Prognostic value of T peak-to-end interval for risk stratification after acute myocardial infarction

Aim

Fatal arrhythmia is the main cause of sudden death in patients with acute myocardial infarction either during hospital admission or in post-discharge period. Our aim is to identify groups at high risk of arrhythmic mortality by using a simple bed-side test in electrocardiogram.

Background

Trans-mural dispersion of repolarization (TDR) in patients with ST elevation myocardial infarction is the main trigger of arrhythmias. The potential value of measuring the interval between the peak and end of the T wave (Tpeak-Tend, Tp-Te) as an index of spatial dispersion of repolarization is a parameter thought to be capable of reflecting dispersion of repolarization and thus may be prognostic tool for detection of arrhythmic risk. Little is known about its use for identifying risk of arrhythmias in acute myocardial infarction and this must be approached with great caution and require careful validation.

Methods

A prospective analysis of data from 564 patients admitted to our CCU by acute myocardial infarction along a period of two years from January 2012 to December 2013 was done. After exclusion of valvular, congenital lesions, HOCM, IDCM, pericardial diseases, accessory pathway, any Bundle branch block, metabolic disorders and re-perfusion arrhythmia. Analysis of TpTe interval and its dispersion were done for all patients and a Holter-24 h was performed after one month. Patients were then classified into two groups based on Lown grading score for arrhythmia: group (I) (441 patients) with no or minimal arrhythmias (Lown score <3), and group (II) (123) with high grade arrhythmias (Lown score ⩾3). In-hospital predischarge echocardiography was done for all patients to evaluate left ventricular functions and presence of myocardial aneurysm. Signal average ECG was done to detect low amplitude signals (LAS). Pre-discharge coronary angiography was done for all patients.

Results

Statistical analysis of the results revealed that, group (II) patients carry a significantly higher number of obese, diabetic, and hypertensive patients. Most of patients in this group were smokers, having higher creatinine levels, and exposed previously to cerebral insults in significantly higher values than group (I). Also, group (II) patients need significantly higher doses of diuretic and ACEIs than group (I). The percentage of anterior wall infarction is significantly higher in group (II), with higher inferior wall affection in group (I). TpTe interval and dispersion between both groups revealed that, a higher TpTe interval was found in group (II) than group (I) and this was linked to occurrence of sudden death or malignant VT and deterioration in Lv functions than in group (I). Also, patients in group (II) exposed to re-infarction and cardiogenic shock in statistically significant values (P < 0.01) than group (I).

Conclusion

TpTe was significantly and independently associated with increased odds of SCD and is linked to deterioration of Lv functions and myocardial aneurysms. It's highly correlated to presence of LAS and associate with severity of coronary lesions. Patients with prolonged TpTe intervals and dispersions were likely to develop fatal arrhythmias.