Low blood pressure may increase risk of heart attack and stroke

Data from the Treating to New Targets (TNT) trial presented today at the American Society of Hypertension's Twenty Fourth Annual Scientific Meeting (ASH 2009) show that low blood pressure levels may lead to increased risk of cardiovascular events, including heart attack and stroke. These data supplement previous findings from the TNT trial of atorvastatin showing aggressive LDL cholesterol-lowering reduced cardiovascular events.

Previous statistical analyses charting cardiovascular events have found a J-curve relationship exists between blood pressure and future cardiovascular events, where higher events were seen at the very low and very high blood pressure levels. However, there is some debate about the extent of this relationship in patients with intensive management of other cardiovascular risk factors, such as LDL-cholesterol.

In this study, researchers analyzed a total of 10,001 patients with coronary artery disease (CAD) who received either 10 mg of atorvastatin (n=5,006) or 80 mg of atorvastatin daily (n=4,995) for a primary composite endpoint of death from coronary disease, nonfatal myocardial infarction (MI), resuscitation after cardiac arrest, fatal or nonfatal stroke.

The relationship between systolic blood pressure (SBP) or diastolic blood pressure (DBP) and major cardiovascular events followed a J-curve with increased event rates above and below reference BP ranges (SBP 130-140 mm Hg and DBP 70-80 mm Hg). A non-linear Cox model identified a blood pressure of 140.6 mm Hg for SBP and 79.8 mm Hg for DBP where the event rate was lowest. The risk of major cardiovascular event increased 3.1-fold in the group with SBP ¡Ü110 mm Hg and 3.3-fold in the group with DBP ¡Ü 60 mm Hg. A similar J-curve relationship was found for the secondary endpoints of all-cause mortality, cardiovascular mortality, non-fatal MI and non-fatal stroke.

Study authors concluded that among a high-risk population with CAD enrolled in the TNT trial, despite substantial lowering of LDL-cholesterol, a J-curve relationship existed between both systolic and diastolic BP and the risk of future cardiovascular events, suggesting that low BP levels may be harmful.

"Our findings negate the dictum that with blood pressure, lower is always better," said study co-author Franz Messerli, M.D., director, Hypertension Program at St. Luke's-Roosevelt Hospital, New York, NY. "As we learn more about the effect of blood pressure on cardiovascular risk, we continually refine our understanding of the optimal treatment and blood pressure targets for these patients."

About the American Society of Hypertension
The American Society of Hypertension (ASH) is the largest U.S. professional organization of scientific investigators and healthcare professionals committed to eliminating hypertension and its consequences. ASH is dedicated to promoting strategies to prevent hypertension and to improving the care of patients with hypertension and associated disorders. The Society serves as a scientific forum that bridges current hypertension research with effective clinical treatment strategies for patients.