Experimental induction of atherosclerosis associated with femoral arteriovenous fistulae in rabbits on a stock diet

Hypothetical hypercholesterolaemia and atherosclerosis

Recent pathological advances in experimental and iatrogenic atherosclerosis and critical review of the epidemiology of coronary heart disease revealed fallacious data and methodological errors underlying the hypercholesterolaemia/lipid hypothesis. Misuse of risk factors, inappropriate use of surrogates and misinterpretation of data pertaining to cholesterol's role in atherogenesis necessitate greater precision in word usage and terminology, reinstitution of the statistical reference range for cholesterol and closer scientific surveillance of aetiological endeavours in medicine.

Structure adaptation and blood flow control in the uterine arterial system after hemochorial placentation

In the course of hemochorial placentation, trophoblast cells build a most conductive placental stream bed for maternal blood with intramural foetal capillaries. The stream bed is adapted to the maternal vascular system, causing local increase in flow and shear stress. Subsequently, local maternal microvascular system vanishes. The remaining upstream arteries, up to the aorta, undergo "physiological changes", i.e. increase in circumference and length, predominantly by growth and remodeling. Peripheral uterine arteries, possibly collapsed due to low intraluminal pressure, show over-dilatation associated with endothelium destruction and trophoblast cell invasion. Overall arterial conductance increases to controlled extent; placental blood flow rate rises moderately. Intraplacental blood pressures are kept low allowing for free perfusion of placental foetal capillaries. According to the generally accepted concept, destructing impact of invading trophoblast cells causes the physiological changes. However, trophoblast invasion does not explain physiological changes occurring before and outside trophoblast invasion. On the other hand, physiological changes may well be induced by shear stress, which operates in extrauterine body regions as signal for vascular adaptation to growth. Thus, it is hypothesized that trophoblast cells control vascular adaptation and placental blood flow rate simply by constructing the hemochorial steam bed, thereby building up shear stress and triggering the general physiological automatism for controlled vascular adaptation to growth.

Misperception of adaptation and remodeling in vascular pathology

A prerequisite of scientific communications is that words should not be misrepresented. Currently, the frequent misuse of adaptation and remodeling derives from faulty analysis and misrepresentation of the pathology of coronary atherosclerotic lesions. This misperception of vascular pathology has misled the uncritical and unwary, and propagates fallacious data and concepts. Unless the misusage ceases, the terms will continue to be meaningless merely furthering promulgation of unscientific data and concepts that effectively obstructs scientific progress.

Coronary heart disease, hypercholesterolemia, and atherosclerosis. I. False premises

Lipid-rich caseous debris of advanced lesions stimulated interest in the role of cholesterol and lipids in atherosclerosis. Lipid-containing arterial lesions in cholesterol-overfed animals (cholesterolosis) and xanthomatous vascular lesions in subjects with familial hypercholesterolemia were then misrepresented as being atherosclerotic and led to the development of the hypercholesterolemic/lipid hypothesis. It is untenable that cholesterol, an essential multifunctional metabolite, is pathogenic at all blood levels and hypercholesterolemia is not prerequisite for human or experimental atherosclerosis. Serum cholesterol levels display a poor correlation with atherosclerosis at autopsy and with unreliable national coronary heart disease (CHD) mortality in each sex. Atherosclerosis topography and its iatrogenic production in humans and experimentally in herbivores by hemodynamic means both support a biomechanical causation and preclude causality by any circulating humoral factor. CHD, not a specific disease, is a nonspecific complication of many diseases including atherosclerosis and cannot be equated with coronary atherosclerosis due to differences in pathology and pathogenesis. Thus, extrapolations from CHD risk factors or correlations with fallacious vital statistics to atherosclerosis are invalid. It follows that the hypercholesterolemic/lipid hypothesis evolving from false premises, misuse of CHD, scientific misrepresentation, and fallacious data has no legitimate basis.

