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Collateralblood vessels

Researchers have tried to stimu-late collateral blood vessels by bath-ing them with protein growth factorsand bombarding them rvith gro*'th-promoting genes. So far, these ellbrtshavent paid off. You can succeedwhere they harent-by exercising.

When you exercise, you dramati-cally boost blood flow through thecoronary arteries. The inner lining ofthe arteries responds to this "stress"much as it does to the stress of ath-erosclerosis, by stimulating tinycollateral blood vessels to elongate,

angioplasty offers the best way to halt rviden, and form new connections.a heart attack. Ideally, such emergency A little bit of exercise won't do theangioplasty should be done no more trick. You need to push your heart. Ifthan trvo to three hours after heart you arent used to exercising, that mayattack symptoms start. A German team mean brisk rvalking. If you rvalk, addhas shorvn that this treatment windorv in spurts of race walking or jogging.might stay open longer in people with Swimming, bicycling, hiking-any

Limit hear t aft ack d am age. |apaneseresearchers have shown that peoplewith well-developed collateral circu-lation have smaller areas of damagedmuscle after a heart attack than thosewith poorer collateral circulation.

Provide extra time for effiergencyheart attack therapy, Artery-opening

Crowing around blocked arteriesNormalcirculation Collateralcirculation

two. They are the byproducts of deskjobs, plentiful food, stress, lack ofexer-cise, and a host ofother factors.

If the development of collateral ves-sels was the body's fail-safe responseto atherosclerosis, relatively ferv peo-ple would have angina or other fbrmsof ischemic heart disease (the kind

caused by poor blood flow to theheart muscle). Unfortunately, noteveryone is genetically programmedto effortlessly grow collateral bloodvessels. Unhealthful habits also getin the way.

activity that gets your heart beatingfaster-will do as long as you keep itup for 20 to 30 minutes a crack and doit several times a week.

Exercise is a great way to preventheart disease. And a host of studiesshow that it can help some people withnarrowed coronary arteries safely avoidbypass surgery or angioplasty. It's alsogood for the bones, brain, and justabout every other part ofthe body. Sowhy not give yourself a natural bypassbefore you need a surgeon to performa more painful and hazardous one? ll

January 2OO8 | Harvard H€art Letter O

Nanowedcoronary artery

When cholesterol-filled plaque or anotherobstruction restricts blood flow (red anows)

healthy collateral circulation.Improve survival.In a study pub-

lished last year of more than 800 menand lvomen lvith stable coronary arterydisease (chest pain with exertion orstress), 89o/o of those with good col-lateral circulation were still alive afterl0 years of follorv-up, compared with71% of those rvith low collateral flow.

Bypass l:efore surgeryMost Americans, including those rvith-out any outward signs ofheart disease,have a narrowed coronary artery or

Harvard HeartletterDo-it-yourself bypassHelping your heart grow new blood vessels is a natural way to bypass cholesterol-clogged coronary arteries.

f\ icture this: You are drivingfl ao*r, a city highway rvhen tral

-jL fic grinds to a halt. You can seea miles-long backup behind a distantconstruction crew that has closed offthe two right lanes. Knowing the area,you merge over to a nearby exit, thenfollow a detour onto streets that runalmost parallel to the highway. Oncebeyond the bottleneck, you re-enterthe highway.

That's similar to what happenswhen cholesterol-filled plaquebegins to narrow a coronary artery.Blood vessels respond to the slowstealthy attack of artery-cloggingatherosclerosis by generating a hostof chemical and physical signals. Animmediate action of these signals isto improve blood flow beyond thenarrowing. They also bulk up tinyblood vessels that have been sittingidly in the heart since birth. As thesecollateral vessels grow larger, moremuscular, and more interconnected,they begin to reroute some of theblood flow around the blockage (see

"Grorving around blocked arteries").Such a natural bypass can keep theheart well supplied with oxygen-richblood, much as its surgical counterpartcan do.

-Sclentists have been trying for yearsto nudge collateral blood vessels todevelop and prosper, but without greatsuccess. You can do it at home withoutanything more high-tech than a com-fortable pair ofshoes.

Collaterals for insuraneeMeasuring the extent of collateral cir-culation, or blood flow through it, isnteasy. That's one reason rvhy it has beendifficult to document the impact ofhaving, or not having, good collateralcirculation. That said, studies from the1950s onward highlight the potentialof this network of recruitable bloodvessels. They can:

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