ST-segment elevation on Q leads at rest and during exercise: relation with myocardial viability and left ventricular remodeling within the first 6 months after infarction.

BACKGROUND

Resting ST-segment elevation on Q leads after an acute myocardial infarction has been related to a greater infarct size. Otherwise, the relation between exercise-induced ST-segment elevation and myocardial viability is controversial. We investigated the relation between ST-segment elevation on Q leads at rest and during exercise and regional dysfunction and its evolution, contractile reserve, left ventricular dilation, and coronary patency.

METHODS AND RESULTS

Exercise testing and cardiac catheterization were performed at the first week after infarction in 51 patients. The study group was divided according to the existence (in 2 or more Q leads; n = 36) or not (n = 15) of resting ST-segment elevation and according to the existence (n = 28) or not (n = 23) of exercise-induced ST-segment elevation. Left ventricular end-diastolic and end-systolic volumes (mL/m2), regional wall motion (SD/chord), contractile reserve (wall motion percentage improvement with low-dose dobutamine), and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 35 patients; systolic recovery (wall motion percentage improvement), left ventricular volumes, and coronary patency were again evaluated. Patients with resting ST-segment elevation showed poorer wall motion (2.1 +/- 0.8 SD/chord vs 1.2 +/- 1 SD/chord, P =.002), lesser contractile reserve (17% [0% to 39%] vs 41% [4% to 92%], P =.04), greater end-systolic volume (32 +/- 15 mL/m2 vs 23 +/- 11 mL/m2, P =.04), and higher percentage of occlusion (36% vs 7%, P =.04) than did patients without ST-segment elevation. Likewise, patients with exercise-induced ST-segment elevation showed lesser contractile reserve (8% [0% to 40%] vs 35% [12% to 86%], P =.03) than did patients without exercise-induced ST-segment elevation. The only independent predictors of contractile reserve were wall motion <2 SD/chord (odds ratio [OR] 7.1, confidence interval [CI] 6.3 to 7.9, P =.01) and the absence of exercise-induced ST-segment elevation (OR 5.7, CI 4.9 to 6.5, P =. 02). There were no significant differences between patients with and those without ST-segment elevation (at rest or during exercise) in systolic recovery or left ventricular volumes at the sixth month.

CONCLUSIONS

ST-segment elevation on Q leads at rest is related to a poorer systolic function (more severe regional dysfunction, greater end-systolic volume, and less response to dobutamine). ST-segment elevation during exercise is independently related to a lesser contractile reserve. ST-segment elevation (at rest or during exercise) is not related to the evolution of volumes or regional dysfunction during the first 6 months after infarction.