Circulation. 2007;116:207-216
doi: 10.1161/CIRCULATIONAHA.107.688135
(Circulation. 2007;116:207-216.)
© 2007 American Heart Association, Inc.
Controversies in Cardiovascular Medicine |
Most Fully Informed Patients Choose Septal Ablation Over Septal Myectomy
Michael A. Fifer, MD
From the Cardiology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston.
Correspondence to Michael A. Fifer, MD, Cardiology Division, Massachusetts General Hospital, 55 Fruit St, Gray/Bigelow Bldg, Ste 800, Mailstop 843, Boston, MA 02114-2696. E-mail mfifer{at}partners.org
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Introduction
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Hypertrophic cardiomyopathy (HCM) is a disease characterized
by primary hypertrophy of the left (and sometimes right) ventricle.
The clinical manifestations of the disease are dyspnea, angina,
and a continuum encompassing lightheadedness, presyncope, syncope,
and sudden death. Although HCM often is caused by an identifiable
mutation in a gene coding for a sarcomeric protein and inherited
in an autosomal-dominant pattern, many patients do not have
any relatives in whom the disease is manifest. The prevalence
of HCM is estimated to be 0.2%, with
600 000 Americans affected.
Response by Maron p 216
Several anatomic variants of HCM exist. Of these, hypertrophic obstructive cardiomyopathy (HOCM) is the variant that has been the subject of the most intense investigation. HOCM was previously termed idiopathic hypertrophic subaortic stenosis and is characterized by 4 closely related pathoanatomic features (Figure 1).1 Obstruction to left ventricular (LV) outflow is caused by bulging of the thickened septum into the left ventricular outflow tract (LVOT) during systole, with apposition of the anterior (occasionally posterior) leaflet of the mitral valve, which demonstrates systolic anterior motion. Mitral regurgitation usually is present, although the degree varies greatly among patients with HOCM. LVOT gradients may be present at rest or only during Valsalva maneuver or exercise (provocable obstruction). A recent report suggests that if patients with provocable gradients are included, most patients with HCM have the obstructive form of the disease.2
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Figure 1. Schematic depiction of 4 elements of the pathoanatomy of HOCM showing asymmetric septal hypertrophy (ASH), systolic anterior motion (SAM) of the anterior leaflet of the mitral valve, an LVOT gradient, and mitral regurgitation (MR). LA indicates left atrium. Reprinted from Fifer.1
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Management of HCM
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The management of HCM may be considered as consisting of 4 elements
(
Table 1).
3 For patients at high risk of sudden death, implantation
of a cardioverter–defibrillator is considered.
4 In patients
with HOCM, the first line of therapy for symptoms consists of
medications with negative inotropic properties that diminish
the extent of septal bulging into the LVOT; these are β-blockers,
calcium channel blockers (of which there has been the largest
experience with verapamil), and disopyramide. In most patients,
symptoms can be adequately controlled with these medications
used alone or in combination. In patients with HOCM and symptoms
refractory to optimal medical therapy, mechanical measures aimed
at relief of the outflow tract obstruction are considered.
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Septal Myectomy
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The original mechanical management of patients with HOCM and
refractory symptoms consisted of septal myotomy, or simple incision
of septal muscle, first performed in 1958.
5,6 Myotomy was soon
replaced by septal myectomy, or removal of septal muscle.
7,8 In this approach, the surgeon visualizes the thickened septum
through an incision in the aortic root and excises a rectangular
segment from the basal septum toward the apex. In patients with
septal thickness <15 to 18 mm, septal myectomy incurs a risk
of causing a ventricular septal defect; in these cases, an alternative
strategy is repair or replacement of the other structure implicated
in LVOT obstruction, namely the mitral valve.
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Pacing
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Dual-chamber pacing with a short atrioventricular delay was
suggested as early as 1968 as an innovative approach for the
management of HOCM.
9 Although marked beneficial effects of pacing
were reported in uncontrolled series,
10 these findings have
not been reproduced in randomized controlled trials,
11,12 although
a suggestion exists that a small subset of patients benefits
from pacing.
12
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Septal Ablation
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Transcatheter ablation of the septum with ethanol was first
performed at the Royal Brompton Hospital in London in 1994.
