Angiographically assessed coronary collateral circulation increases vulnerability to myocardial ischemia during vasodilator stress testing
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Keywords:
Dipyridamole
Collateral circulation
Coronary circulation
Coronary steal
Coronary vasodilator
The effects on the coronary circulation of RA233, a recently developed analog of dipyridamole, were investigated in the acutely transplanted dog heart and compared with those of dipyridamole and adenosine. Close arterial infusions of RA233 increased coronary blood flow within 30 seconds and this returned to control values within 15 minutes of stopping the infusion. In contrast, dipyridarnole increased coronary blood flow only after two minutes of infusion, and after stopping the infusion had a longer residual effect which lasted for 60 minutes. The dose-response curves for RA233 and dipyridamole were parallel and showed that RA233 was only from 1/20 to 1/30 as potent as dipyridamole. Equipotent low dose infusions of both RA233 and dipyridamole potentiated to a similar degree the coronary vasodilator actions of adenosine, shifting the dose-response curve for adenosine to the left in a parallel manner. Low dose infusions of aminophylline alone uniformly produced small reductions in coronary blood flow (16 ±4%) and increased coronary vascular resistance and also blocked the coronary vasodilator actions of RA233, dipyridamole and adenosine. RA233 responses were significantly less inhibited by aminophylline than were those produced by equipotent doses of dipyridamole and adenosine; the latter two were inhibited to a similar degree. With all three drugs, aminophylline produced parallel displacement of the dose-response curves consistent with competitive inhibition. These results with aminophylline may be relevant to the more powerful inhibition of platelet aggregation reported for RA233.
Aminophylline
Dipyridamole
Coronary vasodilator
Coronary circulation
Coronary steal
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It has been reported that previously administered dipyridamole intensifies the coronary vasodilator action of adenosine compounds. In the present study, a combination of dipyridamole and ATP at doses that alone are ineffective was examined for its effect on the coronary sinus blood flow. In 10 anesthetized dogs, heart rate, arterial blood pressure, cardiac output, and coronary sinus blood flow were measured before and during a 20-min constant-rate infusion of (a) ATP alone, 1 mg/min; (b) a combination of ATP, 1 mg/min, and dipyridamole, 0.005 mg/kg/min; and (c) dipyridamole alone, 0.005 mg/kg/ min. Coronary sinus flow was measured by a newly developed thermodilution flowmeter. Consistently during the infusion of ATP or dipyridamole alone no changes in the measured parameters occurred, whereas during infusion of the combination a very marked and sustained elevation (+493%) of coronary flow occurred, associated with a moderate increase in cardiac rate (+37%) and output (+42%) and a decrease in arterial blood pressure (-17%). In 7 other dogs, coronary vasodilator responses to ATP were determined before and 1 hour after a single 10-mg dose of dipyridamole. After dipyridamole, the coronary vasodilator action of ATP increased 5- to 100-fold. In a third group of 3 dogs, dipyridamole did not enhance the coronary vasodilator effects of nitroglycerin, bradykinin, or acetylcholine.
Dipyridamole
Coronary vasodilator
Coronary circulation
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Summary To study the effects of certain vasodilator drugs on the coronary vasculature of the transplanted heart, dog hearts were Implanted into the necks of recipient dogs and connected to the circulation so that coronary blood flow and coronary vascular resistance could be measured continuously. During the first six hours close arterial injections of adenosine and dipyridamole produced marked increases in coronary blood flow and reduced coronary vascular resistance in the transplanted heart; dipyridamole greatly potentiated the vasodilator actions of adenosine. Propranolol, in a beta adrenergic blocking dose, did not alter coronary blood flow or coronary vascular resistance or influence the actions of dipyridamole or adenosine. Low dose infusions of aminophylline uniformly reduced coronary blood flow and increased coronary vascular resistance and also blocked the actions of dipyridamole and adenosine. The blocking effect was similar with higher doses of aminophylline which temporarily increased coronary blood flow. The findings show that coronary vascular reactivity to dipyridamole and adenosine is maintained up to at least six hours after transplantation, and suggest that dipyridamole acts largely through aderosine. Propranolol does not increase coronary vascular resistance in the denervated heart. The aminophylline‐mediated increase in coronary vascular resistance could result from a blocking of the vasodilator effects of adenosine locally produced in non‐ischaemic myocardium.
