The use of muscle flaps to treat left ventricular assist device infections

Left ventricular assist devices have become an important adjunct in the therapeutic armamentarium for patients with end-stage heart failure. Although they may provide a bridge to transplantation, they are prone to certain problems, expecially infection. Because these are life-sustaining devices, changing the device or simple explantation may be a risky, if not impossible, option. Therefore, we evaluated the effectiveness of a surgical alternative, namely, coverage of infected devices with muscle or myocutaneous flaps. Eighty-two consecutive patients who underwent the insertion of 88 left ventricular assist devices at our institution over a 6.5-year period were evaluated. Follow-up was provided for all patients and ranged from 1 to 7.5 years. The duration of ventricular support ranged from 0 to 434 days. All patients who demonstrated clinical evidence of infection were identified. Overall, 54 patients (66 percent) had infections locally at the device site, at distant sites, or systemically during support. Cultured organisms included gram-positive and -negative bacteria, fungi, and viruses. Of the 56 infections in these 54 patients, 21 (38 percent) were device-related, i.e., in the pocket created by the device, in the device itself, or from the driveline. Thus, 24 percent (21 of 88) of all ventricular support devices inserted demonstrated device infection during use. Therapeutic modalities used to combat device-related infection included both nonsurgical management with antibiotics alone and surgical procedures such as device change or relocation, device explant, and flap coverage. Eight of the 20 patients in whom the 21 device-related infections occurred underwent surgical intervention. Four of these eight patients undenwent local flap coverage of their infected left ventricular assist devices. All four patients also had evidence of systemic infection, or "device endocarditis." Coverage was successfully achieved in all cases with pedicled rectus abdominis flaps. There were no perioperative complications. Two patients later underwent successful transplantation; the other two died from causes unrelated to the flap. In conclusion, the treatment of infected left ventricular assist devices currently includes both nonsurgical and surgical alternatives. Of the latter, muscle flaps should be considered a first-line intervention to assist in eradicating infection by providing well-vascularized tissue. Although there were no perioperative complications, the 50 percent mortality rate is consistent with that reported for patients with "device endocarditis." It may be that flap coverage of infected ventricular assist devices, if instituted at an earlier stage in the therapeutic process, could help prevent systemic infection in these patients and, therefore, improve their overall outcome.     

CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT

An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.     

Marshall to the rescue in cardiac resynchronization therapy: Left ventricular lead placement in coronary sinus ostial atresia

This case highlights the importance of proper identification of congenital anomalies of the coronary sinus for the successful placement of left ventricular lead during cardiac resynchronization therapy device implantation. We discuss an alternate route for left ventricular lead placement via the vein of Marshall when the coronary sinus ostium in the right atrium was atretic and was facing difficulty initially in detecting the anomaly.     

左心室脱血回注循环辅助法对急性心肌梗死血流动力学的改善作用

目的:实验观察左心室脱血回注循环辅助法对急性心肌梗死血流动力学的改善作用.方法:18只杂种犬分两组制作急性心肌梗死泵衰竭模型,治疗组给予左心室脱血回注循环辅助,对照组不进行治疗.观察比较两组间心律失常、死亡率、外周动脉压、肺动脉毛细血管楔嵌压(PCWP)、左心室舒张末期压(LVEDP)、左心室内径的变化.结果:治疗组室性期外收缩、心室纤颤发生率和死亡率显著低于对照组;对照组的外周动脉收缩压低于80 mmHg以下,治疗组维持在100mmHg以上(P＜0.01);治疗组PCWP和LVEDP值在45 min以后的各时段低于对照组(P＜0.01);治疗组的左室舒张末期内径小于对照组(P＜0.01).结论:左心室脱血回注循环辅助法能够减少急性心肌梗死泵衰竭的心室纤颤发生率和死亡率,有显著改善血流动力学、防止梗死后心肌扩张和有效的左心室辅助作用.     

