STd during SVT is observed at long VA intervals when the retrograde P wave matches the ST segment, without dependence on the TCL. This suggests that STd is not necessarily rate dependent but a result of a fusion between the ST segment and the P wave.
Introduction Radiofrequency (RF) is the preferred thermal energy used in
electrophysiology. RF catheter must deliver the energy close to
arrhythmia foci. A new method to deliver RF to deeper locations using a
pacemaker lead is explored. Methods A Medtronic 3830 lead screwed in
chicken breasts delivered 50 watts RF energy in three methods: A) direct
fashion (RF catheter touching the proximal end of the 3830 lead, acting
as an extension of RF catheter), or B) 3830 lead as a return patch (RF
delivered in the bath without contact), or C) 3830 lead as a return
patch (RF delivered touching the breast surface close to the 3830 lead
screwed deep in the flesh). Different power settings were also tested.
Lesion surface area is reported in cm2. Results 76 measurements were
available. Bigger lesions were obtained at 10W method A (0.78cm2), 50W
method C (0.72cm2) and 5W method B (0.44cm2). High impedances were noted
at 10W and 50W with tissue remaining attached to the lead when removed.
Conclusion RF can be delivered to deeper foci through a 3830-pacemaker
lead with maximum size lesion formation using proximal unipolar direct
delivery and proximal close bipolar as the return patch. In humans, it
opens a path to attain deep septal foci (LV summit) or epicardial
structures (vein of Marshall, transmural ablation from RF endocardial to
LV coronary sinus lead as return patch): using standard, 4F pacemaker
leads, and 2F small EP catheters or even isolated guidewires.
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