BackgroundPrevious data suggest that mitral valve leaflets are elongated in hypertrophic cardiomyopathy (HCM), and mitral valve leaflet elongation may constitute a primary phenotypic expression of HCM. Our objective was to measure the length of mitral valve leaflets by cardiovascular magnetic resonance (CMR) in subjects with HCM caused by a Finnish founder mutation in the myosin-binding protein C gene (MYBPC3-Q1061X), carriers of the same mutation without left ventricular hypertrophy, as well as in unselected consecutive patients with HCM, and respective controls.MethodsAnterior mitral valve leaflet (AML) and posterior mitral valve leaflet (PML) lengths were measured by CMR in 47 subjects with the Q1061X mutation in the gene encoding MYBPC3 and in 20 healthy relatives without the mutation. In addition, mitral valve leaflet lengths were measured by CMR in 80 consecutive non-genotyped patients with HCM in CMR and 71 age- and gender-matched healthy subjects.ResultsOf the subjects with the MYBPC-Q1016X mutation, 32 had left ventricular hypertrophy (LVH, LV maximal wall thickness ≥ 13 mm in CMR) and 15 had no hypertrophy. PML was longer in patients with the MYBPC3-Q1061X mutation and LVH than in controls of the MYBPC group (12.8 ± 2.8 vs 10.6 ± 1.9 mm, P = 0.013), but the difference between the groups was not statistically significant when PML was indexed for BSA (P = 0.066), or when PML length was adjusted for BSA, age, gender, LV mass and ejection fraction (P = 0.195). There was no significant difference in the PML length in mutation carriers without LVH and controls (11.1 ± 3.4 vs 10.6 ± 1.9, P = 0.52). We found no difference in AML lengths between the MYBPC mutation carriers with or without hypertrophy and controls. In 80 consecutive non-genotyped patients with HCM, there was no difference either in AML or PML lengths in subjects with HCM compared to respective control subjects.ConclusionsIn subjects with HCM caused by the Q1061X mutation in the MYBPC3 gene, the posterior mitral valve leaflets may be elongated, but mitral valve elongation does not constitute primary phenotypic expression of the disease. Instead, elongated mitral valve leaflets seem to be associated with body size and left ventricular remodeling.
Increased mechanical dispersion was associated with NSVT in HCM patients on 24-h ambulatory ECG monitoring. Key messages The prediction of sudden cardiac death in hypertrophic cardiomyopathy remains a challenge and novel imaging methods are required to identify individuals at risk of malignant ventricular arrhythmias. Mechanical dispersion by speckle tracking echocardiography is associated with NSVT on 24-h ambulatory ECG monitoring in patients with hypertrophic cardiomyopathy.
Dynamics of ventricular repolarization in HCM are affected by hypertrophy and fibrosis. LGE may confer an independent effect on QT dynamics which may increase the arrhythmogenic potential in HCM.
Objectives: The sensitivity and specificity of the conventional 12-lead ECG to identify carriers of hypertrophic cardiomyopathy (HCM)causing mutations without left ventricular hypertrophy (LVH) has been limited. We assessed the ability of novel electrocardiographic parameters to improve the detection of HCM mutation carriers. Methods: We studied 140 carriers (G+) of the TPM1-Asp175Asn or MYBPC3-Gln1061X pathogenic variants for HCM: The G+/LVH+ group (n = 98) consisted of mutation carriers with LVH and the G+/LVH− group (n = 42) without LVH. The control group consisted of 30 subjects. The standard 12-lead ECG was comprehensively analyzed and two novel ECG variables were introduced: RV1bRV2NRV3 and septal remodeling. A subset of 65 individuals underwent cardiac magnetic resonance imaging and 2D strain echocardiography. Results: Conventional major ECG criteria were sensitive (90%) and specific (97%) in identifying G+/LVH+ subjects. RV1bRV2NRV3 and septal remodeling were more prevalent in the G+/LVH− subjects compared to the control group (33% vs 3%, p = 0.005 and 45% vs 3%, p b 0.001, respectively). The combination of RV1bRV2NRV3 and Q waves and repolarization abnormalities (QR) differentiated between the G+/LVH− subjects and the control group with a sensitivity of 52% and specificity of 97%. The combination of septal remodeling and QR differentiated between G+/LVH− subjects and the control group with a sensitivity of 64% and specificity of 97%. Conclusions: The novel ECG-parameters RV1bRV2NRV3 and septal remodeling were effective in identifying G+/ LVH− subjects and could be useful in the diagnostics of new suspected HCM patients and in the screening and follow-up of HCM families.
This manuscript has not been published before and is not currently being considered for publication elsewhere. Increased septal convexity of left ventricle has been described in subjects with hypertrophic cardiomyopathy (HCM) -causing mutations without left ventricular hypertrophy (LVH). Our objective was to study septal convexity by cardiac magnetic resonance (CMR) in subjects with the Finnish founder mutation Q1016X in the myosin-binding protein C gene ( MYBPC3) . Septal convexity was measured in end-diastolic 4-chamber CMR image in 67 study subjects (47 subjects with the MYBPC3 -Q1061X mutation and 20 healthy relatives without the mutation). Septal convexity was significantly increased in subjects with the MYBPC3 -Q1061X mutation and LVH (n = 32) compared to controls (11.4 ± 4.3 vs 2.7 ± 3.2 mm, P < 0.001). In mutation carriers without LVH, there was a trend for increased septal convexity compared to controls (4.9 ± 2.5 vs 2.7 ± 3.2 mm, P = 0.074). When indexed for BSA, septal convexity in mutation carriers without LVH was 2.8 ± 1.4 mm/m 2 and 1.5 ± 1.6 mm/m 2 in controls ( P = 0.036). In all mutation carriers, septal convexity correlated significantly with body surface area, age, maximal LV wall thickness, LV mass, and late gadolinium enhancement. Subjects with the MYBPC3 –Q10961X mutation have increased septal convexity irrespective of the presence of LVH. Septal convexity appears to reflect septal remodeling, and could be useful in recognizing LVH negative mutation carriers.
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