Electrocardiographic R wave amplitude in V6 lead as a predictive marker of cardiac dysfunction in Duchenne muscular dystrophy.

Purpose: Duchenne muscular dystrophy (DMD) is an inherited muscular disease characterized by progressive and fatal muscle weakness. Electrocardiographic (ECG) abnormalities, including abnormal R wave amplitudes are frequently observed in DMD. However, clinical implications of abnormal R wave amplitudes remain unclear. Hence, DMD patients were examined for changes in R wave amplitude over time using synthesized 18-lead ECG and the relationship between R wave amplitude and cardiac function.
Methods: The results of 969 ECG examinations of 193 patients with DMD who underwent electrocardiography and echocardiography on the same day were retrospectively reviewed.
Results: A negative correlation was observed between R wave amplitude and age. Positive correlations between R wave amplitude and left ventricular ejection fraction were observed in leads V4, V5, V6, syn-V7, syn-V8, and syn-V9, with V6 showing the strongest correlation (r = 0.52). Mean R wave amplitude during cardiac dysfunction was lower than that observed with preserved cardiac function in leads V6 to syn-V9. Patients had preserved R wave amplitude up to three years before the onset of cardiac dysfunction, with a sharp decrease two years before cardiac dysfunction in leads V6 to syn-V9.
Conclusions: In DMD patients, the R wave amplitude decreases with age. The sharp decline in R amplitude two years before cardiac dysfunction indicates that electrophysiological damage to the myocardium of the left ventricle lateral to the posterior wall precedes the finding of cardiac dysfunction. The R amplitude in V6 of the standard 12-lead ECG is a convenient predictive marker of cardiac dysfunction, similar to that of the 18-lead ECG.
Competing Interests: Declaration of competing interest Masafumi Matsuo is an advisor for JCR Pharmaceuticals Co., Ltd., Japan, and Daiichi Sankyo Co., Ltd. Hiroyuki Awano received consulting fees from Daiichi Sankyo Co., Ltd., Nippon Shinyaku Co., Ltd., and Takeda Pharmaceutical Company Limited, and lecture fees from Nippon Shinyaku Co., Ltd., Chugai Pharmaceutical Co. Ltd., Pfizer Japan Inc. and JCR Pharmaceuticals Co., Ltd. The other authors report no conflicts of interest.
(Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)