Association of size of myocardial scar and persistence of ST-segment elevation after healing of anterior wall myocardial infarction.

Half the patients who survive ST-segment elevation anterior myocardial infarction continue to have ST elevation (STE) 6 months after the event. The mechanism for this and its clinical significance are unclear. There are data to suggest that larger infarcts are more likely to have persistent changes in the ST segment. This study is designed to test this association further using a novel means of assessing the presence and magnitude of myocardial scar using cardiac magnetic resonance imaging (MRI). Delayed imaging by MRI after injection of gadolinium is commonly used to detect myocardial scar through the appearance of delayed contrast hyperenhancement. Consecutive patients referred for myocardial viability imaging were reviewed. The volume of scar as a percentage of anterior wall volume was calculated, and the 26 patients with scar involving >or=10% of the anterior wall were selected for inclusion. All had an electrocardiogram recorded within 15 days of MRI, and none had an intervening cardiac event. Observers unaware of MRI findings independently measured ST-segment changes. Nine patients had STE >1 mm and 17 did not. Mean anterior scar volume in the group without STE was 31.9 +/- 17.1% of the anterior wall volume compared with 50.3 +/- 15.9% in the group with STE >1 mm (p = 0.01). The larger the myocardial scar, the more likely STE was to be present. Only 1 of 10 patients (10%) with scar in the anterior wall <30% had such an elevation compared with 3 of 9 (33%) with scar size of 30% to 49% and 5 of 7 (78%) with scars >or=50%. In conclusion, persistent anterior STE is associated with the size of myocardial scar detected using MRI.