Electrocardiograph: Electronic device used to record the electrical activity of the heart. The record is known as electrocardiogram (ECG). Electrocardiograph is also known as the ECG machine. The process of recording an ECG is known as electrocardiography.

What heart diseases can an ECG detect?

Any disease which can change the electrical activity of the heart leave some changes in the ECG. But often an ECG is taken to look for evidence of a heart attack at the bedside or in the emergency room. Even though it has been there for over hundred years, it is still very handy to detect a heart attack.

Other important group of disorders in which ECG is very useful are the electrical disorders of the heart which alter the rhythm of the heart. ECG shows changes when the chambers of the heart are enlarged due to other causes. Alteration in the blood level of electrolytes like potassium and calcium also leave their mark on the ECG. Many of these changes can also upset the heart rhythm. Many medications change the pattern of waves on the ECG so that it is mandatory during drug trials to check the effect on ECG.

Can a normal ECG exclude heart disease?

Just like any other test, ECG is not foolproof. Several transient changes may occur only during a particular symptom and disappear by the time the ECG is taken. Many disorders of the heart do not produce any significant ECG change, especially the milder ones. Changes noted on ECG are not often very specific to make correct diagnosis based on ECG alone. Of course we have a battery of many other advanced and modern tests for heart disease. Whether one particular test has to be done should be decided only after an expert consultation.

Can ECG be recorded continuously over a long period?

There are several methods for continuous ECG monitoring and recording. All intensive care units, operating rooms and most emergency rooms are equipped with ECG monitors. Many of these have short term recording facility which may run into a few days. Small portable devices called Holter monitors can record ECG over 24-48 hours for an ambulatory person. Extended loop recorders extend the period up to 3 months. Small implantable devices which can be implanted under the skin called implantable loop recorders (ILR) can record up to 3 years. Of course, the cost of the device goes up as the length of service period increases!

How good is the ECG analysis report provided by the modern computerized ECG machines?

Ability of the machine is similar to a human being. The accuracy of the report depends on the quality of recordings and the software installed. Even an advanced software cannot a poorly recorded ECG with a lot of artifacts well. This is the same with human interpretation as well. More advanced (of course costlier) software has been shown to be matching the skills of skilled doctor in interpretation. But most average software interpretations have to be overseen by a skilled physician. Yet the automatic interpretation is often a useful guide for a busy practitioner as it might remind you of some features which may have been missed on a quick ECG survey.