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Objectives: The purpose of the study is to identify the predictors of clinical outcome (mortality and survival without repeat septal reduction procedures) of alcohol septal ablation for the treatment of patients with hypertrophic obstructive cardiomyopathy. Background: Alcohol septal ablation is used for treatment of medically refractory hypertrophic obstructive cardiomyopathy patients with severe outflow tract obstruction. The existing literature is limited to single-center results, and predictors of clinical outcome after ablation have not been determined. Registry results can add important data. Methods: Hypertrophic obstructive cardiomyopathy patients (N = 874) who underwent alcohol septal ablation were enrolled. The majority (64%) had severe obstruction at rest, and the remaining had provocable obstruction. Before ablation, patients had severe dyspnea (New York Heart Association [NYHA] functional class III or IV: 78%) and/or severe angina (Canadian Cardiovascular Society angina class III or IV: 43%). Results: Significant improvement (p < 0.01) occurred after ablation (~5% in NYHA functional classes III and IV, and 8 patients in Canadian Cardiovascular Society angina class III). There were 81 deaths, and survival estimates at 1, 5, and 9 years were 97%, 86%, and 74%, respectively. Left anterior descending artery dissections occurred in 8 patients and arrhythmias in 133 patients. A lower ejection fraction at baseline, a smaller number of septal arteries injected with ethanol, a larger number of ablation procedures per patient, a higher septal thickness post-ablation, and the use beta-blockers post-ablation predicted mortality. Conclusions: Variables that predict mortality after ablation, include baseline ejection fraction and NYHA functional class, the number of septal arteries injected with ethanol, post-ablation septal thickness, beta-blocker use, and the number of ablation procedures. [ABSTRACT FROM AUTHOR]

Background: Defibrillation threshold (DFT) testing is performed in part to ensure an adequate safety margin for the termination of spontaneous ventricular arrhythmias. Left ventricular mass is a predictor of high DFTs, so patients with hypertrophic cardiomyopathy (HCM) are often considered to be at risk for increased defibrillation energy requirements. However, there are little prospective data addressing this issue., Objective: To assess DFTs in patients with HCM and evaluate the clinical predictors of elevated DFTs., Methods: Eighty-nine consecutive patients with HCM and 600 control patients with ischemic or nonischemic cardiomyopathy underwent a uniform modified step-down DFT testing protocol. DFT was compared between the control and HCM populations. Predictors of elevated DFT were evaluated in the HCM group., Results: There was no difference in DFT between HCM and control groups (10.4 ± 5.8 J vs 11.2 ± 5.6 J, respectively). Among patients with HCM, clinical parameters such as left ventricular ejection fraction, interventricular septal thickness, left ventricular mass, and QRS duration were not predictive of an elevated DFT. Only 3 patients (3.4%) with HCM had a DFT >20 J., Conclusion: Patients with HCM do not have elevated DFTs as compared to more typical populations undergoing implantable cardioverter-defibrillator implant; high-energy devices or complex lead systems are not needed routinely in this population., (© 2010 Wiley Periodicals, Inc.)

Objectives: The purpose of this study was to examine the effects of alcohol septal ablation (ASA) on ventricular arrhythmias among patients with obstructive hypertrophic cardiomyopathy (HCM), as measured by appropriate implantable cardioverter-defibrillator (ICD) discharges., Background: Alcohol septal ablation is an effective therapy for patients with symptomatic HCM. However, concern has been raised that ASA may be proarrhythmic secondary to the iatrogenic scar created during the procedure. The impact of ASA on ventricular arrhythmias has not been well described., Methods: This prospective study included 123 consecutive patients with obstructive HCM who underwent ASA and had an ICD implanted for primary prevention of sudden cardiac death (SCD). The ICDs were implanted based on commonly accepted risk factors for SCD in the HCM population. Data from ICD interrogations during routine follow-up were collected., Results: Nine appropriate ICD shocks were recorded over a mean follow-up of 2.9 years in the cohort, which had a mean of 1.5 +/- 0.9 risk factors for SCD. Using Kaplan-Meier survival analysis, the estimated annual event rate was 2.8% over 3-year follow-up. There were no significant differences in the incidence of risk factors between patients who did and did not receive appropriate shocks., Conclusions: The annual rate of appropriate ICD discharges after ASA is low and less than that reported previously for primary prevention of SCD in HCM. This suggests that ASA is not proarrhythmic. Traditional SCD risk factors did not predict ICD shocks in this cohort.

Objectives: This study sought to determine the long-term outcome of alcohol septal ablation (ASA)., Background: There are inadequate data on the long-term outcome of ASA for symptomatic hypertrophic obstructive cardiomyopathy (HOCM)., Methods: Six hundred and twenty-nine patients were enrolled consecutively (1996 to 2007) and 98.4% (n = 619) underwent ASA with 92% follow-up in 2007. Evaluation included deaths, procedural complications, pacemaker requirement, repeat ASA, and myectomy/valve surgery. Follow-up parameters included angina (Canadian Cardiovascular Society score), dyspnea (New York Heart Association functional class), exercise time, and echocardiographic indices (septal thickness, ejection fraction, resting and provoked gradients)., Results: Ethanol (2.6 +/- 1.0 ml) was injected into 1.3 +/- 0.5 septal arteries, inducing a septal infarct. Complications included death 1% (n = 6), permanent pacemaker requirement 8.2% (n = 52), coronary dissection 1.3% (n = 8), and worsening mitral regurgitation 0.3% (n = 2). The mean follow-up was 4.6 +/- 2.5 years (range: 3 months to 10.2 years). During follow-up, New York Heart Association functional class decreased from 2.8 +/- 0.6 to 1.2 +/- 0.5 (p < 0.001); Canadian Cardiovascular Society angina score decreased from 2.1 +/- 0.9 to 1.0 +/- 0 (p < 0.001); and exercise time increased from 4.8 +/- 3.3 to 8.2 +/- 1.0 (p < 0.001) min. The resting and provoked left ventricular outflow tract gradients decreased progressively (p < 0.001) and remained low during follow-up. The septal thickness decreased from 2.1 +/- 0.5 cm to 1.0 +/- 0.1 cm (p < 0.001) and the ejection fraction decreased from 68 +/- 9% to 62 +/- 3% (p < 0.001). The survival estimates at 1, 5, and 8 years were 97%, 92%, and 89%, respectively., Conclusions: The initial benefits of ASA were maintained during follow-up.

