High Blood Pressure

what does the blood pressure reading mean?

Blood pressure is measured with two numbers.

The heart pumping cycle consists of two phases: the active pumping called "systole" and the relaxation phase called "diastole."

The "systolic" pressure (the top number) is the pressure generated by the pumping action of the heart as it pushes the blood out of the heart into the circulation.

The bottom number, called the "diastolic" pressure, comes from the pressure out in the circulation. This is the system pressure that the heart must overcome in order to push the blood out.

The higher the diastolic system pressure, the harder the heart must work to push the blood out.

Blood pressure is controlled by several systems. The kidneys control the amount of fluid in the system. The heart adjusts by pounding harder or faster. The arteries and veins adjust the tension in the system.   

 Chobanian, et al. the JNC7 Report, JAMA 2003;289:2560-2572

Chobanian, et al. the JNC7 Report, JAMA 2003;289:2560-2572

Blood pressure fluctuates every few minutes. It is usually higher during emotional stress and physical activity.

When hypertensive patients complain that their blood pressure is always normal at home (relaxing in a stress-free environment), a 24 hour monitoring device can reveal how high their blood pressure is throughout the day. 

Almost no one can live in a stress-free environment.

High blood pressure has a direct effect on the arteries. The higher the blood pressure, the higher the risk for a heart attack or stroke (1).

Aggressive blood pressure control (defined as using 120 systolic as target) reduced the risk of cardiovascular events by almost 1/3 and the risk of total mortality by almost 1/4, compared to the more conventional target of 140 systolic, according to the NIH-sponsored SPRINT study (2).


  1. Chobanian, et al, the National High Blood Pressure Education Program Coordinating Committee, the JNC7 Report JAMA 2003;289:2560-2572
  2. The SPRINT study of 9,300 hypertensive adults over 50, divided into two treatment target groups of systolic BP < 120 or < 140 was stopped prematurely when benefits of the more aggressive treatment strategy became apparent. The study itself has not yet (as of 9/16/15) been published. See: http://www.nih.gov/news/health/sep2015/nhlbi-11.htm