13,14 The first patient to undergo septal ablation had severe symptoms
despite β-blockade and a resting gradient of 25 mm Hg that
increased markedly during the Valsalva maneuver. Peak creatine
kinase was 2500 U/L. She was discharged 3 days after septal
ablation and was asymptomatic 10 months later. The results were
similar for the other 2 patients in the initial report, both
of whom also had LVOT gradients that were low at rest and higher
in response to provocative maneuvers.
Because the proximal septal branches of the left anterior descending coronary artery supply the conduction system as well as the basal septum, atrioventricular block is a common complication of septal ablation. For this reason, a temporary pacemaker is placed before the procedure. With standard coronary angioplasty guiding catheters, guidewires, and balloon catheters, the most proximal septal branch that can be catheterized is entered, and the angioplasty balloon is inflated. X-ray contrast is injected through the balloon catheter to confirm filling of the septal branch and absence of backflow into the left anterior descending coronary artery itself. Correct catheter placement also is confirmed by myocardial contrast echocardiography (see below). Dehydrated ethanol, usually 1 mL at a time, is then injected slowly through the balloon catheter, causing a targeted myocardial infarction; the usual total dosage of ethanol is 1 to 3 mL. Patients receive narcotics and experience mild to moderate chest pain, usually burning in quality. The gradient can usually be reduced to <20 mm Hg (Figure 2). In some cases, ethanol is injected selectively into septal subbranches15; in others, it is injected into 2 or 3 septal branches. After delivery of ethanol, distal flow in the affected septal branch is slow or absent (no-reflow phenomenon; see Figure 3).16
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Figure 2. Preablation (A) and immediately postablation (B) LV and femoral arterial pressures in the first patient to undergo septal ablation at Massachusetts General Hospital. Reprinted from Fifer.1
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Figure 3. Left coronary arteriogram before (A) and after (B) septal ablation demonstrating the no-reflow phenomenon. The septal branch (arrow) into which ethanol was injected has a truncated appearance (circle, inset) after septal ablation. Reprinted from Baggish et al16 with permission of Elsevier. Copyright © 2006.
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Myocardial contrast echocardiography was introduced into the procedure to localize the septal branch supplying the critical septal segment (ie, the point of mitral valve contact and maximal flow acceleration).17,18 Myocardial contrast may be achieved with agitated x-ray contrast or an echocardiographic contrast agent. Myocardial contrast echocardiography may identify inappropriate sites for injection of ethanol such as a septal branch supplying myocardium too close to the apex, papillary muscle, inferoposterior LV, or right ventricle. Incorporation of this technique reduces the number of septal branches into which ethanol is injected and may both improve success rate and lower marker release and the need for pacing.17,19
Peak creatine kinase is 500 U/L per 1 mL ethanol injected. In patients with failed septal ablation who subsequently undergo septal myectomy, we have found pathological evidence of necrosis of the vascular endothelium (Figure 4), suggesting that ethanol is toxic to both the coronary circulation and the myocardium.16
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Figure 4. Pathology of septal ablation showing the absence of nuclei, indicating necrosis, in myocytes (solid arrow) and vascular endothelial cells (dotted arrow). Reprinted from Fifer.1
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What Do We Know About the Efficacy and Safety of Septal Myectomy?
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Septal myectomy performed by skilled surgeons at high-volume
centers results in abolition of the LVOT gradient and relief
of symptoms in the great majority of cases (
Table 2).
20–23 Results in patients with provocable obstruction are comparable
to those in patients with resting obstruction.
20 Early mortality,
which was high in the early experience with this operation,
has been reduced to
2% in young or middle-aged otherwise healthy
patients undergoing isolated septal myectomy. In older patients,
those with comorbid conditions, and those requiring other concomitant
cardiac surgery, mortality is considerably higher.
