All are true about Hyperophic Obstructive Cardiomyopathy, except :

Answer is A (b agonists are useful) Hyperophic obstructive cardiomyopathy is characterized by hyperophy of left ventricle in the absence of an obvious cause such as hypeension or aoic stenosis. Distinctive Pathophvsiological features include: Heterogeneous hyperophy of LV Pattern of hyperophy is distinctive Asymmetrical septa! hyperophy is characteristic mainly affecting the IV septum and anterolateral wall Thickness of ventricular septum is dispropoionately increased when compared with the free wall Dynamic LV outflow obstruction The LV outflow obstruction is dynamic i.e. it is related to narrowing of the subaoic area as a consequence of opposition of anterior mitral valve leaflet against the hyperophied septum in midsystole. The concept is termed systolic anterior motion (SAM) of mitral valve. The obstruction in HOCM is dynamic and is caused by the opposition of mitral valve leaflet against the hyperophied septum during systole. Increase in volume of blood in LV will move the muscular obstruction away from the opposite wall and decrease the obstructing agent as well as the intensity of murmur. Passive leg raising augments venous return, increases the volume of blood in LV, decreases the obstruction and hence decreases the murmur. Increase in myocardial contractility worsens the obstruction by moving the opposing walls closer to each other. 13 agonists (increase myocardial contractility) would thus increase the obstruction and should not be used. 13 blockers on the other hand are the agent of choice as these decrease myocardial contractility and hence relieve the obstruction by moving the opposing walls away from each other. Remember Clinical Features: Most common complaint in symptomatic patient -- Dyspnoea.Q Sudden Death Q may be the first manifestation. The Hallmark of HOCM is a systolic murmur Qmost often due to MR.Q Double - Triple Apical impulse may be seen.Q Diagnosis: The mainstay of diagnosis is EchocardiographyQ which demonstrates : Asymmetrical LV hyperophy.Q Systolic anterior motion of mitral valve.Q Treatment: b blockers should be the initial drugQ in symptomatic individuals. Ca++ channel blockers may be given.Q Avoid Q : -DigitalisQ - Diuretics Q - NitratesQ - b agonistsQ