Normal Sinus Rhythm (NSR) is the expected rhythm on an EKG in patients without pathophysiology. It is the normal electrical cycle of the heart which was discovered once a tool capable of detecting it was invented; the electrocardiogram (EKG/ECG).

Sinus Bradycardia is a Sinus Rhythm with a rate less than 60bpm and is otherwise identical to NSR. This slow rate results in a long R-R Interval on the EKG tracing and fewer complexes per length.

Sinus Tachycardia is a Sinus Rhythm with a rate greater than 99bpm and is otherwise identical to NSR. This fast rate results in a short R-R Interval on the EKG tracing and more frequent complexes per length.

Supraventricular Tachycardia is a category rather than specific rhythm. SVTs are tachycardic rhythms which originate above the ventricles.

Atrial fibrillation is the most common dysrhythmia seen clinically. It is characterized by an irregular rhythm and fibrillation waves on the EKG baseline.

AV Pacemakers can completely replace the pacemaking function of the heart. Artificial spikes before each wave of an EKG are indicative of implanted pacemaker activity.

Ventricular Tachycardia (VT) is a potentially lethal rhythm in which the ventricles have taken over pacemaking at a tachycardic rate. VT is characterized by wide QRS complexes at a rapid rate and regular rhythm.

Ventricular Fibrillation (VF, VFib) is a lethal rhythm defined by disorganized electrical activity of the ventricles. On the EKG it creates random, erratic deflections with no discernible pattern.

Asystole is the absence of electrical activity. It creates a nearly flat EKG tracing and is considered cardiac arrest.