Tip-to-Base LAMPOON for Transcatheter Mitral Valve Replacement With a Protected Mitral Annulus

Abstract

OBJECTIVES

The purpose of this study was to evaluate tip-to-base intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction (LAMPOON) in patients undergoing transcatheter mitral valve replacement (TMVR) in annuloplasty rings or surgical mitral valves.

BACKGROUND

LAMPOON is an effective adjunct to TMVR that prevents left ventricular outflow tract obstruction (LVOTO). Laceration is typically performed from the base to the tip of the anterior mitral leaflet. A modified laceration technique from leaflet tip to base may be effective in patients with a prosthesis that protects the aortomitral curtain.

METHODS

This is a multicenter, 21-patient, consecutive retrospective observational cohort. Patients underwent tip-to-base LAMPOON to prevent LVOTO and leaflet overhang, or therapeutically to lacerate a long anterior mitral leaflet risking or causing LVOTO. Outcomes were compared with findings from patients in the LAMPOON investigational device exemption trial with a prior mitral annuloplasty.

RESULTS

Twenty-one patients with a annuloplasty or valve prosthesis–protected mitral annulus underwent tip-to-base LAMPOON (19 preventive, 2 rescue). Leaflet laceration was successful in all and successfully prevented or treated LVOTO in all patients. No patients had significant LVOTO upon discharge. There were 2 cases of unintentional aortic valve injury (1 patient underwent emergency transcatheter aortic valve replacement and 1 patient underwent urgent surgical aortic valve replacement). In both cases, the patients had a supra-annular ring annuloplasty, and the retrograde aortic guiding catheter failed to insulate the guidewire lacerating surface from the aortic root. All patients survived to 30 days. Compared with classic retrograde LAMPOON, there was a trend toward shorter procedure time.

CONCLUSIONS

Tip-to-base laceration is a simple, effective, and safe LAMPOON variant applicable to patients with an appropriately positioned mitral annular ring or bioprosthetic valve. Operators should take care to insulate the lacerating surface from adjacent structures.

Left ventricular outflow tract (LVOT) obstruction is a life-threatening complication of transcatheter mitral valve replacement (TMVR) caused by displacement of the anterior mitral leaflet toward the interventricular septum (1-3). The incidence is highest following valve implantation in mitral annular calcification, but is sometimes observed following valve-in-ring or valve-in-valve procedures (4,5). Intentional laceration of the anterior mitral leaflet to prevent LVOT obstruction (LAMPOON) is a fully percutaneous transcatheter technique using off-the-shelf tools (1,6,7). In conventional retrograde LAMPOON and the newer antegrade LAMPOON techniques (8), the anterior leaflet is first traversed with an electrified wire and then sliced from base to tip. These approaches accomplish a midline immediately before TMVR.

If electrosurgical anterior leaflet laceration were instead performed from tip to base in native mitral valve disease, there would be a risk of catastrophic injury to the aortomitral curtain, aortic valve, and mitral annulus. However, patients with prior surgical mitral annuloplasty or valve devices may be protected against such injury. A tip-to-base approach to anterior mitral leaflet laceration has been described in patients as both a preventive (9) and rescue (bailout) strategy (10). We describe the procedural steps and clinical findings of 21 patients undergoing this technique. We also compared these findings with subjects having an annuloplasty-protected mitral annulus in the LAMPOON investigational device exemption (IDE) trial (1), which used the retrograde base-to-tip technique.

METHODS

CLASSIC RETROGRADE LAMPOON.

The classic retrograde base-to-tip LAMPOON, performed in the LAMPOON IDE trial (NCT03015194), has been previously described (1,6,11). The technique can be performed in patients with or without a protected mitral annulus. Two transfemoral Judkins left guiding catheters (Medtronic, Galway, Ireland) are advanced retrograde through the aortic valve and into the LVOT and left atrium. A stiff 0.014-inch guidewire (Astato XS 20, Asahi-Intecc, Aichi, Japan), insulated with a locking hubless microcatheter (Piggyback Wire Converter, Teleflex, Morrisville, North Carolina) is positioned at the base of the middle (A2) scallop of the anterior mitral leaflet and is electrified to traverse from the left ventricular side of the leaflet into the left atrium. A retrograde snare catheter is stabilized in the left atrium along a 0.014-inch guidewire rail that is externalized as an arteriovenous loop. After guidewire traversal of the mitral valve leaflet, the wire is snared in the left atrium and externalized to create a guidewire loop around the valve leaflet. The guidewire shaft is focally denuded in a “flying-V” configuration to facilitate leaflet laceration. Tension is applied to this lacerating system during electrification, by pulling the catheters retrograde toward the aortic valve, creating a midline laceration of the anterior mitral leaflet that is intrinsically aligned with the LVOT. A simpler antegrade technique has recently been described (8).