The Role of 1.5 Tesla MRI and Anesthetic Regimen Concerning Cardiac Analysis in Mice with Cardiomyopathy

Accurate assessment of left ventricular function in rodent models is essential for the evaluation of new therapeutic approaches for cardiac diseases. In our study, we provide new insights regarding the role of a 1.5 Tesla (T) magnetic resonance imaging (MRI) device and different anesthetic regimens on data validity. As dedicated small animal MRI and echocardiographic devices are not broadly available, we evaluated whether monitoring cardiac function in small rodents with a clinical 1.5 T MRI device is feasible. On a clinical electrocardiogram (ECG) synchronized 1.5 T MRI scanner we therefore studied cardiac function parameters of mice with chronic virus-induced cardiomyopathy. Thus, reduced left ventricular ejection fraction (LVEF) could be verified compared to healthy controls. However, our results showed a high variability. First, anesthesia with medetomidine, midazolam and fentanyl (MMF) led to depressed cardiac function parameters and more variability than isoflurane gas inhalation anesthesia, especially at high concentrations. Furthermore, calculation of an average ejection fraction value from sequenced scans significantly reduced the variance of the results. To sum up, we introduce the clinical 1.5 T MRI device as a new tool for effective analysis of left ventricular function in mice with cardiomyopathy. Besides, we suggest isoflurane gas inhalation anesthesia at high concentrations for variance reduction and recommend calculation of an average ejection fraction value from multiple sequenced MRI scans to provide valid data and a solid basis for further clinical testing.     

Simulation of Dilated Heart Failure with Continuous Flow Circulatory Support

Lumped parameter models have been employed for decades to simulate important hemodynamic couplings between a left ventricular assist device (LVAD) and the native circulation. However, these studies seldom consider the pathological descending limb of the Frank-Starling response of the overloaded ventricle. This study introduces a dilated heart failure model featuring a unimodal end systolic pressure-volume relationship (ESPVR) to address this critical shortcoming. The resulting hemodynamic response to mechanical circulatory support are illustrated through numerical simulations of a rotodynamic, continuous flow ventricular assist device (cfVAD) coupled to systemic and pulmonary circulations with baroreflex control. The model further incorporated septal interaction to capture the influence of left ventricular (LV) unloading on right ventricular function. Four heart failure conditions were simulated (LV and bi-ventricular failure with/without pulmonary hypertension) in addition to normal baseline. Several metrics of LV function, including cardiac output and stroke work, exhibited a unimodal response whereby initial unloading improved function, and further unloading depleted preload reserve thereby reducing ventricular output. The concept of extremal loading was introduced to reflect the loading condition in which the intrinsic LV stroke work is maximized. Simulation of bi-ventricular failure with pulmonary hypertension revealed inadequacy of LV support alone. These simulations motivate the implementation of an extremum tracking feedback controller to potentially optimize ventricular recovery.     

The technological imperative and the battle for the hearts of America

The left ventricular assist device is an expensive, invasive technological approach to advanced heart failure, a condition affecting 5 million Americans, principally the elderly. Given that technology is the leading cause of escalating health care costs, an understanding of the diffusion process of new technology is essential. This case study of the left ventricular assist device (LVAD), while demonstrating the interaction of science, industry, politics, and economics in health care, suggests there are three critical points in the life cycle of a new technology. In the innovation phase, research support by the National Institutes of Health is critical. In the adoption phase, the crucial lever is the decision by the Medicare program to reimburse for the proposed new technology. Finally, in the dissemination phase, regular reevaluation of technology is essential.     

Haemodynamic efficacy of microaxial left ventricular assist device in cardiogenic shock: a systematic review and meta-analysis

Netherlands Heart Journal - The Impella percutaneous mechanical circulatory support device is designed to augment cardiac output and reduce left ventricular wall stress and aims to improve survival...     

Insertion of the Impella 5.0 left ventricular assist device via right anterior mini-thoracotomy: a novel practical approach

The Impella 5.0 microaxial pump is a miniaturized left ventricular assist device commonly used for circulatory support in acute cardiogenic shock. The catheter-based pump is designed to be inserted either into a peripheral artery or directly into the ascending aorta. We report the first case in which the Impella 5.0 device was placed directly into the ascending aorta via a small right anterior thoracotomy in a patient following acute myocardial infarction complicated by cardiogenic shock.     

