By Michael H. Crawford, MD

Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco

Dr. Crawford reports no financial relationships relevant to this field of study.

SYNOPSIS: In a comparison of patients with infective endocarditis (IE) and either bicuspid aortic valve (BAV) or mitral valve prolapse (MVP) vs. other IE patients at high or low-to-moderate risk of IE, BAV and MVP patients were more likely to exhibit viridans group streptococci infections of suspected odontogenic origin and cardiac complications at similar rates to high-risk patients.

SOURCES: Zegri-Reiriz I, de Alarcón A, Muñoz P, et al. Infective endocarditis in patients with bicuspid aortic valve or mitral valve prolapse. J Am Coll Cardiol 2018;71:2731-2740.

Chambers JB. Antibiotic prophylaxis against infective endocarditis: Widening the net? J Am Coll Cardiol 2018;71:2741-2743.

There are growing data regarding an increase in infective endocarditis (IE) in those at moderate risk who are excluded from antibiotic prophylaxis (AP) prior to nonsterile procedures. Zegri-Reiriz et al evaluated patients with bicuspid aortic valve (BAV) and mitral valve prolapse (MVP) with IE to learn more about the potential use of AP in patients with these intermediate risk conditions.

Patients with IE from 31 Spanish hospitals were entered into a registry from 2008-2016 (n = 3,524; 316 patients with isolated device-related IE eventually were excluded). After exclusion, 3,208 patients remained, of whom 1,226 were high risk and 1,982 were low-to-moderate risk. Among the 1,982 low-to-moderate risk patients remaining, Zegri-Reiriz et al considered an additional 143 patients from this group separately (n = 54 BAV patients and n = 89 MVP patients). Major adverse IE events were heart failure, embolism, persistent bacteremia, and intracardiac complications. The likely portal of bacteria entry was identified prospectively. The main analysis was a comparison of the clinical features of BAV and MVP IE patients to those at high risk and low-to-intermediate risk of IE. In patients with BAV or MVP, the most common organism detected was viridans group streptococci, which was about three times more common than that observed in the high-risk and remaining low/moderate-risk groups (39% vs. 13%; P < 0.01).

An odontological portal of entry also was more common in the BAV/MVP group than in the remaining patients (17% vs. 6%; P < 0.01). By contrast, staphylococci were the most frequently detected organisms in the high-risk and the remainder of the low/moderate-risk groups (P < 0.01) and was more likely nosocomial in these groups. BAV and MVP patients demonstrated similar rates of intracardiac complications as the high-risk patients, both of which were higher than in the low/moderate-risk patients (50% BAV/MVP and 47% high risk vs. 31% low to moderate risk; P < 0.01). The authors concluded that IE patients with BAV or MVP have more viridans group streptococci infections from odontologic sources than other IE patients and a clinical profile similar to high-risk IE patients. These data suggest that these two lesions should be considered high risk for AP consideration.

COMMENTARY

As more data accumulate, the controversy over the 2007 AP guidelines to prevent IE intensifies. A recently published study from the United Kingdom showed that during a five-year follow-up, many patients considered at moderate risk for IE developed IE at a similar frequency or higher than those considered at high risk by the guidelines.1 Those authors concluded that the guidelines should be changed to recommend IE prophylaxis for patients with electrophysiology devices, hypertrophic cardiomyopathy, congenital valve disease, and nonrheumatic valve disease. As this U.K. study was based on administrative data, few clinical details were available. BAV and MVP patients were included in the congenital and nonrheumatic valve disease categories, respectively, but there were no specific details on these common conditions. Thus, the Zegri-Reiriz et al study of BAV and MVP patients is of interest.

The Zegri-Reiriz et al study is the largest series to date regarding IE in BAV and MVP patients. Participants were relatively young, male, and had few comorbidities. However, these participants exhibited cardiovascular complications at rates similar to patients with high-risk conditions (BAV, 50%; MVP, 47%; high risk, 45%) and significantly higher than low/moderate-risk IE patients. Also, the MVP/BAV patients had high rates of viridans group streptococci IE and of suspected odontologic origin. In addition, the number of BAV patients sent to surgery was high (68%). MVP patients were sent to surgery at rates similar to the low/moderate-risk group (39%), but 66% left the hospital with severe mitral regurgitation. Given the equivalent or worse outcomes of IE in BAV and MVP patients, the authors believed that this indirectly supports including these patients in the AP recommendations.

The major strengths of this study were the large number of patients and complete microbiologic data. However, there were weaknesses, including the lack of AP data. Since Zegri-Reiriz et al recruited patients after the 2007 guidelines were released, presumably the high-risk patients underwent AP and the low/moderate-risk patients did not. Also, odontologic origin was not divided into subcategories, such as dental procedures and poor dentition. Additionally, this was a study of hospitalized patients with IE. We do not know the denominator; thus, IE incidence or prevalence cannot be determined. However, we know from other studies that IE in BAV patients is 30 times higher than the general population, and MVP is the most common underlying condition for IE in developed countries. If the AP guidelines are ever revised, perhaps patients with BAV and MVP (especially those with moderate or greater valvular regurgitation) should be included in the high-risk group and considered candidates for AP.

REFERENCE

  1. Thornhill MH, Jones S, Prendergast B, et al. Quantifying infective endocarditis risk in patients with predisposing cardiac conditions. Eur Heart J 2018;39:586-595.