Silent Brain Infarcts Found in 3% of AFib Patients, Tied to Cognitive Decline

Mitchel L. Zoler

May 11, 2020

Patients with atrial fibrillation, even those on oral anticoagulant therapy, developed clinically silent brain infarctions at a striking rate of close to 3% per year, according to results from SWISS-AF, a prospective of study of 1,227 Swiss patients followed with serial MR brain scans over a 2 year period.

The results also showed that these brain infarctions — which occurred in 68 (5.5%) of the atrial fibrillation (AFib) patients, including 58 (85%) who did not have any strokes or transient ischemic attacks during follow-up — appeared to represent enough pathology to link with a small but statistically significant decline in three separate cognitive measures, compared with patients who did not develop brain infarctions during follow-up.

"Cognitive decline may go unrecognized for a long time in clinical practice because usually no one tests for it," plus "the absolute declines were small and probably not appreciable" in the everyday behavior of affected patients, David Conen, MD, said at the annual scientific sessions of the Heart Rhythm Society, held online because of COVID-19. But "we were surprised to see a significant change after just 2 years. We expect much larger effects to develop over time," he said during a press briefing.

Another key finding was that roughly half the patients had large cortical or noncortical infarcts, which usually have a thromboembolic cause, but the other half had small noncortical infarcts that likely have a different etiology involving the microvasculature. Causes for those small infarcts might include localized atherosclerotic disease or amyloidosis, proposed Dr. Conen, a cardiologist at McMaster University, Hamilton, Ont.

This finding also suggests that, as a consequence, anticoagulation alone may not be enough to prevent this brain damage in Afib patients. "It calls for a more comprehensive approach to prevention," with attention to atherosclerotic cardiovascular disease risk factors in AFib patients, including interventions that address hypertension, diabetes, hyperlipidemia, and smoking cessation. "Anticoagulation in AFib patients is critical, but it also is not enough," Dr. Conen said.

These data "are very important. The two pillars for taking care of AFib patients have traditionally been to manage the patient's stroke risk and to treat symptoms. Dr. Conen's data suggest that simply starting anticoagulation is not sufficient, and it stresses the importance of continued management of hypertension, diabetes, and other medical and social issues," commented Fred Kusumoto, MD, director of heart rhythm services at the Mayo Clinic in Jacksonville, Fla.

"The risk factors associated with the development of cardiovascular disease are similar to those associated with the development of AFib and heart failure. It is important to understand the importance of managing hypertension, diabetes, and obesity; encouraging exercise and a healthy diet; and stopping smoking in all AFib patients as well as in the general population. Many clinicians have not emphasized the importance of continually addressing these behaviors," Dr. Kusumoto said in an interview.

The SWISS-AF (Swiss Atrial Fibrillation Cohort) study enrolled 2,415 AFib patients at 14 Swiss centers during 2014-2017, and obtained both a baseline brain MR scan and baseline cognitive-test results for 1,737 patients (J Am Coll Cardiol. 2019 Mar;73[9]:989-99). Patients retook the cognitive tests annually, and 1,227 had a second MR brain scan after 2 years in the study, the cohort that supplied the data Dr. Conen presented. At baseline, these patients averaged 71 years of age, just over a quarter were women, and 90% were on an oral anticoagulant, with 84% on an oral anticoagulant at 2-year follow-up. Treatment split roughly equally between direct-acting oral anticoagulants and vitamin K antagonists like warfarin.

Among the 68 patients with evidence for an incident brain infarct after 2 years, 59 (87%) were on treatment with an OAC, and 51 (75%) who were both on treatment with a direct-acting oral anticoagulant and developed their brain infarct without also having a stroke or transient ischemic attack, which Dr. Conen called a "silent event." The cognitive tests that showed statistically significant declines after 2 years in the patients with silent brain infarcts compared with those without a new infarct were the Trail Making Test parts A and B, and the animal-naming verbal fluency test. The two other tests applied were the Montreal Cognitive Assessment and the Digital Symbol Substitution Test.

Results from several prior studies also indicated a relationship between AFib and cognitive decline, but SWISS-AF is "the largest study to rigorously examine the incidence of silent brain infarcts in AFib patients," commented Christine M. Albert, MD, chair of cardiology at the Smidt Heart Institute of Cedars-Sinai Medical Center in Los Angeles. "Silent infarcts could be the cause, at least in part, for the cognitive decline and dementia associated with AFib," she noted. But divining the therapeutic implications of the finding will require further investigation that looks at factors such as the impact of anticoagulant type, other treatment that addresses AFib such as ablation and rate control, the duration and type of AFib, and the prevalence of hypertension and other stroke risk factors, she said as a designated discussant for Dr. Conen's report.

SWISS-AF received no commercial funding. Dr. Conen has been a speaker on behalf of Servier. Dr. Kusumoto had no disclosures. Dr. Albert has been a consultant to Roche Diagnostics and has received research funding from Abbott, Roche Diagnostics, and St. Jude Medical.

Heart Rhythm Society (HRS) 2020 Scientific Sessions.

This article first appeared on MDEdge.com.

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