Coronary arterial dimensions and cell populations in ageing man

Age and vascular aging: an unexplored frontier

Vascular age is an emerging field in cardiovascular risk assessment. This concept includes multifactorial changes in the arterial wall, with arterial stiffness as its most relevant manifestation, leading to increased arterial pressure and pulsatile flow in the organs. Today, the approved test for measuring vascular age is pulse wave velocity, which has been proven to predict cardiovascular events. Furthermore, vascular phenotypes, such as early vascular aging and "SUPERNOVA," representing phenotypic extremes of vascular aging, have been found. The identification of these phenotypes opens a new field of study in cardiovascular physiology. Lifestyle interventions and pharmacological therapy have positively affected vascular health, reducing arterial stiffness. This review aims to define the concepts related to vascular age, pathophysiology, measurement methods, clinical signs and symptoms, and treatment.

Arterial remodeling in the left coronary system: the role of high-density lipoprotein cholesterol

OBJECTIVES

We sought to evaluate the plaque and patient variables related to arterial remodeling responses of early, de novo atherosclerotic lesions involving the left coronary artery.

BACKGROUND

Coronary artery remodeling is a lesion-specific process involving either enlargement or shrinkage of atherosclerotic coronary arteries. There are little histologic data available correlating plaque morphologic and patient clinical characteristics with the degree and type of arterial remodeling in early atherosclerosis.

METHODS

We studied 736 serial arterial sections from the left coronary system of 97 autopsy cases (mean age 33 +/- 11 years) by correlating the arterial remodeling response to plaque with demographic, serologic and histologic variables. Using the most proximal section as a reference, and considering the expected degree of internal elastic lamina tapering, remodeling was classified as positive (including neutral remodeling or compensatory enlargement) or negative.

RESULTS

Remodeling was classified as positive in 84.3% (compensatory in 30.6%) and negative in 15.7% of sections with an overall mean luminal stenosis of 10.4 +/- 9.9%. In the lesions with the greatest arterial cross-sectional narrowing from each case, compensatory enlargement was associated with higher high-density lipoprotein (HDL) cholesterol (59.4 +/- 27.2 mg/dl) compared with either neutral (49.3 +/- 15.5 mg/dl) or negative remodeling (30.4 +/- 5.2 mg/dl; p = 0.019). In subjects with advanced atherosclerosis (maximum American Heart Association histologic grade 5 atherosclerosis), there was a modest linear relationship between higher HDL cholesterol and the propensity for positive remodeling (r2 = 0.37; p = 0.025). On multivariate analysis, only HDL cholesterol was related to the arterial remodeling response.

CONCLUSIONS

Negative arterial remodeling occurs in early atherosclerosis. Higher HDL cholesterol may favor positive remodeling.

Is arterial remodeling truly a compensatory biological reaction? A mechanical deformation hypothesis

It has been recognized that arterial enlargement occurs in relation to the formation of atherosclerotic plaque. Previous studies on arterial remodeling have disregarded the role of mechanical deformation and have suggested that compensatory mechanisms occur to maintain arterial flow. We postulated that primary atherosclerotic enlargement and mechanical deformation are the predominant causes of the arterial remodeling. This hypothesis better explains the morphological changes without suggesting additional biological reactions.

Causal relationship between occlusive lesions of the coronary artery and myocardial fibrosis in arteriosclerotic rabbits--differences between cholesterol-fed and heritable hyperlipidemic rabbits

To investigate the causal relationship between lesions of either the proximal large or the distal small coronary arteries and myocardial fibrosis, the hearts and the aortas of 99 cholesterol-fed rabbits with either intermittent or continuous hyperlipidemia for 8 months or more, 44 Watanabe-heritable hyperlipidemic (WHHL) rabbits and 20 normal rabbits were studied histologically. The size and location of the myocardial fibrosis correlated closely with the almost completely occlusive distal small coronary artery which mainly consisted of macrophages, necrosis and calcification but did not correlate with the maximum % stenosis of the large proximal subepicardial coronary arteries in the cholesterol-fed-rabbits. Myocardial fibrosis and almost completely occlusive lesions of the distal small coronary arteries were very rare in the WHHL rabbits, and the maximum % stenosis of the proximal coronary artery and aortic lesions in the WHHL rabbits tended to be greater than those in the cholesterol-fed rabbits. Thus, we are still not certain as to whether or not, the organic stenosis of the subepicardial coronary artery is responsible for myocardial fibrosis in WHHL-rabbits. In conclusion, a causal relationship was observed between myocardial fibrosis and the occlusive lesions of the distal small coronary arteries in cholesterol-fed rabbits, while the arteriosclerotic lesions of the small coronary artery in cholesterol-fed rabbits completely differed from those observed in WHHL-rabbit.

Inheritability of atherosclerosis and the role of lipoproteins as risk factors in the development of atherosclerosis in WHHL rabbits: risk factors related to coronary atherosclerosis are different from those related to aortic atherosclerosis

Inheritability of atherosclerosis and the influences of serum lipids on atherosclerosis were examined by following its progression in selectively bred WHHL rabbits. Our studies indicate (1) coronary atherosclerosis is clearly inherited from parents by offspring whereas inheritability of aortic atherosclerosis is uncertain; (2) coronary stenosis is positively correlated to serum cholesterol level, although the correlation coefficient is markedly low: in contrast, no relationship between serum lipid levels and aortic atherosclerosis was observed; (3) cholesterol-rich VLDL showed atherogenicity in aorta, but not in coronary arteries; (4) an unknown lipoprotein detected by 3.6% polyacrylamide gel electrophoresis was related to coronary atherosclerosis, although no relationship between the unknown lipoprotein and aortic atherosclerosis was observed. These findings suggest that there are two types of genetic factors involved in atherosclerosis, one of which is unique to coronary atherosclerosis whereas the other is related to only aortic atherosclerosis.

Suppression of established atherosclerosis and xanthomas in mature WHHL rabbits by keeping their serum cholesterol levels extremely low. Effect of pravastatin sodium in combination with cholestyramine

We investigated the possibility that established atherosclerosis and xanthomas in mature WHHL rabbits could be suppressed or even regressed when their serum cholesterol levels were kept extremely low. Ten-month-old WHHL rabbits were divided into 3 groups, i.e. control rabbits, sacrificed at age 10 months, and placebo and treated rabbits, sacrificed at age 18 months. The treated rabbits were given pravastatin sodium (50 mg/kg/day), an HMG-CoA reductase inhibitor, in combination with cholestyramine (2% in diet), a bile acid sequestrant, for 36 weeks. The serum cholesterol levels and atherogenic lipoproteins in the treated group were markedly reduced, by about 60% (P less than 0.005 and P less than 0.001). Consequently, the degrees of both coronary and aortic atherosclerosis in the treated group were significantly reduced compared with the placebo group, and were almost the same as in the control group. The histopathological findings supported the above results. In addition, the incidence and degree of xanthomas in digital joints in the treated group were significantly reduced. These results suggest that established atherosclerosis and xanthomas in mature WHHL rabbits could be suppressed by keeping their serum cholesterol levels extremely low by the combination drug treatment.