Long-Term Outcomes in High-Risk Symptomatic Patients With Hypertrophic Cardiomyopathy Undergoing Alcohol Septal Ablation
Deborah H. Kwon, MD*,
Samir R. Kapadia, MD, FACC*,
E. Murat Tuzcu, MD, FACC*,
Carmel M. Halley, MD*,
Eiran Z. Gorodeski, MD, MPH*,
Ronan J. Curtin, MD*,
Maran Thamilarasan, MD, FACC*,
Nicholas G. Smedira, MD, FACC ,
Bruce W. Lytle, MD, FACC,
Harry M. Lever, MD, FACC*,
Milind Y. Desai, MD, FACC*,*
* Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio
Department of Cardiothoracic Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
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Abstract
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Objectives: We sought to assess outcomes of alcohol septal ablation (ASA) in high-risk patients.
Background: Because surgical myectomy is the preferred treatment in patients with symptomatic hypertrophic obstructive cardiomyopathy (HOCM) at our institution, we perform ASA in patients who are at high risk for surgery.
Methods: We studied 55 symptomatic HOCM patients (mean age 63 ± 13 years, 67% women, mean follow-up 8 ± 1 years), at high risk for surgery (as the result of age/comorbidities) who had ASA between 1997 and 2000. The following were recorded at baseline, 3 months, and 1 year: septal thickness, maximal (resting or provocable) left ventricular outflow tract gradient, Minnesota living with heart failure questionnaire score, and the presence of a permanent pacemaker. All-cause mortality was recorded.
Results: No patients died at 48 h, 2 died at 1 year, 7 died at 5 years, and 13 died at 10 years. Only age >65 years at time of ASA predicted long-term mortality (log-rank p = 0.03). Mean maximal left ventricular outflow tract gradient (104 ± 35 mm Hg vs. 49 ± 28 mm Hg), septal thickness (2.4 ± 0.4 cm vs. 1.8 ± 0.6 cm), and Minnesota living with heart failure score (63 vs. 25) improved at 3 months, compared with baseline (all p < 0.001), with no significant changes at 1 year. New permanent pacemaker was present in 26% of patients.
Conclusions: In symptomatic HOCM patients who are at high risk for surgery, ASA is associated with symptomatic improvement and low short-term mortality; with long-term mortality only associated with older age at time of procedure. In symptomatic HOCM patients at high-risk for surgery, ASA is a viable option.
Key Words: hypertrophic cardiomyopathy • percutaneous alcohol septal ablation • long-term outcomes
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Abbreviations and Acronyms
| | AICD = automatic implantable cardioverter defibrillator | | ASA = alcohol septal ablation | | HOCM = hypertrophic obstructive cardiomyopathy | | LVOT = left ventricular outflow tract | | MLWHF = Minnesota Living With Heart Failure | | MR = mitral regurgitation | | NYHA = New York Heart Association | | PPM = permanent pacemaker | | SSDI = Social Security Death Index | | VT = ventricular tachycardia |
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In patients with hypertrophic obstructive cardiomyopathy (HOCM), the presence of dynamic left ventricular outflow (LVOT) obstruction is associated with adverse outcomes (1). Despite maximal medical therapy, such patients frequently remain intractably symptomatic and often require further therapy. Although surgical myectomy has excellent long-term outcomes, it is invasive, and its results are limited to a few centers with adequate experience (2–6). After the introduction of percutaneous alcohol septal ablation (ASA) (7), there was a tremendous surge in the number of such procedures being performed (8). However, enthusiasm for ASA has been tempered recently as the result of concerns for increased periprocedural complications, risk of ventricular tachycardia (VT), and potential sudden cardiac death (9,10). Although multiple studies have demonstrated symptomatic improvement and excellent short-term survival, a paucity of data still exists regarding long-term outcomes after ASA (11–15).
We have achieved excellent long-term outcomes in patients who undergo surgical myectomy at our institution (16). Therefore, it is the preferred treatment in symptomatic HOCM patients who do not have prohibitive comorbidities. We typically perform ASA in symptomatic HOCM patients that are considered to be at high risk for surgery (as the result of age or other comorbidities). Primarily, we sought to assess the short- and long-term outcomes of percutaneous ASA in such high-risk HOCM patients. Secondarily, we compared the long-term mortality of patients undergoing ASA to those undergoing isolated surgical myectomy.
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Methods
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Patient selection and acquisition of clinical data.
Between 1997 and 2000, 645 patients were evaluated at our institution for suspected HOCM. The diagnosis of HOCM was based on standard clinical criteria, i.e., history, physical examination, electrocardiography, and echocardiography (17,18). Baseline demographic, clinical, medication use, and electrocardiographic data were obtained at the time of initial office visit. All patients were taking medications at maximum tolerable dosages. The decision regarding further treatment (surgery vs. ASA) was based upon the presence of symptoms. The Social Security Death Index (SSDI) was queried to determine all-cause mortality. We chose to use all-cause mortality as our primary end point because it is more objective and unbiased than "cardiac mortality" (19). The cause of death was ascertained if it was available.
