HEMODYNAMICS DURING THE CHRONIC STAGE OF MYOCARDIAL DAMAGE CAUSED BY ISOPROTERENOL

Cardiovascular measurements were performed in rats 3–4 days, 1 week, 2 weeks, 5–6 weeks, and 4–5 months after the subcutaneous injection of 40 mg/kg isoproterenol on two consecutive days. Up to 1 week after the injections severe histological damage of the myocardium was accompanied by cardiac enlargement and impaired function: blood pressure, cardiac output and work were in the normal range under basal conditions but the maximum cardiac output and work measured during infusion of polyvinylpyrrolidone into the right side of the heart were well below normal. During the following weeks histological repair took place and the cardiovascular parameters measured were not different from those found in normal rats. This period was followed by a third stage which occurred without further interference with the heart. It consisted of thinning of the ventricular wall and aneurysm formation. All cardiovascular values (maximum and basal as well) were below normal without development of cardiac enlargement.

THE EFFECT OF NITROGLYCERIN ON LEFT VENTRICULAR WALL TENSION IN FIXED ORIFICE AORTIC STENOSIS

Symptoms of myocardial ischemia occur in aortic stenosis in the absence of coronary artery disease. Increased left ventricular wall tension, a principal determinant of myocardial oxygen requirements, may contribute to these symptoms. This investigation was undertaken during the course of transseptal left heart catheterization in order to study the effect of nitroglycerin on left ventricular wall tension in eight patients with fixed orifice aortic stenosis. In seven of the subjects, nitroglycerin significantly reduced tension-time index per beat and per minute. In addition, left ventricular size may have diminished as a consequence of lower diastolic filling pressure. In view of the relationship between wall tension and myocardial oxygen consumption, these effects should favorably influence the balance between oxygen availability and oxygen requirements in patients with fixed obstruction to left ventricular outflow. The eighth patient experienced an appreciable increase in tension-time index, suggesting secondary hypertrophic subaortic stenosis.

ACUTE AND CHRONIC EFFECTS OF THE INSECTICIDE ENDRIN ON RENAL FUNCTION AND RENAL HEMODYNAMICS

Variable effects of chlorinated hydrocarbon insecticides on the kidney have been reported. The purpose of the present study was to determine the acute and chronic effects of the insecticide endrin on renal function and hemodynamics in dogs. Dogs were exposed to endrin acutely by intravenous infusion, and chronically by intramuscular injection. In acute experiments, dogs developed systemic hypertension and increased renal vascular resistance attributable to a sympatho-adrenal action. Acute effects of endrin were predominantly afferent arteriolar vasoconstriction as evidenced by decreases in renal blood flow, glomerular filtration rate, and urine flow. Phentolamine and phenoxybenzamine increased renal blood flow after endrin, providing evidence for humorally induced renal vasoconstriction due to adrenergic agents. Adrenalectomy partially offset the marked drop in renal blood flow after endrin although systemic hypertension and bradycardia were unaffected. Results from renal denervation experiments were variable. Changes in renal function in chronic studies were minimal and appeared to be due to secondary alterations in systemic hemodynamics. Results from this investigation provide no evidence for renal failure attributable to the direct effects of endrin.

COR TRIATRIATUM AS A PROBLEM OF ADULT HEART DISEASE

The occurrence of severe pulmonary venous obstruction due to the congenital anomaly known as cor triatriatum in a 19-year-old furniture mover is described. Relentless and massive hemoptysis led to pulmonary edema, and an attempt at surgical correction under unfavorable conditions was not successful.

Seven other cases of cor triatriatum in adults are reviewed. The hemodynamic abnormalities closely resemble mitral stenosis, except that pressures in the true left atrium were normal in the presence of elevated pulmonary capillary pressures. The availability of flow across the obstructing membrane during systole as well as diastole is probably the major element in the surprisingly good tolerance of severe degrees of anatomic obstruction for long periods of time. Slow increase in the degree of obstruction could also be a factor.

The clinical picture in these patients very closely resembles mitral stenosis. Hemoptysis appeared to be more frequent in cor triatriatum. Features suggestive of the correct diagnosis would include the absence of an opening snap, the absence of a typical murmur of mitral stenosis, regular rhythm, and lesser evidence of left atrial enlargement in the presence of obvious pulmonary hypertension. Five of these patients have undergone successful correction of their disease by operation.

Representative films from the first known angiograms in this condition in an adult are reproduced and discussed.

OBSERVATIONS ON THE RELATION BETWEEN VENTRICULAR ACTIVATION SEQUENCE AND THE HEMODYNAMIC STATE

Hemodynamic parameters including records of left and right ventricular pressure, aortic pressure, the first derivative of the left ventricular pressure curve, and carotid flow were recorded with different patterns of ventricular activation. Special measures were used to achieve a comparable role of the atrium in ventricular filling with the different ventricular activation patterns.

