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Thursday, December 12, 2013
High Blood Pressure
Pulse pressure and central pressure
I understand that pulse pressure is the difference between the systolic and diastolic readings and the larger the difference the higher the risk of a cardiovascular event.
Is the central pressure the same as pulse pressure ? Or put in another way would a large pulse pressure indicate a larger central pressure?
Can isometric tension increase central pressure as well?
The pulse pressure is a measure of arterial stiffness. With aging, arteries lose elasticity, and the systolic pressure (generated by the heart) has to increase, to be able to push the same amount of blood through the arterial tree ("stiffer pipes"). Because of decreased elasticity, the drop in blood pressure following the cardiac contraction is larger (the arteries cannot constrict as quickly to preserve the pressure).
This change in the arteries over the years is reflected by a slow increase in the systolic pressure and a decrease in the diastolic pressure. For that reason, the pulse pressure is a good measure of arterial aging and is the best indicator of the risk for stroke and heart disease.
The central aortic pressure is related to the pulse pressure, but is not the same thing. Usually, blood pressure is measured in the arm, as brachial or radial pressure. The central aortic pressure is the pressure in the aorta close to the heart. It is not only determined by the action of the heart itself, but also by the reflection of the pulse wave from the periphery. This is similar to the wave caused by a rock thrown in the water, that will be reflected by an object sticking out of the water's surface. The wave will be reflected at that point, and by moving backward, causes a "summation wave" that can be higher than the original wave. The physics are somewhat complicated, but it has been found that the degree and extent of arterial stiffening influences this summation wave in the aorta. For that reason, the pressure in the aorta can be quite a bit higher than in the arm.
A large pulse pressure often goes along with a higher central aortic pressure. The concept is important, because some medications decrease the central aortic pressure more than others, which may be beneficial.
Regarding exercise, regular aerobic activity reduces arterial stiffness, while resistance training (weight lifting) actually increases it.
Max C Reif, MD
Professor of Medicine
Director of Hypertension Section
College of Medicine
University of Cincinnati