Alcohol septal ablation group.
Of these 645 individuals, 55 symptomatic patients were deemed to be high-risk surgical candidates (41% because of age >70 years, 30% because of severe lung/liver or kidney disease, 11% because of morbid obesity, 11% because of significant autoimmune disease, and 7% because of other reasons) by a consensus among the cardiologists and cardiothoracic surgeons participating in the care of each patient. Patients with a primary mitral valve problem were excluded, and higher-risk surgery (myectomy plus mitral valve surgery) was still preferred in such patients. These 55 high-risk patients were referred for ASA. After informed consent, these patients were prospectively included in a registry, approved by the institutional review board, established in 1997. The presence of a permanent pacemaker (PPM) at baseline or inserted just before or after ASA in the periprocedural phase) and automatic implantable cardioverter defibrillator (AICD) were recorded. The presence of VT (sustained or nonsustained), defined as 3 or more consecutive ventricular beats at a rate >120 beats/min, was documented (20). All patients undergoing ASA filled out a Minnesota Living With Heart Failure (MLWHF) questionnaire at baseline and at 3 months' follow-up (21). New York Heart Association (NYHA) functional class was determined at baseline and at 3 months' follow-up. The need for repeat ASA and myectomy was recorded.
Myectomy group.
In the same time frame (1997 to 2000), 98 patients underwent isolated myectomy (excluding those patients where myectomy was combined with another procedure) (16). No patients in the myectomy group had severe renal, kidney, or lung disease. A propensity analysis that matched patients based on age, gender, and baseline NYHA functional class was used to identify myectomy patients that formed a control group for comparison to those that underwent ASA.
Echocardiography protocol.
Baseline and follow-up echocardiographic studies were performed with commercially available instruments at the time (Sequoia, Acuson, Mountview, California; Phillips, Andover, Massachusetts; and GE, Milwaukee, Wisconsin), as part of standard clinical practice. Basal interventricular septal thickness was recorded with a standard M-mode echocardiography. Left ventricular outflow peak velocity was measured by continuous-wave Doppler echocardiography, and LVOT pressure gradient was estimated with the simplified Bernoulli equation (22). Care was taken to avoid contamination of the LVOT waveform by the mitral regurgitation jet (1). In patients with resting LVOT gradients <30 mm Hg, provocative maneuvers, including Valsalva and amyl nitrite, were used. The degree of resting mitral regurgitation was assessed by color Doppler and quantified by flow convergence method (23), on a scale of 0 to 4+ (0 = none, 1+ = mild, 2+ = moderate, 3+ = moderately severe, and 4+ = severe).
Alcohol septal ablation protocol.
All patients that were candidates for ASA underwent diagnostic catheterization to evaluate for concomitant coronary artery disease, suitability of a septal perforator branch of the left anterior descending artery, appropriate angle of origin, and length of the septal branch. Significant epicardial coronary artery disease was defined as >50% stenosis. At the beginning of the procedure, a temporary pacemaker was placed in the right ventricle. The protocol, under contrast echocardiography guidance, has been described previously (14).
Statistical analysis.
Baseline demographics, risk factors, and clinical variables are descriptively summarized for the group. Continuous variables are expressed as mean ± standard deviation. Categorical data are presented as percent frequency. Differences between the groups (ASA vs. myectomy) were compared with the use of the Student t test for continuous variables and the chi-square test for categorical variables. Paired t-testing was performed to compare differences between same patients at baseline and during follow-up. Survival analysis was performed with Cox proportional hazards and relative risk of the individual tested variables was calculated. Univariate survival analysis is graphically demonstrated with the use of Kaplan-Meier curves. As discussed earlier, we performed propensity matching with logistic regression analysis (24). Data assembly and basic statistical comparisons were performed with JMP Software version 6.0.2 (SAS Institute, Cary, North Carolina). Advanced statistical analysis was performed with Statistica version 6.1 (Statsoft, Tulsa, Oklahoma). A p value < 0.05 was considered significant.
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Results
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Baseline data for the ASA and myectomy groups.
All ASA patients were symptomatic at baseline (96% had NYHA functional class  3) and a significant proportion had evidence of pre-existing conduction abnormalities (5 patients had left bundle branch block, 7 had right bundle branch block). There were no patients with obstructive left main or proximal left anterior descending disease. All living patients returned at 3 months, with 47 returning at 1 year for symptom evaluation and echocardiography. All-cause mortality was ascertained in every patient by SSDI. The mean follow-up for outcomes (all cause mortality and repeat interventions) was 8 ± 1 years in ASA group and 8 ± 2 years in myectomy group. The baseline demographics are shown in Table 1.