Aminophylline
Dipyridamole
Coronary circulation
Coronary vasodilator
Coronary steal
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Dipyridamole
Coronary steal
Coronary anatomy
Depression
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Coronary vasodilator
Coronary perfusion pressure
Coronary circulation
Coronary steal
Coronary vessel
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Dipyridamole
Coronary vasodilator
Coronary circulation
Coronary steal
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The effects of intravenous dipyridamole (20 mg) and sublingual nitroglycerin (0.6 mg) were compared at rest and during rapid atrial pacing in patients with significant coronary obstruction. Dipyridamole, which had no significant effect on resting systolic blood pressure, caused a significant increase in coronary sinus flow (CSF) and reduction of coronary vascular resistance (CVR) and arterial-coronary sinus oxygen difference (AO2-CSO2δ), whereas nitroglycerin reduced resting systolic pressure but had no significant effect on CSF, CVR, or AO2-CSO2°. Although these effects of dipyridamole and nitroglycerin on resting systolic pressure, CSF, CVR, and AO2-CSO2° were qualitatively similar during rapid atrial pacing, the onset of chest pain and ischemic ECG changes occurred at a lower heart rate following dipyridamole (136±5 beats/min) than following nitroglycerin (149±6 beats/min, p<0.01). However, maximal double product and myocardial oxygen consumption achieved during pacing were similar following both dipyridamole and nitroglycerin and were less than control pacing values. Coronary dilatation following dipyridamole appears to reduce tolerance to pacing-induced ischemia probably by maldistribution of coronary flow away from ischemic myocardium. Nitroglycerin differs from dipyridamole by improving tolerance to pacing; however, this difference appears to be due to systemic vasodilator effects of nitroglycerin rather than to enhancement of flow to ischemic myocardium.
Dipyridamole
Nitroglycerin (drug)
Coronary steal
Coronary vasodilator
Sublingual administration
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The aim of this study was to evaluate simultaneously echocardiographic, haemodynamic and angiographic changes that occur during adenosine and dipyridamole infusion, in patients with one-vessel coronary artery stenosis. This would assess whether deterioration in left ventricular haemodynamics during vasodilator agent infusion is influenced by vasodilation per se, or the development of myocardial ischaemia. We performed adenosine (140 μg.kg−1.min−1 over 4 min) and dipyridamole (up to 0·84 mg.kg−1 over 10 min) stress echocardiography tests, together with angiographic and haemodynamic assessment, in 26 patients undergoing elective coronary angioplasty. In 12 of 26 patients, adenosine and dipyridamole tests were repeated 24 h after angioplasty. The criterion for echocardiography test positivity was the appearance of a new transient regional wall motion abnormality. Coronary angiograms were analysed with quantitative coronary arteriography. Adenosine and dipyridamole induced regional dysfunction in 18/26 (69%) and 14/26 (54%) patients before angioplasty, respectively (P=ns). In the echocardiography-positive patients, the percent diameter stenosis was significantly (P<0·05) tighter stenosis than in the echocardiography-negative patients (adenosine, 66·6±8·3% vs 58·0±8·9%; dipyridamole, 69·2±7·1% vs 57·±7·6%). During both tests, left ventricular end-diastolic pressure significantly increased (P<0·05) in echocardiography-positive patients (adenosine, 9·8±2·7 mmHg to 13·5±4·1 mmHg; dipyridamole, 10·1±2·8 mmHg to 14·1±4·3 mmHg), but not in echocardiography-negative patients. In the patients who had undergone successful angioplasty (reduction to <50% diameter stenosis), both adenosine and dipyridamole confirmed the arteriographic success of the procedure (echocardiography negative in all patients). In this group of patients, no significant change was observed in left ventricular end-diastolic pressure during adenosine or dipyridamole infusion. Intravenous infusion of either adenosine or dipyridamole was accompanied by an obvious increase in left ventricular end-diastolic pressure only in patients with induced wall motion abnormalities. Coronary vasodilation per se has no significant effect on left ventricular end-diastolic pressure when no ischaemia is induced, disproving any clinically significant 'erectile' and adverse effects of coronary vasodilation per se.
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Coronary steal
Coronary vasodilator
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Intravenous dipyridamole is widely used to produce coronary vasodilation during cardiac imaging procedures. However, the routinely used dose of dipyridamole (0.56 mg/kg IV over 4 min) does not always result in maximal coronary dilation. The addition of isometric handgrip during dipyridamole coronary dilation has been reported to substantially increase coronary blood flow over dipyridamole alone. We compared the coronary vasodilation resulting from infusion of the standard dose of dipyridamole with that resulting from a maximally dilating dose of intracoronary papaverine in 12 patients with angiographically normal coronary arteries. We also assessed the effect on coronary blood flow velocity of the addition of isometric handgrip during dipyridamole coronary dilation. Changes in coronary blood flow velocity were measured with a 3F coronary Doppler catheter. The coronary flow reserve (peak/resting coronary flow velocity ratio) after dipyridamole (3.7 +/- 1.2 [mean +/- SD] was less than that seen after papave...
Dipyridamole
Coronary vasodilator
Coronary flow reserve
Coronary steal
Coronary circulation
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Dipyridamole
Coronary steal
Coronary circulation
Coronary flow reserve
Coronary vasodilator
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