Dr. Sorajja and Dr. Binder contributed equally to production of this study.
Valvular and Structural Heart Disease
Predictors of an optimal clinical outcome with alcohol septal ablation for obstructive hypertrophic cardiomyopathy†
Article first published online: 17 APR 2012
Copyright © 2012 Wiley Periodicals, Inc.
Catheterization and Cardiovascular Interventions
Volume 81, Issue 1, pages E58–E67, 1 January 2013
How to Cite
Sorajja, P., Binder, J., Nishimura, R. A., Holmes, D. R., Rihal, C. S., Gersh, B. J., Bresnahan, J. F. and Ommen, S. R. (2013), Predictors of an optimal clinical outcome with alcohol septal ablation for obstructive hypertrophic cardiomyopathy. Cathet. Cardiovasc. Intervent., 81: E58–E67. doi: 10.1002/ccd.24328
Conflict of Interest: None.
- Issue published online: 21 DEC 2012
- Article first published online: 17 APR 2012
- Manuscript Accepted: 3 JAN 2012
- Manuscript Received: 10 JUN 2011
Alcohol septal ablation has emerged as a therapy for patients with obstructive hypertrophic cardiomyopathy (HCM). However, there are limited data on the predictors of success with the procedure.
We examined patient characteristics and cardiac morphology as well as procedural data on 166 HCM patients (mean age, 63 years; 43% men), who underwent ablation at Mayo Clinic. Patients were contacted to determine vital status and symptoms to assess the primary endpoint of survival free of death and severe symptoms (New York Heart Association, class III or IV dyspnea).
The strongest patient characteristics that predicted clinical success were older age, less severe left ventricular outflow tract gradient, lesser ventricular septal hypertrophy, and a smaller left anterior descending (LAD) diameter. Mitral valve geometry or ventricular septal morphology did not predict outcome. Patients with ≥3 characteristics (age ≥65 years, gradient <100 mmHg, septal hypertrophy ≤18 mm, LAD diameter <4.0 mm) had superior 4-year survival free of death and severe symptoms (90.4%) in comparison to those with two characteristics (81.6%) and ≤1 characteristic (57.5%). Case volume with >50 patients was an independent predictor of survival free of severe symptoms. The volume of alcohol injected, number of arteries injected, or size of septal perforator artery were not predictive of clinical success.
Greater case volume and selection for key patient and anatomic characteristics are associated with superior outcomes with alcohol septal ablation. © 2012 Wiley Periodicals, Inc.
Dynamic left ventricular outflow tract (LVOT) obstruction is an important component of the pathophysiology of hypertrophic cardiomyopathy (HCM), leading to symptoms of dyspnea, angina, and syncope in a subset of these patients [1–3]. For those with severe, drug-refractory symptoms and LVOT obstruction, surgical myectomy provides superb hemodynamic relief of obstruction and results in durable symptom improvement in most patients when performed in experienced centers [4–9]. As an alternative therapy, percutaneous alcohol septal ablation is increasingly being performed in patients with obstructive HCM, with clinical efficacy in selected series that may approach that of surgery [10–18]. However, septal ablation may not successfully relieve obstruction in a subset of patients [17, 19].
Presently, there is a lack of understanding regarding the optimal patient selection criteria and predictors of procedure success with septal ablation [20, 21]. Accordingly, this study was undertaken to determine the predictors of an optimal clinical result in patients, who underwent treatment with septal ablation in a tertiary HCM referral center.
