Electronics/Medical Equipment

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Holter monitor[edit]

From Wikipedia, the free encyclopedia : Holter monitor

A Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. Its extended recording period is useful for observing occasional cardiac arrhythmias that would be otherwise difficult to identify in a shorter period of time.

Configuration

Much like standard electrocardiography (EKG), the Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest. The number and position of electrodes varies by model, but most Holter monitors employ from three to six. These electrodes are connected to a small piece of equipment that is attached to the patient's belt, and is responsible for keeping a log of the heart's electrical activity throughout the recording period.

Event diary

In addition to receiving the device itself, most patients are also asked to keep a diary of activities, symptoms, and times that an arrhythmia occurs. This information is used by doctors and technicians to rapidly pinpoint problem areas in the vast amount of data recorded during the monitoring period.

External links

Defibrillator[edit]

From Wikipedia, the free encyclopedia : defibrillator

A defibrillator is a device that performs defibrillation on the chambers of the heart. The device may be implanted in the user of the device. If so, it is known as an implantable cardioverter-defibrillator or internal cardiac defibrillator (ICD).

External defibrillators are available in all hospitals and are commonly available in ambulances. The use of externals defibrillators is taught in advanced cardiac life support.

In recent years, an automatic external defibrillator has been made available for use by the general public. These devices are commonly found in large gathering places, such as airports, casinos, and sports stadiums.

See also: CPR, advanced cardiac life support, cardioversion, implantable cardioverter-defibrillator, defibrillation, automatic external defibrillator

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Defibrillation[edit]

From Wikipedia, the free encyclopedia : defibrillation

Defibrillation is a medical technique used to counter the onset of ventricular fibrillation, a common cause of cardiac arrest. The equipment used in this process is called a defibrillator. Defibrillation is part of advanced cardiac life support.

Defibrillation is a technique used in emergency medicine to save lives when the heart is in an abnormal or damaging rhythm. The most common indications for emergency defibrillation is for ventricular fibrillation and ventricular tachycardia.

Often, ventricular fibrillation is preceded by ventricular tachycardia. While these are both fast rhythms in the lower chambers of the heart (the left and right ventricles), ventricular tachycardia is a more organized rhythm, while ventricular fibrillation is described as chaotic activity of the ventricles. While ventricular tachycardia can lead to ventricular fibrillation, it may break on its own, allowing the person's normal rhythm to resume. Ventricular fibrillation never breaks on its own, and will always lead to death if it is not terminated quickly. Ventricular tachycardia may be associated with an adequate blood pressure to perfuse the brain. Often, however, the heart is beating too fast for blood to enter the heart, causing a low blood pressure and decreased perfusion of the brain and other vital organs. In ventricular fibrillation, since the electrical activity in the ventricle is chaotic, there's no organized pumping of blood, and therefore there is no blood perfusion of the brain.

The purpose of defibrillation of ventricular arrhythmias is to apply a controlled electrical shock to the heart, which leads to depolarization of the entire electrical conduction system of the heart. When the heart repolarizes, the normal electrical conduction may assert itself, in which case the ventricular arrhythmia is terminated. However, if enough energy is not used for defibrillation, the heart may not be completely depolarized, in which case the ventricular tachycardia or fibrillation may not be terminated. Also, if the heart itself is not getting enough oxygen or if there is an instability of the electrolytes in the cardiac cells, the ventricular arrhythmia may recur.

If there is no electrical activity in the heart (electrical asystole, or standstill), then the heart is already depolarized, and defibrillation will have no effect.

Although the process of defibrillation can be repeated, the number of attempts is, in practice, limited, to a series of three or four attempts at increasing voltages, as the likelihood of restoring normal heart rhythm is much less in successive attempts.

Increasingly, automatic external defibrillators (AEDs) are being made available at airports, shopping centres, etc.

Defibrillators can also be implanted (implantable cardioverter-defibrillators or ICDs) in people at high risk of developing an arrhythmia. The ICD is rather like an artificial pacemaker, and indeed performs all the functions of a pacemaker, but it can also deliver a defibrillation shock if a dangerous arrhythmia is detected.

See also: CPR, advanced cardiac life support, cardioversion

Automated external defibrillator[edit]

From Wikipedia, the free encyclopedia : Automated external defibrillator

An automated external defibrillator is used to detect and treat emergency severe heart arrythmia such as ventricular fibrillation (v-fib) and Ventricular tachycardia (v-tach). Uncorrected, these conditions will rapidly (within minutes) lead to cardiac arrest and death.

