Pulmonary hypertension is not a risk factor for RVAD use and death after left ventricular assist system support

Unlike transplantation candidates, patients with pulmonary hypertension (PHTN) and a high transpulmonary gradient do not appear to be at increased risk for right ventricular dysfunction after left ventricular assist system implant. To verify this observation, we reviewed 63 patients supported with the HeartMate (Thermo Cardiosystems, Inc, Woburn, MA) left ventricular assist system. Patients were divided into two groups: patients with PHTN (47 patients) had mean pulmonary artery pressure > 30 mm Hg and/or pulmonary vascular resistance > 4 Wood units, and the remainder of patients did not have PHTN (16 patients). Both groups were similar in age (mean, 51 years), gender distribution (% men, 83% vs 94%, not significant), and number of patients with ischemic cardiomyopathy (72% vs 69%, not significant). More patients in the group without PHTN required extracorporeal membrane oxygenation support (38% vs 12%, p = .06). Right ventricular assist device support was instituted in five (11%) patients with PHTN and four (25%) patients without PHTN. A significantly larger number of patients without PHTN died while on support (14% vs 44%, p = .01). Survival after transplantation in both groups was > 90%. Patients with PHTN have higher transpulmonary gradient, show a significant decrease in pulmonary pressure after left ventricular assist system implantation, and have a higher transplantation rate compared to patients without PHTN. A larger patient cohort is needed to determine if the absence of PHTN is a risk factor for RVAD need and poor outcome after LVAS support.     

Extracorporeal life support as a post left ventricular assist device implant supplement

Extracorporeal life support (ECLS) is indicated following left ventricular assist device (LVAD) implant for right heart failure or pulmonary dysfunction. From December 1991 to December 1996, 100 patients were supported with the implantable HeartMate LVAD. Of these, 12 patients were supported with ECLS post LVAD implant. Pre-operatively, 10 patients (83%) were on an intra-aortic balloon pump, 9 patients (75%) were intubated, and 8 patients (67%) required ECLS bridge to LVAD implant. Six patients (50%) were men, and patient age ranged from 28 to 63 years (mean 46 +/- 10 years). Duration of ECLS averaged 3 +/- 2 days (range, 1-9 days). Eight patients (67%) required a right ventricular assist device (RVAD) with an ECLS circuit, three patients (25%) required peripheral veno-venous ECLS, and one patient peripheral veno-arterial ECLS. Forty-five percent supported with ECLS post LVAD survived to transplant compared with the 81% supported with LVAD only. Early in this experience, three patients had RVAD support only and all three patients died. RVAD support (with or without ECLS) was 11% overall and declined from 14% in the first 50 patients to 8% in the second 50. ECLS post LVAD is relatively uncommon and its use is associated with reduced survival, but helps salvage these critically ill patients.     

Venovenous extracorporeal life support for patients after cardiotomy

Pulmonary edema and acute lung injury are common sequelae after cardiopulmonary bypass. Increased ventilatory support improves gas exchange, but may compromise ventricular function. From July 1994 to February 1997, nine patients were supported with veno-venous (V-V) extracorporeal life support (ECLS) for post cardiotomy respiratory failure. The mean age was 53 +/- 13 years (range: 37-80 years), and eight (89%) were men. Pre-operatively, five of nine (56%) were intubated, three (33%) were supported with an intra-aortic balloon pump, and five (56%) were on veno-arterial ECLS. Four patients were post left ventricular assist device (LVAD) implantation, one each after resection of an aortic aneurysm, mitral valve replacement and bypass grafting, aortic valve replacement, and pulmonary embolectomy and heart transplantation. Mean duration of support was 2 +/- 1 days (range: 1-4 days). Patients were intubated for a mean of 2 +/- 22 days (range: 4-71 days). One patient (11%) required mediastinal re-exploration secondary to bleeding, two patients underwent hemodialysis or ultrafiltration, and seven (77%) developed bacterial pneumonia. All patients were weaned from ECLS. Six patients (67%) survived to hospital discharge. Cause of death was multiple organ failure in two patients; one died from respiratory failure. V-V ECLS is a useful alternative to open sternotomy for ventilatory induced hemodynamic compromise post cardiotomy, especially in patients with LVADs.     