22,24,25
Complications of septal myectomy include those peculiar to the operation (eg, ventricular septal defect [1%]20,26 and complete heart block for which a permanent pacemaker is required [3% to 10%, lower in the absence of preexisting conduction system disease]),20–22,26 and those that pertain to any cardiac operation (eg, postoperative bleeding with tamponade, sepsis, and stroke).20–22 Postoperative left bundle-branch block occurs in 40% to 56% of patients.24,26,27 When septal myectomy is successful and uncomplicated, studies with a mean follow-up of 6 to 12 years indicate that the improvement is usually sustained.20–22,25,26 Successful septal myectomy results in a decrease in LV mass that is much greater than that attributable to the removal of the septal myocardium itself and that undoubtedly results from relief of pressure overload.28
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What Do We Know About the Efficacy and Safety of Septal Ablation?
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Septal ablation performed by skilled operators at high-volume
centers results in a marked immediate decrease in LVOT gradient
in the great majority of patients.
17,29–32 In a sizable
subset of patients, the gradient response is triphasic, with
immediate reduction, early reappearance, and by 3 months after
the procedure, sustained fall.
33,34 This sequence suggests that
myocardial stunning may be responsible in large part for the
immediate reduction in gradient. After recovery from stunning,
ultimate gradient reduction is associated with remodeling of
the septum with an increase in LVOT area.
35 Improvement in symptoms
occurs over the same 3-month period. Symptom relief and gradient
reduction are achieved in >80% of patients (
Table 3).
32,36,37 A clinical impression exists that patients with septal thickness
approaching or exceeding 30 mm may not achieve full benefit
from septal ablation.
In association with the amelioration of the LVOT gradient, the degree of mitral regurgitation decreases,17,29,38 as does the size of the left atrium.17,39 In response to a reduction in the systolic pressure load, systolic myocardial function improves in the free wall40 and hypertrophy regresses throughout the LV (as after aortic valve replacement for aortic stenosis; Figure 5).19,39,41,42 Reduction in LVOT gradient and regression of LV hypertrophy are accompanied by improvement in diastolic LV function,17,29,43 which correlates with an increase in exercise capacity.38
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Figure 5. Regression of LV hypertrophy after septal ablation, including in segments remote from ablation site. Reprinted from van Dockum et al42 with permission of the publisher. Copyright © 2005, The American Heart Association.
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Two studies have demonstrated that, as with septal myectomy, the benefit of septal ablation in patients with provocable gradients is similar to that in patients with resting gradients.44,45 These studies provide retrospective support for Sigwart’s13 performance of septal ablation in his first 3 patients, all of whom had provocable obstruction. The standard provocation for deciding whether a patient is a candidate for septal ablation is exercise. Because exercise is not practical in an instrumented patient, patients triaged to ablation on the basis of exercise-induced gradients may receive dobutamine or isoproterenol during the procedure to provide a gradient suitably high to serve as a "target" for ablation.
Temporary complete atrioventricular block occurs during the procedure in approximately half of the patients.17,29,46–48 After the procedure, right bundle-branch block is present in approximately half of the patients.17,18,27,29,46,48 A corollary is that patients with preexisting left bundle-branch block usually require permanent pacing after ablation.48 Another corollary is that patients who undergo sequential septal ablation and septal myectomy (which frequently causes left bundle-branch block) also are likely to require permanent pacing.49 Although the rate of permanent pacemaker placement was as high as 38% early in the septal ablation experience,29 it has fallen with the introduction of myocardial contrast echocardiography and the use of lower dosages of ethanol, with 1 group reporting an incidence of <10%.17,19,48
In-hospital mortality is 0% to 4%.19,29,30 Deaths have been due to coronary dissection,30 pulmonary embolism,17 refractory ventricular fibrillation,36 right ventricular perforation by the temporary pacemaker,36 pump failure,15 and heart block.29 In-hospital sustained ventricular tachyarrhythmias occur in 5% of cases.16 The theoretical concern that after septal ablation, arrhythmic sudden death resulting from superimposition of a myocardial infarction on a cardiomyopathic substrate would be common has fortunately not been realized in clinical practice. In patients with preexisting risk factors for sudden death, an implantable cardioverter–defibrillator may be placed before septal ablation.
Other complications of the procedure are remote myocardial infarction caused by aberrant ethanol injection14 or collateral circulation50 and ventricular septal rupture.19 Because of the latter potential complication, septal ablation should not be performed if septal thickness at the site of planned ethanol delivery is <15 mm.
