Advanced age is a major risk factor for developing heart disease even in the absence of other diseases. When age increases the risk of heart disease is not very clearly known. But as age increases, a person tends to accumulate lot of “aging heart damage” due to other diseases like hypertension, dyslipidaemia (bad lipids, high cholesterol) and diabetes which have been proven to be lifestyle diseases. Besides these, habits like smoking, excessive alcohol consumption have far reaching effects on the heart when the exposure is over years and decades.
Effects on Blood Vessels
Blood vessels are composed of three layers or tunics:
- Tunica intima (inner, intimate one, made of endothelial cells)
- Tunica media (middle one made of muscle layer)
- Tunica adventitia (outermost, of connective elastic tissue)
All the three layers undergo aging changes and the end result is that the blood vessels become stiff and the heart has to pump with a larger force to keep sending out the required volumes of blood into the circulation. This is nothing but the basis of hypertension.
Endothelium: In younger individuals the endothelium secretes a variety of regulatory substances (like prostacyclin, nitric oxide, growth factors, anti adhesion factors) that decrease the pumping load on heart. As the endothelium ages these substances are progressively secreted less. As a result the blood vessels fail to dilate or get choked and in both situations it is difficult for the heart to pump.
Muscle Layer: With age the muscle layer is slowly replaced by fibrous tissue so regulating the tone of the wall becomes non-uniform.
Outer Coat: With age the elastic tissue also gets replaced by fibrous tissue. The vessels are no longer compliant and it is difficult to stretch them. Pumping blood through these stiff arteries comes as an extra effort on the ageing heart.
Effects on Heart
With the naked eye, one can see deposition of fat in the outer surface of heart. Calcification (deposition of calcium salts) is also a common change in the old hearts. The heart is made of four chambers 2 atria (receiving chambers) and 2 ventricles (pumping chambers). With age the atria dilate while ventricles don’t. This leads to a mismatch. The heart receives more blood than it can pump. It subsequently leads to congestive cardiac failure.
At the individual cell level there are some changes that become very apparent after about 60 years of age. For instance, the pace maker cells that set the rhythm of the heart beat decrease in number. This can lead to abnormal rhythms in the heart leading to arrhythmias.
The total number of heart cells also decrease and there is no regeneration once they die; the loss is more in men as compared to women. Their space is taken up by fibrous tissue which takes up only the space and serves no pumping function.
Heart at Rest: When a person is lying down the heart rate is less than it is when the person is up and about. That means when a healthy young adult sits or stands up from a lying down position, the heart rate increases. If this does not happen, the blood tends to pool in the feet due to gravity and the person feels giddy. This mechanism seems to fail for unknown reasons in old person leading to orthostatic hypotension.
The filling of the heart is affected with age. The changes that happen in the blood vessels also happen in the heart making it stiffer. The heart fails to dilate in order to accept blood. Improper filling leads to inadequate ejection even if heart pumps out all the blood that it receives.
As the atria dilate more than ventricles, there is a tendency for atrial fibrillation in which the atria only quiver and do not actually pump. Blood stays in the atrium and tends to form clots. These clots get dislodged and choke vessels in the systemic circuits leading to thromboemblolism events like stroke or gangrene of limbs.
Heart in Exercise: During exercise both the breathing and heart rate increase to meet the increased requirement of blood. In old age the maximum increase possible decreases compared to what was possible in the same person in younger days. Exertion or exercise leads to chest pain as the heart starts to overwork. That is why regular exercise is advised to keep the higher reserve margin of heart to accommodate age related decline.
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