Epitope mapping of monoclonal antibodies against 4-aminobenzoate hydroxylase from Agaricus bisporus

BACKGROUND: Left ventricular assist devices have been reported previously to reverse ventricular remodeling in patients with dilated cardiomyopathy. In patients with prolonged mechanical support, structural failure of the left ventricular assist device inflow valve can cause regurgitation into the left ventricle, which may affect adversely this process. METHODS: Left ventricular end-diastolic pressure-volume relation of hearts explanted from 8 patients with left ventricular assist device and 8 control subjects with idiopathic cardiomyopathy was determined ex vivo at the time of transplantation. RESULTS: Duration of mechanical support ranged from 210 to 276 days (mean +/- standard deviation = 283 +/- 76 days) in 3 patients with inflow valve regurgitation versus 100 to 155 days (132 +/- 22 days) in 5 patients without (p = 0.005). The end-diastolic pressure-volume relation of all hearts supported mechanically was shifted to the left toward normal controls. This effect was markedly attenuated in patients with inflow valve regurgitation. CONCLUSIONS: Mechanical assistance can cause reverse remodeling in patients with dilated cardiomyopathy as evidenced by the shift in the end-diastolic pressure-volume relation curve to the left. Inflow valve failure, associated with prolonged support, can attenuate changes in left ventricular structure and dimension. Ineffective pressure and volume unloading may explain these observations.     

Use of the Nippon-Zeon pneumatic ventricular assist device as a bridge to cardiac transplantation

The Nippon-Zeon (NZ) ventricular assist device is a sac type, air driven, heterotopic, external pump. Its performance has been evaluated in Japan as a bridge to myocardial recovery. Few data are available on the device as a bridge to heart transplantation. Since 1991, 10 patients (9 men) were bridged to heart transplantation with NZ, all in biventricular support. The mean age was 39 +/- 13 years (range, 21-60 years), mean body weight was 75 +/- 13 kg (range, 51-95 kg). Five patients had a dilated cardiopathy, and five were ischemic (three acute myocardial infarctions). Despite maximal inotropic support, including enoximone in seven, epinephrine in three, and intraaortic balloon pumping in one, eight patients were anuric, three were in acute hepatic failure, and three were intubated. Preoperative hemodynamic and biologic values were: cardiac index, 1.57 +/- 0.4 l/min/m2; pulmonary capillary wedge pressure, 34 +/- 5 mmHg; creatinine, 200 +/- 80 mumol/l; blood urea nitrogen, 17.5 +/- 8 mmol/l; total bilirubin 36 +/- 6 mumol/l; aspartate aminotransferase, 1,000 +/- 2,000 IU/l. In all patients, a biventricular assist device was implanted without the use of cardiopulmonary bypass. Improvement occurred immediately in all but one. Mean left ventricular flow was 4.5 +/- 0.8 l/min. Anticoagulation was maintained with intravenous heparin. Recently for bleeding was required in one case (10%), and two patients had positive blood cultures that were successfully treated. There was no mechanical failure. Hemolysis was not significant (lactate dehydrogenase, 378 +/- 50 IU/l; plasma-free hemoglobin below 10 mg/dl). Each device was free of thrombi and deposits at time of explantation. One patient died while on assist. Nine patients (90%) were transplanted after 11 +/- 8 days (range, 1-32 days). Three died early after transplantation, one of graft failure, two of sepsis. Six patients (66%) could be discharged. The follow-up ranges from 7 to 28 months. NZ is a simple, reliable, pneumatic device driven by a light, silent console; it can be rapidly implanted without cardiopulmonary bypass in patients in desperate condition who are awaiting cardiac transplantation. The difficulty of patient rehabilitation while using this device should limit the duration of support to weeks to allow the patient to be in optimal condition for heart transplantation.     

