Doctors are being urged to be cautious about lowering blood pressure too much in people with coronary artery disease, because it may increase the risk of heart attacks, according to a study.
An international team of scientists, including researchers from Imperial College London, found that while high blood pressure is responsible for heart attacks, blood pressure that is too low could also trigger them.
What Blood Pressure Readings Mean
Blood pressure readings are measured in millimeters of mercury (mmHg) and are written as systolic pressure -- the force of the blood against the artery walls as your heart beats -- over diastolic pressure -- the blood pressure between heartbeats.
People with ideal blood pressure will have readings below 120 over 80, expressed as 120/80. About 1 in 3 U.S. adults have high blood pressure, the American Heart Association says.
Having high blood pressure, also known as hypertension, can lead to health problems including heart disease, heart attack, stroke, and kidney disease.
International Study
The study followed 22,672 people from 45 countries who had heart disease and who were also on medication for high blood pressure.
The scientists found that a blood pressure reading higher than 140/80 was linked to an increased risk of heart attack and stroke.
However, they also discovered that a systolic blood pressure reading higher than 120 mmHg, as well as a diastolic blood pressure below 70 mmHg, were associated with a higher chance of death, having a heart attack, and hospitalization for heart failure.
Caution Over Blood Pressure Treatment
The analysis “confirms the importance of treating high blood pressure,” Professor Kim Fox, co-author of the study and head of the National Heart and Lung Institute at Imperial College London, says in a statement.
"However it also cautions against over-enthusiastic blood pressure control. Blood pressures generally considered normal, and below 120/70, may be too low in patients with coronary disease and treated hypertension."
But the study found that to reduce the risk of stroke, the lower the blood pressure, the better.
The researchers say more studies are needed to establish the ideal blood pressure levels below which harm outweighs benefit. In the meantime, they suggest caution when treating people with heart disease with blood pressure-lowering medication.
The study appears in the online edition of The Lancet.
Peter Russell - WebMD
