Abstract
BACKGROUND: Cardiac MRI (CMR) markers of myocardial fibrosis and infiltration are diagnostically and prognostically important in cardiomyopathies. A noninvasive ECG correlate of CMR interstitial fibrosis measurements (extracellular volume [ECV] and native T1) could assist in diagnosis, risk stratification, and tracking disease progress. The spatial ventricular gradient (SVG) is a vectorcardiographic (VCG) measure of electrical heterogeneity obtained from a 12-lead ECG. The link between the SVG and CMR-derived myocardial interstitial fibrosis is unknown.
METHODS: Retrospective study of patients referred for CMR from 2018-2022 at a single academic center, with an ECG performed within 30 days. VCGs were constructed from 12-lead ECGs, and SVG vector components were calculated. ECV and T1 values were regressed on SVG components, demographics, and ECG parameters using linear regression.
RESULTS: In total, 345 patients met inclusion criteria: 55% male, median age 60.2 (P25-P75 47.4-69.9) years, and median LVEF 57 (P25-P75 44-63)%. Median SVG magnitude was 39.5 (P25-P75 28.2-58.2) mV∙ms and SVG magnitude was inversely correlated with ECV and T1 (p < 0.001 for both). In a multivariable model, SVG magnitude remained independently associated with ECV and T1 after adjustment for body mass index, LVEF, age, and sex (p < 0.01). Patients with amyloid cardiomyopathy had the most abnormal values of ECV and T1; no amyloid patient had SVG magnitude > 50 mV∙ms.
CONCLUSION: SVG magnitude is correlated with CMR-derived ECV and native T1. Patients with high SVG magnitude were not observed to have a large burden of diffuse fibrosis or infiltration.