This study was approved by the Mayo Clinic Institutional Review Board. All patients presenting with criteria for septal reduction therapy were evaluated at the Mayo HCM Clinic. Eligibility criteria for septal ablation were (1) severe, drug-refractory cardiovascular symptoms, which were defined New York Heart Association (NYHA) class III/IV dyspnea and/or Canadian Cardiac Society (CCS) class III/IV angina; (2) dynamic LVOT obstruction (gradient ≥30 mmHg at rest or ≥50 mmHg with provocation) due to ventricular septal hypertrophy and systolic anterior motion of the mitral valve (SAM); (3) ventricular septal thickness ≥15 mm; (4) absence of significant intrinsic mitral valve disease; (5) lack of need for concomitant cardiac surgical procedure (e.g., bypass grafting, valve replacement); (6) and informed patient consent. This investigation analyzed all patients (n = 172) who underwent septal ablation for treatment of severe, drug-refractory symptoms due to obstructive HCM at the Mayo Clinic in Rochester, MN before May 1, 2009 (first case was done on December 4, 1998). Three patients who had ablation refused authorization for use of their medical records for research purposes. Three other patients were excluded from the study: two patients who had had baseline echocardiography done elsewhere and the echocardiograms were not available for review, and one patient with mitral valve prosthesis. All other patients provided informed consent in accordance with Minnesota law, leading to 166 patients analyzed in this study. The diagnosis of HCM was based on typical clinical, electrocardiographic, and echocardiographic features, with ventricular myocardial hypertrophy occurring in the absence of any other cardiac or systemic disease responsible for the hypertrophy [22, 23]. The severity of myocardial hypertrophy was assessed with M-mode and two-dimensional transthoracic echocardiography using standard techniques.
Invasive Hemodynamic Evaluation
Cardiac catheterization was completed in the fasting state under conscious sedation in all patients. In 120 patients (70%), trans-septal puncture was performed to help avoid catheter entrapment during evaluation of left ventricular (LV) pressure . LV pressure was obtained by retrograde access across the aortic valve with placement of the catheter near the LV apex in the remaining patients. In all patients, retrograde femoral access with 6 or 7 Fr guide catheters was used for simultaneous ascending aortic pressures and measurement of the LVOT gradient. Provocable LVOT gradients were assessed during Valsalva strain, isoproterenol infusion, and/or examination of the LVOT gradient on the post-premature ventricular contraction beat. For all hemodynamic variables, rapid acquisition digital records (5 msec intervals) were obtained with pressure records from 3 to 5 end-expiratory cardiac cycles for subsequent offline analysis .
Septal ablation was performed in all patients with previously described techniques [25, 26]. Briefly, a slightly oversized, over-the-wire angioplasty balloon was placed into a proximal septal perforator artery which supplied the specific area of hypertrophied septum using a 6 or 7 Fr left coronary guide catheter and standard floppy guidewires. Following inflation of the angioplasty balloon, angiographic and echocardiographic contrast was injected through the catheter to identify the perfusion bed of the artery. Then, desiccated alcohol (1–3 ml) was infused over a 3–5-min period followed by flush with normal saline. For patients who had less than 50% reduction of the LVOT gradient at rest or with provocation, additional septal perforator arteries were targeted and treated in similar fashion. Following a 5–10-min period of hemodynamic stabilization after septal ablation, residual LVOT gradients were measured at rest and with provocation (i.e., Valsalva strain, postpremature ventricular contraction). All patients without permanent pacemakers underwent placement of temporary pacemaker leads during the procedure as a precaution in case of development of high-grade atrioventricular block. Following septal ablation, patients were monitored in an intensive care unit setting for at least 3 days.
Preprocedural echocardiograms were reviewed by an observer blinded to clinical and follow-up data. Characterization of mitral valve geometry was performed offline with measurements (A diameter, D diameter, C-sept distance, and aortic-mitral plane angle) performed as previously described (Fig. 1) [27–29]. Morphology of the ventricular septum was assessed by determining the contour (sigmoid, reverse curvature, or neutral) and measuring septal thickness. Measurements of septal wall thickness were taken at the C-septum location (i.e., point of ventricular septum closest to mitral leaflet coaptation), and also 1 cm proximal, 1 cm distal, and 2 cm distal to this site. The location of these sites were marked in systole and then measured at end-diastole. The LVOT gradient was calculated from the peak velocity (v) using the modified Bernoulli equation (gradient = 4v2). Care was taken to avoid contamination of the LVOT signal with mitral regurgitation. Mitral regurgitation was graded semiquantitatively using Doppler echocardiography and color-flow imaging (grade I, mild; grade II, moderate; grade III, moderately severe; grade IV, severe) .
