Tuesday, January 29, 2008
Several years ago whilst on a summer trip, I looked down with alarm and noticed the tops of my feet squeezing between my sandal straps. That, to me, is one of the surest signs of advancing age--sit for a long while in a car or on an airplane, especially in the summer heat, and poof! your feet puff up. The perfect storm of venous insufficiency: aging veins dilated in an overheated car unable to transport blood efficiently from toes to heart.
Now I'm once again amongst puffy feet, this time not my own. Two of my family members (FMs #1 and #2) are struggling to stuff their feet into shoes for two different reasons:
FM #1: Venous insufficiency plus too much sitting. The road back to the heart from the furthest reaches of your body (that would be your toes) is a long and passive one. While the arteries that carry oxygenated blood from your heart to your body have elastic walls that snap smartly with each beat of the heart, propelling blood along the route, the veins have no such resiliency.
Instead, the veins rely on valves that open with each pulse beat, then close as the heart relaxes, thus preventing the backwash of blood south to the floor with gravity (see picture above of healthy and varicose veins and their valves). If your veins dilate as in varicose veins (and you can have such veins deep in your leg even if you don't see ugly varicosities on the surface), the valves are too far apart to prevent the backflow of blood.
As a result, blood oozes through capillary walls, feet and lower legs swell, and the dilated capillaries and blood pigments released cause an irritating itchy rash (stasis dermatitis). These skin changes over time cause dark pigmentation in the lower legs, and the skin is more easily injured and less easily healed.
Since venous return from the legs is entirely passive, the squeezing action of the leg muscles is an important extra push to keep the blood moving upwards. Prolonged sitting because you're stuck in the middle seat of row 25 in coach, or perhaps because you're so old and your knees so bad that you're disinclined to get up, takes the muscular pump out of the equation. Add gravity sucking blood southwards and there go the feet into puffiness.
FM #2: Right-sided congestive heart failure plus too much sitting. The right side of the heart is responsible for boosting deoxygenated blood returning from the body into the lungs where it can pick up a new load of oxygen. When the lungs are diseased, say from emphysema, the lung tissue is far less efficient at delivering oxygen across the barrier to the blood. The blood vessels constrict in some misguided effort to bypass the damaged part of the lung (but, unfortunately, the whole darn lung is damaged), and the pressure rises in the narrowed arteries.
As a result, the right heart is now working much harder to push blood into these constricted arteries, and it starts to enlarge and fail. With each beat of the heart, less blood is emptied into the arteries heading for the lungs, and blood starts to back up in the body, particularly in the legs and in the liver. Add inactivity due to lung disease to the equation, and the legs and feet puff up.
Whether the lower extremities swell from inactivity, venous insufficiency, or heart failure, the blood is slowed and sludging in the veins of the leg. If Mr. or Ms. Bigfoot has a clotting problem--inherited, secondary to use of oral hormones such as birth control pills or HRT, as a result of cancer, or due to injury or recent surgery--this sludgy blood can clot. Clotted veins in the legs further aggravate the swelling, and if a glump of clot breaks free and travels up the veins and into the lungs, it can cause a pulmonary embolus which further accentuates right heart failure or, if big enough, stops heart function suddenly...and fatally.