Patients with obstructive hypertrophic cardiomyopathy are presumed to have poor quality of life (QOL) and distress related to their cardiac symptoms and functional limitations. Alcohol septal ablation (ASA) is designed to improve heart function and reduce cardiac symptoms. The purpose of this study was to examine psychosocial factors and QOL in patients with obstructive hypertrophic cardiomyopathy before and 3 months after ASA. Twenty-two adult participants (mean age 57 +/- 14 years, 59% women, 100% Caucasian, 67% married) were recruited during their initial evaluations or scheduled index hospitalizations for ASA. Psychosocial and medical measures were collected before and 3 months after ASA. The results indicated that before ASA, 57% of patients reported clinically relevant levels of depression (Center for Epidemiologic Studies Depression Scale score >16), symptoms of anxiety, and reduced QOL. Repeated-measures analyses of variance revealed that ASA is an effective procedure in reducing disease severity (i.e., peak left ventricular outflow tract gradient, septal thickness, posterior wall thickness) (p = 0.001 to 0.05), depression (p = 0.005), and anxiety (p = 0.029) and improving cardiac-specific QOL (p < 0.001) and generic physical health-related QOL (p = 0.009). Changes in satisfaction with life, optimism, and generic mental health-related QOL were not significant (p = 0.143 to 0.899). In conclusion, significant psychological distress and compromised well-being were present in this sample of pre-ASA patients with obstructive hypertrophic cardiomyopathy. After ASA, significant reductions in psychological distress and improvements in well-being and echocardiographic parameters indicating disease severity were demonstrated. These results suggest that patients perceived broad health benefits from ASA in short-term follow-up.

Objectives: We sought to determine the outcome of myectomy after unsuccessful alcohol ablation., Background: Alcohol septal ablation results in symptomatic improvement and a reduction in dynamic obstruction in most hypertrophic obstructive cardiomyopathy patients. However, a few patients remain with severe symptoms and obstruction and need surgery. The outcome of these cases is not well known., Methods: The medical records of 375 patients who underwent alcohol ablation at our institution were reviewed. Twenty patients (5.3%, mean age 53 +/- 18 years, 17 women) subsequently needed surgical myectomy. The New York Heart Association (NYHA) functional class, angina class, exercise duration, left ventricular outflow tract (LVOT) gradient, ejection fraction, and septal thickness were tabulated. The anatomy and distribution of the septal perforator arteries were examined., Results: After ablation, NYHA functional class (3 to 2.5; p < 0.05) and LVOT gradient (93 +/- 23 mm Hg to 71 +/- 26 mm Hg; p < 0.05) were slightly improved, without a change in exercise duration (171 +/- 124 s to 168 +/- 148 s; p > 0.5). Myectomy was performed at 19 +/- 15 months after ablation. There was no operative mortality, but permanent pacing was needed in 2 patients after surgery, and 3 other cases needed pacing before, or as a complication of, alcohol ablation. A significant improvement was noted, with the NYHA functional class decreasing to 1, exercise duration increasing to 423 +/- 171 s, and LVOT gradient decreasing to 6 +/- 11 mm Hg (all p < 0.05 versus post-alcohol ablation)., Conclusions: Myectomy can be successfully performed after failed alcohol ablation, but with a higher incidence of heart block than in cases where only surgery is performed. Otherwise, alcohol ablation does not appear to adversely affect surgical outcome.

A 49-year-old man with a history of hypertrophic obstructive cardiomyopathy (HOCM) presented in sustained monomorphic ventricular tachycardia (SMVT) 8 days post-alcohol septal ablation. A dual chamber implantable cardioverter defibrillator ICD was implanted and the patient experienced another episode of VT 3 weeks later, which was terminated by an ICD shock. This case demonstrates probable scar-induced reentrant VT post-alcohol septal ablation, a likely rare but hypothesized complication of this procedure.

Seven patients with obstructive hypertrophic cardiomyopathy and single-vessel coronary artery disease underwent percutaneous revascularization of the coronary lesion in addition to alcohol septal ablation therapy for dynamic outflow tract obstruction. One year later, there was a significant reduction of dynamic left ventricular outflow tract obstruction and no clinical evidence of restenosis.

Background: There is a paucity of data on the long-term outcome of alcohol septal ablation (ASA) for symptomatic hypertrophic obstructive cardiomyopathy (HOCM)., Hypothesis: The study was undertaken to evaluate the longer-term outcome of ASA therapy for symptomatic HOCM., Methods: In all, 137 patients were enrolled consecutively (1996-1999) and 130 (95%) (74 men, 56 women, aged 51 +/- 17 years) underwent ASA and had serial prospective follow-up for up to 5 years (mean follow-up 3.6 +/- 1.4 years). Evaluation included angina (Canadian Cardiovascular Society [CCS] score), dyspnea (New York Heart Association [NYHA] class), duration of exercise on treadmill, and echocardiographic indices., Results: Ethanol (3.5 +/- 1.5 cc), injected into 1.5 +/- 0.6 arteries, induced a mean peak plasma creatine kinase (CK) of 1676 +/- 944 units. Complications of procedures included death 1.5% (2/130), heart block requiring permanent pacemaker 13% (17/130), and coronary dissection 4.4% (6/130). Baseline versus last follow-up visit: NYHA class decreased from 3.0 +/- 0.4 to 1.2 +/- 0.6 (p < 0.01); CCS angina score from 2.0 +/- 0.8 to 0.08 +/- 0.4 (p < 0.01); and duration of exercise increased from 322 +/- 207 to 443 +/- 200 s (p < 0.01). Resting left ventricular outflow tract gradient at baseline versus last follow-up visit showed a decrease from 74 +/- 30 to 4 +/- 13 (p < 0.01), and the dobutamine-provoked gradient of 88 +/- 29 decreased to 21 +/- 21 (p < 0.01) mmHg. All-cause mortality over the duration of follow-up was 7.7% (10) giving an annual rate of 2.1%, and cardiac mortality was 2.3% (3) reflecting an annual rate of 0.6%., Conclusions: Alcohol septal ablation decreased symptoms and improved exercise performance, indicating that it is an effective procedure for symptomatic HOCM.

