NEW YORK (Reuters Health) - Lower systolic blood pressure in patients being treated for hypertension is associated with a reduced risk of atrial fibrillation (AF), according to data from the LIFE study.
"Among hypertensive patients at high risk of atrial fibrillation who can tolerate lower systolic blood pressure (SBP) levels, treating to a SBP of 130 or less may be able to reduce or retard the incidence of new AF," Dr. Peter M. Okin from Weill Cornell Medical College, New York, told Reuters Health by email, "but caution should be used when treating to these lower SBP levels to make sure that we are not harming patients in other ways."
Although hypertension clearly increases the risk of AF, studies have not consistently shown that reductions in blood pressure can reduce that risk.
Dr. Okin's team used data from the Losartan Intervention For Endpoint (LIFE) hypertension study to examine whether lower achieved SBP (no greater than 130 mm Hg) is associated with a lower incidence of AF compared with typical SBP control (131-141 mm Hg) and less-adequate SBP control (>=142 mm Hg) in hypertensive patients with left ventricular hypertrophy on ECG.
The post hoc study included more than 8,800 men and women whose age averaged 67 years.
Compared with the group with less-adequate SBP control, patients with typical SBP control had a 24% lower risk of developing AF. And patients with lower achieved SBP had a 40% lower risk, the researchers report in Hypertension, online June8.
Only at SBP levels <=125 mm Hg was lower SBP no longer associated with a significantly reduced risk of AF.
When SBP was included as a continuous variable in multivariate analyses, every 10-mm Hg decrease in SBP was associated with a 13% lower risk of new-onset AF.
"There are a number of concerns with regards to lowering SBP to these levels in older hypertensives," Dr. Okin cautioned. "First, there are a number of studies (including data from the LIFE study that we have published) that suggests that achieving lower target SBP levels can be associated with an increased mortality risk. Indeed, the most recent US guidelines for treatment of hypertension suggest treating to higher SBP goals in patients 60 years of age and older because of some evidence that treating to lower SBP levels may increase as opposed to decrease risk. However, there is significant disagreement regarding these new recommendations."
"Additional data from the LIFE study, that have been presented but not published in manuscript form, seem to support the notion that achieving SBP levels <140 in this patient population is associated with worse outcomes than a SBP between 140 and 149," he said. "Lastly, lower SBP levels in truly elderly patients can sometimes be associated with light-headedness and an increased risk of falling which can add additional morbidity."
Dr. Okin cautioned, "These findings are based on post-hoc analysis of data from a study that was not specifically designed to address this question. As a consequence, we should use caution when interpreting these findings until there are hopefully more specific studies that address the question of whether treating to a lower SBP goal can reduce the risk of developing new AF."
Dr. Kazem Rahimi from University of Oxford's George Institute for Global Health in the UK showed in a recent meta-analysis that antihypertensive therapy modestly reduced the risk of AF.
"There may be a greater risk of adverse events with very aggressive blood pressure control," Dr. Rahimi, who was not involved in the new study, told Reuters Health by email.
"In a trial (ACCORD), which targeted a blood pressure level of <120 mm Hg, BP reduction increased the risk of serious adverse events, particularly increasing the risk of hypotension and hyperkalemia," he said. "However, at the target blood pressure levels that the authors examined (<130 mm Hg SBP), the benefits of blood pressure lowering in older patients (preventing heart attacks and strokes) are likely to outweigh any risks."
Dr. Rahimi said the new analysis is unlikely to change clinical practice due to its observational nature. "However, in the context of randomized trials showing that blood pressure lowering prevents heart attacks and strokes in elderly hypertensive patients, the suggestive evidence from this and other studies that lowering blood pressure may also lower the risk of AF provides another reason for not withholding blood pressure lowering drugs."
The LIFE trial was sponsored by Merck & Co. The authors of the new report disclosed multiple ties to the company, including employment.