Relation between stage of left ventricular diastolic dysfunction and QT dispersion
Objective - In 30-40% of patients with clinical heart failure diastolic dysfunction is present although systolic function is normal. Evaluation of diastolic functions are important for the patient's early diagnosis, treatment and prognosis. QT dispersion is an important parameter that reflects heterogeneity of ventricular repolarization and predicts ventricular arrhythmia and sudden death. According to several studies, QT dispersion is significantly increased in patients with diastolic dysfunction due to ischemic heart disease and left ventricular hypertrophy compared to the patients without diastolic dysfunction. However, a study about the relation between the stage of left ventricular diastolic dysfunction and QT dispersion is not present. The aim of this study was to investigate the correlation between the stage of left ventricular diastolic function determined by transthoracic echocardiography and QT dispersion. Methods and Results - In our study the left ventricular diastolic functions of 80 patients were evaluated by transthoracic echocardiography. Eighty patients were divided to four stages each containing 20 patients. Stage 0 was defined as normal, stage I as prolonged relaxation pattern, stage 2 as pseudonormal pattern and stage 3 as restrictive pattern. We measured QT dispersion (QT D) and corrected QT dispersion (QTc D) values according to Bazzet's formula in their ECGs. QT D and QTc D were found 20 +/- 8 ms vs. 26 +/- 1 ms in normal patients, 25 +/- 8 ms vs. 37 +/- 9 ms in the patients with prolonged relaxation pattern, 28 +/- 10 ms vs. 38 +/- 11 ms in the patients with pseudonormal pattern and 38 13 ms vs. 41 +/- 14 ms in the patients with restrictive pattern. A significant direct relation was found between the stage of left ventricular diastolic function and QT, QTc dispersion (p<0.01). Furthermore, when classified according to the aetiology of the left ventricular diastolic dysfunction (stage 1, 2, 3) QT D and QTc D were 24 6 ms vs. 32 9 ms in the patients with left ventricular hypertrophy (LVH), and 32 +/- 9 ms vs. 41 +/- 12 ms in the patients with ischaemic heart disease (IHD). The differences between the two groups were statistically significant (p<0.01). Conclusions -These findings show that QT D and QTc dispersion values increase in relation to increasing left ventricular diastolic functional stage that is determined by echocardiography and that the patients with ischaemic heart disease have much more increased QT values than the patients with left ventricular hypertrophy.