Tag-along pacemaker.

In a R-wave-inhibited pulse generator, an increased interval between pacing artifacts giving an apparently slow rate was not indicative of impending battery failure in two patients. The pacing artifacts appeared as a tag-along phenomenon following a slow idioventricular rhythm as the result of an exit block due to (1) hyperkalemia and (2) perielectrode fibrosis. Simple tests demonstrated a normally functioning R-wave sensing circuit and pacemaker.

Chylopericardium with cardiac tamponade after cardiovascular surgery in two patients.

Two patients developed postoperative chylopericardium leading to acute cardiac tamponade. Delayed diagnosis and urgent throacotomy did not prevent death in three-month-old patient after the Glenn anastomosis of the superior vena cava to the right pulmonary artery, whereas early recognition of chylopericardium following repair of an interrupted aortic arch in an 11-week-old patient was successfully treated by tube pericardiostomy. The literature is reviewed, and an anatomic predisposition for post-surgical chylopericardium is proposed.

Changes in arterial pressure, viscosity and resistance during cardiopulmonary bypass.

Large changes in arterial pressure and systemic vascular resistance are frequently observed at the onset of and during cardiopulmonary bypass, particularly when hemodilution is employed. In order to assess the extent to which these changes are induced by changes in blood viscosity, we measured viscosity, pressure, and flow in a series of 17 patients. Hemodilution was used in Group A (12 patients) but not in Group B (5 patients). At the beginning of cardiopulmonary bypass, the arteriovenous pressure difference decreased an average of 53.8 per cent in the Group A patients, concomitant with a 41.7 per cent decrease in blood viscosity. The arteriovenous pressure difference in the Group B patients increased an average of 6.4 per cent, while the blood viscosity increased by 8 per cent. A nomogram was theoretically derived for the Group A patients, which allows rapid estimation of the extent of viscosity-induced hypotension for a given volume of priming fluid, initial patient hematocrit, and patient weight. After correction for viscosity changes due to hemodilution, the Group A patients were found to exhibit essentially normal values of systemic vascular resistance at the start of bypass, with a mean of 1,155 dynes-sec./cm.5. On the other hand, the Group B patients had elevated resistance values, with a mean of 1,611 dynes-sec./cm.5. During perfusion, the resistance of both groups tended to increase, sometimes by 100 per cent or more. In some cases, however, the resistance values changed in an erratic fashion. These effects were not due to changes in blood viscosity.

Post-traumatic intracardiac shunts. Report of two cases and review of the literature.

Intracardiac shunts consequent to penetrating thoracic injury have been reported in 94 patients. Two additional cases are reported emphasizing the frequently complex anatomic abnormalities, the variability in clinical course, and the favorable outcome of repair. From a review of the literature, it is apparent that most such lesions should be corrected, since patients are at a continual risk of symptomatic cardiac dysfunction and repair offers an excellent prognosis with minimal morbidity.

Allograft replacement of the aortic valve versus the miniroot and valve.

Between February 1986 and April 1992, 27 patients ranging in age from 8 to 65 years (median, 18 years) underwent allograft replacement of the aortic valve with one death (operative mortality, 3.7%). The indications for operation were aortic regurgitation in 14 patients, aortic stenosis in 7, aortic stenosis/regurgitation in 4, and endocarditis in 2. Associated lesions included annuloectasia in 4 patients (1 with Marfan's syndrome), sinus of Valsalva aneurysm in 3, coronary artery disease in 4, and ventricular septal defect in 2. The freehand technique was used in 12 patients and the miniroot replacement in 15 patients. The postoperative transvalvular gradient was 17 mm Hg in freehand valves and 7 mm Hg in the miniroot valves. Initial postoperative study showed no or trivial aortic regurgitation in all 26 survivors except 1 freehand patient who had mild aortic regurgitation. At late study up to 6 years postoperatively all 10 of our available freehand patients showed progressive regurgitation, and it was severe in 4 patients. By contrast only half of the miniroot patients showed progressive regurgitation, and in none was it severe. Allograft replacement of the aortic valve can be done in children and adults with low mortality rate, short hospital stay, and excellent early function. Subsequent follow-up studies suggest that the miniroot replacements are superior to the freehand valves with lower transvalvular gradients, less valvular regurgitation, and delayed progression of valvular regurgitation.

Intraoperative Doppler coronary artery finder.

Time-consuming difficulty is occasionally encountered in finding coronary arteries or previously placed vascular grafts during coronary revascularization procedures. A catheter-tipped, continuous-wave Doppler ultrasonic probe with simple audio output has been shown to be capable of expediting the search for these vessels.