Left ventricular assist device for pediatric postcardiotomy cardiac failure

Children with postcardiotomy heart failure who are unresponsive to maximal medical management have limited options for survival. Short-term mechanical circulatory support, such as with extracorporeal membrane oxygenation and ventricular assist devices, has assumed an expanding role in the care of these patients by providing a bridge to recovery. This report describes the use of left ventricular assist devices with centrifugal pumps in five pediatric cases (weight <15 kg) with postcardiotomy heart failure.     

Left ventricular outflow tract obstruction associated with chronic ventricular assist device support

Favorable long-term patient outcome after insertion of a left ventricular assist device (LVAD) as a bridge to recovery or destination therapy for the treatment of end-stage cardiomyopathy is adversely affected by pathophysiologic changes affecting the heart. Alterations in the native aortic valve apparatus, specifically aortic valve cusp fusion, is an example of such a phenomenon and may especially affect patients in cases of bridge to recovery, a rare but reported event. A retrospective review of the last 33 LVAD placements at our institution was conducted, including reviews of operative reports and pathologic examinations of the native hearts. Seven hearts were found to have varying degrees of aortic valve cusp fusion after chronic LVAD support (63-1, 339 days). Five of these patients had native aortic valves, and two had bioprosthetic valves. The left ventricular outflow tracts in two patients were surgically occluded at the time of LVAD insertion. Aortic valve cusp fusion occurs in roughly 25% of patients on chronic LVAD support. This phenomenon may prove to be clinically significant by creating a potential source of emboli and infection. In addition, in the case of myocardial recovery, left ventricular outflow tract obstruction could limit parallel flow and produce suprasystemic ventricular pressures that in turn would elevate left ventricular end diastolic pressures. The latter may contribute to further myocardial injury, ultimately limiting the ability of an otherwise recovered heart to be weaned from LVAD support.     

Left ventricular heart failure model for testing cardiac assist devices

During the development of a new circulatory support system, we have used different animal models with and without heart failure for hemodynamic testing. As the normally functioning heart does not always allow for proper evaluation of a circulatory support system, a good and adjustable animal heart failure model is needed. The aim of the study was to develop a left ventricular failure model in calves for acute hemodynamic studies. The principle is based on the negative inotropic effect of drugs with bypass of the right ventricle. Seven calves were used in the study. Metoprolol and verapamil were both given intravenously as a bolus, and verapamil was continued as an infusion. The animals were equipped with a VVI pacemaker to treat the expected arteriovenous blockade. A centrifugal pump provided an adjustable flow with a two-stage inflow cannula draining both the upper and lower caval veins and with the outflow cannula in the pulmonary artery. The pump counteracted the effects of right ventricular failure and enabled us to increase the left atrial pressure to more than 20 mm Hg. Pressure in the left atrium rose from 5+/-3 to 25+/-4 mm Hg (p < 0.001), the left ventricular diastolic pressure increased from 2+/-3 to 17+/-7 mm Hg (p = 0.003), and the mean pulmonary pressure increased from 17+/-5 to 33+/-5 mm Hg (p < 0.001). Cardiac output was not significantly changed from 4.0+/-0.8 L/min in the healthy animals to 3.5+/-0.5 L/min (p = 0.25) in failure. The model allowed us to create an adjustable and isolated left ventricular failure well suited for short-term hemodynamic testing of a left ventricular support device.     

Four-year paracorporeal left ventricular assist device (LVAD) support for heart failure after Rastelli operation

It is well known that heart failure can occur after a conventional Rastelli operation (using an anatomical right ventricle as a systemic ventricle) in patients with congenitally corrected transposition of the great arteries (CCTGA). At present, heart transplantation (HTx) is the only definitive therapy known to save such patients. The left ventricular assist device (LVAD) has been employed for patients presenting with acute deterioration of chronic heart failure as a bridge to transplantation when early HTx is not feasible. LVAD implantation in postoperative cases and/or in patients with dextrocardia is often difficult because of the complex anatomy. We report the case of a 26-year-old male patient with CCTGA who presented with heart failure after a conventional Rastelli operation and in whom paracorporeal LVAD implantation was undertaken for the management of right (systemic) ventricular failure. The patient recovered from the heart failure and remained on the HTx list for approximately 4 years with LVAD support.     

Myocardial size and fibrosis changes during left ventricular assist device support

Previous studies have demonstrated that left ventricular assist device (LVAD) implantation significantly decreases myocyte size and reduces fibrosis of the left ventricle (LV). The objectives of the present study were to evaluate LV functional recovery after LVAD implantation and to assess its predictive factors, including histological findings of LV. Six patients with idiopathic cardiomyopathy underwent LVAD support with an EVAHEART implantable centrifugal pump (Sun Medical Technology Research, Nagano, Japan) for an average support duration of 2.91 years. Histologic samples were obtained from their LV apexes at the time of implantation. At 1 month and at 24 months after implantation, brain natriuretic peptide (BNP) and echocardiographic parameters were evaluated. Brain natriuretic peptide values, LV end-diastolic dimension, LV end-systolic dimension, functional shortening, and right ventricular systolic pressure (RVSP) were improved after LVAD implantation. Patients with developing fibrosis had longer durations of heart-failure history and higher pulmonary artery pressures. Patients with hypertrophic myocytes had smaller FS preoperatively. There was a correlation between the amount of fibrosis and the rate of BNP value change after LVAD implantation. In patients with less fibrosis and smaller myocytes preoperatively, improvement in LV function was observed during LVAD support.     

