The study presented here examined the clinical course and prognosis for patients requiring admission to an ICU because of IE. To our knowledge it represents the first systematic analysis of this small but important subset of ICU patients and highlights the serious prognosis of patients with a complicated course of IE.
Cardiogenic and septic shock were the main reasons for intensive care treatment. Male preponderance and age distribution in this study were comparable to non-ICU series . All patients in this study had left-sided valvular endocarditis and the aortic valve was most commonly involved. PVE was frequent, which might be explained by the location of three of the participating ICUs in a university hospital environment. Surprisingly, no cases of right-sided IE were observed, which is reported to be frequent in intravenous drug abusers . The two patients with a history of intravenous drug abuse included in the series had left cardiac involvement.
In all the patients in the study with positive blood culture Gram-positive strains were present and Staphylococcus aureus was identified as the most prevalent pathogen. The proportion of culture-negative endocarditis in this cohort was slightly higher than in previous reports , which may be explained by the high incidence of antimicrobial pretreatment and by the fact that these patients tended to have a shorter illness duration making a detailed microbiologic evaluation more difficult. In a previous study, 62% of patients with culture-negative endocarditis had received prior antibiotic therapy compared to only 31% of patients with culture-positive endocarditis .
Previous studies also reported a worse prognosis in patients with IE secondary to infection with certain microorganisms such as Staphylococcus aureus . The study reported here failed to show an association between bacteriological findings and outcome. It is likely that any differences in mortality will diminish in the presence of a complicated clinical course of the disease.
The study also highlights the usefulness of the transesophageal echocardiography approach for diagnosis and risk stratification of IE. Transesophageal echocardiography was required in more than 90% of the patients, either to ascertain the pending diagnosis or to delineate the full extent of disease. Vegetations were seen by transthoracic or transesophageal echocardiography in 79% of the patients. In line with previous series, systemic embolism appeared to increase by more than fivefold in patients with vegetations >10 mm in size. Abscess formation was also a frequent finding on transesophageal echocardiography in this cohort of ICU patients.
The observed overall in-patient mortality of 54% in this series is high, but cannot be compared with data obtained in other series because the analysis here included only the patients with severest IE, who required admission to an ICU. Multivariate analysis showed that presence of acute renal failure on admission was the single independent greatest risk factor for a fatal outcome. More than half of the patients in the study underwent successful surgical treatment. In other series, which included patients with IE associated with severe heart failure, in-patient mortality after surgery reached 41% [12,13].
Patients admitted to an ICU as a result of a complicated course of IE, may frequently require acute cardiac surgery for correction of massive valvular regurgitation or for prevention of recurrent systemic embolism. Abscess drainage and/or removal of prosthetic endovascular material may be necessary for treatment of uncontrolled sepsis. Antibiotic pretreat-ment lasting for several days before cardiac surgery is recommended by some authors , but several of the patients in this study had to be operated on immediately after initiation of antibiotic therapy. Nevertheless, cardiac surgery is often deferred in the setting of severe shock and/or of multi-organ failure and patient transfer to a cardiac surgery facility may be associated with additional risks. The decision whether to perform acute surgery is particularly difficult in unconscious or sedated patients with an uncertain neurologic outcome. In the study series cardiac surgery was most often deferred in these patients.
In conclusion, our results show that despite improvements in diagnostic and surgical techniques, advances in antibiotic therapy and optimized critical care, IE still involves a poor prognosis once major complications such as heart failure, septic shock or recurrent systemic embolism have developed. Diagnostic work-up, including a complete transthoracic and transesophageal study, must be performed immediately in every patient admitted to an ICU with embolism, heart failure, cardiogenic or septic shock of unknown cause, as the data presented here suggest that prompt surgical intervention can be life-saving in patients with IE despite the presence of severe shock and the occurrence of multiorgan failure.