The prognostic value of ventricular repolarization
Al-Zaiti, Salah Shafiq
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Background: The electrocardiogram (ECG) has been proven valuable as a non-invasive prognostic tool in different populations. However, despite its astonishing history, experts sometimes refer to it as frustrating. The evidence regarding its prognostic magnitudes is contradictory and there is no general consensus on their clinical utility. Currently, there are no previous meta-analyses in this regard to weigh the evidence and guide clinical practice. Methods: First, the prognostic magnitudes of many well-known ECG abnormalities were prospectively evaluated in 204 ischemic cardiomyopathy patients using cox-proportional hazards regression model. Second, the total prognostic magnitudes of repolarization abnormalities were synthesized from 116 primary studies using random effect models with age, sex, and diagnosis treated as moderators. Finally, the use of quality-adjusted weighting approach on the precision and magnitude of total estimates was investigated. Results: First, prolonged QTc interval and depressed heart rate variability (HRV) were predictive of sudden and non-sudden cardiac mortalities in ischemic cardiomyopathy patients. Second, ECG repolarization abnormalities were valuable predictors of disease specific mortalities, but not all cause death. These abnormalities were particularly useful in younger adults, women, and the general population. Finally, incorporating quality scores in statistical pooling significantly impacted the magnitude of total estimates and reduced their precision. Meta-analyses with higher quality scores, less variations in their quality scores, larger number of studies, or larger pooled sample size were more robust. Conclusions: The ECG can identify patients who might benefit from implantable- cardioverter defibrillators and bi-ventricular pacing. Clinicians need to redefine the use of ECG for disease-specific risk assessment taking into account patient's age, sex, and diagnosis. Quality weight in meta-analysis is essential especially in small meta-analyses with questionable quality.