Surgery for right-sided infective endocarditis

Introduction

Right-sided infective endocarditis (RSIE) most commonly occurs in the setting of intravenous drug use (IVDU) and has taken on increasing surgical significance as the opioid crisis has driven increased abuse of intravenous heroin [ , ]. Surgery for RSIE, which has historically received less attention than left-sided infective endocarditis (LSIE), poses unique challenges because of the high rate of recidivism and recurrent endocarditis in IVD users [ , , ]. Surgical approaches to RSIE must balance competing priorities of maximizing efficacy through effective valve reconstruction and minimizing risk of IE recurrence by limiting implantation of prosthetic material. In this chapter, we will outline distinctive features of RSIE with respect to epidemiology, clinical presentation, and diagnosis and we will define indications for surgical intervention. We will also discuss the major surgical techniques for RSIE and important pre-, intra-, and postoperative considerations.

Epidemiology

RSIE is significantly less common than LSIE, comprising only 5%–10% of total infective endocarditis cases [ , , ]. While RSIE can occur anywhere in the endocardium of the right heart, it displays a 90% predilection for the tricuspid valve with infections of cardiac implantable electronic devices (CIEDs) and the pulmonic valve rounding out the remaining 10% [ ]. The most common risk factor for RSIE is IVDU [ ]. In one study, 34.5% of RSIE patients had a history of IVDU [ ]. Furthermore, even among IVD users, HIV-positive IVD users suffer an odds ratio of 2.31 of developing IE compared to HIV-negative IVD users [ ]. CIEDs, such as pacemakers sand implantable cardioverter defibrillators, and central venous catheters serve as nidi for bacterial colonization and represent alternate mechanisms for the development of RSIE [ ]. Uncorrected congenital abnormalities of the right heart independently predispose patients to RSIE [ ]. With respect to causative microbiological agents, Staphylococcus aureus accounts for 60%–90% of RSIE, but the incidences of methicillin-resistant S. aureus , Pseudomonas aeruginosa , and polymicrobial RSIE are all rising [ , ]. In RSIE related to prosthetic valves and CIEDs, coagulase-negative Staphylococcus species are significant contributors [ , ].

Epidemiological concerns specific to surgery center around the increasing surgical incidence of RSIE and demographic differences between RSIE and LSIE patients. Overall, 5%–40% of RSIE cases require surgical intervention [ , ]. However, IVDU, particularly injection heroin, has more than doubled during the opioid epidemic and with this upsurge, the incidence of IE has increased significantly [ , ]. Additionally, CIEDs have become increasingly common, particularly in the elderly, which has prompted a similar increase in IE [ ]. These increases in the incidence of IE have led to a predictable corresponding rise in the number of required surgical interventions [ ]. In the span of just 6 years (2011–17), the surgical incidence of tricuspid endocarditis increased fivefold [ , ]. The demographic differences between RSIE and LSIE are also a reflection of the IVDU associated with RSIE. RSIE patients tend to be younger, male, and less burdened by comorbidities, reflecting the characteristics of the users of intravenous drugs [ , , ]. The high percentage of recidivism among IVD users (27%) also contributes to a greater percentage of recurrent endocarditis (12%–32%) in RSIE patients compared to LSIE patients [ , , , ]. Lastly, surgeons should be cognizant, both when evaluating imaging studies and performing repair and replacement operations, that 37.9% of RSIE cases are complicated by concomitant LSIE [ ].

Clinical manifestations

RSIE typically presents with constitutional symptoms, chiefly fever, and respiratory symptoms resulting from septic pulmonary emboli [ , , ]. However, because the murmurs of RSIE are often subtle and nonspecific, diagnosis of RSIE can be delayed resulting in a later presentation with a more severe respiratory picture of pleural effusion, hemoptysis, pneumothorax, or pulmonary infarction, abscess, and empyema [ , ]. Cardiac manifestations of RSIE are a function of the severity of tricuspid valve involvement. Vegetations causing severe tricuspid regurgitation can lead to right atrial dilation with the potential for resultant supraventricular arrhythmias and progression to heart failure [ , ]. Systemic emboli with destination-dependent symptoms are possible if a patent foramen ovale is present but are much less common than in LSIE [ , ].

