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Geometric features of coronary artery lesions favoring acute occlusion and myocardial infarction: a quantitative angiographic study

Francois Ledru, MD^a, Pierre Théroux, MD, Jacques Lespérance, MD, Jean Laurier, MSc, Pierre Ducimetière, PhD^*, Jean-L.éon Guermonprez, MD^a, Benoit Diébold, MD, PhD^a and Didier Blanchard, MD^a

^a Department of Cardiology, Broussais Hospital, Paris, France
^* INSERM Unit 258, Broussais Hospital, Paris, France
Department of Medecine, Montreal Heart Institute, Montreal, Canada
Department of Radiology, Montreal Heart Institute, Montreal, Canada

View larger version (33K): [in a new window]   Figure 1 Calculation of the symmetry index and inflow/outflow angles. The symmetry index is measured as the ratio of the area of each border of the stenosis in the two-dimensional representation (a and b respectively, b being conventionally greater than a) (A). It ranges from 0% (asymmetry) to 100% (symmetry). The inflow/outflow angles are calculated from the diameter function (B). The stenosis inlet corresponds to the distance between the proximal boundary of the stenosis (P) and maximal obstruction (O) and the stenosis outlet to the area between maximal obstruction and the distal boundary of the stenosis (D). The inflow and outflow geometric angles are calculated as the angles of lines drawn between P and O and between O and D, respectively. The average angles correspond to the angles of the linear regressions of the diameter function between P and O and between O and D, respectively. The maximal angles are calculated as the maximal slopes of the inflow and outflow diameter function respectively. All angles are corrected for the tapering (ß) of the analyzed segment.

View larger version (59K): [in a new window]   Figure 2 Frequency of the culprit lesions for terciles of the stenosis angiographic descriptors. Increasing values of the symmetry index, the percent diameter stenosis, the length and the outflow angles were associated with increasing frequencies of culprit lesions. *Statistics test linearity of the trend (NS: p > 0.05).

View larger version (19K): [in a new window]   Figure 3 Regression lines (and 95% confidence interval) of the symmetry index, the percent stenosis and the maximal outflow angle against time to acute myocardial infarction (AMI) for the culprit and control lesions. The shorter the time to AMI, the greater were the symmetry index, the percent diameter stenosis and the maximal outflow angle of the culprit stenoses. The difference in percent diameter stenosis and maximal outflow angles between culprit and control lesions was time dependent, whereas the difference in the symmetry index was not. Data obtained with average and geometric outflow angles instead of the maximal outflow angle yielded similar findings. *Statistics compare the slopes of the regression lines between culprit and control lesions.

View larger version (28K): [in a new window]   Figure 4 Risk stratification of the 165 stenoses of intermediate severity. Stenoses of intermediate severity (SIS) were defined as stenoses ranging from 40% to 70% diameter reduction. It is based on the combination of the two independent predictors of occlusion at 3-year follow-up (Table 3). The threshold value of these variables was arbitrarily defined as the lower limit of the tercile that yielded a prevalence of culprit lesions above 25% in univariate analysis (Fig. 2). Consequently, the low-risk pattern was defined as a symmetry index <68° and a maximal outflow angle <27° and the high-risk pattern as a symmetry index 68° and a maximal outflow angle 27°. Mean values ± SD are given for both stenosis variables. See text for the predictive values of the low-risk and high-risk models.