Background: Alcohol septal ablation (ASA) therapy results in clinical and hemodynamic improvement in patients with hypertrophic obstructive cardiomyopathy. However, a subset remains symptomatic afterward, requiring additional procedures. We sought to examine the determinants of an unsatisfactory outcome, defined as unchanged symptoms with <50% reduction of baseline left ventricular outflow tract (LVOT) gradient., Methods and Results: Of 173 consecutive hypertrophic obstructive cardiomyopathy patients who underwent ASA, 39 had an unsatisfactory outcome after the first procedure. Patients with an unsatisfactory outcome had a higher baseline LVOT gradient, fewer septal arteries injected with ethanol, lower peak creatine kinase (CK), smaller septal area opacified by contrast echocardiography, and higher residual gradient in the catheterization laboratory after ASA (all P<0.05). Symptoms, septal thickness, mitral regurgitation severity, and ventricular function were not determinants of outcome. On multiple logistic regression, LVOT gradient reduction after ASA in the catheterization laboratory to > or =25 mm Hg (OR, 5.5; P=0.01) and peak CK <1300 U/L (OR, 2.5; P=0.04) were the independent predictors of an unsatisfactory outcome., Conclusions: The residual LVOT gradient in the catheterization laboratory and peak CK leak after ASA are the independent predictors of ASA outcome.

Treatment of obstructive hypertrophic cardiomyopathy remains challenging. Medical therapy, surgical therapy, and pacemaker therapy have been shown to be beneficial in some patients over the years. Alcohol septal ablation is a catheter-based intervention that causes a controlled infarct in the septum leading to a decrease in the left ventricular outflow tract obstruction. Along with the impressive reductions in left ventricular outflow tract gradient, there is subjective and objective improvement in symptoms. Development of complete heart block requiring a permanent pacemaker after alcohol septal ablation remains a frequent complication, but has decreased in some recent studies. Alcohol septal ablation has been shown to improve diastolic function, decrease mitral regurgitation, decrease left ventricular hypertrophy and mass, as well as cause changes at the cellular and molecular level that improve myocardial function. Comparison of alcohol septal ablation to surgical myectomy has shown favorable results. Long-term follow-up of alcohol septal ablation has shown sustained results out to several years.

Objectives: The purpose of this paper is to examine the incidence and determinants of permanent complete heart block (CHB) after nonsurgical septal reduction therapy (NSRT), and to evaluate the clinical impact of permanent pacemaker (PPM) placement., Background: Nonsurgical septal reduction therapy with ethanol improves the clinical and hemodynamic parameters in patients with symptomatic hypertrophic obstructive cardiomyopathy. Complete heart block is a common complication after NSRT., Methods: The database of 261 consecutive patients who underwent NSRT at Baylor College of Medicine was reviewed. Clinical variables that were considered as possible determinants for CHB after NSRT were: age, gender, New York Heart Association (NYHA) functional class, left ventricular outflow tract (LVOT) gradient at rest or with provocation, septal thickness, and baseline exercise duration. For electrocardiographic (ECG) variables, the presence of first-degree atrioventricular (AV) block, bifascicular block, left bundle branch block, atrial fibrillation, and left ventricular hypertrophy were analyzed. In addition, the volume of ethanol injected, the method of administration of ethanol (i.e., bolus vs. slow injection [over 30 to 60 s]), number of septal arteries occluded, use of myocardial echocardiography, and infarct size as determined by peak creatine kinase level., Results: Of 261 consecutive patients, 37 had PPM or automatic implantable cardiac defibrillator placed before NSRT. Of the remaining 224 patients, 31 (14%) developed CHB after the procedure. Multivariate logistic regression analysis showed that female gender (odds ratio [OR] 4.3; P = 0.02), bolus injection of ethanol (OR 51; P = 0.004), injecting more than one septal artery (OR 4.6; P = 0.016), the presence of left bundle branch block (OR 39; P = 0.002), and first-degree AV block (OR 14; P = 0.001) on the baseline ECG are independent predictors of CHB after NSRT. Patients requiring PPM placement had a similar improvement in their NYHA functional class, septal thickness reduction, LVOT gradient reduction, and improvement of exercise capacity when compared with patients who did not require pacing., Conclusions: Multiple demographic, electrocardiographic, and technical factors seem to increase the risk of CHB after NSRT. Patients with CHB after NSRT derive similar clinical and hemodynamic benefit to patients who did not require permanent pacing.

Background: Nonsurgical septal reduction therapy (NSRT) has been shown to improve left ventricular outflow tract (LVOT) gradients, decrease septal thickness, and improve symptoms in patients with hypertrophic obstructive cardiomyopathy (HOCM). The major complication of this procedure has been the development of complete heart block (CHB) requiring permanent pacemaker implantation, which has been reported in up to 33% of patients in early studies. Since this procedure was first reported, there have been refinements in the technique such as the use of echocardiographic contrast material to localize the site of infarction, slower injection of alcohol, as well as improvement in balloon technology., Hypothesis: We sought to determine the results of NSRT using echocardiographic contrast localization, slow injection of alcohol, and short balloon length. We theorized that the incidence CHB would be lower than earlier reported results using these refined techniques., Methods: We performed 50 NSRT procedures on 46 patients using echocardiographic contrast localization, slow alcohol injection, and currently available balloons. Patients had an echocardiogram before, immediately after NSRT, and at 3 months, and a treadmill test before and at 3 months after NSRT. In the hospital, patients were observed for the development of CHB or other complications, and infarct size was determined by serial creatine kinase (CK) measurements., Results: There was a decrease in the LVOT gradient from 84.2 (+/- 30.8) mmHg at baseline, to 18.5 (+/- 14.8) mmHg immediately after NSRT (p < 0.001). At 3 months, the gradient was not statistically different at 22.7 (+/- 22.2) mmHg 0.27). The septal thickness decreased from 2.21 (+/- 0.66) cm at baseline, to 1.67 (+/- 0.51) cm at 3 months (p < 0.001). New York Heart Association symptom class improved from 3.2 (+/- 0.4) at baseline, to 1.1 (+/- 0.6) at 3 months (p < 0.001). Mean treadmill time in 30 patients was 235 (+/- 142) s at baseline, to 367 (+/- 159) s at 3 months (p < 0.001). Of the 50 procedures, 45 were performed in patients without a previously placed permanent pacemaker or intracardiac cardioverter defibrillator, only 3 (6.7%) of the 45 developed complete heart blocks required permanent pacing. While only three patients in the series had a preexisting left bundle-branch block (LBBB), two of the three patients who required a permanent pacemaker had an LBBB before the prcoedure., Conclusion: Using contrast echocardiographic localization, slow injection of alcohol, and shorter balloon catheters, there continues to be excellent improvement in LVOT gradients, septal thickness, and symptoms, with a reduced incidence of CHB requiring permanent pacemaker implantation. Left bundle-branch block appears to be a strong predictor for the development of CHB after NSRT.

