Misclassification of recovery in dilated cardiomyopathy by echocardiography as compared to cardiac MRI.

Accurate assessment of cardiac function is the cornerstone of DCM diagnosis and management. Studies have compared CMR and 2D-TTE but the impact of these measurements on HF classification and assessment of EF improvement has not been explored. We aim to compare left ventricular (LV) ejection fraction (EF) and volumes as measured by cardiovascular magnetic resonance (CMR) and two dimensional (2D) transthoracic echocardiography (TTE) in dilated cardiomyopathy (DCM) patients in the initial EF based classification of heart failure (HF) and subsequent follow-up.We compared LVEF, LV end-diastolic volume (LVEDV) and LV end-systolic volumes (ESV) measurements from 130 DCM patients during both their initial visit and their follow-up imaging 12-48 months later. We also assessed the myocardial recovery of patients who were classified as having HFimpEF (EF < 40% to EF ≥ 40% with at least a 10% increase in EF) by 2D-TTE and CMR. We found that 2D-TTE overestimated EF (8.3% (95% CI 7.2 to 9.4), p < 0.001) and underestimated LVEDV (-69.0 ml (95% CI -77.0 to -61.1), p < 0.001) and LVESV (-64.8 ml (95% CI -71.6 to -57.9) p < 0.001) as compared to CMR. The overestimation of EF was not uniform across the EF spectrum. The lower the LVEF, the greater the overestimation by TTE. This overestimation led to an initial misclassification of 60% of HFrEF patients and a subsequent misclassification of myocardial recovery in 59% of DCM patients. 2D-TTE misclassification of DCM patients may significantly impact the initial treatment choice and follow-up of heart failure patients.