Patient Selection for Alcohol Septal Ablation for Hypertrophic Obstructive Cardiomyopathy: Clinical and Echocardiographic Evaluation
Total Page：16
File Type：pdf, Size：1020Kb
REVIEW Patient selection for alcohol septal ablation for hypertrophic obstructive cardiomyopathy: clinical and echocardiographic evaluation It has been 18 years since the first alcohol septal ablation was performed in London for relief of symptoms associated with left ventricular outflow tract obstruction in hypertrophic obstructive cardiomyopathy. In the interval since the introduction of this catheter-based alternative to surgical myectomy, use of this procedure has disseminated across the globe, and numerous reports have been published describing its efficacy and safety when performed at high-volume centers by skilled operators. Retrospective comparisons of alcohol septal ablation with surgical myectomy have not conclusively demonstrated superiority of either procedure. The current treatment approach relies on clinical judgment and patient preference. Optimal results of alcohol septal ablation depend on careful patient selection based on clinical and echocardiographic criteria. KEYWORDS: alcohol septal ablation n echocardiography n ethanol n hypertrophic Danita M Yoerger cardiomyopathy n hypertrophic obstructive cardiomyopathy n myocardial contrast Sanborn*1, echocardiography Ulrich Sigwart2 & Michael A Fifer1 Hypertrophic cardiomyopathy (HCM) is a Relief of obstruction can be achieved 1Massachusetts General Hospital, Yawkey 5B-5916, 55 Fruit Street, primary disease of heart muscle that results in surgically via septal myectomy or by a catheter- Boston, MA 02114–2696, USA idiopathic hypertrophy of the left ventricle in based technique, alcohol septal ablation (ASA) 2l’Université de Genève, 1, Avenue de Miremont, CH-1206 Geneva, the absence of abnormal loading conditions. [7]. Regardless of the technique employed Switzerland The disease has a genetic basis and is often to relieve obstruction, successful gradient *Author for correspondence: Tel.: +1 617 726 1543 inherited in an autosomal dominant fashion. reduction with resultant lowering of left Fax: +1 617 726 7684 The frequency of the disease is approximately ventricular (LV) systolic pressure is associated [email protected] one in 500 adults [1] . A variety of HCM with relief of lifestyle-limiting symptoms phenotypes exist, but the variant which has [8–11] . As experience with ASA grows, it has been the subject of the most interest and become clear that appropriate patient selection investigation is hypertrophic obstructive enhances procedural success and reduces cardiomyopathy (HOCM), associated with a complication rates. left ventricular outflow tract (LVOT) gradient. It has been estimated that approximately Clinical features of HOCM 25% of individuals with HCM have resting The symptoms of HOCM include dyspnea on obstruction [2–4]; more recent prospective exertion, angina, lightheadedness, presyncope data, however, suggest that up to 70% of and syncope. Factors contributing to dyspnea symptomatic HCM patients have obstruction on exertion include LVOT obstruction, with activity [5,6]. diastolic dysfunction due to hypertrophy and The cardinal features of HOCM include fibrosis, myocardial ischemia and MR [12] . asymmetric septal hypertrophy, systolic Angina, which is generally associated with anterior motion (SAM) of the mitral valve, effort and has the likelihood of occurring in the LVOT obstruction and mitral regurgitation absence of epicardial coronary artery disease, (MR). Treatment goals include relief of may represent myocardial ischemia due to a symptoms, prevention of sudden cardiac death demand/supply mismatch, since the metabolic and family screening and counseling. When needs of the hypertrophied myocardium cannot symptoms persist despite adequate conservative be met by the coronary microcirculation. The therapy, consideration of septal reduction occurrence of lightheadedness, presyncope therapy for relief of LVOT obstruction should and syncope may be due to a confluence of be considered. abnormalities including LVOT obstruction, part of 10.2217/ICA.12.24 © 2012 Future Medicine Ltd Interv. Cardiol. (2012) 4(3), 349–359 ISSN 1755 -5302 349 REVIEW Sanborn, Sigwart & Fifer / c s – + m systemic vasodilation, diastolic dysfunction and ventricular tachyarrhythmias. 