The goals of management in patients with HCM are to improve symptoms, prevent complications, and reduce the risk of sudden death. The three manifestations of HCM that are amenable to specific medical or surgical therapy are: (1) ventricular outflow obstruction (2) impaired ventricular relaxation during diastole, and (3) atrial and ventricular arrhythmias.
In patients with HCM, what are the optimal therapies for relieving outflow obstruction and improving LV relaxation?
Optimal therapy for the various manifestations of HCM has been debated for years. Outflow obstruction may be improved with beta-adrenergic blocking agents, calcium antagonists, and disopyramide. Pacemaker implant and, rarely, ventriculomyectomy or mitral valve replacement may be indicated. Patients who do not respond to maximum medical and surgical therapy may be candidates for cardiac transplantation.
Calcium antagonists (i.e., verapamil) and beta-adrenergic blocking agents may improve ventricular relaxation. Resting obstruction may be lessened or abolished with disopyramide, thereby improving relaxation. Calcium antagonists should be used with caution because they may worsen or provoke outflow obstruction in some patients.
Name three ways to enhance the outflow gradient in HCM.
Increase contractility (with inotropic drugs such as digitalis)
Decrease preload (hypovolemia, diuretics, nitrates)
Decrease afterload (nitrates, vasodilators)
What is the natural history of HCM?
The clinical course of patients with HCM is variable. Many patients remain asymptomatic or only mildly symptomatic for years. In those with resting obstruction, approximately two-thirds progress to New York Heart Association Class III‚ IV over a 4-year period. The degree of ventricular hypertrophy usually remains stable over time but may increase. In about 10% of patients, HCM progresses to LV dilatation and a dilated cardiomyopathy. The onset of atrial fibrillation usually results in worsening of symptoms. Mortality tends to be higher in those with outflow obstruction, who also tend to have the most extensive hypertrophy and the highest incidence of atrial and ventricular arrhythmias. The annual mortality of patients with HCM is about 3% in adults and 6% in children.