Distinguishing ventricular septal bulge versus hypertrophic cardiomyopathy in the elderly

Abstract

The burgeoning evidence of patients diagnosed with sigmoidal hypertrophic cardiomyopathy (HCM) later in life has revived the quest for distinctive features that may help discriminate it from more benign forms of isolated septal hypertrophy often labelled ventricular septal bulge (VSB). HCM is diagnosed less frequently than VSB at older ages, with a reversed female predominance. Most patients diagnosed with HCM at older ages suffer from hypertension, similar to those with VSB. A positive family history of HCM and/or sudden cardiac death and the presence of exertional symptoms usually support HCM, though they are less likely in older patients with HCM, and poorly investigated in individuals with VSB. A more severe hypertrophy and the presence of left ventricular outflow obstruction are considered diagnostic of HCM, though stress echocardiography has not been consistently used in VSB. Mitral annulus calcification is very prevalent in both conditions, whereas a restrictive filling pattern is found in a minority of older patients with HCM. Genetic testing has low applicability in this differential diagnosis at the current time, given that a causative mutation is found in less than 10% of elderly patients with suspected HCM. Emerging imaging modalities that allow non-invasive detection of myocardial fibrosis and disarray may help, but have not been fully investigated. Nonetheless, there remains a considerable morphological overlap between the two conditions. Comprehensive studies, particularly imaging based, are warranted to offer a more evidence-based approach to elderly patients with focal septal thickening.

Figure 1

Representative image illustrating measurement of isolated basal septal hypertrophy. Two-dimensional echocardiographic parasternal long-axis view from a 71-year-old male who met all the criteria for ventricular septal bulge (A). The maximal thickness of the proximal septum (measured within the first third of the septal length, usually within 20 mm from the insertion of the right aortic cusp) was 17 mm, which was approximately twice the thickness of the mid septum (usually measured at the second third of the septal length), measuring 8 mm. Note that the very proximal fibrous part of the septum should be discarded (B, dashed line). From the same parasternal view, the thickness of the posterior wall is usually measured, which could help in the differential diagnosis between ventricular septal bulge and hypertrophic cardiomyopathy (see the text and figure 3 for details, and the corresponding movie in the online supplementary data).

Figure 2

Patterns of left ventricular hypertrophy observed in patients with hypertrophic cardiomyopathy (HCM). The figure shows the most common septal morphologies in HCM. The table under the figure indicates estimates of the overall prevalence, the age at onset and the yield of genetic testing for each pattern. Modified from Bos et al, Binder et al and Lever et al.

Figure 3

Main echocardiographic features that could help in distinguishing between HCM and VSB in elderly patients. Ao, aorta; HCM, hypertrophic cardiomyopathy; IVS, interventricular septum; LA, left atrium; LV, left ventricle; LVOTPG, left ventricular outflow track pressure gradients; PW, posterior wall; SAM, systolic anterior movement of the mitral valve; VSB, ventricular septal bulge.

Figure 4

Differential diagnostic algorithm of elderly individuals with an isolated proximal septal hypertrophy. An individual enters the differential diagnostic algorithm only if both the ‘entry criteria’ are met; subsequently, a diagnosis of HCM or VSB is established only if all (or most of) the ‘principal criteria’ are present or absent, respectively. In uncertain ‘grey’ cases, in which some principal criteria are present but other are absent, and a definitive diagnosis is sought, ‘further criteria’ involving CMR, genetic testing and endomyocardial biopsy may be considered. CMR, cardiovascular MR; HCM, hypertrophic cardiomyopathy; IVS, interventricular septum; LVOT, left ventricular outflow tract; PW, posterior wall; SAM, systolic anterior movement of the mitral valve; SCD, sudden cardiac death; VSB, ventricular septal bulge.