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Ventricular assist devices (VADs), among which the HeartMate 3 (HM3) is the latest clinically approved representative, are often the therapy of choice for patients with end-stage heart failure. Despite advances in the prevention of pump thrombosis, rates of stroke and bleeding remain high. These complications are attributed to the flow field within the VAD, among other factors. One of the HM3's characteristic features is an artificial pulse that changes the rotor speed periodically by 4000 rpm, which is meant to reduce zones of recirculation and stasis. In this study, we investigated the effect of this speed modulation on the flow fields and stresses using high-resolution computational fluid dynamics. To this end, we compared Eulerian and Lagrangian features of the flow fields during constant pump operation, during operation with the artificial pulse feature, and with the effect of the residual native cardiac cycle. We observed good washout in all investigated situations, which may explain the low incidence rates of pump thrombosis. The artificial pulse had no additional benefit on scalar washout performance, but it induced rapid variations in the flow velocity and its gradients. This may be relevant for the removal of deposits in the pump. Overall, we found that viscous stresses in the HM3 were lower than in other current VADs. However, the artificial pulse substantially increased turbulence, and thereby also total stresses, which may contribute to clinically observed issues related to hemocompatibility., (© 2018 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

The growing population of failing single-ventricle (SV) patients might benefit from ventricular assist device (VAD) support as a bridge to heart transplantation. However, the documented experience is limited to isolated case reports. Considering the complex and different physiopathology of Norwood, Glenn, and Fontan patients and the lack of established experience, the aim of this work is to realize and test a lumped parameter model of the cardiovascular system able to simulate SV hemodynamics and VAD implantation effects to support clinical decision. Hemodynamic and echocardiographic data of 30 SV patients (10 Norwood, 10 Glenn, and 10 Fontan) were retrospectively collected and used to simulate patients' baseline. Then, the effects of VAD implantation were simulated. Simulation results suggest that the implantation of VAD: (i) increases the cardiac output and the mean arterial systemic pressure in all the three palliation conditions (Norwood 77.2 and 19.7%, Glenn 38.6 and 32.2%, and Fontan 17.2 and 14.2%); (ii) decreases the SV external work (Norwood 55%, Glenn 35.6%, and Fontan 41%); (iii) decreases the pressure pulsatility index (Norwood 65.2%, Glenn 81.3%, and Fontan 64.8%); (iv) increases the pulmonary arterial pressure in particular in the Norwood circulation (Norwood 39.7%, Glenn 12.1% and Fontan 3%); and (v) decreases the atrial pressure (Norwood 2%, Glenn 10.6%, and Fontan 8.6%). Finally, the VAD work is lower in the Norwood circulation (30.4 mL·mm Hg) in comparison with Fontan (40.3 mL·mm Hg) and to Glenn (64.5 mL·mm Hg) circulations. The use of VAD in SV physiology could be helpful to bridge patients to heart transplantations by increasing the CO and unloading the SV with a decrement of the atrial pressure and the SV external work. The regulation of the pulmonary flow is challenging because the Pap is increased by the presence of VAD. The hemodynamic changes are different in the different SV palliation step. The use of numerical models could be helpful to support patient and VAD selection to optimize the clinical outcome., (Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

An increasing number of devices can provide mechanical circulatory support (MCS) to patients with acute hemodynamic compromise and chronic end-stage heart failure. These devices work by different pumping mechanisms, have various flow capacities, are inserted by different techniques, and have different sites from which blood is withdrawn and returned to the body. These factors result in different primary hemodynamic effects and secondary responses of the body. However, these are not generally taken into account when choosing a device for a particular patient or while managing a patient undergoing MCS. In this review, we discuss fundamental principles of cardiac, vascular, and pump mechanics and illustrate how they provide a broad foundation for understanding the complex interactions between the heart, vasculature, and device, and how they may help guide future research to improve patient outcomes., (Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

