Current neurological mortality rates in infectious endocarditis

Dear Editor:

Infectious endocarditis (IE) is a serious disease with a high global mortality rate, despite the advances made in diagnosis and treatment over the last few years.¹ Neurological complications (NC) are frequent and constitute one of the main causes of morbidity and mortality. Their incidence ranges from 20% to 40% depending on the series.²

The aim of this clinical note is to present the NC incidence and global and specific mortality due to neurological causes observed in a current consecutive series of patients with IE treated in a tertiary hospital.

To that end, we carried out a prospective review of all patients diagnosed with IE according to the modified Duke criteria³ who died in Hospital Universitario Donostia (HUD) and Policlínica-Gipuzkoa in San Sebastián. The study period was March 2008 to December 2010. The HUD has 1150 beds and provides care to 350 000 inhabitants. It is also the tertiary hospital of reference for the whole province of Guipúzcoa. IE was diagnosed and IE surgery was indicated according to the criteria established by European guidelines.⁴ NC was diagnosed based on the patient's symptoms and confirmed using CT or MRI neuroimaging tests.

Between March 2008 and December 2010, 104 cases of IE were diagnosed. Seventeen of these patients died (16.3%): five (29.4%) due to neurological causes and the remaining twelve due to other causes.

The five patients who died of a neurological cause comprised three men and two women; mean age was 73 years and meticillin-sensitive Staphylococcus aureus was the microbial cause of death in four cases (80%). The mitral valve was involved in two cases and the aortic valve in another two, with both mitral and aortic involvement observed in the fifth case. Neurological cause of death was ischaemic stroke in four patients (80%), as well as being the reason for admission in two cases. The remaining patient (20%) died of haemorrhagic stroke. Average elapsed time between admission and death was 21 days. Two patients had undergone prior surgery (40%).

Of the 104 patients, neurological symptoms were identified in 19 (18.3%) and seven patients in that group died. Mortality in the group of patients with NC was 36.8%, compared to 11.76% (10/85) in the patient group with no neurological symptoms.

These results show that despite advances in NC diagnosis, antibiotic treatments, and early surgical intervention, the disease is currently a major cause of in-hospital mortality and morbidity.

Systematic use of CT or MRI neuroimaging techniques in several studies has shown that CNS involvement in cases of IE is far more frequent than expected, reaching 80% in some series.^5–7 Involvement of the CNS can influence diagnosis, prescription of antibiotic treatment, and the indication for surgery in IE cases. Duval et al. showed that early systematic use of head MRI scans modified the diagnostic classification and the treatment approach in 28% of the cases in a series of 130 patients.⁵ However, it remains to be determined whether modifications following diagnosis of subclinical neurological involvement can alter the course of IE and patient prognosis. In addition, current guidelines do not recommend systematic use of neuroimaging techniques in managing IE.

S. aureus is the causative agent associated with a higher incidence of cerebrovascular events, both symptomatic and asymptomatic.^2,6,8 Some authors believe that it could be very useful to systematically perform neuroimaging tests in cases of IE due to S. aureus, although there is no evidence to support this.

In short, NC accounts for a high percentage of morbidity and mortality in IE and further studies are needed to help determine if the systematic use of MRI can modify the treatment approach for these patients and thus decrease both NC-related morbidity and general and neurological mortality in IE.