ST elevation is an indicator for a serious form of myocardial infarction (MI), also known as a heart attack. This type of heart attack is called a STEMI, which stands for ST elevated myocardial infarction. The ST segment of an ECG depicts the depolarization and repolarization of the ventricles. If the ST segment is elevated, the ventricles may not be depolarizing (contracting) and repolarizing (relaxing) properly.
A premature atrial contraction (PAC) is an abnormal event, however it is less serious than ST elevation. A PAC occurs when a node other than the sinus node, fires and electrical impulse early which causes premature contraction of the atria.
A wide QRS complex is an indicator of a bundle branch block (BBB). A bundle branch block indicates a delay or blockage on one of the electrical pathways leading to the ventricles.
Asystole depicts the absence of a heart rhythm or rate. This is seen when there are no electrical signals or contractions by the heart.
Learning Point: It is not in the medical assistant’s scope of practice to interpret an electrocardiogram (ECG), however they may need to be able to recognize the basic characteristics of various normal and abnormal heart rhythms.
Heart Rhythms
- Normal Sinus Rhythm: presence of P waves, regular, 60-100 bpm
- Sinus Tachycardia: presence of P waves, regular, above 100 bpm
- Sinus Bradycardia: presence of P waves, regular, below 60 bpm
- Atrial Fibrillation: absent/irregular P waves, irregular, usually above 100 bpm
- Atrial Flutter: sawtooth appearance, can be regular or irregular, usually above 100 bpm
- Supraventricular Tachycardia: P waves merge with T waves, regular, above 150 bpm
- Ventricular Tachycardia: absent P waves, abnormally wide QRS complex
- Ventricular Fibrillation: no measurable heart rate, irregular
- Asystole: no rhythm or rate present
- Premature Atrial Contraction: single beat with a P wave that contracts prematurely
- Premature Ventricular Contraction: single beat without a P wave and abnormally wide QRS complex that contract prematurely
