An appraisal of blood trauma and blood-prosthetic interface during left ventricular bypass in the calf and humans.

Mechanical circulatory support was accomplished in 20 calves (mean, 140 days) and in 5 patients following operation for acquired heart disease (range, 1 hour to 8 days) employing a pneumatically actuated xenograft-valved assist pump interposed between the left ventricular apex and aorta. Following pump implantation in calves, hematocrit and platelets decreased transiently and returned to normal within 14 days. Plasma hemoglobin and erythrocyte mechanical fragility values were elevated for 48 hours. Platelet survival was slightly reduced, but erythrocyte survival values were similar to controls. In patients who received assist pumps, plasma hemoglobin and erythrocyte mechanical fragility were transiently elevated, but rapidly decreased to normal. Thrombocytopenia occurred only in the presence of bleeding and renal failure requiring hemodialysis. Pump flow of the left ventricular assist device was maintained above 2.0 L/min/m2 despite serious arrhythmias. Postmortem examination revealed no evidence of thromboemboli in the clinical patients although anticoagulant agents were not administered.

Quantitative radionuclide angiocardiography. Determination of left ventricular ejection fraction in children.

A method is described for measuring left ventricular ejection fraction which uses high frequency computer recording of gamma scintillation camera data and peripheral venous injectinon of technetium-99m as sodium pertechnetate. Data from mechanical model experiments are used to show feasibility of this method. A phantom experiment is described which was used to develop a technique for accurate delineation of the ventricular outline in the presence of background. The left ventricular ejection was measured in 12 patients by radionuclide angiocardiography and biplane cineangiography. Comparison of these two methods gave a correlation coefficient of 0-91. In addition, left ventricular ejection fraction was measured in 34 patients (aged 7 weeks to 18 years) without evidence of cardiac disease using the radionuclide method alone. Average ejection fractions of 0-66 and 0-70 were found for children over 2 years of age and children 2 years of age or younger, respectively. In addition, an interobseerver comparison study was performed with the data from 10 patients, and only small differences were noted (SD 0-025).

The surgical management of discrete and diffuse supravalvar aortic stenosis.

Between 1956 and 1976, 18 patients underwent surgery for supravar aortic stenosis at the The Children's Hospital Medical Center, Boston. Discrete obstruction, present in 11, was treated by insertion of a prosthetic gusset placed across the area of narrowing and extending into the noncoronary sinus of Valsalva. There was one operative death. Residual gradients (measured in five patients) ranged from 4-55 mm Hg, one of which was supravalvar in location. Significant aortic regurgitation was not common preoperatively. The diffuse form of supravalvar obstruction, a more difficult surgical problem, was present in seven patients. There were three operative deaths. Complete relief of the pressure gradient was achieved only in one instance by insertion of a left ventricular-aortic bypass shunt diverting the majority of the cardiac output into the descending thoracic aorta. This patient is now asymptomatic 20 months following operation. On the basis of this experience, it is suggested that patients with the diffuse form of supravalvar obstruction, and perhaps even those with a hypoplastic annulus alone, would benefit from a left ventricular-aortic bypass shunt.

Quantitative radionuclide angiocardiography: detection and quantitation of left to right shunts.

In 105 patients defection and quantitation of left to right shunts was performed using quantitative radionuclide angiocardiography. The radionuclide angiocardiograms were acquired and analyzed by a gamma camera interfaced to a digital computer system. Pulmonary to systemic flow (Qp/As) ratios were calculated by analysis of pulmonary time-activity histograms using a gamma variate model. All patients were studied with cardiac catheterization, left ventricular angiocardiography and radionuclide angiocardiography. The radionuclide method allowed precise detection and quantitation of left to right shunts with a Qp/Qs ratio of 1.2 to 3.0. There was good agreement between the Ap/As ratio calculated by oximetry at cardiac catheterization and radionuclide angiocardiography (r = 0.94). The information gathered with this nontraumatic method appears sufficiently reliable to be used in the management of patients.

Relief of congenital obstruction to left ventricular outflow with a ventricular-arotic prosthesis.

