The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings. Impedance measurements showed a good correlation with CO2 rebreathing stroke volume measurements in VVI patients. Impedance variations were then used to set the optimal AV delay at different pacing rates in DDD patients. The inverse relationship between the optimal AV delay and the pacing rate has been accurately identified in most of the patients but is not predictable. In all cases, the cardiac output was higher in DDD mode at the optimal AV delay than in VVI mode. In some patients with a damaged myocardium, the stroke volume appeared to be highly sensitive to multiple AV delay settings. Impedance plethysmography can permit such repetitive non-invasive quick measurements, increasing the accuracy of optimal AV delay determination and is well suited for routine examination of patients with cardiac dual chamber pacemakers.

Orthotopic en bloc transplantation of the heart and one lung has been done in two patients with end-stage cardiopulmonary disease and a prior thoracic operation. The first patient had undergone right pulmonary thromboembolectomy with caval ligation 5 years earlier, and the second had had left lower lobectomy for bronchiectasis 15 years before the heart and contralateral lung transplantation. Surgical procedures followed the techniques that had been developed in animals. Transplantation of the unoperated contralateral lung made it possible to avoid dissection in the obliterated pleural space and to minimize bleeding, which simplified the procedure considerably. Dramatic reduction in pulmonary artery pressure and improved respiratory function allowed both patients to be weaned from cardiopulmonary bypass without problems. Although the first patient died of liver and renal failure soon after the operation, an intact cough reflex facilitated recovery in the second patient, who has been discharged with essentially normal respiratory function. This report describes heart and unilateral lung transplantation as a procedure of choice for patients with extensive pleural adhesions that made total cardiopulmonary replacement unfeasible.

Proton magnetic resonance spectroscopy of plasma indicates an alteration of proteolipid methyl and methylene resonances after heart transplantation. The intensity of these alterations is modulated by the transplant tolerance phenomena and allows the accurate detection of heart graft rejection. These results reinforce the analogy between the immunology of graft tolerance and the immunology of cancer or pregnancy where identical alterations have been identified.

To evaluate the changes in left ventricular filling associated with acute cardiac rejection, serial Doppler echocardiographic examinations were prospectively performed on the same day as endomyocardial biopsy in 55 consecutive patients who successfully underwent orthotopic transplantation and were free of a previous episode of rejection. On average, 8.6 Doppler studies per patient were performed within a 6 month period after transplantation. Recordings of mitral flow were made with pulsed Doppler and two-dimensional echocardiography from an apical four chamber view; isovolumic relaxation time, peak early mitral flow velocity and pressure half-time were measured. The patients were classified into two groups on the basis of the histopathologic findings: group I (25 patients with at least one episode of mild or moderate rejection) and group II (30 patients without rejection). In group I, rejection was associated with a significant decrease of isovolumic relaxation time (p less than 0.005) and especially pressure half-time (p less than 0.0005) with no change in heart rate and peak early mitral flow velocity. In group II, Doppler indexes remained unchanged. These changes were not associated with alterations in left ventricular systolic function assessed by echocardiography. Isovolumic relaxation time and pressure half-time both returned to values similar to baseline values after immunosuppressive therapy (p less than 0.05 and p less than 0.0005, respectively). With 20% decrease in pressure half-time as a criterion for acute rejection, sensitivity was 88%, specificity 87% and positive predictive value 85%. Thus, Doppler echocardiographic evaluation of left ventricular diastolic function provides an excellent tool for early detection of acute rejection and noninvasive monitoring of the cardiac transplant recipient.