Choosing the Right Electrocardiograph

There are two main types of electrocardiographs chosen according to the type of examination to be performed:

• Resting electrocardiograph: this type of electrocardiography is performed at rest during an appointment or before an operation. It’s an essential tool that enables medical staff to monitor a patient’s general health. The electrodes connected to the electrocardiograph are placed on the patient’s bare skin (that’s been shaved and cleaned) at different places on the body (torso, wrist, ankle). These will capture cardiac electrical activity. Minimum six electrodes must be placed on the patient’s skin, but it is common to use 12, 15 or even 18.
• Stress test electrocardiograph: this type of electrocardiography is performed during physical activity, for patients with, for example, palpitations or chest pain. During the session, the patient must make an increasingly intense physical effort – usually he or she is on a treadmill with the speed increased gradually. The examination lasts on average from 10 to 30 minutes. The electrodes (fewer than on a resting electrocardiograph) are connected to a system that sometimes also measures respiratory rate and blood pressure.

A Schiller 12-channel electrocardiograph

The number of electrodes is decisive for the accuracy of the diagnosis: the higher the number, the more reliable and accurate it will be.

An electrocardiograph with four leads (three electrodes and one ground) allows for basic monitoring. It can measure the heart rate, analyze the change in heart rate, visualize P waves, QRS complex and T waves. Usually, electrodes are placed on the wrists and ankles. The electrodes on both arms and the left leg reflect the electrical variations of the heart while the electrode on the right leg serves a ground.

An electrocardiograph with 12 leads provides a more precise and accurate diagnosis by eliminating noise and disturbance from some leads. It also makes it possible to refine the diagnosis on a specific part of the heart. A standard 12-lead electrocardiograph includes six peripheral leads (also called limb leads) and six precordial leads (also called chest leads).

LUMED ECG electrodes

The type of electrodes vary according to several elements:

• Whether they are to be used for pediatric or adult care. Electrodes intended for children and infants have a smaller diameter than those for adults.
• Fixation method: metal suction cups (also called pear electrodes), pressure electrodes, clamp electrodes, lock electrodes (which can be used with cables equipped with “crocodile” type clips), clip electrodes (designed for stress tests and can be used with cables equipped with “banana” type plugs).
• Service life: resuable or single-use. Reusable electrodes are often with metal suction cups or clamps. Single-use electrodes are mainly lock electrodes and universal pressure electrodes. In the latter case, the use of this type of elecrode requires the application of electrically conductive gel.
  There are also electrodes that are equipped with more powerful adhesive. They are able to stick to the skin for several hours and are often used in intensive care and operating rooms. These electrodes can have connectors or clamps added to them.

There are several options available in order to obtain a more comprehensive diagnosis. Some options, for example, enable:

• Long-term (or continuous) monitoring: when the cardiologist suspects an anomaly in cardiac activity, he or she may request a continuous electrocardiograph. The recording is then made over a period of 24 to 48 hours using electrodes placed on the patient’s chest and connected to a case worn on the belt or as a pendant around the neck. Throughout the recording period, the patient should avoid taking a bath or shower and record his or her periods of activity and rest as well as any symptoms he or she may have experienced. This will facilitate the interpretation of the results afterwards.
• Automatic analysis of the electrocardiogram: most ECG systems are now equipped with software that automatically analyzes the measured signals in order to directly detect any pathologies of the myocardium.
• Wireless connections: some ECG systems are wireless. This means the system can be installed more quickly, making it more convenient for the specialist. The absence of some cables also reduces part of the interference, thus promoting reliable results.
• Extended cardiac monitoring: To record the activity of a patient’s heart over a long period of time, an implantable ECG system can be implanted under the skin to continuously monitor the heart rate. It can remain in place for one year and transmit the collected data by radio waves.

The analysis of an electrocardiogram is a wealth of information for a cardiologist. Cardiac pathologies that can be detected by ECG analysis include:

• Accelerated idioventricular rhythm
• Accelerated junctional rhythm
• Bundle branch block
• Asystole (heart failure)
• Tachycardia
• Atrial flutter
• A pacemaker malfunction
• Cardiac arrest
• Arrhythmia
• Bradycardia
• Ventricular or atrial fibrillation
• Wolff-Parkinson-White (WPW) syndrome
• Sinus dysfunction