0 200 400 600 E chocardiography in HOCM Echocardiography in HOCM usually reveals a triad of abnormalities: Beats nAsymmetric LV hypertrophy (ratio of inter- 99 ventricular septal [IVS] to posterior wall thickness ≥1.3); nSAM of the mitral valve; MS Every Max PG = mmHg 103.4 V = Max 508.5 cm/sec 0 nA dynamic, late-peaking LVOT gradient by Doppler. Delay 1 Delay Obstruction to LV outflow occurs due to 4 cm apposition of the thickened septum and the 7. : 0 anterior leaflet of the mitral valve; there is ante- 0 10 C rior displacement of the coaptation point of the Focus mitral leaflets due to hypertrophy and displace- ment of the papillary muscles. This in turn leads / c s 68 68 m 2.5 MHZ to residual anterior mitral leaflet length. The mitral leaflet tips move into the LVOT dur- ing systole (SAM) due to drag forces [13,14] and the Venturi effect [15] (FIGURE 1A). As the anterior mitral leaflet tip comes into contact with the IVS during the systolic ejection period, there 2D echocardiography 2D from the parasternal long axis showing view, marked LA is acceleration of blood flow in the LVOT and thus a late-peaking LVOT gradient detectable by spectral Doppler (FIGURE 1C). This obstruction is a dynamic process, and thus varies based on loading conditions and cycle length. Factors LV that increase contractility or decrease LV filling (exercise, Valsalva maneuver and postextrasys- tolic potentiation) lead to increased obstruction and an increased LVOT gradient. MR results ® T cm HZ 6 3.2 from malcoaptation of the anterior and posterior P 1. 16 19 B mitral leaflets during SAM, is typically posteri- orly directed and may be late-systolic. In patients with MR that is not posteriorly directed, care- Color Doppler Color echo from the parasternal long axis showing view, eccentric mitral regurgitation (arrows) resulting from SAM. ful assessment for structural abnormalities of (B) the mitral valve is imperative. In the setting of significant LVOT obstruction, Doppler inter- rogation of aortic flow often reveals a biphasic flow pattern, with a decrease in the midsystolic a ejection velocity. This pattern correlates with Aort LA premature closure of the aortic valve demon- strated by 2D and M-mode imaging, as well as RV with the ‘spike and dome’ pattern in the aortic pulse tracing. Septum M LV SA Conservative therapy for HOCM hocardiographic findings of hypertrophic obstructive cardiomyopathy. (A) hypertrophic cardiomyopathy. obstructive of findings hocardiographic c First-line therapy for symptomatic HOCM E 1. 1. consists of negative inotropic drugs, including ® b-adrenergic blockers, calcium channel T Continuous wave Doppler Continuous the of left ventricular outflow tract, demonstrating a significant late-peaking left ventricular outflow tract gradient at the ofsite SAM–septalcontact. cm 6 3.2 P 1. blockers, and disopyramide. b-blockers are the 16 61 HZ A Figure (C) LA: Left Left atrium; ventricle; LV: PG: Peak gradient; RV: Right ventricle; SAM: Systolic anterior motion; V: Velocity. asymmetric septal hypertrophy and SAM (arrow). drugs of choice. Dose titration is governed by 350 Interv. Cardiol. (2012) 4(3) future science group Patient selection for alcohol septal ablation for hypertrophic obstructive cardiomyopathy REVIEW symptoms, side effects and heart rate, with a Box 1. Indications for alcohol septal ablation. heart rate goal of 50–60 for amelioration of the Symptoms that interfere substantially with lifestyle despite optimal medical therapy symptoms. In patients with contraindications Septal thickness ≥16 mm b to -blockade, such as severe asthma, and in Left ventricular outflow tract gradient≥ 30–50 mmHg at rest or ≥50–60 mmHg those requiring discontinuation of b-blockade with exercise because of side effects, verapamil is often Adequately sized and accessible septal branch(es) supplying the target myocardial substituted and titrated similarly to symptoms, segment side effects and heart rate. In patients with Absence of important intrinsic abnormality of mitral valve and of other conditions symptoms refractory to optimal dosages for which cardiac surgery is indicated of these medications, disopyramide can be Absolute or relative contraindication to cardiac surgery or patient preference for added in the absence of a contraindication to alcohol septal ablation when both options are reasonable and patient has been fully this medication. Disopyramide is a class IA informed regarding benefits and risk of both procedures antiarrhythmic drug that has the additional Adapted with permission from Oxford University Press [11]. property of being a negative inotropic agent. It is necessary to monitor the corrected QT should include cardiac auscultation during the interval after initiation of disopyramide or an Valsalva maneuver (with the patient supine increase in dosage. Anticholinergic side effects to avoid syncope) for detection of provocable such as dry mouth and constipation can be obstruction. Some patients referred for ASA managed with pyridostigmine. respond to intensification of conservative Patients with symptoms refractory to medical therapy, as described above, obviating the need therapy who have a dual-chamber pacemaker for septal reduction therapy. or implantable cardioverter defibrillator already in place may be managed with a trial of pacing n Echocardiographic with short atrioventricular delay