As the aortic valve (AV) opens, the pump pressure head remains constant, which is reflected as a "notch/plateau" in pump pressure and flow signals. However, instantaneous flow estimation may be influenced by friction and is particularly difficult in axial pumps. Therefore, a new method to determine the duration of AV opening based on the area under the curve (AUC) of the power spectral density analysis of pump speed signal was developed. Data from patients implanted with HeartWare HVAD left ventricular assist device were studied at different pump speeds, with simultaneous transthoracic echocardiography in two cohorts. In the first group, pump data of 15 patients were used to investigate the ability to discriminate between an open and closed AV. In the second cohort of a further 13 patients, the duration of AV opening was measured from digitized M-mode images, and the relationship between the AV opening time and the new method assessed. In 14 of the initial 15 patients, AV status could be discriminated using only one threshold for all patients. In the second cohort, gradual speed reduction resulted in aortic valve opening in 12 of the 13 patients. The correlation between AV opening duration and AUC was 0.96 ± 0.03. Regression analysis indicated a linear relationship in each of the patients with a small error between the fit and the measured opening time (root mean square error = 11.0 ± 7.6 ms). However, the slopes (69.0 ± 52.8) and intercepts (-31.4 ± 78.0) varied widely between patients. The sensitivity and specificity for the new method using AUC threshold of 0.95 for aortic valve closure was 95% and 91%, respectively. The newly developed method to detect AV opening not only provides information on the AV status during LVAD support (open/closed) but also gives insight into the duration of AV opening. Because the slope of the relationship varies from patient to patient, initial training and adaptation of the method to each patient seems to be required., (Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

Considering the lack of donors, ventricular assist devices (VADs) could be an alternative to heart transplantation for failing Fontan patients, in spite of the lack of experience and the complex anatomy and physiopathology of these patients. Considering the high number of variables that play an important role such as type of Fontan failure, type of VAD connection, and setting (right VAD [RVAD], left VAD [LVAD], or biventricular VAD [BIVAD]), a numerical model could be useful to support clinical decisions. The aim of this article is to develop and test a lumped parameter model of the cardiovascular system simulating and comparing the VAD effects on failing Fontan. Hemodynamic and echocardiographic data of 10 Fontan patients were used to simulate the baseline patients' condition using a dedicated lumped parameter model. Starting from the simulated baseline and for each patient, a systolic dysfunction, a diastolic dysfunction, and an increment of the pulmonary vascular resistance were simulated. Then, for each patient and for each pathology, the RVAD, LVAD, and BIVAD implantations were simulated. The model can reproduce patients' baseline well. In the case of systolic dysfunction, the LVAD unloads the single ventricle and increases the cardiac output (CO) (35%) and the arterial systemic pressure (Pas) (25%). With RVAD, a decrement of inferior vena cava pressure (Pvci) (39%) was observed with 34% increment of CO, but an increment of the single ventricle external work (SVEW). With the BIVAD, an increment of Pas (29%) and CO (37%) was observed. In the case of diastolic dysfunction, the LVAD increases CO (42%) and the RVAD decreases the Pvci, while both increase the SVEW. In the case of pulmonary vascular resistance increment, the highest CO (50%) and Pas (28%) increment is obtained with an RVAD with the highest decrement of Pvci (53%) and an increment of the SVEW but with the lowest VAD power consumption. The use of numerical models could be helpful in this innovative field to evaluate the effect of VAD implantation on Fontan patients to support patient and VAD type selection personalizing the assistance., (Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