Angiograms were reviewed by an observer blinded to clinical and follow-up data. Quantification of angiographic data was performed offline using MEDIS QCA-CMS version 4.0 software package (Leiden, Netherlands). Right anterior oblique projections with the minimal amount of foreshortening of the left anterior descending (LAD) and septal perforator arteries were used. Measurements were made of the diameter of the ostium of the septal artery, angle of the septal artery take-off relative to the LAD artery, visible length of the septal artery, and the diameter of the LAD artery immediately proximal to the septal perforator artery (i.e., reference diameter). For all angiographic variables, 3–5 measurements were obtained and averaged. In patients where more than one artery was used for ablation, measurements for all arteries were averaged.
Follow-up evaluation was performed in all patients to determine vital status, symptoms, need for additional septal reduction therapy (e.g., surgical myectomy, repeat septal ablation), and potential complications related to septal ablation (e.g., ventricular arrhythmias, pacemaker dependency, device malfunction, or infection). This evaluation consisted of mailed questionnaires, telephone contact, and interrogation of the Social Security Death Index. For deceased patients, procurement of death certificates and interviews with next-of-kin was performed to determine cause of death. Sudden cardiac death was defined as instantaneous and unexpected death with or without documented ventricular fibrillation within 1 hr after a witnessed collapse, in patients who previously were in stable clinical condition, or nocturnal death with no antecedent history of worsening symptoms . Appropriate discharge (i.e., pacing or defibrillation) of an implanted internal cardioverter-defibrillator (ICD) device for therapy of a lethal arrhythmia (i.e., sustained ventricular tachycardia or fibrillation) was considered to be sudden cardiac death. Occurrence of stroke was defined according to standard criteria .
Acute hemodynamic procedural success was defined when all the following criteria were met: (1) a residual resting LVOT gradient of ≤10 mmHg; (2) a ≥80% reduction in the provocable peak LVOT gradient; and (3) absence of procedural death or need for emergency surgery [19, 33]. Severe symptoms in follow-up was defined as class ≥III dyspnea or angina, or debilitating syncope, or need for surgical myectomy. The definitions of hemodynamic and clinical success were based on results typically achieved with surgical myectomy, in which there is immediate relief of the LVOT gradient (residual <10 mmHg) and symptom improvement in >90% of patients. These definitions were chosen to gain insight into factors that can lead clinical success currently attributed to the surgical standard of therapy for patients with symptomatic obstructive HCM. To examine relation of cumulative experience (i.e., learning curve) at our own institution to outcomes, the patient population was arbitrarily divided into three groups by chronological order (group 1, case number 1–50; group 2, case number 51–100; and group 3, case number >100). At our institution, performance of septal ablation is restricted to three invasive operators, and case selection in this entire experience was led by a single investigator. Simple regression techniques using statistical software (Statview 4.0) were used to identify independent variables associated with procedural success. Survival estimates with 95% confidence intervals (CI) were calculated using the Kaplan–Meier method. Survival comparisons were made using a one-sample log rank test. Comparisons of continuous variables were made with the appropriate t test. Continuous variables are reported as mean ± standard deviation.
All authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
Table I lists the baseline characteristics of the 166 patients who underwent septal ablation (age, 63 ± 14 yrs; 43% men). Of note, severe cardiovascular symptoms were present in all patients (NYHA class III/IV dyspnea, 98%; CCS class III/IV angina, 19%). Three (2%) patients had previously failed surgical myectomy. Eleven patients (7%) previously had failed dual-chamber pacing therapy for relief of symptomatic LVOT obstruction. Seven patients (4%) had a history of ICD implantation for primary prevention of sudden cardiac death.
