In this situation, the P-wave morphology in leads V1 and II plays a decisive role. The P wave of sinus rhythm is biphasic (initially positive, then negative) in V1, with or without left atrial ...
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) ...