This mainly has to do with the location of the SA node (see here). The SA node is located in the atrial wall at the junction of the superior vena cava and right atrium.
The AV node lies near the back of the intraventricular septum near the opening of the coronary sinus (the triangle of Koch defines the AV node location)
Other fun facts from UWorld about ablation and different sites of origin, etc:
Between the tricuspid and inferior vena cava (cavotricuspid isthmus) is the most likely location of a reentrant circuit causing atrial flutter
The pulmonary vein ostia is the most likely site of origin for AFib and therefore most likely targeted for catheter ablation to correct Afib
The right ventricular outflow tract and papillary muscles are the most likely site of origin for Idiopathic VTach (though it is more commonly from ischemic tissue)
An accessory pathway bypassing the AV node is the cause of Wolff-Parkinson-White syndrome (characteristic delta wave upstroke) and AV reentrant tachycardia
A slow pathway that reenters the AV node is the cause of AV nodal reentrant tachycardia and the slow pathway would be targeted for ablation
submitted by โcassdawg(1780)
This mainly has to do with the location of the SA node (see here). The SA node is located in the atrial wall at the junction of the superior vena cava and right atrium.
The AV node lies near the back of the intraventricular septum near the opening of the coronary sinus (the triangle of Koch defines the AV node location)
Other fun facts from UWorld about ablation and different sites of origin, etc: