IMPACT OF IMPAIRED CORONARY FLOW RESERVE AND INSULIN-RESISTANCE ON MYOCARDIAL ENERGY-METABOLISM IN PATIENTS WITH SYNDROME-X

To evaluate the role of a decreased coronary flow reserve in the genes is of angina pectoris in patients with syndrome X, we studied myocardi al hemodynamics and metabolism at rest, during pace stress, and in the recovery period after pacing in 18 consecutive patients with syndrome X and in 10 control subjects. By means of positron emission tomograph y or the intracoronary flow-wire method, patients were subclassified a s having microvascular angina (MA, n = 8) when coronary flow reserve w as reduced (<2.5) or no microvascular angina (non-MA, n = 10) when cor onary flow reserve was preserved (greater than or equal to 2.5). At re st, coronary sinus blood flow was increased in MA patients. During pac e stress, coronary sinus blood flow increased by 39 +/- 6% in MA patie nts versus 67 +/- 12% in non-MA patients and 69 +/- 7% in controls (p <0.05). Patients with non-MA revealed fasting hyperinsulinemia, increa sed arterial concentration of free fatty acids, and a similar tendency for beta-hydroxybutyrate. Oxygen extraction and carbon dioxide releas e did not differ between groups. Net myocardial lactate release wets n ot observed in any patient during pace stress and myocardial energy me tabolism was preserved in all patients with syndrome X. During pacing, myocardia uptake of free fatty acids and beta-hydroxybutyrate was inc reased in non-MA patients. Myocardial uptake of free fatty acids corre lated positively and myocardial glucose and lactate uptake correlated inversely with arterial concentrations of free fatty acids in all subj ects. Metabolic evidence of myocardial ischemia is uncommon in patient s with syndrome X, irrespective of a globally reduced coronary flow re serve. Although patients with syndrome X can be subclassified accordin g to presence of a microvascular or a metabolic disorder, angina pecto ris and ST-segment depressions coexist with a preserved global myocard ial energy efficiency in all patients. (C) 1997 by Excerpta Medica, In c.