The Importance of Atrial Pacing during Alcohol Septal Ablation

Case description. A 52-year-old female presented to us with shortness of breath with her daily activities despite optimal medical therapy. An echocardiogram revealed hypertrophic cardiomyopathy with severe dynamic outflow tract obstruction. She was given the options of myectomy and alcohol septal ablation and she chose the latter. On catheterization, a pigtail at the LV apex and a catheter in the aorta revealed a gradient of 235 mmHg (Figure 1, note 400 scale) and a systolic blood pressure of 85 mmHg. As alcohol septal ablation can be complicated by complete heart block, a backup temporary pacemaker was placed in the right ventricular (RV) apex. Pacing from the RV lead dropped her aortic pressure to 60 mmHg (Figure 2A). To maintain the left atrial contribution to left ventricular (LV) filling an atrial lead was positioned and the AV delay was optimized such that RV pacing followed RA pacing. Aortic systolic pressure increased to 85 mmHg with symptomatic improvement (Figure 2B). Subsequently using magnetic navigation (Stereotaxis, St. Louis, Missouri), a proximal septal was wired and a 2.5 mm x 6 mm Sprinter over-the-wire coronary balloon (Medtronic, Minneapolis, Minnesota) was advanced over the guidewire into the proximal end of the target septal perforator branch and was inflated to occlude the septal vessel. The guidewire was then removed and agitated contrast was injected through the central lumen of the balloon. Following contrast injection, transthoracic echocardiography identified the potential infarct area. A total of 2 mL of 98% dehydrated alcohol was injected via the Sprinter balloon over 3 minutes. Then, the occluding balloon catheter was deflated and removed. Hemodynamic monitoring showed that the dynamic gradient was reduced to 15 mmHg (Figure 2C). The technique of alcohol septal ablation has been described previously1 along with its favorable long-term effects on outflow tract obstruction, symptoms and exercise tolerance.2 Despite refinements in the technique of the procedure,3,4 transient AV block is not uncommon. While most patients can have stable hemodynamics with RV pacing only, patients with severe diastolic dysfunction are heavily dependent on the atrial contribution to LV filling. These patients develop a marked drop in LV stroke volume when AV synchrony is not maintained, as illustrated in this case. In such situations an atrial lead should be placed prior to the alcohol septal ablation. The case and the hemodynamic tracings illustrate the important role atrial pacing can have during alcohol septal ablation in specific HCM patients.

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From Methodist DeBakey Heart and Vascular Center, The Methodist Hospital, Houston, Texas. The authors report no conflicts of interest regarding the content herein. Manuscript submitted July 13, 2009, provisional acceptance given August 10, 2009, final version accepted September 24, 2009. Address for correspondence: John M. Buergler, MD, FACC, Methodist DeBakey Cardiology Associates, 6550 Fannin, Suite 1901, Houston, TX 77030. E-mail: jbuergler@tmhs.org

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References

1. Sigwart U. Non-surgical myocardial reduction for hypertrophic obstructive cardiomyopathy. Lancet 1995;346:211–214. 2. Fernandes VL, Nagueh SF, Wang W, et al. A prospective follow-up of alcohol septal ablation for symptomatic hypertrophic obstructive cardiomyopathy — The Baylor experience (1996–2002). Clin Cardio 2005;28:124–130. 3. Buergler JM, Alam S, Spencer W, et al. Initial experience with alcohol septal ablation using a novel magnetic navigation system. J Interv Cardiol 2007;20:559–563. 4. Soon CY, Buergler JM. Alcohol septal ablation and the Brockenbrough-Braunwald