From: Steve Harris <sbharris@ix.netcom.com> Newsgroups: sci.med.cardiology,sci.med Subject: Re: dietary fat & cardio deaths: quality not quantity Date: 21 Jan 2005 20:04:39 -0800 Message-ID: <1106366679.106920.217530@c13g2000cwb.googlegroups.com> COMMENT: It's way too complicated a subject to discuss fully. The short form (which I can't do justice, so this is only approximate) is that vascular aging per se in absense of atherosclerosis can be studied in animals like the rat that don't get atherosclerosis or hypertension on standard diets. As they age, you can see standard "successful aging" which thickens the artery lining "intima" a bit, and causes the main wall "media" to expand and lose some elasticity. None of these things is enough to cause increases in pressure. Actually, what typically happens is diastolic pressure drops and systolic pressure remains the same, so that pulse pressure (systolic minus diastolic, or upper number minus lower one) increases a little without any hypertension. This happens as blood pressure characteristics come to be set by the large arteries and their characteristics in advanced "healthy" aging, as opposed to being set by small artery tone. This is pretty much what happens in humans in the absense of disease, with aging. It's what is seen in undeveloped countries in people on a very low fat diet, who never get atherosclerosis or hypertension. Normal aging is a pulse pressure of 40 at age 40 and about 60 at age 80. Anything above a pulse pressure of around 80 at 80 usually means there's some artery damage by more than healthy aging. By what? Well, hypertension itself, and diabetes, both cause worse intimal thickening and worse elasticity, so it looks like aging changes, but worse. Atherosclerosis, a local fatty-tumor-like injury disease disease in blood vessels, has many causes, but starts with injury to the intima due to flexion or hypertension or chemical causes. You see it where arteries flex a lot, like the neck, the groin or knee, or in the bouncing heart. It starts with infiltration of the intima with foamy lessions, which eventually coalese into plaques.These are generally non-concentric and bulge into the artery from one side. This does NOT in an of itself increase the pressure. If blood can't go through, it just doesn't. Systemic pressure increases per se (systolic and diastolic increases) are due to disease mechanisms of other types, occuring in the smaller arteries, NOT due to disease like atherosclerosis in larger arteries. These pressure increases in turn cause damage (intimal thickening and loss of elasticity) in larger arteriies, as above, but cause and effect are in the direction indicated. The pressure increases cause the thickening in large vessels but not the reverse (the thickening and elasticity loss per se causes increased pulse pressure, but NOT hypertension). Similarly, hypertension also causes atherosclerosis, but NOT the other way around (with the exception occasionally of lessions in kidney arteries which directly cut off the kidney blood pressure sensing mechanisms, and can result in high blood pressure that way-- but this is rare and generally isn't the way it happens). SBH From: Steve Harris <sbharris@ix.netcom.com> Newsgroups: soc.culture.indian,alt.fan.jai-maharaj,misc.health.alternative, sci.med.cardiology,sci.med Subject: Re: Blueberries lower LDL cholesterol better than statin drugs Date: 27 Jan 2005 16:01:13 -0800 Message-ID: <1106870473.303658.218160@f14g2000cwb.googlegroups.com> Arteriosclerosis is not a disease but a general wastebasket term for at least 3 varieties of a hardening of the arteries by some pathological mechanism. It's not a very useful term, since even normal aging hardens arteries somewhat by making them thicker and less elastic. However this normal aging process is not normally considered arteriosclerosis. Atherosclerosis is named for atheroma-- a sort of Greek gruel. The junk in the center of placques reminded somebody (Virchow?) of that. Risk factors are the usual ones for heart disease. For descriptions of the less common kinds of arteriosclerosis, which are arteriolar sclerosis (which affects small vessels and has hypertension as main risk factor), and also for the Monckeberg arteriosclerosis which involves calcification of larger arteries and looks horrible on X-ray but actually isn't clinically all that important, see: http://www.well-net.com/cardiov/arterios.html |