Objectives: This study examined plasma levels of certain matrix metalloproteinase (MMP) and tissue inhibitor of matrix metalloproteinase (TIMP) species before and after alcohol-induced myocardial infarction (MI) in patients with hypertrophic obstructive cardiomyopathy (HOCM)., Background: Matrix metalloproteinases contribute to tissue remodeling, and endogenous control of MMP activity is achieved by the concordant release and binding of TIMPs. Animal models of MI have demonstrated a role for MMP activation in myocardial remodeling. However, the temporal relationship of MMP and TIMP release following a controlled myocardial injury in humans remains unknown., Methods: Plasma levels for the gelatinases MMP-2 and MMP-9, and for the collagenases MMP-8 and MMP-13, as well as TIMP-1 profiles were examined (by enzyme-linked immunosorbent assay) at baseline and serially up to 60 h following alcohol injection into the septal perforator artery in order to induce an MI in 51 patients with HOCM (age 55 +/- 2 years)., Results: Plasma creatine kinase (MB isoform), indicating myocardial injury, increased 2,150% 18 h post-MI (p < 0.05). Plasma MMP-9 increased by over 400% and MMP-8 by over 100% from baseline values by 12 h post-MI (p < 0.05 vs. baseline). A similar temporal profile was not observed for MMP-2 and MMP-13. In addition, a concomitant increase in plasma TIMP-1 levels did not occur post-MI. As a result, MMP/TIMP stoichiometry (MMP-9/TIMP-1 ratio) increased significantly post-MI, suggestive of reduced TIMP-1 mediated MMP-9 inhibition, which would potentially enhance extracellular myocardial remodeling., Conclusions: These unique results demonstrated that induction of a controlled myocardial injury in humans, specifically through alcohol-induced MI, caused species- and time-dependent perturbations of MMP/TIMP stoichiometry that would facilitate myocardial remodeling in the early post-MI setting.

Background: Transcoronary ethanol septal ablation (TESA) is a novel treatment for obstructive hypertrophic cardiomyopathy (HOCM). Our objective was to evaluate the use of gated single photon emission computed tomography (SPECT) in patients with HOCM and the effects of TESA on myocardial perfusion., Methods and Results: We performed gated SPECT and Doppler echocardiography before and 6 weeks after TESA in 30 patients with severe HOCM. The lung-to-heart and septal-to-lateral wall count-activity ratios were calculated. Before ablation, SPECT showed perfusion abnormalities in only 6 patients. Asymmetric septal hypertrophy was noted in 21 patients (70%). In patients with a lung-to-heart ratio greater than 0.50 before ablation, the ratio decreased from 0.56 +/- 0.04 to 0.45 +/- 0.08 after ablation (P <.01). The septal-to-lateral wall ratio also decreased significantly after ablation. Mean Doppler pressure gradient across the left ventricular outflow tract decreased from 52 +/- 39 mm Hg to 13 +/- 13 mm Hg (P <.01) immediately after ablation and to 10 +/- 21 mm Hg 6 weeks later (P <.01). There were no significant changes in left ventricular ejection fraction by gated SPECT after the procedure. SPECT studies done after ablation showed fixed septal defects in 29 of 30 patients (96.7%). The defects involved the basal and mid septum in 100% and 38% of patients, respectively, and ranged in size from 2% to 30% of the left ventricle (mean, 8.8% +/- 7.0%)., Conclusions: TESA is an effective technique for relieving left ventricular outflow obstruction in patients with HOCM. Myocardial gated SPECT can identify the presence and location of infarction after TESA.

Assessing the effectiveness of newer treatments for rare diseases can be challenging because of the small number of patients treated at individual centers. We enrolled patients undergoing percutaneous transluminal septal myocardial ablation (PTSMA) for hypertrophic obstructive cardiomyopathy (HOCM) at five international centers (1 Japan, 2 United Kingdom, and 2 United States). Our study group developed standard data definitions regarding clinical symptom severity, previous HOCM treatment, procedure status, and outcome, and entered patient data directly into a shared, web-based registry system. In the first 10 months of 1998, 51 patients were enrolled in our registry, with 47 ultimately receiving the PTSMA procedure. Although HOCM is consider a single disease, there were significant differences among centers in patient characteristics (age, gender, and family history of HOCM), symptom severity, diagnostic techniques (measurements taken after provocation), and treatment (amount of alcohol used, timing of injection, and number of branches attempted).

Background: Patients with hypertrophic obstructive cardiomyopathy have left ventricular (LV) diastolic dysfunction due, in part, to temporal heterogeneity in regional function. The acute effect of the relief of LV outflow tract obstruction is unknown. Therefore, we investigated the effects of nonsurgical septal reduction therapy (NSRT) on regional function., Methods and Results: Twenty-two patients (aged 56+/-17 years) underwent echocardiographic examination, including tissue Doppler imaging, simultaneously with left heart catheterization before and after NSRT. LV regional function was assessed in 12 segments from which myocardial strain was obtained. Asynchrony was calculated as the coefficient of variation of the time interval from the QRS complex to the onset of expansion and to early diastolic strain. After NSRT, a significant reduction in LV outflow tract obstruction (from 57+/-5 to 12+/-3 mm Hg) occurred with shortening of the time constant of LV relaxation (71+/-4 to 61+/-3 ms; both P<0.05). The coefficient of variation of the time interval to onset of regional expansion decreased significantly and related well to the changes in the time constant of LV relaxation (r=0.81, P<0.01)., Conclusions: NSRT has a favorable effect on LV regional asynchrony, which accounts for the acute changes in LV relaxation.

Hypertrophic obstructive cardiomyopathy is a complex and challenging disease. Medical therapy, surgical therapy, and pacing therapy have been used with some success over the years. Nonsurgical septal reduction therapy, also called alcohol septal ablation, has been used recently as a percutaneous catheter-based intervention to improve left ventricular outflow tract obstruction and thereby improve symptoms. The reported results of this procedure have shown impressive reductions in gradient and improvement in symptoms at relatively low risk. The most common complication of the procedure, development of complete heart block requiring a permanent pacemaker, has improved in recent studies with refinements of the procedural technique. Nonsurgical septal reduction therapy has been shown to improve diastolic function, decrease left ventricular hypertrophy and mass, and cause changes at the cellular and molecular level that improve myocardial function. Reported results at 1 year follow-up continue to show benefit, and long-term studies are ongoing.