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Comparison of Septal Ablation and Septal Myectomy
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There have been no prospective randomized trials comparing septal
ablation with septal myectomy. Investigators have compared the
results of septal ablation with those of septal myectomy in
several nonrandomized studies (
Table 4).
49,51–53 In none
of these retrospective studies have patients been adequately
matched for age, gender, and other clinical predictors of outcome
in HOCM.
In an institution at which both procedures were regularly performed, patients were triaged according to clinical factors, so the groups were not comparable.49 In particular, the 25 patients undergoing septal ablation were older and had a higher prevalence of comorbid conditions than did the 26 patients undergoing myectomy. At the 3-month follow-up, the gradient reduction was more complete in the surgical cohort, whereas the 2 groups had similar reductions in symptoms, septal thickness, and degree of mitral regurgitation. No deaths occurred in either group.
In the second study from 2 hospitals that each favored 1 of the procedures, patients were triaged according to institutional preference.51 In this study, it was possible to match patients for age and LVOT gradient. Forty-one patients were included in each group. At the 1-year follow-up, severity of symptoms, maximal oxygen uptake, LVOT gradient, septal thickness, and degree of mitral regurgitation were similar for the 2 therapies. There was 1 death during septal ablation as a result of coronary dissection.
A third study compared the effects of septal ablation in 20 patients with those of septal myectomy in 24 patients.53 Patients who underwent myectomy were younger than those who had ablation. There was 1 death in each group. Although improvements in LVOT gradient and New York Heart Association (NYHA) class were similar in the 2 groups, the increase in maximal oxygen uptake was higher in the patients who underwent surgery.
In a fourth study, patients were triaged to ablation or surgery on the basis of age and other clinical factors.53 The outcomes of 54 patients undergoing septal ablation were compared with those of 48 patients undergoing septal myectomy. Relief of symptoms was more complete in the surgical group. More late deaths occurred in the ablation group.
A comparison of echocardiographic indexes of diastolic function an average of 5 months after intervention demonstrated no difference between septal ablation and septal myectomy.54
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Which Patients Are Candidates for Mechanical Therapy for HOCM?
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Mechanical therapy is appropriate for patients with HOCM who
have symptoms (exertional dyspnea, angina, and/or "hemodynamic"
syncope) that interfere significantly with lifestyle and are
refractory to optimal medical therapy. The clinical threshold
for performing septal ablation should be identical to that for
performing septal myectomy.
Optimal therapy consists of β-blockade titrated to symptom relief, heart rate, or an adverse reaction. In patients with substantial symptoms despite optimal β-blockade, disopyramide, starting as 150 mg BID in the controlled-release form, may be added. Although disopyramide administration is sometimes limited by QT prolongation, a retrospective multicenter study provides some evidence against a proarrhythmic effect of the drug in patients with HOCM.55 In patients with noncardiac side effects of β-blockade, verapamil usually is substituted.
In patients without resting LVOT gradients of at least 30 to 50 mm Hg, exercise may bring out a provocable gradient. Patients with obstruction at rest or during exercise are candidates for mechanical therapy if they have symptoms that interfere substantially with their lifestyles despite truly optimal medical therapy. Published guidelines suggest that patients undergoing mechanical therapy should be in NYHA class III or IV.56 Because patients in NYHA class II have, by definition, symptoms during ordinary physical activity,57 some of these patients also are appropriate candidates for either septal ablation or septal myectomy. Patients in class II are, in fact, often managed with either septal ablation36,37,51,53 or septal myectomy.20–22,24–26,51,53 On the other hand, some patients in NYHA class III choose to live with their symptoms rather than undergo interventional or surgical management.
Retrospective studies have suggested that prognosis in HCM is related to the presence of a resting LVOT gradient58 and that prognosis in HOCM is favorably affected by septal myectomy.23 In the absence of conclusive prospective data to indicate that reducing or abolishing the gradient improves prognosis, however, mechanical therapy should not be offered to patients, even those with large gradients, if they have no or mild symptoms.
In some cases, HOCM is associated with intrinsic abnormalities of the mitral valve. These and other patients who require concomitant valve surgery or coronary bypass grafting should undergo septal myectomy rather than septal ablation. Surgery also should be considered for patients with atrial fibrillation who might benefit from a concomitant maze procedure.