TIP-TO-BASE LAMPOON.

Tip-to-base LAMPOON relies on a prior mitral annuloplasty ring or valve to protect the mitral annulus from electrosurgical injury. When employed for “rescue,” the laceration is directed at anterior mitral leaflet tissue extending beyond the transcatheter valve frame. Two guiding catheters are connected via an atrial transseptal guidewire. The guidewire is exteriorized, kinked, and focally denuded to form the “flying-V,” and positioned at the tip of the anterior mitral leaflet. The 2 catheters will be used in tandem to lacerate the leaflet from tip to base during traction into the left atrium and aorta with simultaneous guidewire electrification. Laceration is complete when the guidewire reaches the base adjoining the previously placed mitral ring or valve.

Atrial transseptal crossing is performed in the standard fashion at the inferoposterior portion of the foramen ovale, in a position that is 3 to 4 cm from the mitral annular plane. A deflectable guiding sheath (such as Nagare [Terumo Interventional Systems, Tokyo, Japan] or Agilis [Abbott Vascular, Santa Clara, California]) is advanced into the left atrium.

Under transesophageal echocardiography (TEE) guidance, a balloon-wedge end-hole catheter is advanced through the deflectable guiding sheath and across the mitral valve. This catheter establishes a chord-free major orifice trajectory across the mitral valve, to allow free catheter movement and preserve chordal tension on lacerated leaflets. A support wire (Amplatz Extra-Stiff no, Cook Medical, Bloomington, Indiana) with an exaggerated curve may be placed in the catheter to help direct it toward the LVOT. Once positioned, it is advanced through the aortic valve. A 300-cm, stiff 0.014-inch guidewire (Astato XS 20) is advanced through the balloon-wedge end-hole catheter before it is ensnared (18/30 Atrieve, Argon Medical Devices, Frisco, Texas) in the ascending aorta. With the distal guidewire secured by the snare, the balloon-wedge end-hole catheter is removed and replaced with a 6-F Multipurpose or Judkins right 4 guiding catheter. The guidewire is insulated as usual with a hubless locking microcatheter (Piggyback Wire Converter) and attached to a standard electrosurgery generator (e.g., ValleyLab ForceFX/A, Galway, Ireland).

The middle of the 300-cm guidewire, which is still outside the body via the venous guiding catheter, is modified as previously described to create the flying-V electrosurgical lacerating surface (12). The proximal guidewire is insulated with a hubless locking microcatheter (Piggyback Wire Converter) and attached to a standard electrosurgery generator (e.g., ValleyLab ForceFX/A). Then, the flying V can be advanced with the microcatheter into the body via the venous guiding catheter (Medtronic, Galway, Ireland), while the arteriovenous loop is completed by externalizing the guidewire tip out the femoral artery via the aortic Judkins left 3.5 or JR4 guiding catheter (Figure 1).

FIGURE 1. Key Steps in Preventive Tip-to-Base LAMPOON.

(A) A transseptal guidewire is snared in the ascending aorta valve and externalized creating a venoarterial rail. (B) The flying-V lacerating system is positioned at the tip of the mitral valve. Note that the aortic guiding catheter is telescoped to the anterior mitral leaflet to minimize the risk of errant laceration. (C) Laceration is performed from the tip to the base of the mitral leaflet. The red lines indicate the electrified lacerating surface. Full laceration is achieved when the flying V contacts the protected mitral annulus. (D) Transcatheter mitral valve replacement is performed in the standard fashion. LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction.

