Atrial natriuretic peptide release at rest and with exercise after cardiac transplantation with bicaval anastomoses.

Bicaval anastomoses in orthotopic cardiac transplantation offer the advantage of preserving the right atrial geometry. To elucidate the impact of this anastomotic technique on atrial natriuretic peptide plasma levels at rest and with exercise, nine patients were submitted to a symptom-limited supine exercise test. Atrial natriuretic peptide plasma levels in samples obtained from the right atrium were elevated at rest (274.4 +/- 60.4 pg/ml), at peak exercise (438.1 +/- 71.7 pg/ml), and thereafter (328.1 +/- 71.2 pg/ml) with respect to normal reference values of 21 +/- 1 pg/ml at rest and 92 +/- 14 at peak exercise. Renin, angiotensin, and aldosterone plasma levels were almost normal and did not indicate any pathologic processes in volume homeoostasis. Right-sided hemodynamic parameters were not correlated with atrial natriuretic peptide secretion. An adverse relationship between cold ischemic time of the donor organ and atrial natriuretic peptide release was found (r = 0.88, p < 0.0008), indicating that endocrine cardiocytes are sensitive to prolonged ischemia. Atrial natriuretic peptide release may thus be independent of the surgical approach, and other unique characteristics of the transplanted heart, such as denervation, are more likely to be responsible for elevated atrial natriuretic peptide plasma concentrations after orthotopic heart transplantation.

A new experimental model and formula for flow determination and possible application in sizing of interatrial communication.

The concept of an artificial interatrial communication in application of the Fontan procedure in high risk patients has raised the problem to exactly determine the shunt amount. This experimental study shows that in vitro flow studies of interatrial communications can be performed without animal blood and PTFE membranes respectively. Furthermore the simulation of an pulmonary vascular venous flow is not necessary. Additionally a new formula with acceptable accuracy for flow estimation is derived from the presented data obtained by this study.

Cardiovascular dynamics and dimensions after bicaval and standard cardiac transplantation.

Bicaval orthotopic cardiac transplantation leaving the right atrium intact has been introduced recently into clinical practice as an alternative to the standard method. To determine the effect of the surgical technique, 27 patients were studied at rest and supine exercise 19 +/- 5 months after bicaval orthotopic cardiac transplantation (group A, n = 15) and 22 +/- 7 months after standard orthotopic cardiac transplantation (group B, n = 12). Resting hemodynamics showed no difference between groups. With exercise, a significantly higher right atrial pressure was noted in group B. Echocardiographic analysis showed asynchronous right atrial contraction in 83% of group B patients versus none in group A. Resting right ventricular dimensions were significantly greater in group B (right ventricular end-diastolic diameter, 3.27 +/- 0.44 cm versus 2.88 +/- 0.35 cm [p < 0.05]; right ventricular end-diastolic area, 21.3 +/- 2.85 cm2 versus 17.1 +/- 2.01 cm2 [p < 0.005]). A higher incidence and significantly higher grade of tricuspid regurgitation were found throughout exercise in group B. The exercise duration (17.34 +/- 3.53 minutes versus 14.04 +/- 4.11 minutes [p < 0.05]) and the exercise capacity (1.17 +/- 0.25 W/kg versus 0.93 +/- 0.34 W/kg [p < 0.05]) were increased in group A. These data provide some evidence that the bicaval technique of cardiac transplantation improves cardiovascular dynamics and dimensions as well as exercise capacity.

Time course of lung function and exercise performance after heart transplantation.

To study the time course of exercise performance and the diffusion capacity after heart transplantation, we submitted two groups of patients to graded symptom-limited supine exercise. Patients in group 1 (n = 11) underwent operation 12.9 +/- 7.0 months before the study; those in group 2 (n = 10) underwent operation 53.9 +/- 14.8 months before the study. Respiratory and cardiovascular parameters were evaluated noninvasively at rest, at individual peak exercise, and 10 minutes later with a commercially available Sensormedics MMC 4400 metabolic measurement chart. Short-term survivors exhibited a lower maximum work capacity compared with that of long-term survivors (63.6 +/- 25.9 versus 100 +/- 50 W, p < 0.05), with a concomitant lower terminal heart rate (123 +/- 19 versus 137 +/- 17 beats/min, p < 0.05) that accounts for the lower cardiac output in this group, but statistical significance was not achieved (13.0 +/- 4.6 versus 17.5 +/- 6.3 L/min, not significant). Interestingly, significant differences were also observed for diffusion capacity before exercise (11.9 +/- 4.8 versus 19.3 +/- 7.3 ml/min/mm Hg, p < 0.05). The improvement of the diffusion capacity may be associated with a time-dependent change in the diffusion characteristics of the alveolocapillary membrane.