ECG scar quantification correlates with cardiac magnetic resonance scar size and prognostic factors in Chagas' disease

Objective: To test the hypothesis that 12-lead ECG QRS scoring quantifies myocardial scar and correlates with disease severity in Chagas' heart disease. Design: Patients underwent 12-lead ECG for QRS scoring and cardiac magnetic resonance with late gadolinium enhancement (CMR-LGE) to assess myocardial scar. Setting: University of São Paulo Medical School, São Paulo, Brazil. Patients: 44 Seropositive patients with Chagas' disease without a history of myocardial infarction and at low risk for coronary artery disease. Main outcome measures: Correlation between QRS score, CMR-LGE scar size and left ventricular ejection fraction. Relation between QRS score, heart failure (HF) class and history of ventricular tachycardia (VT). Results: QRS score correlated directly with CMR-LGE scar size (R=0.69, p<0.0001) and inversely with left ventricular ejection fraction (R=-0.54, p=0.0002), which remained significant in the subgroup with conduction defects. Patients with class II or III HF had significantly higher QRS scores than those with class I HF (5.1±3.4 vs 2.1±3.1 QRS points (p=0.002)) and patients with a history of VT had significantly higher QRS scores than those without a history of VT (5.3±3.2% vs 2.6±3.4 QRS points (p=0.02)). A QRS score ≥2 points had particularly good sensitivity and specificity (95% and 83%, respectively) for prediction of large CMR-LGE, and a QRS score ≥7 points had particularly high specificity (92% and 89%, respectively) for predicting significant left ventricular dysfunction and history of VT. Conclusions: The wide availability of 12-lead ECG makes it an attractive screening tool and may enhance clinical risk stratification of patients at risk for more severe, symptomatic Chagas' heart disease.