The flying V is positioned at the tip of the anterior mitral leaflet (Figure 3) and aligned with both the midline of the target bioprosthetic or anterior mitral leaflet and with the aortic root. This alignment is typically confirmed in a left anterior oblique and caudal radiographic projection (Figure 2), and can be assisted with a catheter or prosthesis in the aortic root. TEE helps to assure midline position on the target A2 scallop. Proper alignment assures midline laceration, rather than less effective eccentric laceration (8).

FIGURE 3. Key Steps in “Rescue” Tip-to-Base LAMPOON.

(A) A balloon-wedge end-hole catheter is advanced through the mitral valve to facilitate guidewire advancement out of the aortic valve without chordal entrapment. (B) A guidewire is snared in the aortic root and externalized to create a venoarterial rail. (C) The flying V is advanced to the tip of the anterior mitral leaflet. Note that the aortic guiding catheter is telescoped into the left ventricular outflow tract to prevent inadvertent laceration of the aortic valve. (D) The flying V is electrified and tension is applied to lacerate the leaflet. The red line indicates the lacerating surface. The green outline represents the guidewire, blue represents the guiding catheters, and red represents the electrified lacerating surface. LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction.

FIGURE 2. Appropriate Guidewire Alignment.

The deflectable guiding catheter is used to position the lacerating system (red arrow) on the middle of the mitral leaflet prior to laceration. This is best confirmed in the left anterior oblique and caudal position.

Leaflet laceration is performed while infusing nonionic 5% dextrose into the guiding catheters (displacing blood to confine ablation energy to the leaflets and to prevent both coagulation and guidewire carbonization), electrifying the flying V at 70 W, and pulling the guiding catheters until the flying V abuts the protected mitral annulus. In rescue tip-to-base LAMPOON, the overhanging anterior mitral leaflet is lacerated from tip to the most ventricular aspect of the transcatheter heart valve struts, with the valve struts serving as a protective backstop. Linear slicing is confirmed by TEE, and the lacerating system is removed from the patient.

Following tip-to-base LAMPOON, TMVR is performed in the standard fashion (Video 1). The same steps are followed when performing tip-to-base LAMPOON as a rescue (bailout) strategy (Figure 3).

PATIENT SELECTION.

Cases were defined as high risk for LVOT obstruction (LVOTO) based on a neo-LVOT area of <200 mm² measured using time-resolved computed tomography (CT) or an anterior mitral leaflet length >2 cm (1). Briefly, using gated cardiac CT a virtual valve with the expected dimensions of the intended size transcatheter valve (SAPIEN 3, Edwards Lifesciences, Irvine, California), fully expanded, was modeled in the last systolic phase with the aortic valve fully open. The valve deployment is modeled at a 10% to 20% atrial and 80% to 90% ventricular position. A similar technique was used to confirm the skirt-neo-LVOT was >150 mm (12). The minimum LVOT area was determined by planimetry at end-systole, assuming no blood can traverse the SAPIEN-3 valve frame without leaflet laceration.

All patients with a “protected” mitral annulus (with a valve or annuloplasty device that was expected to prevent inadvertent injury to the aortomitral curtain), who were deemed to be at high risk for LVOTO, and who underwent attempted tip-to-base LAMPOON were included in this study. Each participating center’s Institutional Review Board approved this retrospective report and waiver of informed consent to share de-identified clinical data. The LAMPOON IDE trial was approved by each participating site’s Institutional Review Board.

DATA COLLECTION AND ANALYSIS.

Clinical, procedural, echocardiographic, and angiographic details were abstracted locally from the medical records of each patient’s index procedure. All endpoints were classified using the Mitral Valve Academic Research Consortium definitions (13).

Findings were compared with subject-level data collected from 15 subjects with a protected mitral annulus enrolled in the prospective LAMPOON IDE trial, a recent multicenter independently adjudicated assessment of the safety and effectiveness of the predicate retrograde LAMPOON technique and the same SAPIEN-3 TMVR.

Data are represented as number (percentage) or median (interquartile range [IQR]), as appropriate. Measures of statistical significance are not provided because of the small sample size.

RESULTS

PATIENTS.

