Chapter 32 Nursing Assessment: Cardiovascular System 763Cardiovascular System

Pulse Pressure and Mean Arterial Pressure. Pulse pressure is the difference between the SBP and DBP. It is nor-mally about one third of the SBP. If the BP is 120/80, the pulse pressure is 40. An increased pulse pressure may occur during ex-ercise or in individuals with atherosclerosis of the larger arteries due to increased SBP. A decreased pulse pressure may be found in cardiac failure or hypovolemia.

Another measurement related to BP is mean arterial pressure (MAP). The MAP is the perfusion pressure felt by organs in the body. It is not the average of the diastolic and systolic pressures because the duration of diastole exceeds that of systole at normal HRs. MAP is calculated as follows:

MAP � (SBP � 2 DBP) � 3

A person with a BP of 120/60 has a MAP of 80. A MAP of greater than 60 is necessary to sustain the vital organs of an aver-age person under most conditions. If the MAP falls signifi cantly below this number for an appreciable time, vitals organs will be underperfused and will become ischemic.

GERONTOLOGIC CONSIDERATIONSEFFECTS OF AGING ON THE CARDIOVASCULAR SYSTEM

Cardiovascular disease is the most common cause of hospitaliza-tion and the second cause of death in adults less than age 85. It remains the leading cause of death in adults greater than age 85. The most common cardiovascular problem is coronary artery disease (CAD) secondary to atherosclerosis. It is diffi cult to sep-arate normal aging changes from the pathophysiologic changes of atherosclerosis. Current thinking suggests that many of the physiologic changes in the cardiovascular system of the elderly are a result of the combined effects of the aging process, disease, environmental factors, and lifetime health behaviors rather than age alone.4,5

With increased age, the amount of collagen in the heart in-creases and elastin decreases. These changes affect the contractile and distensible properties of the myocardium. One of the major

age-associated alterations in the cardiovascular response to physi-cal or emotional stress is a decrease in CO and SV caused by de-creased contractility and HR response to increased stress. The resting HR is not markedly affected by aging.

Cardiac valves become thicker and stiffer from lipid accumula-tion, degeneration of collagen, and fi brosis.5 The aortic and mitral valves are most frequently affected. These changes result in either regurgitation of blood when the valve should be closed or narrow-ing of the orifi ce of the valve (stenosis) when the valve should be open. The turbulent blood fl ow across the affected valve results in a murmur.

The number of pacemaker cells in the SA node decreases with age. By age 75, a person may have only 10% of the normal number of pacemaker cells, though this is compatible with normal SA node function.2 Similar decreases in the number of conduction cells in the AV node, the bundle of His, and the bundle branches also occur with aging. Fibrosis of the bundle branches has been shown to precipitate chronic heart block in persons 65 years and older.2 A normal ECG of an aging patient may show small, incon-spicuous increases in PR, QRS, and QT intervals.

The autonomic nervous system control of the cardiovascular system is altered with aging. The number and function of �-adrenergic receptors in the heart decrease with age. Therefore the older adult not only has a decreased response to physical and emo-tional stress but also is less sensitive to �-adrenergic agonist drugs.

Arterial blood vessels thicken and become less elastic with age.6 Arteries increase their sensitivity to vasopressin (antidiuretic hormone). Both of these changes contribute to a progressive in-crease in SBP and a decrease or no change in DBP with age. Con-sequently, an increase in the pulse pressure is found. Hypertension is not considered a normal consequence of aging and should be treated.

Orthostatic hypotension is estimated to be present in 30% of patients over age 70 with systolic hypertension.7 Despite the changes associated with aging, the heart is able to function ade-quately under most circumstances.

Age-related changes in the cardiovascular system and differ-ences in assessment fi ndings are presented in Table 32-1.

Changes Differences in Assessment Findings Chest WallKyphosis Altered chest landmarks for palpation, percussion, and auscultation; dis-

tant heart sounds

HeartMyocardial hypertrophy, ↑ collagen and scarring, ↓ elastin ↓ Cardiac reserve, heart failure

Downward displacement Diffi culty in isolating apical pulse

↓ CO, HR, SV in response to exercise or stress Slowed, ↓ response to exercise and stress; slowed recovery from activity

Cellular aging changes and fi brosis of conduction system ↓ Amplitude of QRS complex and slight lengthening of PR, QRS, and QT intervals; irregular cardiac rhythms, ↓ maximal HR, ↓ HR variability

Valvular rigidity from calcifi cation, sclerosis, or fi brosis, impeding complete closure of valves

Systolic murmur (aortic or mitral) possible without being indication of car-diovascular pathology

Blood VesselsArterial stiffening caused by loss of elastin in arterial walls, thickening of

intima of arteries, and progressive fi brosis of media ↑ in systolic and possible ↑ or ↓ in diastolic BP; possible widened pulse

pressure; pedal pulses diminished, ↑ in intermittent claudication

Venous tortuosity increased Infl amed, painful, or cordlike varicosities

BP, Blood pressure; CO, cardiac output; HR, heart rate; SV, stroke volume.

TABLE 32-1

GERONTOLOGIC DIFFERENCES IN ASSESSMENTCardiovascular System

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