Case Report and Brief Review

Alcohol Septal Ablation for Symptomatic Hypertrophic Obstructive Cardiomyopathy in Patients with Prior Coronary Revascularization

Rami N. Khouzam, MD and Srihari S. Naidu, MD

Rami N. Khouzam, MD and Srihari S. Naidu, MD

ABSTRACT: Alcohol septal ablation has become an acceptable alternative to surgical myectomy in patients with hypertrophic obstructive cardiomyopathy who remain significantly symptomatic after optimized medical management and meet strict anatomic criteria. Given the prevalence of coronary artery disease and the variable phenotypic penetrance and age at first diagnosis of hypertrophic cardiomyopathy (HCM), patients may undergo coronary revascularization before a firm diagnosis of HCM is made. Patients with prior revascularization in the form of percutaneous coronary intervention or coronary artery bypass grafting pose unique challenges when contemplating and performing alcohol septal ablation. We present two cases of alcohol septal ablation after prior coronary revascularization, and discuss relevant concerns regarding patient selection, procedural technique and consequent durability of clinical outcome.
J INVASIVE CARDIOL 2010;22:E220–E224
Key words: reduction, stent, bypass
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Case Reports

Patient #1. A 67-year-old male presented with history of dyslipidemia, tobacco use and coronary artery disease with stent placement spanning the proximal and mid left anterior descending (LAD) coronary artery in 2003. Three years after stent placement, due to persistent exertional angina and dyspnea, and despite patent coronary arteries, he underwent reevaluation and was subsequently diagnosed with hypertrophic cardiomyopathy. Once the diagnosis was made, augmented doses of beta-blocker and calcium-channel blocker therapy were instituted with minimal effect, and the patient remained in New York Heart Association (NYHA) and Canadian Cardiovascular Society (CCS) Angina Class III. Echocardiogram revealed ejection fraction of 65–70%, basal septal hypertrophy of 2.3 cm, and systolic anterior motion (SAM) of the anterior mitral valve leaflet with dynamic left ventricular outflow tract obstructive physiology. A cardiac catheterization was performed, confirming hypertrophic obstructive cardiomyopathy physiology; specifically, there was no resting gradient but provokable gradient to 160 mmHg (Figure 1). Angiography showed a patent stent in the proximal to mid LAD, with multiple septal perforators. Of note, the first septal perforators arose proximal to the stent, while the second perforator was covered, albeit still patent, by the stent (Figure 2). Under fluoroscopic and myocardial contrast echocardiographic guidance (Figure 3), the septal perforator prior to the LAD stent was found to be supplying the intended target, and 3 ml of 98% ethanol were infused without complication. After ablation, there continued to be 100 mmHg gradient with provocation (Figure 4). As a 50% or greater reduction in peak gradient is typically desired, the second more distal septal perforator was wired, but not amenable to passage of a 1.5 mm balloon through the prior stent strut, despite use of different wires. Continued attempts to achieve > 50% gradient reduction were therefore aborted. Echocardiogram at 6 months showed a resting gradient of 40 mmHg and provokable gradient of 80 mmHg, with basal septum thickness decreased to 2.0 cm. Clinically, despite partially successful alcohol septal ablation (inability to achieve 50% or greater reduction in gradient at the time of procedure), symptoms improved to NYHA Class II with increased exercise tolerance and elimination of angina on the identical medical regimen. Patient #2. A 56-year-old male presented with hypertension, hypothyroidism and coronary artery disease, manifested by coronary artery bypass graft (CABG) surgery 10 years prior. At that time, the patient received a left internal mammary artery to the LAD (LIMA-LAD) graft, a saphenous vein graft to the posterior descending artery (SVG-PDA) and a radial arterial graft to the first diagonal branch. Eight years after bypass, a diagnosis of hypertrophic cardiomyopathy (HCM) was made when the patient presented with frequent episodes of dizziness, syncope and chest pain, predominantly exertional. Despite optimal medical management in the form of beta-blocker and calcium-channel blocker therapy, as well as prophylactic implantable cardioverter-defibrillator (ICD), the patient remained in NYHA Class III with exertional lightheadedness. Echocardiogram showed moderate left ventricular hypertrophy (LVH), with basal septal diameter of 2.2 cm, SAM of the mitral valve, moderate posteriorly-directed mitral regurgitation and normal left ventricular size and function, with ejection fraction of 60–65%. A resting outflow tract gradient of 25 mmHg was noted. Cardiac catheterization performed to identify the etiology of dyspnea and syncope revealed two patent grafts (LIMA-LAD, SVG-PDA), but occluded radial-first diagonal graft, and total occlusion of all native coronaries. Of note, there was complete occlusion of the proximal-mid LAD at the takeoff of the first septal perforator (Figure 5). Hypertrophic obstructive cardiomyopathy physiology was demonstrated, with no resting gradient, but provokable gradient of 180 mmHg aftercombined Brockenbrough and Valsalva maneuvers. The previously mentioned first septal artery was of moderate caliber (2 mm diameter) and arose off the native LAD as previously described, but the second septal perforator was slightly larger (2.25 mm diameter), longer, and accessible in antegrade fashion via the LIMA (Figure 6). Multiple attempts to wire the first septal perforator were unsuccessful, despite use of hydrophilic wires. Angiographically, there was a severe lesion at the ostium of the first septal perforator, as an extension of the disease and total occlusion of the proximal-mid LAD. As a result, a decision was made to perform alcohol septal ablation in the proximal LAD itself. 