Twenty-one consecutive patients underwent tip-to-base LAMPOON. All were deemed high or prohibitive risk for surgical mitral replacement. Baseline characteristics are shown in Table 1. Most were women with multiple comorbidities. The indication for TMVR was mitral stenosis in 7 patients, regurgitation in 9 patients, mixed in 4 patients, and unknown in 1 patient undergoing rescue LAMPOON. Ten patients had a prior surgical mitral ring, and 11 patients had a prior surgical bioprosthetic mitral valve replacement. Two patients underwent a rescue tip-to-base LAMPOON following valve-in-ring TMVR complicated by LVOTO. The 29-mm SAPIEN-3 valve was selected in 7 cases and a 26-mm SAPIEN-3 valve was selected in 13 cases. Images from a representative case of prophylactic and rescue tip-to-base LAMPOON are shown in Figures 1 and 2, respectively.

TABLE 1.

Baseline Subject Characteristics

	Tip-to-Base LAMPOON (n = 21)	Retrograde LAMPOON (n = 15)
Age, yrs	72 (62–82)	78 (50–85)
Female	17 (81)	8 (53)
End-organ failure
Home oxygen	8 (38)	4 (27)
End-stage kidney disease	0	2 (13)
Other comorbidities
Prior aortic valve replacement	6 (29)	1 (0.07)
NYHA functional class III or IV	21 (100)	14 (93)
2 or more prior cardiac surgeries	1 (5)	9 (60)
Moderate-to-severe pulmonary HTN	14 (49)	5 (33)
STS Predicted Risk of Mortality from mitral valve replacement, %	5.0 (3.3–14.1)	11.1 (5.9–15.8)
Ejection fraction, %	60 (48–65)	55 (47–65)
TMVR setting
Annuloplasty ring	10 (48)	15 (100)
Bioprosthetic mitral valve	11 (52)	0 (0)
LAMPOON setting
Preventive	19	15
Rescue	2	0
Baseline mean mitral valve gradient, mm Hg	11.0 (7.5–14.0)	8.4 (4.9–12.3)
Predicted neo-LVOT, mm2 (n/total having fixed LVOTO risk)	133 (72–150) (10/19)	96 (46–129) (11/15)
Predicted “skirt” neo-LVOT	279 (179–350)	240 (188–261)

Values are median (interquartile range) or n (%), unless otherwise indicated.

HTN = hypertension; LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction; LVOT, left ventricular outflow tract; LVOTO, left ventricular outflow tract obstruction; NYHA = New York Heart Association; STS = Society of Thoracic Surgeons; TMVR, transcatheter mitral valve replacement.

GEOMETRY.

Table 1 shows the geometry of the protected mitral annulus and LVOT by CT in the 21 patients who underwent preventive tip-to-base LAMPOON. Ten patients were at risk for a fixed LVOTO, defined as a neo-LVOT of ≤200 mm², and 11 patients were at risk of dynamic LVOTO associated with a long anterior mitral leaflet. Only 1 patient had a skirt-neo-LVOT ≤150 mm² requiring adjunctive septal debulking by transcoronary alcohol septal ablation in a separate session.

In contrast to with base-to-tip LAMPOON, in which image-guided basal laceration enforces midline laceration, tip-to-base LAMPOON does not entail basal leaflet traversal. Nevertheless, all patients had midline laceration, evident on TEE.

COMPLICATIONS.

There were 2 cases (both valve-in-ring) of inadvertent injury to the aortic valve caused by the electrified wire during laceration. Both caused severe aortic insufficiency immediately upon successful laceration of the anterior mitral leaflet. One case was treated with rapid initiation of extracorporeal membrane oxygenation followed by emergency implantation of a self-expanding transcatheter aortic valve. The second case was treated with urgent surgical aortic valve replacement the next day. Both patients survived to discharge.

In both cases, the retrograde aortic guiding catheter was insufficiently telescoped over the electrified guidewire and did not provide adequate protection of adjacent structures from the guidewire lacerating surface. In retrospect, there was also aggressive traction during electrosurgical tip-to-base laceration.

ADJUNCTIVE PROCEDURES.