|Age (yrs)||63 ± 14|
|Men—no. (%)||71 (43)|
|NYHA class III/IV—no. (%)||162 (98)|
|CCS class III/IV—no. (%)||31 (19)|
|Atrial fibrillation—no. (%)||28 (17)|
|Prior stroke—no. (%)||5 (2)|
|Hypertension—no. (%)||88 (53)|
|Diabetes mellitus—no. (%)||13 (8)|
|Coronary artery disease—no. (%)||24 (14)|
|Prior myectomy—no. (%)||3 (2)|
|Family history of HCM—no. (%)||30 (18)|
|Family history of sudden death due to HCM—no. (%)||9 (5)|
|Internal cardioverter-defibrillator—no. (%)||7 (4)|
|Permanent pacemaker- no. (%)||22 (13)|
|Beta-receptor antagonist||118 (71)|
|Calcium-channel blocker||62 (37)|
|ACE-inhibitor or ARB||21 (13)|
Significant LVOT obstruction on echocardiography was present at rest in the majority (80%) and provocable in others (Table II). Sigmoidal septal hypertrophy was the most common ventricular morphology (57% of patients). In 52 patients (31%), the site of maximal ventricular septal hypertrophy was separate from the C-septum location (i.e., the site of the ventricular septum closest to the location of mitral leaflet coaptation). Anterior displacement of the mitral coaptation point (A/D ratio ≤0.5) was present in 60 patients (30%). Few patients had either an acute angle take off the septal artery (<90°) relative to the LAD (n = 10 or 6%) or small septal arteries (≤1.0 mm; n = 23 or 14%).
|End-diastolic diameter (mm)||44.4 ± 6.5|
|End-systolic diameter (mm)||24.7 ± 5.3|
|Mitral regurgitation grade 3 or 4—no. (%)||22 (13)|
|Resting LVOT gradient (mmHg)||70.7 ± 40.1|
|≥30 mmHg—no. (%)||132 (80)|
|Reverse curvature hypertrophy—no. (%)||26 (16)|
|Sigmoid septal hypertrophy—no. (%)||95 (57)|
|Concentric hypertrophy—no. (%)||45 (27)|
|Aortic valve distance to maximal septal thickness (mm)||26.4 ± 10.3|
|Aortic valve distance to SAM (mm)||23.6 ± 7.1|
|Maximum septal wall thickness (mm)||23.8 ± 5.0|
|1 cm proximal to C-septum site (mm)||16.1 ± 3.6|
|At C-septum site (mm)||22.7 ± 4.1|
|1 cm distal to C-septum site (mm)||20.8 ±5.6|
|2 cm distal to C-septum site (mm)||18.6 ± 5.8|
|A distance (mm)||20.7 ± 5.5|
|D distance (mm)||33.9 ± 5.2|
|A/D ratio||0.61 ± 0.15|
|Mitral leaflet length (mm)||10.7 ± 0.3|
|C-septum distance (mm)||18.4 ± 3.9|
|AMP angle (°)||142.2 ± 8.9|
|Coaptation angle (°)||26.9 ± 23.3|
Predictors of Hemodynamic Success
Septal ablation reduced the resting LVOT gradient from 74.6 ± 45.1 to 13.1 ± 20.6 mmHg in the overall population (Table III). In the subgroup of patients with resting baseline obstruction, the residual LVOT gradient after ablation was 16.2 ± 21.9 mmHg. Overall, acute hemodynamic success with septal ablation (residual resting LVOT gradient of ≤10 mmHg and ≥80% reduction in the provocable peak LVOT gradient, without death or need for surgery) occurred in 117 patients or 70%. Transient (n = 8) or permanent (n = 20) heart block necessitating new pacemaker implantation after ablation occurred in 28 patients (17%). This incidence is higher than reported in other studies, and reflects our previous experience of postoperative transient atrioventricular block progressing to complete heart block .
Hemodynamic success with septal ablation was more common in older patients, and those with lower LVOT gradients, smaller LAD diameter, and lesser ventricular septal hypertrophy (Table IV). Distance to the C-septum location was predictive of hemodynamic success in univariate analyses but not in multivariate models that adjusted for baseline characteristics.
