Role of Concomitant Valve Surgery in Orthotopic Heart Transplant

Abstract

There remains a significant shortage of donor hearts despite an ever-increasing demand. In an effort to maximize the utilization of this scarce resource, extended criteria for donor hearts with surgically correctable abnormalities should be considered. Bench valve surgery on the donor heart prior to heart transplantation is feasible, and its implementation could enable the use of previously unsalvageable hearts, thus expanding the donor organ pool. With proper donor and recipient selection, bench valve surgery will enable the expansion of the donor pool to provide high-quality donor allografts that would otherwise have been declined. This chapter reviews the current practices employed in heart transplantation, with emphasis on the surgical technique for concomitant valve surgery in the donor heart prior to transplantation.

1. Introduction

Orthotopic heart transplantation is the gold standard treatment for end-stage heart failure [1]. According to the 2019 Registry of the International Society for Heart and Lung Transplantation, approximately 5000 heart transplantations were performed from July 1, 2017, to June 30, 2018 [2] (Figure 1). With the increasing prevalence of heart failure, it is estimated that over 25,000 patients annually can benefit from heart transplantation [3].

Figure 1.

Number of adult and pediatric patients who underwent orthotopic heart transplantation by year, from the International Society for Heart and Lung Transplantation 2019 report.

There are approximately 3000 candidates on the heart transplant waiting list in the United States. The mortality rate on the waiting list is approximately 15%, and the annual number of heart transplants is approximately 2500. Thus, there remains a severe shortage of donor hearts despite an ever-increasing demand. In an effort to maximize the utilization of this scarce resource, extended criteria for donor hearts with surgically correctable abnormalities should be considered [4]. Although there is consensus that mild valvular abnormalities in the donor may be amenable to repair or replacement on the bench [5], only a limited number of reports [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16] in the literature exist, and a standardized technique has not been well established or adopted.

This chapter reviews the current practices employed in heart transplantation, with emphasis on the surgical technique for concomitant valve surgery in the donor heart prior to transplantation.

2. Donor considerations

Upon receiving information regarding a possible donor for a heart transplant, the recipient team considered several essential factors (Figure 2) [17], and donor quality assessment is determined first. Once information regarding the donor has been received, donor quality assessment is determined first.

Figure 2.

Guidelines for an algorithm for the management of potential heart donors. CVP: central venous pressure; HCT: hematocrit; Hb: hemoglobin; MAP: mean arterial pressure; LVEF: left ventricular ejection fraction; T3: triiodothyronine; SVR: systemic vascular resistance; BG: blood glucose; and PCWP: pulmonary capillary wedge pressure.

Organic valve disease is considered a contraindication when using a donor organ for heart transplants. It has been reported that certain donor criteria have been expanded safely, but only sporadic cases have been reported in the literature regarding bench repair or replacement of valves before heart transplantation. Of the reports in the last 25 years [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16], Risher et al. [14] in 1994 were the first to report on mitral commissurotomy of the donor heart before transplantation. However, heart valve disease remains a contraindication for heart donation in most heart transplant centers.

3. Mitral valve abnormalities

Mitral valve bench correction has rarely been performed because of concerns related to the feasibility of repair and durability. The additional ischemic time required to perform valve repair or replacement needs to be taken into account before using a donor heart with valvular dysfunction.

The assessment of mitral valve regurgitation in a donor patient is essential to determine the mechanism, severity, and reversibility of the disease before planning mitral valve repair. A thorough review of the donor echocardiogram should be performed to determine the exact nature and pathology of mitral regurgitation in otherwise acceptable donor hearts. If the mechanism of mitral regurgitation is simple, then bench repair can be performed by increasing the duration of warm ischemia time before transplantation.

However, the evaluation may be compromised by a decrease in afterload resulting from the loss of peripheral vascular tone or inflated by transient ventricular dysfunction [18]. For this purpose, transesophageal echocardiographic evaluation is necessary to understand whether mitral regurgitation is surgically treatable. Therefore, there is sufficient reason to perform bench mitral valve repair without a significant increase in recipient morbidity and mortality. In addition, donor hearts should not show any electrocardiographic or echocardiographic signs of left ventricular hypertrophy (LVH). The authors believe that in some cases, the presence of mitral regurgitation with moderate pulmonary hypertension may be a protective factor as the right ventricle is preconditioned to a high afterload.

4. Aortic valve abnormalities

Only a small number of heart transplants with concomitant aortic valve replacement for moderate-to-severe aortic insufficiency or aortic stenosis have been documented [6, 7, 9, 10, 12, 15]. It has been reported [7] that a bioprosthetic valve is preferred on a predicted average donor heart survival of 10–15 years [2] and the relatively frequent need for endocardial biopsies early after transplantation. The need for warfarin after mechanical valve replacement could lead to frequent bridging and interruption of anticoagulation during scheduled endocardial biopsies. In addition, it was considered that a large bioprosthesis would likely outlast the life of the allograft. When the donor has a bicuspid valve, the donor’s aorta carries an increased risk of expansion due to the inherent nature of the bicuspid aortic valve. In younger individuals with normal life expectancy, aortic valve repair may be an excellent alternative since the risk of structural valve deterioration of aortic bioprosthesis is known to be higher in younger patients. Rates of reoperation as high as 50% in 15 years have been reported in 25-year-old patients [19].

