Magnetic Resonance for Differential Diagnosis of Left Ventricular Hypertrophy: Diagnostic and Prognostic Implications

Abstract

Background: Left ventricular hypertrophy (LVH) may be due to different causes, ranging from benign secondary forms to severe cardiomyopathies. Transthoracic Echocardiography (TTE) and ECG are the first-level examinations for LVH diagnosis. Cardiac magnetic resonance (CMR) accurately defines LVH type, extent and severity.

Objectives: to evaluate the diagnostic and prognostic role of CMR in patients with TTE and/or ECG evidence of LVH.

Methods: We performed CMR in 300 consecutive patients with echocardiographic and/or ECG signs of LVH.

Results: Overall, 275 patients had TTE evidence of LVH, with initial suspicion of hypertrophic cardiomyopathy (HCM) in 132 (44%), cardiac amyloidosis in 41 (14%), hypertensive LVH in 48 (16%), aortic stenosis in 4 (1%), and undetermined LVH in 50 (16%). The initial echocardiographic diagnostic suspicion of LVH was confirmed in 172 patients (57.3%) and changed in 128 patients (42.7%, p < 0.0001): the diagnosis of HCM increased from 44% to 71% of patients; hypertensive and undetermined LVH decreased significantly (respectively to 4% and 5%). CMR allowed for a diagnosis in 41 out of 50 (82%) patients with undetermined LVH at TTE. CMR also identified HCM in 17 out of 25 patients with apparently normal echocardiography but with ECG criteria for LVH. Finally, the reclassification of the diagnosis by CMR was associated with a change in survival risk of patients: after CMR reclassification, no events occurred in patients with undetermined or hypertensive LVH.

Conclusions: CMR changed echocardiographic suspicion in almost half of patients with LVH. In the subgroup of patients with abnormal ECG, CMR identified LVH (particularly HCM) in 80% of patients. This study highlights the indication of CMR to better characterize the type, extent and severity of LVH detected at echocardiography and suspected with ECG.

Keywords: echocardiography; left ventricular hypertrophy; magnetic resonance; prognosis.

Figure 1

The left graph shows the distribution of initial diagnostic suspicion by transthoracic echocardiography (TTE). The right graph shows the reclassification of diagnosis by cardiac magnetic resonance (CMR). As evident by the comparison of the two graphs, CMR allowed a significant decrease in cases with undetermined left ventricular hypertrophy (LVH), as well a decrease in the percentage of hypertensive LVH. HCM, hypertrophic cardiomyopathy.

Figure 2

Cardiac Magnetic Resonance of 3 different cases of left ventricular hypertrophy: The upper panels show a case of hypertensive left ventricular hypertrophy (LVH) with concentric hypertrophy, normal native T1 values and negative late gadolinium enhancement (LGE). The middle panels show a case of hypertrophic cardiomyopathy (HCM) with asymmetrical LVH, focal areas of myocardial fibrosis at LGE and focal increase in native T1 corresponding to the fibrotic areas. Finally, a case of cardiac amyloidosis is reported in the lower panels. In this case, LVH is concentric, native T1 is diffusely increased and a diffuse subendocardial enhancement was found at LGE. SSFP, steady state free precession.

Figure 3

Cardiac Magnetic Resonance of a patient with Fabry disease: This was a case of a 70-year-old male with apparently asymmetrical LVH, with extensive LGE in the lateral wall but with low myocardial T1 in the basal septum. This latter finding suggested the diagnosis of Fabry disease with pseudonormalization of T1 in the fibrotic myocardial segment of lateral wall. The subsequent genetic evaluation confirmed the presence of a pathogenic mutation of alpha-galactosidases.

Figure 4

Kaplan–Meier curves: The graphs represent the survival-free events curve of the patients with the 4 major diagnoses in this population: hypertrophic cardiomyopathy (HCM), cardiac amyloidosis, hypertensive left ventricular hypertrophy (LVH) and undetermined LVH. The left graph shows the curves based on the initial echocardiographic suspicion, and the right graph was the result of the reclassification made by cardiac magnetic resonance (CMR). As is evident, the reclassification allowed a prognostic change in survival curves: no events occurred in patients with hypertensive LVH and those with undetermined LVH based on CMR diagnosis.