Teaching Case

79-year-old-female. Previous history of hypertension, dyslipidemia and treated breast cancer. She presents to the emergency department for central, sharp, non-radiating chest pain and intermittent palpitations. ECG shows normal sinus rhythm with no ST-T changes. Chest x-ray and labs including initial troponin were within normal limits. The impression was of an episode of low risk chest pain, brief palpitation and hypertension. The patient felt improved in the emergency room and she was discharged. An echocardiogram was requested in an outpatient basis.

On the echocardiogram, there was normal left ventricular size and systolic function (LVEF>55%). Normal diastolic function. Normal right ventricular size and systolic function. A well-defined, rounded echogenic mass measuring 16 x 16 mm in the mid posterior left ventricular wall was identified.

A cardiac MRI was performed to further characterize the “mass” seen in the echocardiogram. On the cardiac MRI, there was normal left ventricular (LV) size and normal ejection fraction (LVEF 68%).

Asymmetric thickening of the left ventricular mid to apical lateral myocardial wall with normal myocardial contraction. The maximum end-diastolic wall thickness was 15 mm. On first-pass perfusion imaging, the affected region demonstrated similar perfusion pattern as the background myocardium. On late gadolinium enhancement (LGE) imaging, there was ill-defined intermediate signal intensity LGE in keeping with non-ischemic scar. Otherwise, no myocardial mass was identified. No evidence of diffuse fibrosis or edema on tissue mapping in the remote LV myocardium. The imaging findings favored "mass-like" hypertrophic cardiomyopathy (HCM). In retrospect, this finding was present in a previous abdominal MRI from 2017 (only seen in the non-diagnostic scout images), and correlated with the findings seen in the echocardiogram.

HCM is a common genetic cardiovascular disorder affecting to about 0.2% of the general population [1]. It is defined as unexplained LV hypertrophy associated with nondilated ventricles in the absence of another cardiac or systemic disease that itself would produce LV hypertrophy. Pathophysiologically, there is a combination of abnormalities including LVOT obstruction, mitral regurgitation, myocardial fibrosis, and arrhythmias and clinically, that can lead to sudden cardiac death, heart failure and atrial fibrillation (2). The therapeutic options in HCM include ICDs for secondary or primary prevention of sudden death, drugs appropriate to control heart failure symptoms, surgical septal myectomy, alcohol septal ablation, and heart transplantation [2, 3, 4].

An important diagnostic criterion of HCM is the maximal LV wall thickness of 15 mm in end-diastole. Cardiac MRI has become instrumental not only in the diagnosis of HCM but also in the risk stratification of sudden cardiac death in patients with HCM [6].

There is a number of HCM subtypes, including basal asymmetric septal HCM (the most frequent), reverse curvature septal HCM, apical HCM, concentric HCM, midventricular HCM, non-contiguous HCM and mass-like HCM [5, 7]. Mass-like hypertrophic cardiomyopathy (HCM) is a very rare subtype of HCM defined as focal hypertrophy mimicking a cardiac mass [7]. Cardiac MRI is an important tool to differentiate HCM from neoplastic masses. In this case, cardiac MRI confirmed the presence of asymmetric thickening of the LV mid to apical lateral myocardial wall. The tissue characterization sequences (T1, T1 fat sat and T2 weighted imaging) demonstrated similar signal intensity as the background myocardium. This also applied to the first-pass perfusion imaging, that showed similar perfusion as the adjacent myocardium. On LGE imaging, there was intermediate signal intensity LGE in keeping with non-ischemic scar, similar to the pattern seen in HCM. Another imaging feature that helped differentiate mass-like HCM from a cardiac mass was the presence of myocardial contraction, which is present in mass-like HCM but not present in cardiac masses.

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