|Resting LVOT gradient (mmHg)||74.6 ± 45.1|
|Provocable LVOT gradient (mmHg)||123.9 ± 39.7|
|Left atrial pressure (mmHg)a||17.7 ± 7.3|
|Left ventricular end-diastolic pressure (mmHg)||22.4 ± 6.5|
|LAD diameter (mm)||3.5 ± 2.8|
|Angle (°)||123.6 ± 20.7|
|Diameter (mm)||1.6 ± 0.5|
|Length (mm)||49.4 ±12.1|
|Diameter x length (mm2)||81.6 ± 34.4|
|Balloon distance from LAD||15.9 ± 5.5|
|Number septal arteries injected|
|Volume of ethanol injected (ml)||1.8 ± 0.7|
|Volume of ethanol injected per septal thickness (ml/mm)||0.8 ± 0.3|
|Post TIMI flow = 0—no. (%)||135 (81)|
|Postprocedural resting LVOT gradient (mmHg)||13.1 ± 20.6|
|Resting LVOT gradient <15 mmHg—no. (%)||124 (75)|
|Postprocedural provocable LVOT gradient (mmHg)||21.4 ± 30.6|
|Hemodynamic successb||117 (70)|
|RR||95% CI||P||RR||95% CI||P|
|1 cm proximal to SAM||0.83||0.74–0.92||0.003||–|
|At SAM-septal contact||0.87||0.79–0.95||0.002||0.85||0.75–0.96||0.009|
|LAD reference diameter||0.62||0.41–0.94||0.02||0.96||0.94–0.97||0.05|
|Case number <51||0.31||0.15–0.64||0.001||0.39||0.15–1.00||0.04|
There were no age-related differences in residual LVOT gradients (age ≥65 years vs. <65 years, 13 ± 23 vs. 13 ± 17 mmHg; P = 0.85). Anatomic differences in angiographic or echocardiographic characteristics between older and younger patients were not present, with the exception of distribution of septal hypertrophy relative to the point of anterior mitral leaflet-septal contact (C-septum). Specifically, older patients had less septal thickness both at 1 cm (20 ± 5 mm vs. 22 ± 6 mm; P = 0.05) and at 2 cm (17 ± 5 mm vs. 19 ± 6 mm; P = 0.06) distal to the C-septum.
Patients in group 1 (first 50 cases) had lower hemodynamic success than patients who had the procedure later (Fig. 2). There was no difference in hemodynamic success between patients in the latter two groups. Patients who had septal ablation early in the experience were younger and had more severe septal hypertrophy than patients in the other two groups (Table V). Both the C-septum distance and A/D ratio were lower in latter cases. In addition, the operators used smaller and shorter septal arteries with relatively less acute angulation, and injected more alcohol per maximal septal thickness in latter cases. There was no difference in the total volume of alcohol injected or number of septal perforator arteries injected between the three groups of experience. In multivariate analyses that adjusted for baseline differences, case volume remained predicted of acute hemodynamic success (Table IV).
|Case number group|
|Group 1||Group 2||Group 3|
|Age (years)||58 ± 15a||65±12||66 ± 13|
|LVOT gradient at rest (mmHg)||75 ± 39||69 ± 40||69 ± 41|
|C-septum distance (mm)||18.1 ± 4.1||19.5 ± 3.2b||17.8 ± 4.1|
|A/D ratio||0.70 ± 0.11c||0.73 ± 0.05||0.47 ± 0.09|
|Septal thickness (mm)|
|Maximal||25 ± 4c||23 ± 3||21 ± 4|
|1 cm proximal to SAM||18.0 ± 3.4c||16.5 ± 3.8||14.6 ± 2.8|
|Septal artery (mm)|
|Angle||127 ± 22||127 ± 22||119 ± 18d|
|Diameter||1.8 ± 0.4||1.6 ± 0.15||1.6 ± 0.25|
|Length||52 ± 13b||51 ± 12||46 ± 12|
|Injected (ml)||1.9 ± 0.9||1.7 ± 0.6||1.8 ± 0.5|
|Volume per maximal septal thickness (ml/mm)||0.70 ± 0.29||0.74 ± 0.30||0.92 ± 0.29d|
Mean follow-up duration was 2.4 years (maximum, 7.6 years; 99% complete). There were 13 total deaths (7.8%) in the study population, including two in-hospital deaths. Both in-hospital deaths occurred in patients in whom ablation was performed for cardiogenic shock and severe obstructive HCM as previously described . At the end of follow-up, mean NYHA functional class improved from 3.0 ± 0.13 at baseline to 1.5 ± 0.7 after septal ablation (P < 0.0001 vs. baseline), including 92 patients who were NYHA class I (55% of all patients; Fig. 3).
