Poor Circulation in the Legs, Impaired Blood Flow and Blood Clots

Blood flow to the legs, as is the case with any part of the body, is via the arteries and veins. Arteries carry oxygen-rich blood to the site, while veins transport oxygen-depleted blood away and back to the heart. Any excess fluid in the tissue spaces drains into the lymphatic vessels that eventually empties into the veins. Poor blood flow to the legs can be broadly termed as peripheral vascular disease (PVD). This includes any disease that impairs blood flow through the arteries or legs. However, the term has become synonymous with peripheral arterial disease (PAD) which is a problem with the blood flowing through an artery.

Poor blood circulation in the legs is a common problem. It may be due to a disruption in either the arteries or veins and less commonly in both simultaneously. The legs, and particularly the feet, being the furthest point from the heart are more prone to these conditions. Normally the pressure created by the pumping heart propels blood to any given site and there is sufficient force to return the blood back to the heart. However, with the legs, specialized mechanisms exist to assist with this process due to the distance from the heart.

Poor Arterial Circulation to the Legs

Arteries may become blocked, narrowed, hardened or inflamed. This can disrupt the blood flowing through it. With regards to the legs, the most common cause of impaired arterial blood flow is the build up of atheromatous plaques in the wall of the artery. This condition is known as atherosclerosis and can affect just about any artery in the body. It is often associated with hypertension, diabetes mellitus, hyperlipidemia and lifestyle factors like inactivity and cigarette smoking.

The plaques gradually develop within the artery and partially occludes the blood flowing through it. Initially it may be asymptomatic but with time it leads to  leg pain, particularly in the calves, during activity (claudication). Although the causes may vary, it is broadly referred to as peripheral arterial disease (PAD). Sufficient quantities of oxygen-rich blood cannot reach the lower leg and feet leading to tissue injury (ischemia) particularly when the oxygen demands are greater like during walking or running.

Poor Venous Circulation in the Legs

The leg veins carry blood back to the heart. There is a superficial and deep system that drains the feet, lower legs and thighs. The leg veins are somewhat unique in that it has valves which are not seen in most veins. These valves help to carry blood back to the heart since there is insufficient pressure created by the heart to return the blood effectively.

The muscles of the lower legs and feet also act as a pump and push the blood through the veins. A sedentary lifestyle, standing for long periods, obesity and pregnancy are some of the common causes of valvular insufficiency. Blood collects in the legs, the veins distend and the valves become incompetent. This is less likely to cause pain as is the case with impaired arterial circulation through the legs but often leads to leg swelling and engirgement of the veins that may be visible particularly the superficial veins (varicose veins). This condition is broadly termed venous insufficiency of the legs.

Blood Clots in the Legs

In both poor arterial and venous blood flow of the legs, a clot may form at the site where the vessel is narrowed or blood is pooling. It exacerbates the underlying condition and severely hampers the already limited blood flow. In the narrowed artery, the clot may almost totally occlude the blood flow and lead to acute limb ischemia. In the vein, a clot that forms particularly within the deep vein system, which is known as deep venous thrombosis (DVT), can dislodge and block blood flow through the lungs (pulmonary embolism). Both conditions may have dire consequences and even prove to be fatal.

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