Distribution of myocardial blood flow in the exercising dog with restricted coronary artery inflow.

Ball, Richard; Bache, Robert J.

doi:10.1161/01.res.38.2.60

Cited by 106 publications

(35 citation statements)

References 31 publications

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“…This is consistent with previous observations using hydraulic occluders to create coronary artery stenoses (6,10) or ameroid constrictors to create coronary occlusions (1 1-15). The mechanisms by which flow decreases to subendocardial layers include an increase in the fraction of total flow which occurs during systole (16), intense vasodilation ofcoronary resistance vessels, and reductions in distal coronary artery perfusion pressure (17).…”

Section: Discussionsupporting

confidence: 93%

“…Although it has been previously shown that regional dysfunction may occur after exercise in the presence of coronary artery stenosis (5), the mechanisms underlying post-exercise dysfunction have received little attention. In the presence of a flow-limiting coronary artery stenosis, exercise results in an alteration of the transmural dis-tribution of myocardial perfusion such that flow is distributed preferentially to the subepicardium, while the subendocardium is most severely hypoperfused (6). Since distal coronary vasodilation and tachycardia may persist for some time after the cessation of exercise, it is possible that persistent subendocardial hypoperfusion would continue during the early post-exercise period.…”

Section: Introductionmentioning

confidence: 99%

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Persistence of regional left ventricular dysfunction after exercise-induced myocardial ischemia.

Homans¹,

Sublett²,

Dai³

et al. 1986

J. Clin. Invest.

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139

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To determine whether regional myocardial dysfunction occurring after exercise-induced ischemia might be caused by continued abnormalities of myocardial blood flow in the post-exercise period, nine dogs were instrumented with ultrasonic microcrystals for determination of circumferential segment shortening, circumflex artery electromagnetic flow probes, and hydraulic coronary artery occluders. Dogs performed treadmill exercise during partial inflation of the coronary artery occluder. When the stenosis was maintained after exercise (persistent stenosis), subendocardial hypoperfusion was noted 1 min after exercise (subendocardial flow = 0.79±0.42 ml/min per g vs. 1.39±0.43 ml/ min per g control), and this was associated with continued dysfunction in the ischemic zone (segment shortening 45.4±36.9% of resting control). When the stenosis was released immediately after exercise (temporary stenosis), however, flow was markedly increased 1 min post-exercise (mean transmural flow 4.24±1.22 ml/min per g, subendocardial flow 4.18±1.52 ml/min per g), and this was associated with a transient increase in segment shortening to 104.5±9.3% of resting control. 5 min after exercise, however, moderate reductions in ischemic segment shortening were noted after both temporary stenosis and persistent stenosis runs, and these persisted for 30 min post-exercise. It is concluded that regional left ventricular dysfunction may persist for a significant period of time after exercise-induced ischemia. Furthermore, early after exercise, dysfunction is related to persistent abnormalities of myocardial blood flow, whereas late after exercise it is independent of primary reductions in myocardial blood flow.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Persistence of regional left ventricular dysfunction after exercise-induced myocardial ischemia.

Homans¹,

Sublett²,

Dai³

et al. 1986

J. Clin. Invest.

Self Cite

139

View full text Add to dashboard Cite

show abstract

“…The redistribution ofregional myocardial blood flow in the partially occluded region in this study is comparable to that which our laboratory described earlier in animals with partial coronary artery stenosis and ischemia-induced vasodilation (14) and in exercising animals with partial occlusion (13 (26). Earlier studies in our laboratory have shown that the initial localization ofthallium-20 1 is closely related to myocardial blood flow during a wide range of blood flows produced by ischemia and exercise stress (12), and by acute ischemia and recent myocardial infarction (27).…”

Section: Discussionsupporting

confidence: 90%

“…First, intravenous dipyridamole infusion in dosages that cause marked coronary vasodilation effects a distribution of regional myocardial blood flow that is comparable to, as previously reported by our laboratory, blood flow distribution during exercise and partial and complete coronary occlusion (12,13) and during partial occlusion and ischemicinduced vasodilation (14). Second, regression analysis demonstrated that the relationship between the distribution of thallium-201 and myocardial blood flow during dipyridamole infusion was similar to that observed in animals subjected to treadmill exercise.…”

Section: Discussionsupporting

confidence: 77%

Relationship between regional myocardial blood flow and thallium-201 distribution in the presence of coronary artery stenosis and dipyridamole-induced vasodilation.

Mays¹,

Cobb²

1984

J. Clin. Invest.

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Abstract. This study assesses the relationship between the distribution of thallium-201 and myocardial blood flow during coronary vasodilation induced by intravenous dipyridamole in canine models of partial and complete coronary artery stenosis. 10 dogs were chronically instrumented with catheters in the left atrium and aorta and with a balloon occluder and electromagnetic flow probe on the proximal left circumflex coronary artery. Regional myocardial blood flow was measured during control conditions with radioisotope-labeled microspheres, and the phasic reactive hyperemic response to a 20-s transient occlusion was then recorded. Dipyridamole was then infused intravenously until phasic coronary blood flow increased to match peak hyperemic values. The left circumflex coronary artery was either partially occluded to reduce phasic blood flow to control values (group 1) or it was completely occluded (group 2), and thallium-201 and a second microsphere label were injected. 5 min later, the animals were sacrificed, the left ventricle was sectioned into 1-2-g samples, and thallium-201 activity and regional myocardial blood flow were measured.Curvilinear regression analyses between thallium-20 1 localization and myocardial blood flow during dipyridamole infusion demonstrated a slightly better fit to a second-as compared with a first-order model, indicating a slight roll-off of thallium activity as myocardial blood This work was presented in part at the 54th Scientific Session of the American Heart Association, November 1981, Dallas, Texas.Received for publication 7 January 1983 and in revised form 16 January 1984. flow increases. During the dipyridamole infusion, the increases in phasic blood flow, the distributions of regional myocardial blood flow, and the relationships between thallium-201 localization and regional blood flow were comparable to values previously observed in exercising dogs with similar occlusions. These data provide basic validation that supports the use of intravenous dipyridamole and thallium-201 as an alternative to exercise stress and thallium-20 1 for evaluating the effects of coronary occlusive lesions on the distribution of regional myocardial blood flow.

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“…It seems likely that this regional ischemia resulted from increased myocardial metabolic demands in the face of limited coronary reserve as well as from coronary blood flow redistribution away from the subendocardium during exercise under conditions of partial coronary artery constriction. 9 The severity of the exercise in the present experiments undoubtedly explains the rapidity with which regional dysfunction developed and could account for the occurrence of sudden death in two dogs. The latter event is most unusual during exercise testing in patients.…”

Section: Figure 3 Left Panel: Serial Changes In the Control Segments mentioning

confidence: 62%

Regional myocardial dysfunction and hemodynamic abnormalities during strenuous exercise in dogs with limited coronary flow.

Tomoike¹,

Franklin

McKown³

et al. 1978

Circulation Research

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SUMMARY We studied regional myocardial dynamics during brief, strenuous bouts of running in 12 conscious dogs by telemetry before and after partial circumflex coronary artery (CCA) constriction. Regional myocardial dimensions were measured by an ultrasonic method in a control segment (CS) and segment to be made ischemic (IS). In control runs heart rate (HR), left ventricular (LV) systolic pressure, and dP/dt increased markedly, and segment end-diastolic lengths (EDL) increased along with augmentation of regional myocardial performance. Following CCA constriction, resting hemodynamics and segment dynamics remained within the control range; during running, HR was elevated similarly to the control (approximately 280/min), but LV systolic pressure and dP/dt changes were significantly reduced. Shortening of CS did not change significantly, but IS shortening, velocity, and indices of segment power and stroke work were rapidly and markedly depressed. In two dogs, ventricular fibrillation occurred during and immediately after running. After exercise, IS shortening usually required from 5 to 10 minutes to recover to near pre-exercise levels. We conclude that when regional and total cardiac function are within the normal range at rest, strenuous exercise in the presence of coronary stenosis induces rapid, severe regional myocardial dysfunction accompanied by significant hemodynamic abnormalities and, occasionally, by sudden death. Abnormal regional wall motion during and following exercise appears to provide a specific indicator of limited coronary reserve.IN NORMAL experimental animals, exercise increases the cardiac output, systemic arterial pressure, heart rate, and myocardial contractility, and thereby markedly augments myocardial oxygen consumption and coronary blood flow.1 "" When the coronary blood supply is limited by experimental coronary artery stenosis or by obstructive coronary artery disease in man, exercise is known to evoke electrocardiographic S-T segment abnormalities 7 " and to cause redistribution of coronary blood flow. -9Such changes in the electrocardiogram, suggestive of subendocardial ischemia, have led to the widespread use of exercise stress testing in patients with coronary heart disease. 8Regional myocardial function measured by implanted ultrasonic crystals'" recently has been found to be a sensitive indicator of myocardial ischemia in conscious dogs,"~':l and we have now combined this approach with telemetry to make direct measurements of regional left ventricular dynamics and corresponding hemodynamic measurements in conscious exercising dogs before and during partial coronary artery stenosis. It was hypothesized that if coronary blood flow were limited by coronary stenosis during the resting state, regional myocardial function would remain within the normal range at rest. However, if the myocardial oxygen demands then rose to exceed the limited coronary reserve, regional myocardial performance in the ischemic area would promptly become depressed, and if the physiological stress were severe,...

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Distribution of myocardial blood flow in the exercising dog with restricted coronary artery inflow.

Cited by 106 publications

References 31 publications

Persistence of regional left ventricular dysfunction after exercise-induced myocardial ischemia.

Persistence of regional left ventricular dysfunction after exercise-induced myocardial ischemia.

Relationship between regional myocardial blood flow and thallium-201 distribution in the presence of coronary artery stenosis and dipyridamole-induced vasodilation.

Regional myocardial dysfunction and hemodynamic abnormalities during strenuous exercise in dogs with limited coronary flow.

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