Intravascular ultrasound imaging in patients with acute myocardial infarction: comparison with chronic stable angina pectoris

Abstract

Background: Myocardial infarction is the result of acute thrombotic occlusion of a coronary artery, most likely secondary to rupture of an atherosclerotic plaque. Intracoronary ultrasonic (ICUS) examinations were performed in patients with acute myocardial infarction (AMI) in order to describe intraluminal ultrasonic findings at the site of acute coronary occlusion.

Methods: Coronary angiography and ICUS studies were performed consecutively within 6 h of the onset of chest pain in 30 patients with AMI prior to percutaneous transluminal coronary angioplasty (PTCA). The control group consisted of 30 patients with chronic stable angina pectoris (SAP). Following angiographic documentation of a proximal stenosis or occlusion, a 3.5 or 4.8 F mechanical ultrasound catheter (20 MHz) was advanced successfully through the lesion in 25 of 30 (83%) patients with AMI and in 15 of 30 (50%) patients with SAP (P < 0.01).

Results: Intracoronary ultrasound permitted differentiation between pulsatile, low-echogenic intraluminal material suggesting thrombus and mural highly echogenic atherosclerotic plaque in 22 of 25 (88%) patients with AMI. A negative imprint of the ICUS catheter was documented within the low-echogenic material in 17 of 25 (68%) patients with AMI. Low-echogenic intraluminal material was found in 18 of 25 (72%) segments proximal and in 12 of 25 (48%) segments distal to the highly echogenic plaque, indicating prestenotic and post-stenotic thrombus in AMI. The plaque appeared eccentric in 22 of 25 (88%) patients with AMI. In comparison, stenotic lesions in chronic SAP patients were less frequently eccentric (5/15, 33%, P < 0.01) and contained a higher proportion of pure highly echogenic material (12/15, 80%). Cross-sectional area stenosis due to highly echogenic plaque averaged 52 +/- 13% in AMI and 82 +/- 3% in SAP (P < 0.01). Calcification of plaque was evident in 21 of 25 patients with AMI (SAP 12/15, 80%, NS). The surface of the plaque was rough in 13 of 25 (52%) AMI patients (SAP 4/15, 27%, P < 0.05). Fissures were detected in only seven (28%) patients and dissection was observed in two (8%) cases. The low incidence might be a result of the limited resolution of the ICUS system.

Conclusion: This study demonstrates that ICUS with 4.8 or 3.5 F catheters is feasible and safe in selected patients with AMI, and adds little to the overall duration of the angioplasty procedure. The identification and demarcation of atherosclerotic plaque provided by ICUS could prove valuable in guiding PTCA, in deciding on appropriate therapy, and in acute and long-term follow-up of AMI patients.