Corrected QT-interval during one year follow-up after an acute myocardial infarction
Insights
This study found that prolonged resting QTc interval in myocardial infarction patients indicates impaired left ventricular function and predicts higher mortality. A longer QTc at rest suggests poorer heart muscle condition post-MI.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Imaging
Background:
- Myocardial infarction (MI) survivors require ongoing assessment of cardiac function and prognosis.
- The relationship between QTc interval dynamics during exercise and left ventricular ejection fraction (LVEF) post-MI is not fully understood.
Purpose of the Study:
- To investigate the correlation between QTc interval measurements (rest and exercise) and LVEF in patients following MI.
- To assess the prognostic value of QTcrest in predicting one-year mortality in post-MI patients.
Main Methods:
- Prospective study of 101 patients under 66 years old post-MI.
- Serial assessments of exercise ECG, resting technetium LVEF, QTcrest, and QTcwork at 1, 6, and 12 months post-MI.
- Statistical analysis to determine correlations and prognostic significance.
Main Results:
- Patients with lower LVEF exhibited longer QTcrest and a smaller QTc change during exercise.
- A significant negative correlation was observed between LVEF and QTcrest (r = -0.35, P < 0.001).
- QTcrest exceeding 0.480 s at initial investigation was associated with 50% one-year mortality versus 9% for shorter QTcrest (P = 0.0002).
Conclusions:
- Resting QTc interval (QTcrest) serves as a marker for left ventricular myocardial condition in post-MI patients.
- Prolonged QTcrest is indicative of impaired myocardial function and is a significant predictor of increased one-year mortality after MI.
Abstract:
One hundred and one unselected patients less than 66 years of age who had had a myocardial infarction were investigated with exercise ECG and technetium resting left ventricular ejection fraction (LVEF) within one month of the myocardial infarction (MI), and at 6 months and 12 months. QTc was measured at rest (QTcrest) and at maximal exercise (QTcwork). In patients with QTcwork less than QTcrest LVEF was found to be lower (mean 0.42) and QTcrest longer (mean 0.467 s) than in patients with QTcwork greater than QTcrest. In this latter group LVEF was 0.50 (mean value) (P less than 0.001) and QTcrest 0.426 s (mean value) (P less than 0.001). A negative correlation was found between LVEF and QTcrest, r = -0.35, P less than 0.001. A negative correlation was also found between QTcwork-QTcrest (i.e. the change in QTc during maximal exercise) and QTcrest, r = -0.69, P less than 0.001. In patients with QTcrest greater than 0.480 s at the first investigation, the one-year mortality was 50%, compared with 9% in patients with QTcrest less than 0.480 s (P = 0.0002). It is concluded that in post-MI patients, QTcrest reflects the condition of the left ventricular myocardium, a prolonged QTcrest being found with impaired myocardial function.
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