P), mid (M), and distal (D) LDM during the fatigue test. After partial vascular isolation, initial shortening, work, and power decreased by 29.4%, 32.5%, and 31.7% from their respective control values. During the fatigue test, fatigue indices for shortening, work, and power were 24.7 +/- 3.3%, 19.5 +/- 4.6%, and 22.2 +/- 4.7%, respectively, all significantly (p < 0.05) less than control values. Resting blood flows were unaltered. During exercise, flow to the P increased, whereas flow did not increase in M (p < 0.05). Loss of LDM function was most apparent after mobilizing and reattaching the muscle. Initial shortening, work, and power significantly decreased (p < 0.05) by 74.1%, 76.8%, and 74.4%, from their respective control values. During a fatigue test, final values for shortening, work, and power were all near zero. Resting blood flow decreased in the M and D (p < 0.05) and, during exercise, blood flow increased only in P. Thus, LDM function was severely depressed during the isolation procedure. This functional loss is associated with inadequate blood flow responses. Therefore, preconditioning and/or revascularization is needed if the LDM is to provide cardiac assistance shortly after cardiomyoplasty surgery.

Background: This study examines whether the measurement of internal thoracic artery (ITA) graft flow can determine the adequacy of the ITA-left anterior descending coronary artery (LAD) anastomosis., Methods: To study a wide range of clinical problems, we used a computer simulation of the cardiovascular system. The model included a time-varying elastance model of the heart, a systemic circulation represented by a multielement nonlinear model of the aorta and its major branches, a nonlinear model of the LAD circulation, and a model of the ITA bypass graft., Results: With a mild LAD stenosis, ITA graft flow was low and flow reversal occurred. As the percent stenosis increased, ITA flow and the percentage of ITA-to-total LAD flow increased. The ITA graft helped to maintain resting LAD blood flow. A partial obstruction (40%) at the ITA-LAD anastomosis reduced ITA graft flow at similar levels of LAD stenosis. However, overlap in flow values comparing a normal with a partially obstructed anastomosis occurred., Conclusions: Flow patterns in the ITA are highly dependent on the degree of stenosis of the LAD as well as the integrity of the anastomosis. The predictive power of ITA flow measurement increases with severe stenosis or total occlusion of the proximal LAD and with high coronary blood flow demands.

Minimally invasive coronary artery bypass grafting (MICABG) may be achieved by arterial grafting on the beating heart, without cardiopulmonary bypass, and by operations via limited access. The Second Utrecht MICABG Workshop held October 4-5, 1996, focused on beating-heart coronary immobilization, limited-access thoracoscopic and direct-vision mobilization of the internal mammary artery, limited-access left anterior descending coronary artery grafting, and, finally, facilitated distal anastomosis techniques. It has yielded 33 reports in this supplement. The combined, cumulative experience of a number of participants exceeded 3,000 beating-heart cases, including more than 1,000 with arterial grafting through limited access. The average number of anastomoses per patient ranged from 1.0 to 2.0. Therapeutic strategies are evolving, and dedicated instrumentation is being developed. Randomized clinical trials with angiographic follow-up are required to establish that the reduction in invasiveness of coronary bypass grafting is not achieved at the expense of suboptimal quality of the arterial graft and the distal anastomosis.

Although progress has been made in treating hypoplastic left heart syndrome, improvements in perioperative care may further decrease mortality. We present a case in which continuous monitoring of systemic venous oxygen saturation allowed stabilization and successful management of a critically ill infant. Systemic venous oxygen saturation may provide a more accurate representation of a child's clinical status, allowing more rapid intervention and better outcomes.