Hypoplasia of the aortic valve annulus and ascending aorta is a rare form of congenital aortic stenosis, with a poor prognosis. Replacement of the aortic valve and ascending aorta with a suitable prosthesis is feasible, but the hypoplastic valve annulus must also be enlarged if an adult-sized aortic valve is to be placed in the subcornary position. In an effort to develop a new method of surgical treatment for this congenital abnormality, we fabricated a prosthesis which can be interposed between the left ventricular apex and descending thoracic aorta. This prosthesis is coupled to a 25 mm. Dacron graft and xenograft valve and is lined with flocked Dacron fibrils to encourage formation of a stable biologic lining and prevent thrombus buildup. The prosthesis was implanted in a 22 year old male patient of the Children's Hospital Medical Center without difficulty. Postoperative cardiac catheterization idicated that all of the contrast material was ejected from the left ventricle through the prosthesis. The patient was discharged from the hospital taking sodium warfarin and remains entirely asymptomatic.

Transmural coronary venous O2 saturations in normal and isolated hearts.

Blood O2 saturations were measured by microscopic oximetry in the small coronary veins of wither open-chest or isolated and blood-perfused dog hearts. Subendocardial saturations (average 34%) were significantly lower than subepicardial (average 52%) in isolated hearts contracting isovolumically at systolic and coronary perfusion pressures of 100 mmHg. Saturations of botb regions fell and were not significantly different from each other (both averaged 16%) with partial coronary occlusion. When MVo2 was increased by calcium infusion, subendocardial saturations fell sharply to about 2% and were significantly, lower than subepicardial (average 10%). Conversely, when MVo2 was decreased by ventricular decompression, saturations rose equally in subendocardium (average 40%) and subepicardium (average 45%) (not significant). These data illustrate the efficacy of cascular autoregulation in isolated hearts. In open-chest dogs, as in isolated hearts with partial coronary occlusion, subendocardial (average 20%) saturations were not significantly diffenent from each other and ranged from 0 to 70%, suggesting the possibility of significant differences either in regional coronary flow or MVo2, or both, in closely adjacent areas throughout the myocardium.

The Anrep effect reconsidered.

Evidence is presented supporting the hypothesis that the positive inotropic effect after an abrupt increase in systolic pressure (Anrep effect) is the recovery from subendocardial ischemia induced by the increase and subsequently corrected by vascular autoregulation of the coronary bed. Major evidence consists of data obtained from an isolated heart preparation showing that the Anrep effect can be abolished with coronary vasodilation, and that with an abrupt increase in systolic pressure there is a significant reduction in the distribution of coronary flow to subendocardial layers of the ventricle. Furthermore, the intracardiac electrocardiogram shows S-T segment and T wave changes after an abrupt increase in ventricular pressure similar to that noted after coronary constriction. Major implications are that normally there may be ischemia of the subendocardial layers tending to reduce myocardial contractility which may account, in part, for the positive inotropic effect of various coronary vasodilators; that with an abrupt increase in ventricular pressure the subendocardium is rendered temporarily ischemic, placing the heart in jeopardy from arrhythmias until this is corrected; and that end-diastolic pressure and the intracardiac electrocardiogram may provide a means of evaluating the adequacy of circulation to subendocardial layers in diseased ventricles when systolic pressure is abruptly increased.

Left ventricular performance and coronary flow after coronary embolization with plastic microspheres.

Coronary flow, left ventricular circumference, and left ventricular pressure were observed in the isovolumically contracting, isolated canine heart supported with arterial blood from a donor. Systolic pressure, heart rate, and coronary perfusion pressure were held constant while the coronary bed was progressively embolized with either large (average 865 mu) or small (average 10 mu) polystyrene microspheres. During embolization with large microspheres, coronary flow diminished progressively. After sufficient embolization, decreased ventricular performance was indicated by a rise in end-diastolic pressure. During embolization with small microspheres, coronary flow initially increased, which suggests the effective release of a vasodilator substance. Return of coronary flow to control levels occurred only after the end-diastolic pressure rose, on the average, to above 30 mm Hg. After embolization with both sizes of microspheres, ventricular diastolic pressure-volume relationships showed decreased ventricular compliance. This was attributed, in part, to edema of the ventricular wall and, in part, to focal shortening of the sarcomeres where the circulation was compromised. Embolization with both sizes of microspheres ultimately caused a decrease in ventricular performance, although when the systolic pressure was increased the usual relationship between peak developed wall stress, and end-diastolic pressure showed less of a descending limb than that found in the nonembolized, isolated heart. It is felt that the data summarized above have bearing on ventricular performance and coronary flow in clinical situations where hearts are perfused through pump oxygenator systems and are thereby subject to embolization from aggregated clumps of platelets and fibrin.