ST-segment elevation on Q-leads during exercise in patients with ST-segment elevation at rest after myocardial infarction.

INTRODUCTION: ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infarct size. The meaning of a further exercise-induced ST-segment elevation in these patients has not been analyzed. METHOD: Thirty-six patients with ST-segment elevation on Q-leads were studied after a first acute myocardial infarction. Exercise testing and cardiac catheterization were performed at the first week. Left ventricular volumes (ml/m(2)); the extent of abnormal wall motion (AWM: chords); contractile reserve (AWM improvement with low dose dobutamine) and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 20 patients; systolic recovery (AWM improvement), left ventricular volumes and coronary patency were again evaluated. RESULTS: Patients with exercise-induced ST-segment elevation in two or more Q-leads (n=21) showed lesser contractile reserve (6+/-6 vs. 12+/-7 chords, P=0.01) than patients without exercise-induced ST-segment elevation (n=13). AWM (F=8.1) and absence of exercise-induced ST-segment elevation (F=9.5; positive predictive value: 80%; negative predictive value: 68%) were the only independent predictors of contractile reserve. Nevertheless, this electrocardiographic sign was not related to left ventricular volumes, coronary patency or systolic function and it did not predicted late systolic recovery. CONCLUSIONS: In patients with baseline ST-segment elevation on Q-leads an exercise-induced ST-segment elevation is independently related to a lesser contractile reserve but not to the evolution of volumes or regional dysfunction during the first 6 months post-infarction. Therefore, the clinical value of this sign seems to be limited to the non-invasive detection of myocardial viability during the early post-infarction phase.

QT dispersion within the first 6 months after an acute myocardial infarction: relationship with systolic function, left ventricular volumes, infarct related artery status and clinical outcome.

INTRODUCTION: We analysed QT dispersion within the first 6 months postinfarction, its relationship with the main established risk stratifiers and its clinical value. METHODS AND RESULTS: In 55 patients with a first Q-wave myocardial infarction the 12-lead electrocardiogram was scanned and digitised for analysis of QT dispersion (QT maximum-QT minimum) at first day (72 [61-96] ms), first week (69 [47-90] ms), first month (67 [46-88] ms) and sixth month (47 [40-74] ms; P<0.0001 vs. first day). Cardiac catheterization was performed at first week and at sixth month; QT dispersion was not related to ejection fraction, left ventricular volumes, infarct related artery status or contractile reserve (improvement of the infarcted area with low-dose dobutamine); no relation was found between QT dispersion decrease from first week to sixth month with regional systolic function improvement. Finally, during a mean follow-up period of 35+/-22 months QT dispersion was not independently related to clinical events. CONCLUSION: QT dispersion decreases progressively during the first months after myocardial infarction. These changes should be taken into account to define cut-off values of clinical interest in this phase. This variable does not seem related to the classic prognosis predictors. In a nonselected postinfarction population it has a low clinical value.