Low BP in patients with AF may be harmful

For patients with atrial fibrillation, the optimal BP target may be higher than that for the general population, according to new findings from the AFFIRM study.

Researchers conducted a post-hoc analysis of patients with AF and at least one risk factor for stroke who participated in the AFFIRM trial (n=3,947). In that trial, patients were randomly assigned to a rate-control strategy or a rhythm-control strategy.

Optimal BP in patients with AF had not been studied or addressed in guidelines, so the researchers sought to determine the relationship between BP and all-cause mortality in the AFFIRM participants, Nileshkumar J. Patel, MD, of Staten Island University Hospital, Staten Island, N.Y., told Cardiology Today.

Nileshkumar J. Patel

Optimal target differs

While the report of the Seventh Joint National Committee stated that systolic BP <120 mm Hg/diastolic BP <80 mm Hg was optimal, “studies have been done in the past that show this target BP may not be applicable for each and every patient,” Patel said in an interview. “It has been shown that for patients with ACS or CAD or stroke, there is not a linear relationship between BP and mortality; they found a J-shaped relationship. We thought this might hold true for patients with AF, because they are different from the general population and from hypertensive patients. We thought it might have clinical implications because most of the medications used for rate control and rhythm control also lower BP. By giving more and more medications, are we helping the patient or are we actually harming the patient?”

The primary outcome of the study was all-cause mortality. The secondary outcome was a composite of all-cause mortality, ventricular tachycardia and/or ventricular fibrillation, pulseless electrical activity, significant bradycardia, stroke, major bleeding, MI and pulmonary embolism.

During the mean follow-up period of 42.4 months, 15.6% of participants died, according to the researchers.

Patel and colleagues demonstrated via a nonlinear Cox proportional hazards model that the nadir BP for the complete cohort resulting in the lowest incidence of all-cause mortality was 140 mm Hg systolic/78 mm Hg diastolic.

Risk at either extreme

Compared with patients who achieved systolic BP 130 mm Hg to 140 mm Hg, the risk for all-cause mortality increased by 3.9-fold in those with systolic BP ≤110 mm Hg and increased by 1.9-fold in those with systolic BP >160 mm Hg (P<.001 for both). Compared with patients who achieved diastolic BP >80 mm Hg to 90 mm Hg, the risk for all-cause mortality increased by 3.9-fold in those with diastolic BP ≤60 mm Hg (P<.001) and increased by 1.8-fold in those with diastolic BP >90 mm Hg (P=.02).

The secondary outcome occurred in 24.6% of participants, according to the researchers. Compared with patients who achieved systolic BP 130 mm Hg to 140 mm Hg, the risk for the secondary outcome increased by 2.4-fold in those with systolic BP ≤110 mm Hg (P<.001) and by 1.5-fold in those with systolic BP >160 mm Hg (P=.02). Compared with patients who achieved diastolic BP >80 mm Hg to 90 mm Hg, the risk for the secondary outcome increased by 2.5-fold in those with diastolic BP ≤60 mm Hg (P<.001) and by 1.5-fold in those with diastolic BP >90 mm Hg (P=.04).

“Another interesting finding is that in this population with AF, if systolic BP goes below 110 mm Hg or diastolic BP goes below 60 mm Hg, the mortality risk is even higher than that for people with high BP,” Patel told Cardiology Today. For both systolic and diastolic BP, the group with the lowest BP had greater mortality than the group with the highest BP (HR=3.9; P<.001 for both).

Results were similar between the rate-control and rhythm-control groups, he said.

Because this was a retrospective study, the researchers could not definitively state why patients with AF are vulnerable when their BP is low. However, they said possible reasons include inadequate perfusion to the heart, increased risk for ventricular ischemia and inadequate blood flow to other organs.

“Because this is a retrospective study, this study will not change management right away, but it might spur researchers to further investigate this relationship,” researcher Raul D. Mitrani, MD, director of cardiac electrophysiology at University of Miami Miller School of Medicine, said in an interview. “Furthermore, clinicians may opt to be more cautious in uptitrating medications to control AF in patients who already have BPs in the low range of normal. Besides medications, there may be other nonpharmacologic means to control AF in select patients.”

Another researcher, Abhishek J. Deshmukh, MD, cardiologist at Mayo Clinic, added that “managing BP could be a double-edged sword and the need to find a sweet spot to reduce AF recurrences and prevent strokes should be studied prospectively.” – by Erik Swain

For more information:

Badheka AO. Am J Cardiol. 2014;114:727-736.

Abhishek J. Deshmukh, MD, can be reached at Mayo Clinic, 200 First St. SW, Rochester, MN 55905; email: abbishek_mbbs@yahoo.com.

Raul D. Mitrani, MD, can be reached at University of Miami Hospital, 1400 NW 12^th Ave, Suite 4062, Miami, FL 33136; email: rmitrani@med.miami.edu.

Nileshkumar J. Patel, MD, can be reached at Staten Island University Hospital, 212 N. Rail Road Ave., Apt. 1C, Staten Island, NY 10304; email: dr.nilesh.j.patel@gmail.com.

Disclosure: Deshmukh, Mitrani and Patel report no relevant financial disclosures.