A 78-year-old man is being evaluated for headaches that are relieved by over-the-counter acetaminophen. He takes no other medications and is a lifelong nonsmoker. The patient's blood pressure is 180/70 mm Hg and pulse is 75/min and regular. During a prior office visit, blood pressure was 175/68 mm Hg. Physical examination shows an S4 but is otherwise unremarkable. CT scan of the head reveals no significant abnormalities. Which of the following age-related changes best explains this patient's blood pressure readings?
Physiologic age-related cardiovascular changes | |
Aortic stiffening |
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Mild concentric LVH* |
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Conduction cell degeneration |
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Reduced baroreceptor sensitivity & adrenergic responsiveness |
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*A soft S4 is a normal finding in the elderly. EF = ejection fraction; HTN = hypertension; LVH = left ventricular hypertrophy; SV = stroke volume. | |
This patient's blood pressure readings show a pattern of elevated systolic blood pressure (SBP) with relatively low diastolic blood pressure (DBP) and elevated pulse pressure, consistent with isolated systolic hypertension (ISH). ISH is often seen in elderly patients (eg, age >65), representing 60%-80% of hypertension cases in this population.
Aging is associated with increased aortic stiffness caused by endothelial dysfunction and a change in extracellular matrix composition (ie, replacement of elastin with collagen). These changes reduce aortic compliance, which increases pulse pressure (pulse pressure is directly related to stroke volume and inversely related to aortic compliance). In youth, ample aortic compliance results in delayed retrograde reflection of pressure waves during ventricular systole, with the waves returning to the heart after aortic valve closure and assisting in coronary artery perfusion. The reduced compliance that occurs with age hastens the retrograde reflection of pressure waves, causing the waves to return prior to aortic valve closure and increase the load on the left ventricle (ie, increased SBP).
Reduced aortic compliance also causes less blood volume to be retained in the arterial system between left ventricular contractions, slightly decreasing DBP.
(Choice A) The aortic lumen slightly increases (not decreases) in diameter with age. Nonetheless, it is the compliance of the large arteries (rather than the diameter) that affects blood pressure. The diameter of the small arteries (ie, arterioles) determines systemic vascular resistance and is a primary determinant of DBP.
(Choice B) A decrease in stroke volume decreases pulse pressure, leading to reduced SBP. However, stroke volume is generally maintained with age; a physiologic decrease does not occur.
(Choice D) Renal arterial resistance can increase with age due to the development of renal artery atherosclerosis. This causes hypertension by activating the renin-angiotensin-aldosterone system to cause sodium retention and arteriolar vasoconstriction, resulting in increased DBP (and increased SBP due to unchanged pulse pressure) rather than ISH.
(Choice E) Increased sympathetic tone causes increased DBP (arteriolar vasoconstriction) and increased pulse pressure (increased contractility leading to increased stroke volume). Increased sympathetic tone often contributes to hypertension in patients age <50, but sympathetic tone decreases with age due to reduced responsiveness of adrenergic receptors.
Educational objective:
The isolated systolic hypertension commonly seen in elderly patients results from age-related stiffening (ie, replacement of elastin with collagen) and reduced compliance of the aorta and other large arteries.