Surgical techniques for the implantation of heterotopic prosthetic ventricles

Risk analysis in patients bridged to transplantation

BACKGROUND

Efforts to predict mortality in bridge to cardiac transplant patients have concentrated on preventricular assist device (VAD) status. To more fully identify factors influencing survival to transplant, we reviewed the preoperative and postoperative VAD courses of 105 bridge to transplant patients.

METHODS

Sixty-four parameters (34 pre-VAD, 30 post-VAD), including hemodynamics, complications, and evaluations of major organ function were examined and analyzed.

RESULTS

Thirty-three patients (31%) died on VADs and 72 were transplanted. There were two posttransplant operative deaths (3%). By univariate analysis 23 of 64 factors were significant. These 23 factors were entered into a stepwise logistic regression analysis to identify predictors of survival to transplant. Four factors, including pre-VAD intubation (p < 0.005), cardiopulmonary bypass (CPB) time during VAD insertion (p < 0.0001), mean pulmonary artery pressure (first postoperative day after VAD) (p < 0.0002), and highest post-VAD creatinine (p < 0.01) were independent predictors of transplantation.

CONCLUSIONS

Other than the need for intubation, pre-VAD variables were of little value in predicting survival to transplant. Problems during VAD insertion (long CPB time) and post-VAD renal insufficiency were independent predictors. Severe complications that developed during the interval of VAD support, including cerebrovascular accident, bleeding and infection, were surprisingly not predictors for transplantation.

Transfer of patients receiving advanced mechanical circulatory support

OBJECTIVE

Improving results with ventricular assist devices have led to their wider clinical application. Centers can stabilize, support, and wean or transfer patients to regional transplant centers.

METHODS

Prospectively collected data were reviewed to evaluate the clinical results of patients transferred to our institution while receiving advanced mechanical circulatory support.

RESULTS

Since 1993, 16 patients were accepted while receiving support with either extracorporeal membrane oxygenation or a ventricular assist device. The 10 male and 6 female patients ranged in age from 9 to 60 years (mean, 42.1 years). Thirteen had had cardiac surgical procedures, two had acute myocardial infarctions, and one had myocarditis. The distance transported ranged from 0.2 to 309 miles (mean, 132 miles). Twelve patients were transferred by ground, and 4 were transported by air. Seven patients were originally supported with extracorporeal membrane oxygenation, 6 with centrifugal pumps, and 3 with ABIOMED ventricular assist devices (ABIOMED, Inc, Danvers, Mass). Two patients had clinical complications during transfer, and one had a cerebrovascular accident, recovered, was weaned, and survived. A second patient had hemodynamic deterioration. There were no technical complications associated with transport. Six patients were left on the original support device; 3 of the 6 were weaned and survived, and 3 died during support. The 10 remaining patients were switched to other ventricular assist devices: 9 patients to Thoratec devices (Thoratec Laboratories, Pleasanton, Calif) and 1 patient to a Novacor device (Baxter Healthcare Corp, Novacor Division, Oakland, Calif). Six of the 10 patients underwent transplantation and survived. Four patients died while being supported by the devices. Nine patients were discharged, with 1 late death at 29 months. Eight patients are alive 4 to 65 months after discharge.

CONCLUSIONS

These data suggest that patients receiving advanced support can be moved between clinical centers with acceptable risks. Because 33% of the survivors were weaned, transplantation is not required for survival.

Clinical experience with 111 thoratec ventricular assist devices

BACKGROUND

Ventricular assist devices (VADs) have gained wider acceptance due to refinements in patient selection and management and device availability.

METHODS

To evaluate early and late results, we reviewed our first 111 patients with the Thoratec VAD.

RESULTS

Forty-four patients were supported for myocardial recovery. The mean age in the recovery group was 51.9 years. There were 18 left VADs (LVADs), 17 biventricular VADs (BVADs), and nine right VADs (RVADs). Complications included bleeding in 20 patients (45%) and device-related infection in 1 patient (2%). Nineteen were weaned from the VAD, with 12 survivors. Sixty-seven patients were supported as a bridge to cardiac transplantation. The mean age was 41.5 years. There were 39 LVADs and 28 BVADs. Complications included bleeding in 21 patients (31%) and device-related infection in 12 (18%). Three patients were weaned and 39 patients were transplanted from the assist device, for a total of 42 bridge survivors. Device-related thromboembolism occurred in 9 patients (8.1%), 7 of whom were bridge to transplantation. The duration of VAD support ranged from 0.1 to 27 days (mean 4.5 days) in the recovery group and 0.2 to 184 days (mean 40.7 days) in the bridge to transplantation group. The 10-year actuarial survival was 16% for the recovery group, 22%, for the bridge group, and 33% for transplanted patients.

