Normal ECG Components

An electrocardiogram (ECG) is a noninvasive medical procedure that is used extensively to evaluate and monitor the electrical activity of the heart. In order to administer the ECG, a technician places electrodes on the chest and records electrical conduction on a specialized machine that is connected to the electrodes. A normal ECG consists of a series of waves and intervals that represent the activity during a cardiac cycle. Those who have cardiac damage or who suffer from heart disease might show abnormal patterns on their tracing.

Technicians who work in cardiac care must have an understanding of normal ECG patterns if they hope to be capable of providing an initial evaluation of the quality of the test results before passing them off to a registered nurse or licensed physician for professional review. The ability to differentiate between a high quality exam and a low quality exam is one of the essential skills that is sought after in the industry and that allows the department to work efficiently to deliver comprehensive medical care. Individuals who are proficient when it comes to administering electrocardiograms are in very high demand within the industry and can expect to benefit from a variety of career opportunities and long-term job security.

Electrocardiogram Administration

The electrocardiogram is often the first test that is administered when evaluating stable individuals who are suspected of suffering from a variety of different heart conditions. Some of the most common diseases that justify the administration of an ECG include things like a myocardial infarction (heart attack), pulmonary embolism, murmur, syncope, and abnormal rhythms. While the technician is not qualified to perform an advanced evaluation of the exam results, they are generally expected to be able to administer the exam as well as ensure that the results are sufficient for an informed evaluation by a licensed healthcare provider.

A Systematic Approach to ECG Evaluation

Most advanced medical personnel use a systematic approach for reading a normal ECG that helps them ensure that all elements of the exam have been reviewed and addressed. In general, the provider will first determine if a normal sinus rhythm exists where each P wave is followed by a QRS wave and wave rates are between 60 and 100 beats per minute (bpm). Results that show a rate of less than 60 bpm are said to be in a sinus bradycardia while those above 100 bpm are said to be in sinus tachycardia. Next, the nurse or the physician will evaluate the structure and duration of the waves and intervals. Standard P waves should be less than 2.5 millimeters tall and less than 0.11 seconds wide in lead II. Abnormalities in the P wave structure might indicate a right or left atrial hypertrophy, premature beats, hyperkalemia, or some other cardiac condition.

The P wave on a normal ECG should be followed by a PR interval that is 0.12 to 0.20 seconds in duration, QRS complex that is less than 0.10 seconds in duration, QT interval that is 0.40 seconds in duration, ST segment that is not elevated or depressed, and normal T and U waves. PR intervals that are shorter than they should be may be an indication of a variety of different diseases including that of Duchenne muscular dystrophy, hypertrophic cardiomyopathy, Wolff-Parkinson-White syndrome, Lown-Ganong-Levine syndrome, and others. A prolonged PR interval may be a sign that a patient suffers from bundle branch block, hyperkalemia, or ventricular abnormalities. This level of evaluation is usually not performed by the EKG technician and should be reserved for advanced medical personnel.

A prolonged QT interval could be the result of many different types of conditions including a myocardial infarction, inflammation of the myocardium, hypothyroidism, hypocalcemia, hemorrhage, drug reactions, and hereditary diseases such as that of Jervill-Lange Nielson syndrome and Romano Ward syndrome. Elevation of the ST segment may indicate a left or right bundle branch block, pericarditis, or may be a normal variant. Depression of the ST segment could be the result of a heart attack, ventricular hypertrophy, drug effect, or a pulmonary embolus. T waves that appear abnormally tall might be a sign of a myocardial infarction, bundle branch block, or electrolyte imbalance while a flat or inverted T wave may be an indication of a heart attack, pericarditis, anxiety, drug effect, conduction delay, electrolyte imbalance, or several other important possibilities.

The Role of the Technician

Evaluating exam results to determine if they represent a normal ECG is a complex process that requires years of professional training and experience to master. While a cardiac care unit will require individuals in this profession to administer electrocardiograms and determine the quality of results, they generally do not expect an unlicensed provider to perform an advanced review or provide treatment advice to patients. Most technicians will acquire the skills they need to become successful through formal instruction and hands-on training.