ABSTRACT
Arterial compliance (C) is related to the elasticity, size, and geometrical distribution of arteries. Compliance is a determinant of the load that impedes ventricular ejection. Measuring compliance is difficult, particularly in the pulmonary circulation in which resistive and compliant vessels overlap. Comparing different methods for quantification of compliance to a method that involves a continuous flow might help to identify the optimal method. Pulmonary arterial compliance was computed in six pigs based on the stroke volume to pulse pressure ratio, diastolic decay exponential fitting, area method, and the pulse pressure method (PPM). Compliance measurements were compared to those obtained under continuous flow conditions through a right ventricular bypass (Heartware Inc., Miami Lakes, FL, USA). Compliance was computed for various flows using diastolic decay exponential fitting after an abrupt interruption of the pump. Under the continuous flow conditions, resistance (R) was a decreasing function of the flow, and the fitting to P = e-t/RC yielded a pulmonary time constant (RC) of 2.06 s ( ± 0.48). Compliance was an increasing function of flow. Steady flow inter-method comparisons of compliance under pulsatile flow conditions showed large discrepancies and values (7.23 ± 4.47 mL/mmHg) which were lower than those obtained under continuous flow conditions (10.19 ± 1 0.31 mL/mmHg). Best agreement with steady flow measurements is obtained with the diastolic decay method. Resistance and compliance are both flow-dependent and are inversely related in the pulmonary circulation. The dynamic nature of the pulsatile flow may induce a non-uniformly distributed compliance, with an influence on the methods of measurement.
ABSTRACT
BACKGROUND: Due to budgetary restrictions our university heart transplant program came to a standstill to be gradually restarted early 2011. Consequently waiting-times for transplantation increased dramatically beyond the usual 10-15 months. We reviewed the clinical results of this peculiar transplant program over the past 4 years. METHODS: Since March 2011 until February 2015, 65 patients (age 48±23 years) were listed for heart transplantation. Eight patients (11%) of whom three in high emergency were transplanted without any form of mechanical assistance. Fifty-one patients required a left ventricular assist device (LVAD) Heartware (Heartware Inc., Miami Lakes, FL, USA) as a bridge-to-transplant due to terminal heart failure. Merely 5 listed patients remain without assistance. RESULTS: One patient without assistance and 11 LVAD patients (22%) died on the waiting-list. Meanwhile 10 LVAD patients were transplanted after a 2-year waiting time (770±717 days). Four transplanted patients died of early graft failure none after LVAD explantation. Survival at 1 and 3 years was respectively 78 (72%) and 83 (78%) for transplanted and assisted patients (log-rank P=0.056). Cox multivariable regression analysis identified crash-to-burn patients (P=0.002) and waiting-times over 2 years (P=0.044) as risk factors for early death, while age above 60 (P=0.008) and ischemic aetiology (P=0.029) and pulmonary hypertension (P=0.092) were risk factors for survival. CONCLUSIONS: In times of donor shortage mechanical assistance proves very effective as bridge-to-transplant in patients for whom candidacy follows the standard inclusion procedures. In our settings, a steep increase in LVAD implantation served to salvage patients for whom transplantation became jeopardized due to an ever increasing waiting-time. Circulatory LVAD support could be considered as primary therapy in the future.