Patients who had acute hemodynamic success were more likely to have minimal or no cardiovascular symptoms in follow-up. Of the 114 patients with acute hemodynamic success, 99 patients (or 87%) survived free of severe cardiovascular symptoms or need for surgical myectomy. However, among the 49 patients without acute hemodynamic success, severe symptoms occurred in 12 patients (24%; χ2 = 3.1, P = 0.07) at last follow-up.
Clinical variables that predicted acute hemodynamic success (older age and lower preprocedural LVOT gradient, smaller LAD artery diameter, and less severe ventricular septal hypertrophy) also were associated with greater survival free of severe symptoms. For patients with ≥3 of the characteristics in binary fashion (age ≥65 years, resting LVOT gradient <100 mmHg, septal hypertrophy at site of SAM ≤18 mm, LAD diameter <4.0 mm), 4-year survival free of severe symptoms was 90.5% (95% CI, 81.8–99.2%) and was significantly greater than patients with fewer of these characteristics (log-rank P = 0.02; Fig. 3). For patients with two characteristics, 4-year free of severe symptoms was 81.6% (68.7–94.4%). Conversely, among patients with zero or one characteristic, survival free from severe symptoms was 57.5% (36.4–78.5%). Lower case number (group 1 patients) was associated with poorer survival free of severe symptoms (P = 0.04 vs. other two groups, Fig. 2).
The principal findings of this study are: (1) using a rigorous definition of procedural success, acute hemodynamic relief of LVOT obstruction occurred in 70% of patients with alcohol septal ablation; (2) hemodynamic success and survival free of severe symptoms are more likely in older patients, and those with lower LVOT gradients, smaller LAD diameter, and less severe hypertrophy; (3) case experience is an important determinant of clinical success with septal ablation.
For patients with drug-refractory symptoms due to obstructive HCM, alcohol septal ablation has been found to be an effective therapy that can result in symptom improvement comparable to that of surgical myectomy [11–18]. Nonetheless, there remain a number of unresolved issues regarding the role of septal ablation in our therapeutic armamentarium, and there are few data on the most appropriate patient selection for the procedure. In this study, we selected a rigorous definition of hemodynamic success (residual resting LVOT gradient of ≤10 mmHg and ≥80% reduction in the provocable peak LVOT gradient), comparable to the effects of surgical myectomy, to identify predictors of an optimal clinical outcome with septal ablation. With this definition, acute hemodynamic relief of LVOT obstruction was achieved in only 70% of patients. The acute hemodynamic success did predict clinical outcome. Thus, further refinements in patient selection for alcohol septal ablation are needed to approach the success that has been achieved with surgical myectomy.
Older patient age was an important predictor of optimal clinical outcome. There were no significant differences in angiographic or echocardiographic characteristics between older and younger patients, with the exception of septal thickness proximal and distal to the point of mitral leaflet-septal contact. The more discrete nature of ventricular septal hypertrophy in those who were older may have contributed to greater hemodynamic success in these patients. Residual septal hypertrophy may predispose toward intraventricular flow abnormalities that become more evident during provocation or physical exertion . Of note, sigmoid septal hypertrophy was common in the older patient population, possibly due to greater selection of surgical myectomy for patients with more severe degrees of hypertrophy.
Overall, the average residual LVOT gradient was 13 mmHg, comparable to previous reports of septal ablation [11–18]. There were not age-related differences in residual LVOT gradients. However, the residual gradients after ablation are higher than typically achieved with surgical myectomy (usually <5–10 mmHg), and may not be tolerated by younger or more active patients. Notably, among 120 who had residual LVOT gradients of <10 mmHg with septal ablation, 102 of these patients (or 85%) survived free of severe symptoms or need for surgical myectomy in follow-up.
