Side branch occlusion during coronary angioplasty: incidence, angiographic characteristics, and outcome.

Side branch occlusion (SBO) during percutaneous transluminal coronary angioplasty is a well-recognized complication. The purpose of the present study was to analyze the incidence, angiographic characteristics, and sequelae of side branch occlusion. Data from coronary angiograms of 4,800 consecutive patients from January 1981 to December 1987 was retrospectively analyzed, and 167 patients (3%) involving 181 lesions, with side branch occlusion, were identified. Only arteries with occlusion of side branches greater than 1 mm were evaluated. There were 65 (36%) diagonal, 49 (27%) septal, 40 (22%) left circumflex, and 27 (15%) right coronary branch occlusions. Most side branch occlusion occurred in branches with disease (66%: 120 of 181) or branches originating within the primary arterial lesion (72%: 130 of 181). Although the incidence of side branch occlusion is uncommon, it is associated with a significant incidence of myocardial infarction (14%). Attempts to reopen the occluded branch were successful in 27 of 36 cases (75%). With improvement in balloon angioplasty technology, the risks of side branch occlusion have declined, and many occlusions can be successfully reopened, suggesting that side branch involvement in a primary lesion is not a limitation to balloon angioplasty.