Initial experience with a new blood pump

A new type of blood pump was tested in calves for 6 hours. The pump consists of a rigid housing with a trochoidal internal surface, an inlet and outlet, and two lateral walls. A two-corner piston rotating on an eccentric shaft, describes a trochoidal path, thus creating a gap seal, the gap measuring a constant 10-35 microns. The pump is driven by a watercooled DC motor. For right ventricular assist, a cannula is inserted into the right ventricle through the right atrium, and into the left ventricle for left ventricular assists. From a total of 10 experiments, two left ventricular assists, two right ventricular assists, and three biventricular assists were evaluated. The pump produced a pulsatile flow of 31 at 70 rpm. Energy requirements were 2.19 watts for left, 2.06 for right, and 7.26 for biventricular assists. Plasma hemoglobin remained as low as 10 mg/dl during monoventricular, and increased during biventricular assists to 20 mg/dl after 3 hours, and returned to 16 mg/dl after 6 hours. From these preliminary results it is concluded that this new rotary blood pump may be suitable as a circulatory assist device.     

PREFABRICATION DESIGN CONSIDERATIONS FOR A LONG-TERM ELECTRICALLY-ACTUATED ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (E-TYPE ALVAD)

The conceptual design and development of a long-term, low-profile intracorporeal left ventricular assist device is a multifaceted project involving a series of technical, anatomic and physiologic considerations. Patients with severe left ventricular failure refractory to all other forms of therapy could benefit from such a device. Prior to fabrication of such a blood pump, consideration must be given to physiologic parameters of the projected patient population. The pump must be designed to meet physiologic demands and yet conform to the anatomic constraints posed by the patient population. We measured the body surface area (BSA) of a group of patients (n=50) and found the mean BSA for this group to be 1.804 +/- 0.161 m(2). Using 25 ml/m(2) as a stroke volume index indicative of left ventricular failure and a stroke volume index of 45 ml/m(2) as normal, distributions of stroke volumes (normal and in left ventricular failure) were plotted for a potential population and demonstrated that 63% of the projected population can be returned to normal by a pump with a stroke volume >/= 83 ml. Cadaver fitting studies established that 73% of the potential population can accommodate an ALVAD 10.8 cm in diameter. In-vitro tests demonstrated that a pump stroke volume >/= 83 ml could be achieved by the proposed pump with a 15 mmHg filling pressure at rates up to 125 B/min. A pusher-plate stroke of 0.56 inches would be necessary to provide a stroke volume >/= 83 ml. The percent of the patient population that could be served was determined by excluding those in whom the pump would not fit or in whom it would provide less than a normal resting stroke volume. Approximately 73% of the projected patient population would accommodate this pump and be returned to normal circulatory dynamics.     

ULTRASTRUCTURAL ANALYSES OF STONE HEART SYNDROME AT ONSET AND SIX DAYS LATER FOLLOWING TOTAL SUPPORT OF THE CIRCULATION WITH A PARTIAL ARTIFICIAL HEART OR LEFT VENTRICULAR ASSIST DEVICE (ALVAD)

Ischemic myocardial contracture developed in a 21-year-old man following aortic and mitral valve replacement. The patient's circulation was supported totally for 6 days with an abdominal left ventricular assist device (ALVAD). Cardiac allografting was then undertaken. Samples of myocardium taken at the original operation and 6 days later at transplantation were analyzed ultrastructurally. At the onset of ischemic cortracture, left ventricular abnormalities included hypercontraction of myofibrils, loss of normal A-band and Z-band patterns, mitochondrial swelling with fusion of cristae, interfibrillar edema and glycogen depletion. Capillaries demonstrated swelling of endothelial cells and basement membrane disruption. Six days later, ultrastructural morphology showed further degeneration. The myofibrils remained hypercontracted, but were more fragmented. Degenerative changes in mitochondria were more advanced and calcium deposition in cristae was present. No glycogen was seen. The right ventricular myocardium exhibited significantly fewer ultrastructural abnormalities. The principal right ventricular changes were endothelial swelling and basement membrane disruption. Glycogen granules were present. Ischemic contracture affects the left ventricle more than the right, and the morphology becomes more abnormal with time. To our knowledge, this is the first instance wherein morphologic progressions of the ultrastructural alterations of ischemic contracture have been documented.     

