Relationship of cardiac allograft size and pulmonary vascular resistance to long-term cardiopulmonary function

The purpose of this study was to evaluate the long-term cardiopulmonary function of heart transplant patients who received disproportionately sized allografts for varying levels of pulmonary vascular resistance. Resting hemodynamics and oxygen uptake during exercise were recorded at 1 year after transplantation in 52 patients. No differences in resting heart rate, cardiac output, stroke volume, peak oxygen uptake during exercise, and exercise duration were found in recipients of undersized hearts (donor:recipient weight ratio [D:R] <0.75), sized-matched hearts [D:R = 0.75 to 1.25), and oversized (D:R >1.25) hearts. In a further analysis according to preoperative pulmonary vascular resistance, resting cardiac output (5.8±1.3L/min) was normal, and peak exercise oxygen uptake (22.7±8.0ml/kg/min) was mildly decreased in recipients of size-matched allografts with a pulmonary vascular resistance of less than 3 Wood units (size-matched hearts, with mild or no pulmonary vascular resistance). Of patients with moderate pulmonary hypertension (pulmonary vascular resistance ≥3 Wood units), resting cardiac output was normal (5.1±0.6L/min) in recipients of oversized hearts and was reduced (4.7±1.0L/min) in recipients of size-matched hearts (p<0.05 versus recipients of size-matched hearts with pulmonary vascular resistance less than 3 Wood units). Peak exercise oxygen uptake was, however, markedly reduced in the recipients of oversized hearts (16.4±3.0ml/kg/min; p=0.07, versus recipients of size-matched hearts with pulmonary vascular resistance less than 3 Wood units) and only mildly impaired in the recipients of size-matched hearts (21.0±4.4ml/kg/min; p = not significant, versus recipients of size-matched hearts with pulmonary vascular resistance less than 3 Wood units). Of patients with a pulmonary vascular resistance of less than 3 Wood units, resting cardiac output (5.0±1.4L/min) and peak exercise oxygen uptake (19.4±4.3ml/kg/min) in recipients of undersized hearts was similar to those who received size-matched hearts. Two patients with oversized hearts and pulmonary vascular resistance of less than 3 Wood units had normal resting cardiac output (6.1 and 6.2L/min) and peak exercise oxygen uptake (23.6 and 42.0ml/kg/min). In the presence of moderate preoperative pulmonary hypertension, long-term cardiopulmonary function is compromised in recipients of oversized allografts and mildly impaired in recipients of size-matched allografts. In its absence, cardiopulmonary function is impaired to similar degrees with undersized and size-matched allografts and normal with oversized allografts. Our findings support the liberalized use of undersized hearts for transplantation of patients without moderate pulmonary hypertension and suggest that oversized allografts are not beneficial to the long-term cardiopulmonary function of patients with moderate pulmonary hypertension.