Left Ventricular Outflow Tract Obstruction Following Transcatheter Mitral Valve Replacement Resolved by Chordal Rupture.

Transcatheter mitral valve replacement carries a risk of left ventricular outflow tract obstruction associated with mortality. We present a case of left ventricular outflow tract obstruction that resolved spontaneously when chords to the anterior mitral leaflet were found to have ruptured. (Level of Difficulty: Advanced.).

History of Presentation

An 83-year-old woman with severe mitral regurgitation was referred from an outside hospital for a possible transcatheter valve procedure. She had been denied cardiac surgery because of advanced age and increased surgical risk. She was symptomatic with heart failure, New York Heart Association (NYHA) functional class II. Medication included a beta-blocker, an angiotensin-converting enzyme inhibitor, and diuretic agents. On examination, there were no signs of cardiac decompensation. There was an apical systolic murmur grade 5/6, and her lung fields were clear. Her blood pressure was 100/70 mm Hg. She was in sinus rhythm, without a history of atrial fibrillation (AF). Her N-terminal pro–B-type natriuretic peptide levels were elevated at 6,110 ng/L (reference, <222 ng/L).

Learning Objectives

To understand the concept of LVOTO and its risk factors following TMVR.

To appreciate the potential role of a flail AML in the development of a dynamic LVOTO, following TMVR.

Past Medical History

Comorbidities included hypertension and moderate renal dysfunction.

Investigations

Echocardiography showed a severely distorted mitral valve and severe mitral regurgitation, primarily caused by a large coaptation deficit in the A3-P3 and A2-P2 regions (Video 1). The leaflet tips were prolapsing or flail but possibly with intact, but elongated, primary chords to the leaflet edges in the A3-P3 segments (Figure 1, Video 2). There was a probable rupture of a primary chord more toward the A2 segment, with a flail leaflet tip (Figure 2, Video 3). Left ventricular ejection fraction was preserved at 60% to 65%.

Figure 1

Preoperative Transesophageal Echocardiography Biplane View

A cut plane through the medial (A3-P3) part of the valve showing prolapsing anterior and posterior leaflet tips (asterisks).

Figure 2

Preoperative Transesophageal Echocardiography Biplane View

A cut plane slightly more central than in Figure 1. A flail segment of the anterior leaflet (asterisk) is seen.

Cardiac computed tomography (CT) showed dimensions suitable for a Tendyne prosthesis (Abbott Vascular), a self-expandable, transapically inserted mitral valve prosthesis with an apical tether (Figure 3). The risk of left ventricular outflow tract (LVOT) obstruction (LVOTO) was perceived as low. The projected minimal area of the so called neo-LVOT was adequate at approximately 3.5 cm2 (Figure 4), and the anterior mitral leaflet (AML) was not excessively long, measuring approximately 21 mm (Figure 5).

Figure 3

Tendyne Prosthesis

A stented transapically inserted mitral bioprosthesis with a tether attached to an apical pad. (Courtesy Abbott. Tendyne is a trademark of Abbott or its related companies. Copyright Abbott 2021. All rights reserved. Tendyne is not approved for use in the United States.)

Figure 4

Preprocedural Computed Tomography

Virtual implantation of the intended Tendyne (Abbott) valve size at end-systole. The projected neo–left ventricular outflow tract area is planimetered at 3.5 cm2.

Figure 5

Preprocedural Computed Tomography

Anterior mitral leaflet (yellow line) measuring approximately 21 mm. CAU = caudal; RAO = right anterior oblique.

Management

A transcatheter mitral valve replacement (TMVR) procedure was considered the preferred management option by the heart team. Other transcatheter options, such as edge-to-edge repair or annuloplasty, were deemed futile because of the morphologic features of the valve.

A Tendyne prosthesis was implanted through transapical access with the patient under general anesthesia. After valve deployment, the patient became hypotensive, and transesophageal echocardiography showed a narrow neo-LVOT and systolic anterior motion (SAM) of the AML (Video 4). Continuous-wave Doppler imaging showed severe LVOTO with a peak gradient of up to 100 mm Hg (Figure 6). Management included volume infusion of Ringer solution and albumin, as well as afterload increase with norepinephrine, with a positive hemodynamic response, and the procedure could be concluded. The patient was weaned from mechanical ventilation a few hours later.

Figure 6

Intraoperative Left Ventricular Outflow Tract Obstruction

Continuous-wave Doppler transesophageal echocardiography with a systolic peak gradient of up to 100 mm Hg.

On postoperative day 1, there was persistent SAM (Figure 7, Video 5) with moderate LVOTO (peak gradient 33 mm Hg). Clinically, however, the patient was recovering well. On day 3, AF occurred; it was cardioverted to sinus rhythm but soon recurred. Further AF management was medical.

Figure 7

Transthoracic Echocargiography Postoperative Day 1

Parasternal long-axis view. The native mitral leaflets drape the stent (asterisk) of the Tendyne (Abbott) prosthesis. There is systolic anterior motion of the tip (dagger) of the anterior mitral leaflet with septal contact.

