Intravascular ultrasound study of angiographically mildly diseased coronary arteries

Objectives. We hypothesized that intravascular ultrasound may identify significant coronary artery narrowing in the mildly diseases artery of patients with or one- or two-vessel coronary artery disease. Bacground. Necropsy studies have revealed that coronary angiography may underestimate stenosis severity in vessels that appear mildly diseased. Intravascular ultratound has been shown to detect atherosclerotic changs in a angiographically normal coronary arteries and to correlate better with histologic findings. Methods. In 20 patients, we performed intravascular ultrasound imaging (3.5F catheter, 30-MHz transducer) in 37 coronary arteries that were considered mildly diseased (<50% diameter narrowing) by qualitative angiography. The angiographic diagnosis was no significant coronary artery in eight patients, one-vessel disease to seven and two-vessel disease in five. Each vessel, except for the left main coronary artery, was divided into proximal, mid and distal segments. Percent area narrowing and minimal lumen diameter were subsequently quantified by both ultrasound and quantitative angiography. Results. Mean maximal arterial area narrowing by ultrasound in the 67 segments studied was 36 ± 20% (range 0% to 80.2%) and 19 ± 23% (range 0% to 82%) by quantitative angiography of these same (p < 0.001, paired t test). Mean minimal lumen diameter of the segments was 3.3 ± 0.9 mm by ultrasound and 2.7 ± 0.8 mm by quantitative angiography. In 10 patients there were 19 angiographically mildly diseased segments where the percent arterial area narrowing by ultrasound was ≥50%. Intravascular ultrasound revealed that the more proximal (reference) segmnt had >25% intimal thickening in 12 of the 19 underestimated segments. In six stenosed segments (32%), total vessel area increased compared with that of the adjacent proximal vessel segment because of compensatory dilation. Conclusions. Intravascular ultrasound identified potentially significant coronary artery disease in vessels that appear to be only mildly diseased by angiography.