CORONARY MICROVASCULAR DYSFUNCTION IS ASSOCIATED WITH ISCHEMIC-LIKE ELECTROCARDIOGRAM DURING EXERCISE IN PATIENTS WITH ANGINAL CHEST PAIN AND NORMAL CORONARY ANGIOGRAMS

To determine the possible mechanism of the ischemic-like electrocardio gram (ECG) during exercise in the presence of anginal chest pain and n ormal coronary angiograms, both a treadmill exercise test (TET) and co ronary hemodynamic study were prospectively performed in 33 consecutiv e patients (18 females and 15 males, aged 48 +/- 10 years) with angina of unknown cause. Although baseline characteristics and coronary hemo dynamics were similar between patients with (TET+, n=17) and those wit hout (TET-, n=16) ischemic-like ECG during TET, effort angina was more frequently seen in the former group (P < 0.01). Compared to TET- pati ents, TET+ patients had a significantly lower maximum great cardiac ve in flow (GCVF, 108.8 +/- 47.0 vs 146.4 +/- 23.4 ml/min, P = 0.007), hi gher minimum coronary vascular resistance (0.94 +/- 0.41 vs 0.61 +/- 0 .09 mmHg/ml/min., P = 0.003), and lower corrected GCVF (GCVF/rate-pres sure product, 0.0087 +/- 0.0036 vs 0.0125 +/- 0.0019, p = 0.001) after dipyridamole infusion (0.56 mg/kg for 4 min.). Though coronary flow r eserve was significantly lower in TET+ than in TET- patients (2.26 +/- 0.59 vs 3.08 +/- 0.48, p = 0.0001), myocardial oxygen consumption and myocardial efficiency (rate-pressure product/myocardial oxygen consum ption) were still similar between these two groups after dipyridamole infusion. Thus, coronary microvascular dysfunction rather than altered cardiac metabolism could contribute to effort angina and ischemic-lik e ECG during exercise in patients with anginal chest pain and normal c oronary angiograms.