What is Windkessel Effect?

What is Windkessel Effect?

എന്താണ് വിൻഡ്‌കെസൽ എഫ്ഫക്റ്റ്?

The term ‘Windkessel effect’ is used in the setting of large elastic arteries like aorta. Elastic arteries  have elastic tissue much more than the muscular arteries and are located nearer to the heart. Aorta is the largest blood vessel arising from the left ventricle, which carries oxygenated blood to the whole body. Left ventricle is the left lower muscular chamber of the heart. The other important muscular artery is the pulmonary artery, which carries blood to the lungs for oxygenation. The elasticity helps these blood vessels to maintain a relatively constant pressure gradient and flow though the heart is pumping intermittently.

The original term ‘Windkessel’ means ‘air chamber’ in German language. It was an air chamber used in fire engines in the 18th century, to maintain continuous delivery of water for fire-fighting. In the case of aorta, the aortic elasticity causes expansion and temporary storage of blood in systole so that more blood enters the aorta than what leaves it in systole. Systole is the period when the heart is contracting and ejecting out blood.

This buffer stock of blood is released during diastole, to maintain blood flow to the organs. Diastole is the period when the heart is relaxing after a contraction and receiving blood from the veins. Veins return blood from various parts of the body to the heart, while arteries carry the blood pumped out by the heart. The Windkessel effect makes aorta function as a ‘second pump’ in diastole. This diastolic flow is quite important in the case of coronary arteries as coronary blood flow occurs mostly in diastole.

Coronary arteries are blood vessels supplying oxygenated blood to the heart muscles. The branches of coronary arteries entering the heart muscle are compressed when the heart contracts in systole. So very little blood can enter the heart muscles in systole. That is why the flow into the heart muscle occurs predominantly in diastole when the heart muscle relaxes. Windkessel effect in the aorta ensures that an adequate flow into the heart muscle is possible even though the heart is not pumping in diastole.