First use of an untethered, vented electric left ventricular assist device for long-term support

This report describes the first long-term (505-day) application of the vented electric (VE) HeartMate left ventricular assist device (LVAD) (Thermo Cardiosystems, Inc). The device consists of an abdominally placed, battery-powered titanium blood pump that, in contrast to earlier pneumatically powered systems, allows patients untethered freedom of movement. The batteries last 5 to 8 hours and can be changed on a rotating basis indefinitely. The patient, a 33-year-old man (90 kg, blood type O) with idiopathic cardiomyopathy, experienced end-organ heart failure (New York Heart Association [NYHA] class IV) while he was awaiting heart transplantation. When his hemodynamic criteria met those outlined in the protocol, we implanted the VE-LVAD as a bridge to transplantation. The patient was supported by the device for more than 16 months. His cardiac status returned to NYHA class I, and he was eventually allowed to take day trips outside the hospital as he awaited transplantation. The VE-LVAD enabled the patient to participate in activities such as eating in restaurants, going to movies, and practicing basketball shots. Unfortunately, the patient died suddenly due to a neurological thromboembolic event that occurred on day 503 of VE-LVAD support. The VE-LVAD improved native left ventricular function by chronic unloading, and ventricular remodeling resulted in a more normal configuration anatomically, physiologically, and ultimately, histologically and pathologically.     

Evaluation of a pulsatile pediatric ventricular assist device in an acute right heart failure model

BACKGROUND: The development of pulsatile ventricular assist devices for children has been limited mainly by size constraints. The purpose of this study was to evaluate the MEDOS trileaflet-valved, pulsatile, pediatric right ventricular assist device (stroke volume = 9 mL) in a neonatal lamb model of acute right ventricular failure. METHODS: Right ventricular failure was induced in ten 3-week-old lambs (8.6 kg) by right ventriculotomy and disruption of the tricuspid valve. Control group 1 (n = 5) had no mechanical support whereas experimental group 2 (n = 5) had right ventricular assist device support for 6 hours. The following hemodynamic parameters were measured in all animals: heart rate and right atrial, pulmonary arterial, left atrial, and systemic arterial pressures. Cardiac output was measured by an electromagnetic flow probe placed on the pulmonary artery. RESULTS: All results are expressed as mean +/- standard deviation and analyzed by Student's t test. A p value less than 0.05 was considered statistically significant. Base-line measurements were not significantly different between groups and included systemic arterial pressure, 80.6 +/- 12.7 mm Hg; right atrial pressure, 4.6 +/- 1.6 mm Hg; mean pulmonary arterial pressure, 15.6 +/- 4.2 mm Hg; left atrial pressure, 4.8 +/- 0.8 mm Hg; and cardiac output, 1.4 +/- 0.2 L/min. Right ventricular injury produced hemodynamics compatible with right ventricular failure in both groups: mean systemic arterial pressure, 38.8 +/- 10.4 mm Hg; right atrial pressure, 16.8 +/- 2.3 mm Hg; left atrial pressure, 1.4 +/- 0.5 mm Hg; and cardiac output, 0.6 +/- 0.1 L/min. All group 1 animals died at a mean of 71.4 +/- 9.4 minutes after the operation. All group 2 animals survived the duration of study. Hemodynamic parameters were recorded at 2, 4, and 6 hours on and off pump, and were significantly improved at all time points: mean systemic arterial pressure, 68.0 +/- 13.0 mm Hg; right atrial pressure, 8.2 +/- 2.3 mm Hg; left atrial pressure, 6.4 +/- 2.1 mm Hg; and cardiac output, 1.0 +/- 0.2 L/min. CONCLUSIONS: The results demonstrate the successful creation of a right ventricular failure model and its salvage by a miniaturized, pulsatile right ventricular assist device. The small size of this device makes its use possible even in small neonates.     

