Because many of the patients with right-sided IE develop infection as a result of IDU (see the Right-Sided IE in IDUs section), the general approach is to treat these patients Table 17. Direct Evidence Supporting an Association Between Valve Surgery and Lower Mortality From Observational Studies: Level of Evidence B Study Mortality IE Group PE vs SA Lalani et al10 In-hospital mortality NVE PE Bannay et al15 5-y mortality NVE+PVE PE Kiefer et al11 In-hospital and 1-y mortality CHF (NVE+PVE) PE Lalani et al10 In-hospital mortality Paravalvular complications (NVE) SA Bannay et al15 5-y mortality Intracardiac abscess (NVE+PVE) SA Lalani et al10 In-hospital mortality Systemic embolization (NVE) SA Bannay et al15 5-y mortality Systemic embolization (NVE+PVE) SA Lalani et al10 In-hospital mortality S aureus (NVE) SA Bannay et al15 5-y mortality CHF (NVE+PVE) SA Lalani et al259 In-hospital and 1-y mortality PVE with the highest propensity to undergo surgery SA CHF indicates congestive heart failure; NVE, native valve infective endocarditis; PE, primary end point; PVE, prosthetic valve infective endocarditis; and SA, subgroup analysis. All studies have adjusted for selection and survivor bias and confounding. Valve surgery was performed during the active phase of the disease (during initial hospitalization before completion of a full therapeutic course of antibiotics). Baddour et al Infective Endocarditis in Adults 1467 medically and to avoid placement of valve prostheses because of the subsequent risk of device infection with continued IDU. Surgical intervention is reasonable for patients with the fol- lowing complications: right heart failure secondary to severe tricuspid regurgitation with poor response to medical therapy, sustained infection caused by difficult-to-treat organisms (ie, fungi, multidrug resistant bacteria) or lack of response to appropriate antimicrobial therapy, and tricuspid valve vegeta- tions that are 20 mm in diameter and recurrent pulmonary embolism despite antimicrobial therapy. 