Theofilos J. Tsagaris

Hemodynamic effects of exercise in patients with aortic stenosis

Abstract Hemodynamic data obtained by right and left heart catheterization at rest and during exercise in thirty-two patients with aortic stenosis were reviewed. Eighteen patients had either minimal or no aortic regurgitation (group I) and fourteen patients had moderate to moderately severe aortic regurgitation (group II). The mean systolic pressure gradient (ΔP) across the aortic valve decreased or remained unchanged during exercise in eleven of eighteen patients in group I and in nine of fourteen patients in group II. Net forward aortic valve systolic flow (AVSF) increased during exercise in fourteen of eighteen patients in group I and in thirteen of fourteen patients in group II. Thus, in some patients the change in ΔP during exercise appears to be at variance with the predictability implied by the Gorlin equation which states that ΔP should be directly related to (AVSF) 2 . It is unlikely that this discrepancy can be explained on the basis of a systematic measuring error involving one or more of the various factors in the equation. This suggests that the aortic valve may not behave as a fixed orifice under all hemodynamic conditions, and that orifice hydraulics might be different depending on the mechanics of contraction. Average cardiac index (CI) was 2.5 L. per minute per M 2 . at rest and 3.8 L. per minute per M 2 . during exercise for patients in group 1, and 2.2 L. per minute per M 2 . at rest and 3.9 L. per minute per M 2 . during exercise for patients in group 2. Arterial and left ventricular systolic and diastolic pressures increased, and systemic resistance decreased during exercise. Thus, resting cardiac output is maintained and it increases during exercise at the expense of marked elevation in both systolic and diastolic pressures in the left ventricle. An analysis of the relationship between stroke work index (SWI) and left ventricular end diastolic pressure (LV edp ) in patients from group I revealed, in general, two types of responses to exercise. Six patients had an increase in SWI averaging 39 per cent associated with a 67 per cent increase in LV edp . In sharp contrast, ten other patients demonstrated an increase in SWI averaging only 1.3 per cent whereas LV edp increased by an average of 129 per cent. It is apparent therefore that the response to exercise makes it possible to separate patients with remaining myocardial reserve from those without. Thus, exercise data in patients with aortic stenosis provide objective, quantitative information useful in making a decision when and if to perform corrective surgery.

Effects of prostaglandins F2a and E2 on the bovine circulation.

Summary The effects of PGF2α and PGE2 on the pulmonary and systemic circulations were studied in unanesthetized calves. PGF2α, average dose 2.1 μg/kg, injected into the pulmonary artery resulted in a significant increase in PA pressure and fall in CO whereas FA pressure, LV end diastolic pressure, HR, blood gases and pH were not significantly altered. PGE2, average dose 1.9 μg/kg, injected into the pulmonary artery resulted in a significant decrease in FA pressure, increase in HR and a small but significant increase in PA pressure whereas LV end diastolic pressure, CO, blood gases and pH were not significantly altered. Thus, this study indicates that in the bovine PGF2α causes pulmonary vasoconstriction and PGE2 causes systemic vasodilatation. The authors are indebted to Dr. J. E. Pike of the Upjohn Company for generous supplies of prostaglandins. The technical assistance of Mr. Don Anton and Filimon Ukradyha, PhD, is greatly appreciated.

BRISKET DISEASE. III. SPONTANEOUS REMISSION OF PULMONARY HYPERTENSION AND RECOVERY FROM HEART FAILURE.

Previous reports from this laboratory have dealt with the ecologic, pathologic, clinical, and pathophysiologic features of brisket disease (1, 2). On the basis of these studies brisket disease may be defined as altitude-dependent, pulmonary, hypertensive heart disease in cattle of the species Bos taiurus. Briefly, the disease in Utah occurs primarily in young calves usually during their first exposure to conditions existing on summer ranges at elevations between 8,000 and 11,000 feet. Typical findings in animals suffering from brisket disease are outlined in Table 1. It was observed that a significant number of animals with acute brisket disease recovered when removed from the mountainous ranges and brought to Salt Lake City, Utah (elevation 4,500 feet). This observation prompted an investigation of the nature, magnitude, and time course of changes in various physiologic parameters associated with clinical recovery. The demonstration of dramatic remission from pulmonary hypertension and improvement in over-all cardiovascular function provides the basis for this report.

Coronary Artery Aneurysm and Subacute Bacterial Endarteritis

Excerpt Recent reviews dealing with congenital coronary arteriovenous aneurysms attest to the increasing interest in this malformation (1-5). Examples reported prior to 1947 were discovered only du...

