Sequential Use of Alcohol Septal Ablation and Electrosurgical Leaflet Resection Prior to Transcatheter Mitral Valve Replacement

Abstract: In patients with increased surgical risk and hemodynamically significant mitral disease, a transcatheter strategy for mitral valve replacement (TMVR) may be suitable; however, is also not without procedure risk. Obstruction of the left ventricular outflow tract (LVOT) is one of the most dreaded complications of TMVR, requiring careful consideration of potential candidates with preprocedural imaging and ex vivo valvular fit simulation as part of risk assessment for postprocedure obstruction. In patients at high risk of LVOT obstruction, early studies have shown that alcohol septal ablation or electrosurgical laceration of the anterior mitral leaflet (LAMPOON) procedure prior to TMVR may mitigate the risk of LVOT obstruction. We describe the recent successful management of a patient with severe mitral valve disease, mitral annular calcification (MAC), and high risk of post-TMVR LVOT obstruction, who underwent a sequential strategy of ASA followed by electrosurgical leaflet resection with the LAMPOON procedure prior to TMVR to successfully prevent LVOT obstruction. To our knowledge, this is the first time this dual strategy has been reported, and it may allow more patients with severe mitral valve disease to undergo TMVR in the future.

Key words: left ventricular outflow tract, LAMPOON, LVOT obstruction, mitral valve disease, TMVR

In patients with severe mitral annular calcification (MAC) and valvular dysfunction, transcatheter mitral valve replacement (TMVR) may be an option for patients of prohibitive surgical risk. Despite the growing use TMVR, Left ventricular outflow tract (LVOT) obstruction remains a life-threatening complication of this procedure. Preprocedural risk modeling with computed tomography (CT) imaging that includes a predicted neo-LVOT is effective in determining those at high or prohibitive risk of LVOT obstruction after TMVR.^1,2 However, no consensus currently exists regarding preprocedural therapy to minimize risk. In some patients with favorable anatomy, early studies have shown that use of alcohol septal ablation (ASA) prior to TMVR may lead to sufficient anatomical remodeling to reduce risk of LVOT obstruction.^2,3 However, a waiting period of at least 4 weeks is required before TMVR can be performed. Recently, Khan et al⁴ published an electrosurgical approach for prevention of postimplant LVOT obstruction, involving modification of a surgical approach that involves transection of the anterior leaflet immediately before TMVR to prevent iatrogenic LVOT obstruction. We describe here a recent patient with prohibitive risk of LVOT obstruction, as well as debilitating symptoms from severe MAC and mitral valve dysfunction, who required both ASA and subsequent electrosurgical transection of the anterior leaflet to further reduce risk of LVOT obstruction after TMVR. In patients with residual prohibitive or high risk of LVOT obstruction after ASA, this dual approach of ASA with electrosurgical resection may allow more patients to undergo TMVR.

Case Presentation

A 72-year-old female with history of non-obstructive coronary artery disease, hypertension, restrictive lung disease, and end-stage renal disease requiring hemodialysis was referred to our Structural Heart Clinic for symptomatic mitral stenosis. Her echocardiogram showed an ejection fraction (EF) of 65%, a small left ventricle (LV) with thickened interventricular septum (IVS), and severe mitral stenosis with MAC. Subsequent transesophageal echocardiography (TEE) showed a heavily calcified and fixed posterior mitral leaflet with a moderately calcified anterior leaflet that extended into the LVOT. With a preoperative STS mortality score of 7.8%, frailty, and significant medical comorbidities, the patient was determined to be at prohibitively high surgical risk, and alternative catheter-based therapy was pursued. TMVR in the MAC was deemed the best option.

