Bacteremia Appears to Increase 30-Day Risk of MI or Stroke

Patients who had bacteremiamainly urinary-tract infections, pneumonia, or sepsiswhen admitted to hospital were much more likely to have an MI or stroke within 30 days, compared with healthy controls or patients hospitalized for other reasons, in a new study.


“Our study corroborates that acute infection may trigger cardiovascular events,” Dr Michael Dalager-Pedersen(Aalborg University Hospital, Denmark) told heartwire in an email. “It is the first study to demonstrate that many different bacterial infections may affect MI and stroke risk,” he added.


The research suggests that “bacteremia (a severe and acute infection) should be considered a risk factor for MI and stroke, but only for a short period of time after onset of infection,” and it hints that infection with Staphylococcus aureus may confer a particularly high risk.


“Patients admitted with signs of acute infection and bacteremia/sepsis should be monitored closely for complications, and treated early . . . with fluid therapy, oxygen, and antibiotics,” Dalager-Pedersen continued. “Moreover, it seems prudent to increase vaccination efforts (eg, influenza and pneumococcal vaccination), in particular in patients who already have established cardiovascular disease, since infection may trigger new cardiovascular events.”


Future studies are needed to clarify whether specific cardiovascular therapies (eg, antithrombotic or anti-inflammatory drugs) may reduce the risk of cardiovascular complications in patients with bacteremia, he said.


The study was published online February 12, 2014 in Circulation.


Infection a Trigger for MI, Stroke

An estimated one million Americans have an acute MI or stroke each year, and it would be useful to understand how acute infections might trigger these events, but most previous studies lacked laboratory confirmation of infection, the researchers write.


Using population-based databases, they identified 4389 patients in Northern Denmark who had positive blood cultures when admitted to hospital from 1992 to 2010. The pathogens were Escherichia coli, Streptococcus pneumoniae, S aureus, other bacteria, and fungi. Most patients had urinary-tract infections or pneumonia, while others had central nervous system infections, endocarditis, and other infections.


The mean age of patients was 73 years. Based on age, gender, and date of admission, each patient was matched with about five patients hospitalized for other reasons and about 10 individuals in the general population.


Researchers identified all incident MI and stroke events that occurred within 0 to 30 days, 31 to 180 days, and 181 to 365 days after the day of hospitalization.


Patients with community-acquired bacteremia had a greatly increased risk of MI or stroke within 30 days. At 31 to 180 days, these patients had a modestly higher risk of MI or stroke compared with healthy controls, but not compared with other hospitalized patients. No differences in cardiovascular risk were seen after more than six months.


“I was surprised by the magnitude of increased risk for AMI and stroke in bacteremia patients, especially because the risk was increased in all the examined subgroups,” said Dalager-Pedersen.


“An important step in improving the prognosis for patients with severe acute infection is to recognize the association between acute infection and MI/stroke, in order to raise the level of suspicion for vascular complications and diagnose and treat these complications at an early stage.”


Call for Improved Vaccination Rates, More Studies

“If Dalager-Pedersen and colleagues’ results are accurate and generalizable it is likely that 30 000 to 40 000 new strokes or MIs occur after bacteremia each year in the US,” Dr Allan J Walkey (Boston University School of Medicine, MA) writes in an accompanying editorial [2].


“Adding in previously described risks of cardiovascular events following pneumonia or urinary-tract infection, we estimate that 5% to 10% of acute MIs or strokes may be associated with acute infection.”


The study identified that ” ‘being sick’ in general was not the only mechanism for increased risk” of MI or stroke, Walkey observed.


Like the study authors, he calls for improved vaccination rates and more research. “Increased efforts should be made to improve suboptimal vaccination rates among patients with cardiovascular disease . . . [and] further mechanistic studies and large randomized trials would be required to assess whether antiplatelet, beta-blocker, or statin therapies might result in lower cardiovascular complications and possibly better outcomes after acute infection.”


The researchers reported no conflicts of interest. Walkey received funding from the National Heart, Lung, and Blood Institute for a study on atrial fibrillation in sepsis.

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