It has been shown that left ventricular assist devices (LVADs) increase the survival rate in end-stage heart failure patients. However, there is an ongoing demand for an increased quality of life, fewer adverse events, and more physiological devices. These challenges necessitate new approaches during the design process. In this study, computational fluid dynamics (CFD), lumped parameter (LP) modeling, mock circulatory loops (MCLs), and particle image velocimetry (PIV) are combined to develop a numerical Pump Testing Framework (nPTF) capable of analyzing local flow patterns and the systemic response of LVADs. The nPTF was created by connecting a CFD model of the aortic arch, including an LVAD outflow graft to an LP model of the circulatory system. Based on the same geometry, a three-dimensional silicone model was crafted using rapid prototyping and connected to an MCL. PIV studies of this setup were performed to validate the local flow fields (PIV) and the systemic response (MCL) of the nPTF. After validation, different outflow graft positions were compared using the nPTF. Both the numerical and the experimental setup were able to generate physiological responses by adjusting resistances and systemic compliance, with mean aortic pressures of 72.2-132.6 mm Hg for rotational speeds of 2200-3050 rpm. During LVAD support, an average flow to the distal branches (cerebral and subclavian) of 24% was found in the experiments and the nPTF. The flow fields from PIV and CFD were in good agreement. Numerical and experimental tools were combined to develop and validate the nPTF, which can be used to analyze local flow fields and the systemic response of LVADs during the design process. This allows analysis of physiological control parameters at early development stages and may, therefore, help to improve patient outcomes., (Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.)

It is known that examining turbulence effects on medical devices has an important effect in design and optimization of blood-contacting devices. CFD has been commonly used on prosthetic heart valves, stents, and Ventricular Assist Devices (VADs) in both the design process and also on hemodynamics of the flow characteristics. In this study, flows in the FDA nozzle were modeled to examine Reynolds stresses in the whole domain. The flow behavior was determined by applying the Reynolds-Averaged Navier-Stokes model of turbulence (k-ω SST) to simulate five distinctive experimental cases in the nozzle taken from the literature. The Reynolds stress frequencies are determined for the five different experimental conditions. Results showed that the highest velocity case (corresponding throat Reynolds number of 6500) has much higher Reynolds stresses with a high number of frequencies. However, the lowest velocity case has very small Reynolds numbers in a very high frequency. When different parts of the nozzle were examined, the Reynolds stress values showed more fluctuations for the higher velocities and more regular profiles for the lower velocity cases. [ABSTRACT FROM AUTHOR]

The characterization of intraventricular flow is critical to evaluate the efficiency of fluid transport and potential thromboembolic risk but challenging to measure directly in advanced heart failure (HF) patients with left ventricular assist device (LVAD) support. The study aims to validate an in-house mock loop (ML) by simulating specific conditions of HF patients with normal and prosthetic mitral valves (MV) and LVAD patients with small and dilated left ventricle volumes, then comparing the flow-related indices result of vortex parameters, residence time (RT), and shear-activation potential (SAP). Patient-specific inputs for the ML studies included heart rate, end-diastolic and end-systolic volumes, ejection fraction, aortic pressure, E/A ratio, and LVAD speed. The ML effectively replicated vortex development and circulation patterns, as well as RT, particularly for HF patient cases. The LVAD velocity fields reflected altered flow paths, in which all or most incoming blood formed a dominant stream directing flow straight from the mitral valve to the apex. RT estimation of patient and ML compared well for all conditions, but SAP was substantially higher in the LVAD cases of the ML. The benchtop system generated comparable and reproducible hemodynamics and fluid dynamics for patient-specific conditions, validating its reliability and clinical relevance. This study demonstrated that ML is a suitable platform to investigate the fluid dynamics of HF and LVAD patients and can be utilized to investigate heart-implant interactions. [ABSTRACT FROM AUTHOR]