Despite a detailed examination of cardiac morphology, the only consistent echocardiographic predictors of optimal outcome were severity of septal hypertrophy and LVOT obstruction. In addition, LAD diameter was the only angiographic variable associated with clinical success. The reason for the relation between LAD diameter and outcome is unclear but may be related to the size of coronary artery associated with greater left ventricular mass of myocardium perfused. Nevertheless, for patients with relatively milder septal hypertrophy, less severe LVOT obstruction, and comparatively smaller LAD diameter, septal ablation was efficacious with >90% of patients having an optimal clinical result in follow-up. Procedural success with septal ablation is dependent on the ability to access and treat the perfusion bed of the entire myocardium that contributes to the development of LVOT obstruction. This ability is affected by coronary anatomy and limitations of the therapeutic agent (i.e., alcohol), whose efficacy may be inhibited by incomplete perfusion of the targeted myocardium and collateralization of the hypertrophied myocardium via untreated septal arteries (Figs. 4 and 5). Of note, alcohol dosing was not related to outcome in our study, but our mean delivered dose was only 1.8 ± 0.7 ml. Multiple prior studies have shown high clinical efficacy and have suggested improved long term outcome with lower alcohol doses (<2 ml) [35, 36]. Anterior encroachment of the mitral valve and higher LVOT gradients both have been found to be predictive of lower clinical success in previous reports of septal ablation [28, 33]. Thus, septal ablation may be more effective in patients with milder myocardial hypertrophy and LVOT obstruction.
Presently, there is no clear consensus on requirements for clinical competency to perform alcohol septal ablation . Septal ablation uses conventional equipment and techniques of percutaneous coronary intervention, but the clinical management of patients with HCM is complex and requires a multidisciplinary team approach. In this study, there were differences in patient characteristics and procedure variables that might suggest changes in both patient selection and performance of septal ablation with case experience. We observed greater acute hemodynamic success and higher likelihood of survival free of severe symptoms for patients who had the procedure in the latter stages of case experience (>50 cases). This learning curve resembles the published experience with other structural heart disease interventions and occurred in a tertiary referral institution with long-standing practice in therapy for HCM  Given these observations and the relatively low volume of patients with HCM who are candidates for percutaneous or surgical relief of LVOT obstruction, septal reduction therapy should be undertaken in institutions with established experience in an integrated team approach for HCM.
The present investigation was retrospective, which has known inherent limitations and biases. Only patients who underwent septal ablation are included in this study; the impact of those with unfavorable anatomic characteristics that led to exclusion from the procedure cannot be assessed. Nonetheless, examination of the patient characteristics was performed in a comprehensive, detailed manner with investigators blinded to hemodynamic and clinical outcome data. Data on infarct size and area at risk with contrast echocardiography was not available. These variables have been found to predictive of outcome in prior studies but require prospective evaluation. Ventricular remodeling occurs in patients with septal ablation [39, 40]. Although acute hemodynamic relief occurred in only 70% of patients, remodeling likely led to a further reduction in LVOT gradients and contributed to symptom relief in patients without initial procedural success. Because of geographic limitations regarding patient follow-up, data on change in LVOT gradients during follow-up were not available.
Optimal outcomes with septal ablation are greater when the procedure is performed in older patients, and in those with lower LVOT gradients, smaller LAD, and less severe ventricular septal hypertrophy. Case volume is an important predictor of clinical success with septal ablation.
- 21Task Force on Clinical Expert Consensus Documents. American College of Cardiology. Committee for Practice Guidelines. European Society of Cardiology. American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy. A report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents and the European Society of Cardiology Committee for Practice Guidelines. J Am Coll Cardiol 2003; 42: 1687–713., , , , , , , , , , .
- 36Alcohol septal ablation for hypertrophic obstructive cardiomyopathy: lower alcohol dose reduces size of infarction and has comparable hemodynamic and clinical outcome. Catheter Cardiovasc Interv 2004; 63: 231–235., , , et al.
- 37ACCF/AHA/SCAI update of the clinical competence statement on cardiac interventional procedures: a report of the American College of Cardiology Foundation/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training (Writing Committee to Update the 1998 Clinical Competence Statement on Recommendations for the Assessment and Maintenance of Proficiency in Coronary Interventional Procedures). J Am Coll Cardiol 2007; 50: 82–108., , , et al.