Improving sudden cardiac death risk stratification by evaluating electrocardiographic measures of global electrical heterogeneity and clinical outcomes among patients with implantable cardioverter-defibrillators: rationale and design for a retrospective, multicenter, cohort study

Abstract

Purpose: Implantable cardioverter-defibrillators (ICDs) improve survival of systolic heart failure (HF) patients who are at risk of sudden cardiac death (SCD). We recently showed that electrocardiographic (ECG) global electrical heterogeneity (GEH) is independently associated with SCD in the community-dwelling cohort and developed GEH SCD risk score. The Global Electrical Heterogeneity and Clinical Outcomes (GEHCO) study is a retrospective multicenter cohort designed with two goals: (1) validate an independent association of ECG GEH with sustained ventricular tachyarrhythmias and appropriate ICD therapies and (2) validate GEH ECG risk score for prediction of sustained ventricular tachyarrhythmias and appropriate ICD therapies in systolic HF patients with primary prevention ICD.

Methods: All records of primary prevention ICD recipients with available data for analysis are eligible for inclusion. Records of ICD implantation in patients with inherited channelopathies and cardiomyopathies are excluded. Raw digital 12-lead pre-implant ECGs will be used to measure GEH (spatial QRST angle, spatial ventricular gradient magnitude, azimuth, and elevation, and sum absolute QRST integral). The primary endpoint is defined as a sustained ventricular tachyarrhythmia event with appropriate ICD therapy. All-cause death without preceding sustained ventricular tachyarrhythmia with appropriate ICD therapy will serve as a primary competing outcome. The study will draw data from the academic medical centers.

Results: We describe the study protocol of the first multicenter retrospective cohort of primary prevention ICD patients with recorded at baseline digital 12-lead ECG.

Conclusion: Findings from this study will inform future trials to identify patients who are most likely to benefit from primary prevention ICD.

Trial registration: URL: http://www.clinicaltrials.gov . Unique identifier: NCT03210883.

Keywords: Electrocardiogram; Implantable cardioverter-defibrillators; Risk stratification; Sudden cardiac death; Vectorcardiogram; Ventricular arrhythmias.

Figure 1.

Retrospective Follow-Up timeline

Figure 2.

Schematic presentation of the study

Figure 3:

Measurement of global electrical heterogeneity parameters: A. Spatial QRS-T angle is the angle between the QRS vector and the T vector in 3-dimensional space. Spatial ventricular gradient (SVG) is a vector defined as the vector sum of the mean QRS and the mean T vectors. SVG has a magnitude which is the length of the vector, elevation (the angle of the SVG vector projected in the XY plane), and azimuth (the angle of the SVG vector projected in the XZ plane). B. Sum Absolute QRST Intergral (SAI QRST) is the sum of the absolute area under the entire QRST complex in the X, Y, and Z leads. C. Circular coordinates system for measurement of azimuth and elevation.