Background—This study probes the cellular basis for the T wave under baseline and long-QT (LQT) conditions using an arterially perfused canine left ventricular (LV) wedge preparation, which permits direct temporal correlation of cellular transmembrane and ECG events. Methods and Results—Floating microelectrodes were used to record transmembrane action potentials (APs) simultaneously from epicardial, M-region, and endocardial sites or subendocardial Purkinje fibers. A transmural ECG was recorded concurrently. Under baseline and LQT conditions, repolarization of the epicardial action potential, the earliest to repolarize, coincided with the peak of the T wave; repolarization of the M cells, the last to repolarize, coincided with the end of the T wave. Thus, the action potential duration (APD) of the longest M cells determine the QT interval and the Tpeak–Tend interval serves as an index of transmural dispersion of repolarization. Repolarization of Purkinje fibers outlasted that of the M cell but failed to r...

Cellular Basis for the Normal T Wave and the Electrocardiographic Manifestations of the Long-QT Syndrome

https://www.research.manchester.ac.uk/portal/files/58548199/Heart_Rhythm_meta_analysis_2_.pdf

The Tpeak − Tend interval as an electrocardiographic risk marker of arrhythmic and mortality outcomes: A systematic review and meta-analysis

Malignant cardiac arrhythmias which result in sudden cardiac death may be present in individuals apparently healthy or be associated with other medical conditions. The way to predict their appearance represents a challenge for the medical community due to the tragic outcomes in most cases. In the last two decades some ventricular repolarization (VR) markers have been found to be useful to predict malignant cardiac arrhythmias in several clinical conditions. The corrected QT, QT dispersion, Tpeak-Tend, Tpeak-Tend dispersion and Tp-e/QT have been studied and implemented in clinical practice for this purpose. These markers are obtained from 12 lead surface electrocardiogram. In this review we discuss how these markers have demonstrated to be effective to predict malignant arrhythmias in medical conditions such as long and short QT syndromes, Brugada syndrome, early repolarization syndrome, acute myocardial ischemia, heart failure, hypertension, diabetes mellitus, obesity and highly trained athletes. Also the main pathophysiological mechanisms that explain the arrhythmogenic predisposition in these diseases and the basis for the VR markers are discussed. However, the same results have not been found in all conditions. Further studies are needed to reach a global consensus in order to incorporate these VR parameters in risk stratification of these patients.

Ventricular repolarization markers for predicting malignant arrhythmias in clinical practice

QRS Fragmentation and the Risk of Sudden Cardiac Death in MADIT II.



Background: QRS fragmentation (fQRS) has been reported as a useful ECG parameter in predicting mortality in high-risk postinfarction patients. Its prognostic value for sudden cardiac death (SCD) and ventricular arrhythmias in ischemic cardiomyopathy (ICM) remains unknown.



Methods: MADIT II enrollment 12-lead ECGs were analyzed for fQRS defined as RSR’ patterns (≥1 R’ or notching of S or R wave) in patients with a normal QRS duration and >2 notches on the R or S wave in patients with abnormal QRS duration, present in 2 contiguous leads. Exclusion criteria included a paced rhythm and an uninterpretable or incomplete ECG. Study endpoints included SCD, SCD or appropriate implantable cardioverter defibrillator (ICD) shock, and total mortality (TM).



Results: Of the 1,232 ECGs reviewed, 1,040 were of suitable quality for fQRS analysis. QRS fragmentation was found in 33% of patients in any leads, in 10% of patients in anterior leads, in 8% of patients in lateral leads and in 21% of patients in inferior leads. Anterior and lateral location of QRS fragmentation was not associated with follow-up events. Inferior location of fQRS was found to be predictive of SCD/ICD shock (hazard ratio [HR] 1.46, P = 0.032), SCD (HR 2.05, P = 0.007), and TM (HR 1.44, P = 0.036). This association was driven primarily by the increase in events found in LBBB patients: SCD/ICD shock (HR 2.05, P = 0.046), SCD (HR 4.24, P = 0.002), and TM (HR 2.82, P = 0.001).



Conclusions: Fragmented QRS, especially identified in inferior leads, is predictive of SCD, SCD or appropriate ICD shock, and all-cause mortality in patients with ICM. Identifying inferior fQRS in patients with LBBB is of particular prognostic significance and should reinforce the use of ICD therapy in this high-risk group. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1343-1348, December 2012)

QRS fragmentation and the risk of sudden cardiac death in MADIT II.

https://www.heartrhythmjournal.com/article/S1547-5271(15)00545-7/pdf

T-peak to T-end interval for prediction of ventricular tachyarrhythmia and mortality in a primary prevention population with systolic cardiomyopathy

AimsThe interval between the T-wave's peak and end (Tpe), an electrocardiographic (ECG) index of ventricular repolarization, has been proposed as an indicator of arrhythmic risk. We aimed to clarify the clinical usefulness of Tpe for risk stratification. Methods and resultsWe evaluated 327 patients with left ventricular ejection fraction (LVEF) ≤35 (75 male, LVEF 23 ± 7). All patients had an implanted implantable cardioverter- defibrillator (ICD). Clinical data and ECGs were analysed at baseline. Prospective follow-up for the endpoints of appropriate ICD therapy and mortality was conducted via periodic device interrogation, chart review, and the Social Security Death Index. During device clinic follow-up of 17 ± 12 months, 59 (18) patients had appropriate ICD therapy, and during mortality follow-up of 30 ± 13 months, 67 (21) patients died. A longer Tpec predicted appropriate ICD therapy, death, and the combination of appropriate ICD therapy or death (P< 0.01 for each endpoint). On multivariable analysis correcting for other univariable predictors, Tpec remained predictive of ICD therapy [hazard ratio (HR) per 10 ms increase: 1.16, P=0.02], all-cause mortality (HR per 10 ms: 1.14, P=0.03), and the composite endpoint of ICD therapy or death (HR per 10 ms: 1.16, P< 0.01). ConclusionsIn patients with left ventricular systolic dysfunction and an implanted ICD, Tpec independently predicts both ventricular tachyarrhythmia and overall mortality.

/pdf/relationships-between-the-t-peak-to-t-end-interval-4lors2qkpy.pdf

Onajefe S. Nelson-Twakor

Papers

Relationships between the T-peak to T-end interval, ventricular tachyarrhythmia, and death in left ventricular systolic dysfunction