Microalbuminuria, Retinopathy Predict AF
DALLAS—Microalbuminuria and microvascular abnormalities in the retina are independently associated with a higher risk of atrial fibrillation (AF). The two together increase the risk of AF by more than 20-fold, Sunil K. Agarwal, MD, MPH, PhD, reported at the American Heart Association's Scientific Sessions 2013.
“The processes that change small vessels in the heart should probably change the vessels of other organ systems,” said Dr. Agarwal in explaining the rationale for the study. “We wanted to see how micro-vessel changes in the eyes and also albumin in the urine, meaning that two different organ beds are involved, were related to development of AF.”
Dr. Agarwal and his colleagues analyzed data from the Atherosclerosis Risk in Communities (ARIC) database. The population-based ARIC study included a biracial cohort of 16,000 middle-aged men and women from four U.S. communities. Participants had retinal examinations and baseline measurement of urine albumin early in the study. After exclusions for missing data, missing potential confounders, and prevalent AF, the authors were left with 10,009 study subjects (56% women, 20% African American), 1,100 of whom developed AF over approximately 15 years of follow-up.
Of those with retinopathy at baseline, AF developed in 17.3%, compared with only 10.4% among those without retinopathy. After adjusting for age, race, sex, diabetes, blood pressure, other cardiovascular risk factors, and prevalent cardiovascular disease, the risk of AF was increased by 37% with retinopathy at baseline.
“Retinal micro-hemorrhages are very strongly associated with developing AF, irrespective of confounders,” said Dr. Agarwal, a clinical investigator at Johns Hopkins University in Baltimore. “Small hemorrhages showed a 42% higher risk of developing AF independent of any other heart disease that develops. Aneurysms are associated with AF but once adjusted for events during the follow-up, they were no longer associated.”
The study revealed no significant association between other retinal microvascular signs (arteriovenous nicking, focal/generalized narrowing or central retinal arterial equivalent) and incident AF.
“There were only 27 people who had both albumin in the urine and retinopathy. Out of them, 45% developed AF,” he said.
The incidence rates of AF were 24.4, 16.8, 8.9, and 5.7 per 1,000 person-years for those with retinopathy and microalbuminuria, microalbuminuria only, retinopathy only, and neither, respectively.
“We know that AF is often hidden [paroxysmal], and people don't have symptoms, and it's associated with an almost fivefold risk of stroke. We are able to reduce this risk by more than 60% with use of appropriate therapy,” Dr. Agarwal said. “All of this leads to thinking that if somebody finds retinopathy or microalbuminuria, they should think about whether the patient has AF or might develop AF.”
Autonomic nervous system dysfunction may also play a role in AF development, he said. “People who have small vessel disease may also have damage to their autonomic nervous system, which may increase their risk of AF downstream.”
In a separate analysis of the ARIC database he presented here, chronic kidney disease (CKD) was found to increase the risk of sudden cardiac death. Even a moderate reduction in kidney function (stage 3 CKD) increased this risk by about fivefold.