Criteria in standard ECG to guide conduction system pacing implants

Conduction System Pacing (CSP) is gaining acceptance when high ventricular pacing burden is expected, and as an alternative to cardiac resynchronization. Current accepted criteria to ascertain CSP proper lead placement requires an EP system, not widely available. There are multiple ECG only criteria not currently validated for CSP implantation. We extracted all CSP attempted implants. Various accepted criteria for CSP capture were evaluated for each patient, along with other ECG only criteria: T wave polarity in lateral leads (V5-V6); T wave polarity in D1, terminal S wave in lateral leads; terminal S wave in D1; and an initial r wave in V1. A cohort of 482 consecutive patients was evaluated, where 36% were women. Mean age was 77.3 y.o. (± 8.9 years; range 22-98 y.o.). Implant indications included: sick sinus (26.3%), AV block (34.9%), abnormal conduction induced cardiomyopathy (26.1%), AV node ablation (9.1%) and LBBB only (0.8%). Medtronic 3830 leads were mostly implanted. A His pacing was targeted in 5.2% of patients, and 51.4% had pre-implant narrow QRS. Leads were directed anteriorly, posteriorly and mid-septal in 28.3%, 18.6%, and 53.1% of cases, respectively (based on inferior lead polarities). A QRS (from the pacing spike) of 140ms or less was achieved in 60.0% of implants, a LVAT lesser than 75ms in 47.7% (lesser than 85ms in 78.1% of patients and impossible to evaluate in 6.0% of patients (due to Q-S in V6)). A V6-V1 interpeak interval greater than 33ms was achieved in 54.0% of patients (the criterion was impossible to measure in 36.3% of patients). When comparing possible ECG parameters which may guide CSP implants, V5-V6 normal T wave repolarization and terminal S waves in V5-V6 where found to be most helpful and provides another tool to ascertain CSP capture when r’/R’ are not seen (mostly in anterior oriented positions) or V6-V1 inter-peak is impossible to measure (lack of either positive V5-V6 or visible r’/R’ in V1).