Asymmetric septal hypertrophic cardiomyopathy: MRI patterns

Clinical History

A 50-year-old male patient was admitted for assessment of a myocardial hypertrophy diagnosed with cardiac ultrasound.

Imaging Findings

We performed a cardiac ECG-gated MRI on a 1.5 T system (Siemens) with CINE-MR sequences in the short axis, 3 chamber, 2 chamber and 4 chamber, T2 STIR, T1 mapping, FLASH perfusion and delayed enhancement. The cardiac MRI showed isolated hypertrophy of the septal wall of the LV. Its thickness was 31 mm (Fig. 1). LV was non-dilated and hyperdynamic with an abnormal ejection fraction (78%). Cine MR demonstrated anterior motion of the mitral leaflet in the systolic phase with a turbulent low signal jet in the obstructed LVOT (Fig. 2). There was diffuse late gadolinium enhancement of the anteroapical and anteroseptal mid segments of the LV. The septal hypertrophic segment (both basal and mid) was free of late enhancement, which characterized a pattern of an unusual presentation (Fig. 3). However, T1 value was 1069 ms in the septal LV wall on mapping sequences (Fig. 4).

Discussion

Hypertrophic cardiomyopathy (HCM) is a common genetic disorder with an estimated prevalence of 1:500. It is defined as a diffuse or segmental left ventricular hypertrophy with non-dilated and hyperdynamic chamber in the absence of another disease capable of producing that grade of hypertrophy [1].
Asymmetrical septal hypertrophy is the most common morphologic presentation of HCM. Usually, patients have no or only minor symptoms (dyspnoea, chest pain, palpitation, syncope and lipothymia). Sudden cardiac death may be the initial presentation.
Echocardiography is occasionally limited by poor acoustic windows, incomplete visualization of the left ventricular wall, and inaccurate evaluation of left ventricular mass. Cardiac MR is a valuable complementary technique to the cardiac ultrasound.
The diagnostic criteria of asymmetric HCM are septal LV wall thickness ≥ 15 mm in end diastole or ratio of septal wall/lateral wall thickness greater than 1.5 at mid-ventricular level [2]. The hypertrophic myocardium does not contract normally. Delayed enhancement tends to involve the interventricular septum, particularly the anteroseptal mid to basal segments.
Cardiac MR depicts cardiovascular risk stratification. The patient under discussion had classical markers of high risk for sudden death, such as myocardial thickness ≥ 30 mm, myocardial hyperenhancement [3] and obstruction of the LV outflow tract [4]. The detection of myocardial fibrosis in HCM using the late enhancement technique is believed to be the anatomical substrate for the occurrence of malign ventricular tachyarrhythmias [5]. T1 mapping imaging can be also a useful method to evaluate fibrosis in HCM patients because of a variable degree of fibrosis in the involved myocardium [6], such as in our case.
Cardiac MR is util in the diagnosis, therapeutic planning and prognostication of HCM. It has the potential to give to physician important information for risk stratification.

Differential Diagnosis List

Final Diagnosis

Asymmetric hypertrophic cardiomyopathy

URL:	https://eurorad.org/case/12091
DOI:	10.1594/EURORAD/CASE.12091
ISSN:	1563-4086