A standardized approach to treat complex aortic valve endocarditis: a case series

In this case series we aimed at providing evidence for the standardized use of a stentless bioprostheses in complex aortic valve endocarditis. “Standardized use” refers to the use of one type of stentless bioprosthesis for a variety of anatomical problems complicating aortic valve endocarditis. Clinical data and high quality macroscopic pictures from sixteen patients with active aortic valve endocarditis and paravalvular abscess formation were collected between 2006 and 2015. In this time period, a total of 85 patients underwent aortic valve surgery for endocarditis in our center. Here, we report on those patients treated with stentless bioprostheses. Their endocarditis was not limited to the cusps but also involved the annulus with formation of large paravalvular abscesses at various anatomical locations. Consequently, complications arose, such as root disarrangement with loss of aortaventricular or aortomitral continuity, atrioventricular conduction disturbance, or infection of the septum or the right ventricle. Despite their poor clinical condition, these patients were deemed eligibile for surgical valve repair and LVOT reconstruction using stentless bioprostheses.

Infective endocarditis was diagnosed based on the modified Duke criteria [4] and expert opinion of a multidisciplinairy team. Prosthetic valve endocarditis was considered early if it occurred during the first year after valve replacement, otherwise it was considered late [2]. Causative micro-organisms were identified by culture and molecular testing on peripheral blood and tissue or prosthetic material collected during surgery [2]. Functional cardiac derangements as described by the guidelines were important indications for surgery [2, 19]. Macroscopically visible pathological findings considered an indication for the use of stentless bioprostheses were presence of destructive lesions, including annular abscess, paravalvular leak and cusp perforation. Re-thoracotomy was defined as reopening of the sternum after implantation of the bioprosthesis. Reoperation was defined as any surgical procedure involving the implanted bioprosthesis. Recurrence was used as a combined term for both relapse (repeat episodes of endocarditis caused by the same microorganism) and reinfection (infection caused by a different microorganism) [2].

The Freestyle® bioprosthesis (Medtronic Inc., Minneapolis, MN, USA) is a stentless porcine aortic root prosthesis with ligated coronary arteries and a thin skirt over the porcine septal myocardium. The bioprosthesis is fixed with low pressure applied to the aortic wall, and zero-net pressure across the leaflets (Fig. 1). Pre-implantation, the bioprosthesis underwent an anticalcification treatment using alpha-amino-oleic acid. The device can be implanted by various techniques: subcoronary valve replacement, root inclusion, or complete aortic root replacement.

The standard surgical approach was a median (re)sternotomy with mild/moderate hypothermic (32–34 °C) cardiopulmonary bypass and cardioplegic cardiac arrest (retrograde blood cardioplegia). Cardiopulmonary bypass was performed using aortic cannulation and right atrial or bicaval cannulation for venous drainage.

The aorta was transected above the sinotubular junction. After the aortotomy exposure, the abscess regions were inspected (Fig. 2) and infected native cusps or prosthesis as well as any aortic aneurysms were removed with extensive tissue debridement. The aortic sinuses were resected with trumpet-shaped recesses of the coronary ostia. More specifically, a ventricular septum defect just under the membranous septum was identified in Fig. 2a. In this case a pericardial patch was used, which was distally sutured on the septum covering both the defect and the membranous septum, proximally attached at the level of the aortic annulus. Figure 2b and c depict chronic dehiscence of a mechanical prosthesis (implanted after a Bentall procedure) as a result of abcess formation at the annular level. Interestingly, the prosthesis was found floating above the annulus, only attached by the coronary arteries. Hence, the adhesions surrounding the annulus kept the prosthesis in place. Following resection of the infected prosthesis and clearance of the abcess, the stentless bioprosthesis was sutured on the annulus using a single-stitch technique. Given the chronic nature of disease in this case, the bioprosthesis was parachutted downwards towars the subannular plane to minimize traction of the chronically anchored anterior mitral leaflet (AML). In contrast, Fig. 2d and e illustrate acute subannular abcess formation. In this case, the AML was detached from the annulus while the prosthesis attachment site remained intact. In this case, due to the recent onset of infection, traction of the AML to the annulus plane and a neo-annulus were created after clearance of the abcess and other inflammatory tissue. Afterwards the stentless bioprosthesis was sutured to the annulus. Figure 2f to h depict Gerbode lesions with tricuspid valve involvement. Gerbode(−like) lesions encompass fistulas formed between the left ventricle(aorta) and the right side of the heart, appearing above or below the septal leaflet of the tricuspid valve. Repair of the sub-valvular fistula from the right side included temporary resection of the spetal leaflet of the tricupid valve, which was thereafter re-attached.

After debridement, restoration and sizing of the aortic annulus the proximal anastomosis was performed using 20–25 interrupted sutures of Ticron 3–0 in a single plane. If required, the coronary ostia were mobilised using diathermy. After completion of the proximal suture line, the patient’s coronary ostia were reimplanted end-to-side to the corresponding sinus of Valsalva of the prosthesis using a continuous 5–0 polyproylene suture. Finally, the bioprosthesis was anastomosed with the aorta using continuous 4–0 polyproylene. If further resection of the ascending aorta was required, a vascular tube graft was interposed.

The institutional medical ethical review board of the University Medical Center Groningen approved the use of retrospective patient data for our study and waived informed consent (METc2015/033; February 2015).

This series consecutively included 14 males and 2 females with a median age of 63 years (Tables 1 and 2). All patients had an urgent indication for cardiothoracic surgery with implantation of a stentless bioprosthesis as root replacement due to uncontrolled infection and abscess formation (evidence class I and level B [2]). Median New York Heart Association score was III, and median logarithmic EuroSCORE I score was 40.7. Median follow-up for survivors was 4.6 years. All survivors were followed for at least 2 years, 36% were followed for 5 years, and 9% for 10 or more years. In 4 patients (25%) the endocarditis involved native aortic valves, with 2 identified bicuspid valves. In 12 patients (58%) the endocarditis involved prosthetic aortic valves: in 7 patients the aortic valve was replaced once and in 1 patient twice before, in 5 patients a Bentall procedure had been performed. Of the patients with prosthetic valves, 2 patients had early (3–4 months after surgery) and 10 patients late endocarditis (1–29 years after surgery). In-hospital and 30 day mortality were 18.8% and 12.5%, respectively; 2-year recurrence rate was 14%.

Several situations of active aortic valve endocarditis with paravalvular abscess formation and accompanying pathologies were deemed eligible for valve repair and LVOT reconstruction with a stentless bioprosthesis (Figs. 2, 3, 4 and 5).

Infective endocarditis is a cardiac disease with extracardiac complications due to hematogenous and embolic spread. In our series, the three most common complications were: mycotic aneurysm (n = 3), cerebral emboli (n = 2), and vertebral osteomyelitis (n = 2).

Figure 6 shows the survival of included patients for 11 years. Five patients died during this period (Table 2), due to: end-stage heart failure 227 days post-surgery; recurrent respiratory insufficiency resulting from sputum retention, encephalopathy and extended postoperative wound infection 40 days post-surgery; active intra-cerebral bleeding without therapeutic options 14 days post-surgery; re-infection of the prosthesis with cerebral embolization, mediastinitis and kidney failure 388 days post-surgery; severe hemodynamic instability immediately post-surgery.