Aortic valve patch closure: an alternative to replacement with HeartMate^® LVAS insertion

Abstract

A PTFE patch sewn to the aortic valve and annulus, to occlude the ventriculoaortic junction is used to successfully correct aortic insufficiency with HeartMate^® (LVAS) insertion. This represents an inexpensive alternative to aortic valve replacement for aortic insufficiency or the presence of a mechanical aortic valve.

HeartMate^®, Left Ventricular Assist

1 Introduction

The HeartMate^® Left Ventricular Assist System (LVAS) (ThermoCardiosystems Inc., Woburn, MA) is a highly successful bridge to transplantation [1,2]. It is a pulsatile pump that fills through a conduit sewn to the apex of the heart and empties through an outflow conduit sewn end-to-side to the ascending aorta. Since the device functions parallel to the left ventricular circulation, regurgitant flow through the aortic valve creates a shunt through the pump. Small amounts of aortic regurgitant flow are tolerated but large amounts must be addressed. A related situation is the patient with a mechanical aortic valve who requires a HeartMate^® (LVAS). When the device is fully supporting the patient, the aortic valve opens intermittently leading to stasis at the valve. This stasis can lead to thrombus formation and subsequent embolism. In the presence of excessive valvular incompetence or a mechanical aortic valve, the current recommendation is to replace the valve with a bioprosthetic valve [3]. If replacement is difficult this can lengthen the ischemic time for device insertion. Furthermore, substantial cost is incurred for implantation of a bioprosthetic valve, which will be removed when the transplant is performed. An alternative approach is to close to ventriculoaortic junction permanently.

2 Case report

The patient is a 25-year-old female with a family history of atrial myxomata. In 1994 a resection was performed to remove multiple myxomata, which included the atrial septum, left atrium and part of the anterior mitral annulus. In 1998 she was diagnosed with a large recurrence and scheduled for elective surgery. The procedure included replacement of the atrial septal patch and mitral valve replacement (St. Jude). The left sinus of valsalva and aortic valve cusp were injured during the operation and repaired by simple suturing (the specific nature of the injury was noted in retrospect at the time of HeartMate^® insertion). Attempts to wean from cardiopulmonary bypass were unsuccessful. A transesophageal echocardiogram (TEE) demonstrated severe left ventricular dysfunction and mild aortic insufficiency. She was placed on extracorporeal life support (ECLS). TEE after 2 days of ECLS demonstrated severe aortic insufficiency, recovery of right ventricular, inferior and inferoseptal left ventricular function; but akinesis of the majority of the left ventricle with an ejection fraction of less than 10%. The decision was made to place the HeartMate^® (LVAS) as a bridge to transplant.

For successful implant of the HeartMate^® (LVAS) the aortic insufficiency needed to be addressed. After switching to traditional cardiopulmonary bypass, the aorta was cross-clamped and the heart arrested using retrograde cold blood cardioplegia. The aorta was opened transversely and the valve inspected. The left main coronary artery was ectopically located, arising above the commissure between the left and the right cusps of the aortic valve. A repaired tear in the aortic extended along the commissure, into this artery. The severe LV dysfunction was secondary to occlusion of the left main coronary, which occurred during repair of the aortic tear. This tear caused prolapse of the left valve cusp. In addition, there was prolapse of the noncoronary cusp of the aortic valve. There was no chance for left ventricular recovery and the only long-term option for recovery was transplant. Aortic valve replacement was considered, however, the annulus and aortic root were small, making replacement difficult and time consuming. The left and noncoronary leaflets were injured precluding simple suture closure. Instead, the left ventricular outlet was closed with a Gore-tex Cardiovascular Patch (W.L. Gore and Associates, Flagstaff, AZ) sewn to the annulus of the non- and left coronary sinuses and the intact right coronary cusp using a running 5-0 polypropylene suture. The HeartMate^® (LVAS) was inserted in the traditional manner. The outflow cannula was anastomosed to the right side of the aorta cephalad to the aortotomy. The patient was easily weaned from cardiopulmonary bypass. TEE demonstrated no evidence of a leak through the aortic annulus. The patch moved with ventricular contraction bowing forward and back. Post-operatively oral anticoagulants were administered for the prosthetic mitral valve.

Eight months after LVAS insertion the patient was successfully transplanted. Examination of the surgical specimen demonstrated the complete closure and tissue incorporation of the patch in the ventriculoaortic junction (Fig. 1). The right coronary artery was unobstructed and 1 cm above the closed junction suggesting there had not been deposition of a large amount of thrombus on the patch. The mechanical mitral valve was healed in place with a single loosely adherent fibrin strand attached to the sewing ring on the atrial side.

Fig. 1

Opened ventricle, mechanical mitral valve, healed occluded LV outlet (smooth, white over MV).

3 Discussion

In the presence of significant aortic insufficiency or a mechanical aortic prosthesis, it is recommended the aortic valve be replaced with a bioprosthesis. As an alternative, we choose to close the ventriculoaortic outlet. In the presence of central aortic insufficiency a patch can be quickly sewn directly to the annulus or intact valve cusps. A patch can be placed after removal of a prosthetic valve or sewn to the sewing ring of a mechanical valve. Though thrombus might form on the patch, in the absence of transvalvular flow the risk of embolism should be minimal. Should there be some recovery of ventricular function, blood is readily ejected through the HeartMate^® (LVAS). In this patient, we continued anticoagulation for the mechanical mitral valve. However, if we had only placed the patch to occlude the ventricular outlet, the recommended regimen of aspirin and dipyridimole for the HeartMate^® (LVAS) would have been used.

In a broader sense, in the absence of any chance for ventricular recovery, we suggest that functional left-sided valves are not necessary in the presence of a HeartMate^® (LVAS). The HeartMate^® (LVAS) uses functional equivalents of the mitral and aortic valves and the left ventricle is ‘atrialized’ when the device functions. On this basis, we suggest and have shown that the ventricular outlet can merely be occluded. It also seems likely that the native mitral valve is not essential after implantation of the HeartMate^® (LVAS) and can be removed if stenotic. In this case we chose to leave the prosthetic valve in place, given the condition of the patient, and length of the procedure. Note that, if there is some ventricular function, in contrast to the ability of the left ventricle to eject through the pump in the event of pump failure with the ventricular outlet occluded, should the pump fail in the absence of a competent mitral valve the patient would soon die.

We feel these approaches are logical and minimize ischemic time, cardiopulmonary bypass time and expense of HeartMate^® (LVAS) insertion.