Sinus Rhythm

• P waves must be present
• P wave must have the morphology which is usual for the subect and the lead
• P wave axis must be normal (upright in II, III, AVF, and biphasic in v1)
• P wave must have same morphology in a given lead
• P wave rate must be constant
• P wave rate must be between 60-100
• There must be QRS complexes
• QRS complexed must have the same morphology which is usuall for subject and lead
• QRS rate must be constant
• There must be on p wave for every QRS complex
• P wave must be in front of every QRS
• P-R interval must be normal
• P-R interval must be constant