[Development of circulatory support during 420 aneurysm resections of the descending thoracic aorta]

From July 1974 to January 1996, 420 aneurysms of the descending thoracic aorta were surgically treated at l'Hôpital du Sacré-Coeur de Montréal. Three principles were previously established and rigorously respected: 1) the preservation of distal body perfusion, 2) the briefest aortic cross-clamp time realizable (mean: 29.8 +/- 16 minutes overall, reduced to a mean of 24 +/- 6 minutes for the last 250 cases), 3) keep the aortic resection as short as possible in order to preserve as many intercostal arteries as possible (10 cm or less in 91.6% of the cases). In the first 380 cases, distal aortic circulation was supported with a 9 mm Gott shunt without using systemic heparinization. Average shunt flows from 300 ml/min, to 4900 ml/min. (mean: 2497 +/- 813 ml/min.), average proximal pressures from 80 to 200 mmHg (mean: 146 +/- 17 mmHg) and average distal pressures from 15 to 150 mmHg (mean: 64 +/- 19 mmHg) were recorded. In the last 40 cases, the distal circulation was supplied through the left heart assistance device Bio-Medicus using minimal systemic heparinization (0.5 mg/kg), (target ACT > 150 seconds). Average pump flows from 1800 ml/min to 5200 ml/min. (mean: 3340 +/- 866 ml/min.) were obtained. Average proximal pressures from 90 to 200 mmHg (mean: 118 +/- 19 mmHg) and average distal pressures from 58 to 180 mmHg (mean: 95 +/- 24 mmHg) were recorded. Overall hospital mortality is 11.9% (50/420 cases) and 9.9% when ruptured aneurysms are excluded. Paraplegia occurred in 2 patients (0.4%) and one was related to an unfunctional Gott shunt. Adverse anatomical conditions like a proximal aneurysm, degenerative changes of the aortic wall, a previous proximal graft replacement or the presence of coronary artery bypass grafts, a friable wall encountered with dissecting aneurysms and also an adverse physiological condition like a left ventricular dysfunction prompted us to modify the circulatory support by using the left heart bypass. Comparison of both methods of perfusion supported by statistical analysis regarding shunt and pump flows, proximal and distal perfusion pressures has showed the physiological superiority of the centrifugal pump that we have now routinely adopted.