Preprocedural evaluation to determine optimal valve sizing and determination of neo-LVOT was performed with cardiac CT, which employed specialized multiplanar reconstruction, maximum intensity projections, and advanced 3D offline postprocessing (Figure 1). The MAC was asymmetric, with sparing of the lateral aspect of the annulus, severe posterior calcification, and moderate anterior calcification extending to the LVOT side of the annulus, as well as accompanying severe mitral stenosis (Figure 1A). Measurements of the mitral annulus included the short- and long-axis distances (31.9 mm and 24.8 mm, respectively), cross-sectional area (6.01 cm³), average diameter (27.7 mm), and perimeter (89.3 mm) (Figure 1B), and determination of the annular plane in short-axis view (Figures 1C and 1D). The predicted changes of the LVOT were also measured (Figure 1E) with the neo-LVOT between the septum, and the proposed 26 mm Edwards Sapien prosthesis (Edwards Lifesciences) revealed cross-sectional area of 73.3 mm² at 40% R-R interval and with 50/50 valve deployment in the MAC (Figure 1F).

Further evaluation by CT showed a basal septal thickness of 1.1 cm. Given this, the patient was felt to be at prohibitive risk of LVOT obstruction should TMVR proceed without first attempting ASA, with planned intentional percutaneous laceration of the anterior mitral leaflet to prevent outflow obstruction (LAMPOON) technique for electrosurgical laceration of the anterior leaflet immediately prior to TMVR if LVOT obstruction risk remained high.

Approximately 4 weeks later, the patient underwent successful ASA of the first septal perforator, with 0.9 mL of 98% ethanol (EtOH), which she tolerated without complication (Figures 2A and 2B). Postprocedure transthoracic echocardiography showed no observable reduction in the patient’s LVEF, no wall-motion abnormalities, and no pericardial effusions after the administration of EtOH to the septal myocardium. Severe calcification of the mitral valve annulus was again seen, with mitral valve stenosis and mean pressure gradient of 12 mm Hg. Mitral valve area was calculated at 1.3 cm² by pressure half-time method. On outpatient follow-up 60 days later, the patient underwent repeat cardiac CT, which revealed no dynamic LVOT obstruction at rest, and a maximum basal septal wall thickness of 0.9 cm. Advanced 3D postprocessing was again employed to assess the mitral valve anatomy post ASA (Figures 2C and 2D). Neo-LVOT with a proposed 26 mm Edwards Sapien valve was calculated to be 132.0 mm², still placing the patient at high risk for LVOT obstruction following TMVR. The decision was then made to proceed with electrosurgical laceration of the anterior leaflet immediately before TMVR.

Methods

Image acquisition and processing. All cardiac CT images were acquired in house, as part of a multidisciplinary preprocedure evaluation or as part of follow-up anatomical assessments. Advanced postprocessing included multiplanar reconstruction, maximum intensity projection, and 3D processing, and was performed with the use of TeraRecon software.

Procedural details

(1) ASA for reduction of expected LVOT obstruction in advance of TMVR. The patient was brought in a fasting state to the cardiac catheterization laboratory. Standard prep was performed, with topical anesthetic and intravenous sedation given. Access was gained via Seldinger technique using ultrasound guidance without complication. The first septal perforator was identified and wired, with a 2.0 x 6 mm balloon placed and inflated to 8 atm. Contrast was then injected down the left anterior descending (LAD) coronary artery to ensure good flow, with the balloon inflated in the septal perforator. The coronary wire was then removed and contrast was injected via the balloon; the first septal perforator was seen, with no backflow down LAD and no collaterals to other branches. Bedside echocardiography was used to confirm that the upper septum only was supplied by the perforator branch. An infusion of 0.9 mL of 98% EtOH was then given over 1 minute, with 10 total minutes of dwell time. Angiography of the LAD was performed to confirm adequate LAD flow during the period of alcohol dwell time. The balloon catheter was then flushed, aspirated, and removed. Following ablation, the LAD was again determined to be patent with first septal with anticipated cutoff. Final angiography revealed occlusion in the first septal, and the procedure was considered a success. The patient recovered overnight in the cardiac intensive care unit, and was discharged home on postprocedure day 2.