Mechanically induced electrical storm as a complication of cardiac resynchronization therapy: A case report

BackgroundCardiac resynchronization therapy (CRT) has been shown to improve both the functional status and mortality of heart failure patients with left bundle branch block. Multiple recent studies suggest several mechanisms for proarrhythmia associated with CRT device.Case summaryA 51-year-old male with symptomatic non-ischemic cardiomyopathy and no previous history of ventricular arrhythmias underwent placement of a biventricular cardioverter-defibrillator. The patient developed sustained monomorphic ventricular tachycardia (VT) soon after implantation. The VT recurred despite reprogramming to right ventricular only pacing. The electrical storm resolved only after a subsequent discharge from the defibrillator caused inadvertent dislodgement of the coronary sinus lead. No recurrent VT occurred throughout 10-years follow up after urgent coronary sinus lead revision.DiscussionWe describe the first reported case of mechanically induced electrical storm due to the physical presence of the CS lead in a patient with a new CRT-D device. It is important to recognize mechanical proarrhythmia as a potential mechanism of electrical storm, as it may be intractable to device reprogramming. Urgent coronary sinus lead revision should be considered. Further studies on this mechanism of proarrhythmia are needed.     

Atrial pacing, the forgotten pacing mode

In patients with sick sinus syndrome and normal atrioventricular conduction, physiological pacing can be accomplished with either a single chamber atrial pacemaker AAI/R or a dual chamber pacemaker DDD/R. The single chamber device has the advantages of simpler implantation and lower initial costs, while the dual chamber device offers protection in case atrioventricular conduction disturbances develop in the future. When rigorous attention is paid to the pre-implantation selection criteria, the incidence of reported second- or third-degree atrioventricular block varied between 0.4 and 1.8% per annum. Medical practice, however, has shifted to predominant implantation of DDD/R pacemakers in more than 95% of patients with sick sinus syndrome. Recent publications have reported an increase in left atrial diameter, decrease in left ventricular fractional shortening and increased incidence of atrial fibrillation in patients with DDD/R pacing as compared with patients with single chamber atrial devices. These changes were proportional to the percentage of ventricular paced beats. New algorithms in dual chamber devices have been developed in order to minimise ventricular stimulation. These are being evaluated at present. In my opinion there is still a place for atrial pacing in selected patients with sick sinus syndrome with a minimum risk of developing complete atrioventricular block. (Neth Heart J 2008;16(suppl 1): S25-S27.)     

一组有或无基因突变的特发性扩张型心肌病患者临床发病及预后的分析

目的:分析携带基因突变和未携带基因突变的特发性扩张型心肌病(IDCM)患者的临床发病及预后的差异性。方法:收集2011年01月-2014年09月于南京鼓楼医院就诊的IDCM患者115例,经靶向二代测序鉴定后分为基因突变组和未突变组,出院后对两组患者进行定期随访,将两组患者的临床资料及随访结果进行统计学分析。结果:两组患者的一般临床特征(如性别比例、首发症状年龄、血压、糖尿病比例等)无显著差异(P0.05);辅助检查特征(如左室射血分数、左室舒张末内径、室壁厚度、QRS-T夹角和血肌酐水平等)无显著差异(P0.05);治疗情况(如药物和器械治疗)无差异(P0.05);随访资料(如再入院和生存分析)亦无统计学差异(P0.05,Log rank P=0.12);将性别比例、是否吸烟、是否合并糖尿病、是否植入器械、是否发生突变等临床参数进行Cox回归分析,发现上述参数未影响患者的临床预后(P0.05)。结论:本组资料显示携带基因突变的IDCM患者临床发病及预后较未携带突变者无显著差异。     

Dynamic optimization of in-series cardiac assistance by means of intra-aortic balloon pumping

Analytical techniques are developed which permit objective control of asiist device driving systems. In addition to being objective, the techniques described in this paper are optimal in the sense of minimizing a performance index which consists of a term involving left ventricular power and a term involving deviations of aorta hemodynamic parameters from normal values. Comparisons are included of off-line computations and measurements on dogs with experimentally induced myocardial infarctions undergoing intraaortic balloon pumping.     