Influence of inhaled nitric oxide on systemic flow and ventricular filling pressure in patients receiving mechanical circulatory assistance

BACKGROUND: In patients with left ventricular (LV) dysfunction, inhaled nitric oxide (NO) decreases pulmonary vascular resistance (PVR) but causes a potentially clinically significant increase in left atrial pressure (LAP). This has led to the suggestion that inhaled NO may reach the coronary circulation and have a negative inotropic effect. This study tested an alternative hypothesis that LAP increases because of volume shifts to the pulmonary venous compartment caused by NO-induced selective pulmonary vasodilation. METHODS AND RESULTS: The Thermo Cardiosystems Heartmate is an LV assist device (LVAD) that can be set (by controlling pump rate) to deliver fixed or variable systemic blood flow. Eight patients (between 1 and 11 days after LVAD implantation) were administered inhaled NO (20 and 40 ppm for 10 minutes), and LAP, systemic flow, and pulmonary arterial pressure were measured in both fixed and variable pump flow modes. In both modes, inhaled NO lowered PVR (by 25 +/- 6% in the fixed mode, P < .001, and by 21 +/- 5% in the variable mode, P < .003). With fixed pump flow, LAP rose from 12.5 +/- 1.2 to 15.1 +/- 1.4 mm Hg (P < .008). In the variable flow mode, LAP did not increase and the assist device output rose from 5.3 +/- 0.3 to 5.7 +/- 0.3 L/min (P < .008). CONCLUSIONS: A selective reduction in PVR by inhaled NO can increase LAP if systemic flow cannot increase. These data support the hypothesis that with LV failure, inhaled NO increases LAP by increasing pulmonary venous volume and demonstrate that inhaled NO has beneficial hemodynamic effects in LVAD patients.     

Temporary mechanical left heart support. Recovery of heart function in patients with end-stage idiopathic dilated cardiomyopathy

BACKGROUND: Implantation of a mechanical cardiac support system (MCSS) in patients with idiopathic dilated cardiomyopathy (IDC) may improve cardiac function and allow explantation of the device. Our experience now includes 13 patients who have been "weaned" from MCSS and we report about the overall results of this treatment as well as the effects of ventricular unloading on cardiac function, anti-beta 1-adrenoceptor-autoantibody (A-beta 1-AAB) level and the degree of myocardial fibrosis. METHODS: 13 patients with non-ischemic IDC who had been admitted here in cardiogenic shock (CI < 1.61.min-1.m2, left ventricular ejection fraction [LVEF] < 16% and left ventricular internal diameter in diastole [LVIDd] > 68 mm) and who all tested positive for A-beta 1-AABs were implanted with an uni-(12 patients) or a biventricular (1 patient) mechanical assist device. Echocardiographic evaluation and A-beta 1-AAB-level-monitoring was routinely performed after implantation and explantation of the MCSS and the degree of myocardial fibrosis was assessed at the time of implantation and after explantation. RESULTS: During a mean duration of mechanical support of 236 +/- 201 days (range: 30 to 794 days), LV-EF improved to a mean of 46% and LVIDd decreased to a mean value of 56 mm in these 13 patients. A-beta 1-AABs decreased and disappeared 11.7 weeks after implantation of the device and did not reincrease thereafter. The highly pathologic degree of fibrosis at the time of implantation diminished to normal values about 1 year after explantation. One patient died of anesthesiologic complications and another patient shortly presented with a new episode of cardiac insufficiency 6 months after explantation. He was implanted again with an univentricular assist device was successfully transplanted 3 weeks later. Mean observation period of the remaining 11 patients now amounts to 12.6 +/- 9.77 (range: 3 to 26) months after explantation of the device--as of May, 31, 1997--with a cumulative observation period of 139 patient months. CONCLUSION: Temporary implantation of a MCSS may normalize cardiac function in selected patients with IDC. The striking degree of myocardial fibrosis can reduce to normal values after explantation of the device. A-beta 1-AABs disappear during ventricular unloading and do not increase thereafter. "Weaning" from mechanical device may constitute an alternative treatment to cardiac transplantation in selected patients.     

Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure

BACKGROUND: Mechanical, histological, and biochemical improvement has been described in patients after left ventricular assist device (LVAD) support. Explantation of the LVADs without heart transplantation has been described in selected patients who received this therapy as a bridge to transplantation. METHODS AND RESULTS: A retrospective review of patients receiving a mechanical bridge to transplantation at Columbia Presbyterian Hospital after July 21, 1991, was performed to determine the incidence of patients in whom the device was successfully explanted. From August 1, 1996, to February 1, 1998, we prospectively attempted to identify potential explant candidates by the use of exercise testing. During this time, we recruited 39 consecutive patients after insertion of the Thermo Cardiosystems vented electric device to participate in the following study. Approximately 3 months after device implantation, a maximal exercise test with hemodynamic monitoring and respiratory gas analysis was performed with the LVAD in the automated mode. The electric device was interfaced with a pneumatic console such that the rate could be decreased to 20 cycles/min. Hemodynamic measurements were recorded as the device rate was decreased. A repeat exercise test was then performed if the patient remained hemodynamically stable. A retrospective chart review of 111 LVAD recipients at our institution identified only 5 successful explant patients. Eighteen of the 39 patients were studied. Fifteen patients exercised with maximal device support. At peak exercise, VO2 averaged 14.5+/-3.6 mL. kg-1. min-1; LVAD flow, 8.0+/-1.3 L/min; Fick cardiac output, 11.4+/-3.3 L/min; and pulmonary capillary wedge pressure, 13+/-4 mm Hg. Seven patients remained normotensive and could exercise at a fixed rate of 20 cycles/min. In these patients, peak VO2 declined from 17.3+/-3.9 to 13.0+/-6.1 mL. kg-1. min-1. In one of these patients, the device was explanted. CONCLUSIONS: Significant myocardial recovery after LVAD therapy in patients with end-stage congestive heart failure occurs in a small percentage of patients. Most of these patients have dilated cardiomyopathy. Exercise testing may be a useful modality to identify those patients in whom the device can be explanted.     

Altered myocardial phenotype after mechanical support in human beings with advanced cardiomyopathy

BACKGROUND: Left ventricular assist devices (LVAD) provide lifesaving circulatory support to patients awaiting heart transplantation. To date, the extent to which sustained mechanical unloading alters the phenotype of pathologic myocardial hypertrophy in dilated cardiomyopathy is unknown. METHODS: We examined left ventricular size, myocyte and myocardial immunoreactivity for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in eight patients with advanced dilated cardiomyopathy before and after LVAD support. The mean duration of congestive heart failure was 18 +/- 5 months, and LVAD support averaged 42 +/- 4 days before heart transplantation. RESULTS: Echocardiographically determined left ventricular mass decreased from 505 +/- 83 to 297 +/- 52 gm (p < 0.05) during LVAD support, whereas minimum myocyte diameter decreased from 28.1 +/- 0.9 to 21.7 +/- 0.6 microns (p < 0.01) in transmural myocardial tissue specimens. Overall left ventricular ANP immunopositivity decreased from 48% at LVAD placement to 12% at transplantation (p < 0.05), whereas BNP immunopositivity decreased from 28% to 4% after LVAD support. Moreover, a gradient of ANP and BNP immunostaining from subendocardium to epicardium observed before mechanical unloading diminished after LVAD support. Analysis of the relationship between left ventricular mass and ANP immunopositivity revealed a close and highly significant correlation between these variables. CONCLUSIONS: These studies demonstrate remarkable left ventricular plasticity even in the presence of advanced cardiomyopathy. Parallel reductions in myocardial mass and myocyte size with reductions in ventricular ANP and BNP immunostaining indicate a novel regression of the phenotype of pathologic hypertrophy within the human myocardium after LVAD support.     

Infections during extended circulatory support: University of Alabama at Birmingham experience 1989 to 1994

