AF, Carotid Disease Synergistic for Risks for Stroke, Dementia

July 29, 2019

The presence of atrial fibrillation (AF) and carotid artery disease in the same person predicts greater risks for stroke and dementia than either condition would alone, suggests a study of more than 11,000 patients from a single large health system.

Notably in the analysis, the risk for dementia dropped after either catheter ablation of AF or revascularization of carotid disease. But of the two treatments, only AF ablation was followed by a reduction in risk for cerebrovascular events.

"Our study is one of the largest ever done, with the longest follow-up, of patients with either carotid disease or AF or both conditions," T. Jared Bunch, Intermountain Medical Center, Murray, Utah, told Medscape Medical News.

"We saw a critical synergistic link between AF and carotid disease and the risk of developing dementia," said Bunch, who is lead author on the study, published July 9 in Heart Rhythm.

Patients with both AF and carotid disease, he said, showed "an early and persistent increased risk of dementia compared with patients who had AF alone or carotid disease alone."

Of note, Bunch added, "we also saw benefits of treatment of these conditions on the risk of dementia. In particular, we found a significant impact of ablation of AF on reducing both stroke and dementia. And the relative benefit of ablation was greatest in AF patients who also had carotid disease."

Doctors need to be aware of these links, he said. "In AF patients who develop signs of dementia, maybe we should look at their carotids to reduce this risk. And patients with carotid disease starting to show cognitive decline should be checked for AF. If they are found to have both conditions, then there is even more reason to do an ablation."

In practice, Bunch said, sicker patients, including those with vascular disease and previous stroke, are less likely to be referred for ablation if they have AF. "But our results suggest that these sicker patients may actually gain the most benefit from AF ablation. So the procedure should not be withheld from these patients."

Bunch explained that AF has been linked to dementia in previous studies. "As well as the obvious stroke-related dementia, AF is also associated with Alzheimer's and other types of dementia," he observed.

"There is also a group of patients who report cognitive decline almost immediately after they develop AF, and this cannot be explained just by a clot. There seems to be an acute hemodynamic effect in the brain. We are trying to understand more about that," Bunch said.

"We know the brain has the ability to compensate when it is under hemodynamic stress, such as that caused by AF. When the vasculature is healthy, it might be able to compensate for this. But we wondered about patients with carotid disease and whether this affects the brain's ability to compensate for AF."

The researchers case-matched four groups of patients from their health system who were categorized according to their AF and carotid disease status. There were 2893 adults in each group: those with AF, those with carotid disease, those with both conditions, and those with neither.

The groups were matched for age, sex, hypertension, diabetes, coronary artery disease, and previous stroke, and were tracked for incident stroke or transient ischemic attack (TIA) and dementia.

Over a follow-up of 5 to 7 years, baseline carotid disease increased the risk for stroke/TIA (hazard ratio [HR], 2.74; P < .0001) and dementia (HR, 1.44; P < .0001), compared with having neither carotid disease nor AF. Similarly, AF increased the risk for stroke/TIA (HR, 2.08; P < .0001) and dementia (HR, 1.30; P = .004).

The coexistence of AF and carotid disease augmented risk for stroke/TIA (HR, 3.09; P < .0001) and for dementia (HR, 1.39; P = .001).

Risks for the composite end point of stroke, TIA, and dementia were similarly increased for the same comparisons by baseline AF and/or carotid disease.

Carotid revascularization, as indicated, was associated with a decreased 5-year risk for dementia (HR, 0.47; 95% CI, 0.27 - 0.81; P = .007), even after adjustment for demographics, medications, and clinical features.

In multivariate analysis, ablation for AF was associated with a reduced risk for dementia (HR, 0.51; 95% CI, 0.27 - 0.96; P = .04) and for stroke/TIA overall (HR, 0.55; 95% CI, 0.38 - 0.81; P = .002), and solely among patients who also had carotid disease (HR, 0.36; 95% CI, 0.21 - 0.61; P = .0001).

"These data confirm prior studies that have shown carotid disease to be an independent risk factor for stroke in patients with and without AF," the authors write.

The findings also "expand these prior studies to include dementia as part of the spectrum of disease states associated with cerebral injuries in patients with and without AF."

Bunch cautioned that the findings from the observational study are only hypothesis-generating, and therefore "need to be confirmed in a prospective study. However, observational studies have their strengths too. This is a real-life view of routine practice in a large number of patients. This is the largest study available to look at these questions."

Bunch discloses receiving research grants from Boehringer Ingelheim and Boston Scientific. Disclosures for the other authors are in the report.

Heart Rhythm. Published online July 9, 2019. Abstract

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