CONCLUSIONS

Despite advances, VAD support remains associated with significant morbidity and operative mortality.

The continuing evolution of mechanical ventricular assistance

A great number of patients suffer and die of the sequelae of acute and chronic heart failure each year. Although advances in medical and surgical therapy have benefited many of these patients, most have disease that is refractory to any definitive therapy. For these patients cardiac transplantation is the only remaining hope. Unfortunately, because of the increasing demand for donor organs in the face of a fixed and limited supply, this option is available to only a small percentage of these patients. Even in patients accepted for transplantation, a significant waiting list mortality has been observed. A variety of VADs have been developed since the first successful case of mechanical cardiac assistance more than 30 years ago. These devices differ in basic mechanical function, method of insertion, and degree of implantability and thus have different indications and potential applications. Whereas the intraaortic balloon pump and centrifugal pumps are effective short-term support modalities, extracorporeal and implantable pulsatile devices have been used successfully for long-term support of patients with reversible and nonreversible cardiac failure. Although these pumps have most commonly been used as bridges to transplantation, increasing clinical experience has supported the notion of long-term mechanical assistance as a definitive therapy for patients with end-stage heart disease. Although complications, particularly infection and thromboembolism, pose significant challenges and long-term device reliability remains to be fully determined, available implantable devices appear to be capable of providing effective long-term support. As data are obtained from currently ongoing trials comparing VAD support with medical therapy for end-stage heart failure, ethical and economic issues will assume increasing importance.

Preoperative and postoperative comparison of patients with univentricular and biventricular support with the thoratec ventricular assist device as a bridge to cardiac transplantation

OBJECTIVES

The goal of this study was to determine whether there are differences in populations of patients with heart failure who require univentricular or biventricular circulatory support.

METHODS

Two hundred thirteen patients who were in imminent risk of dying before donor heart procurement and who received Thoratec left (LVAD) and right (RVAD) ventricular assist devices at 35 hospitals were divided into three groups: group 1 (n = 74), patients adequately supported with isolated LVADs; group 2 (n = 37), patients initially receiving an LVAD and later requiring an RVAD; and group 3 (n = 102), patients who received biventricular assistance (BiVAD) from the beginning.

RESULTS

There were no significant differences in any preoperative factors between the two BiVAD groups. In the combined BiVAD groups, pre-VAD cardiac index (BiVAD, 1.4 +/- 0.6 L/min per square meter, vs LVAD, 1.6 +/- 0.6 L/min per square meter) and pulmonary capillary wedge pressure (BiVAD, 27 +/- 8 mm Hg, vs LVAD, 30 +/- 8 mm Hg) were significantly lower than those in the LVAD group, and pre-VAD creatinine levels were significantly higher (BiVAD, 1.9 +/- 1.1 mg/dl, vs LVAD, 1.4 +/- 0.6 mg/dl). In addition, greater proportions of patients in the BiVAD groups required mechanical ventilation before VAD placement (60% vs 35%) and were implanted under emergency conditions than in the LVAD group (22% vs 9%). The survival of patients through heart transplantation was significantly better in patients who had an LVAD (74%) than in those who had BiVADs (58%). However, there were no significant differences in posttransplantation survival through hospital discharge (LVAD, 89%; BiVAD, 81%).

CONCLUSION

Patients who received LVADs were less severely ill before the operation and consequently were more likely to survive after the operation. As the severity of illness increases, patients are more likely to require biventricular support.

Left ventricular cannula obstruction in a patient with previous ventricular aneurysmectomy

Cannula position is an important factor influencing optimal ventricular assist device function. A case of inflow cannula malposition resulting in suboptimal left ventricular assist device performance is presented. A discussion of alternative techniques and diagnosis is provided.

Use of a Dacron cuff to decrease bleeding from atrial cannulas of ventricular assist devices

The use of ventricular assist devices is becoming more common for postcardiotomy cardiogenic shock and as a mechanical bridge to transplantation. Bleeding is the most common complication reported in most clinical series. The sources of bleeding are multiple, but our experience is that a substantial percentage occurred from cannulation sites. We present a technique that we believe decreases the incidence of bleeding from atrial cannulation sites of such devices.

