No abstract

Non-invasive assessment of mechanical properties of the aorta may prove useful in the early detection of atheroma. We have evaluated several of the available echocardiographic indices using ability to detect age-related changes in putatively disease-free vessels as a measure of sensitivity to changes in aortic mechanical properties. Suprasternal imaging was used in 49 healthy non-smoking volunteers to measure minimum and maximum aortic arch diameters. Maximal flow velocities, with corresponding acceleration times and heart periods, were determined in the descending aorta in 24 of these subjects. Blood pressure was recorded non-invasively immediately after the echocardiographic study. Doppler derived measurements of aortic flow acceleration did not relate to age (P greater than 0.05). Three different 2D echo assessments of aortic distensibility, however, all showed a close relationship to age. Ep elastic modulus and Beta index (derived from different stress-strain mechanical relationships) were significantly related to age with r = 0.69 and 0.65 respectively. There were no significant effects of gender or left ventricular systolic function on these relationships. There was a tendency for the relationship between these distensibility indices and age more closely to fit an exponential than a linear relationship. We conclude that 2D echocardiographic assessment of aortic distensibility is able to detect sensitively changes in aortic mechanical properties. Even in the absence of risk factors for cardiovascular disease there is a marked reduction in aortic distensibility with increasing age.

We examined the prevalence of left ventricular structural and functional abnormalities in previously untreated subjects by performing echocardiography in 89 normal volunteers, 57 patients with established hypertension, and 38 patients with mild or borderline hypertension. We measured left ventricular mass, wall thickness, internal diameter, and wall thickness/radius ratio. Because of intergroup differences hi body size, we used covariance analysis to index these variables to a common value of 1.8 m 2. No adjustment was needed for the wall thickness/radius ratio. Functional variables determined were fractional shortening and transmitral early/late flow velocity ratio (the latter was standardized by analysis of covariance to age 40 years). The prevalence of left ventricular mass index values more than 2 SD above the mean of the normal group was 30% in the patients with established hypertension and 12-15% hi the patients with mild hypertension. Corresponding figures for wall thickness index were 65% and 32% and for the wall thickness/radius ratio 60% and 40%. The prevalence of abnormality in the transmitral flow velocity was 28% in the patients with established hypertension and 12% in the patients with mild hypertension. A multivariate discriminant function that used combined anatomic and functional variables provided the most reliable classification; it was correct in 82% of normal subjects, 65% of patients with established hypertension, and 61% of patients with mild hypertension. The majority of patients with hypertension have cardiac structural or functional abnormalities, or both. {Hypertension 1989; 13:151-162) I n human primary hypertension the reported prevalence of left ventricular hypertrophy (LVH) ranges between 20 and 80%. >-7 The majority of investigators suggest that the prevalence is closer to the lower end of this range. However, even the upper end of the range is below the almost universal prevalence of LVH in animals with genetic or experimental hypertension. -9 Hypertension is usually more severe in the experimental models, which could account for the greater incidence of LVH. In addition, most experiments are performed in inbred strains of animals, where the normal range of variation of left ventricular size may be smaller than in a mixed population 89 where genetic or environmental factors are not as well controlled. Many of the previous human series have included patients previously treated with antihyper-

The "chronic" effect of exercise on blood pressure has been controversial and the debate has been confused by a large number of studies with inadequate methodology. Recent consistent findings in epidemiological, experimental and longitudinal intervention studies have suggested that a true antihypertensive effect which is independent of confounding effects of sodium intake, weight, etc. is more likely than not. Unlike some other measures of lowering blood pressure such as sodium restriction, alcohol moderation and some drugs, regular exercise is associated with beneficial effects on several risk factors and probably has an independent effect on cardiovascular mortality. The magnitude of the effect in previously sedentary subjects is greater than that of dietary measures which lower blood pressure except for weight reduction in the obese. Long-term effects on blood pressure are supported by evidence of a favourable influence on left ventricular hypertrophy. The mechanisms involved in the antihypertensive effect of exercise are unclear, but sympathetic withdrawal is one factor involved. Present evidence appears sufficient to include regular exercise amongst the useful therapies for hypertension.

Three patients with ischaemic heart disease developed profound cardiac failure, hypotension and bradycardia during combined therapy with verapamil and beta-adrenergic blocking drugs. This clinical picture resolved completely with cessation of the combined therapy. Baseline left ventricular function, assessed by cardiac catheterisation or nuclear angiography, was normal in two patients and only mildly reduced in the other. Simultaneously administration of beta-adrenergic blocking drugs and verapamil may result in profound adverse interactions and should only be administered with great caution.