(2) LAMPOON technique of electrosurgical laceration of the anterior leaflet. A waiting period of approximately 8 weeks passed between the ASA procedure and planned electrosurgical laceration of the anterior leaflet and TMVR. At the time of the second procedure, access was obtained in the left femoral artery and vein without complication, and a temporary pacing wire was placed from the left femoral vein with adequate thresholds found. At the right femoral vein, an 8 Fr sheath was placed and then exchanged over a 0.032 wire for a transseptal sheath (Baylis Medical). Using a transseptal needle (Baylis Medical) and TEE guidance, transseptal puncture was performed and a ProTek pig wire was advanced to the left atrium (LA). A 14 Fr eSheath (Edwards Lifesciences) was advanced over the wire and an Agilis sheath (Abbott Cardiovascular) was then used to access the LV. A balloon-tipped catheter was subsequently advanced into the LV,  LVOT, and descending aorta. A 300 cm-long run-through catheter was then advanced through the transseptal system into the descending aorta. A gooseneck snare inside a JR 4 guide was advanced from the right femoral artery and the run-through catheter was snared and then externalized. A 6 Fr JL 3.5 catheter was advanced into the LA over the run-through wire and a three-headed snare was advanced into the LA through the JL 3.5 guide. A second JL 3.5 guide was advanced into the LV and aimed at the anterior leaflet. An Astato catheter (Asahi Intecc) inside a piggyback catheter was advanced through the LV JL guide. Two fluoroscopic views were then used to confirm the position of the catheter, and a single burn was passed through the wire and into the LV. This wire was snared and secured, and a flying V was created in the standard fashion and advanced to the anterior leaflet of the mitral valve and left in position (Figure 3A).

(3) TMVR for severe MAC. The 26 mm Sapien valve was prepped, and dilation of the septum with a 12 mm peripheral balloon was performed to allow passage of the valve over the ProTek pig wire. A 6 Fr pigtail catheter was brought through the Agilis sheath and then advanced across the prosthetic valve into the LV, taking care to avoid entrapment in the LAMPOON system. A Confida wire (Medtronic) was placed through the pigtail, with the pigtail catheter and the Agilis sheath subsequently removed over the wire. Baseline hemodynamics were noted at this time to be 20 mm Hg (LA) and 140/6 mm Hg (LV). The Sapien valve was then introduced (Figure 3B) while carefully visualizing the path from the sheath to the septum. At the septum, the catheter was flexed and the delivery catheter advanced to the mitral valve. The stent valve was then brought into position. After confirming that it was correctly positioned, the valve was deployed with rapid ventricular pacing (Figure 3C).

Postoperative TEE showed trivial mitral insufficiency with negligible paravalvular leak. Mean gradients were noted to be less than 2 mm Hg post procedure by TEE across the mitral valve. There was a gradient across the LVOT ranging from 23 to 35 mm Hg that appeared to be heart-rate dependent, and was well tolerated by the patient. Given this result, the procedure was considered successful. The stent-valve delivery system was removed over the wire, the large sheaths were removed, and hemostasis was confirmed.

(4) Postoperative recovery and 1-month follow-up. Several hours after transfer to the cardiac intensive care unit for postprocedure recovery, the patient was noted to have intermittent complete heart block, requiring placement of a dual-chamber pacemaker the following day. It is not clear whether this was due to TMVR or to the earlier septal ablation procedure. An echocardiogram was subsequently performed on postoperative day 3, and revealed an EF of 65%, and a well-seated Sapien 3 valve with no paravalvular leak. Mitral valve peak velocity was noted to be 1.4 m/s, peak gradient was 8 mm Hg, and mean gradient was 3 mm Hg. LVOT gradient was noted to be improved compared with the immediate postprocedure period, and now ranged from 11-19 mm Hg. The remainder of the patient’s recovery was uncomplicated, and she was discharged home on hospital day 4 with plans for 3 months of anticoagulation and indefinite use of aspirin. At her 30-day follow-up appointment, echocardiogram showed continued improvement (Table 1); the patient reported near-complete resolution of her shortness of breath and had returned to her normal daily activities.

