Going all in: left ventricular outflow tract, aortic root and intervalvular fibrous body reconstruction for extensive infective endocarditis

The most fundamental principle of emergency surgery is to perform the safe operation, the one that brings the patient out of the operating room alive. Specific to infective endocarditis (IE), the most important surgical goal is for radical resection of all infected structures, including any pre-existing prosthetic material, to enable a reconstruction without residual nidi of infection [1, 2]. There is an innate tension between these 2 principles; a more complete resection necessitates a more complex and higher-risk operation. Infective endocarditis is an infection of the endocardium, the innermost lining of the heart and heart valves. Its incidence seems to be increasing, from 9.3 cases per 100 000 in 1998 to 15 cases per 100 000 as of 2011 [3]. Over time, the presentation of IE has evolved; the incidence of prosthetic valve endocarditis (PVE) has increased [2, 4, 5], while Staphyloccocus aureus invasion [2, 5, 6] has become the most common identifiable aetiology. Mortality is higher in cases of PVE compared to native valve endocarditis [7–9]. Both PVE [10] and S.aureus-associated IE [7] typically result in more extensive infection, thereby necessitating more aggressive resection and repair [1]. Overall, IE is the cardiac valve disease with the highest operative mortality. Despite advancing surgical techniques and perioperative care, mortality remains high, even in experienced IE repair centres [1–3, 6, 8, 9, 11, 12]. However, extensive IE is usually fatal in the absence of any invasive treatment [1]. Infective endocarditis involving the intervalvular fibrous body (IFB)—also known as the aortomitral curtain—is an extremely high-risk subset of IE that requires reconstruction of the IFB. Intervalvular fibrous body reconstruction is a procedure that remains notorious for its complexity and risk, even in the best of hands [1]. The majority of patients presenting with IE involving the IFB have PVE and have had previous cardiac surgery [8, 11]. A significant proportion of patients are critically ill, presenting with cardiogenic shock, sepsis or septic shock, septic embolisms including preoperative strokes, or paravalvular abscesses [8, 11]. In consecutive series of patients operated on for IFB-associated IE, the mean logistic EuroSCORE can be as high as 36–53% [8, 11]. Some of the most complex adult intracardiac operations are undertaken in this subset of patients with extreme surgical risk and numerous negative prognosticators (e.g. prior cardiac surgery [13], PVE [7–9, 13, 14], S.aureus invasion [2, 4, 6, 8, 9, 13, 15], cardiogenic shock [6, 8, 13], sepsis/septic shock [6, 7, 9, 15], preoperative stroke [2, 6] and preoperative heart failure [6, 13]). Surgical repair of IE involving the IFB can be performed in a variety of ways: the classical commando procedure, first described by David et al. [16] at the Toronto General Hospital, modified commando procedures [17, 18], the hemi-commando procedure [12, 19] with or without a homograft root replacement [14], the mitral monobloc [20] and the technique described by El-Sayed Ahmad et al. [21]. The classical commando procedure is a combined mitral and aortic valve replacement with or without a root replacement completed through a transaortic incision that is carried down through the non-coronary sinus and over the dome of the left atrium. The IFB is reconstructed via a 2-layer patch with one side closing the left atrial incision and the other closing the longitudinal incision into the aorta [22]. The modified commando procedures are essentially commando procedures with IFB reconstruction via a patch, but the anchor points of the patch are at differing orientations to facilitate a more extensive initial exposure and reduce tension during reconstruction [17, 18]. A hemi-commando procedure is a commando procedure that spares the mitral valve [12, 19]. The mitral valve can be spared via standard mitral repair techniques, or it can be repaired using the aortomitral tissue on an aortic homograft root [14]. In cases where the mitral valve needs to be replaced, homografts can still be used to reconstruct the aortic root and IFB to minimize prosthetic material. The mitral monobloc is a technique that seats a prosthetic mitral valve in a circumferential Dacron annulus with an associated strip of Dacron becoming the neo-IFB and patch for the aortic wall [20]. Despite guideline recommendations [1] for the use of aortic homograft roots in extensive PVE to minimize prosthetic material and recurrent IE, contemporary data have not demonstrated clear benefits related to mortality, recurrent IE or reoperation rates for homografts compared with conventional bioprosthetic and mechanical valves [23]. In this issue of the Journal, El-Sayed Ahmad et al. [21] present the impressive short and midterm results of their surgical approach to extensive IE involving the aortic root, mitral valve and IFB. This study is a single-centre consecutive series of the 41 patients who underwent this extensive repair between March 2017 and February 2021 at their high-volume referral centre for IE. During the same period, a total of 216 patients underwent IE repair at their centre. Unsurprisingly, the patients in this study were complex and critically ill. Most patients had previous cardiac surgery, PVE, paravalvular abscesses and underwent the surgical repair on an emergent basis. The most common positive blood culture was S.aureus. Importantly, a significant proportion of patients presented with cardiogenic shock, sepsis, a recent stroke or a recent septic embolic event. Correspondingly, the median logistic EuroSCORE in this series was 35%. These demographics are comparable to the most pertinent modern series describing the surgical repair of extensive IE, exemplifying the operative complexity routinely encountered in a patient population that can, not uncommonly, present in extremis [8, 9, 11, 12, 14, 19, 24]. Their surgical technique was aggressive. In every case, the mitral valve and entire aortic root were replaced, bioprosthetic valves were used 73% of the time, and a tubular Dacron prosthesis was implanted at the level of the left ventricular outflow tract (LVOT). The LVOT conduit was secured with an everted double-suture technique first described by Nakamura et al. [25]. When indicated, coronary ostia were reimplanted via a modified Cabrol technique. A patch was then used to seal the initial defects following exposure via the left atrial roof and notably the interatrial septum in all cases. These complex operations were completed expeditiously with median cardiopulmonary bypass and aortic cross-clamp times of 126 and 78 min, respectively. Acknowledging the perioperative risk of this cohort, where each patient underwent a double valve and aortic root replacement, their 30-day and 1-year mortality were acceptable compared to other extensive IE repair series where not all patients required double valve or aortic root replacement [8, 9, 11, 12]. Their cardiopulmonary bypass and aortic cross-clamp times were significantly faster than the time required to undertake the other types of repair in extensive IE [8, 9, 11, 12], with relatively low reoperation rates for postoperative bleeding [8, 9, 12]. New postoperative stroke rates were similarly low [8, 9, 12]. The benchmarks set by El-Sayed Ahmad et al. [21] outperformed series where not all patients required double valve and aortic root replacements. These impressive results demonstrate that aggressive resections followed by complex reconstruction can be achieved expeditiously in a patient population that serves to benefit from every minute spared from cardiac ischaemia and the proinflammatory, coagulopathic environment of the cardiopulmonary bypass circuit. A circumferential LVOT conduit provides a stable, haemostatic proximal anastomosis as well as a secure neoaortic root to seat the prosthetic aortic valve. Non-root replacement techniques often rely on patch augmentation of the native annulus and root that can be friable and inflamed due to prior adjacent paravalvular abscesses. There is also the serious, albeit rare, risk of pseudoaneurysms at the IFB with the main risk factors being PVE, ring abscesses and prior valve surgery [26]. Conceptually, relying on a Dacron conduit to bridge the anterior mitral annulus to the aortic annulus would provide a more secure neo-IFB than a conventional patch but long-term data and comparative studies are required to ascertain this further. As this is a single-centre, observational, non-comparative study done in an expert, high-volume, referral centre with a small sample size and limited follow-up duration, conclusions regarding generalizability and long-term results of this technique should be drawn with caution. Regardless, current guidelines recommend that surgical repair of IE should be concentrated at centres of excellence within multidisciplinary IE teams [1, 2, 7]. It stands to reason that this level of complex reconstruction could be reproduced at centres skilled enough to routinely operate on this patient population. While the pacemaker implantation rate in this study is reasonable and expected given the extent of disease and 100% rate of root replacement in this cohort [8, 9, 12, 24], the recurrent IE rate and consequent reoperation rate were higher than in contemporary extensive IE repair series [8, 9]. A useful comparator arm in this study would have been homograft root reconstruction. This comparison is particularly relevant because the repair technique in this series commits the patient to the most amount of prosthetic material of all the IFB reconstruction techniques described above [12, 14, 17–20, 22]. One must wonder if the potential benefits of faster operative times, reduced bleeding risks, reduced postoperative strokes and conceptually increased LVOT stabilization are not diminished by a higher rate of recurrent IE which, in this patient population, would translate into an even higher-risk reoperation. Longer-term follow-up is required to assess this balance of risks. Indeed, El-Sayed Ahmad et al. [21] went all in, presenting their promising initial results of a fast, reproducible and aggressive operation for IE of the IFB. Their perioperative and midterm outcomes are comparable to benchmarks set by highly experienced centres and time-tested techniques performed on patients with less operative complexity. Should these results be reproduced in other centres of excellence—and should the long-term incidence of recurrent IE prove acceptable—this technique could become a useful addition to the surgical armamentarium for the treatment of extensive IE. Conflict of interest: The authors report no potential conflict of interest.

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