Univentricular and biventricular Thoratec VAD support as a bridge to transplantation

As of October 1991, the Thoratec ventricular assist device (VAD) system has been used in 154 transplant candidates who were in imminent risk of dying before donor heart procurement at 39 medical centers in 10 countries. The VAD system consists of a prosthetic ventricle with a 65-mL pumping chamber made from Thoratec's BPS-215M polyurethane, cannulas for atrial or ventricular inflow and arterial outflow connections, and a pneumatic drive console. The devices can be used for partial or complete support of the pulmonary, systemic, or both circulations. In all patients (average age, 42 years; range, 11 to 64 years), the pumps were placed in a paracorporeal position on the anterior abdominal wall and connected to the heart and great vessels by cannulas crossing the chest wall. Biventricular support was used in 120 patients (78%) and isolated left VADs were used in 34. Average flow rate was 5.0 +/- 0.9 L/min for the left VAD and 4.3 +/- 0.8 L/min for the right VAD. The most frequent complications were bleeding (42% incidence, 7% mortality) and infection (36% incidence, 8% mortality). Ninety-eight patients (65%) recovered sufficiently to undergo heart transplantation after 8 hours to 226 days of support (average, 17.5 days), and 3 are waiting on VADs for transplantation. Eighty-two patients who received transplants have been discharged. This is an 84% early post-transplantation survival and a 54% overall survival. The actuarial survival 1 year after transplantation is 82%, comparable with that of conventional heart transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Techniques for optimization of pulsatile ventricular assist device support

For some time now researchers have argued the efficacy of pulsatile versus nonpulsatile hemodynamic support. Pulsatile systems, while providing a more physiological pumping source, are burdened with a multiparametric output function that can greatly affect the utility of such ventricular assist device (VAD) support. A simplified approach to the optimization of the pulsatile VADs' output function has been developed. This approach yields device outputs of approximately 5.5 L/min at physiologic pressures while demonstrating clinically acceptable blood chemistry. Obtaining this optimal operating point involves the determination of the VAD system output function for a range of fill-enhancing vacuum settings. A quantitative method for evaluating synchronous versus asynchronous pumping modes as related to coronary perfusion is also demonstrated.

[Value of continuous venous blood oxygen measurement during external circulatory assistance]

A case is reported of a 40 year-old man, on the waiting-list for heart transplantation, who developed terminal heart failure. Using an Opticath catheter and a radial artery catheter, SV(-)O2 was monitored continuously, and cardiac output, pulmonary arterial and wedged pressures, and right atrial pressure were repeatedly measured. Despite appropriate treatment (adrenaline, dobutamine, glyceryl trinitrate), the patient remained in anuria and cardiogenic shock. External circulatory support (ECS) (BVS 5000 Abiomed) was therefore used as a bridge to cardiac transplantation. The resultant increase in systemic blood flow led to an early and fast rise in SV(-)O2, from 40% to 73%, with a decrease in the oxygen extraction ratio (ERO2) from 50 to 30%. Serum lactate concentrations returned to normal within the first six hours of ECS (less than 120 mg.l-1). During the first 24 h of ECS, SV(-)O2 decreased and ERO2 rose significantly on two occasions: during an episode of shivering, and another of restlessness during nursing. An attempt at weaning the patient from the ventilator at the 39th h also led to a sudden decrease in SV(-)O2, with a rise in ERO2. The Opticath catheter was finally removed after 150 h of ECS because of a decrease in reflected light intensity.

The Pierce-Donachy ventricular assist device as a bridge to cardiac transplantation

The Pierce-Donachy ventricular assist device (VAD) was used as an attempted bridge to orthotopic cardiac transplantation in 12 patients aged 13 to 55 years. Ischemic (4 patients), dilated (4 patients), acute viral (1 patient), postpartum (1 patient), and hypertrophic cardiomyopathy (1 patient), along with a failed transplant (1 patient), were the causative factors of end-stage cardiomyopathy in these patients. All patients were candidates for orthotopic cardiac transplantation but sustained refractory cardiogenic shock (cardiac index less than 2 L/min/m2). Left VADs were placed in all patients; 7 also required right VADs. Four patients died of hemorrhagic complications less than 24 hours after VAD insertion. Ventricular assist device stabilization was successful in 8 patients and support ranged from eight hours to 64 days. Seven patients successfully underwent orthotopic cardiac transplantation. One died postoperatively of hemorrhagic complications, 6 were discharged from the hospital, and 1 patient died at 3 months of cytomegalovirus infection. Five patients are long-term survivors. The Pierce-Donachy VAD is an effective means for supporting critically ill patients with end-stage cardiomyopathy and cardiogenic shock before orthotopic cardiac transplantation. Death is related to hemorrhagic, rather than infectious or thromboembolic, complications. Patients successfully stabilized with the VAD can undergo orthotopic cardiac transplantation with acceptable mortality and morbidity rates.