AV node dependent and AV node independent tachycardias

SVT can be classified into AV node independant and AV node dependant tachycardias. Sinus tachycardia, atrial tachycardias, atrial flutter and atrial fibrillation are AV node independant tachycardia because the AV nodal conduction is not necessary for the maintenance of the tachycardia. In AVNRT, AVRT and junctional tachycardia are AV node dependent tachycardias. Integral conduction of AV node is essential for the maintenance of the tachycardia in these conditions. Blocking the AV nodal conduction by drugs or manouevers terminates AV node dependent tachycardias.
Orthodromic AVRT is ruled out if there are more P waves than QRS complexes. But an antidromic AVRT can rarely have this situation.
More QRS complexes than P waves in a narrow QRS complex tachycardia can be due to junctional ectopic tachycardia, His bundle tachycardia or very rare situations of ventricular tachycardia with narrow QRS.