5 ml of ethanol were infused to the proximal LAD without complication (Figure 7), after myocardial contrast echo confirmation. Repeat hemodynamics were performed, with the intention of proceeding to the second septal perforator via the LIMA if there was > 50% residual gradient, but revealed no resting or provokable gradients, indicating a successful procedure. A follow-up echocardiogram at 4 months confirmed no resting or provokable gradients, with basal septal thickness now 1.4 cm and resolution of SAM-related mitral regurgitation. The patient’s symptoms completely resolved. Discussion. Hypertrophic cardiomyopathy occurs in 1 out of every 500 individuals as the most common genetic cardiac defect. Due to variable phenotypic penetrance, heterogeneity of left ventricular thickening, differential age at presentation, and continued relatively low cardiovascular community awareness of the disease, a diagnosis of HCM may not be made until middle or late adulthood. Many patients are thus diagnosed with and treated for other more common cardiovascular disease processes, most notably coronary artery disease, before a formal diagnosis of HCM is made. In such patients, either HCM physiology was concomitantly present, yet underappreciated, at the time of coronary revascularization, or developed years after coronary revascularization as a new cause of recurrent cardiovascular symptoms. In either case, such patients pose unique challenges to the HCM specialist contemplating further invasive therapy. Four major approaches are available for treatment of obstructive HCM, including: 1) pharmacologic therapy; 2) dual chamber pacing; 3) surgical myectomy; and 4) nonsurgical septal reduction (alcohol septal ablation, coil embolization and radiofrequency ablation). The aim of medical therapy, which is successful in roughly half of all patients, is relief of left ventricular outflow tract obstruction and improvement in diastolic function. Cardiac dual-chamber pacing has been suggested as an alternate method of reducing outflow tract obstruction and improving symptoms after failure of medical therapy.1,2 However, results of randomized trials have diminished the enthusiasm for cardiac pacing as a primary therapy for HCM, except perhaps in those over age 65.3,4 For four decades, the “gold standard” for treating severe obstructive HCM has been ventricular septal myotomy-myomectomy, with relief of outflow tract obstruction and improvement in symptoms in 70–90% of individuals.5,6 The results of surgery from several quaternary centers in North America are excellent. In real world application, however, several subgroups of patients prove poor candidates for surgery, including those with advanced age, significant co-morbidity, and poor motivation or social support. Dr. Ulrich Sigwart first reported selective septal ablation utilizing the relevant septal perforator in 1995.7 Since then, alcohol ablation has been performed widely and successfully, with short- and intermediate-term clinical outcome comparable to surgery in appropriately selected patients.8 Alcohol septal ablation results in relief of symptoms in the majority of patients, low procedural and intermediate-term mortality, rapid recovery, and functional improvement that continues over a 2-year period, despite a slightly higher incidence of complete heart block requiring permanent pacemaker placement.8,9 Non-surgical septal myocardial reduction by coil embolization in HOCM has also been demonstrated in case reports and pilot studies to be feasible without inducing complete heart block. Larger studies, ideally randomized to contemporary alcohol septal ablation, are warranted.10,11 In young children, in whom alcohol-induced septal ablation is not an option, radiofrequency catheter ablation offers another alternative, with the benefits of repeatability and lower risk of procedure-related permanent atrioventricular block.12 In general, patients with known hypertrophic obstructive cardiomyopathy and significant multivessel coronary disease should undergo combined myectomy and coronary artery bypass surgery. However, when the diagnosis of HCM is made after coronary revascularization, as in our cases, the decision on which invasive therapy to pursue becomes more complex. For patients with prior PCI, the decision may ride on whether the prior PCI was successful and whether residual or progressive multi-vessel disease has occurred. If restenosis or significant progression of disease in multiple territories is seen, then a decision to perform CABG and concomitant myectomy should be made, as long as the patient remains a reasonable operative candidate. If the PCI was successful and there is no significant residual or progressive disease, however, such patients may consider the less-invasive alcohol septal ablation, especially if they have relative contraindications to myectomy, such as co-morbidity, advanced age or a strong personal preference for less invasive therapy. In patients with prior successful CABG, in