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Background:
Right ventricular (RV) septal pacing (RVS) may offset the detrimental effect on left ventricular function with chronic RV apical (RVA) pacing. During pacemaker implantation lead placement involves standard fluoroscopic views in both antero-posterior (AP) and left anterior oblique (LAO 300) position sometimes in combination with a paced 12-lead surface ECG. We compared the post-procedure final lead position determined by high-resolution contrast cardiac CT with the position indicated by the surface ECG.
Methods:
18 patients with dual chamber pacemakers (10 RVS and 8 RVA), placed fluoroscopically using AP and LAO 300 views at implant, subsequently underwent contrast enhanced ECG-gated modified, multi-detector CT coronary angiography (CTCA) and a 12 lead ECG with forced ventricular pacing at 90 pulses per minute. All implants were performed by experienced operators. True septal lead position was defined if the pacing lead tip pointing toward the left anterior descending artery (LAD) assisted by late contrast enhancement of the RV endocardium.
Results:
Of leads positioned in the RVS at implant, CT revealed 7 were on the anterior RV wall, 2 were at the anteroseptal junction, and only 1 at the septum. The ECG demonstrated a QRS axis of -900, absent R wave in V1 and a positive R wave in V6 in all cases. For the 8 RVA leads, 4 were anterior, 2 septal and 2 anteroseptal. The ECG axis varied between -90 and +1100, with an absent R wave in V1 in all cases but a positive R wave in V6 in 4.
Conclusion:
although the surface ECG differentiates septal from apical leads, it is of insufficient accuracy to determine subtle changes in the final lead tip position. The majority of leads were not truly septal as judged by CT imaging. This has implications for pacing studies using septal lead position as a comparator.
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