Background: Nonsurgical septal reduction therapy (NSRT) is a novel therapeutic strategy for patients with hypertrophic obstructive cardiomyopathy (HOCM). Although the clinical benefits of this technique appear to be clear, the structural and functional changes that lead to improvements in cardiac function are not completely defined. In these studies, we sought to define the effect of NSRT on myocardial function as well as various markers of hypertrophy including the expression of tumor necrosis factor (TNF)-alpha, a cytokine capable of producing fibrosis, left ventricular hypertrophy (LVH), and cardiomyopathy., Methods and Results: We performed endomyocardial biopsies of the RV side of the septum and echocardiograms on 15 HOCM patients at baseline and after successful NSRT. Comparative analysis on paired myocardial samples were performed to determine the effects of NSRT on LVH, end-diastolic volume and chamber stiffness, myocyte size, collagen content, and TNF-alpha levels. At baseline, myocardial TNF-alpha levels were increased in all patients. After NSRT, myocyte size, collagen content, and TNF-alpha were significantly decreased. These changes were accompanied by an increase in left ventricular volumes and a reduction in LVH and chamber stiffness., Conclusions: We suggest that pressure overload in HOCM patients contributes to the development of hypertrophy. These data provide the initial experimental evidence to suggest that TNF-alpha may play a pathogenetic role in the hypertrophy of pressure overload.

Background: Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by left ventricular hypertrophy (LVH) in the absence of increased external load. Recently, nonsurgical septal reduction therapy (NSRT) with intracoronary ethanol has been introduced to treat severely symptomatic patients with outflow tract obstruction. Its long-term effects on LV mass, however, are unknown., Methods and Results: The LV size, function, and outflow tract gradient of 26 HOCM patients (53+/-15 years old) who underwent NSRT were assessed by echocardiography at baseline and 1 and 2 years after the procedure. LVH was evaluated by wall thickness of individual myocardial segments, planimetered myocardial area, and mass. The outflow gradient decreased from 36+/-6 mm Hg before NSRT to 0+/-3 mm Hg at 2 years (P<0.001), with patients experiencing symptomatic improvement (P<0.05). LV end-diastolic and end-systolic dimensions increased significantly at both 1 and 2 years (P<0.001). All parameters of LVH showed evidence of regression. LV mass decreased (301+/-78 g at baseline, 223+/-5 g at 1 year, and 190+/-58 g at 2 years; P<0.01), with the 2-year reduction in mass related to infarct size and the acute reduction in outflow tract gradient (r=0.48, P<0.05 and r=0.63, P<0.01, respectively)., Conclusions: NSRT results in LV remodeling that is characterized by an increase in LV size and a decrease in the extent of LVH.

Objectives: We sought to evaluate the mechanisms by which nonsurgical septal reduction therapy (NSRT) reduces left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic obstructive cardiomyopathy (HOCM) both acutely and on a long-term basis., Background: NSRT reduces LVOT obstruction in patients with HOCM and leads to symptomatic improvement. The mechanisms involved, however, are not well studied., Methods: An initial group of 30 HOCM patients (age 46 +/- 17, 16 women) who underwent NSRT had echocardiographic studies performed at baseline and six months after the procedure. Measurements included LVOT diameter, end-diastolic distance between the anterior mitral leaflet and interventricular septum, septal base function and the angle between LV systolic flow and the protruding mitral leaflets. In addition, pulse Doppler recordings at a point 2.5 cm apical to the mitral valve were acquired and analyzed for peak and mean ejection velocity, peak acceleration rate and the ratio of acceleration time to ejection time (AT/ET)., Results: Significant changes were observed after the procedure, with widening in the LVOT, thinning and akinesis of the septal base, decrease in the angle between LV systolic flow and the protruding mitral leaflets, a decrease in peak acceleration rate and an increase in AT/ET. All of these variables had significant relations with the decrease in LVOT obstruction (r = 0.5 to 0.79, p < 0.01). These correlations were then evaluated in a test group of 15 patients who underwent echocardiographic examinations at baseline, acutely in the catheterization laboratory with ethanol injection and at six weeks post NSRT. Acute changes in peak acceleration rate (r = 0.65) and AT/ET (r = 0.73) related significantly (p < 0.01) to the decrease in LVOT obstruction with ethanol. At six weeks, changes similar to those noted in the initial group were observed in LVOT geometry, the angle between LV systolic flow and the protruding mitral leaflets, peak acceleration rate and AT/ET. In both populations combined, these parameters accounted for 72% to 77% of the variance in gradient reduction., Conclusions: Changes in LV ejection dynamics and septal base function account in part for the acute relief of LVOT gradient after NSRT. The long-term relief of obstruction is dependent on remodeling of LVOT as well as the changes in LV ejection.

Medical therapy for managing atrial fibrillation remains less than satisfactory. Electrical therapy such as right atrial (RA) pacing was shown to reduce rate of recurrence of atrial fibrillation, while evidently dual-site pacing was more effective than single-site pacing. However, similarities and/or differences in the electrophysiological consequences of single-site and dual-site RA pacing are unclear. Our objective was to simultaneously map RA and left atrial (LA) activation patterns and compare intra-atrial and interatrial activation properties during single-site and dual-site RA pacing in the normal canine heart. Basket-shaped catheters carrying 64 electrodes were deployed under the guidance of fluoroscopy and echocardiography into both the RA and LA of 7 dogs. Basket unipolar electrograms were simultaneously recorded while pacing at high lateral RA (HRA) alone, at inferior RA septum (RAS) alone, and at both sites simultaneously. We found that pacing at HRA alone resulted in the longest interatrial conduction time (47+/-6 ms). Pacing at RAS alone significantly shortened interatrial conduction time (29+/-5 ms) and completely activated both the RA and LA simultaneously (70+/-6 ms and 69+/-8 ms, respectively). Dual-site pacing at HRA and RAS significantly abbreviated RA complete activation time (52+/-7 ms), but did not alter interatrial conduction time or LA activation pattern compared to pacing at RAS alone. In conclusion, single-site pacing at RAS shortened interatrial conduction time compared to HRA and completely activated both atria simultaneously in canines with normal atria. In addition to shortening interatrial conduction time, dual-site pacing at HRA and RAS abbreviated RA complete activation time.

