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Surgical aspects of valve replacement in carcinoid heart disease

Abstract Tricuspid and pulmonary valve replacement in patients with advanced carcinoid heart disease (CaHD) reduces right heart failure and improves prognosis. The surgical literature is limited concerning description of technical aspects of valve replacement in CaHD. Although a dedicated multidisciplinary care is required for these frail patients, optimization of surgical technique is important and may lead to better postoperative outcomes.


| INTRODUCTION
Carcinoid heart disease (CaHD) is a complication of metastasizing neuroendocrine tumors (NETs), which are rare slow-growing malignancies usually originating in the small intestine. High levels of circulating serotonin and other vasoactive substances released by the tumors cause, by complex processes, formation of plaques and fibrosis of the tricuspid (TV), and pulmonary valves (PV). Advanced CaHD of the right-sided valves leads to severe regurgitation and/or stenosis, eventually causing progressive right heart failure and worsening of the patient´s oncological prognosis. 1 Valve surgery in CaHD patients has been shown to reduce right heart failure, increase functional capacity, allow for more aggressive oncological treatment and improve long-term prognosis. Several smaller series of 19-32 operated patients have been reported, [2][3][4] but the largest one is the 30-year experience from Mayo Clinic with 240 CaHD patients. 5,6 In this study, 30-day mortality after surgery was 5%, while 2-year survival was 60%, with most patients succumbing to progressive tumor burden. Despite the prevalent outcome reporting, there is a remarkable shortage in the surgical literature concerning the technical aspects and optimization of surgical details of valve replacement in these rare patients. Tricuspid valve replacement (TVR) is always a part of these operations, and most often the pulmonary valve has to be replaced concomitantly (PVR). However, TVR and PVR are quite uncommon procedures in routine adult cardiac surgical practice. Patients with severe CaHD are frail and optimal surgical technique may lead to better outcomes. The focus of the current report is not to demonstrate patient results, but to describe some of the surgical technical issues concerning TVR and PVR in CaHD, based on our recent experience of 17 cases in the past 4 years ( Table 1). The need for informed consent was waived by the local ethics committee.

| PRE-AND PERIOPERATIVE CONSIDERATIONS
Indications for valve surgery in CaHD patients are outlined in guidelines 7 and include progressive right heart failure with echocardiographical findings of moderate to severe insufficiency of the right-sided valves. The TV is always involved in surgical candidates and is usually severely regurgitant, while the PV often shows a combination of stenosis and regurgitation. The decision for valve replacement should be based on a multidisciplinary evaluation of general operability in relation to oncological status and cardiac function. Timing of surgery with preoperative optimization of nutritional status and somatostatin analog treatment for carcinoid hormonal activity is essential. Studies indicate that earlier intervention rather than late improves outcomes. 7 In our experience, the PV pathology is often underestimated on preoperative echocardiography, and a larger regurgitation may be unmasked by a higher forward flow after TVR, if leaving the PV untreated. Also, an uncorrected significant pulmonary regurgitation after TVR may lead to progressive right heart dilatation and poorer results. 8

| OPERATIVE TECHNIQUES
Both mechanical and bioprosthetic valves have been used for the right-sided valve replacements in CaHD. However, in recent reports, bioprostheses seem to be preferred, as life-expectancy is limited in these patients and warfarin therapy may not be well managed. 5 After sternotomy, aortic cannulation is performed in standard fashion, although inserting the cannula more to the right side of the ascending aorta will improve exposure of the PV. Both venae cavae are snared after separate venous cannulation and commencing cardiopulmonary bypass (CPB). Triple lines for pump suction are utilized and CO 2 wound irrigation is started. Basically, both right-sided valves can be replaced on CPB using no or intermittent aortic cross-clamping. In our view, however, cardioplegic arrest provides better visualization and detailed evaluation of the diseased valves, and more accurate placement of valve sutures. Before starting CPB, the planned incision on the anterior surface of the pulmonary artery (PA) is marked by a felt pen. The order of valve replacement is by surgeon preference, but we generally begin with the PV. We use only antegrade cold blood cardioplegia, every 20 min and in large amounts, for optimal protection of the RV. Retrograde cardioplegia may be insufficient in this respect.

| Pulmonary valve
An incision is made in the proximal PA and extended backwards across the PV and 3-4 cm into the right ventricular outflow tract (RVOT; Figure 1A). The PV is exposed by stay-sutures, evaluated,

| Tricuspid valve
After opening the right atrium (RA), a methodical inspection for and closure of a persistent foramen ovale should be performed.