Prominent Crypt Formation in the Inferoseptum of a Hypertrophic Cardiomyopathy Mutation Carrier Mimics Noncompaction Cardiomyopathy
Recently, we reported that crypts can be identified in the inferior part of the septum by cardiac magnetic resonance (CMR) imaging in most carriers of hypertrophic cardiomyopathy mutations (HCM) who have not yet developed hypertrophy.1 The crypts may be an early sign of maladaptive myocardial alterations that ultimately lead to the development of the characteristic hypertrophy in HCM patients.
In this patient, a 30-year-old asymptomatic female HCM carrier with a maximal septal wall thickness of 6 mm, the crypts were very prominent in the inferoseptum (Figure 1) and consequently were visible with echocardiography (Figure 2A and 2B). On both the CMR and echocardiographic images, the crypts were identified within the basal inferoseptum (Figure 2A and 2B and Movies I and II); flow in the crypts also was observed (Figure 2C and Movie III). No contrast enhancement was visible within the myocardium on delayed contrast-enhanced CMR images.
When crypt formation is very prominent in an HCM carrier, as in this patient, the cardiac image mimics the image of noncompaction cardiomyopathy on echocardiography.2 However, crypt formation as part of the development of HCM can be distinguished from noncompaction cardiomyopathy on the basis of several criteria, First, noncompaction generally is located in the apical and/or lateral segments of the left ventricle and very rarely in the basal inferoseptum. Second, the crypts penetrate compact myocardium sometimes up to the epicardial myocardial layer, in contrast to noncompaction cardiomyopathy, in which a noncompacted layer of myocardium parallels a compact layer alongside the ventricular cavity. Third, the crypt formation does not seem to affect global left ventricular contractile function, whereas in noncompaction cardiomyopathy, patients may have a dilated and poorly contracting left ventricle.3
Distinguishing between these 2 cardiomyopathies has important clinical therapeutic implications because HCM carriers may remain asymptomatic for decades and patients with noncompaction cardiomyopathy are at increased risk of thromboembolic events and supraventricular arrhythmias when heart failure is present.3 However, the very recent discovery of the crypts in HCM carriers probably means that HCM carriers have been misdiagnosed in the past as having some form of noncompaction cardiomyopathy.
In conclusion, if crypts are very prominent in HCM carriers, they also can be observed with echocardiography on a dedicated apical 2-chamber view through the inferoseptum but must be carefully distinguished from noncompaction cardiomyopathy.
We gratefully acknowledge Milan van Tuin for acquiring the CMR images and Yolanda de Groot for making the echocardiography images.
Sources of Funding
Dr Germans (grant 2006B213), Dr Wilde (grant 2003T302), and Dr van Rossum (2006B213) have received research grants from the Netherlands Heart Foundation.
The online-only Data Supplement, consisting of Movies I-III, is available with this article at http://circ.ahajournals.org/cgi/content/full/115/24/e610/DC1.
Germans T, Wilde AA, Dijkmans PA, Chai W, Kamp O, Pinto YM, van Rossum AC. Structural abnormalities of the inferoseptal left ventricular wall detected by cardiac magnetic resonance imaging in carriers of hypertrophic cardiomyopathy mutations. J Am Coll Cardiol. 2006; 48: 2518–2523.
Jenni R, Oechslin E, Schneider J, Jost CA, Kaufmann PA. Echocardiographic and pathoanatomical characteristics of isolated left ventricular non-compaction: a step towards classification as a distinct cardiomyopathy. Heart. 2001; 86: 666–671.