BACKGROUND: The University of Alabama at Birmingham experience with investigational ventricular assist devices (VADs) used as a bridge to transplantation has increased over the past several years; it now includes 27 VAD implantations with 13 VAD runs lasting for extended periods (ie, > 30 days). A review of complications experienced by patients during extended VAD runs is warranted before the further development and testing of chronically implanted mechanical circulatory support devices. METHODS: This study focuses on the infectious complications of extended VAD support; it includes 13 patients who were supported by either a Thoratec or HeartMate VAD for longer than 30 days pending cardiac transplantation. Infection was defined as any positive culture. The infections were classed according to site and severity as follows: class I were patient-related non-blood-borne infections, class II were blood-borne infections, class III were VAD percutaneous site infections, and class IV were infections of the blood-contacting surfaces or intracorporeal components of the VAD. RESULTS: The 8 Thoratec and 5 HeartMate patients were supported for a total of 1,648 days with a range of 33 to 279 days per patient. Every patient had at least one infection; however, there were 6 patients who had no class II or IV infections during the period of support. One of these 6 patients died of a stroke, whereas the other 5 patients survived VAD support. No trends were identified for a change in the incidence of bacterial compared with fungal infections during the course of VAD support. There was no trend for a greater number of infections in patients who died during VAD support compared with those who survived. Neither class II nor IV infections precluded transplantation. Three patients died during VAD support; 1 died as a direct consequence of fungal infection. Eight patients received transplants. One patient had an unanticipated recovery of cardiac function and the VAD was removed. Support in 1 patient is ongoing. CONCLUSIONS: Infection during VAD support pending cardiac transplantation is an important cause of morbidity and mortality in patients maintained for longer than 30 days by circulatory assist. Infectious complications will probably be a prominent component of the risk associated with the use of chronically implanted mechanical circulatory assist devices and will likely have an important effect on the quality of life experienced by these patients.     

Current status of heart assist and replacement in Taiwan

The first clinical application of intraaortic balloon pumps (IABP) in Taiwan was in 1976 to treat post-cardiotomy cardiogenic shock. It is now the most commonly used circulatory assist. From 1991 to 1995, 186 patients received IABP support with an overall mortality rate 41.9%. The male patients had the best survival rate, 67%, after coronary artery bypass grafting. The first extracorporeal membrane oxygenation (ECMO) was in 1987 to treat intractable heart failure caused by severe acute rejection after heart transplantation. Because of poor outcome, patients only received ECMO sporadically during the past years. From November 1994 to November 1995, 30 patients received ECMO support with 50% of them eventually weaned from ECMO and 27% discharged. For short-term support or emergency rescue, ECMO was a good choice. When long-term support was required, the ventricular assist device (VAD) was a more suitable assist. One patient who received Thermedics VAD developed right heart failure and finally died of sepsis and multiple organ failure. VAD should be implanted before the secondary organ failure. The first successful clinical heart transplantation in Taiwan was performed on July 17, 1987. From 1991 to 1995, 102 patients underwent heart transplantation. The operative mortality was 3.9%, and the 1 and 5 year actuarial survival rates were 86 +/- 3% and 77 +/- 5%, respectively. To improve the success rate of clinical heart transplantation, organ donation should be encouraged.     

Assessment of timing right ventricular assist device withdrawal using left ventricular assist device filling characteristics

Right ventricular assist devices (RVAD) are often needed on a short term basis in patients who develop RV failure after left ventricular assist device (LVAD) implantation. The purpose of this study was to use LVAD filling characteristics to help determine the timing for weaning a patient from RVAD support. Eleven patients (age 50 years +/- 15) supported with an LVAD (Novacor) and an RVAD (Biomedicus or ABIOMED) were studied. Eight patients (RV recovery group) were studied before RVAD removal and all were successfully weaned from RVAD support. Five patients (RV failure group) were studied at the time of RVAD placement to determine baseline characteristics of RV failure. Simultaneous measures of LVAD volume and routine hemodynamics were recorded during periods of high and low RVAD flow. The LVAD filling was assessed as the first derivative of LVAD volume and the mean filling rate for each cardiac cycle was calculated and averaged over 10 sec periods at both RVAD flows. The mean pump rate corrected filling rates did not change in the RV recovery group (89 +/- 13 vs. 87 +/- 8 ml/beat) and significantly decreased in the RV failure group (84 +/- 19 vs. 62 +/- 22 ml/ beat) (p < 0.001) with decreasing RVAD flow. These data suggest that LVAD filling rates may be used to assess RV systolic function and the proper timing of RVAD removal in selected patients.     

