Systolic blood pressure is the pressure in the arteries as the heart contracts, while the pressure that remains during cardiac relaxation is known as diastolic. Isolated systolic hypertension has been defined as a systolic blood pressure above 140 mm Hg with a diastolic pressure less than 90 mm Hg. This condition becomes more common as people age, and its main cause seems to be related to age-associated changes in the blood vessels. Elevated systolic blood pressure is a known risk factor for heart attack and stroke.
Aortic Stiffness
Drs. Smulyan and Safar discuss the concept of a stiffened aorta as a cause of isolated systolic hypertension in the "Annals of Internal Medicine." The aorta is the main artery that exits the heart and serves as a conduit for blood flow to the whole body. As we age, this vessel tends to lose elasticity and compliance. This increased stiffness leads to an increase in pressure because the walls have less give and are unable to absorb the force exerted by the pumping action of the heart. These factors do not come into play when the heart relaxes, so the diastolic pressure is not affected.
Essential Hypertension
The vast majority of elevated blood pressure is termed essential, meaning it occurs without any other medical cause of explanation, and is likely multifactorial, meaning there are several factors whose combined effects produce the hypertension. It is often related to lifestyle choices, and is affected by dietary levels of salt, caffeine and alcohol. It is also more prevalent in the obese and those who lead a sedentary life. Nicotine intake through cigarettes and chewing tobacco correlate with blood pressure levels. Genetic and other poorly understood factors may play a role as well. Although essential hypertension is not limited to the systolic reading, many people with this condition will have greater elevations in systolic pressure than diastolic pressure. This may be related to a genetic predisposition, certain specific lifestyle choices, or an individual's particular cardiovascular makeup.
Hyperthyroidism
The thyroid gland is very important in managing the overall metabolism and activity of the body. It may become overactive for a number of reasons, but this hyperactivity may lead to increased heart rate and blood pressure. Hyperthyroidism is an important cause of isolated systolic hypertension according to Mayoclinic.com
Hyperaldosteronism
Aldosterone is a hormone in the body that regulates sodium levels and blood volume. It may become elevated through various mechanisms. When this occurs, elevated systolic blood pressure may develop. Elevated levels of aldosterone is a leading cause of secondary hypertension.
References
- National Heart, Lung, and Blood Institute Guidelines: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure
- "Annals of Internal Medicine"; The Diastolic Blood Pressure in Systolic Hypertension; Harold Smulyan, MD, and Michel E. Safar, MD; February, 2000
- FP Notebook: Hypertension Causes
- Mayoclinic.com: Isolated Systolic Hypertension: A Health Concern?
