The human heart starts to beat around the 21st day of life at a rate similar to the mother’s heart rate of about 75beats per minute. This rate increases and then decreases slightly through the fetal period. By the time the baby is born, the heart rate is about 145beats per minute. The heart beat can be heard by listening with the ordinary ear or with the aid of a stethoscope over the chest. It is loudest over a point marked by the intersection of an imaginary line running horizontally in the space between the 5th and 6th left ribs and an imaginary vertical line running down from a point just to the right of the midpoint of the left collar bone. This point is called the apex; it is the lowermost and outermost part of the heart and it is the point of maximal cardiac impulse.
The normal heart sounds are the sounds produced by turbulence in the heart as a result of the closure of valves as the different heart chambers contract and relax to pump out and receive blood respectively. The sounds are designated with the letter S, with S1 being the first heart sound (also referred to as lub) and S2 the second heart sound (also referred to as dub).
lubdub lubdub lubdub lubdub lubdub lubdub lubdub lubdub lubdub…………………
Sometimes, extra sounds may be heard by a doctor with the aid of a stethoscope. There may be 3rd and 4th heart sounds (S3, S4) or Murmurs. A murmur may or may not be a sign of a heart disease; for instance, hyper dynamic states in which there’s more blood flowing through the heart can result in turbulence which is heard as a murmur. Such states may be caused by fever, anemia, hyperthyroidism and pregnancy. With the reversal of the condition, the murmur also disappears. However, a murmur may be caused by heart disease, most often a congenital defect such as holes in the septum or valvular abnormalities. Heart valves may also be damaged by certain infections or age related changes.
In an adult, the normal rate of the heart is between 60-100 beats per minute. A rate faster than 100bpm is generally referred to as tachycardia while one slower than 60bpm is called bradycardia. There are many conditions which may lead to tachycardia or bradycardia. Some of these are physiological i.e due to normal body adjustments e.g the heart rate of an athlete is expected to be slower than average. Sudden fright or anxiety can, on the other hand, cause tachycardia which is only temporary and resolves when the cause is taken away. Substances such as caffein, nicotine (in cigarette), drugs of abuse, prescription drugs may also cause changes in the heart rate. However, low heart rate or high heart rate may sometimes be manifestations of heart disease or other diseases.
The most common symptom of a change in the rate or rythm of the heartbeat is palpitation. This refers to a sense of awareness of the heart beat. It could be disturbing and quite distressful.
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| heartfailurematters.org |
The heartbeat, normal or abnormal, can provide a large amount of information about what is going on in the heart as well as other parts of the body, therefore auscultation for the heart sounds is a vital part of the medical examination.
lub dub
edited on 28/11/11
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