Patients with HCM who cannot be helped by drug therapy may participate in the study. The standard treatment for such patients is septal myectomy, an operation in which the surgeon shaves the muscle obstructing the blood flow. Another treatment option is implantation of a type of pacemaker that causes the heart to contract in a certain way that reduces blood flow obstruction and improves symptoms. The pacemaker is implanted under local anesthesia and usually takes less than an hour. PTSA is an experimental treatment that may provide a third option. In PTSA, a thin tube (catheter) is inserted into the blood vessel that feeds the heart muscle causing the blood flow obstruction. A small amount of alcohol is injected through the catheter to destroy some of the muscle and relieve the obstruction.