An organ that changes with us

Risposta: The extraordinary nature of the heart is also demonstrated by its remarkable ability to adapt. During the foetal stage, whilst we are in the womb, there is a connection at the atrial level between the right and left sides of the heart known as the foramen ovale. This ensures that oxygenated, nutrient-rich blood from the mother, via the umbilical cord, passes directly into the foetus’s systemic circulation without first passing through the pulmonary circulation, as the foetus’s lungs are not yet functioning. Immediately after birth, due to changes in pressure, the foramen ovale closes and the newborn’s lungs begin to function. The first cries facilitate this process and mark the start of the coordinated functioning of the cardiopulmonary system. Over the course of a lifetime, the heart grows to support the various stages of an individual’s development, adapting to the activities that daily life presents to each of us. Its chambers can become ‘larger’ when we subject our bodies to prolonged physical activity, as is the case with long-distance runners and cyclists. Conversely, when the exertion is very intense – as in weightlifting – the thickness of the heart walls increases, much like the volume of skeletal muscles does when subjected to heavy loads. These are ‘physiological’ changes – that is, normal – and must naturally be distinguished from pathological alterations which can compromise the heart’s function if not recognised at an early stage. The thickness of the heart may increase, for example, due to valvular defects such as aortic stenosis, muscle disorders such as hypertrophic cardiomyopathy, or high blood pressure. There are also conditions that cause the heart walls to thicken due to the deposition of substances, as occurs in amyloidosis. In old age, there is a progressive reduction in the number of cardiomyocytes and an increase in the fibrous component. This fibrous component can cause electrical conduction to become more irregular, facilitating the onset of atrial fibrillation, an arrhythmia whose incidence increases with age. Another problem associated with the increase in the fibrotic component is the progressive stiffening of the ventricular walls, which become more difficult to distend during diastolic filling, thereby leading to an increase in intra-cardiac pressures. If this increase in pressure is severe, it can lead to fluid leakage into the lungs, resulting in heart failure with a preserved ejection fraction, which is common in older people. The ejection fraction is a measure of the volume of blood pumped out of the ventricle with each heartbeat.