Papillary muscle rupture after myocardial infarction during left ventricular assist device support

We report a rare case of papillary muscle rupture due to myocardial infarction during left ventricular assist device support. A 69-year-old woman with cardiogenic shock due to acute myocardial infarction requiring venoarterial extracorporeal membrane oxygenation support was transferred for further surgical intervention. Six days after the event, extracorporeal membrane oxygenation was decannulated, and an extracorporeal left ventricular assist device was implanted. On postoperative day 11, she suffered from sudden onset hypoxia due to pulmonary edema. Transesophageal echocardiography showed new onset severe mitral regurgitation. No further surgical intervention was performed according to the family’s wishes, and she passed away on the 22nd postoperative day. Autopsy findings revealed papillary muscle rupture. Although the left ventricle is unloaded by the left ventricular assist device, papillary muscle rupture should be recognized as a possible complication after myocardial infarction.     

Left ventricular assist devices as bridge to heart transplantation in congestive heart failure with pulmonary hypertension

Severe pulmonary hypertension (PH) has been considered a significant contraindication to cardiac transplantation. Ongoing clinical experience, however, has shown that temporary support using left ventricular assist devices (LVADs) in these patients can result in significant reductions in PH. A comprehensive review of the available literature regarding the use of LVADs in heart failure patients with PH was conducted. The existing literature to date supports the use of LVADs in heart failure patients with PH and demonstrates that significant reductions in PH in these patients can be achieved. This subsequently allows for safe and effective cardiac transplantation in patients who were previously excluded from this modality. For heart failure patients with severe PH, the use of LVADs can provide significant benefits by significantly reducing PH and allowing subsequent staged transplantation.     

Treatment of acute myocardial infarction with cardiogenic shock using left ventricular assist device

We have treated ten cardiogenic shock patients after acute myocardial infarction (AMI) with a left ventricular assist device (LVAD). These patients were later divided into three groups: the first group with ventricular septal perforation, the second with aorto-coronary bypass grafting (ACBG) before LVAD implantation and the third group without ACBG. LVAD maintained the systemic circulation in each group, and cardiac function recovered enough to remove LVAD in 70% of the total patients. Two of three patients in the first group were discharged from hospital. Two weaned cases in the second group died of multiple organ failure and one was discharged, and hemorrhagic necrosis was seen in the bypassed area of the myocardium. One patient of the third group could not be weaned from LVAD because of respiratory failure though his heart function began to recover. Another case in the third group underwent bypass grafting after removal of LVAD. However ACBG surgery should be done very carefully because a patient in shock is occasionally intolerant to major surgery. In all groups, the major cause of death was multiple organ failure which was probably caused by the prolonged low output condition prior to LVAD application. In the light of this experience, it appears that LVAD should be applied before irreversible damage occurs to major organs, including the heart itself. To ensure the timely application of LVAD, some way must be found to introduce systematic application of LVAD into the normal course of AMI treatment.     

Comparison of observed survival after ventricular assist device placement versus predicted survival without assist device using the Seattle heart failure model

Determining optimal timing for implant of ventricular assist device (VAD) in end-stage heart failure remains a challenge and may be aided by a risk assessment tool. For a cohort of 80 consecutive VAD implants at a single center, observed 1 year survival post-VAD was compared with the estimated survival had these patients not received a VAD, using the Seattle Heart Failure Model (SHFM). The SHFM was adjusted with a hazard ratio of 1.17 for inotrope use (Cochrane Meta-analysis of phosphodiesterase inhibitors) and a hazard ratio of 2.92 for balloon pump, ventilator, or renal replacement therapy (Comparative Outcome and Clinical Profiles in Transplantation [COCPIT] Model). Values immediately before surgery were used to calculate the SHFM score. Point estimates of 1 year survival were compared using Z scores. Mean age was 53 ± 14 (± standard deviation [SD]) years with mean left ventricular ejection fraction of 17 ± 6%. At the time of VAD implant, 92% were on inotropes, 53% had balloon pump, and 15% were intubated. For the entire cohort, 1 year survival without VAD predicted by the SHFM was 47% versus observed survival after VAD of 60% (p = 0.06). The model was most helpful in patients electively implanted with a left ventricular assist device (LVAD). In this group predicted 1 year survival on medical management was 49% versus an observed survival of 82% after LVAD placement (p < 0.05). The model was least helpful in patients undergoing placement of biventricular assist devices (BiVAD), where the model paradoxically predicted better survival with ongoing medical management. This indicated that the model was unable to forecast outcome in patients with higher severity of illness, for example, in cases warranting BiVAD placement. Observed 1 year survival was better with VAD versus that predicted with medical management. Tools such as the SHFM may aid in determining appropriate timing for VAD by providing an estimated survival with ongoing medical management. The model is best applied to more stable patients being considered for elective VAD implantation.     

