Sinus rhythm

Sinus rhythm is the term used to refer to a normal heartbeat pattern on an EKG. There are six distinct features, each identified by a letter from P to U:
*P wave - a short upwards "hill" followed by a flat section, representing the contraction of the atria
*Q wave - a short sharp drop where the impulse passes the septum between the atria and the ventricles
*R wave - a very large and sharp straight rise to a peak well above the flat section of the P wave, representing the contraction of the major ventricles
*S wave - a sharp drop to the lowest point, followed by a sharp slight rise, representing the passage of the contraction out of the heart
*T wave - a plateau followed by a "hill" larger than that of the P wave dropping down to the plateau, representing the relaxation of the heart muscles
*U wave - a long flat plateau, leading back into the P wave, the interval between heartbeats
Not only must each part of the rhythm take place, they must also take place in the right order. "Normal" sinus rhythm has no arrhythmia, tachycardia, or bradycardia and represents a steady rhythm of roughtly 80-100 beats per minute.
Sinus rhythm at Wikipedia
Category:Cardiology