Muscular Subaortic Stenosis

Abstract

Eleven patients with muscular subaortic stenosis were studied by use of combined right and transatrial septal left heart catheterization. A variety of stimulating maneuvers were performed to induce or increase the functional outflow tract obstruction; 150 pug/kg of propranolol was administered intravenously, and the stimulating maneuvers were repeated. Outflow obstruction was latent (present only with stimulation) in four patients, labile (present intermittently at rest) in five patients, and persistent and severe in two patients. Propranolol abolished or significantly decreased the spontaneous variations in outflow obstruction occurring at rest, during the enhanced gradient in the post-exercise state, and during variations induced by isoproterenol infusion. The outflow obstruction induced by inhalation of amyl nitrite, the Valsalva maneuver, and premature ventricular contractions was only inconsistently prevented. Long-term oral propranolol therapy has been of significant symptomatic benefit in all the patients with latent or labile outflow obstruction and is considered the treatment of choice in these groups. In one patient with persistent outflow obstruction, an increase in symptoms occurred when oral propranolol was administered, and the drug was discontinued. Evidence is presented to support the concept of a cycle of obstruction and hypertrophy in the natural history of this disease. This vicious cycle might be prevented by propranolol. Additional Indexing Words: Amyl nitrite Isoproterenol

Hypertrophic Cardiomyopathy

“…They are effective in the relief of ischemic chest discomfort and may attenuate exercise-induced LVOT obstruction and resulting dyspnea as well 230 . Disopyramide, a negative inotropic agent, when added to a beta blocker may reduce symptoms further in patients with LVOT obstruction 231 .…”

Diagnosis and Treatment of Obstructive Hypertrophic Cardiomyopathy

“…Furthermore, b-blockers are used in HCM to control the arrhythmic burden in patients with frequent supraventricular or ventricular ectopies, and for rate control in patients with atrial fibrillation. Propranolol was the first b-blocker used and in old studies showed a significant benefit for symptoms associated with a significant reduction in LVOTO [23][24][25][26][27]. More selective beta blockers such as nadolol and bisoprolol are equally effective in controlling exercise induced LVOTO [28].…”

Inherited cardiomyopathies

“…Gene specific treatment has yet to enter clinical practice but is likely to play a role in the future. β blockers are recommended as first line therapy in HCM with symptomatic left ventricular outflow tract obstruction 35565758. ESC guidelines recommend titration to maximum dose and use of disopyramide or invasive and surgical options if symptom control remains problematic 35…”