In the United States, about one million people are seen to visit the operating theater for cardiac surgery annually. However, nearly half of these visits result in complications such as renal, neurological, and cardiac injury of varying degrees. Historically, many mechanisms and approaches have been explored in attempts to reduce injuries associated with cardiac surgery and percutaneous procedures. Devices such as cardioplegia, mechanical circulatory support, and other methods have shown promising results in managing and preventing life-threatening cardiac-surgery-related outcomes such as heart failure and cardiogenic shock. Comparably, cardioprotective devices such as TandemHeart, Impella family devices, and venoarterial extracorporeal membrane oxygenation (VA-ECMO) have also been proven to show significant cardioprotection through mechanical support. However, their use as interventional agents in the prevention of hemodynamic changes due to cardiac surgery or percutaneous interventions has been correlated with adverse effects. This can lead to a rebound increased risk of mortality in high-risk patients who undergo cardiac surgery. Further research is necessary to delineate and stratify patients into appropriate cardioprotective device groups. Furthermore, the use of one device over another in terms of efficacy remains controversial and further research is necessary to assess device potential in different settings. Clinical research is also needed regarding novel strategies and targets, such as transcutaneous vagus stimulation and supersaturated oxygen therapy, aimed at reducing mortality among high-risk cardiac surgery patients. This review explores the recent advances regarding the use of cardioprotective devices in patients undergoing percutaneous procedures and cardiac surgery. [ABSTRACT FROM AUTHOR]

To investigate the effect of tandem use of transient balloon occlusion of the descending aorta (AO) and percutaneous left ventricular assist device (pl-VAD) during cardiopulmonary resuscitation in a large animal model of prolonged cardiac arrest. Ventricular fibrillation was induced and left untreated for 8 minutes followed by 16 minutes of mechanical CPR (mCPR) in 24 swine, under general anesthesia. Animals were randomized to 3 treatment groups (n = 8 per group): A) pL-VAD (Impella CP®) B) pL-VAD+AO, and C) AO. Impella CP® and the aortic balloon catheter were inserted via the femoral arteries. mCPR was continued during treatment. Defibrillation was attempted 3 times starting at minute 28 and then every 4 minutes. Haemodynamic, cardiac function and blood gas measurements were recorded for up to 4 hours. Coronary perfusion pressure (CoPP) in the pL-VAD+AO Group increased by a mean (SD) of 29.2(13.94) mmHg compared to an increase of 7.1(12.08) and 7.1(5.95) mmHg for groups pL-VAD and AO respectively (p = 0.02). Similarly, cerebral perfusion pressure (CePP) in pL-VAD+AO increased by a mean (SD) of 23.6 (6.11), mmHg compared with 0.97 (9.07) and 6.9 (7.98) mmHg for the other two groups (p < 0.001). The rate of return of spontaneous heartbeat (ROSHB) was 87.5%, 75%, and 100% for pL-VAD+AO, pL-VAD, and AO. Combined AO and pL-VAD improved CPR hemodynamics compared to either intervention alone in this swine model of prolonged cardiac arrest. [ABSTRACT FROM AUTHOR]

Introduction: Through concerted endeavours in the fields of surgery, medicine, and biomedical engineering, patronized by government and industry, ventricular assist devices have become an established surgical treatment to support the failing heart, which could easily and simply surpass the frequency of heart transplantation. Be it as it may, complications and adverse events have unfolded, and these facilitated the way to newer biomedically-engineered pump designs in search of the perfect support for a failing heart. Areas covered: This review focuses on the evolution of the continous-flow ventricular assist device as an accepted mode of treatment in advanced heart failure, as a bridge to myocardial recovery, as a bridge to heart transplantation and as a permanent therapy, with its attendant complications and long-term outcome. Expert commentary: Continuous flow devices offer improved durability, less surgical trauma due to their smaller size, high-energy efficiency, and lower thrombogenicity, regardless of administration of single or dual anti-thrombotic therapy. These benefits translate into better survival, lower frequency of adverse events, improved quality of life and higher functional capacity of patients. Through ceaseless innovations and technology, newer pumps have been developed; however, none has been proven to be superior over the others. [ABSTRACT FROM AUTHOR]

