Electrocardiographic Impact of Myocardial Diffuse Fibrosis and Scar: MESA (Multi-Ethnic Study of Atherosclerosis)

Purpose: To examine the associations of myocardial diffuse fibrosis and scar with surface electrocardiographic (ECG) parameters in individuals free of prior coronary heart disease in four different ethnicities. Materials and Methods: This prospective cross-sectional study was approved by the institutional review boards, and all participants gave informed consent. A total of 1669 participants in the Multi-Ethnic Study of Atherosclerosis, or MESA, who were free of prior myocardial infarction underwent both ECG and cardiac magnetic resonance imaging. In individuals without a late gadolinium enhancement-defined myocardial scar (n = 1131), T1 mapping was used to assess left ventricular (LV) interstitial diffuse fibrosis. The associations of LV diffuse fibrosis or myocardial scar with ECG parameters (QRS voltage, QRS duration, and corrected QT interval [QTc]) were evaluated by using multivariable regression analyses adjusted for demographic data, risk factors for scar, LV end-diastolic volume, and LV mass. Results: The mean age of the 1669 participants was 67.4 years 6 +/- 8.7 (standard deviation); 49.8% were women. Lower postcontrast T1 time at 12 minutes was significantly associated with lower QRS Sokolow-Lyon voltage (beta = 15.1 mu V/10 msec, P = .004), lower QRS Cornell voltage (beta = 9.2 mu V/10 msec, P = .031), and shorter QRS duration (beta = 0.16 msec/10 msec, P = .049). Greater extracellular volume (ECV) fraction was also significantly associated with lower QRS Sokolow-Lyon voltage (beta = 235.2 mu V/1% ECV increase, P < .001) and Cornell voltage (beta = 223.7 mu V/1% ECV increase, P,.001), independent of LV structural indexes. In contrast, the presence of LV scar (n = 106) was associated with longer QTc (beta = 4.3 msec, P = .031). Conclusion: In older adults without prior coronary heart disease, underlying greater LV diffuse fibrosis is associated with lower QRS voltage and shorter QRS duration at surface ECG, whereas clinically unrecognized myocardial scar is associated with a longer QT interval. (C) RSNA, 2016