Objective: The objective of this study is to evaluate the one-year outcome of the first 50 patients who underwent nonsurgical septal reduction for symptomatic hypertrophic obstructive cardiomyopathy at our institution., Background: Left ventricular outflow tract obstruction is an important determinant of clinical symptoms in patients with hypertrophic obstructive cardiomyopathy. Nonsurgical septal reduction is a new therapy that has been shown to result in left ventricular outflow tract gradient reduction and resolution of symptoms immediately after the procedure and on midterm follow-up., Methods: Fifty patients with hypertrophic obstructive cardiomyopathy who underwent nonsurgical septal reduction at our institution and completed 1-year follow-up are described. Complete history, physical examination, two-dimensional echocardiography with Doppler and exercise treadmill testing have been analyzed., Results: The mean age of the study group was 53 +/- 17 years. All patients had refractory symptoms before enrollment. Ninety-four percent had class III or IV New York Heart Association class symptoms at baseline compared to none at 1 year (p < 0.001). The exercise duration increased by 136 s at 1 year (p < 0.021). Only 20% of patients were either receiving beta-blockers or calcium-channel blockers on follow-up. The resting left ventricular outflow tract gradient decreased from 74 +/- 23 mm Hg to 6 +/- 18 mm Hg (p < 0.01) and from 84 +/- 28 mm Hg to 30 +/- 33 mm Hg (p < 0.01) in patients with dobutamine-provoked gradient at one year. These changes are associated with decreased septal thickness and preserved systolic function., Conclusion: Nonsurgical septal reduction therapy is an effective therapy for symptomatic patients with hypertrophic obstructive cardiomyopathy with persistence of the favorable outcome up to one year after the procedure.

Objectives: The purpose of this study was to evaluate changes in left ventricular (LV) filling, left atrial (LA) volumes and function six months after nonsurgical septal reduction therapy (NSRT) for hypertrophic obstructive cardiomyopathy (HOCM)., Background: Patients with HOCM frequently have enlarged left atria, which predisposes them to atrial fibrillation. Nonsurgical septal reduction therapy results in significant reduction in left ventricular outflow tract (LVOT) obstruction and symptomatic improvement. However, its effect on LV passive filling volume, LA volumes and function is not yet known., Methods: Thirty patients with HOCM underwent treadmill exercise testing as well as 2-dimensional and Doppler echocardiography before and six months after NSRT. Data included clinical status, exercise duration, LVOT gradient, mitral regurgitant (MR) volume, LV pre-A pressure and LA volumes. Left atrial ejection force and kinetic energy (KE) were computed noninvasively and were compared with 12 age-matched, normal subjects., Results: New York Heart Association (NYHA) class was lower and exercise duration was longer (p < 0.05) six months after NSRT. The LVOT gradient, MR volume and LV pre-A pressure were all significantly reduced. HOCM patients had larger atria, which had a higher ejection force and KE, compared with normal subjects (p < 0.01). After NSRT, LV passive filling volume increased (p < 0.01), whereas LA volumes, ejection force and KE decreased (p < 0.01). Reduction in LA maximal volume was positively related to changes in LV pre-A pressure (r = 0.8, p < 0.05) and MR volume (0.4, p < 0.05). Changes in LA ejection force were positively related to changes in LA pre-A volume (r = 0.7, p < 0.01) and KE (r = 0.81, p < 0.01). The increase in exercise duration paralleled the increase in LV passive filling volume (r = 0.85, p < 0.05)., Conclusions: Nonsurgical septal reduction therapy results in an increase in LV passive filling volume and a reduction in LA size, ejection force and KE.

Background: The spread of activation between the right atrium (RA) and left atrium (LA), particularly along the right and left aspects of the interatrial septum, is not clear., Methods and Results: Basket-shaped catheters carrying 64 electrodes were deployed into both the RA and LA of 10 dogs. Position and orientation of the baskets were determined by fluoroscopy and echocardiography. Basket unipolar electrograms were simultaneously recorded in each dog during sinus rhythm, right ventricular pacing, and pacing of the right septum through the basket in the superior and inferior regions. Isochrone maps depicting all aspects of the atria, including the septum, were compared. During sinus rhythm and superior right septal pacing, wave fronts propagated predominantly from superior to inferior regions on both the right and left septum. However, activation of the left septum was delayed compared with the right septum. During right ventricular pacing and inferior right septal pacing, activation of the septum was discordant; 1 wave front propagated rapidly on the right septum from inferior to superior regions, whereas 2 opposing wave fronts originated on the left septum in both the superior and inferior regions. The left septum was activated predominantly by the superior wave front. Activation of the left septum was completed in a significantly shorter time during pacing of the right septum in the inferior region compared with the superior region., Conclusions: In dogs, activation of the right and left aspects of the interatrial septum is discordant. Electrical connections are present between the RA and LA in regions superior as well as inferior to the septum.

Background: Nonsurgical septal reduction therapy (NSRT) decreases left ventricular outflow tract (LVOT) gradient and improves symptoms in patients with hypertrophic obstructive cardiomyopathy (HOCM). NSRT effects on LV/left ventricular diastolic function are currently unknown., Methods and Results: HOCM patients (n=29) had Doppler echocardiography at baseline and 6 months after NSRT to evaluate changes in LV volume, pre-A-wave pressure, early diastolic mitral annulus velocity (Ea) by tissue Doppler, and tau. At 6 months, a significant reduction in LVOT gradient (from 53.6+/-15 to 6+/-5 mm Hg; P<0.001) was accompanied by improvement in exercise duration (from 284+/-147 to 408+/-178 seconds; P=0.04) and New York Health Association class (from III to I; P<0.001). Pre-A pressure (18+/-6 to 14+/-5 mm Hg; P<0.01) and tau (62+/-8 to 51+/-8 ms; P<0.01) decreased, whereas Ea (5.8+/-1.8 to 8+/-1.8 cml/s; P<0.01) and LV end-diastolic volume (117+/-16 to 130+/-22 mL; P<0.01) increased., Conclusions: NSRT improves LV relaxation and compliance, which contributes to the symptomatic relief seen at 6 months.