Coronary heart disease, hypercholesterolemia, and atherosclerosis. II. Misrepresented data

Early development of the hypercholesterolemic/lipid hypothesis of atherosclerosis was based on false premises including fallacious national mortality rates and misrepresentation of the vascular lesions in cholesterol-overfed animals and monogenic hypercholesterolemias (MH). Nonspecific coronary heart disease (CHD) was inappropriately used as a surrogate of atherosclerosis, unmeasured and unseen. Causality was assumed and implied by classifying statistical correlates of CHD as atherogenic risk factors. These faults were compounded by methodological errors, pooling of all causes of CHD, a large clinical diagnostic error, biased age selection of cohorts leading to confounding by age and MH, and emphasis on population and cohort mean values which conceal heterogeneity within cohorts and are inapplicable to individuals. Overzealous investigators neglected to review the premises and relevant pathology on which the hypothesis was based or to reconcile valid criticisms, inconsistencies, and invalidation of CHD epidemiology by pathological, experimental, and iatrogenic evidence. Statistical data, pertaining to CHD but with no scientific applicability to atherosclerosis, progressively imparted to readers a misleading perception of the relationship of serum cholesterol to CHD. Concurrently the statistical serum cholesterol range was unjustifiably abandoned. The evidence establishes that the lipid hypothesis of atherosclerosis lacks scientific basis.

Evaluation of aneurysm models, particularly of the aorta and cerebral arteries

Irrespective of their intended use, the best models of spontaneous aneurysms in humans are produced under conditions analogous to those occurring in humans and specific for the site. Even if appropriate for other purposes, models dependent on artificial conditions (physical and thermal trauma, chemical and enzymatic degradative processes), not in compliance with the above, bear no relationship to the etiology or pathology of the lesion or disease under investigation. Surgical models of poststenotic dilatation and aneurysm, arteriovenous shunts, and venous graft aneurysms are suitable for study of the prevailing hemodynamics and pathological effects of the associated stresses on the vessel wall which have bearing on degenerative aneurysms at other sites. The protracted course of atherosclerosis and constraints of time and research funds when reproducing the pathology and conditions prevailing in the human situation legitimize the use of models which accelerate development and complications. The limitations of any model are of paramount consideration. The value of some current models of aortic and cerebral aneurysms is discussed.

The elusive local factor in atherosclerosis

Recent evidence confirms that local haemodynamic stresses account for the initiation, topographical localization and complications of atherosclerosis. These causative stresses are vibratory and associated with pulse pressure and the lesser vibrations of greater frequency generated by blood flow at predilection sites. This bioengineering fatigue hypothesis is further substantiated by analogous effects of repetitive stresses on erythrocytes and in the musculoskeletal system. The mechanism underlying fatigue is cumulative molecular scissions of the mural constituents which ultimately result in failure of the wall as a whole. Free radicals and oxidation products are by-products of this molecular scission in atherogenesis. This theory which explains the progressive inexorable loss of mural cohesion, its pathogenesis and complications is completely substantiated by the iatrogenic and experimental reproduction of the disease by haemodynamic means.

Ultrastructure of the afferent arteries of experimental femoral arteriovenous fistulae in rabbits

Using transmission electron microscopy, the aorta and ilio-femoral arteries of 12 normocholesterolemic rabbits with femoral arteriovenous fistulae were investigated (49 to 895 days post-operatively) to determine whether the fibrofatty lesions in arteries proximal to chronic fistulae were ultrastructurally consistent with human atherosclerosis. The contralateral ilio-femoral arteries from the same animals and the vessels of 4 additional rabbits (2 with femoral arteriotomies) served as control material for comparison. There were microfractures adjacent to complete tears of the internal elastic lamina which had abrupt margins. These tears were observed mostly in the ilio-femoral arteries proximal to the fistula. They were most numerous, extensive and associated with considerable intimal proliferation near the fistula. Further proximally the tears were associated with progression to severe atrophy of the wall, the media in places being reduced in width to no more than 2 or 3 smooth muscle cells without any evidence of cellular degeneration. Intimal proliferation near the fistula and the naturally occurring intimal thickenings at branching sites proximal to the fistula, not only extended peripherally and progressed with time post-operatively, but exhibited ultrastructural changes consistent with atherosclerosis. These changes comprised dystrophic basement membrane, granulovesicular degeneration (matrix vesicles) and necrosis of smooth muscle cells, disruption of the elastic laminae, the appearance of extracellular and to a lesser extent intracellular lipid, adherence of monocytes, accumulation of foam cells, intimal fibrin deposition and sub-endothelial hemorrhage. Such results indicate that augmented hemodynamic stresses associated with femoral arteriovenous fistulae are consistent with those of human atherosclerotic lesions.

