MECHANISMS OF ANGINA-PECTORIS IN SYNDROME-X ASSESSED BY MYOCARDIAL PERFUSION DYNAMICS AND HEART-RATE-VARIABILITY

The fundamental abnormality in syndrome X (angina pectoris, ischaemia- like stress ECG despite angiographically normal coronary arteries) mig ht be patchily distributed increased tone in pre-arteriolar coronary v essels with compensatory release of adenosine. The aim of this study w as to confirm this hypothesis and to explore its relationships with au tonomic system functioning. Using parametric positron emission tomogra phy, myocardial perfusion was examined in 480 segments in 16 syndrome X patients and 16 age- and sex-matched healthy volunteers. Automatic f unction was explored by Holter monitoring of time domain parameters of heart rate variability. Compared to volunteers, both mean perfusion ( 123 +/- 35 vs 87 +/- 16 mg.min(-1).100 g(-1); P<0.01) and its coeffici ent of variation (17.0 +/- 3.2 vs 13.6 +/- 2.2%; P<0.01) as a measure of perfusion heterogeneity, were higher in patients with syndrome X. I n contrast to the findings in the control subjects, patients showed an inverse relationship between perfusion heterogeneity (coefficient of variation of segmental perfusion) and autonomic tone (heart rate varia bility parameters). Since marked perfusion heterogeneity (inversely re lated to autonomic tone) and higher overall perfusion were found, the study supports the data that in syndrome X hyperreactivity of small co ronary vessels with compensatory release of adenosine may be patchily distributed.