Hypertrophic cardiomyopathy (HC) with left ventricular (LV) apical aneurysm is a relatively new subgroup of patients within the broad disease spectrum, best identified and defined by contrast cardiovascular magnetic resonance (CMR). We agree with and appreciate Drs. Claver, Salazar-Mendiguchia, and Cequier’s observations and concerns regarding embolization in HC and LV apical aneurysm. The clinical question raised here concerns the frequency and nature of clot formation in the LV apex of these patients and the unpredictability of clinical events. Identification of thrombi situated in the aneurysm in this patient subset is not uncommon (i.e., 20%), and 5% of patients may experience an embolic event. As suggested by our report, clot size may be variable and include small thrombi (not always reliably identified by echocardiography) that are nevertheless capable of embolizing.

It is apparent that CMR is the most effective imaging test to identify apical thrombi independent of size, and it is our practice to routinely use CMR for surveillance in this patient subgroup. However, a limitation to this strategy is that many patients with apical aneurysm will receive primary prevention implantable cardioverter-defibrillators and consequently are no longer eligible for CMR studies. In this circumstance, we may interrogate the apex of the LV using oblique (off-axis) echocardiographic imaging planes, often with the use of contrast, to improve the detection of thrombus over standard echocardiography. If clinical concern for thrombus formation remains, we may selectively evaluate patients with computed tomographic angiography.

Certainly, any patient with HC with a visible apical thrombus deserves strong consideration for anticoagulation. Whether anticoagulant drugs should be routine in patients with HC and apical aneurysm is an open question, requiring more data for resolution, and therefore presently, those decisions can only be made on a case-by-case basis.