Mahaim Tachycardia

From Ask Dr Wiki

Features

1. Absent or minimal preexcitation
2. Tachycardia generally exhibits a LBBB with LAD
3. Right Atrial Pacing leads to more pre-excitation with shorter stimulus to delta interval than Left Atrial Pacing
4. Decremental Antegrade Conduction is evident
5. Retrograde conduction over the pathway is absent
6. Earliest Ventricular Activation is usually (but not always) near the RV apex
7. Most common tachycardia is antidromic AVRT

Features Separating Atriofascicular from Long Atrioventricular

1. Atriofascicular pathways have narrower pre excited QRS (113ms versus 165ms), so atriofascicular QRS should be < 145ms with rapid QRS onset in I and/or V1
2. Atriofascicular have shorter retrograde V-H times (16ms versus 39ms), so atriofascicular QRS should have a VH interval during maximal pre-excitation < 20ms

Articles on Mahaim Tachycardias

1. In atriofascicular pathways, an AP potential was found along the TA in only 52% of patients. Ablation at the ventricular insertion site often resulted in RBBB (57%), but the AP was also successfully ablated. (PACE 2006; 29:1226–1233)