Four cases used adjunctive procedures at operator discretion. In each case, elective intra-aortic balloon counterpulsation support was used to optimize hemodynamics prior to leaflet laceration, though there was not a predefined target blood pressure. In 2 of these cases, a percutaneous transthoracic left ventricular free wall (“apical”) TMVR-guidewire rail was created to enforce TMVR coaxiality during deployment. One case, described previously, required emergency extracorporeal membrane oxygenation. The remaining 20 cases did not exhibit significant hemodynamic compromise, require escalation of vasoactive medication support, or require unplanned mechanical circulatory support

OUTCOMES.

A total of 100% of patients underwent successful TMVR after tip-to-base LAMPOON without a significant LVOT gradient, using a single intended valve device, and survived the procedure. A total of 100% of patients survived to discharge and to 30 days.

Tip-to-base LAMPOON successfully prevented or treated LVOTO. In patients in whom tip-to-base LAMPON was used as a pre-emptive strategy, the median LVOT gradient at baseline was 2.5 mm Hg (IQR: 1.0 to 4.8 mm Hg) and 8.0 mm Hg (IQR: 1.3 to 2.8 mm Hg) after TMVR. One patient had an LVOT gradient increment >10 mm Hg (17 mm Hg), which was considered acceptable in the individual clinical context.

“Rescue” tip-to-base LAMPOON successfully treated LVOTO when applied in 2 patients. Before LAMPOON, 1 patient had hemolysis following TMVR (lactate dehydrogenase >1000 u/l, tea-colored urine, transfusion dependence) that resolved after rescue LAMPOON. In the other patient, tip-to-base LAMPOON reduced the resting LVOT gradient from 30 to 18 mm Hg and the post-premature ventricular contraction LVOT gradients from 96 and 47 mm Hg, respectively. Importantly, there was no evidence of transcatheter valve dysfunction following the “rescue” procedure. There were no strokes.

COMPARISON WITH CLASSIC LAMPOON.

Table 2 compares tip-to-base LAMPOON outcomes with those of subjects with prior ring annuloplasty in the LAMPOON IDE trial. Full lengthwise leaflet laceration was successful in all. No patients undergoing tip-to-base LAMPOON required bailout alcohol septal ablation, compared with 10% of subjects undergoing retrograde LAMPOON in the IDE trial. Cerebral embolic protection was not commercially available during the LAMPOON IDE trial, but was used in 6 patients undergoing tip-to-base LAMPOON. There were no clinically significant paravalvular leaks following TMVR in patients undergoing tip-to-base LAMPOON, compared with 3 subjects in the retrograde LAMPOON cohort. Transmitral gradients were comparable among groups upon discharge (4.2 ± 2.8 mm Hg for tip to base vs. 5.8 ± 2.3 mm Hg for retrograde).

TABLE 2.

Clinical Outcomes

	Tip-to-Base LAMPOON	Retrograde LAMPOON
Procedural outcomes
Successful laceration	21 (100)	15 (100)
Midline laceration	21 (100)	15 (100)
Successful deployment and correct positioning of TMVR	21 (100)	15 (100)
Successful access, delivery, and retrieval of LAMPOON system	21 (100)	15 (100)
Time from leaflet traversal to TMVR, min	13 (10–24)	18 (7–27)
Required “bail-out” alcohol septal ablation	0	3 (20)
Cardiac perforation	0	0 (0)
Required cardiac surgery or intervention within 30 days	2 (9.5)	1 (7)
Paravalvular leak greater mild	0	3 (20)
Procedural complications
Stroke	0 (0)	0 (0)
Major vascular complication	3 (14)	4 (27)
Echocardiographic outcomes
LVOT gradient
Baseline, mm Hg	2.5 (1.0–4.8)	1.4 (1.0–1.8)
Pre-discharge, mm Hg	8.0 (2.8–13.0)	4.1 (2.0–5.7)
LVOT gradient increase >10 mm Hg	1	0
Survival
Survived immediate procedure	21 (100)	15 (100)
Survived to 30 days	21 (100)	15 (100)

Values are n (%), median (interquartile range), or n.

Abbreviations as in Table 1.

Tip-to-base LAMPOON appeared faster than classic retrograde LAMPOON (13 min vs. 18 min) (Central Illustration).

