Pacemaker artificial

Pacemaker, dispozitiv electronic de suport cardiac care produce impulsuri electrice ritmice care preiau reglarea bătăilor inimii la pacienții cu anumite tipuri de boli cardiace.

boli cardiovasculare: stimulatoare cardiace

Ritmul normal al inimii este generat de activitatea electrică spontană în celulele dintr-o zonă a inimii numită nod sinoatrial.

O inimă umană sănătoasă conține propriul sistem de conducere electrică capabil să controleze atât ritmul, cât și ordinea contracțiilor cardiace. Impulsurile electrice sunt generate la nodul sinoatrial din atriul drept, una dintre cele două camere superioare ale inimii. Ei trec apoi prin mușchii ambelor atrii pentru a declanșa contracția acelor două camere, care forțează sângele în ventricule. Valul de activitate electrică atrială activează un al doilea plasture de țesut conductiv, nodul atrioventricular, inițierea unei a doua descărcări de-a lungul unui ansamblu de fibre conductoare numit mănunchiul lui, care induce contracția ventriculelor. Când conducta electrică prin nodul atrioventricular sau mănunchiul lui este întreruptă, starea se numește bloc cardiac.Un stimulator de stimulare artificială poate fi folosit temporar până când revine conducta normală sau permanent pentru a depăși blocajul.

In temporary pacing, a miniature electrode attached to fine wires is introduced into the heart through a vein, usually in the arm. The pacing device, an electric generator, remains outside the body and produces regular pulses of electric charge to maintain the heartbeat. In permanent pacing, the electrode may again be passed into the heart through a vein or it may be surgically implanted on the surface of the heart; in either case the electrode is generally located in the right ventricle. The electric generator is placed just beneath the skin, usually in a surgically created pocket below the collarbone.

The first pacemakers were of a type called asynchronous, or fixed, and they generated regular discharges that overrode the natural pacemaker. The rate of an asynchronous pacemaker may be altered by the physician, but once set it will continue to generate an electric pulse at regular intervals. Most are set at 70 to 75 beats per minute. More-recent devices are synchronous, or demand, pacemakers that trigger heart contractions only when the normal beat is interrupted. Most pacemakers of this type are designed to generate a pulse when the natural heart rate falls below 68 to 72 beats per minute.

Once in place, the electrode and wires of the pacemaker usually require almost no further attention. The power source of the implanted pulse generator, however, requires replacement at regular intervals, generally every four to five years. Most pacemakers use batteries as a power source.

Pacemakers designed to communicate wirelessly, using radio-frequency telemetry-based technology, have enabled physicians to gather information about a patient remotely. The implanted pacemakers transmit information to home monitoring systems and to programming devices used by doctors. As a result, a doctor working in a clinic can collect important information about a patient’s heart function while the patient is at home. This type of wireless device also sends out alert signals to the physician when the patient’s heart rate becomes abnormal.