Unexplained physical symptoms: outcome, utilization of medical care and associated factors

BACKGROUND: Measurement of intracardiac hemodynamic parameters has been limited to brief periods in the acute care setting. We developed and evaluated an implantable hemodynamic monitor that is capable of measuring chronic right ventricular oxygen saturation and pulmonary artery pressure. METHODS AND RESULTS: The device consists of an electronic controller placed subcutaneously and two transvenous leads placed in the right ventricle (reflectance oximeter) and pulmonary artery (variable capacitance pressure sensor). Implantation was performed in 10 patients with severe left ventricular dysfunction. Average implant pulmonary artery pressures were systolic, 52 +/- 16 mm Hg; diastolic, 29 +/- 11 mm Hg; and mean, 40 +/- 12 mm Hg. The mean right ventricular oxygen saturation at implant was 51%. Provocative maneuvers, including postural changes, sublingual nitroglycerin, and bicycle exercise, demonstrated expected changes in measured oxygen saturation and pulmonary artery pressures over time. At follow-up of 0.5 to 15.5 months, there were no significant differences between pulmonary artery pressures or oxygen saturation values transmitted from the device and simultaneous measurement with balloon flotation catheters. Four of the pulmonary artery leads dislodged and three demonstrated sensor drift, whereas two of the oxygen saturation sensors failed. Four patients died and four received transplants. Pathological study did not demonstrate injury to the right ventricular outflow tract or pulmonic valve. CONCLUSIONS: Chronic measurement of hemodynamic parameters in the outpatient setting with implantable sensor technology appears to be feasible. The devices are well tolerated without significant untoward effects, and the sensors generally function well over time, providing reliable information. Clinical usefulness remains to be established.     

Transient normalization of systolic and diastolic function after support with a left ventricular assist device in a patient with dilated cardiomyopathy

A 19-year-old man who had fulminant heart failure caused by an idiopathic dilated cardiomyopathy was supported with a left ventricular assist device for 183 days as a bridge to heart transplantation. At the time of intended transplantation it was noted that the patient's heart had returned to normal size, had a normal ejection fraction, and was able to maintain normal pressures and flows. In view of the apparent recovery of cardiac properties, the left ventricular assist device was explanted and the transplantation was not performed. However, the heart dilated, ejection fraction worsened, and the patient died of heart failure exacerbated acutely by a systemic viral illness. Although such recovery of systolic function is uncommon, as use of the left ventricular assist devices becomes more widespread other physicians might encounter similar findings and, in this regard, they might find our experience useful as they contemplate their treatment options.     

High stroke volume para-aortic counterpulsation device versus centrifugal pump in cardiogenic shock: experimental study

During the last decades a number of left ventricular assist devices has been used especially for patients resistant to pharmacologic treatment and to intraaortic balloon pump (IABP) support for left ventricular failure. A high stroke volume para-aortic counterpulsation device (PACD) has been developed utilizing the principle of the diastolic counterpulsation technique. In this study the hemodynamic effects of the valveless PACD were compared to those of the centrifugal blood pump (CBP) in nine dogs in acute experimental cardiogenic shock. Hemodynamic measurements were obtained at baseline with both devices off, PACD on and CBP off, or PACD off and CBP on. There was no difference in mean aortic pressure between PACD on (60.0 +/- 11.5 mmHg) and CBP on (69.0 +/- 26.8 mmHg). Similarly, there was no difference in left ventricular end-diastolic pressure with the PACD on (11.9 +/- 5.4 mmHg) versus the CBP on (9.9 +/- 5.2 mmHg) or the cardiac index with the PACD on (84 +/- 36 ml/kg/min) versus the CBP on (77 +/- 36 ml/kg/min). However, the left ventricular systolic pressure (55.0 +/- 19.0 with PACD versus 73.0 +/- 26.0 with CBP,p < 0.001), the tension time index (712 +/- 381 versus 1333 +/- 694,p < 0.01), and the double product (5629 +/- 2574 versus 7440 +/- 3294,p < 0.01) were significantly lower during assistance with the PACD than with the CBP. It was concluded that PACD is at least as effective as CBP for restoring hemodynamic status during acute experimental cardiogenic shock. Moreover, the PACD unloads the left ventricle more effectively than CBP, making it suitable for left ventricular mechanical support in cases with reversible myocardial damage.     