Continuous flow ventricular assist devices (cfVADs) while effective in advanced heart failure, remain plagued by thrombosis related to abnormal flows and elevated shear stress. To limit cfVAD thrombosis, patients utilize complex anti-thrombotic regimens built upon a foundation of aspirin (ASA). While much data exists on ASA as a modulator of biochemically-mediated platelet activation, limited data exists as to the efficacy of ASA as a means of limiting shear-mediated platelet activation, particularly under elevated shear stress common within cfVADs. We investigated the ability of ASA (20, 25 and 125 μM) to limit shear-mediated platelet activation under conditions of: 1) constant shear stress (30 dynes/cm 2 and 70 dynes/cm 2 ); 2) dynamic shear stress, and 3) initial high shear exposure (70 dynes/cm 2 ) followed by low shear exposure – i.e. a platelet sensitization protocol, utilizing a hemodynamic shearing device providing uniform shear stress in vitro . The efficacy of ASA to limit platelet activation mediated via passage through a clinical cfVAD system (DeBakey Micromed) in vitro was also studied. ASA reduced platelet activation only under conditions of low shear stress (38% reduction compared to control, n = 10, p < 0.004), with minimal protection at higher shear stress and under dynamic conditions (n = 10, p > 0.5) with no limitation of platelet sensitization. ASA had limited ability (25.6% reduction in platelet activation rate) to modulate shear-mediated platelet activation induced via cfVAD passage. These findings, while performed under “deconstructed” non-clinical conditions by utilizing purified platelets alone in vitro , provide a potential contributory mechanistic explanation for the persistent thrombosis rates experienced clinically in cfVAD patients despite ASA therapy. An opportunity exists to develop enhanced pharmacologic strategies to limit shear-mediated platelet activation at elevated shear levels associated with mechanical circulatory support devices. [ABSTRACT FROM AUTHOR]

While Fontan palliation in the form of the total cavopulmonary connection has improved the management of congenital single ventricle physiology, long-term outcomes for patients with this disease are suboptimal due to the lack of two functional ventricles. Researchers have shown that ventricular assist devices ( VADs) can normalize Fontan hemodynamics. To minimize blood contacting surfaces of the VAD, we evaluated the use of an external compression device ( C- Pulse Heart Assist System, Sunshine Heart Inc.) as a Fontan assist device. A mock circulation was developed to mimic the hemodynamics of a hypertensive Fontan circulation in a pediatric patient. The Sunshine C- Pulse compression cuff was coupled with polymeric valves and a compressible tube to provide nonblood-contacting pulsatile flow through the Fontan circulation. The effect of the number, one or two, and placement of valves, before or after the compression cuff, on inferior vena cava pressure ( IVCP) was studied. In addition, the effect of device inflation volume and compression rate on maintaining low IVCP was investigated. With one valve located before the cuff, the device was unable to maintain an IVCP below 15.5 mm Hg. With two valves, the C- Pulse was able to maintain IVCP as low as 8.5 mm Hg. The C- Pulse provided pulsatile flow and pressure through the pulmonary branch of the mock circulation with a pulse pressure of 16 mm Hg and 180 mL/min additional flow above unassisted flow. C- Pulse compression reduced IVCP below 12 mm Hg with 13 cc inflation volume and compression rates above 105 bpm. This application of an external compression device combined with two valves has potential for use as an artificial right ventricle by maintaining low IVCP and providing pulsatile flow through the lungs. [ABSTRACT FROM AUTHOR]

