MadSci Network: Anatomy
Query:

Re: Why would somebody with defective heart valves be unlikely to beome athlete

Date: Mon Sep 10 07:35:21 2001
Posted By: David Burton, Post-doc/Fellow, Physiology, University of Oxford
Area of science: Anatomy
ID: 999792536.An
Message:

Hello Sami,

The valves of the heart are there to control the flow of blood through the chambers of the heart so that it works most efficiently.

The heart contains 4 chambers. Two chambers on the right side of the heart and two on the left. On each side of the heart there is an atria and a ventricle. The right side of the heart receives deoxygenated blood from the tissues and is fed by a very large vein, the vena cava. The right side of the heart pumps blood to the lungs where it is oxygenated and then returns to the left side of the heart. The chambers of the left side of the heart have much thicker walls and pump blood round the body to the muscles, brain and all other tissues.

The blood flows into the heart between beats and collects in the first chamber on each side of the heart, the left and right atria. The atria are relatively small chambers and can be thought of as the storage chambers of the heart where the blood is collected between beats. The first part of the heartbeat is the contraction of the atria. These pump all the blood into the left and right ventricles. As the atria contract the increased pressure in the chambers forces valves between the atria and the blood vessels that supply them closed and valves between the atria and ventricles open. This ensures that all the blood ejected by the contraction of the atria flows into the ventricles and not back to where it came from.

Shortly after this the ventricles contract. The contraction of the ventricles forces shut the valves between the ventricles and the atria and it opens valves to the aorta and pulmonary artery, the blood vessels that take the blood away from the heart to the body and lungs respectively. Therefore all the blood will be ejected from the heart and none will be regurgitated back into the atria.

When the ventricles relax filling of the heart starts again and valves close to stop the regurgitation of the ejected blood back into the heart from the arteries. Therefore the valves of the heart serve a vital function in ensuring the coordinated flow of blood through the heart.

When you listen to a heartbeat what you are actually hearing is these valves slamming shut during the phases of the heartbeat. The details of what makes these sounds can be found in the answer to previous question on heart sounds. You can hear heart sounds by placing your head on someone's chest. The heart makes a lubb dubb sound each beat. The lubb is from the closing of the valves between the ventricles and the atria as the ventricles contract. The dubb is from the closing of the valves between the ventricles and the arteries that carry the blood away from the heart.

If there is a problem with the valves working properly this is heard as a 'heart murmur'. A heart murmur is a whooshing sound caused by a leaky heart valve. If a valve does not close properly some of the blood will be forced through the gap and will therefore flow the wrong way through the heart. This means that not all the blood will be ejected from the heart on each beat and therefore the volume of blood ejected from the heart on each beat, known as the 'cardiac output' will be reduced.

I hope you can now see where I am going with this to answer your question. If someone has leaky heart valves resulting in a decreased cardiac output then their heart will have to beat more times per minute to eject the same volume of blood as a heart with valves working properly. There is a maximum rate that the heart can beat at, which is approximately 220 beats per minute minus your age for a human heart (e.g. 190bpm for a 30 year old person). Strenuous physical exercise can be maintained at a heart rate of around 85% of the maximum rate (162 beats per minute for a 30 year old) but any higher than this and the person will fatigue quickly. Part of an athletes training is to push this to the limit so that a trained athlete can possibly maintain exercise at over 90% of their maximum heart rate without fatigue setting in quickly. Therefore during strenuous physical exercise there is no reserve capacity for the heart with a leaky valve to beat faster to compensate for the decreased cardiac output. Therefore this places an individual with a leaky heart valve at a considerable disadvantage and means that they are unfortunately unlikely to become an athlete.

I hope that this is all clear and thank you for your question.

David Burton


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