contrast, a strategy of alcohol septal ablation first seems most reasonable, especially if a patent LIMA is present, as re-do sternotomy in such patients carries significant risk.13 Patients with prior revascularization pose unique challenges when undergoing alcohol septal ablation. There is surprisingly little to no literature on this topic. Indeed, different considerations come into play, depending on whether CABG or PCI was the initial strategy of revascularization, where the native coronary occlusions are located, and which septal perforators are accessible. For patients with prior PCI, alcohol septal ablation is only impacted when stent placement is placed overriding relevant septal perforators. In such cases, specific attention must be made to the number and location of septal perforators, and which ones have been jailed by the stent. Myocardial contrast echo takes on greater importance, in order to ascertain whether the perforators that are accessible (immediately prior to or distal to the stent) adequately subserve the target myocardium. If this is not the case, then wiring through previous stent struts may be attempted. However, as in our case, although wiring was possible, tracking a small-diameter balloon over the wire was not, resulting in termination of the procedure. Due to the 90 degree or greater angle with which septal perforators arise off of the LAD, and the inability in most cases to place a wire very distal in the septal perforators (due to their limited length), the presence of a prior stent makes balloon placement very difficult. In our first case, partially successful ablation (40% reduction in gradient as opposed to > 50%) was performed through a more proximal perforator that was not “jailed.” In these patients, it is reasonable to follow the patient clinically to see whether a significant improvement in clinical symptoms has occurred. Indeed, such “cut-offs” may not be absolute, as the clinical success in our patient illustrates. For those in whom severe symptoms persist, however, surgical myectomy may be performed if feasible. For those in whom surgical myectomy is contraindicated, septal ablation may be re-attempted using stronger back-up, more forceful dilation of stent struts, followed by alcohol septal ablation and repeat stent placement to the disrupted area if necessary. Patients with prior CABG are oftentimes poor candidates for re-do sternotomy and surgical myectomy, especially if a patent LIMA is present. In such patients, alcohol septal ablation should be the preferred invasive treatment. Two potential avenues to the proximal septal perforators are available in patients with prior LIMA to LAD anastomosis. In general, an antegrade approach is preferred through the native LAD, when feasible, as this is the normal route for alcohol septal ablation and avoids inadvertent damage to the all-important LIMA to LAD graft. Alcohol septal ablation through the LIMA, although not described in the literature, could theoretically also be performed. However, this might require complicated and dangerous wiring techniques down the LIMA, retrograde or antegrade in the LAD, and finally into the septal perforator. A short guide catheter should be considered in such cases, as well as highly trackable balloons. In our case, the first septal perforator could not be wired due to a near chronic total occlusion and severe tortuosity at the ostium of the first septal perforator. As a result, we opted to place the balloon catheter in the proximal LAD itself, knowing angiographically that all alcohol would enter the first septal perforator due to the more distal chronic total occlusion. After confirmation with myocardial contrast echocardiography, this resulted in complete objective and subjective success. Few case reports of patients undergoing simultaneous alcohol ablation and angioplasty of the LAD artery for significant coronary stenosis have been published.14,15 To our knowledge, this is the first case of alcohol septal ablation of the proximal LAD, with total occlusion of the mid-LAD preferentially directing alcohol into the first septal perforator, and resultant successful procedure. Conclusion. Alcohol septal ablation is feasible after prior coronary revascularization, including both PCI and CABG. However, unique cognitive and technical challenges exist that complicate the procedure, raise the risks, and potentially reduce chances of success. Myocardial contrast echocardiography, in particular, takes on far greater importance in such procedures. As a result, alcohol septal ablation procedures after prior coronary revascularization should only be performed by those highly experienced in alcohol septal ablation and myocardial contrast echocardiography, and only in the context of a comprehensive HCM program. Whether newer modalities of non-surgical septal reduction, such as coil embolization, will aid in such complex patient subsets remains to be seen.

References

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From the Department of Medicine, Division of Cardiology, Winthrop University Hospital, Mineola, New York. The authors report no conflicts of interest regarding the content herein. Manuscript submitted March 25, 2010, provisional acceptance given April 28, 2010, final version accepted May 3, 2010. Address for correspondence: Srihari S. Naidu, MD, FACC, FSCAI, Director, Cardiac Catheterization Laboratory, Winthrop University Hospital, 120 Mineola Blvd, Suite 500, Mineola, NY 11501. E-mail: ssnaidu@winthrop.org