Fixed pulmonary hypertension (PH) is a contraindication for heart transplantation (HTx). Several studies showed that use of a left ventricular assist device (LVAD) in patients with fixed PH who were initially deemed ineligible for HTx effectively decreased pulmonary arterial pressure (PAP), thus permitting HTx. We recently encountered a candidate for HTx who had severe PH with extremely high pulmonary vascular resistance (PVR). A 27-year-old female who had been diagnosed with dilated-phase hypertrophic cardiomyopathy and who was approved for HTx at age 25 was referred to our institute because of severe fatigability with moderate dyspnea even at rest due to severe bilateral heart failure. Despite continuous inotrope infusion, the patient's symptoms were not relieved. Right heart catheterization (RHC) disclosed a PAP of 62/40 mmHg with severely reduced cardiac output (1.8 l/min). A PVR of 15.9 Wood units suggested progressive worsening of left ventricular function with almost irreversible remodeling of the pulmonary vasculature, and the patient was thought to be contraindicated for HTx. Following 3 weeks of aggressive medical treatment, repeat RHC demonstrated PVR lowering to 8.16 Wood units. This suggested it was likely that PVR could be reversed, and the patient underwent LVAD implantation. RHC performed after LVAD implantation showed a fall in PVR from the initial, extremely high measurement of 15.9 Wood units to 3.4 Wood units at 2 months postoperatively, and to 2.2 Wood units at 1 year. The patient is currently awaiting HTx with favorable LVAD support. [ABSTRACT FROM AUTHOR]

Ventricular assist devices (VADs) are used to improve the systemic circulation and to decrease ventricular loading in patients with hemodynamic instability that is refractory to pharmacologic therapies. During an acute critical event, percutaneous devices are preferred because of their rapid deployment, since implantable devices require more extensive procedures. Implantable devices are used for patients with established end-stage heart failure as a bridge to heart transplantation, recovery or destination therapy. This report reviews mechanical principles and clinical studies regarding percutaneous VAD to address their potential renal effects. Since the focus of this study is set on devices that are dedicated to cardiac support only, extracorporeal membrane oxygenation systems are not included. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable rotary blood pump (IRBP), have been widely used as a predictive tool to investigate the interaction between the CVS and the IRBP under various operating conditions. The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total blood volume on the efficiency of rotary pump assistance, using an optimized dynamic heart-pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean pump speed and the circulatory perturbations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, pump assistance ratio, and pump flow pulsatility from both the greyhound experiments and model simulations are demonstrated. Furthermore, the applicability of some of the previously proposed control parameters, that is, pulsatility index (PI), gradient of PI with respect to pump speed, pump differential pressure, and aortic pressure are discussed based on our observations from experimental and simulation results. It was found that previously proposed control strategies were not able to perform well under highly varying circulatory conditions. Among these, control algorithms which rely on the left ventricular filling pressure appear to be the most robust as they emulate the Frank-Starling mechanism of the heart. [ABSTRACT FROM AUTHOR]

Pulmonary hypertension (PH) unresponsive to pharmacological intervention is considered a contraindication for orthotopic heart transplantation (OHTX) due to risk of postoperative right-heart failure. In this prospective study, we describe our experience with a treatment strategy of improving severe PH in heart transplant candidates by means of ventricular assist device (VAD) implantation and subsequent OHTX. In 11 heart transplantation candidates with severe PH unresponsive to pharmacological intervention we implanted VAD with the aim of achieving PH to values acceptable for OHTX. In all patients we observed significant drop in pulmonary pressures, PVR and TPG (p<0.001 for all) 3 months after VAD implantation to values sufficient to allow OHTX. Seven patients underwent transplantation (mean duration of support 216 days) while none of patients suffered right-side heart failure in postoperative period. Two patients died after transplantation and five patients are living in very good condition with a mean duration of 286 days after OHTX. In our opinion, severe PH is not a contraindication for orthotopic heart transplantation any more. [ABSTRACT FROM AUTHOR]

The major advances in cardiovascular care can be linked to the combined growth of advanced imaging modalities and the variety of treatment options available for patients with complex structural, acquired and congenital, valvular, myocardial and aortic diseases. Paralleling this growth are the number and spectrum of complications - such as device failures and infections - that these patients will inevitably encounter. The keys to successful implementation of advanced cardiac therapy are the real-time images, 3D reconstructions, and the hemodynamic and tissue profiles that can be obtained to evaluate these patients and their devices. We will review the roles of echocardiography, multidetector computed tomography and MRI in the evaluation of normal and abnormal cardiac device function. INSET: Key issues. [ABSTRACT FROM AUTHOR]