Reflections on external circulatory assistance. Apropos of 8 patients treated with the MEDOS system

Mechanical circulatory support is required when cardiogenic shock is unresponsive to well conducted medical therapy. In this hemodynamic situation, when the patient's life is in danger, within hours, several questions should be answered quickly. These questions take into consideration the etiologies of cardiogenic shock and are related to the possibility of improvement of myocardial function, cardiac transplantation, the choice of uni- or biventricular support and surgical techniques of left ventricular assistance (left atrium to aorta or left ventricular apex to aorta). The follow-up of patients with circulatory support is complex. It requires to take into consideration hemodynamic, mechanical and hemobiological parameters as well as the peripheric organ function. We report in this article our clinical experience with eight patients that underwent circulatory support with Medos external ventricular assist device.     

Influence of longer term left ventricular assist device support on valvular regurgitation

The authors previously published data that describe acute alterations in ventricular dimensions and in the severity of mitral and tricuspid regurgitation (MR/TR) after initiation of left ventricular assist device (LVAD) pumping. In the current study, measurements of ventricular size and regurgitant jet area acquired after LVAD implantation are presented. Eight patients had LVAD implanted pending cardiac transplantation (duration of assist 70-279 days; mean, 162 +/- 29 days). Echocardiograms were obtained at the time of LVAD implant and later during LVAD support (mean time for late echo, 95 +/- 32 days post-implant). Comparisons of pre-implant with late post-implant data showed: increased TR jet area (4.8 +/- 1.0 cm2 vs. 8.0 +/- 1.7 cm2 P < 0.05); increased right ventricular (RV) end-systolic dimension (31 +/- 4 vs 40 +/- 5 mm, P < 0.05); and increased RV end-diastolic dimension (35 +/- 4 vs. 45 +/- 5 mm, P < 0.065). Decreased MR jet area and decreased LV dimensions (P < 0.05) also were noted on comparison of pre-implant and late post-implant data. There were no significant differences between any immediate post-implant and late post-implant echocardiographic measurements. No patient had clinical evidence of RV failure. LV mechanical assist causes an acute increase in TR, presumably by volume loading the RV. TR and RV enlargement persisted but did not discernibly worsen on subsequent post-implant echocardiograms. LV dimensions and MR remained less than the pre-implant values on later post-implant determinations.     

Hemodynamic effects of the implantation of an intracaval oxygenator

Treatment of severe respiratory failure by extracorporeal membrane oxygenation (ECMO) is complex. However, there is now an intravascular gas exchanger (IVOX) available that provides extrapulmonary gas transfer without requiring an extracorporeal blood path. The present study was performed to determine the hemodynamic effects resulting from the intracaval placement of the intravascular device. A bovine model (n = 6; body-weight = 72 +/- 5 kg) was selected for temporary lung support with the intravascular device. The latter was placed in the caval axis under fluoroscopic control after full instrumentation of the animal for hemodynamic measurements including a pulmonary artery catheter for determination of cardiac output by thermodilution and continuous readout of mixed venous oxygen saturation. All measurements were taken after a stabilization period of 15 min. The heart rate moved from 65 +/- 8 before to 72 +/- 10 after implantation and 68 +/- 9 after onset of intravascular gas exchange (NS). Right atrial pressure was 13 +/- 3 mm Hg before, 12 +/- 3 mm Hg after implantation and 10 +/- 3 mm Hg after onset (NS) whereas femoral venous pressure moved from 14 +/- 3 mm Hg to 17 +/- 4 mm Hg (p < 0.05) and remained at 17 +/- 4 mm Hg after onset. Cardiac output was 5.3 +/- 0.7 l/min before, 5.4 +/- 0.7 l/min after implantation and 5.3 +/- 1.1 l/min after onset (NS) while mixed venous oxygen saturation dropped from 60 +/- 7% to 54 +/- 11% and moved to 57 +/- 11 after onset of the device (NS).(ABSTRACT TRUNCATED AT 250 WORDS)