V-fib is a condition wherein the electrical system of the heart is pulsating in a chaotic manner, resulting in an ineffective transfer of blood from the heart to the body (and brain), which ends in cardiac arrest. V-tach is a condition wherein the heart is beating too fast to render effective transfer of blood from the heart to the body (and brain). Frequently, v-tach can lead to v-fib. A defibrillator clears the electrical system (a reboot of sorts) and allows it to start over.

The Automated External Defibrillator is automated in that the shock level is not user-selectable, and the user cannot override "no shock" advice. It is external in that there are pads that are attached to the patient/victim, rather than an implant surgically placed in the patient/victim's chest.

Once the pads are attached to the patient, the machine will analyze the rhythm of the patient's heart and determine if a shock is necessary to treat v-tach or v-fib. If the machine determines that a shock is necessary, it will charge up and prepare to deliver the shock. When the machine is prepared, it will notify the user, and instruct the user to make user no one is touching the patient and then press a button on the machine to actually deliver the shock.

After the shock is delivered, the machine will monitor the patient's rhythm to determine if further shocks are necessary.

If the patient's heart rate is too slow, these devices typically do not pace the heart to make it beat faster.

All AEDs manufactured and approved for use in the US feature a synthesized voice prompting the user or users through every step of use. They are particularly made to be operated by untrained and minimally trained individuals. The use of AEDs is taught in Basic Life Support (BLS) classes nation-wide.

Asystole[edit]

From Wikipedia, the free encyclopedia : asystole

In medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Asystole is one of the conditions required for a medical practitioner to certify death.

Cardioversion[edit]

From Wikipedia, the free encyclopedia : cardioversion

Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms.

Similar to defibrillation, cardioversion differs in that it uses much lower electricity levels. Cardioversion may also be done through medication instead of an electrical shock.

EKG (Electrocardiogram)[edit]

From Wikipedia, the free encyclopedia : Electrocardiogram

Lead II An Electrocardiogram (abbreviated as either ECG or EKG from German, Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical current in the heart in the form of a continuous strip graph. The ECG results provide the following:

  • Determine whether the heart is performing normally or suffering from abnormalities (e.g. extra or skipped heartbeats - Cardiac arrhythmia).
  • May indicate coronary artery blockages (during or after a heart attack).
  • Can be used for detecting calcium, magnesium and other electrolyte disturbances.
  • Allows the detection of conduction abnormalities (heart blocks).
  • Indicates the physical shape of a patient during stress tests.
  • Can provide information on the physical condition of the heart (i.e.: left ventricular hypertrophy).

Details[edit]

The EKG complex. p=p wave, PR=PR segment, QRS=QRS complex, QT=QT interval, ST=ST segment, t=t wave.

A typical ECG tracing of a normal heartbeat consists of a p wave, a QRS complex and a t wave. The p wave is the electrical signature of the current that causes atrial contraction. Both the left and right atria contract simultaneously. The QRS complex corresponds to the current that causes contraction of the ventricles, which is much more forceful than that of the atria and involves more muscle area, thus resulting in a much greater ECG deflection. The QRS complex contains the atrial repolarization current. The t wave represents the repolarization of the ventricles. Electrically, the cardiac muscle cells are like loaded springs. A small impulse sets them off, they depolarize and contract. Setting the spring up again is repolarization (more at action potential).

Lead I[edit]

A typical ECG report shows the cardiac cycle from 12 different vantage points, like viewing the event elecrically from 12 different directions. Understanding the usual and abnormal directions, or vectors, of depolarization and repolarization yields important diagnostic information. The directions, or vectors, are known as leads. The inferior leads are II, III and aVF, the lateral leads are I and aVL. The chest, or anterior leads are V1 through V6. aVR is rarely used for diagnostic information, but indicates if the ECG leads were placed correctly on the patient. Inferior, lateral and anterior refer to portions of the heart. The inferior leads record events from the apex of the left ventricle. The lateral and anterior leads record events from the left wall and front walls of the left ventricle, respectively. The right ventricle has very little muscle mass. It leaves only a small imprint on the ECG, making it more difficult to diagnose than changes in the right ventricle.

Notes[edit]

The device has become so familiar with its depiction in various television medical dramas to the point where the reading of no cardiac electrical activity nicknamed flatline is often used as a symbol of death or at least extreme medical peril. This is technically known as asystole.

Related topics[edit]

  • advanced cardiac life support
  • cardiac arrest
  • Holter monitor

External links[edit]