Sinus tachycardia is indicated on ECG with a normal upright P wave in lead II preceding every QRS complex (indicating that the pacemaker is coming from the sinus node and not elsewhere in the atria) with an atrial rate of greater than 100 per minute.
Usually the ventricular rate (indicated by the QRS complex rate), is also greater than 100 since in most cases the P wave conducts through the AV node to the ventricles to produce a QRS complex in a 1:1 fashion. On occasion the sinus rate can be different than the ventricular rate (AV dissociation) such as in ventricular tachycardia or complete heart block. Treatment is aimed at the primary cause. The differential diagnosis for sinus tachycardia includes:
- Dehydration or shock
- Chronic pulmonary disease
- Decompensated congestive heart failure
- Pulmonary embolus