Evidence for Pulmonary Venoconstriction in Brisket Disease

Measurements were made of simultaneous pulmonary artery wedge (PAw) and left ventricular diastolic (LVed) pressures 39 times during 21 venous and left ventricular cardiac catheterization studies in eight animals with brisket disease. Each animal was studied during the acute phase of the disease. The remaining 13 studies were carried out in six animals at various intervals during spontaneous recovery from pulmonary hypertension and heart failure. A pressure gradient between PAw and LVed (δP) which averaged 14.6 ± 1.6 (SE) mm Hg was demonstrated in 12 measurements during seven studies in four animals (group A). The δP in 27 measurements during 14 studies in six animals averaged 2.4 ±0.8 mm Hg (group B). Venous resistance (Rv) represented 39±5% of the total resistance (RT) of pulmonary vessels in group A and 13±4% in group B studies. The δP and Rv/RT in group A animals are consistent with findings caused by pulmonary venous obstruction. The obstruction was interpreted to represent the effect of pulmonary venoconstriction.

Computer Estimation of Stroke Volume from Aortic Pulse Contour in Dogs and Humans

Stroke volume (SV) estimation from computer analysis of aortic pressure contour was tested in 12 anesthetized dogs and 2 humans with A-V block. The ‘actual’ SV was calculated from right-heart bypass pump flow values in 6 open-chest dogs, from heart rate (HR) and cardiac output (CO) using dye dilution in 6 closed-chest dogs and by the Fick method in the human subjects. SV changes were induced by changes in pacing rate and pump flow, infusion and withdrawal of fluids and exercise. Mean arterial pressure was altered in dogs by changes in CO and infusions of drugs.In the dogs, the method (using Warner’s formula) proved consistent (r = 0.774, p y. x = 3.82 ml) but inaccurate (slope = 0.386) in 627 comparisons. The same conclusions were reached in 11 human comparisons. The Kouchoukos formula showed similar problems. Corrections are suggested based on these results.

Rest and Exercise Hemodynamic Studies in Patients with Isolated Aortic Stenosis

Hemodynamic data obtained during rest and exercise in 22 patients with aortic stenosis were analyzed. Mean aortic valve gradient for the group did not change significantly during exercise but there was large individual variability. Aortic valve flow increased during exercise in all but 2 patients. There was no correlation between change in gradient and change in flow during exercise. Although the mean calculated aortic valve area for the group did not change significantly during exercise, the calculated area was larger during exercise in most patients. Change in the calculated valve area correlated best with changes in aortic valve flow, left ventricular stroke work index, and the product of left ventricular systolic pressure and stroke volume. This suggests that in some patients there may be a dynamic component to aortic valve obstruction that may vary with changing hemodynamics.

Influence of adrenergic drugs on prostaglandin E release from the dog kidney

Summary PGE levels in renal venous blood of in situ perfused dog kidneys were measured by radioimmunoassay. A basal efflux of PGE was found and a significant increase in the levels was elicited by injection of norepinephrine or epinephrine into the renal arterial circulation. Isoproterenol had a small but possibly unimportant effect, α-adrenergic blockade with phen-oxybenzamine did not inhibit the PGE increase but did block the pressor response to norepinephrine and epinephrine. Thus, PGE release in these experiments was apparently not dependent on total renal blood flow or perfusion pressure. Acetylsalicylic acid and indomethacin blocked the PGE response to norepinephrine and epinephrine but did not affect the pressor response suggesting that PGE synthesis rather than the release of stored PGE occurs when α-adrenergic drugs are administered. Our findings lend support to the suggestion that PGE may play a physiologic role in the intrarenal vascular adjustments.

Left Main Coronary Artery Occlusion

Patients with complete occlusion of the left main coronary artery are candidates for massive myocardial infarction and sudden death and are thought to have a uniformly poor prognosis. Complete occlusion of the left main coronary artery was identified in 2 male patients among 2,546 patients undergoing cardiac catheterization over a period of 14.5 years in our institution. Both patients had angina pectoris. Left ventricular end-diastolic pressure was markedly elevated in one, and the ejection fraction was moderately to markedly reduced in both. Significant collateral flow to the left coronary system from the right coronary artery was present in both patients. Our study supports previous reports that left main coronary artery occlusion is rarely encountered during cardiac catheterization.

Hemodynamic Effects of Small Amounts of Endotoxin in the Bovine

Summary The effects of 1–10 μg/kg Escherichia coli endotoxin on the pulmonary and systemic circulations were studied in unanesthetized calves. Typically, no change in hemodynamic variables occurred until 8 min had elapsed, after which there was a significant increase in PA pressure and heart rate, a decrease in FA pressure and CO, with no change in LV diastolic or PAW pressures. Arterial pO2 decreased and pH increased slightly. In calves pretreated with either ASA or IM, endotoxin produced no significant change in PA, PAW, FA, or LV diastolic pressures, CO or HR. Continuous inhalation of 100% O2 did not modify the effect of endotoxin. Thus, this study indicates that the bovine pulmonary circulation is exceedingly sensitive to minute amounts of endotoxin. The mechanism whereby this response occurs is not clear.