By Michael H. Crawford, MD
This article originally appeared in the March 2015 issue of Clinical Cardiology Alert. It was peer reviewed by Susan Zhao, MD. Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco. He is the editor of Clinical Cardiology Alert. Dr. Zhao is Director, Adult Echocardiography Laboratory, Associate Chief, Division of Cardiology, Department of Medicine, Santa Clara Valley Medical Center. Dr. Crawford and Dr. Zhao report no financial relationships relevant to this field of study.
SOURCES: Chu VH, et al. Association between surgical indications, operative risk, and clinical outcome in infective endocarditis: A prospective study from the international collaboration on endocarditis. Circulation 2015;131:131-140; Erbel R. The new strategy in infective endocarditis: Early surgery based on early diagnosis: Are we too late when early surgery is best? Circulation 2015;131:121-123.
Although guidelines outline specific indications for surgery in infective endocarditis (IE), applying these recommendations in the clinical area is challenging. In order to understand these challenges, the International Collaboration on Endocarditis (ICE) conducted a prospective study to evaluate the factors that influence the decision with regard to surgical intervention in IE. From the ICE database, patients with left-sided IE enrolled between 2008 and 2012 were selected for this analysis. Among the 1296 patients, 314 (25%) had prosthetic valve IE. Surgery was performed in 733 (57%). Indications for surgery were heart failure, embolic event, persistent bacteremia, paravalvular complications, severe regurgitation, vegetation size, and microorganism type. Among the 863 with indications for surgery, 661 (77%) had surgery. Those undergoing surgery were younger compared to those who did not have surgery (57 vs 68 years, P < 0.001). Also, they more often had severe aortic regurgitation (odds ratio [OR] = 2.4), abscess (2.0), and embolic events (1.7). Factors associated with no surgery despite indications were liver disease (OR = 0.16), stroke (0.54), or Staphylococcus aureus (0.50). The reason cited for not operating with S. aureus was sepsis. The Society of Thoracic Surgeons (STS) preoperative risk score averaged 24 in those going to surgery. Surgery was associated with higher 6-month survival, and survival was related to the STS score. Surgical indications and an STS score above the median resulted in about a 90% 6-month survival; whereas, those with an STS below the median had about a 70% 6-month survival. Those with a surgical indication with an STS above the median and no surgery had the worst prognosis, < 30% 6-month survival. The authors concluded that the performance of surgery in patients with IE generally followed guidelines, except for patients with S. aureus. Despite S. aureus being the most common cause of IE in the current era and an indication for surgery in most guidelines, surgery was performed less often in S. aureus IE patients.
COMMENTARY
The widespread use of transesophageal echocardiography (TEE) in the last 20 years has markedly improved the sensitivity for detecting IE (now 96%) and its complications. However, mortality has not changed over the last 2 decades. Many believe that part of the reason mortality has not decreased with earlier diagnosis of the disease is that early surgery is often not done despite guideline recommended indications being present. In this study from the prospective, observational ICE database, 30-day mortality in those with indications for surgery who had surgery was 15% vs. 26% in those with indications for surgery in whom it was not done. Surprisingly, 25% of patients with indications for surgery did not get it. The major reasons for not doing indicated surgery were comorbidities that raised operative risk and S. aureus sepsis. Naturally, the STS score was higher than what would be encountered in other types of cardiac surgery, since healthy people rarely get IE. Also, STS score was related to outcome as one would expect. On the other hand, surgery can be lifesaving for patients unlikely to be cured by medial therapy.
In addition to being an observational study, there are other weaknesses of this study. It was conducted in large tertiary centers and half the patients were transferred from other hospitals. So there is likely a referral bias. Also, the study was done in several countries and not adjusted for differences in practice patterns. Finally, the data were not adjudicated centrally. On the other hand, randomized trials are unlikely to ever be done in IE. Also, this was a comprehensive study that looked at 275 clinical variables. Older studies demonstrated the benefits of surgery, but lacked the detailed information in this study.
This study emphasizes that early surgery before antibiotics have been able to fully work should be strongly considered when published indications are present, since successful surgery improves survival. When the STS score is < 24, the 6-month survival was excellent (about 90%). Even when the STS score was > 24, the 6-month survival was about 70%; lower but clearly better than the alternative of failed medical therapy.
