US researchers say they identified a possible link between a history of sudden drops in blood pressure and atrial fibrillation, or an irregular heartbeat. Dr. Sunil K. Agarwal, a fellow in the Division of General Internal Medicine at the Johns Hopkins University School of Medicine who led a study of patients who experience sudden drops in blood pressure, said the results suggest a bout of orthostatic hypotension -- a steep blood pressure drop that occurs when a person stands up after a period of lying down -- appears to be associated with an overall 40 percent increase in the risk of developing atrial fibrillation over the following two decades. "We hope our research will sensitize physicians to a possible link between orthostatic hypotension and atrial fibrillation, and that they will go the extra step to see if something more serious is going on when patients experience rapid blood pressure fluctuations," Agarwal said in a statement. "We want this on their radar screens." The researchers tracked 12,071 African-American and white men and women ages 45-64, who were enrolled in the Atherosclerosis Risks in Communities study beginning in 1987-89. Those who had a history or symptoms of atrial fibrillation at baseline were excluded from the study. Three follow-up visits were conducted, as well as annual telephone interviews and active surveillance of hospitalizations and death. Five percent of the subjects were diagnosed with a rapid drop in blood pressure when going from lying down to standing up. The study, published in the journal Plos One, found during an average follow-up of 18 years, 12 percent of the study participants developed atrial fibrillation. Those with orthostatic hypotension, after accounting for factors such as race, age, gender and other common risk factors for the arrhythmia, were 40 percent more likely than those without orthostatic hypotension to develop an irregular heartbeat, the study found.