A novel miniature ventricular assist device for hemodynamic support

The HemoDynamics Systems enabler is a new cardiac assist pump that can expel blood from the left ventricle and provide pulsatile flow in the aorta. We evaluated the efficacy of the 18 Fr enabler. The enabler was inserted from the left ventricular apex into the ascending aorta in eight sheep. Heart failure (mild, moderate, and severe) was induced by microsphere injection into the coronary arteries to reduce cardiac output by 10-30%, 31-50%, and more than 50% from baseline, respectively. The enabler was activated, and its flow was increased to approximately 2.0 L/min. Hemodynamic variables were recorded before and after activation. In moderate heart failure, cardiac output and mean aortic pressure increased from 2.3 +/- 0.6 L/min and 59 +/- 12 mm Hg before assist to 2.8 +/- 0.6 L/min and 70 +/- 8 mm Hg at 30 minutes after activation, respectively (p < 0.01). Left atrial pressure decreased from 17 +/- 3 to 13 +/- 4 mm Hg (p < 0.05). Similar findings were observed in mild and severe heart failure. Despite its small diameter, the enabler significantly improved the hemodynamics of failing hearts and may potentially serve as a means of peripheral left ventricular support. Further study is warranted.     

基于集中参数模型的左心室辅助装置血流动力学仿真

目的新一代植入式心室辅助装置(ventricular assist device,VAD)采用旋转式血泵(rotary blood pumps)技术,目前已成为治疗严重心力衰竭的重要手段,因而研究VAD与人体间的生理相互作用机制有着重要的意义。本研究通过在Matlab Simulink环境中建立人体心血管循环系统的集中参数数学模型,模拟左心衰患者在植入左心室辅助装置(left ventricular assist device,LVAD)后,循环系统的血流动力学特性。方法通过弹性腔和电路原理建立集中参数模型,主要包括心脏、肺循环、体循环、冠状动脉循环。调整模型的输入值使得模型的仿真结果符合设定的目标值。结果仿真结果证实LVAD可以使心衰患者的总心排量恢复正常,同时对于心脏有明显的除负荷效果、增加冠脉血流量并降低肺动脉楔压,因此可以缓解心衰末期患者重要器官供血不足、心肌缺氧以及肺水肿等并发症。同时通过改变左心室辅助装置的转速,末期左心衰患者可以恢复一定的运动能力。结论 CAMSIM集中参数模型符合人体血液循环特点。模型仿真结果证实了LVAD对心衰的辅助作用。     

左室辅助循环对急性左心衰犬肾素血管紧张素系统影响

目的:研究不同辅助流率对急性左心衰时肾素血管紧张素系统(RAS)的影响.方法:对20条急性左心衰犬进行高、中、低流量的180 min左室辅助,观察其对血液动力学及RAS的影响.结果:左室辅助循环可使急性左心衰犬平均左房压、血浆肾素、血管紧张素Ⅱ迅速下降,平均主动脉压、左室搏功指数均升高.结论:不同辅助流量对急性左心衰时左心血液动力学支持均有效,但以中流量效果最佳.神经内分泌因子是评价LVAD效果敏感而有效的指标.     

Granulomatous myocarditis in severe heart failure patients undergoing implantation of a left ventricular assist device

BackgroundGranulomatous myocarditis may develop into cardiomyopathy and severe congestive heart failure that requires implantation of a left ventricular assist device (LVAD).MethodsLeft ventricular (LV) core samples were collected from 177 patients with severe heart failure at the time of LVAD implantation, and samples were histologically examined and graded for severity of hypertrophy and fibrosis. Granulomatous myocarditis incidentally seen in a subset of samples was characterized by staining and culturing for mycobacteria and fungi. Various clinical parameters in these patients were analyzed.ResultsOf the 177 LV core samples examined, 6 (3.4%) showed nonnecrotizing granulomatous inflammation in the myocardial wall. Stains and cultures for mycobacteria and fungi were negative. All six patients [three women, three men; five African American, one Asian; mean age, 52±9 years (range, 41–61 years)] had arrhythmias and required an automatic implantable cardioverter defibrillator. Before LVAD implantation, the patients' mean cardiac index was 1.8±0.4 l/min/m²; cardiac output, 2.9±0.6 l/min; and ejection fraction, 20±2%. One year after LVAD implantation, one patient had undergone heart transplantation. At 2 years, a second patient was transplanted, and one died. At 3 years, a third patient was transplanted and died postoperatively; two patients remained on support. No clinical evidence indicated involvement of other organs or recurrence in the transplanted patients.ConclusionThe incidental diagnosis of granulomatous myocarditis in our patients indicates that histological study of LV core samples in patients who undergo LVAD implantation may contribute to the diagnosis and be a consideration in the management of the underlying cause of heart failure.