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Advantages of Septal Myectomy
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- The success rate for septal myectomy is higher than that for septal ablation. This difference results in part from the dependence of the septal ablation procedure on the vagaries of septal anatomy.
- Sustained relief of outflow obstruction occurs immediately after septal myectomy but may be delayed by up to 3 months after septal ablation.
- Longer-term data are available for septal myectomy than for septal ablation, a consideration of particular relevance to the management of younger patients.
- Although both septal myectomy after failed septal ablation and septal ablation after failed septal myectomy have been carried out successfully, the former is more common. Because septal ablation often causes right bundle-branch block and septal myectomy often causes left bundle-branch block, patients undergoing the 2 procedures in sequence incur a very high risk of complete heart block, necessitating permanent pacing. A younger patient may therefore be better served by the strategy of primary septal myectomy to avoid the prospect of decades of permanent pacing.
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Advantages of Septal Ablation
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- Septal ablation has the potential for greater patient satisfaction because of absence of a surgical incision and need for general anesthesia, the lower amount of pain, and the much shorter recovery time.
- The benefit of alcohol septal ablation in older patients is similar to that in younger patients.36,59 Because the risks of cardiac surgery, particularly stroke, increase with age, ablation may offer an advantage in older patients.
- The cost of septal ablation is less than that of septal myectomy.
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What We Do Not Know
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- No randomized trials have been conducted on septal ablation versus septal myectomy.
- Conclusive data on the effect of either septal ablation or septal myectomy on life expectancy are not available.
- Although it is clear that life-threatening ventricular tachyarrhythmias after septal ablation are rare, they have been reported in sporadic cases. In the absence of definitive data, a reasonable strategy is to consider septal ablation a potential risk factor for sudden death. A corollary is that patients with preexisting risk factors (recurrent syncope, family history of sudden death in association with HCM, ventricular tachycardia, severe hypertrophy, or abnormal blood pressure response to exercise) should be considered for implantation of a cardioverter–defibrillator before septal ablation.
- The first septal ablation was performed in 1994; thus, long-term follow-up data in substantial numbers of patients are not available.
- Studies comparing the cost-effectiveness of septal ablation and septal myectomy have not been done.
- It is not known whether the outcomes of septal ablation and septal myectomy described at high-volume centers can be reproduced at other institutions.
Thus, although some have expressed strong, well-reasoned opinions in support of either septal ablation60 or septal myectomy61 as the procedure of choice, existing data are inconclusive, so the management decision in many cases depends critically on patient choice.
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Application to Patient Care
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Triage of patients to septal ablation or septal myectomy is
illustrated by the following recent real-life cases from Massachusetts
General Hospital.
Case 1: A 43-year–old man had exertional dyspnea and angina despite β-blockade. Septal thickness was 16 mm, and LVOT gradient 72 mm Hg. On the combination of a β-blocker and disopyramide, his symptoms remitted.
Case 2: A 61-year–old man had severe lightheadedness and exertional dyspnea despite optimal medical therapy in association with HOCM and pulmonary fibrosis. Septal thickness was 22 mm, and LVOT gradient 116 mm Hg. Because of his pulmonary disease, the patient underwent septal ablation.
Case 3: A 27-year–old man had presyncope and progressive exertional angina and dyspnea despite optimal medical therapy. Septal thickness was 26 mm, and LVOT gradient 184 mm Hg. His symptoms were refractory to medical therapy. Because of his young age and marked hypertrophy, the patient underwent septal myectomy.
Case 4: A 73-year–old woman had severe bisided heart failure in association with HOCM and chronic obstructive pulmonary disease. Septal thickness was 24 mm, and LVOT gradient 121 mm Hg. Diuresis was limited by hypotension and azotemia. Because she was in need of immediate relief of outflow obstruction and despite her concomitant pulmonary disease, the patient underwent septal myectomy.
Case 5: A 46-year–old woman had disabling angina, dyspnea, and lightheadedness despite optimal medical therapy. Septal thickness was 19 mm, and LVOT gradient 121 mm Hg. Both mechanical options—septal ablation and septal myectomy—were offered to the patient.
