Intraventricular Pressure and the Distribution of Coronary Blood Flow

Cutarelli, Renato; Levy, Matthew N.; Zieske, Harrison; Nelson, Geroldine

doi:10.1161/01.res.12.3.322

Cited by 47 publications

(18 citation statements)

References 17 publications

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“…The control subendocardial-subepicardial flow ratios which we obtained with 8-10/x microspheres are similar to those obtained with diffusible indicators (7,8,29,30); the slight differences noted could be due to differences in the techniques used or the physiology of the preparations. In addition, the way the heart has been divided to provide these ratios is not uniform in different studies.…”

Section: Discussionsupporting

confidence: 83%

Experimental Subendocardial Ischemia in Dogs with Normal Coronary Arteries

Buckberg

Fixler

Archie

et al. 1972

Circulation Research

809

403

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Subendocardial ischemia without anatomic coronary artery obstruction may result from a discrepancy between metabolic needs and available blood supply. We studied this in open-chest anesthetized dogs and measured pressures in aorta and left ventricle (LV), phasic left coronary arterial blood flow (CBF) by electromagnetic flowmeter, total CBF and LV subendocardial (endo) and subepicardial (epi) flow with radioactive microspheres 8-10fi in diameter. Since LV subendocardial flow is mainly or entirely diastolic, it should depend on coronary driving pressure and duration of diastole (i.e., the area between aortic and left ventricular diastolic pressures). This diastolic pressure time index (DPTI) was varied by opening arteriovenous fistulas to lower aortic diastolic pressure, constricting the ascending aorta to raise LV diastolic pressure and pacing to shorten diastole. Myocardial oxygen needs were estimated from the tension time index (TTI). Normal endo-epi flow ratios per gram (1:1) fell to 0.1:1 with these procedures and paralleled a fall in diastolic flow fraction (often nearly zero) and postischemic coronary reactive hyperemic responses. These changes occurred despite normal or raised mean CBF and 300-500% increase in systolic CBF. The altered flow ratios were best predicted by relating them to the ratio of DPTI (supply) to TTI (demand). KEY WORDSregional coronary blood flow arteriovenous fistula subepicardial flow aortic constriction radioactive microspheres ventricular pacing reactive hyperemia tension time index phasic coronary blood flow diastolic pressure time index• Patchy necrosis and fibrosis of left ventricular subendocardial muscle occur in patients whose coronary arteries are normal or narrowed by atheroma (1-5). These changes could be due to a discrepancy between myocardial oxygen demand and available blood supply in subendocardial muscle, but this hypothesis has not yet been tested in

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Section: Discussionsupporting

confidence: 83%

Experimental Subendocardial Ischemia in Dogs with Normal Coronary Arteries

Buckberg

Fixler

Archie

et al. 1972

Circulation Research

809

403

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“…infusion of adenosine, 4.0 ,umol/kg of body weight/min via the right antecubital vein. The adenosine was dissolved in warmed normal saline, 30 ,umol/cm3.…”

Section: Methodsmentioning

confidence: 99%

“…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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“…Tissue uptake methods, which have used intravascular administration of diffusible isotopes, have shown an equal distribution of flow to the endocardium and the epicardium under normal conditions of coronary perfusion pressure and flow but a decrease in endocardial distribution during myocardial ischemia (12)(13)(14)(15)(16). These methods can be criticized because cellular transport mechanisms rather than flow may be the factor limiting uptake, particularly in studies in which 80 Rb is used (28).…”

Section: Moirmentioning

confidence: 99%

“…Experimental evidence can be marshaled to defend either the view that the subendocardium is adequately perfused under circumstances of normal coronary perfusion pressure and left ventricular pressure (12)(13)(14)(15)(16)(17)(18) or the view that it is underperfused (19)(20)(21)(22)(23)(24) and survives by a hypothetical anaerobic metabolism (19). These opposing conclusions depend on the methods used for estimating endocardial coronary blood flow.…”

mentioning

confidence: 99%