Cleveland Clinic's PediPump (Cleveland, OH, USA) is a ventricular assist device designed for the support of pediatric patients. The PediPump is a mixed-flow ventricular assist device with a magnetically suspended impeller measuring 10.5 mm in diameter by 64.5 mm in length. Progress and achievements for the PediPump program are considered according to the development project's three primary objectives: Basic engineering: along with size reductions, substantial design improvements have been incorporated in each design iteration including the motor, magnetic bearings, axial touch points, and heat transfer path; Anatomic modeling and device fitting studies: Techniques based on computed tomography and magnetic resonance imaging have been developed to create three-dimensional anatomic-modeling and device-fitting tools to facilitate device implantation and to assist in preoperative planning. For in vivo testing, to date, six acute (6-h duration) and nine chronic (30-day target duration) implantations have been performed in sheep; the implantation of the PediPump appears to be relatively easy with excellent hemodynamic performance and minimal hemolysis during support. Cleveland Clinic's PediPump program supported by the National Heart, Lung and Blood Institute's Pediatric Circulatory Support Program has led to the development of a pediatric ventricular assist device that has satisfactory performance in preclinical evaluation and appears to be ready to support a program of clinical testing. [ABSTRACT FROM AUTHOR]

Purpose: We describe our experience with ventricular assist devices (VAD) in patients with cardiogenic shock refractory to pharmacological therapy and support using intraaortic balloon pump after cardiac transplantation.Patients: Between July 1987 and August 1997, 848 patients underwent cardiac transplantation in our hospital.Interventions: Fifteen patients (1.8%) needed mechanical circulatory support for refractory cardiac failure due to right heart failure (six patients), primary graft failure (three patients), and acute rejection (six patients). Three pump systems were used: Biomedicus Centrifugal Pump, Abiomed BVS 500, and Thoratec VAD. The choice of system depended on the indication and quality of each device. Seven patients (47%) could be weaned from the mechanical circulatory support (MCS) system and three patients (20%) are long-term survivors.Results: All 15 patients developed at least one serious complication, such as multiorgan failure (MOF), liver failure, acute renal failure or sepsis. Twenty-five per cent had severe bleeding and 13% had neurological complication. Mortality was due mostly to MOF, MOF and sepsis or sepsis. The survivors had a CI greater than 2.2 l.min.m2, total bilirubin less than 1.0 U/1, and did not undergo resuscitation.Conclusions: Heart failure after cardiac transplantation severe enough to require MCS is currently associated with several major complications and high mortality (80%). [ABSTRACT FROM AUTHOR]

Introduction: Assessment of left ventricular (LV) contractility under continuous-flow left ventricular assist device (cfLVAD) support requires information on pump loading conditions. We describe a derivation of completely non-invasive pressure-volume (PV) loops in cfLVAD patients. Methods: Steady state PV loops were derived. Instantaneous left ventricular pressure (LVP) was derived from central aortic pressure+outflow conduit pressure gradient-LVAD pressure head (H). Central aortic pressure was derived from the brachial arterial pressure waveform (Sphygmocor Xcel). H was calculated from pump speed, hematocrit (Hct) and flow(Q). Instantaneous pulsatile conduit pressure losses were calculated from a linear regression model incorporating Q, dQ/dt, conduit diameter, Hct and pump speed developed in a pulsatile mock loop circulation. Instantaneous left ventricular volume (LVV) was calculated as left ventricular end-diastolic volume (LVEDV, derived from simultaneous transthoracic echocardiography) minus the sum of the integral of pump flow with respect to time and the calibrated aortic ejection volume based on aortic valve opening duration. PV loops were derived in HVAD patients following pump speed adjustment (baseline, +200RPM, -200RPM) and bolus intravenous Milrinone to assess changes in loading conditions and contractility respectively. Results: 14 patients were studied (examples in figure 1). Decreased pump speed resulted in significantly higher LV stroke work (0.44±0.20 vs 0.38±0.16J, p=0.03), peak LVP (102±18 vs 95±20mmHg, p=0.03), maximum dP/dt (535±112 vs 487±106mmHg.s-1, p=0.03) and LVEDV (202±83 vs 169±77ml, p=0.0001) compared to increased speed. Milrinone administration significantly reduced LVEDV (175±73 vs 194±80 ml, p<0.0001) and LVEDP (16±9 vs 19±8mmHg, p=0.047), and increased maximum dP/dt (562±112 vs 513±109 mmHg.s-1, p=0.007) and peak LV elastance (0.96±0.55 vs 0.84±0.39 mmHg.ml-1, p=0.03). Invasive mean arterial pressure significantly decreased with both lower pump speed (p<0.0001) and Milrinone (p=0.003). Conclusions: PV loops are able to be derived non-invasively and can detect induced changes in load and contractility. This technique may help in the assessment of LV recovery under cfLVAD support. [ABSTRACT FROM AUTHOR]