For patients like the last one, clinical decision making is not informed by clear-cut data demonstrating that either septal ablation or septal myectomy is superior. For such "gray-area" patients, the principle of patient autonomy dictates that it is appropriate for the properly informed patient to choose between the 2 procedures.
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What to Tell Patients
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Patients’ decisions depend critically on the information
given to them by their physicians and the manner in which it
is presented. To enable the patient to make what for him or
her is the best decision, the physician must present a thorough
and objective comparison of the 2 procedures. The physician
must recognize that local outcomes for either septal ablation
or septal myectomy may not match those from high-volume centers.
For example, the incidence of heart block for which permanent
pacing is indicated may be higher for both procedures than that
reported from a few select centers. All percentage estimates
should be modified accordingly. Representative considerations
to communicate to patients are the following:
- The medium-term success rate for septal myectomy (90% to 95%) is higher than that for septal ablation (80% to 90%).
- Clinical benefit is realized immediately after recovery from septal myectomy but may be delayed for up to 3 months after septal ablation.
- Neither the long-term success rate for septal ablation nor the long-term consequences of the septal ablation scar is known.
- The mortality rates of the 2 procedures (in otherwise healthy patients) are comparable (1% to 2%).
- The chance of needing a permanent pacemaker is much higher after septal ablation (10% to 15%) than after septal myectomy (5%).
- Although it is possible to have septal myectomy after failed septal ablation, the likelihood of needing a permanent pacemaker is extremely high after that sequence.
- In older patients, the chance of having a stroke is lower with septal ablation than with septal myectomy.
- The recovery time after septal myectomy is much longer than that after septal ablation.
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What Patients Will Choose
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Cardiologists and their patients are confronted by the choice
between percutaneous transcatheter and surgical therapies much
more often in coronary artery disease than in HOCM. In the setting
of coronary artery disease, most, but not all, patients for
whom either procedure would be appropriate choose percutaneous
coronary intervention over coronary artery bypass grafting.
The choice appears to be motivated by substantial value placed
by the patient in the avoidance of the incision, general anesthesia,
pain, and/or long recovery associated with surgery. These factors
also have engendered extension of nonsurgical interventional
procedures to the management of congenital and valvular cardiac
lesions.
Similarly, and for the same reasons, most gray-area patients with HOCM choose septal ablation over septal myectomy. Patients are of course influenced by the information presented to them by physicians. It is important to emphasize that not all patients fall into the gray area; as illustrated above by the case examples, many patients exist for whom the cardiologist should direct the management to either septal ablation or septal myectomy. It is also critical that gray-area patients be allowed to choose between the options in an unhurried, unpressured environment and to seek counsel from family, friends, other patients with HCM, and other physicians.
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Conclusions
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Longer-term follow-up will permit judgment on the durability
of the medium-term amelioration of LVOT gradient and improvement
in symptoms observed in most patients after septal ablation.
No data exist to support extending the current indications for
mechanical management of HOCM to patients with only mild symptoms.
If cardiologists adhere to strict inclusion criteria for septal
ablation and septal myectomy, with either procedure performed
only in patients with symptoms that interfere substantially
with their lifestyles and are refractory to truly optimal (usually
2-drug) medical therapy, few centers offering the procedures
are likely to maintain reasonable minimum case volumes. Operators
performing the procedures at lower rates may have lower success
and higher complication rates. Accordingly, performance of both
septal ablation and septal myectomy should be confined to regional
referral centers. The mechanical procedures should be offered
only in the context of a program that integrates expertise in
all aspects of HCM, including genetic counseling and arrhythmia
management.
Future comparisons of the results of septal ablation and septal myectomy would be aided by adoption of a standard definition of success of the procedures. One possible definition would be improvement by 
1 NYHA or Canadian Cardiovascular Society class and gradient reduction by 50% at 3 months after the procedure. Clinical equipoise would allow performance of a multicenter randomized trial comparing septal ablation and septal myectomy.62,63 Because mortality is low after both procedures, selection of a primary end point such as exercise capacity is advisable.
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Acknowledgments
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The author thanks Drs Igor F. Palacios, Michael H. Picard, and
Gus J. Vlahakes for critically reviewing the manuscript.
Disclosures
Dr Fifer has received honoraria for speaking on HCM in general and on septal ablation in particular.
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Introduction
Management of HCM