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Table 1 Baseline Characteristics of Patients Who Underwent Alcohol Septal Ablation and Surgical Myectomy Between 1997 and 2000
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Outcomes data of both groups.
In the ASA group, there were no deaths at 48 h, 1 (2%) at 1 month, 2 (4%) at 1 year, 7 (13%) at 5 years, and 13 (24%) at up to 10 years' follow-up. Only age >65 years at time of ASA was predictive of worse long-term survival (p = 0.03, Figs. 1 and 2). Table 2
describes the characteristics of ASA patients who died during follow-up.
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Figure 1 Kaplan-Meier Curves Demonstrating Difference in Long-Term Survival in Alcohol Ablation Group, on the Basis of Age
Patients >65 years of age had worse survival than those younger.
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Figure 2 Univariate Survival Analysis of Patients Undergoing Alcohol Ablation
Only patients who were >65 years of age achieved statistical significance (p < 0.05; other: p > 0.10). CI = confidence interval; LVOT = left ventricular outflow tract; MR = mitral regurgitation; VT = ventricular tachycardia.
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During follow-up, mortality in myectomy group was 8%. Subsequently, we performed propensity matching of 2 groups, based on age, gender, and baseline NYHA functional class, which resulted in 2 groups of 28 patients each (Table 3). In these groups, on univariate survival analysis, there was no significant difference in long-term mortality (log-rank p value = 0.12).
Clinical and echocardiographic response after ASA.
After ASA, there was a significant reduction in number of patients with NYHA functional class 3 (96% vs. 17%). All patients had normal ejection fractions at baseline (>55%), with no change at follow-up. Most patients had an improvement in MLWHF score (98%), maximal LVOT gradients (82%), upper septal thickness (91%), and mitral regurgitation (MR) (85%) at 3 months versus baseline (Figs. 3 to 5). The mean MLWHF score (62 ± 22 vs. 24 ± 22), resting LVOT gradient (31 ± 26 mm Hg vs. 72 ± 46 mm Hg), maximal (either resting or provocable) LVOT gradient (49 ± 28 mm Hg vs. 104 ± 35 mm Hg), maximal upper septal thickness (1.8 ± 0.6 cm vs. 2.4 ± 0.4 cm), and mean MR (1.4 ± 0.9 vs. 2.2 ± 1.1) improved at 3 months versus baseline (all p < 0.001). Of the 47 patients that had 1-year follow-up data available, the resting and maximal LVOT gradients changed minimally (31 ± 39 mm Hg and 51 ± 50 mm Hg, all p = NS), compared with 3-month gradients. There was no further reduction in upper septal thickness at 1-year follow-up (1.91 ± 0.47 cm, p = NS). However, the MR at 1-year follow-up was slightly more than at 3 months (2.6 ± 1.8, p < 0.01).
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Figure 3 Change in Minnesota Living With Heart Failure Score at 3 Months, Compared With Baseline
All patients had an improvement in the Minnesota Living With Heart Failure score at 3 months’ follow-up.
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Figure 4 Change in Maximal (Resting or Provocable) LVOT Gradient at 3 Months, Compared With Baseline
Vast majority of the patients had a significant reduction in the maximal left ventricular outflow tract (LVOT) gradient at 3-month follow-up.
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Figure 5 Changes in Basal Interventricular Septal Thickness and Mitral Regurgitation
(A) Change in basal interventricular septal thickness at 3 months, compared with baseline. (B) Change in mitral regurgitation at 3 months, compared with baseline.
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Failure of ASA and need for repeat intervention.
Nine patients had persistent or recurrent symptoms and underwent repeat intervention. Five patients underwent myectomy, 3 underwent repeat ASA, and 1 had additional mitral valve surgery at our institution (at up to 10 years' follow-up). In this group of 9 patients, the mean age was 64 ± 13 years, and 5 patients were women. These patients' persistent symptoms were reflected in the mean 3-month MLWHF score of 36 ± 21. Furthermore, at 3 months, the mean upper septal thickness and maximal LVOT gradient were 2.1 ± 0.4 cm and 69 ± 33 mm Hg, respectively. After the repeat procedure, the mean upper septal thickness and maximal LVOT gradient improved to 2.1 ± 0.4 cm and 13 ± 22 mm Hg, respectively. All patients had NYHA functional class <2. Two of these patients died during follow-up.
Complications after ASA.
Permanent pacemakers were implanted in 14 of 55 (25.5%) patients after ASA. Thirteen patients were PPM dependent at 3-month follow-up because of underlying complete heart block. Of the 18 patients that had Holter monitoring at baseline, none had documented VT. At 1-year follow-up, 36 had Holter monitoring. Eleven of these patients had nonsustained VT on Holter monitoring, and 3 of these patients had an AICD placed because of sustained VT. None of the patients had AICD discharges at 1-year follow-up. There were no procedure-related mortalities. One patient had a dissection of left anterior descending artery, requiring emergent stenting. No alcohol was given, and this patient was excluded from analysis.
