Cardiomyopathy outflow tract obstruction

Contraindications are hypertrophic obstructive cardiomyopathy (increase in inotropism can increase outflow tract obstruction), AF in WPW syndrome (can cause precipitation of the arrhythmia to ventricular fibrillation (VF) by preferential conduction over the accessory pathway), significant AV-block or sick sinus syndrome, hypokalemia (causes increased digoxin sensitivity and supraventricular/ventricular arrhythmia), thyreotoxicosis, postinfarction status (increased mortality). Caution should be exerted in renal failure, and coadministration of other drugs depressing sinus node or AV-nodal function. 

Maron MS, Olivotto I, Betocchi S, etal. Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy. N Engl J Med 2003 348 295-303. 

Cherian J, Kothari S, Angelis D, Atef A, Downey B, Kirkpatrick Jr. J. Atypical takotsubo cardiomyopathy dobutamine-precipitated apical ballooning with left ventricular outflow tract obstruction. Tex Heart Inst J 2008 35(1) 73-5. 

Hypertrophic cardiomyopathy a primary myocardial disorder of sacromeric proteins with an autosomal dominant pattern of inheritance is characterized by asymmetric hypertrophy of the septum with or without dynamic obstruction of the outflow tract (1,2), The prevalence in the general population is estimated as 1 500 and it is the most common monogenic cardiac disorder, Annual mortality in an unselected population is reported to be about I % to 2%, and sudden death is the most common cause, Sudden death is assumed to be due to idiopathic ventricular arrhythmias, but hemodynamic factors and myocardial ischemia may be involved as well. 

Ruzyllo W, Chojnowska L, Demkow M, et al. Left ventricular outflow tract gradient decrease with non-surgical myocardial reduction improves exercise capacity in patients with hypertrophic obstructive cardiomyopathy, Eur Heart J 2000 21 770-777. 

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