On day 4, echocardiography surprisingly showed that the tip of the native AML was completely flail, with some part of the mitral apparatus almost prolapsing across the aortic valve in systole (Figure 8, Video 6). Separate structures could be seen in the LVOT in systole: the AML; and parts of a chord or chords, now ruptured, the other part of which could be seen still attached to the posteromedial papillary muscle (Video 7). The event is illustrated in Figures 9A and 9B for clarification. With this new, spontaneous chordal rupture, systolic support to part of the AML was lost, thus rendering it completely flail. Previous systolic contact between the septum and the AML, that had created LVOTO, was thus abolished, and the peak LVOT gradient dropped to approximately 13 mm Hg (Figure 10). The prosthesis was still well seated. The patient kept recovering well and was discharged to her local hospital on postoperative day 6.

Figure 8

Transthoracic Echocardiography Postoperative Day 4

Parasternal long-axis view with a flail anterior mitral leaflet (asterisk) and part of a ruptured chord or chords seen in the left ventricular outflow tract in systole.

Figure 9

Development of Chordal Rupture

(A) Mitral valve prosthesis in place and systolic anterior motion of the native anterior mitral leaflet with septal contact are seen (B) After spontaneous rupture of a chord (or chords), the tip of the anterior mitral leaflet is seen completely flail in the left ventricular outflow tract, resulting in loss of septal contact and no significant residual left ventricular outflow tract obstruction. (Illustration courtesy Magnus Dalén.)

Figure 10

Transthoracic Echocardiography Postoperative Day 4

No significant left ventricular outflow tract obstruction, with a peak gradient (Max PG) of 13 mm Hg. Vmax = maximum velocity.

Discussion

TMVR is a promising treatment alternative for patients with symptomatic mitral regurgitation but at a high or prohibitive surgical risk (1). There is, however, a risk of introducing LVOTO, associated with increased mortality (2), and concern for LVOTO is an important limitation in the use of TMVR (3).

LVOTO can occur because a narrow neo-LVOT may be created between the stent of the prosthesis and the septum of the left ventricle. Apart from this fixed narrowing, a dynamic component resulting from SAM of the AML may occur and cause or aggravate LVOTO (4).

To avoid the introduction of a narrow neo-LVOT, preprocedural planning includes cardiac CT with virtual implantation of the intended valve prosthesis and calculation of the systolic area of the projected neo-LVOT (4). Apart from anatomical factors, such as the aortomitral angle, the presence of a “septal bulge,” and the size and profile of the prosthesis to be implanted, the risk of LVOTO is also related to the properties of the AML. Specifically, an elongated AML is cited as a risk factor for LVOTO through SAM (4).

Transcatheter techniques used to avoid or abolish LVOTO include septal alcohol ablation to reduce basal septal hypertrophy (4) and the laceration of the AML to prevent LVOTO (LAMPOON) procedure in case of concern for SAM (5). Moreover, implantation of a transcatheter aortic valve has been undertaken as a bailout procedure to abort SAM mechanically (6); interestingly, in that case, as in ours, there was also a flail AML in the preoperative evaluation.

In our case, LVOTO was not expected. The projected neo-LVOT was not small, and the AML was not excessively long. However, prolapse and flail of the AML with a highly mobile, untethered leaflet tip occurred. Probably, this was the underlying feature predisposing it to persistent SAM and LVOTO after prosthesis implantation because the stent of the prosthesis pushed the AML with its mobile tip toward the septum. However, LVOTO was surprisingly resolved by spontaneous chordal rupture. Possible explanations for this rupture include chordal stretching and strain secondary to the anterior motion of the AML, as well as chordal stretching or damage by the valve prosthesis. This chordal rupture proved beneficial because LVOTO was abolished, and no negative impact was evident clinically or echocardiographically. After transient hemodynamic instability after valve deployment, LVOTO in our case was moderate, with no severe hemodynamic consequences. However, in situations with critical LVOTO resulting from SAM following TMVR, intentional rupture of chords to the AML could potentially serve as a bailout procedure. This warrants further study.

Follow-Up

At 3 months postoperatively, the patient was in NYHA functional class I. The AML was still flail in the LVOT, and there was no significant LVOT-gradient (peak gradient of 12 mm Hg). The latest follow-up to date was carried out by telephone, at 13 months postoperatively, and the patient was doing well, reporting no change in clinical status.

Conclusions

First, with TMVR, the presence of a flail AML may raise concerns for LVOTO, even when the projected neo-LVOT is of an adequate dimension and the anterior leaflet does not appear excessively long. Second, on the basis of this case with resolution of SAM and LVOTO with the spontaneous rupture of chords to the AML, intentional rupture of chords could be considered as a bailout procedure if there is a critical hemodynamic situation. This warrants further study.

Funding Support and Author Disclosures

Dr Norgren has received consulting fees from Abbott Vascular. Dr Feldt has received consulting fees from Abbott Vascular. Dr Rück has received proctor fees, research support, and lecture fees from Boston Scientific, Medtronic, and Edwards Lifesciences. Dr Settergren is a proctor and advisory board member for Abbott Vascular, Boston Scientific, Medtronic, and Edwards Lifesciences. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.