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Discussion
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To the best of our knowledge, this study is one of the first to evaluate the long-term outcomes of ASA in symptomatic HOCM patients who were deemed to be at high risk for surgery and compare them with patients who underwent surgical myectomy. The immediate hemodynamic and symptomatic improvements were maintained up to 1 year after ASA in a majority of cases. On survival analysis, age >65 years was the only predictor of long-term outcomes after ASA. Patients >65 years were considered to be at greater risk for surgery (particularly if they had other comorbid conditions) by our cardiothoracic surgeons. Therefore, this age was used as the cutoff for survival analysis. The comorbid condition that precluded the individual patient from undergoing surgical myectomy was generally the cause of mortality in patients <65 years that died after ASA (Table 3). A recent study demonstrated favorable results in 329 HOCM patients at 10 years after ASA (15). However, this study's patient population was much healthier than ours, with no significant comorbidities that would preclude them from undergoing surgical myectomy.
We further compared the long-term mortality data of these patients with a group of propensity-matched symptomatic HOCM patients who underwent isolated myectomy during the same time frame. There was no difference in mortality between these 2 groups. Mortality in ASA group was comparable with the published long-term myectomy outcomes (at least 5 years' follow-up) at other institutions (1.3% to 3.5% per year) (4,25).
There was also an increased frequency of PPM placement in patients after ASA, likely related to the older baseline age of the population. A recent study has demonstrated that assessment of intracardiac conduction during ASA can help identify patients that are likely to develop future complete heart block after the procedure (26). A major concern with ASA is the theoretic increased risk of VT and sudden cardiac death (27). Our study reiterates previous findings that a significant proportion of these patients have VT (27). However, only 3 patients in the ASA group had an implantable cardioverter defibrillator implanted, with no discharges. The significance of VT is likely diminished in older, as compared to younger, HOCM patients.
Furthermore, reintervention may be necessary after ASA. There are many reasons for a suboptimal result after ASA, including the degree/location of septal regression following alcohol injection (28) and multifactorial etiology of LVOT obstruction, including the presence of mitral apparatus abnormalities like anterior displacement of the papillary muscles (29–31) and leaflet elongation (32). Hence, the decision regarding ASA versus surgery should likely involve the following factors: 1) understanding the etiology of LVOT obstruction; 2) institutional experience with surgical myectomy; and 3) patient specific comorbidities. In patients with concomitant mitral valve problems, myectomy plus mitral valve surgery should be considered.
Study limitations and future outlook.
Because this study was conducted at a large tertiary-care referral center, there is a distinct possibility of selection bias. Our highly skilled cardiothoracic surgeons have extensive experience in performing myectomy; hence, the threshold for referring patients for ASA is very high. Thus, patients undergoing ASA were sicker and deemed poor candidates for surgery. One might argue that these variables make a comparison of outcomes between ASA (high-risk group) and myectomy (low-risk group) flawed. Nevertheless, there is no significant difference in mortality between the 2 propensity-matched groups. However, the sample size expectedly becomes very small after propensity matching. To fully ascertain superiority/noninferiority of one technique over another, a randomized study is warranted, if deemed ethically feasible.
Another limitation includes a loss of follow-up with time. At our tertiary-care center, patients are referred for high-risk procedures from all over the country, and some of these patients prefer to follow-up locally. However, in the current study, the lack of follow-up pertains only to symptom/arrhythmia evaluation and echocardiographic data. Because we performed a SSDI query, we have an accurate estimate of all-cause mortality. Holter monitoring was not available in all patients at baseline or during follow-up. Also, short-term (24- to 48-h) arrhythmia monitoring can potentially miss episodes of asymptomatic VT. These factors might have potentially accounted for no documented VT at baseline. The impact of VT and potential benefit of ICD in such patients needs to be prospectively studied.
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Conclusions
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In symptomatic HOCM patients who are deemed to be high-risk for surgery, ASA is associated with substantial symptomatic improvement and low short-term mortality, with long-term mortality only associated with older age at the time of procedure. After adjustment of baseline differences, the long-term mortality is not significantly different when compared to myectomy. In symptomatic HOCM patients who are at high-risk for surgery, ASA is a viable option.
* Reprint requests and correspondence: Dr. Milind Y. Desai, Department of Cardiovascular Medicine, Desk F 15, 9500 Euclid Avenue, Cleveland, Ohio 44195. (Email: desaim2{at}ccf.org).
Manuscript received January 11, 2008;
revised manuscript received April 11, 2008,
accepted May 22, 2008.
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Abstract
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