Cardiology Associates of North Mississippi Now Performs Percutaneous Transluminal Septal Myocardial Ablation (PTSMA) by Alcohol-induced septal branch occlusion for Hypertrophic Obstructive Cardiomyopathy (HOCM)
02/18/2005.
CANM cardiologists recently performed the first alcohol ablation of the interventricular septum in the North Mississippi region, providing a new treatment option for symptomatic hypertrophic obstructive cardiomyopathy.
Hypertrophic cardiomyopathy (HOCM) is defined as the unexplained, asymmetical or concentric hypertrophy of the undilated left ventricle. It may be inherited as an autosomal dominant condition, but at least half of cases may be the result of sporadic mutation. Hypertrophic cardiomyopathy is the most common genetically transmitted cardiovascular disease. HOCM accounts for less than 5% of the overall heart failure population. Unlike dilated cardiomyopathy, HOCM is distinguished by a thickening and stiffening of the interventricular septum. A subset of this population involves obstruction of the left ventricular outflow tract.
The condition usually slowly progresses and symptoms can develop such as shortness of breath on exertion, dizziness, fainting and chest pain (all of which reflect the inability of the heart to pump enough blood around the body.) People with HOCM are at risk from sudden death because serious and potentially fatal arrhythmias, such as ventricular tachycardia and ventricular fibrillation, may occur.
Treatment Options
Whether or not patients are experiencing symptoms, it is important to avoid isometric exercises such as weight lifting. Unless otherwise advised by a physician, aerobic exercises such as walking or even running can be safe as long as they are never engaged to the point of dehydration and/or exhaustion.
Until recently, treatment options for HOCM patients were limited to medical management, dual chamber pacing, or surgical myectomy. Beta blockers and calcium channel blockers are the primary pharmacologic tool, with many patients demonstrating symptom improvement initially. However, a significant number either do not respond to drug therapy, or develop intolerance. In additional, dual chamber pacing has achieved some success in HOCM patients, though less than half have sustained long-term symptom relief.
Surgical myectomy, which involves debulking of the ventricular septum and enlargement of the left ventricular outflow tract, has demonstrated long-term symptom relief in many HOCM cases. However, as many patients are not surgical candidates either due to contraindications or preference, clinicians are now pursuing interventional treatment options.
New Interventional Therapy
Alcohol ablation of the interventricular septum is a catheter-based treatment that involves direct injection of ethyl alcohol into a targeted region of the septal wall. “Identification of an appropriate branch supplying the hypertrophied septal region is crucial to the success of this procedure,” says Barry Bertolet, M.D., the CANM interventional cardiologist who performed the recent procedure. Echocardiography with a doppler study of the outflow tract are the primary tools in the diagnostic work-up of these patients.
“The procedure result is a targeted septal myocardial infarct that decreases the obstruction in the outflow tract, and precipitates a remodeling process that gradually shrinks the septum and widens the tract,” says Dr. Bertolet. “Substantial symptom relief can often be seen in a matter of days,” he adds.
The accepted indication for percutaneous transluminal septal myocardial ablation (PTSMA) by alcohol-induced septal branch occlusion for hypertrophic obstructive cardiomyopathy (HOCM) in adult patients when ALL of the following criteria are met:
- Patient has severe symptoms (e.g., dyspnea, angina pectoris, [pre]syncope, palpitations or heart failure) for at least 6 months despite optimal drug therapy (e.g., beta-blockers, calcium-antagonists), dual chamber pacing (DDD) therapy and/or ineffective previous surgical myotomy/myectomy; AND
- Patient is classified as New York Heart Association class III or IV; AND
- Patient has a classical, asymmetric subaortic HOCM identified by echocardiography (ECHO), and not a mid-ventricular, a concealed membranous subaortic stenosis, nor supravalvular form; AND
- ECHO shows left ventricular wall thickness of > 13 mm in adults in the absence of another cause for left ventricular hypertrophy (LVH); 15 mm in an athlete; AND
- Patient has systolic anterior motion of the mitral valve on ECHO; AND
- Patient has a resting left ventricular outflow tract (LVOT) gradient of > 30 mmHg or a stressed gradient of > 60 mmHg, or patient has less severe symptoms and LVOT of > 50 mmHg at rest or > 100 mmHg under stress; AND
- Patient does not have coronary artery disease (CAD) that would preclude performance of the procedure.
The technique for the alcohol-induced septal infarction is as follows. The femoral artery and vein are cannulated using 6 Fr sheaths, respectively. A 6 Fr multipurpose catheter is inserted into the left ventricle and pressure measurements recorded. A 5 Fr balloon-tipped pacemaker is inserted through the right femoral vein to the right ventricle. An 6 Fr coronary guide catheter is then inserted through the femoral artery sheath.
Following positioning of the catheters, coronary arteri-ography identifies the septal artery branches from the proximal left anterior descending artery. Intravenous heparin is then administered.
Prior to septal ablation, narcotics are given. The first large septal artery is cannulated using an 0.014” angioplasty guidewire over which a short angioplasty balloon is completely advanced into the first septal artery. The septal artery balloon catheter is inflated and radiographic contrast is instilled into the occluding balloon to demonstrate the correct positioning of the balloon catheter without con-trast reflux.
Simultaneous two-dimensional transthoracic echocardiography is also per-formed. For contrast opacification of the hypertrophied septum, Optison or Definity echo contrast (3 cc) is diluted 1: 10 and instilled via the septal balloon lumen. The echo contrast opacifies the protruding septum and defines the area of proposed infarction. Following echocardiographic confirmation of correct septal branch occlusion, 1-3 cc of 98% dehydrated alcohol is delivered slowly into the septal artery over 5 min, followed by a 5-min waiting period.
Hemodynamics are continuously measured before, during, and after alcohol septal ablation. After the 5-min period following alcohol administration, the occlud-ing balloon catheter is deflated and withdrawn. Coronary arteriography is repeated to assure no compromise of the LAD. The 6 Fr multipurpose catheter is re-inserted into the LV cavity and pressure measures repeated. Success is achieved when the provoked gradient is less than 20 mm Hg.
The temporary pacemaker and the vascular sheaths are secured in place. The patient is transferred to the coronary care unit for observation. Patients are managed after the procedure (as are patients after spontaneous myocardial infarction) in a monitored setting for a minimum 3-day hospital stay. Temporary pacemakers are routinely left in place for up to 2 days. Peak creatine kinase often exceeds 1000 U/liter.
Conduction defects are common. Third degree AV block occurs during the procedure in 60%-70% of patients. Following the procedure, right bundle branch block (RBBB) is present in approximately one half of patients. A corollary is that patients with preexisting left bundle branch block (LBBB) usually require permanent pacing after ablation
Activity is restricted for 2-4 weeks after discharge. Patients return in 3 months for clinical assessment and a follow-up echocardiogram.