Left Ventricular Noncompaction and Hypertrophic Cardiomyopathy
Patient KM is a 26-year-old male in whom a systolic ejection murmur was recently identified on a routine physical examination. As part of his evaluation, he underwent 2-dimensional echocardiography, which revealed asymmetrical left ventricular (LV) hypertrophy with a maximum LV wall thickness of 22 mm in the basal anterior septum and extension of hypertrophy into the posterior septum. His LV ejection fraction was 55%, with a normal cavity size and no evidence of resting LV outflow tract obstruction. In addition, the myocardium was noted to be highly trabeculated from the apex to the midportion of the LV (Figure 1; online-only Data Supplement Movie I). The right ventricle was normal in size and function. He has never developed heart failure symptoms, chest pain, or syncope and has no known family history of heart disease or sudden cardiac death.
Cine and contrast-enhanced cardiovascular magnetic resonance (CMR) imaging was performed to better characterize the cardiac morphology in this patient. CMR confirmed the presence of asymmetrical LV hypertrophy in the basal anterior septum, with prominent trabeculations (ie, noncompacted myocardium) noted in the apex and LV lateral wall (Figure 2; online-only Data Supplement Movie II). The maximum end-diastolic ratio of noncompacted to compacted myocardial wall thickness was 4:1, consistent with a diagnosis of LV noncompaction. In addition, contrast-enhanced CMR demonstrated multiple areas of delayed enhancement that predominantly involved the basal anterior septum, consistent with myocardial fibrosis (Figure 2).
Hypertrophic cardiomyopathy is the most common genetic heart disease, with a prevalence of 1:500. It is diagnosed when LV hypertrophy occurs in the absence of another identifiable cause (such as hypertension or valve disease) on either an echocardiogram or CMR and is associated with a heterogeneous phenotypic expression and clinical course, including sudden cardiac death and heart failure symptoms.1 It is inherited as a mendelian autosomal dominant trait, and >900 associated mutations from 11 sarcomeric genes have been identified.2
LV noncompaction is a rare disorder, with a prevalence of less than 1:5000, and little is known about its inheritance pattern. LV noncompaction is diagnosed by the presence of excessive trabeculations of the LV (with a noncompacted-to-compacted ratio at end diastole of ≥2:1), which are caused by a disruption in myocardial development. Although the natural history of LV noncompaction remains uncertain, patients may be at increased risk of thromboembolic events and sudden cardiac death. Recently, mutations in genes encoding sarcomeric proteins, which previously have been implicated in the pathogenesis of hypertrophic cardiomyopathy, have been identified in patients with LV noncompaction but without LV hypertrophy.3 This suggests that these cardiomyopathies may have a similar genetic origin, and as this case demonstrates, the phenotypic expression of both diseases can occur in the same patient.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/CIRCULATIONAHA.108.829564/DC1.