CENTRAL ILLUSTRATION. Tip-to-Base LAMPOON Is a Simplified Approach to Lacerate the Anterior Mitral Leaflet.

A comparison of LAMPOON techniques. (A) Retrograde LAMPOON. (B) Tip-to-Base LAMPOON. LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction; MAC = mitral annular calcification; SMVR = surgical mitral valve replacement.

DISCUSSION

In the present study, we describe the procedure steps and clinical outcomes of 21 patients who underwent tip-to-base LAMPOON. The main findings of this study are: 1) tip-to-base LAMPOON was technically feasible in 100% of patients; 2) tip-to-base LAMPOON was 100% effective in preventing LVOTO in 19 patients otherwise deemed to be at prohibitive risk of surgical and transcatheter mitral valve replacement; 3) tip-to-base LAMPOON successfully treated LVOTO in 2 patients after TMVR; 4) 2 patients suffered iatrogenic aortic valve injury that in retrospect probably could have been avoided through technical modifications; and 5) there was 100% procedural survival and 100% survival to 30 days—similar to the LAMPOON IDE trial.

We believe that tip-to-base LAMPOON should not be attempted in patients with untreated native mitral annular calcification or noncircumferential surgical annuloplasty bands because of the risk of catastrophic injury to the aortomitral curtain. Surgical mitral implants that span the intertrigonal line form a protective barrier between the anterior mitral leaflet and the aortic root, and that allow safe “reverse” laceration from tip to base.

The relationship of the surgical valve posts to the LVOT is important. Surgical mitral valves are typically implanted with the posts either side of the LVOT. If a valve post is protruding into the LVOT, laceration is unlikely to be effective. The LAMPOON IDE trial used for comparison included subjects with prior mitral annuloplasty or mitral annular calcification but not prior surgical mitral valve replacement.

The tip-to-base LAMPOON technique represents a simplification of previously described LAMPOON technique for patients with an aortomitral curtain protected by a ring or valve (8). In earlier LAMPOON approaches, the base of the A2 scallop is traversed prior to laceration. The traversal step requires careful catheter positioning that can be technically challenging for the operator. Tip-to-base LAMPOON does not require leaflet traversal and thereby is a less technically demanding procedure. Midline leaflet laceration is performed by aligning the flying V on the target A2 scallop in the caudal left anterior oblique projection and by confirming alignment on simultaneous biplane TEE. The role of LAMPOON in implantation of dedicated TMVR devices is not established. Applicable TMVR devices must allow flow through the space created by anterior leaflet laceration. We have used LAMPOON to prevent dynamic LVOTO complicating compassionate Tendyne TMVR (14).

The numerically fewer post-TMVR alcohol septal ablations in this tip-to-base LAMPOON cohort is likely attributable to advancements in pre-procedural CT planning. Patients at risk of LVOT from the transcatheter valve skirt (12) can be identified and treated with preemptive septal modification in a separate procedure before TMVR. Tip-to-base LAMPOON also may allow for a more complete laceration. In classic retrograde LAMPOON, leaflet laceration is performed from the obtained traversal point to the leaflet tip. During tip-to-base LAMPOON, laceration to the basal most point of the leaflet is achieved with the surgical prosthesis serving as a stop guard. The lower incidence of clinically significant paravalvular leak is also likely attributable to advancements in TMVR technique and the selective use of a LV free wall rail to assure coaxiality during deployment.

Two major vascular complications in the tip-to-base cohort were attributable to errant aortic lacerations that were not associated with procedural mortality. These 2 cases of serious inadvertent aortic injury are likely related to early inexperience with this technique. Both appear to share 2 features. In both the supra-annular annuloplasty ring was sutured high into the aortomitral curtain. More important, the 2 guiding catheters were allowed to separate excessively during electrosurgical laceration, and therefore failed to insulate and protect the aortic root from bystander injury. This is a humbling reminder of the limitations of transcatheter electrosurgery, especially using current off-the-shelf technology. The authors recommend that new operators obtain training before undertaking such procedures. Dedicated laceration devices may decrease this risk. We recommend operators enforce close proximity of the 2 guiding catheters at all times during laceration, exposing a maximum of 2 mm of guidewire including the flying-V lacerating surface. It is therefore helpful to “take the slack” out of the aortic catheter before applying electrosurgical traction. We recommend applying the minimal necessary traction to the lacerating system to facilitate safe leaflet splitting. The third major vascular complication in this cohort was a femoral artery occlusion caused by a vascular closure device that resolved with balloon dilatation.