If aortic valve replacement is considered for a donor heart, careful evaluation of LVH status and expected ischemic time is mandatory. This is because significant LVH and prolonged ischemic time has been proven to jeopardize transplant outcomes.

The use of donor hearts with LVH has yielded mixed results in terms of recipient outcomes. Kuppahally et al. [20] reported that recipients of donor hearts with LVH (≥ 1.2 cm) had worse survival and a higher incidence of cardiac allograft vasculopathy (CAV). Subsequently, Pinzon et al. [21] reviewed the UNOS database between 2006 and 2010 with almost 3000 recipients and stratified donor hearts into groups without LVH (< 1.1 cm), with mild LVH (1.1–1.3 cm), and with moderate-severe LVH (≥ 1.4 cm). They found similar 30-day and 1-year survival rates across the recipients in all three groups. However, hearts from donors with additional risk factors such as older age or prolonged cold ischemic time (≥4 h) exhibited worse survival [21], suggesting an association between LVH and other donor risk factors. The 2010 ISHLT guidelines for the care of heart transplant recipients state that using donor hearts with LVH (wall thickness < 1.4 cm) and without accompanying electrocardiograms (ECG) findings of LVH may be appropriate (class IIa; level of evidence C) [22]. Thus, the authors suggest that it is reasonable to avoid a donor heart presenting with posterior wall and interventricular septum thickness > 14 mm during diastole. The presence of aortic valve disease (stenosis or insufficiency) in the absence of left ventricular hypertrophy should not preclude donor considerations.

Careful attention must be paid to allograft ischemic time since bench valve surgery requires additional warm ischemic time. Currently, the allograft ischemic time is limited to 4–6 h. In fact, a study utilizing the UNOS database that included over 11,700 patients undergoing heart transplantation reported that ischemic time was an independent risk factor for survival in patients with an ischemic time > 6 hours [OR 1.7 (1.0–2.8), p < 0.05] and in patients with an ischemic time between 4 and 6 hours [OR 1.4 (1.3–1.6), p < 0.05] [23]. Several reports have shown that longer ischemic time is associated with a higher risk of mortality [24, 25]. Moreover, it has been reported that long cold ischemic time may introduce primary graft dysfunction, CAV, and increased length of stay in intensive care [26, 27]. Conversely, some investigators have demonstrated that a prolonged ischemic time does not negatively impact the 1-year survival following heart transplantation [28, 29]. After the heart allocation policy was revised in the United States [3], it was reported that the mean total allograft ischemic time increased from 3.0 to 3.4 h (P < 0.001), with a concurrent increase in median distance between donor and recipient transplant centers from 83 to 216 miles [30]. Therefore, the acceptable maximum allograft ischemic time remains a matter of debate; however, a longer allograft ischemic time is not without risk.

5. Tricuspid valve abnormalities

Heart transplantation is often associated with tricuspid regurgitation (TR). Structural or functional factors can be associated with TR. The biatrial technique of heart transplantation is associated with more TR than the bicaval technique. The incidence of post-transplantation TR has decreased since the introduction of the bicaval anastomosis implantation technique by Yacoub et al. in 1989 [31, 32]. This was believed to be related to the reduced right atrial pressure and preserved right atrial size during the use of a bicaval rather than a biatrial anastomosis technique [33]. Other possible causes of TR include (1) allograft dysfunction with right ventricular dilatation due to poor preservation, reperfusion injury, donor factors, or rejection; (2) pulmonary hypertension; (3) severe donor-recipient size mismatch; and (4) structural damage during endomyocardial biopsy [34, 35, 36].

It has been reported that prophylactic tricuspid valve annuloplasty of the donor heart is durable and offers a survival advantage in the perioperative and long-term periods [37, 38]. Considering the simplicity and safety of tricuspid valve annuloplasty and its advantages, there should be a low threshold when considering the procedure as a routine adjunct to heart transplantation.

6. Conclusion

The appropriate utilization of the valve repair/replacement technique with precise assessment of an additional warm ischemic time necessitates careful consideration within each transplant center and each patient potentially willing to accept an allograft with valve disease in the context of the expected allograft cold ischemic time.

Bench valvular replacement or repair of donor allografts during cold ischemia is feasible, and its implementation could enable the use of previously unsalvageable hearts, thus expanding the donor organ pool. Bench valve surgery, combined with proper donor and recipient selection, will enable the expansion of the donor pool to provide high-quality donor allografts that otherwise would have been declined.

Conflict of interest

None.