Current of Injury Is an Indicator of Lead Depth and Performance During Left Bundle Branch Pacing Lead Implantation

Authors, Journal, Affiliations, Type, DOI

• Authors: Shalaimaiti Shali and Weiyun Wu (joint first authors); Jin Bai; Wei Wang; Shengmei Qin; Jingfeng Wang; Yixiu Liang; Haiyan Chen; Yangang Su; Xueying Chen (corresponding); Junbo Ge
• Journal: Heart Rhythm 2022;19(8):1281–1288. © 2022 Heart Rhythm Society
• Affiliations: Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, National Clinical Research Center for Interventional Medicine; Department of Laboratory Medicine, Zhongshan Hospital; Department of Cardiac Echocardiography, Zhongshan Hospital
• Type: Prospective single-centre observational study — 212 consecutive patients, 513 LBBP lead-fixation attempts (mean 2.38 ± 0.64 per patient), 6-month follow-up
• DOI: 10.1016/j.hrthm.2022.04.027
• Funding: Shanghai Hospital Development Center (SHDC2020CR4003); National Natural Science Foundation of China (82170387); Shanghai Clinical Research Center for Interventional Medicine (19MC1910300). Disclosures: none declared

Overview

When the LBBP lead is screwed into the septum, the trauma produces a current of injury (COI) on the unipolar intracardiac electrogram — ST-segment elevation relative to the intrinsic R wave. This study asks whether that signal can answer the two questions the operator actually faces: is the lead deep enough for a good threshold, and has it perforated? In 212 patients and 513 fixation attempts, a distinct COI on the tip electrode (≥25% of the intrinsic R amplitude) was present in 92.6% of attempts. Its presence predicted that an initially poor threshold would improve within 10–20 minutes — 33/47 with initial COI improved versus 0/8 without — and its absence identified every perforation: the 38 attempts without tip COI included all 11 septal perforations (3 evident, 8 microperforations), giving sensitivity 100%, specificity 94.6%, NPV 100%. The tip-to-ring COI ratio added a quantitative depth measure: it correlated negatively with angiographic lead depth (r = −0.624) and fell to 0.07 ± 0.04 in microperforation, so a ratio <1 flagged microperforation with sensitivity 100% and a 100% negative predictive value. The practical message: wait rather than reposition when COI is present; stop rotating when it disappears.

Keywords

Lead perforation; Left bundle branch pacing; Current of injury; Capture threshold; Intracardiac electrogram

Key Takeaways

Definitions and methods

• COI: ST-segment elevation ≥25% of the intrinsic R-wave amplitude on the unipolar intracardiac EGM (band-pass 0.05–1000 Hz), measured from both tip and ring electrodes after each lead rotation, by two observers blinded to the protocol
• Acceptable LBB capture threshold: <1.5 V/0.5 ms
• Evident perforation: loss of capture at 10 V/0.5 ms unipolar from both tip and ring, with abrupt electrode movement on fluoroscopy
• Microperforation: loss of capture on the tip at 3.0 V/0.5 ms initially and at 10 minutes, while the ring still captures myocardium with an RBBB-paced QRS
• Confirmation: contrast injection from the sheath into the LV cavity
• Capture confirmation (separate from COI): RBBB-paced morphology plus either selective LBBP with a discrete EGM component or Sti-LVAT shortening >10 ms with increasing output / shortest and constant at the final site
• Recording: 12-lead ECG plus intracardiac EGM on a GE CardioLab 2000 at 100 mm/s; pacing parameters on a Medtronic 2290 analyser

Cohort

• 212 patients, age 66.25 ± 15.20; male 60.66%
• Indications: AV block 63.93%, SSS 19.67%, AF with low ventricular rate 1.64%, HFrEF 14.75%
• Echocardiography: LVEDD 50.48 ± 7.42 mm, IVS 9.92 ± 1.23 mm, LVEF 57.63 ± 12.41%
• Intrinsic QRS 125.32 ± 36.30 ms; normal 57.38%, RBBB 21.31%, LBBB 13.11%, IVCD 8.20%
• 513 attempts, 2.38 ± 0.64 per patient; mean lead depth 12.96 ± 2.07 mm
• Septal perforation: 11/513 (2.14%) — 3 evident, 8 microperforations
• PoLBB 182 (85.85%); SLBBP 125 (58.96%); paced QRS 129.15 ± 21.53 ms (S) and 121.79 ± 20.75 ms (NS); PoLBB–V 25.86 ± 6.13 ms; Sti-LVAT 72.28 ± 13.72 ms; threshold 0.81 ± 0.48 V; sensing 6.43 ± 2.25 mV; impedance 699.42 ± 174.52 Ω

COI and the capture threshold

• COI on the tip was present in 475/513 attempts (92.60%), amplitude 10.64 ± 6.36 mV; on the ring in 349/513 (68.0%), 5.78 ± 4.96 mV
• Better thresholds had larger COI: leads with capture <1 V (n=405) had 12.33 ± 6.14 mV versus 4.04 ± 3.35 mV in those with ≥1.5 V (n=58) at first measurement (P < .001)
• An unacceptably high initial threshold occurred in 9.89% of attempts with COI (47/475) versus 28.85% without (11/38) (P < .001) — and every one of the 38 without COI was a perforation (3 evident, 8 micro)
• The management rule: after 10 minutes, the threshold improved in 33/47 (70.2%) with initial COI versus 0/8 without (P < .0001). The 8 without COI all had a threshold ≥3.0 V/0.5 ms at 10 minutes and were confirmed microperforations
• Absence of initial tip COI as a perforation marker: SN 100%, SP 94.62%, PPV 28.95%, NPV 100% — note the low PPV: most leads without COI were not perforated, so absence is a rule-out signal, not a diagnosis
• Residual COI after 10 minutes (repeat measurements, n=47): COI fell from 9.05 ± 5.24 to 4.78 ± 3.35 mV in 33 cases (P = .000); 14 had no residual COI
  • Improvement was likelier with residual COI: 29/33 vs 4/14 (P < .0001)
  • Among the 14 still ≥1.5 V at 10 minutes, none of the 10 without residual COI improved at a further 10 minutes (all repositioned); of the 4 with residual COI, 2 improved after another 10 minutes, 1 after deeper advancement, 1 was repositioned
  • Absence of residual COI for a persistently high threshold: SN 90.91%, SP 88.89%, PPV 71.43%, NPV 96.97%

