Infective Endocarditis Often Missed in At-Risk Patients

Diana Mahoney

November 08, 2012

BOSTON, Massachusetts — Men are more likely than women to be affected by infective endocarditis (IE), and left-sided disease is more common than right-sided disease. These findings come from a 12-year autopsy review designed to assess the pathology of the inflammatory condition and to determine how frequently the diagnosis is not made when the patient is alive.

Furthermore, at autopsy, a disproportionate number of black IE patients were infected with methicillin-resistant Staphylococcus aureus (MRSA), and a "surprising" number of patients were dialysis-dependent, lead investigator Yaolin Zhou, MD, a resident in the Department of Pathology at the University of Alabama at Birmingham, reported here at the American Society for Clinical Pathology 2012 Annual Meeting.

The most disturbing finding, Dr. Zhou told Medscape Medical News, is that despite advances in antimicrobial therapy and in diagnostic and surgical techniques in recent years, "many of the cases, and almost all of those involving right-sided endocarditis, were not diagnosed until autopsy."

For their study, Dr. Zhou and colleagues reviewed all autopsy reports from their institution issued from January 2000 to March 2012. They identified 46 cases of IE and obtained patient demographic characteristics, clinical history, and cultured organisms from the autopsy report, and supplemented missing data with a review of the patients' original medical records.

Of the 46 patients (median age, 54 years; range, 20 to 78), 36 were male and 23 were black. MRSA was identified as the causative organism in 17 patients overall (37%) and in 11 of the 23 black patients (48%), Dr. Zhou reported. Other prevalent causative organisms included nonresistant strains of S aureus (n = 5; 11%), resistant and nonresistant strains of Enterococcus (n = 6; 13%), and coagulase-negative Staphylococcus (n = 5; 11%). Streptococcus pneumoniae, Enterobacter cloacae, Serratia marcescens, Candida, group B streptococcus, and Stenotrophomonas maltophilia were also identified. Three cases were culture-negative, and 3 were infected with multiple organisms.

With respect to endocardial involvement, 35 patients had evidence of left-side only endocarditis and 7 had right-side only endocarditis. "Multiple valve involvement was noted in 11 patients, including 4 patients with evidence of right- and left-sided [IE]," Dr. Zhou said during a poster presentation. At least 3 of the patients, including 1 with right-sided IE, were identified as intravenous drug users, she said. Other identified risk factors included hemodialysis (n = 17), recent infection (n = 15), surgical procedure (n = 15), damaged valves (n = 10), prosthetic valves (n = 10), immune compromise (n = 9), aortic regurgitation (n = 9), previous endocarditis (n = 8), hepatitis C liver cirrhosis (n = 7), and mitral regurgitation (n = 7).

Among the most common presenting signs and symptoms were altered mental status/headaches (n = 19), fever/chills (n = 16), chest and other pain (n = 15), dyspnea (n = 13), unstable vital signs (n = 7), gastrointestinal complaints (n = 7), and general weakness (n = 5), Dr. Zhou stated.

Right-Sided IE Presents With Atypical Symptoms

"Despite hospitalization, one third of these patients [n = 15; 32.6%] were not diagnosed until autopsy, including all but 1 of the cases involving the right side only," said Dr. Zhou. The reason for the significant and disproportionate difference in missed diagnoses among patients with right-sided IE might be the increased likelihood of nonclassic presenting symptoms, she hypothesized. Specifically, "right-sided murmurs often go undetected, and peripheral signs [such as Roth's spots, Osler's nodes, Janeway lesions, and splinter hemorrhages] are not there," she explained, noting that nonspecific respiratory symptoms seem to be more predominant in this population.

The disproportionate number of black patients infected with MRSA in this study is not surprising, given the high percentage (37%) of patients on hemodialysis, Dr. Zhou said. The prevalence of end-stage kidney disease (leading to dependence on dialysis) is more prevalent in the black population than in the general population, "and the risk for invasive MRSA infections is significantly higher in dialysis patients," she said.

Although the diagnosis of IE is challenging, particularly among those with right-sided disease, because of the variability in clinical presentation and the frequency of nonspecific symptoms, "a strong clinical suspicion should be entertained in patients who present with any of the identified risk factors," Dr. Zhou stressed, noting that early diagnosis, aggressive antibacterial therapy, and surgical treatment can improve the prognosis in affected patients.

Better Diagnosis and Management Needed

The findings of this study are consistent with those from previous studies, and point to the need for improvements in the diagnosis and management of patients at risk for IE, given the persistently high rate of morbidity and mortality associated with it, according to Andrew Wang, MD, professor of medicine and director of the cardiovascular disease fellowship program at Duke University Medical Center in Durham, North Carolina. Dr. Wang was not involved in the study.

The management challenge is exacerbated by changes that have occurred over the past 20 years; the "typical" case is no longer that of a middle-aged patient with a predisposing native valve condition and streptococcal infection, Dr. Wang told Medscape Medical News. Today, S aureus is more likely to be the causative organism, often in association with injection drug use, but also in dialysis-dependent patients and those with suppressed immune systems, he said. Reducing IE-associated morbidity and mortality requires better education about the risks for healthcare-associated infections, careful management of susceptible patients (including those with cardiac devices and significant comorbidities), multidisciplinary care (with a focus on appropriate antibiotic therapy and use of surgery), and more research on modifiable procedure-related risks and host characteristics, he explained.

Dr. Zhou has disclosed no relevant financial relationships. Dr. Wang reports financial relationships with Abbott Vascular, Edwards Lifesciences, Gilead Sciences, and Medtronic.

American Society for Clinical Pathology (ASCP) 2012 Annual Meeting: Poster 260 Presented November 3, 2012