How does a defibrillator work? To be clear, that device that is used in the medical field to restore normal heart rhythm. And above all, why do you give an electricity to the heart in case of cardiac arrest? These are the questions that we ask ourselves every time we talk about defibrillators. But to truly understand the functioning of this life -saving device, it is necessary to start from the bases: the heart and its rhythm.
The heart is an involuntary muscle
The heart can be conceptually assimilated to a pump. It is in fact a muscle that, alternating two phases: that of relaxation and that of contraction. Thanks to this rhythmic mechanism, the heart receives blood low in oxygen, sends it to the lungs to oxygenate it and then pumps it again in the rest of the body, starting the cycle again. The structure of the heart is divided into Two distinct half – Right and left – just to separate the two blood flows, guaranteeing efficient circulation.
This circulation is made possible by cardiac contractions, which take place completely autonomously, without the need for conscious control. The heart is in fact a involuntary muscle. But how does this spontaneous contraction take place? Through electrical impulses.
The walls of the heart consist of billions of muscle cells which, if electrically stimulated, contract. A cell, after counterattack, must complete the release phase before being able to respond to a new stimulus. The electrical stimulus that makes them contract originates in a specific point, called breast node And it spreads in the heart following a precise path. The correct timing with which this impulse reaches the various “control points” is fundamental for the functioning of the heart.
Functional anatomy of the heartbeat
The heart is divided into two sections, each composed of a lobbywhich welcomes the blood, and from a ventriclewho puts him back in the circulation. A valve is between atrium and ventricle that guarantees the correct flow of blood.
The electrical signal starts from the breast node and causes the contraction of the Atri, which push the blood towards the ventricles. The impulse then passes to the atrio-ventricular node, crosses the HIS bundle and is divided into ventricular branches, causing the contraction of the ventricles and the expulsion of the blood from the heart. This electric sequence is the basis of the heartbeat. But in addition to the sequence, it is essential that the electrical stimulus reaches every point with the right timing: this defines the cardiac rhythm.
The electrocardiogram (ECG) detects the passage of the electric impulse in the various points of the heart. The highest track represents the depolarization of the ventricles, that is, their contraction. Through the ECG, doctors can identify any cardiac rhythm anomalies. The number of beats per minute, that is, the frequency, can vary, for example during physical activity, but the beat itself must always be the same. Otherwise, we talk about cardiac arrhythmia. Arrhythmias can take different forms, and one of the most serious is the heart attack, or the necrosis of the myocardium caused by an interruption of the bloodstream.
Because the defibrillator is used and how it acts
The defibrillator comes into play in the presence of serious irregularities of the heart rhythm. In these cases, one Download targeted electricity He can “reset” the cardiac rhythm. The electric discharge simultaneously depolarize all cardiac muscle cells, allowing the heart to “start again” with a correct cardiac rhythm. Each defibrillator is equipped with two adhesive plaques to be applied on the chest. These allow to monitor heart activity and detect any arrhythmias. Once the problem is identified, the power of the discharge is set and the plates are activated. Manual defibrillators require the intervention of qualified personnel, able to interpret the ECG and correctly dose the discharge. Today, however, the Semi-automatic defibrillators (DAE). These independently detect arrhythmia, set the energy and administer the discharge independently, requesting only the correct application of the plates.
Defibrillation is often followed by cardiopulmonary resuscitation (RCP). When the heart stops, the flow of blood oxygenated to the vital organs is also stopped, first of all the brain. The RCP serves to maintain a minimal circulation until the restoration of the beat.
Plant pacemaker and defibrillators: differences
Defibrillation is also present in the functioning of artificial pacemaker. However, while i Pacemakers provide continuous impulses To compensate for a permanent chronic defect – such as, for example, a specific part of the heart that is no longer able to contract independently – i implantable defibrillators come into operation only in the event of an emergencywhen they detect potentially fatal arrhythmia.
