EFFECTS OF SHORT-TERM ADMINISTRATION OF SUBLINGUAL NIFEDIPINE ON CORONARY ARTERIAL-WALL ELASTIC PROPERTIES - EVALUATION BY INTRAVASCULAR ULTRASOUND

Intravascular ultrasound is suited to measure coronary cross-sectional anatomy. Therefore the regional coronary wall elasticity was evaluate d by examining the response to nifedipine. In 20 patients, coronary os tial pressure (P) and intravascular ultrasound images were simultaneou sly recorded before and after sublingual administration of 10 mg nifed ipine. We identified the perimeter of the vessel wall, with normal or atherosclerotic plaque, on ultrasound image. At the atherosclerotic si te, we measured segmental perimeter (S) for each normal or plaque segm ent. The ratio of the individual segment length (Delta S/Delta P) and cyclic variation of cross-sectional area (Delta A/Delta P) per mm Hg i ncrease in P were calculated. Nifedipine decreased pressure (133/79-12 0/73 mm Hg) and increased heart rate (79-82 beats/min). After nifedipi ne, Delta A/Delta P increased from 8.5 +/- 10.2 x 10(-3) to 16.5 +/- 1 4.4 x 10(-3) mm(2)/mm Hg at 20 normal sites (p = 0.005) but was unchan ged at 17 atherosclerotic sites (6.6 +/- 7.0 x 10(-3) to 6.7 +/- 7.1 x 10(-3) mm(2)/mm Hg). Nifedipine increased Delta S/Delta P in normal s egments (4.5 +/- 8.7 x 10(-3) to 9.9 +/- 10.9 x 10(-3) mm/mm Hg; p = 0 .02) but produced no change in segments with calcified or soft plaque (-1.1 +/- 0.3 x 10(-3) to 1.4 +/- 1.6 x 10(-3) mm/mm Hg and 5.0 +/- 3. 6 x 10(-3) to 6.1 +/- 4.8 x 10(-3) mm/mm Hg, respectively). This study demonstrated that nifedipine increases regional coronary arterial ela sticity at normal segments but not at that containing mildly atheroscl erotic segment, and likely that the arterial wall function indicated b y the response to nifedipine was impaired at an early stage of atheros clerosis.