COI ratio, lead depth, and microperforation

• The tip/ring COI ratio averaged 4.86 ± 4.04 (range 0.03–10.88) and correlated negatively with angiographic lead depth (r = −0.624, P < .0001)
• Ratio <1: depth 13.86 ± 1.07 mm versus 11.24 ± 1.95 mm for ratio ≥1 (P = .001)
• In microperforation the ratio was 0.07 ± 0.04 (range 0.03–0.13)
• Ratio <1 for microperforation: SN 100%, SP 98.22%, PPV 57.14%, NPV 100%
  • ⚠ The abstract reports specificity 96.6% for this rule; the Results section reports 98.22%. The two figures are not reconciled
• The 11 perforations in detail: in the 3 evident perforations, COI was absent on both electrodes; in the 8 microperforations, only the tip COI was absent, while ring COI remained similar to non-perforated leads (P = .157). Perforated leads had impedance 420–660 Ω
• The signal is dynamic: as the helix was pulled back, COI reappeared on the tip, confirming that loss of tip COI tracks the electrode position rather than irreversible tissue damage

The proposed decision algorithm

• When the initial threshold is ≥1.5 V but <10 V:
  • COI present → wait 10 minutes rather than reposition; if still high, wait another 10 minutes or advance the lead more deeply before relocating
  • COI absent → reposition — microperforation is likely and the threshold will not improve
• While screwing: monitor tip and ring COI continuously; stop when tip COI drops abruptly or when tip/ring falls below 1, because further advancement toward a lower threshold or larger potential then risks microperforation
• COI is not a capture criterion. PoLBB, SLBBP, paced QRSd, PoLBB–V and Sti-LVAT did not differ by COI status; capture still has to be confirmed by the usual criteria

Limitations of the document

Authors' own stated limitations

• All implants were performed by the centre's most experienced physician, who had done >500 LBBP cases — the conclusions may not transfer to less experienced operators
• No commercially available application reports the tip/ring COI ratio in real time, limiting adoption
• Single-centre observational study with only 6 months of follow-up — chronic lead failure was not detected, so the predictive value for long-term performance is unknown
• The cohort had HFrEF in 14.75% and abnormal QRS in 42.62%, so the results should be interpreted carefully

Additional limitations evident in the study

• It is an unblinded, single-operator management study. The COI was read and acted on by the same team, and the "wait versus reposition" algorithm was applied with knowledge of the COI values — so the comparison of outcomes is confounded by the decision rule itself
• ⚠ The abstract and results disagree on the ratio rule's specificity (96.6% vs 98.22%), and neither is accompanied by a confidence interval. The discrepancy suggests the rule was refined after analysis, and the reported performance is in-sample
• The positive predictive values are low for the absence-based rules — 28.95% for absent tip COI and 57.14% for ratio <1 — so these are rule-out tests, and the paper's framing ("could indicate perforation") understates how many COI-negative leads were simply shallow or poorly engaged rather than perforated
• Microperforation is defined electrically, not anatomically. "Loss of tip capture with preserved ring capture" can also occur with a lead that has simply advanced past the myocardium or lies in a different tissue plane; only the contrast injection confirms the LV cavity, and the paper does not state how many of the 8 microperforations were contrast-confirmed
• The sample size was powered for a 2 mV COI difference, not for perforation prediction. With 11 events, the 100% sensitivity and NPV have very wide confidence intervals and no external validation
• The ratio threshold of 1 was derived and tested in the same 513 attempts, and the measurement is offline and observer-dependent; no reproducibility data are given for the tip/ring measurement
• COI was measured after each rotation, not continuously, despite the discussion recommending real-time monitoring — so the paper's central proposal (continuous COI surveillance) is not the method it evaluated
• The 2.14% perforation rate is high relative to several series and comes from a single high-volume operator; whether the COI strategy reduces perforation relative to standard practice is not tested (there is no control arm)
• The cohort is mostly AV block with preserved LVEF; the algorithm is untested in CRT/LBBB populations, where deeper septal placement and larger leads may alter COI behaviour
• The unusually high PoLBB rate (85.85%) and SLBBP rate (58.96%) exceed most published series and suggest either a very experienced operator or a liberal recording definition; either way, the cohort may not represent routine practice
• No chronic threshold or lead-failure data, so the claim that COI predicts "performance" is limited to the acute and 6-month window
• Rating rationale: rated medium. It is a large prospective series (212 patients, 513 attempts) with a clinically useful, mechanistically grounded signal and a clear decision algorithm, and its rule-out performance for perforation is strong. It is not high because it is single-centre, single-operator, unblinded and uncontrolled, the predictive rules were derived and tested in the same cohort, the PPVs are low, the abstract and results disagree on a key specificity, and no external validation or real-time implementation exists

Key Concepts Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — the technique; this paper supplies its COI safety rules
• concepts/Conduction-System-Pacing — the umbrella category
• