Diagnosis of apical hypertrophic cardiomyopathy: T-wave inversion and relative but not absolute apical left ventricular hypertrophy

Abstract

Background: Diagnosis of apical HCM utilizes conventional wall thickness criteria. The normal left ventricular wall thins towards the apex such that normal values are lower in the apical versus the basal segments. The impact of this on the diagnosis of apical hypertrophic cardiomyopathy has not been evaluated.

Methods: We performed a retrospective review of 2662 consecutive CMR referrals, of which 75 patients were identified in whom there was abnormal T-wave inversion on ECG and a clinical suspicion of hypertrophic cardiomyopathy. These were retrospectively analyzed for imaging features consistent with cardiomyopathy, specifically: relative apical hypertrophy, left atrial dilatation, scar, apical cavity obliteration or apical aneurysm. For comparison, the same evaluation was performed in 60 healthy volunteers and 50 hypertensive patients.

Results: Of the 75 patients, 48 met conventional HCM diagnostic criteria and went on to act as another comparator group. Twenty-seven did not meet criteria for HCM and of these 5 had no relative apical hypertrophy and were not analyzed further. The remaining 22 patients had relative apical thickening with an apical:basal wall thickness ratio >1 and a higher prevalence of features consistent with a cardiomyopathy than in the control groups with 54% having 2 or more of the 4 features. No individual in the healthy volunteer group had more than one feature and no hypertension patient had more than 2.

Conclusion: A cohort of individuals exist with T wave inversion, relative apical hypertrophy and additional imaging features of HCM suggesting an apical HCM phenotype not captured by existing diagnostic criteria.

Keywords: Cardiovascular magnetic resonance; Hypertrophic cardiomyopathy.

Fig. 1

a, Case in point 1 (see online supplementary cine images). An athletic 49 year old man with no family history and normal coronary arteries was referred with atypical chest pain, an abnormal ECG (deep infero-lateral TWI, a) and a normal echocardiogram for CMR. This demonstrated: 1) a discrete increase in wall thickness at the apex (10 mm vs 8 mm basally); 2) a 14 mm tube-like apical cavity (arrowed, b, c) which obliterates in systole; 3) a small apical micro-aneurysm un-obliterated in systole (arrowed, f); 4) apical scar (arrows d, g). 5) Left atrial dilatation (e). This patient was subsequently found to have a gene mutation in myosin binding protein C3 (R810H). b, Case in point 2. Despite the different appearances between the left and right images; all images are in diastole (SSFP cine stills). Top row 4 chamber, bottom row 2 chamber. Left: Index scan 2008 of 47 year old male referred with TWI and atypical chest pain which was related to gall stone disease. Maximum wall thickness in 2008 was 12 mm with apical cavity obliteration of 25 mm. At follow-up 6 years later, the maximum wall thickness was 18 mm with apical cavity obliteration of 41 mm. He now has a formal diagnosis of HCM.

Fig. 2

Measuring apical wall thickness. Left: short axis slice near the base of the heart with max wall thickness of 8 mm. Middle: four chamber view. The left ventricle is divided into thirds: Basal, mid and apical, the apical cap makes up only the most apical 6% of the ventricle. At the base the short axis slice is truly perpendicular to the wall. Towards the distal ventricle — as the cavity tapers, the short axis slice is not perpendicular to the wall — this complicates wall thickness measurement and it should be performed on multiple long axis views, perpendicular to the true septal axis and with careful exclusion of papillary muscle origins and trabeculation.

Fig. 3

Graph showing number of abnormal criteria fulfilled by disease type. This illustrates that there are many patients in the relative apical hypertrophy group who are much more akin to true HCM than to normal but there is considerable overlap.

Fig. 4

a) Left ventricular apical wall thickness across the groups. In healthy volunteers and hypertension, the apex is a thin structure (mean ± SD = 5 ± 1 and 6 ± 2). In the patients with TWI, the apex is significantly thicker (15 ± 4, p < 0.001 ANOVA). b) In healthy volunteers and hypertension wall thickness universally tapers towards the apex and thus the apex:base wall thickness ratio is always less than 0.9 (mean ± SD apex:base ratio = 0.6 ± 0.1 and 0.5 ± 0.1) unlike the disease candidate group (1.2 ± 0.3, p < 0.001).

Fig. 5

Patient flow diagram and table.