Discussion

Few treatment options exist for high- to extreme-risk patients with severe MAC and symptomatic valve dysfunction. In patients considered too high risk for traditional surgical mitral valve replacement, a transcatheter approach may be a suitable option. However, procedural risks may be prohibitive.¹ Of those risks, obstruction of the LVOT from systolic anterior motion (SAM) of the valve^1-3 is associated with increased risk of mortality, and often presents in the immediate postimplant period.^1-3

LVOT obstruction risk stratification requires preprocedural cardiac CT imaging, which should always include an ex vivo virtual simulation of valvular fit.^2,3 Assessment of the LVOT cross-sectional area created between the myocardial septum and the simulated prosthesis (the “neo-LVOT”), has now become more common as TMVR becomes more widely employed.^3-5 Recent studies suggest that a neo-LVOT area of <2 cm² increases the risk of LVOT obstruction,⁴ with a recent retrospective study of 30 patients suggesting that a neo-LVOT of <1.894 cm² raises risk of postimplantation LVOT obstruction, and should prompt consideration of empiric ASA prior to TMVR, as long as the patient’s anatomy is favorable.⁵

Pre-emptive ASA in patients at high risk for LVOT obstruction. ASA had been used as a bail-out strategy for acute LVOT obstruction; however, mortality remained high despite rescue attempts. In 2019, a retrospective multicenter trial by Wang et al showed that pre-emptive ASA was associated with a significant increase in predicted neo-LVOT area before TMVR in 30 patients.⁵ However, ASA is not without its share of risks; in patients with a thin interventricular septum, this procedure may give limited results^2,5 or expose patients to risk of ventricular septal defects. Furthermore, this is not a viable strategy in those without septal perforators, or those with history of coronary artery bypass grafting or an occluded LAD.⁵ The risk of postablation complete heart block requiring permanent pacemaker can be as high as 25%.² In addition, the waiting time of at least 4 weeks between ablation and proceeding with TMVR may be problematic in patients with severe mitral valve disease and debilitating symptoms.^2,5 The results of ASA, especially in normal or thin septums, are variable. Few available studies have addressed the dilemma of residual high LVOT obstruction risk following preprocedural ASA, which led us to pursue an additional risk reduction strategy of electrosurgical leaflet laceration at the time of TMVR.

The LAMPOON procedure to prevent LVOT occlusion. The LAMPOON procedure was demonstrated to allow patients at prohibitive risk of LVOT obstruction to proceed successfully with TMVR in a recent feasibility trial⁴ that included 30 patients. The use of an electrosurgical approach for anterior leaflet resection immediately prior to TMVR was developed based upon pre-existing surgical techniques to prevent LVOT obstruction without disruption of the chordae.⁴ The adaptation of this technique to a transcatheter-based strategy was done using modified commercially available devices, although more clinical studies are needed to demonstrate feasibility and safety.^4,6 Other recent LAMPOON trials demonstrated a reduction in post-TMVR incidence of LVOT obstruction^4,6 and reduced mortality post procedure,^4,6 with findings applicable to patients with both native and annuloplasty valve anatomies.^3,4,6 Although still early in its use across transcatheter valve centers, LAMPOON holds promise as a viable preventative strategy as TMVR is more widely implemented, both in patients at prohibitive risk of LVOT obstruction and as an adjunct to other LVOT obstruction risk-reduction measures, such as ASA.

Conclusion

We report here a successful strategy of sequential use of ASA and LAMPOON procedure in a patient at prohibitive risk of LVOT obstruction with debilitating symptoms of mitral valve dysfunction. Patients who remain at exceedingly high risk of LVOT obstruction despite preprocedural ASA can potentially benefit from this sequential dual approach with the LAMPOON procedure.

From the Sentara Heart Hospital, Structural Heart Division, Norfolk, Virginia.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Mahoney is a consultant and proctor for Edwards Lifesciences and Medtronic. Dr Long reports no conflicts of interest regarding the content herein.

The authors report that patient consent was provided for publication of the images used herein.

Manuscript submitted October 21, 2019, provisional acceptance given October 30, 2019, final version accepted November 6, 2019.

Address for correspondence: Paul Mahoney, MD, Sentara Heart Hospital, Structural Heart Division Director, 600 Gresham Drive, Norfolk, VA 23507. Email: paul.mahoney.md@gmail.com

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