Alcohol Septal Ablation for Hypertrophic Obstructive Cardiomyopathy: Novel Application of the Cutting Balloon

Case Presentation. A 39-year-old female with chronic hypertension presented with a 1-year history of progressive dyspnea. Echocardiography 6 months prior to admission confirmed hypertrophic obstructive cardiomyopathy (HOCM), and high-dose beta-blocker therapy was initiated. On admission, she noted dyspnea on minimal exertion, including conversing rapidly, consistent with New York Heart Association (NYHA) Class III to IV symptoms. Physical examination was notable only for a dynamic systolic ejection murmur heard best at the left upper sternal border. An electrocardiogram revealed sinus bradycardia at 44 beats per minute and left ventricular hypertrophy. An echocardiogram confirmed HOCM with asymmetric septal hypertrophy, systolic anterior motion of the mitral valve (SAM), resultant moderate mitral regurgitation and a severe subaortic resting gradient of 100 mmHg. Catheterization revealed secondary pulmonary hypertension (PA systolic 55 mmHg, PVR 4 Woods Units), severe dynamic outflow tract obstruction (resting gradient 90 mmHg provocable to 220, Figure 3A), and normal coronary arteries. A large branching first septal perforator was identified as supplying the target myocardium. Hyperdynamic ventricular contraction, particularly of the septum, produced marked extrinsic compression of the septal artery during systole (Figure 1). A decision was made to proceed with alcohol septal ablation. After wiring the first perforator (1.5 mm diameter vessel) of the large septal artery, a Maverick 2.0 x 9.0 mm angioplasty balloon (Boston Scientific Corp., Natick, Massachusetts) was appropriately positioned and inflated. However, stable balloon position could not be maintained, despite multiple attempts, due to vigorous myocardial compression of the septum and resultant “watermelon-seeding” of the balloon proximally (Figure 2A). Longer (Maverick 2.0 x 12 mm) and slightly oversized (Quantum Maverick 2.25 x 12 mm) balloons were subsequently tried without success. In order to enhance balloon stability, a final attempt was made using a 2.25 x 10 mm over-the-wire Cutting Balloon (Boston Scientific). The Cutting Balloon was inflated to 3 atmospheres and contrast was injected via both the guide catheter and the balloon lumen to confirm position and stability over 5 minutes (Figure 2B). Four milliliters of ethanol were then infused in standard fashion, resulting in a finalresting gradient of 10 mmHg without provocable augmentation (Figure 3B). At 10 days post-procedure, an outpatient echocardiogram confirmed a resting gradient of 16 mmHg, with normalization of pulmonary pressures (PA systolic 26 mmHg). The patient reported marked improvement in dyspnea, consistent with NYHA Class I. Discussion Hypertrophic cardiomyopathy (HCM) is a complex genetic cardiac disease characterized by abnormal myocardial hypertrophy.¹ The interventricular septum is often disproportionately involved, resulting in systolic anterior motion of the mitral valve and significant dynamic obstruction of the left ventricular outflow tract (LVOT) in 25% of cases.² Patients refractory to medical treatment with beta-blockers, calcium channel blockers, and/or disopyramide often benefit from surgical myectomy or percutaneous transluminal septal myocardial ablation (PTSMA), with similar short-term outcomes.^3,4 In PTSMA, also known as alcohol septal ablation, an appropriately-sized over-the-wire angioplasty balloon selectively occludes the target septal perforator while ethanol is delivered via the central lumen. Precise balloon positioning and stability are required throughout the procedure. Remote myocardial infarction, typically of the distal anterior wall and apex, may occur due to reflux of ethanol past the balloon and down the left anterior descending artery (LAD), particularly if the balloon is not fully occlusive or migrates proximally (watermelon-seeding). In addition to facilitating ethanol reflux, proximal watermelon-seeding can cause direct, albeit transient, obstruction to LAD flow, or dissection of the LAD at the takeoff of the septal artery. The Cutting Balloon was first designed and reported in 1991 and was subsequently approved as a treatment modality for coronary “high-pressure, balloon-resistant lesions,” including de novo lesions and in-stent restenosis.^5,6 It features three or four longitudinal atherotomes that create incisions in the plaque, facilitating dilation. A secondary benefit of the atherotomes is enhanced balloon stability due to increased friction between the balloon and the adjacent vessel, as demonstrated in the RESCUT trial.⁷ Despite initial concerns, the Cutting Balloon has proven to be safe, with no evidence for increased procedural complications, specifically coronary dissection and perforation.^8,9 The current case highlights a novel use of the over-the-wire Cutting Balloon to allow for successful septal ablation in patients with vigorous septal contractility and resultant proximal watermelon-seeding of standard balloons. Alternatives to the Cutting Balloon in this scenario might include use of a “buddy wire” and/or manual removal of the hydrophilic balloon coating.

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