CHANGES IN PROXIMAL AND DISTAL CORONARY-ARTERY DIAMETER DURING ATRIALPACING-INDUCED MYOCARDIAL-ISCHEMIA

Background: The present study was designed to evaluate the role of tac hycardia-induced dynamic coronary artery diameter changes in the devel opment of myocardial ischemia. Methods: Coronary angiography at rest a nd during atrial pacing-induced myocardial ischemia was performed in 2 2 patients. The diameter of the proximal and the corresponding distal coronary artery segments at rest and during pacing was measured using quantitative coronary angiography. Plasma levels of noradrenaline, adr enaline, dopamine and endothelin were determined in a subset of 14 pat ients in blood drawn from aorta and coronary sinus at rest and during pacing. Results: Luminal diameter in normal proximal and distal segmen ts increased, respectively, from 2.93+/-0.34 and 1.40+/-0.04 mm at res t to 3.0+/-0.25 and 1.58+/-0.07 mm during atrial pacing. The diameter of the proximal coronary artery segments with significant concentric s tenosis decreased from 1.28+/-0.4 mm at rest to 0.95+/-0.34 mm during pacing, whereas segments with either significant eccentric or non-sign ificant stenosis did not change significantly. A correlation was found between the noradrenaline level in the coronary sinus and the distal coronary artery diameter. Conclusions: A decrease in diameter of coron ary artery segments with concentric stenosis during tachycardia might contribute to the development of myocardial ischemia. Some of the dyna mic coronary artery changes may be influenced by the plasma level of n oradrenaline. No evidence was found to suggest that dynamic changes in the diameter of proximal segments are related to the changes in diame ter of the corresponding distal segments.