EXERCISE HEMODYNAMICS DURING LONG-TERM IMPLANTATION OF A LEFT-VENTRICULAR ASSIST DEVICE IN PATIENTS AWAITING HEART-TRANSPLANTATION

Objectives. The goal of this study was to assess patients with end-stage heart disease after implantation of a left ventricular assist device at rest and during exercise compatible with activities of daily life. Background. Mechanical circulatory assistance with a left ventricular assist device is an accepted therapy for bridging patients with end stage heart disease to heart transplantation and has been proposed for long-term implantation. Methods. Three patients (aged 37, 42 and 57 years) with end stage heart failure required implantation of a pneumatically driven, asynchronous Thermedics left ventricular assist device while awaiting heart transplantation. All were assessed 1 month later during graded supine bicycle exercise (maximal work load 100 to 150 W). Detailed central hemodynamics, including continuous pulmonary artery oxygen saturation and oxygen consumption measurements, were obtained. Two of the patients also underwent upright treadmill exercise with oxygen consumption measurements. Results. During supine bicycle exercise, the heart rate increased from 93 +/- 37 beats/min (95% confidence interval: mean +/- t(0.025) x SE) at rest to 119 +/- 54 beats/min and left ventricular assist device rate increased from 82 +/- 47 to 109 +/- 55 beats/min. Oxygen consumption increased from 3.0 +/- 0.9 to 8.7 +/- 2.9 ml oxygen/min per kg body weight. Cardiac output increased from 6.0 +/- 4.4 to 9.6 +/- 7.1 liters/min, yielding an average exercise factor of 8.5 +/- 7.7 and an exercise index of 0.83 +/- 0.61. The patients assessed during treadmill exercise achieved a maximal oxygen consumption of 14.3 and 16.7 ml of oxygen/min per kg. No thromboembolic or other complications attributable to left ventricular assist device implantation occurred during the duration of support. All patients survived orthotopic heart transplantation and are doing well. Conclusions. Significant work loads compatible with activities of daily life and adequate exercise hemodynamics were demonstrated by these patients while awaiting heart transplantation. Definitive conclusions regarding the use of this device must be viewed as preliminary because only three patients were involved in this study and the failure rate may be as high as 71% (95% confidence interval of left ventricular assist device success as a bridge to transplantation 29.3% to 100%). Final conclusions regarding the safety and efficacy of the left ventricular assist device as a possible long term circulatory sup port device must await results of larger multicenter trials in progress.