Transient myocardial dysfunction during pharmacologic vasodilation as an index of reduced coronary reserve: A coronary hemodynamic and echocardiographic study

Abstract

Regional coronary flow reserve and regional myocardial contractility were evaluated in 29 patients after maximal pharmacologic coronary vasodilation (intravenous dipyridamole, 0.56 mg/kg body weight, administered over 4 minutes). Nineteen patients had a severe (80 to 99%) proximal and isolated stenosis of the left anterior descending coronary artery and 10 patients had normal coronary arteries; all had normal ventricular function under rest conditions. Myocardial contractility was assessed by means of continuous two-dimensional echocardiographic monitoring; coronary reserve was evaluated by coronary sinus thermodilution. After dipyridamole infusion, 9 of the 19 patients with left anterior descending artery stenosis had transient myocardial asynergy involving the septum or apex, or both (Group IA), whereas 10 patients showed no asynergy (Group IB). No impairment of contractility was observed in the 10 patients with normal coronary arteries (Group II). Coronary blood flow was measured under basal conditions and up to 10 minutes after the end of dipyridamole infusion. In patients in Group II, dipyridamole induced an increase in great cardiac vein flow of 167 +/- 68% (mean +/- SD). The 10 patients in Group IB showed a response comparable with that of the control group (Group II) (136 +/- 45% increase in great cardiac vein flow; NS versus Group II), whereas the 9 patients in Group IA had an increase of 46 +/- 30% (p less than 0.01 versus both Group IB and Group II). No significant difference was found in the angiographic severity of the stenosis expressed in terms of minimal cross-sectional area (Group IA = 0.30 +/- 0.13 mm2, Group IB = 0.34 +/- 0.18 mm2; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)