DEFIBRILLATOR AND PACEMAKER

DEFIBRILLATOR AND PACEMAKER 

GLOSSARY

• Heart rate: number of times the heart beats for one minute.
• Arrhythmias: It is a disorder of the heart rate (pulse) or heart rate. The heart may beat too fast (tachycardia), too slow (bradycardia) or irregularly.
•  Defibrillation: is used in cases of cardiorespiratory arrest, with the patient unconscious, with ventricular fibrillation or ventricular tachycardia without a pulse. They are deadly without treatment. 
• The electrical cardioversion: It is used to reverse all types of reentrant arrhythmias, except ventricular fibrillation. The electric shock is synchronized with the electrical activity of the heart. It can be administered electively or urgently, if the situation compromises the patient's life.

Defibrillation is based on the abrupt and brief application of a high voltage electric current to stop and reverse the rapid cardiac arrhythmias (sustained ventricular tachycardia, ventricular fibrillation); situations in which the number of heartbeats increases excessively or a disorganized electrical activity occurs, because some area or focus of the heart 'triggers' impulses in an uncontrolled manner, which are not effective or produce a hemodynamic instability (deterioration of the vital signs) that can lead a person to cardiac arrest.

The defibrillator is indicated in patients with cardiac arrest, loss of consciousness and ventricular fibrillation. When the heart beats so many times and so disorganized, it can not pump blood and therefore its activity 'stops'. Under these conditions, death ensues in a few minutes if the arrhythmia does not stop. The only measure that can prevent this outcome is electrical defibrillation.

 It is also indicated in patients with a history of myocardial infarction or dilated cardiomyopathy who have poor ventricular function who have not suffered any cardiac arrest, but who are at high risk of suffering from a dangerous cardiac arrhythmia (primary prevention).

The pacemaker is an electronic device that sends impulses to the heart to maintain the normal rhythm. An artificial pacemaker is an electronic device designed to produce electrical impulses in order to stimulate the heart when physiological or normal stimulation fails. These impulses, once generated, need a conductor cable (or electrocatheter) that stands between them to reach their goal. In this way, a cardiac stimulation system consists of a generator of electrical impulses (or pacemaker itself) and a cable.

Pacemakers, in general, are indicated for heart rhythm disorders with abnormal decrease in heart rate. And there are two main causes of an abnormal fall in heart rate:

• The inability of the sinus node (cell group where the electrical impulse that gives rise to a heartbeat originates) to produce a sufficient number of impulses per minute: also called 'sick sinus syndrome or sinus node disease'. When the nodule fails, its trigger frequency decreases (number of pulses / minute) and sometimes there are long pauses in which the heart stops beating for a few seconds. Pacemaker implantation is indicated if symptoms such as syncope (loss of consciousness), heart failure (difficulty in breathing, swelling in the legs) or angina (chest pain) occur, as long as these symptoms are secondary to bradycardia.
• The failure of the conduction of the impulses produced by the sinus node to the heart muscle: if atrioventricular AV node disorders occur (cardiac cells specialized in the formation and conduction of cardiac electrical impulses) and of the distal conduction system, The indication of implanting a pacemaker depends on the severity of the disorder and the patient's symptoms. If there is a complete atrio-ventricular block (no conduction of any of the impulses produced by the sinus node), the pacemaker is indicated; if it is of the second degree (there is no conduction of some of the impulses produced by the sinus node), it will only be applied if there are symptoms, and if it is of the first degree (all impulses are driven but with a decrease in the transmission speed) , it is not implanted. There are other circumstances in which its use is indicated.

Types of pacemakers 

Temporary pacemaker: the generator is not implanted in the patient, and can be:

•  Transcutaneous (usually included in some defibrillators): the electrodes are placed on the skin, one in the anterior part of the chest (negative electrode) and another in the back (positive electrode). 
• Intravenous (endocavitary): the electrodes are placed through a central vein to contact the endocardium. Permanent pacemaker: the generator is implanted subcutaneously.

Permanent pacemaker: the generator is implanted subcutaneously.

Pacemaker and Defibrillator code

we declared the pin of input of a button and the size of arrays 

when the button is pressed, we set a discharge of 500 ms according to the value of voltage that the person selected.

In the circuit, we show the correct connection of capacitors from where we get the voltage.

To perform the defibrillation voltage multipliers are used, these are electronic circuits composed of rectifier diodes and capacitors to raise an AC voltage to a DC voltage. The voltages used were: 18, 140 and 260 V.

For show the vector of ECG that we read from signal generator, we did with the next code where we read 80 data in total where the time between data is 1 ms, and the sampling frequency was 125 Hz.