Diagnosis

RSIE presents several unique diagnostic challenges. Infectious endocarditis, including RSIE, can be diagnosed by pathological or clinical criteria [ ]. The Duke criteria, long considered the gold standard for diagnosis of IE, define as major clinical criteria (1) persistently positive blood cultures and (2) echocardiographic evidence of endocardial involvement [ ]. However, the Duke criteria were principally designed for LSIE and minor clinical criteria such as immunologic and vascular phenomena are less applicable to RSIE [ ]. Proposed modifications to the Duke criteria emphasizing the role of transesophageal echocardiography (TEE) have increased the capability of the criteria to detect RSIE [ ]. Transthoracic echocardiography (TTE) has traditionally been the imaging modality of choice for suspected RSIE because of the proximity of the transducer to anteriorly situated right heart structures [ ]. However, multiple studies have demonstrated comparable or improved sensitivity of TEE compared to TTE in the diagnosis of RSIE [ ]. The benefit of TEE relative to TTE is most clearly established in CIED-related RSIE where TTE provides especially poor sensitivity, especially of pacemaker leads situated on the roof of the right atrium [ ]. TEE has been shown to increase sensitivity to CIED-related RSIE by as much as 60% and is therefore mandated in such cases [ , , ]. Intracardiac echocardiography is useful in the setting of inconclusive TTE and TEE and offers a high sensitivity but comes at the cost of significantly increased invasiveness [ ]. Computerized tomography (CT) finds application in RSIE for detecting septic pulmonary infarcts and abscesses [ ].

Medical management

The foundation of medical management of RSIE is intravenous antibiotic therapy [ ]. Blood cultures should be obtained as soon as clinical suspicion for IE arises and should be repeated at 30-minute intervals to a total of three sets [ ]. In suspected RSIE patients with hemodynamic instability, empiric IV antibiotic therapy should be initiated immediately following blood culture draws [ ]. Empiric coverage should always include S. aureus and can be further guided in the IVD user by the type of drug and solvent abused as well as the location of the infection [ , , ]. Following culture and sensitivity results, antibiotics should be tailored to the causative organism [ , ]. Appropriate antibiotic therapy is effective in clearing bacteremia in 70%–85% of cases of tricuspid valve infective endocarditis (TVIE) [ ]. However, additional intervention may be necessary to address satellite sources of bacteremia, for example, lung decortication to treat pleural abscesses or empyema resulting from septic pulmonary emboli [ ]. The authors therefore advocate a scaled invasiveness approach to treatment of RSIE, with valve surgery reserved for cases in which less invasive procedures have failed to eliminate bacteremia.

Indications for surgery

Surgery for RSIE may be indicated by failure of medical management, risk of future adverse events, deteriorating patient condition, or a combination thereof. In the case of persistent fever or bacteremia 5–7 days following initiation of appropriate antibiotic therapy, surgery is indicated to remove the source vegetation [ , , , ]. Surgery in this case has the additional benefits of disrupting biofilms and exposing residual live organisms to on-going antibiotic therapy and immune response [ ]. Similarly, surgery may be required to treat cases of RSIE caused by organisms, such as fungi, that are difficult to eradicate by antimicrobial medications alone [ , , ]. Size and mobility of vegetations are also important factors dictating surgical intervention. Vegetations larger than 2 cm with high mobility and corresponding risk for embolization should be surgically excised [ , , , ]. While septic embolization to the lungs is an undesirable complication of RSIE, the literature and author experience suggest that pulmonary emboli should not be an indication for surgery in and of themselves [ ]. That said, recurrent septic pulmonary emboli can lead to increased pulmonary vascular resistance, reducing the ability of the right heart to pump out excess volume from tricuspid regurgitation and exacerbating regurgitation-based heart failure that may already be developing [ ].

Heart failure from severe tricuspid regurgitation is an independent indicator for surgery, particularly when refractory to diuretics [ , , , ]. Perivalvular abscesses and destructive penetrating lesions which are more commonly seen in prosthetic RSIE also require surgical intervention [ , , ]. Furthermore, if endocarditis or associated inflammation spread into the conduction system of the right heart, heart block can necessitate surgery for both vegetation resection as well as potential pacemaker implantation [ , ]. When concomitant LSIE is present, typically the circumstances of the LSIE dictate the need for surgery [ , ]. Once the need for surgery has been established, the operation should be performed within 48 h as early surgery has been demonstrated to improve outcomes [ , ].