Stretch the heart: Get memory

Abstract

T-wave memory is a commonly observed clinical phenomenon that refers to T-wave changes that persist after cessation of altered ventricular electrical activation, i.e. pacing or intra-ventricular conduction delay. 1 Rosenbaum M.B. Blanco H.H. Elizari M.V. et al. Electrotonic modulation of the T wave and cardiac memory. Am J Cardiol. 1982; 50: 213-222 Abstract Full Text PDF PubMed Scopus (337) Google Scholar Although altered ventricular electrical activation was initially thought to be a benign phenomenon, there is increasing recognition of its pathological consequences. In the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II trial, despite improved mortality from ICD therapy, there was worsening heart failure due to right ventricular (RV) pacing. 2 Moss A.J. Zareba W. Hall W.J. et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002; 346: 877-883 Crossref PubMed Scopus (5587) Google Scholar In the Dual Chamber And VVI Implantable Defibrillator (DAVID) trial, increased duration of RV pacing resulted in increased mortality. 3 Wilkoff B.L. Cook J.R. Epstein A.E. et al. DAVID Trial InvestigatorsDual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator - The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA. 2002; 288: 3115-3123 Crossref PubMed Scopus (1685) Google Scholar In contrast, therapeutic use of Bi-Ventricular pacing in heart failure improves synchrony of electrical activation and improves survival. 4 Bristow M.R. Saxon L.A. Boehmer J. et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. N Engl J Med. 2004; 350: 2140-2150 Crossref PubMed Scopus (4756) Google Scholar , 5 Cleland J.G. Daubert J.C. Erdmann E. et al. The effect of cardiac resynchronization on morbidity and mortality in heart failure. N Engl J Med. 2005; 352: 1539-1549 Crossref PubMed Scopus (5166) Google Scholar Although still incompletely understood, the pathophysiology induced by altered electrical activation is due to dyssynchronous activation of the ventricle compared to synchronous His-Purkinje activation, resulting in dyssynchronous contraction, 6 Curry C.W. Nelson G.S. Wyman B.T. et al. Mechanical dyssynchrony in dilated cardiomyopathy with intraventricular conduction delay as depicted by 3D tagged magnetic resonance imaging. Circulation. 2000; 101: E2 Crossref PubMed Google Scholar reducing pump efficiency, and inducing deleterious electrical remodeling. There is growing evidence for the primary role of mechanical effects of altered activation as a mechanism triggering electrical remodeling in the heart that is observed as T-wave memory on the surface ECG. 7 Jeyaraj D. Wilson L.D. Zhong J. et al. Mechanoelectrical feedback as novel mechanism of cardiac electrical remodeling. Circulation. 2007; 115: 3145-3155 Crossref PubMed Scopus (101) Google Scholar