Clinical and arteriographic characterization of patients with unstable angina without critical coronary arterial narrowing (from the TIMI-IIIA Trial).

Previous studies have reported that some patients presenting with unstable angina are found at coronary angiography to have no critical coronary stenosis. This study evaluated the clinical presentation and arteriographic findings in patients enrolled in the Thrombolysis in Myocardial Ischemia (TIMI-IIIA) trial, which assessed the effect of tissue-type plasminogen activator added to conventional therapy on the coronary arteriographic findings in patients presenting with ischemic pain at rest. Three hundred ninety-one patients were enrolled in the TIMI-IIIA trial and underwent coronary arteriography within 12 hours of enrollment. Fifty-three patients (14%) had no luminal diameter stenosis of a major coronary artery of > or = 60% on the baseline arteriogram. Compared with patients with unstable angina with an identifiable culprit lesion, patients without critical coronary obstruction were more likely to be women and non-white and less likely to have ST-segment deviation on the presenting electrocardiogram. Arteriography in such patients revealed no visually detectable coronary stenosis in half of the group; the remaining patients had noncritical coronary narrowing (i.e., < 60% luminal diameter stenosis) without morphologic features (ulceration or thrombus) suggestive of unstable or active coronary plaque. Nearly one third of the patients without critical coronary stenosis had impaired angiographic filling, suggesting a possible pathophysiologic role for coronary microvascular dysfunction. These patients with unstable angina and no critical coronary obstruction had an excellent short-term prognosis; 2% died or had myocardial infarction compared with 18% of patients with critical obstruction.

A new bioabsorbable intravascular stent: in vitro assessment of hemodynamic and morphometric characteristics.

Currently available intracoronary stents are permanent and their placement may be complicated by thrombosis and restenosis. We have developed a new bioresorbable stent constructed of type I collagen. This stent has a compliant tubular structure that is self expanding and carries a net negative surface charge to increase hemocompatibility. In vitro histologic and morphometric examination was performed by deploying the stent in six pressure fixed explanted porcine arteries. Morphometry revealed a close relationship between the stent external diameter 2.9 +/- 0.4 mm) and the arterial lumen diameter (3.0 +/- 0.4 mm). A relative reduction in arterial lumen diameter secondary to stent placement of 17% to 26% was observed. Folding of the stent wall was noted in those preparations where the stent external diameter was larger than the arterial lumen diameter. Polyvinyl chloride (PVC) tubing was used as a mock arterial segment for flow studies. Flow at baseline and following stent placement was determined at perfusion pressures of 10, 50, and 80 mmHg. A modest reduction in flow following stent placement of between 2% and 6% was observed. Thus, type I collagen may be used to construct a self expanding tubular stent. Morphometric and hemodynamic evaluation reveals a modest impact on arterial lumen dimensions and flow.