2.5. Carotid atherosclerosis and hypertension

Carotid atherosclerosis has been determined by different combinations of IMT, plaque size and number, sums of plaque sizes, stenosis and flow changes (Fine-Edelstein et al. 1994). In the Framingham Study cohort of 1116 subjects, the degree of carotid atherosclerosis was expressed as percent stenosis. Crouse et al. (1986) summed up the thicknesses of four near- and far-wall sites on each side to obtain a carotid artery score, whereas Bonithon-Kopp et al. (1993) and Salonen et al. (1988) classified atherosclerosis into three categories: no arteriosclerotic lesions, IMT, plaques with or without IMT. Plaques have been found with varying frequencies in the range of 6.3–80.6%, depending mainly on the age range (Fabris et al. 1994, Pujia et al. 1992). In hypertensive subjects, the prevalence of plaques has been 43–96.4% (Prisant et al. 1993, Sutton et al. 1987, Lusiani et al. 1990). Roman et al. (1992) found plaques to be equally prevalent in control subjects (14%) and hypertensive patients (12%), but in another work (Roman 1991) plaques were more frequent in hypertensive patients (28.5% versus 10%).

The results associating high blood pressure or hypertension with carotid atherosclerosis measured as IMT and carotid plaques have been contradictory. In several studies, carotid atherosclerosis has been more prevalent in hypertensives than in controls (Roman et al. 1992, Crouse et al. 1987, Tell et al. 1989, O’Leary et al. 1992, Bots et al. 1993), but contrary results have also been reported (Roman et al. 1992, Handa et al. 1990, Poli et al. 1993, Haapanen et al. 1989). Baseline blood pressure did not have a significant association with the progression of carotid IMT during a follow-up of 2 years (Salonen & Salonen 1990). However, in the Framingham Study cohort, systolic BP was independently related to carotid atherosclerosis in multivariate analysis. The odds ratio for carotic stenosis for an increase of 10 mmHg in systolic BP was 1.22 (95% CI 1.10 to 1.37) in men and 1.21 (95% CI 1.12 to 1.31) in women (Fine-Edelstein et al. 1994). In the San Daniele project, systolic BP was independently related to the plaque-stenosis group (odds ratio for an increase of 10 mmHg in systolic BP, was 1.12 (95% CI 1.03 to 1.22)(Prati et al. 1992). Increased IMT was associated with isolated systolic hypertension in asymptomatic elderly subjects in the Rotterdam Elderly Study (Bots et al. 1993). In renovascular hypertensives, the prevalence of carotid artery lesions (82.6%) was significantly higher (p < 0.01) than in primary hypertensives (42.9%). The higher prevalence of lesions in renovascular hypertension was observed not only in patients with atherosclerosis (100% vs 55%, p < 0.001), but also in those with fibrodysplasia (57% vs 27%, p < 0.01)(Rossi et al. 1994). The discrepancies between previous studies are most probably due to different compositions of the study populations, small sample size and less well established hypertension (Folsom et al. 1994).

Consistently, the effect of hypertension on IMT has been less powerful than the effect of other CV risk factors, i.e., age, smoking and cholesterol (Giral et al. 1991, Handa et al. 1990). In the ACAPS study (Furberg et al. 1994), the lipid-lowering lovastatin intervention effect in hypertensive patients was larger than in the nonhypertensive group.