Association between QTd, Tp-e/QT Ratio and In-hospital Prognosis in Thrombolysed Acute ST-elevation Myocardial Elevation (STEMI) Patients

Background: Both QTd and Tp-e/QT ratio have been linked to increased risk for arrhythmia and mortality. But Significance of QTd in STEMI Patients is not documented in all studies and Tp-e/QT ratio is a novel index which is understudied in these patients. Therefore, the present study is aimed to determine the short term, in-hospital prognostic value of QTd and Tp-e/QT ratio in thrombolysed STEMI patients. Methods: This is a prospective, observational study that includes 321 patients. Relevant clinical data is collected. QTd and Tp-e/QT ratio (tangent method) is calculated from “at admission ECG” just before thrombolysis. Multivariate logistic regression analysis was done to determine the predictors of in-hospital outcomes. A p-value of <0.05 is considered statistically significant. Results: The mean age of study population was 56.72 ± 11.36 with males:females ratio of 2.73:1. Mean value of QTd and Tp-e/QT ratio were 80.29 ±10.2 ms and 0.28 ± 0.05 respectively. The QTd and Tp-e/QT ratio are found to be independent predictors of in MACE, in addition to absence of beta-blocker therapy at admission, AWMI. Tp-e/QT ratio is independent predictor of in-hospital mortality in addition to reduced LVEF and AWMI. Analysis of the ROC curve demonstrated that the optimal cut-off value for in-hospital outcomes was a Tp-e/QT ratio of ≥0.30. Conclusion: Both QTd and Tp-e/QT ratio may serve as a prognostic predictors of in hospital MACE independently but only Tp-e/QT ratio predicts patients with in-hospital all cause mortality in thrombolysed STEMI patients. Editorial Viewpoint • Q T d a n d T p e / Q T ratio have been linked t o i n c r e a s e d r i s k f o r arrhythmia and mortality. • Th is s tudy f inds tha t Tp-e/QT ratio predicts i n h o s p i t a l a l l c a u s e mortality in thrombolysed STEMI patients. arrhythmias namely ventricular tachycardia (VT) and ventricular fibrillation (VF). Inves t iga tors have focused o n t h e e l e c t r o p h y s i o l o g i c a l characterization of arrhythmogenic substrates in the myocardium o f A M I p a t i e n t s , s u c h a s Q T interval and T wave. These studies have shown clinical promise for predicting malignant arrhythmias a n d s u d d e n c a r d i a c d e a t h (SCD).1–3 P r e v i o u s l y m a n y o f t h e c o n t e m p o r a r y s t u d i e s g a v e impor tance to QT d ispers ion ( Q Td ) f o r q u a n t i f y i n g t h e arrhythmogenesis substrate than QT interval because QT interval shows certain degree of interlead spatial variability and thus serves as an index of the spatial d i spers ion o f the ventr i cu lar recovery times.4 Consequently, Introduction A Myocardial infarction ( A M I ) r e p r e s e n t s o n e o f the catastrophic events in the natural history of coronary artery disease (CAD). Despite remarkable advances in the treatment of AMI the occurrence of AMI is associated with substantial early and late mortality, In majority of cases both early (out and in-hospital) and late mortality is attributed to two main sequel of acute coronary occlusion namely pump failure and arrhythmogenesis. Predominant arrhythmic events, attr ibuting to this burden are ventricular Journal of The Association of Physicians of India ■ Vol. 65 ■ October 2017 35 QT dispersion is regarded almost a direct measure of the heterogeneity of myocardial repolarizat ion. 5 This QTd is was used clinically in many situations.6,7 However, not all studies demonstrated this clinical usefulness of QT dispersion,8-10 causing it to call as ‘the greatest fallacy in electrocardiography in the 1990s” by few researchers.11 Recently, the Interval from the peak to the end the T wave (T peak-Tend interval [Tp-e]) was used in predicting arrhythmias and Sudden cardiac death (SCD) in some cardiac channelopathies.12-14 S t u d i e s s h o w n t h a t t h e Tp e interval may serve as an index of total dispersion of repolarization ( t ransmural , apico-basal , and global). As body weight and heart rate (HR) increases, there is a linear increase in the QT interval and is accompanied by a parallel increase in the Tp-e interval. Hence the Tp-e/QT ratio remains shows consistency within the narrow range of 0.15 to 0.25. A higher Tp-e/QT ratio has been associated with arrhythmic events associated with many clinical conditions.15 However, little is known about this index in patients with STEMI undergoing thrombolysis. Therefore, the present study is aimed to evaluate the QTd and Tp-e/QT ratio immediately before thrombolysis in pat ients with STEMI and to determine their short term prognostic value.