With an intact cardiac conduction system, definite but small differences in the hemodynamic parameters named were associated with different activation patterns. Normal ventricular activation produced slightly higher peak pressures in both ventricles and higher carotid flow than did abnormal activation. Each different activation pattern was associated with differences in the detailed shape of the ventricular pressure curves and with differences in the relative time of onset of pressure rise in right and left ventricles. When the specialized conduction system was blocked with large doses of ouabain, various patterns of ventricular activation were associated with marked differences of the hemodynamic parameters named. These findings may explain previously published conflicting results. They also suggest that disease of the conduction system may have a significant functional role in cardiac disease.

INTERVENTRICULAR SEPTAL DEFECT: ANALYSIS OF 415 CATHETERIZED CASES, NINETY WITH SERIAL HEMODYNAMIC STUDIES

Four hundred fifteen patients with interventricular septal defect, proved at cardiac catheterization, have been followed for 1,407 patient years. As a group, they demonstrated marked growth failure in early childhood, which was more striking for weight than height. Ninety patients had serial hemodynamic studies without intervening cardiovascular surgery. Eight demonstrated spontaneous functional closure of their defect; only one progressed to the Eisenmenger syndrome. No patient with initially normal pressure developed pulmonary hypertension. Patients with initial pulmonary hypertension more commonly demonstrated regression than progression of the hypertension. Six patients developed bacterial endocarditis; all recovered. There was a frequent association (11 per cent) between interventricular septal defect and right ventricular outflow obstruction. Some patients developed increasing right ventricular outflow obstruction during the study. Eighteen patients with predominant right-to-left shunt were studied. Seventeen were cyanotic at the time of the initial study. The incidence of cyanosis was equal in the two sexes but females developed it later in life than males.

Twenty-nine patients have died. Twenty-two deaths resulted from operative procedures; seven from the natural course of the disease. The principal factors associated with operative mortality was the presence of pulmonary hypertension and surgical repair before age 5. There were no operative deaths in patients with pulmonary artery systolic pressure below 65 mm. Hg. One patient died of progressive pulmonary hypertension 6 years after successful surgical closure of his defect.

There is a great need for more information concerning the natural course of this disease in all age groups, both in the unoperated patient and in patients whose defects have been surgically closed.

MECHANISMS REGULATING ALDOSTERONE SECRETION DURING SODIUM DEPLETION

Steroid secretion was studied in conscious dogs before and during 4 days of Na depletion. A threefold increase in aldosterone secretion occurred but corticosterone output was unchanged. Plasma renin was markedly elevated. Plasma Na and K concentrations were unchanged until the 4th day of Na depletion at which time plasma Na was decreased and plasma K was elevated. The Na content of the adrenal cortex expressed as fat-free tissue solids was decreased. It seems likely that the adrenocortical Na loss was extracellular; adrenocortical K content was unaltered. It is suggested that the normal rate of corticosterone secretion during Na depletion is maintained by a negative corticosteroid feedback mechanism, since corticosterone output was consistently increased in Na-depleted hypophysectomized dogs. Aldosterone secretion was three times as great in the presence as in the absence of the anterior pituitary during Na depletion. It is concluded that increased activity of the renin-angiotensin system is the primary mechanism leading to hyperaldosteronism during Na depletion and that the adenohypophysis plays an important supportive role.

LEFT VENTRICULAR HEAT PRODUCTION DURING INDUCED TACHYCARDIA IN THE INTACT DOG

It is well established that heart rate is a determinant of myocardial oxygen consumption. However, it has not been demonstrated that the increase of oxygen consumption at faster rates actually represents loss of energy, degraded as heat. Control measurements of systemic and coronary hemodynamic and metabolic parameters and left ventricular heat production (measured by a recently reported method) were obtained in 10 dogs. Tachycardia was then induced electrically and the same parameters redetermined. Significant increases occurred in coronary blood flow, cardiac metabolic rate of oxygen, and left ventricular heat production. The elevated myocardial oxygen consumption at higher rates is associated with increased heat production.

HEMODYNAMIC ASPECTS OF PROLONGED INFUSION OF ANGIOTENSIN INTO UNANESTHETIZED DOGS

Arterial pressure, cardiac output, stroke volume, heart rate, and peripheral resistance have been recorded daily in eight trained, healthy dogs with implanted aortic flow probes and aortic catheters. After suitable control periods angiotensin II was infused for periods of from 2 to 29 days.

