Subendocardial Distribution of Coronary Blood Flow and the Effect of Antianginal Drugs

Moir, Thomas W.

doi:10.1161/01.res.30.6.621

Cited by 158 publications

(47 citation statements)

References 47 publications

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“…Studies were performed on 30 mongrel dogs, whose weights averaged 21.2+0.7 (SE) kg. The animals had been screened for mcrofilariae, medicated against rabies and intestinal parasites, and maintained on a nourishing diet for at least 30 days.…”

Section: Methodsmentioning

confidence: 99%

“…The underlying basis for subendocardial underperfusion is considered by most investigators to be related to a systolic intramyocardial tissue pressure gradient which increases from epicardium to endocardium (8). A current hypothesis is that flow is normally less in the subendocardium during systole due to this pressure gradient, but greater in the subendocardium during diastole due to autoregulation of flow by coronary resistance vessels (21) The previous studies raised an important question concerning the adequacy of subendocardial flow in aortic insufficiency, and one of the main purposes of the present investigation was to obtain information bearing on this question. It was felt that information on regional tissue flow would not permit a reliable assessment of the nutritional adequacy of such flow because oxygen consumption of the ventricle is reported to be increased in aortic insufficiency (14).…”

Section: Methodsmentioning

confidence: 99%

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Coronary Hemodynamics and Regional Myocardial Metabolism in Experimental Aortic Insufficiency

Griggs¹,

Chen²

1974

J. Clin. Invest.

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ABSTRA CT Acute aortic valvular insufficiency was induced in open chest dogs by employing a special intravascular cannula, or by rupturing an aortic valve leaflet. Phasic and mean coronary flow were assessed in some animals, while in others data were obtained on arterial and coronary sinus blood lactate, pyruvate, Po2, Pco2, and pH, and on myocardial tissue lactate, pyruvate, and water content in the outer and inner halves of the free wall of the left ventricle. Results showed that in acute aortic insufficiency diastolic coronary flow decreased as a function of aortic diastolic pressure, but systolic coronary flow increased in such proportion that mean coronary flow did not decrease. With moderate reductions in aortic diastolic pressure due to aortic insufficiency, myocardial blood flow was judged to be nutritionally adequate in both the outer and inner regions of the left ventricle. With more severe reductions in aortic diastolic pressure, the inner region exihibited biochemical signs of anaerobic metabolism. The presence of these metabolic changes could be correlated with either of two previously described pressure indexes. These findings suggest that the reduced coronary perfusion pressure and the intramyocardial tissue pressure gradient can be compensated for by autoregulation in some cases of aortic insufficiency, but in others such compensation may be incomplete, in which case oxygen delivery to the subendocardium will be inadequate to meet local tissue oxygen needs. INTRODUCTIONIt is apparent from the high incidence of angina pectoris in patients with severe aortic insufficiency (1) December 1973. this is related to the low perfusion pressure in the coronary circulation during diastole-the time when coronary flow is normally greatest-and the greater than normal energy requirements of the hyperfunctioning left ventricle. Recently, Buckberg, Fixler, Archie, and Hoffman (2) demonstrated that when aortic diastolic pressure was lowered in the dog by opening a large arteriovenous fistula, blood flow in the wall of the left ventricle became uneven and lower in the subendocardium than the subepicardium. They correlated the regional flow changes with a special pressure index they developed to assess the balance between oxygen supply and demand in the subendocardium. It was not possible, however, to determine from the flow data or the pressure index to what extent, if any, the metabolic needs of the subendocardium were being under met when aortic diastolic pressure was reduced.In previous animal studies from our laboratory (3, 4) we showed that when pressure in the coronary circulation was independently reduced by coronary constriction, the subendocardium developed metabolic signs of inadequate oxygen delivery. This finding correlated well with a pressure index developed by us to predict the presence of uneven myocardial blood flow (5). It (Fig. 1) into the aorta via the ligated left subclavian artery and passing it retrograde across the aortic valve. This tube, henceforth referred to as an "aortic insuffi...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Coronary Hemodynamics and Regional Myocardial Metabolism in Experimental Aortic Insufficiency

Griggs¹,

Chen²

1974

J. Clin. Invest.

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“…Measurements of transmural myocardial blood flow and the capacity to augment endocardial blood flow have yielded conflicting results (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Winbury (1), using polarographic techniques for measuring intramyocardial oxygen tension in anesthetized dogs, reported lower Po2 within the subendocardium than in the subepicardium.…”

Section: Introductionmentioning

confidence: 99%

Regional Myocardial Blood Flow in Awake Dogs

Cobb¹,

Bache²,

Greenfield³

1974

J. Clin. Invest.

154

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A B S T R A C T The objectives of this study were to test the hypothesis in awake dogs that during control conditions endocardial vessels are maximally dilated and to determine whether variables introduced by general anesthesia and thoracotomy modify distribution of myocardial blood flow or impair capacity for augmentation of flow in response to a coronary vasodilator stimulus. Myocardial blood flow was measured in, relatively small, 2-3 g, left ventricular epicardial and endocardial samples by using 7-10-Arm radioisotope-labeled microspheres during control conditions and during infusion of adenosine in dosages which produced maximum increases in coronary blood flow. Measurements were made initially in awake resting animals and were repeated after pentobarbital anesthesia, thoracotomy, and pericardiotomy.Blood flow (mean+±SEM) in the epicardium and endocardium, respectively, was 0.75±0.06 and 0.83±0.06 during control conditions and 4.98±0.28 and 4.49±0.27 cm',/ min/g during adenosine. These data demonstrate considerable capacity for vasodilation in both myocardial layers and thus refute the hypothesis that endocardial vessels are maximally dilated during control conditions. During control conditions blood flow within epicardial and endocardial layers was essentially homogeneous around the circumference of the left ventricle. In contrast to previous studies in anesthetized animals, however, transmural gradients were present in most regions, i.e., endocardium: epicardium ratio (endo/epi) 1.06-1.16. During adenosine, circumferential epicardial flows were homogeneous; however, circumferential endocardial flows were inhomogeneous and increased less than epicardial flows, endo/epi 0.81-0.99.

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“…As a 40/ result, the increased oxygen delivery needed by the 40 heart when its work increases is obtained mainly by an 7-increased coronary blood flow. This dependence of myocardial oxygen supply on coronary blood flow also implies dependence on coronary vascular o 40 resistance since, by the hydraulic equivalent of Ohm's law, flow = pressure drop/resistance, and pressures CORONARY PEF tend to remain fairly constant. Changes in coronary vascular resistance are the basis for the phenomenon of autoregulation, a term which indicates that the heart regulates its oxygen supply and blood flow according to its needs. One way of demonstrating this is shown in figure 1 decreased pressure drop, so that at this time at least some vessels are maximally dilated.…”

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confidence: 99%