The spatial ventricular gradient is a non-invasive, vectorcardiographic correlate of cardiac fibrosis

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.

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.

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.

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.