Genetic Disorder due to Mutations - Biology Assignment Help

1)  It is a genetic disorder due to mutations in the gene that encodes for β-Cardiac myosin heavy chain (Localised to chromosome 14). It is characterized by inappropriate and often massive myocardial hypertrophy There is myocardial disarray and interstitial fibrosis. It has asymmetric septal hypertrophy, left ventricular outflow obstruction due to systolic anterior motion of mitral valve, LV diastolic dysfunction, myocardial ischaemia and arrhythmias. LV outflow obstruction occurs only in about ¼th. 

2)  Usually the  apex is palpable and  will be LV type and may have double apical impulse due to powerful LA contraction. Prominent S4 and systolic murmur at lower sternal border are heard. The murmur is due to labile LV outflow obstruction and it increases with Valsalva manoeuvere, standing up from squatting position, exercise and in postextrasystolic contraction. The SM is harsh and crescendo-decrescendo in configuration. It commences sometime after S1 and is best heard between apex and left sternal border. It radiates to lower sternal border, axilla and base of the heart, but never to carotids. MR murmur may also be present. Brisk carotid pulse and sometimes prominent ‘a’ in JVP are seen.

3)  The abnormalities are seen in QRS, ST Changes and T-Waves. LV voltage is increased. Abnormal Q are seen in 25-50 per cent of patients, usually in inferolateral leads and may mimic myocardial infarction. Early repolarisation and other ST changes may be seen. Giant negative T-waves are seen in apical cardiomyopathy. LA is enlarged, Arrhythmias (NSVT 25 per cent, PSVT 35-50 per cent, af 5 per cent) are seen. In 5 per cent WPW may be seen.

4)  It is the most important diagnostic tool. There is asymmetric septal hypertrophy as seen by septal to posterior wall thickness ratio of 1.5 or more. Maximal septal hypertrophy occurs midway between apex and base. Apical hypertrophy, midventricular hypertrophy or RV hypertrophy may be seen. LV thickness can vary from 15mm to 60 mm. Systolic anterior motion of the mitral valve identifies LV outflow tract obstruction. There is also elongation and enlargement of mitral valve leaflets, leading to abnormal aortic outflow geometry. It contributes to pressure gradient across LV outflow and is also responsible for mitral regurgitation. There are other echocardiographic findings viz. small LV cavity, partial systolic closure and coarse fluttering of aortic valve reduced septal and exaggerated posterior wall motion.

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