可植入式心室辅助装置动物模型的建立

目的探讨建立可植入式心室辅助装置研究的实验动物模型。方法选取体质量120-180 kg小公牛7只,常规全麻后左侧第4肋间开胸,建立体外循环,体外循环辅助下诱颤后,植入自主研发的国产可植入式心室辅助装置（DIVAD,domestic-made implantable ventricular assist device）,DIVAD机械性能参数接近国际同类产品,泵尺寸29.5mm×72 mm,重量158 g,体外转速可达9000 r/min,流量可达8 L/min,整合流量计,并可通过体外控制器监测控制。DIVAD连接左室及降主动脉,转速3500-8000 r/min左右,行左室辅助。术后撤除体外循环,持续监测动物生命体征及DIVAD运转情况。肝素静滴维持ACT在正常值1.5-2倍之间。结果7只小牛术后全部复跳,均能成功撤离体外循环辅助,最长存活时间超过93 h,最短存活时间0.5 h,平均存活时间20.28 h。结论小牛可以作为DIVAD研究的合适动物模型,其围手术期处理有相应特点,小牛DIVAD实验模型的建立对于进一步研究改进DIVAD有重要作用。     

Characteristics of cardiac device infections in the Isala Hospital; a large volume tertiary care cardiology centre

Aims

To determine the frequency, characteristics and risk factors of cardiac device infections in the Isala Hospital.

Methods

We retrospectively studied all patients who underwent cardiac device procedures performed in the cardiac catheterisation lab and the operating room from 2010 to 2012. All patients who developed a cardiac device infection were reviewed for its characteristics.

Results

31/2026 patients developed a cardiac device infection (1.5 %). One (3.2 %) patient died within 30 days of hospitalisation. Device infection rates for procedures in the catheterisation lab and operating room were similar (p = 0.60). Positive cultures were present in 27/31 (87 %) cases. These consisted predominantly of micro-organisms that are part of the skin flora (84 %). The mean time between device procedure and infection was 14 ± 21 months (range 0–79). Cardiac device infection was significantly associated with device revision, (65 % were revisions in patients with device infection vs. 30 % revisions in patients without device infection, p = 0.011) and placement of a left ventricular lead in pacemaker implantations (59 % of patients with vs. 51 % of patients without device infection, p < 0.001).

Conclusion

The frequency of cardiac device infection was 1.5 % with a mortality of 3.2 % within 30 days, which is lower compared with other registries. Cardiac device infections were associated with device revisions and placement of left ventricular leads in pacemaker implantations.     

AN INTRACORPOREAL (ABDOMINAL) LEFT VENTRICULAR ASSIST DEVICE [ALVAD], XXX: CLINICAL READINESS AND INITIAL TRIALS IN MAN

The purpose of this report is to present documenting evidence of the clinical readiness of an abdominal left ventricular assist device (ALVAD) according to NHLI criteria,( double dagger ) and the initiation of clinical trials of this device in otherwise irretrievable adult post-cardiotomy patients at the Texas Heart Institute of St. Luke's Episcopal and Texas Children's Hospitals. The ALVAD system has been developed, modified, and improved under NHLI auspices over the last eight years,( double dagger double dagger ) with annual reviews. Over 20,000 hours of in-vivo testing in the calf have been accomplished in our laboratories. The current clinical trials underwent two federal reviews (May 22, 1973 and October 17, 1974) and were the topic of an Ad Hoc Workshop at NHLI on October 28, 1973.( double dagger double dagger double dagger ) More recently, a consecutive series of 26 bovine ALVAD implantations were undertaken; acute and chronic hemodynamic effectiveness with maintenance or augmentation of the systemic circulation during profound ventricular unloading without undue blood trauma, intra-or extra-prosthetic thrombosis, or sepsis was demonstrated; no biomaterials problems were encountered. In-vivo realibility and durability, histologic and pathologic results were detailed, summarized, and submitted to NHLI. Patient acceptability surveys and geometric and volumetric human configuration studies were analyzed. Categorizations of the patients at risk in our institutions and the needs for such a device were documented. The periods of intended use (two weeks-one month), weaning procedures, and the possibility of pump dependence have been discussed. The legal, moral, ethical and informed consent issues were addressed. Clinical protocols (anesthesia, surgical, cardiologic, hematologic, engineering, computerized data-acquisition, follow-up) and cost analyses were developed. The device has now been used in four terminal patients since December, 1975; all subsequently succumbed, but their circulations were temporarily supported during total left ventricular unloading for periods up to eight hours. Continued systematic, controlled clinical investigations of this nature are warranted. A comprehensive listing of pertinent references is included.