Final answer:
To treat stable narrow QRS complex tachycardia, initial interventions include vagal maneuvers and medications like beta blockers or antiarrhythmic agents, potentially followed by synchronized cardioversion or electrophysiological study and ablation if necessary. An abnormal pattern and increased frequency of QRS complexes can indicate an increase in heart rate.
Step-by-step explanation:
To treat stable narrow QRS complex tachycardia, different interventions may be considered based on the underlying cause and the presence of symptoms. Observing an abnormal electrical pattern prior to the QRS complexes and an increased frequency of these complexes could indicate a form of supraventricular tachycardia (SVT), and this would likely result in an increase in heart rate, or pulse.
Initial treatment might include vagal maneuvers to attempt to slow the heart rate, followed by pharmacologic interventions such as beta blockers or antiarrhythmic agents like procainamide. If the tachycardia does not respond to these measures or if the patient is hemodynamically unstable, synchronized cardioversion might be employed. In cases where the condition is recurrent or unmanageable with medications, an electrophysiological study and ablation may be considered.
Note that in situations where there is a third-degree heart block, the P waves are unassociated with the QRS complexes, further complicating the electrical activity of the heart and significantly affecting heart rate. Potassium channel blockers such as amiodarone and procainamide are known to affect the cardiac action potential, specifically the repolarization phase, due to their mechanism of impeding K+ movement through voltage-gated potassium channels.