Background: Conventional Doppler parameters are unreliable for estimating left ventricular (LV) filling pressures in hypertrophic cardiomyopathy (HCM). This study was undertaken to evaluate flow propagation velocity by color M-mode and early diastolic annular velocity (Ea) by tissue Doppler 2 new indices of LV relaxation, combined with mitral E velocity for estimation of filling pressures in HCM., Methods and Results: Thirty-five HCM patients (52+/-15 years) underwent LV catheterization simultaneously with 2-dimensional and Doppler echocardiography. Pulsed Doppler echocardiography of mitral and pulmonary venous flows was obtained along with flow propagation velocity and Ea. LV preA pressure had weak or no relations with mitral, pulmonary venous velocities and atrial volumes. In contrast, preA pressure related strongly to E velocity/flow propagation velocity (r=0.67; SEE=4) and E/Ea (r=0.76; SEE=3.4). In 17 patients with repeat measurements, preA pressure changes were well detected by measuring E velocity/flow propagation velocity (r=0.68; P=0.01) or E/Ea (r=0.8; P<0.001). PreA pressure estimation with these 2 methods was tested prospectively in 17 additional HCM patients with good results (E velocity/flow propagation velocity, r=0.76; E/Ea, r=0.82)., Conclusions: LV filling pressures can be estimated with reasonable accuracy in HCM patients by measuring E velocity/flow propagation velocity or E/Ea. These ratios also track changes in filling pressures.

Background: Left ventricular outflow tract (LVOT) obstruction is frequently responsible for symptoms in hypertrophic obstructive cardiomyopathy (HOCM). Medical therapy is often not sufficient to control these symptoms, and surgical myotomy-myomectomy is required., Methods and Results: We enrolled 33 symptomatic patients with HOCM and obstruction (>/=40 mm Hg gradient at rest or >/=60 mm Hg dobutamine-provoked). By contrast echocardiography, the bulging septum was localized and infarcted by injection of 2 to 5 mL of absolute ethanol into the septal artery(ies) supplying the hypertrophied area. Baseline echocardiograms with Doppler, myocardial perfusion tomograms, and treadmill exercise or pharmacological testing were compared with those at 6 weeks and 6 months. The mean rise in creatine kinase was 1964+/-796 U. All patients experienced symptomatic relief; NYHA class decreased from 3. 0+/-0.5 to 0.9+/-0.6 (P<0.001). Exercise time increased from 286+/-193 to 421+/-181 seconds (P=0.03). The resting and dobutamine-provoked gradient decreased from 49+/-33 and 96+/-34 mm Hg to 9+/-19 (P<0.001) and 24+/-31 mm Hg (P<0.001), respectively. Echocardiograms repeated at 6 weeks after the procedure showed a 28% reduction in septal thickness and 17% reduction in left ventricular mass. Myocardial perfusion imaging showed a "septal amputation pattern," with scarring in the upper and middle septal areas. Complete heart block developed in 11 patients, who then required permanent pacemaker implantation., Conclusions: Echocardiography-guided ethanol septal reduction in patients with HOCM is a safe, minimally invasive procedure that provides symptomatic relief with improved hemodynamic and left ventricular parameters.

Objectives: This study was undertaken to evaluate the ability of myocardial contrast echocardiography (MCE) to guide the targeted delivery of ethanol during nonsurgical septal reduction therapy (NSRT) and to assess the relation between the MCE risk area and infarct size determined by enzymatic and radionuclide methods., Background: NSRT with intracoronary ethanol is a new promising treatment for patients with hypertrophic obstructive cardiomyopathy (HOCM). Proper localization and quantification of the septal infarct before ethanol injection are highly desirable. MCE can provide accurate delineation of the vascular territory of the coronary arteries., Methods: Twenty-nine patients with HOCM and maximal medical therapy underwent NSRT. The left ventricular outflow tract (LVOT) gradient by Doppler echocardiography at baseline was 53 +/- 16 mm Hg (mean +/- SD). Before NSRT, MCE was performed in all patients with intracoronary sonicated albumin (Albunex). Diluted sonicated albumin (Albunex) was selectively injected into the septal perforator arteries during simultaneous transthoracic imaging. Immediately after MCE, ethanol was injected into the same vessel. Plasma total creatine kinase (CK), total CK-MB fraction and CK-MB fraction subforms were measured at baseline and serially for 36 h., Results: LVOT gradient decreased to 12 +/- 6 mm Hg (p < 0.001) after NSRT. Accurate mapping of the vascular beds of the septal perforators was successfully attained in all patients by MCE. Furthermore, the MCE risk area correlated well with peak CK (r = 0.79, p < 0.001). Six weeks after NSRT, 23 patients underwent myocardial perfusion studies performed with single-photon emission computed tomography (SPECT). Mean SPECT septal perfusion defect size involved 9.5 +/- 6% of the left ventricle and correlated well with MCE area (r = 0.7), with no statistically significant difference between the risk area estimated by MCE and that by SPECT., Conclusions: Estimation of the size of the septal vascular territory with MCE is accurate, safe and feasible in essentially all patients during NSRT. MCE can delineate the perfusion bed of the septal perforators and can predict the infarct size that follows ethanol injection.

Recent reports have raised doubts regarding the safety and efficacy of the blind subclavian venipuncture technique for intracardiac lead implantation. To permit a more lateral entry, we used a simple subclavian venogram performed through the brachial vein of the ipsilateral arm of 22 consecutive unselected patients undergoing lead implantation (19 permanent pacemakers and 3 intracardiac defibrillators). A total of 35 leads were implanted (31 left pectoral and 4 right pectoral). Lead insertion by venogram technique was used successfully in all patients. Two inconsequential arterial punctures occurred. There were no pneumothoraces infections, or other complications. Lateral placement should facilitate lead manipulation and minimize "subclavian crush." The method of ipsilateral venogram guided lead insertion appears to be safe and reliable and deserves consideration in patients who require permanent lead placement via the subclavian vein approach.

