Infective Endocarditis: Longer Than Expected Stroke Risk

Pauline Anderson

July 14, 2015

Infective endocarditis (IE) increases the stroke risk for much longer than previously thought, new findings suggest.

The study showed that the risk for stroke begins to increase about 4 months before a diagnosis of IE, peaks in the month after the diagnosis, and then normalizes by 5 months afterward.

"This is a 9-month period that patients with endocarditis are at risk for stroke, which is many months longer than was previously reported," lead author Alexander Merkler, MD, fellow in neuro critical care, Weill Cornell Medical College and New York-Presbyterian Hospital, New York, told Medscape Medical News. "In addition to that, the 1-month period after a diagnosis of endocarditis is extremely high."

Dr Alexander Merkler

The study was published online July 10 in Neurology.

"Huge" Increased Stroke Risk

From the California Office of Statewide Health Planning and Development, which collects data on state-wide emergency department visits and hospital stays at nonfederal acute care hospitals, researchers used validated codes to identify adult California residents hospitalized with IE between July 1, 2007, and June 30, 2011.

Among 17,926 patients with IE, 2275 developed a stroke during the12-month period surrounding the diagnosis of IE. Of these patients, 82.5% had an ischemic stroke, 13.7% had a hemorrhagic stroke, and 3.8% had both an ischemic and a hemorrhagic stroke.

Stroke risk was highest in the month after the diagnosis of IE compared with the same 1-month period 2 years earlier. This corresponded to an absolute increase in risk of 9.1% (95% confidence interval [CI], 8.6% - 9.5%) and an odds ratio [OR] of 96.5 (95% CI, 60.1 - 166.0).

The risk for stroke was significantly elevated from the fourth month before the IE diagnosis (OR, 3.1; 95% CI, 1.6 - 6.5) through the fifth month afterward (OR, 2.6; 95% CI, 1.4 - 5.2).

The risk for ischemic stroke was similar to that for all strokes in that it was highest in the month after the IE diagnosis, in this case corresponding to an absolute increase in risk of 7.6% and an OR of 80.9. As well, ischemic stroke risk increased in the fourth month before the IE diagnosis and persisted through the third month afterward.

A similar temporal pattern was found for hemorrhagic stroke, although the peak increase in absolute risk during the month after IE was more modest at 1.8%.

"Doctors should know that patients who have endocarditis are at a very, very elevated risk for stroke; we have found that they are 80 times more likely to have a stroke than those who don't have endocarditis, which is a huge increased risk," said Dr Merkler. "Also, the risk of stroke exists 4 months before and 5 months afterwards, which is long time. No one realized that until now."

Many factors may tie endocarditis to stroke, including inflammation, according to Dr Merkler. Having a prosthetic heart valve can lead to stagnant blood flow in the heart, which increases the risk for arrhythmias and for stroke, and also for endocarditis.

Two-Way Street

In patients with endocarditis, bacteria deposits on the heart valve can break off and travel to the brain, causing an ischemic stroke if they get lodged in the blood vessels or a hemorrhagic stroke if they cause blood vessels to burst.

"But it's probably a two-way street," said Dr Merkler. "Patients who have a stroke and are in the hospital get procedures like central lines and that increases the risk of endocarditis."

A stroke is often the first clinical sign of endocarditis. Dr Merkler referred to one patient who for months had experienced low-grade fevers and chills and had gone from doctor to doctor trying to get a diagnosis. "Finally, he presented with a stroke, so he probably had endocarditis for a long time, but wasn't actually given the diagnosis until the stroke occurred."

While aspirin or other blood thinners are given to most patients with ischemic stroke, this treatment is contraindicated in those whose stroke is from IE because of the elevated bleeding risk, said Dr Merkler. Patients with such a stroke are treated with antibiotics.

As the population ages and an increasing number of older patients get artificial heart valves, endocarditis is becoming much more common, said Dr Merkler.

Commenting on the study for Medscape Medical News, Ralph Sacco, MD, professor and chair, Department of Neurology, University of Miami Miller School of Medicine, Florida, said the results "widen the period of susceptibility" to stroke in patients with infective endocarditis.

Such studies, said Dr Sacco, are difficult to carry out. "Teasing apart the temporal relationships between stroke and the onset of IE is not easy."

He also pointed out that the authors relied on administrative databases, which have limitations.

"Although the stroke risk extended up to 4 months prior to IE diagnosis, it is not clear whether IE could have remained subclinical and stroke could have been the initial manifestation of IE."

The study was supported by the National Institute of Neurological Disorders and Stroke, a National Institutes of Health grant administered through the Weill Cornell Clinical and Translational Science Center, the Michael Goldberg Stroke Research Fund, and the Florence Gould Endowment for Discovery in Stroke. Dr Merkler has disclosed no relevant financial relationships.

Neurology. Published online July 10, 2015. Abstract

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