The ultrastructure of arteries proximal to chronic experimental carotid-jugular fistulae in rabbits

The afferent arteries from 11 normocholesterolemic rabbits with carotid-jugular arteriovenous fistulae ranging in duration from 107 to 718 days were examined by transmission electron microscopy to determine long term effects of an arteriovenous shunt on the afferent artery. Extensive tears and fragmentation of the internal elastic lamina of the elastic common carotid arteries were observed in all animals. Fragmentation and loss of elastic tissue as well as loss of muscle in the media accompanied progressive mural atrophy and tortuosity. Close to the fistula and in regions of tortuosity, fibromusculoelastic intimal proliferation was superimposed on the atrophic medial changes. The accumulation of matrix vesicles (cell debris), bizarre shaped smooth muscle cells, irregularly thickened multilaminated and reticulated basement membrane material beneath the endothelium and about smooth muscle cells, and abnormal shaped collagen fibrils were observed in the intima. Lipid was frequently found in the extracellular matrix and within smooth muscle cells while monocytes and lipid-laden macrophages were a feature of the more advanced intimal changes. These experiments confirm that in the absence of hypercholesterolemia the hydraulic stresses associated with an arteriovenous shunt cause severe mural atrophy and proliferative changes in the intima similar in nature to those of atherosclerosis.

Science, atherosclerosis and the "age of unreason": a review

Research in atherosclerosis has been dominated by the lipid hypothesis. The pathology of both the cholesterol-fed animal and of familial hypercholesterolemia has been misrepresented. The vascular lesions of these disorders are not atherosclerotic but manifestations of fat storage. There has been undue faith in the epidemiology of coronary heart disease and atherosclerosis. Fundamental defects in the epidemiological approach to the cause of atherosclerosis include: (1) misuse of cause and risk factors; (2) misuse of coronary heart disease as an imprecise and inappropriate surrogate endpoint in clinical and mortality studies; (3) use of fallacious monocausal death certificates and mortality rates; (4) assumed causal role of risk factors; (5) use of fallacious dietary data; (6) ecological fallacies; (7) nonspecificity of statistical correlations and selection bias; (8) failure to take note of inconsistencies; (9) inappropriate use of the blood cholesterol level as a surrogate of atherosclerosis (substitution game) without demonstration of any such effect on arteries; and (10) misplaced faith in pathological and experimental corroborative evidence. The epidemiology of atherosclerosis is based on unscientific methodology and the lipid hypothesis as currently envisaged is invalid. There is need to review the cholesterol-lowering campaign especially for normolipidemic subjects.

Endothelium in the aorta and ilio-femoral arteries proximal to femoral arteriovenous fistulae in rabbits

The endothelium and underlying internal elastic lamina of the aorta and ilio-femoral arteries from 15 rabbits with femoral arteriovenous fistulae (2 to 92 days postoperatively) and 3 rabbits with control femoral arteriotomies were examined using the en face technique and scanning electron microscopy. The rapidity of development of the tears in the internal elastic lamina of the muscular ilio-femoral arteries was greater than in fistulae involving the elastic common carotid artery. The elastic tissue tears appeared to have a predilection for certain anatomical regions possibly related to regions of specific hemodynamic stress. A few tears were observed in the aorta near the origin of the renal arteries. Initially the elastic tissue tears in the afferent ilio-femoral arteries were longitudinally orientated and the endothelium overlying the elastic tissue tears soon exhibited increased cell density relatively restricted to the floor of the tears. This cellular pattern was similar to that in the carotid-jugular fistulae. With time the endothelium assumed a more conventional morphology.