By pacing both atria simultaneously, one could reliably predict and optimize left-sided AV timing without concern for IACT. With synchronous depolarization of the atria, reentrant arrhythmias might be suppressed. We studied four male patients (73 +/- 3 years) with paroxysmal atrial fibrillation and symptomatic bradyarrhythmias using TEE and fluoroscopy as guides; a standard active fixation screw-in lead (Medtronic model #4058) was attached to the interatrial septum and a standard tined lead was placed in the ventricle. The generators were Medtronic model 7960. The baseline ECG was compared to the paced ECG and the conduction time were measured to the high right atrium, distal coronary sinus and atrial septum in normal sinus rhythm, atrial septal pacing, and AAT pacing. On the surface ECG, no acceleration or delay in AV conduction was noted during AAI pacing from the interatrial septum as compared with normal sinus rhythm. The mean interatrial conduction time for all 4 patients was 106 +/- 2 ms; the interatrial conduction time measured during AAT pacing utilizing the atrial septal pacing lead was 97 +/- 4 ms (P = NS). During atrial septal pacing, the mean conduction time to the high right atrium was 53 +/- 2 ms. The mean conduction time to the lateral left atrium during atrial septal pacing, was likewise 53 +/- 2 ms. We conclude that it is possible to pace both atria simultaneously from a single site using a standard active fixation lead guided by TEE and fluoroscopy. Such a pacing system allows accurate timing of the left-sided AV delay.

The use of pacing techniques for the treatment of atrial tachyarrhythmias has been advocated for more than 30 years. Although it has played a beneficial role in the management of paroxysmal supraventricular tachycardia (PSVT) in drug-refractory patients, tachycardia acceleration and development of atrial fibrillation has been the major drawback. With the availability of radiofrequency catheter ablation therapy, the use of implantable antitachycardia devices for PSVT is currently negligible. From retrospective and small control studies it has been shown that atrial or dual-chamber pacing in patients with sick sinus syndrome has been associated with a lower incidence of paroxysmal atrial flutter or fibrillation than in those who received a ventricular pacemaker. Furthermore, recent studies have reported the potential benefit of reducing frequency of paroxysmal atrial flutter and fibrillation with multisite atrial pacing. As a result, there is a resurgence of research interest in antitachycardia pacing for prevention of atrial tachyarrhythmias. This paper briefly describes the basic aspects of antitachycardia pacing, reviews the data on the use of implantable antitachycardia devices for PSVT and the selection of patients, and assesses the current status of research on atrial pacing for prevention of paroxysmal atrial flutter and fibrillation.

Transvenous pacemaker lead malposition in the left ventricle occurs rarely and requires a high index of suspicion for proper diagnosis. The case of a woman with unintentional lead placement in the left ventricle is presented. She had two episodes of transient neurologic deficits, possible secondary to embolic events, and was started on oral anticoagulants. Chest x-ray and electrocardiogram (ECG) suggested pacemaker lead malposition and transesophageal echocardiography revealed sinus venosus atrial septal defect. The lead was shown to cross the atrial septum and the mitral valve to the left ventricle. The malpositioned lead was successfully removed from the left ventricle at the time of surgical repair of the atrial septal defect. The potential value of 12-lead ECG, chest x-ray, posteroanterior and lateral views, and echocardiography in the diagnosis of pacemaker lead malposition are discussed and recommendations to avoid this complication at the time of pacemaker implant are outlined.

The hemodynamic effects of two different pacing modes--rate adaptive atrial (AAIR) versus dual chamber (DDDR) pacing--were assessed in 12 patients with DDDR pacemakers during upright bicycle exercise first-pass radionuclide angiography using a multiwire gamma camera with tantalum-178 as a tracer. All patients had sinus node disease with intact AV conduction. Patients exercised to the same heart rate in random order in these two different pacing modes, AAIR and DDDR with AV delay (of 100 msec) selected to maintain 100% ventricular capture. Cardiac output increased significantly above baseline values during exercise in both pacing modes: 154 +/- 41% (mean +/- SEM, P = 0.002) with AAIR, versus 95 +/- 24% (P = 0.004) with DDDR (P = NS between the two modes). The peak filling rate, likewise, increased in both pacing modes (2.3 +/- 0.21 end-diastolic volumes/sec to 3.8 +/- 0.31 end-diastolic volumes/sec in AAIR [P = 0.0004] and 2.2 +/- 0.18 end-diastolic volumes/sec to 3.4 +/- 0.27 end-diastolic volumes/sec in DDDR [P = 0.0008]). LV ejection fraction was normal at rest (60 +/- 4%, SEM) and did not significantly change with submaximal exercise in either pacing mode (both 56%, P = NS). No significant changes in end-diastolic volume or stroke volume indexes occurred with exercise in either pacing mode. Our study demonstrates that in patients with normal resting LV function, AAIR and DDDR pacing are equally effective in attaining appropriate increases in cardiac output and LV filling during exercise.

Study Objective: To evaluate the effect of helicopter transport of acute myocardial infarction (AMI) patients after initiation of thrombolysis on bleeding complications through hospital discharge., Design: Prospectively identified incidence (cohort) study., Setting: Air medical service of tertiary-care teaching hospital., Types of Participants: Ninety-five consecutive AMI patients transported within 12 hours of the initiation of thrombolysis with recombinant tissue-type plasminogen activator were compared with 119 nontransported AMI patients treated in a similar manner., Results: The transported and nontransported populations were similar with regard to age, sex, and infarct location. Transport was well tolerated with no episodes of cardiac arrest or cardioversion occurring during transport. Hypotension requiring fluids or increased pressors occurred in 18 patients. Bleeding complications of all types occurred in 43.2% of the transported and 49.6% of the nontransported patients, respectively (relative risk, 0.87; 95% confidence interval, 0.65 to 1.17)., Conclusion: Helicopter transport of AMI patients after initiation of thrombolysis appears to be safe acutely and without a clinically significant increase in risk of bleeding complications through hospital discharge when accomplished by a highly skilled team.

Dual chamber, rate-modulated pacemakers provide the capability of augmenting the heart rate of patients with chronotropic incompetence but also may cause atrial arrhythmias because of high rate, competitive atrial pacing. We studied ten patients with two consecutive 24-hour Holter monitors during which they were alternately programmed to either DDD or DDDR pacing in random order. Maximum heart rates (max HR) were measured at every 15-minute interval during each 24-hour period. DDDR pacing showed rate augmentation, 80 +/- 7 average max HR when compared with DDD pacing, average max HR 76 +/- 5. These results were even more striking when waking hours (7 am to 10 pm) were compared: average max HR 86 +/- 7 DDDR versus 78 +/- 4 average max HR DDD. Several patients showed marked rate augmentation. Seven of ten patients preferred DDDR pacing over DDD pacing. In the entire population, DDDR pacing did not result in an increased number of atrial arrhythmias (1.25 atrial events/24 hour) when compared to DDD pacing (1.75 atrial events/24 hour). We conclude that DDDR pacing provides heart rate augmentation during daily life in a clinical population while not resulting in a significant increase in atrial arrhythmias.