Introduction: Acute disturbances in loading conditions under continuous-flow left ventricular assist device (cf-LVAD) support have not been systematically described. We assessed the effect of increased intrathoracic pressure due to forced expiration on pump flow pulsatility and suction events in patients with HeartWare HVAD. Methods: Stable HVAD patients underwent right heart catheterization with simultaneous invasive radial arterial pressure and pump flow recording. Patients performed forced expiration (~40mmHg) with an open glottis at 3 pump speeds (baseline, -200RPM, +200RPM). In addition to standard hemodynamic variables, arterial resistance (mean arterial pressure (MAP) divided by pump flow (Q)) and arterial stiffness (pulse pressure (PP) divided by flow pulsatility) were calculated. The primary outcome was complete loss of pump flow pulsatility during forced expiration. Results: Six of 15 patients (40%) demonstrated complete loss of flow pulsatility during at least 1 expiratory maneuver (figure 1). In univariate analysis, these patients had lower baseline pulmonary arterial wedge pressure (PAWP) (p=0.001), right atrial pressure (RAP) (p=0.019) and mean pulmonary artery pressure (MPAP) (p=0.009) and higher arterial PP (p=0.001). Loss of flow pulsatility was predicted by lower PAWP (p=0.01) and arterial resistance (p=0.004) and higher arterial stiffness (p=0.022) in multiple logistic regression analysis (AUC 0.973, figure 2). Of 24 observed suction events, 19 were preceded by loss of pulsatility (p-value for association <0.0001). Conclusions: In cf-LVAD patients, low preload and arterial resistance and increased arterial stiffness are independently associated with loss of flow pulsatility during forced expiration. This has significant implications for the prevention of suction events and design of automated 'physiological' LVAD controllers. [ABSTRACT FROM AUTHOR]

Abstract: This review broadly covers advances in heart failure, which is responsible for significant morbidity, mortality, and cost in the United States. It is a heterogeneous condition, and accurate classification helps ensure appropriate application of evidence-based therapies. Hemodynamics are important in acute heart failure syndromes and may help tailor therapy. Neurohormonal modulation forms the cornerstone of chronic systolic heart failure treatment but does not affect outcomes in diastolic heart failure where management goals emphasize optimization of central volume, blood pressure, and atrial rhythm, as well as the treatment of comorbidities. Frontiers of heart failure therapy range from advances in pharmacology (novel inotropic agents and neurohormonal modulators), to cell biology (nucleic acid-based drugs and cell therapy) to biomedical engineering (devices such as ultrafiltration, biventricular pacemakers, implantable cardiac defibrillators, remote monitoring systems, and left ventricular assist devices), and to health systems (risk stratification and integrated care of comorbidities). The ultimate frontier will be to integrate these data effectively to ensure that patients with heart failure consistently receive the best evidenced-based care possible. [Copyright &y& Elsevier]