The risk of aortic injury can further be decreased by telescoping the aortic guiding catheter into the LVOT during guidewire exteriorization, exposing only minimal guidewire adjacent to the flying V, and carefully monitoring the position of the flying V to ensure that it remains on the A2 scallop during laceration. Importantly, there were no eccentric leaflet lacerations or damage to the mitral apparatus. Only 1 patient who did experience an errant laceration required escalation of mechanical circulatory support. All other patients remained hemodynamically stable following laceration allowing for methodical TMVR.

Transcoronary alcohol septal ablation is an alternate strategy to prevent and treat LVOTO. Although technically simple to perform, the technique requires an anatomically suitable septal perforator artery, which may not be present in all patients, and a “waiting period” to allow for septal reduction. In the largest reported series, alcohol septal ablation was associated with a 7% procedural mortality and 17% pacemaker rate (15). In that report, alcohol septal ablation enabled TMVR in only 50% of cases in which it was performed. By comparison, there were no deaths or conduction disturbances in our patient cohort, and the technique can be performed immediately prior to TMVR.

Unlike retrograde LAMPOON, tip-to-base LAMPOON can be used as both a preventive and rescue strategy. In this series, we describe 2 patients—without good treatment options—who were successfully treated with “rescue” tip-to-base LAMPOON more than a week following TMVR. Although the LVOT gradient was not fully abolished, both patients were discharged with a “tolerable” LVOT gradient, and 1 patient had complete resolution of hemolysis. The strategy may not be applicable to valve-in-valve TMVR, as surgical mitral bioprostheses have short leaflets unlikely to overhang and be accessible to LAMPOON. We recommend preventive, rather than rescue, tip-to-base LAMPOON when possible to allow for complete anterior leaflet laceration.

STUDY LIMITATIONS.

This is a retrospective, multicenter report of sites’ initial experience with tip-to-base LAMPOON. The small sample size precludes detecting important differences among LAMPOON approaches. The trends toward improved outcomes may reflect interval operator experience with transcatheter electrosurgery, even though the current series includes proctored (16) and initial site experience. Operators performing the technique should take care to avoid inadvertent injury to the aortic valve during wire exteriorization and laceration. A strength of this report is the availability of systematically adjudicated comparator data.

CONCLUSIONS

Tip-to-base LAMPOON is a simplified variant of classic retrograde LAMPOON. It appears effective and reproducible in preventing or treating LVOTO in patients with a annuloplasty ring or valve protecting the mitral annulus. We recommend that this approach be considered for patients undergoing TMVR with annuloplasty rings protecting the mitral annulus.

Supplementary Material

Supplemental video

Supplemental Video 1. Case demonstrations of key steps in tip-to-base LAMPOON and the “rescue” variant.

PERSPECTIVES.

WHAT IS KNOWN?

LAMPOON is an effective strategy to prevent LVOTO complicating TMVR. Base-to-tip LAMPOON, which requires leaflet traversal, is technically challenging for new operators.

WHAT IS NEW?

Tip-to-base LAMPOON laceration is a new strategy applicable to valve-in-ring TMVR or “rescue” for long anterior leaflet causing LVOTO after TMVR. Tip-to-base LAMPOON is less technically demanding than traditional base-to-tip LAMPOON. Tip-to-base LAMPOON requires meticulous attention to insulate the lacerating surface in order to avoid serious injury to the aortic valve

WHAT IS NEXT?

Dedicated devices may improve the safety of tip-to-base LAMPOON.

ABBREVIATIONS AND ACRONYMS

CT

computed tomography

IDE

investigational device exemption

IQR

interquartile range

LAMPOON

intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction

LVOT

left ventricular outflow tract

LVOTO

left ventricular outflow tract obstruction

TEE

transesophageal echocardiography

TMVR

transcatheter mitral valve replacement