The effects observed were considered under four categories: 1) The immediate effects consisted of rise of arterial pressure, decrease of cardiac output and heart rate, rise of peripheral resistance and increased pulse pressure. Within five days all values tended to return to control levels unless the infusion rate of angiotensin was increased. 2) A chronic phase followed and, during this period, cardiac output was normal while arterial pressure and peripheral resistance were elevated. 3) After infusions were stopped pressure and peripheral resistance rapidly declined to be low normal, while cardiac output and heart rate rose to above normal. 4) A transient "malignant" phase was elicited by very large increases in the rate of angiotensin infusion, during which cardiac output and stroke volume were diminished while arterial pressure and peripheral resistance were increased greatly.

The hemodynamic changes resulting from prolonged angiotensin infusion were similar in some respects to those found by us during the onset of hypertension due to renal artery constriction in dogs. They differed, however, in that doses of angiotensin, which were great enough to induce arterial pressure elevations similar to those of chronic experimental renal hypertension, reduced stroke volume, and these higher pressures could not be maintained for more than a few days. Hypertension did not persist after discontinuing angiotensin even after 28 days of almost continuous infusion. There was a distinct tendency for the pressor response to diminish with passage of time; more angiotensin was required to maintain similar elevations of arterial pressure.

COMPARATIVE CARDIOVASCULAR EFFECTS OF TYRAMINE, EPHEDRINE, AND NOREPINEPHRINE IN MAN

The systemic hemodynamic and forearm vascular effects of tyramine, ephedrine, and norepinephrine were studied in normal male subjects. The pressor effect of tyramine was associated usually with bradycardia, unchanged cardiac output, and moderate arteriolar constriction in the forearm. A similar pressor effect of ephedrine was characterized by an increase of heart rate and output, with a slight fall in forearm vascular resistance. Occasional subjects responded to tyramine with an increase of cardiac output and a fall in forearm vascular resistance, and to ephedrine, with a marked increase of vascular resistance. The pressor effect of norepinephrine was associated always with bradycardia and with marked arteriolar and venous constriction in the forearm.

Brachial arterial infusions of the drugs in nonpressor doses confirmed the vascular effects. Norepinephrine produced dose-dependent forearm constriction in all subjects, while vasodilatation was observed occasionally with tyramine and frequently with ephedrine.

The demonstrated differences in local vascular and systemic hemodynamic effects of these drugs suggest some inconsistency in the hypothesis that the effect of either ephedrine or tyramine is mediated exclusively by norepinephrine release.

THE STRAIGHT BACK SYNDROME: CLINICAL CARDIOVASCULAR MANIFESTATIONS

Analysis of the cardiovascular manifestations caused by loss of thoracic kyphosis has been incomplete. Accordingly, this study was designed to investigate the physical signs and the electrocardiographic, radiologic, hemodynamic, and pulmonary ventilatory features of this skeletal defect. Twenty-three patients with straight thoracic spines in lateral chest x-rays were selected. Ratios of anteroposterior to transthoracic dimensions were uniformly below a mean derived from 100 normal subjects. Cardiac features included pulmonic ejection murmurs, palpable left parasternal systolic impulses, loud delayed sounds of tricuspid valve closure, exaggerated respiratory splitting of the second heart sound, vertical electrical axes, rSr' patterns in leads V 1 or aV R , radiologic prominence of the pulmonary arteries, levodisplacement of the heart, a "pancake" cardiac configuration simulating cardiomegaly, occasional alterations in height or contour of the right ventricular diastolic pressure pulse, and an occasional mild pulmonary ventilatory restrictive defect. Differential diagnoses principally included atrial septal defect, mild pulmonic stenosis, and idiopathic dilatation of the pulmonary artery.

A STUDY OF HEPATIC HEMODYNAMICS IN THE DOG

The effects of altered hepatic blood flow, of splanchnic and hepatic nerve stimulation, and of injecting epinephrine and vasopressin (Pitressin) were studied by perfusing canine livers in vitro. Controlled hepatic arterial perfusions demonstrated a linear relationship between arterial pressure and hepatic arterial inflow. It was found that increases of hepatic artery flow slightly increased portal vein pressure and vascular resistance of the portal vein, and that increases of portal vein flow slightly increased hepatic artery vascular resistance. Splanchnic nerve stimulation caused vasoconstriction of the hepatic artery, portal vein, and mesenteric vasculature. Hepatic nerve stimulation caused constriction of only the hepatic artery and portal vein vasculature. Similar results were obtained by the administration of epinephrine. Pitressin caused marked vasoconstriction of the mesenteric vasculature, vasodilatation of the portal vein vascular bed, and slightly increased hepatic artery vasomotor tone. It was noted that the rise in portal vein vasomotor tone with sympathetic stimulation was due in part to constriction of the "postjunctional" resistance.