Hypertrophic cardiomyopathy with midventricular obstruction and apical aneurysm formation in a single family: case report

Background Hypertrophic cardiomyopathy (HCM) is an extremely heterogeneous disease. An under recognized and very often missed subgroup within this broad spectrum concerns patients with left ventricular (LV) apical aneurysms in the absence of coronary artery disease. Case presentation We describe a case of HCM with midventricular obstruction and apical aneurysm formation in 3 patients coming from a single family. This HCM pattern was detected by 2D-echocardiography and confirmed by cardiac magnetic resonance imaging. A cardioverter defibrillator was implanted in one of the patients because of non-sustained ventricular tachycardia detected in 24-h Holter monitoring and an abrupt drop in systolic blood pressure during maximal exercise test. The defibrillator activated 8 months after implantation by suppression of a ventricular tachycardia providing anti-tachycardia pacing. The patient died due to refractory heart failure 2 years after initial evaluation. The rest of the patients are stable after a 2.5-y follow-up period. Conclusion The detection of apical aneurysm by echocardiography in HCM patients may be complicated. Ventricular tachycardia arising from the scarred aneurysm wall may often occur predisposing to sudden death.


Background
Hypertrophic cardiomyopathy (HCM) is an extremely heterogeneous disease, in terms of clinical course and phenotypic expression [1][2][3]. An under recognized and very often missed subgroup within this broad spectrum concerns patients with left ventricular (LV) apical aneurysms in the absence of coronary artery disease [4][5][6][7][8][9][10]. In this report we present a case-series of HCM patients with midventricular obstruction and apical aneurysm formation in a single family.

Case presentation
We studied 3 female patients (case-index 1, 63-y; case-index 2, 56-y; case-index 3, 27-y) ( Figure 1) with already diagnosed HCM who were referred to our department for further evaluation. NYHA class was graded as III in the case-index 1 and as II in the case-index 2 and 3 patients. The patients underwent electrocardiography, echocardiography, 24-h Holter monitoring, treadmill cardiopulmonary exercise test, and cardiac magnetic resonance imaging. Unfortunatelly, genotype analysis was not performed since it is not, at present, available in our laboratory. Coronary arteriography performed in case-index 1 and case-index 2 patients excluded significant atherosclerotic narrowing of the extramural coronary arteries. The distribution of LV hypertrophy assessed by 2-D echo was similar among patients, with predominant thickening in the midseptal and midlateral regions (maximum wall thickness 16-18 mm) ( Figure 2, Additional File 1). None of the patients showed LV outflow tract obstruction. A formation of a wall-thinning aneurysm involving the LV apex was detected in all 3 patients, a finding also confirmed by means of cardiac magnetic resonance imaging (MRI) and by cardiac catheterization (Figures 3, 4 and Additionals file 2, 3). A cardioverter defibrillator was implanted in index-case 1 patient because of non-sustained ventricular tachycardia detected in 24-h Holter monitoring and an abrupt drop in systolic blood pressure during maximal exercise test. The defibrillator activated 8 months after implantation by suppression of a ventricular tachycardia providing anti-tachycardia pacing. The patient died due to refractory heart failure 2 years after initial evaluation. The rest of the patients are stable after a 2.5-y follow-up period.

Discussion
In this report we present a case of HCM with midventricular obstruction and apical aneurysm formation in 3 patients coming from a single family.
Isolated midventricular obstruction is an uncommon phenotype of HCM [7,11]. The midcavity obstruction is due to the midsystolic muscular apposition of the septum and LV free wall producing distinct proximal and distal chambers, resembling an "hourglass" shape of LV. Maron MS et al reported that the formation of LV apex aneurysm in HCM accounts approximately for 2% of HCM population. The pattern of hypertrophy in such patients is that of midventricular obstruction in 68%, and that of apical hypertrophy in 32% of patients [5]. Unfortunatelly, geno- type analysis was not performed in our patients since it is not available in our laboratory. However, this disorder has been associated with mutations of the essential or regulatory light chains of myosin. These types of mutation are assumed to cause stretch activation response disrupt leading to midventricular obstruction [12].

Family tree
The detection of apical aneurysms by echocardiography in HCM patients may be complex, if hypertrophy is confined to posterior septum, LV free wall, or to the apex. Furthermore, echocardiographist's experience, the quality of acoustic window and acquired images along with aneurysm's size play an important role in the aneurysm identification. According to a previous study, echocardiography identified only 57% of HCM patients having aneurysms, all of which were either medium or large [5]. On the contrary cardiac MRI, showing a greater spatial resolution, proves to be 100% sensitive in revealing this entity [5,13].
The mechanism responsible for the formation of apical aneurysms in HCM patients remains unresolved while several causes have been accused, such as increased LV wall stress as a result of midcavitary LV obstruction and elevated intracavitary systolic pressures, genetic predisposition and myocardial bridging of the left anterior descending coronary artery [5].
The formation of apical aneurysm in HCM represents a very serious clinical form of the disease. Very often, LV systolic function is depressed and thrombi may be developed inside the aneurysm leading to embolic events. Ventricular tachycardia arising from the scarred apical wall may also occur, predisposing to sudden death.

Conclusion
LV apical aneurysms affect up to 2% of the entire HCM population. Their detection using 2D echocardiography may be difficult. MRI imaging, on the contrary, shows 100% sensitivity in revealing them. The presentation of apical aneurysms in HCM patients is connected to serious complications including embolic events or even sudden death.

Consent
Written informed consent was obtained at first visit from all patients for publication of this case report and all accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.