Coronary vasomotor tone: Determinants and effect on coronary angioplasty

Background. Coronary artery reference diameters increase during coronary angioplasty (PTCA). However, in clinical practice, balloon selection is often based on a preceding diagnostic coronary angiogram. It is common to find that the initially selected balloon is undersized due to resting vasomotor tone. This may contribute to a suboptimal angioplasty result. Methods. Quantitative coronary angiography (QCA) was used to determine the magnitude of coronary artery vasodilatation over baseline angiography and its impact on balloon size choice. PrePTCA clinical and treatment variables were analyzed for their potential contribution to resting vasomotor tone. Results. QCA of reference coronary diameters was performed in a group of 103 patients undergoing PTCA. Post PTCA proximal and distal reference diameters significantly increased over baseline. The average increase of the proximal segment was 0368 mm (13.6%) p < 0.001 and of the distal segment 0.567 mm (24.8%) p < 0.001. The initial nominal balloon diameter was smaller than the post PTCA proximal segment by an average of 0.34 mm (12.6%) p < 0.001. Of the clinical and treatment variables examined age < 65 years and pre-PTCA beta blocker use, significantly affected baseline vasomotor tone p < 0.05. Conclusions. Routine diagnostic angiography underestimates the true diameter of the coronary artery. Due to baseline vasomotor tone, coronary reference segments can be expected to increase approximately 13% in diameter during successful PTCA. Patients under 65 years of age and those using beta-blockers may have a significantly increased baseline vasomotor tone. Underestimation of coronary artery diameter based on initial angiography necessitated a second, larger balloon in 16.5% of cases.