The Effects of Aging and Degenerative Vascular Disease on the Measurement of Arterial Rigidity in Man*

Abstract

In 1937, Hallock and Benson demonstrated a progressive loss of aortic distensibility with aging (1). Their observations on the pressure-volume relationship in segments of human aortas from five age groups are shown in Figure 1. The curves which represent the less distensible older aortas have a greater slope (d P/d V). The slope of each curve is not fixed, however, and it changes by bending toward the pressure axis as pressure increases. The rate of this change in slope (or the curvature) also is greater in the curves of older aortas.The present report deals with an indirect clinical index of the curvature of arterial pressurevolume curves, using the ratio of the change in pulse pressure to the change in diastolic pressure following the inhalation of amyl nitrite. This index is referred to, arbitrarily, as one of "arterial rigidity." A study of Hallock and Benson's curves made it apparent to us that the change in the slope of each curve is associated with a corresponding change in pulse pressure at different diastolic pressures. If the pressure-volume curve is relatively straight, as it is in the young, the curvature and the index will be near zero (Figure 2). If the line curves greatly toward the pressure axis, the index will be positive and large (Figure 3). If it curves the other way, the index will be negative. In vitro indices were derived from each of the five aortic distensibility curves and were found to correlate with age ( Figure 4). This observation suggested that the values of this index in "normal" subjects also should increase with chronological age. MATERIALS AND METHODSSelection of subjects. The subjects for this investigation were patients from the wards and members of the professional staff of Milwaukee County Hospital. One hundred fifteen subj ects varying from 8 to 95 years of age were studied. They were separated into nine age groups. Seven subjects, aged 8 to 19 years, comprised the first group; 4 subjects were 20 to 29 years of age; 18 were 30 to 39 years; 24 were 40 to 49 years; 21 were 50 to 59 years; 13 were 60 to 69 years; 16 were 70 to 79 years; 9 were 80 to 89 years; and 3 were 90 to 95 years. A careful clinical examination and review of the hospital records disclosed normal retinal vessels,1 "normal" blood pressures 2 and freedom from heart disease, overt periph- 1 Silver wiring and tortuosity were accepted as normal retinal changes in subjects over 60 years of age.2 All the subjects under 60 years of age had blood pressures below 140/80 and all those over 60 years had blood pressures below 170/90. 933

Linear relationship between systolic and diastolic blood pressure monitored over 24 h: assessment and correlates

“…Previous findings and interpretation of the systolic-ondiastolic slope About half a century ago, Conway and Smith [24,25] and Abboud and Huston [26,27] attempted to characterize the tendency of arteries to stiffen upon elevating pressure using intra-arterial BP changes that occur immediately after inhalation of amyl nitrite but before the onset of reflex tachycardia. The 'arterial rigidity index' was defined as the ratio of the change in pulse pressure to the related decrease in diastolic pressure during this period [24][25][26][27].…”

“…The 'arterial rigidity index' was defined as the ratio of the change in pulse pressure to the related decrease in diastolic pressure during this period [24][25][26][27]. This parameter, which resembles to some extent the systolic-on-diastolic slope, increased steeply with age and for hypertensive patients with arteriosclerosis.…”

Measurement of Arterial Aging in Hypertensive Patients*

“…The ratio of the change in pulse pressure X 100 to the related decrease in diastolic pressure during this period is the index of arterial rigidity (Figure 1). A detailed protocol of the test procedure has been presented (3). A complete physical examination and a careful review of the clinical record followed the performance of the test in each patient.…”

“…Our findings do not support this hypothesis, since the majority of patients in this study had normal rigidity indices for their age. (3) in which the effect of age on the rigidity index was determined. These "normal" subjects were selected to satisfy certain criteria among which were the absence of a family history of diabetes, of grade III or IV retinopathy and of left ventricular hypertrophy.…”

“…An indirect clinical index of the latter effect of aging on arterial walls has been described (2,3) and referred to, arbitrarily, as an "index of arterial rigidity." It does not measure the slope dP/dV of arterial pressure-volume curves but the rate of change in slope (or the curvature) with pressure.…”