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Pneumonia-related atrial fibrillation (Afib) should not be considered a transient and benign finding, according to a Danish cohort study that showed that patients could be left with recurrent Afib and an increased thromboembolic risk if they didn't start anticoagulants.

Survivors of pneumonia had a 0.8% incidence of ischemic stroke and/or systemic arterial embolism at 1 year if they had no Afib, compared with 2.1% for peers who had developed new-onset Afib within a month after infection, reported Mette Søgaard, DVM, PhD, of Aalborg University Hospital in Denmark, and colleagues.

Over 3 years of follow-up, the risk remained relatively high for people with Afib not on oral anticoagulation -- reaching 5.3% among those with new-onset Afib and high baseline stroke risk, the authors noted in .

With these thromboembolic risk estimates, people with Afib after pneumonia may be candidates for warfarin and oral anticoagulant (OAC) therapy for stroke prevention, they suggested. "The question remains whether these patients should initiate lifelong OAC therapy."

In the study, 14.0% of the Afib group became new anticoagulant users during follow-up. Nearly one in three had a new hospital contact with documented Afib.

"This corroborates previous findings and suggests that restoration of sinus rhythm with resolution of infection may not protect against Afib recurrence. In this respect, infection may merely be a stress test that demonstrates the likelihood for future Afib," Søgaard and team wrote.

"These findings may have rhythm monitoring and treatment implications, and improved communication and monitoring of long-term Afib risks is warranted," they added.

Current guidelines do not provide clear directives on oral anticoagulants for people with Afib after an infection such as pneumonia. High-quality evidence is lacking, since this group had been excluded from most anticoagulation trials for stroke prevention.

COVID-19 patients in the ICU have also been found to develop atrial arrhythmias.

"In the era of non-vitamin K OAC therapy, perhaps it is time for infection-related Afib to be treated in the same way as non-infection-related Afib, with long-term anticoagulation maintained in patients with manifested clinical stroke risk factors," the authors wrote.

"However, the decision to initiate anticoagulation treatment in the setting of severe infections is complex," they cautioned. "High bleeding risk due to systemic activation of the inflammatory response and depletion of coagulation factors and platelets may outweigh the benefits of anticoagulation."

The population-based cohort study relied on Danish registries that captured patients hospitalized with incident community-acquired pneumonia in Denmark from 1998 to 2018. Søgaard and team analyzed 274,196 individuals who were alive and not receiving anticoagulation therapy.

Of this cohort, 6,553 had developed new-onset Afib (mean age 79.1 years, 52% women) by the landmark time point of 30 days after the index hospitalization.

Compared with patients with pneumonia without Afib, the Afib group had a greater prevalence of cardiovascular and noncardiovascular comorbidities. Most also had intermediate or high CHA₂DS₂-VASc scores.

All-cause mortality rates at 3 years were 49.8% in the Afib group and 25.7% in the group without Afib.

Søgaard's group acknowledged that the study may have missed patients who had Afib go undetected or unreported. There was also no information on duration and number of Afib episodes during pneumonia hospitalization, nor were there details on stroke type when one occurred.

Nevertheless, the authors said, the analysis "expands the evidence suggesting that there is an increased risk of thromboembolism in patients with infection-related Afib, and it adds to the notion that new-onset Afib should not be regarded as self-limiting and benign."

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