712 Abstracts

Tetraiodothyfromic acid is an effective anticholesterol agent which appears to be safe to use in patients with severe heart disease.

AUTOREGULATION OF INTESTINAL BLOOD FLOW. Paul C. Johnson, M.D., with the technical assistance of Stuart L. Graham. Indiana University School of Medicine, Indianapolis, Ind.

Previous experiments have shown that the arterial vessels of the intestine are responsive to changes in portal venous pressure, with pressure elevation causing arterial constriction. The purpose of this study was to determine whether these vessels respond in a similar fashion to changes in arterial pressure.

In thirty-nine pressure-flow studies on segments of terminal ileum, resistance to flow decreased with pres- sure reduction in 72 per cent of the experiments and In- creased in 28 per cent. The passive increase in re- sistance with pressure reduction was seen primarily shortly after the surgical procedure was completed. Thus, it appears that the arterial vessels of the intestine are not ordinarily passively distensible with changes in arterial pressure. As a result of this vascular reaction, the influence of arterial pressure on blood flow is at least partially counteracted. The mechanism of this autoregulation of flow is not a local reflex, a change in interstitial fluid volume or a change in tone of the in- testinal muscle. Changes in concentration of aerobic or anaerobic metabolites and oxygen tension of the t& sues were likewise eliminated. It is concluded that autoregulation of intestinal blood flow is a result of the sensitivity of vascular smooth muscle to change in arte- rial pressure [a myogenic response).

SURVEY OF THE PROBLEM OF PATENT DUCTUS ARTERIOSUS.

George Kaiser, M.D. Indiana University Medical Center, Indianapolis, Ind.

Over a ten-year period, no deaths followed ductal division in typical patients with no known pulmonary hypertension. The records of over fifty patients with known hypertension of varying degrees are reviewed. Success has been achieved in several with obvious re- versal. Three deaths occurred : one during postoperative bronchoscopy for atelectasis, two in patients believed to represent cases with retention of high fetal resistance (one at operation, one of unexplained cause on fourth postoperative day). No deaths occurred in twenty- two cases of coarctation and patent ductus. Also re- viewed are cases complicated by intracardiac shunt with and without coarctation.

RESULTS OF COMBINED TRANSTHORACIC LEFT AND PER-

CUTANEOUS RIGHT HEART CATHETERIZATION IN “ALVULAR

LESIONS OF THE LEFT HEART. Paul Kezdi, M.D., F.A.C.C. Chicago Wesley and Passavant Memorial Hospitals, and the Northwestern University Medical School, Chicago, Ill.

Combined left and right heart catheterizations were performed in 150 patients with lesions of the left side of the heart by the transthoracic approach and simulta- neous percutaneous catheterization of the right heart. The latter required no fluoroscopy. Cardiac output and pressure gradients were determined simultaneously and valvular areas were calculated. The largest single group studied had pure mitral stenosis. The rest had mitral stenosis and regurgitation, aortic stenosis, com-

bined aortic and mitral lesion and non-valvular heart condition in decreasing order. Valuable information was obtained supplementing the clinical findings and aiding the clinician in his decision in recommending surgical treatment. In a significant number of in- stances, the findings were contrary to the clinical im- pression. In combined valvular lesions, the predomi- nant lesion could be evaluated with great accuracy.

Characteristic hemodynamic changes of the dif- ferent valvular lesions obtained by left heart catheteriza- tion are discussed. Hemodynamic results of aortic valvotomy are presented in patients studied by left heart catheterization pre- and postoperatively.

Complications were relatively few and minor. There were no deaths and cardiac tamponade did not occur.

EXPERIMENTAL STUDIES WITH MITRAL VALVE REPLACE-

MENT. Harold Kiq, M.D. Indiana University Medical Center, Indianapolis, Ind.

To date, results of total replacement of a mitral valve leaflet with a plastic prosthesis have been dis ppointing. In contrast, results obtained with partial replacement of a mitral valve leaflet are encouraging.

HEMODYNAMIC EFFECTS OF BALLOON OBSTRUCTION OF THE

ABDOMINAL AORTA AND CLOSED-CHEST EXTRACORPOREAL

CIRCULATION IN EXPERIMENTAL MYOCARDIAL INFARCTION

wirn SHOCK. L&e A. Kuhn, M.D., F.A.C.C., Frank Gruber, M.D., Albert Franked, M.D. and Sherman Kujfu, M.D. The Mount Sinai Hospital, New York, N. Y.

The ability of extracorporeal circulatory support to produce a sustained increase in coronary perfusion pres- sure, and its effects on left ventricular work, cardiac output and systemic vascular resistance were investigated in closed-chest dogs with shock following plastic sphere coronary embolization.

In normal animals and in those with hypotension due to myocardial infarction, pumping of large volumes of blood (40 to 60 cc./kg./minute) from the venae cavae into the abdominal aorta failed to produce a rise in central aortic pressure. To raise central aortic pres- sure in these animals it was necessary to increase vascu- lar resistance. This was accomplished by inflating a balloon catheter inserted via a femoral artery into the abdominal aorta. Blood pumped from the superior vena cava supplied the distal aorta below the site of obstruction. In this manner, the circulation was “com- partmentalized,” leading to a rise in proximal aortic pressure with increased perfusion of the heart and the brain, and some diminution in distal aortic pressure. With this method, normal animals and those with myocardial infarction with shock demonstrated a sustained increase in central aortic (coronary perfusion) pressure and coronary flow, average central aortic mean pressure in twelve animals with shock rising from 73 to 133 mm. Hg. Left ventricular end diastolic and right atria1 pressures remained normal. Left ventricular work diminished or remained unchanged despite the rise in central aortic pressure, due to shunting of a portion of the venous return into the distal aorta.

It is concluded that conventional technics of extracor- poreal circulation, employing shunting from the veins to the abdominal aorta, are ineffective in raising coro- nary perfusion pressure unless there is severe congestive heart failure. To raise aortic pressure by mechanical means in experimental myocardial infarction with shock, it is necessary to increase vascular resistance.

THE AMERICAN JOURNAL OF CARDIOLOGY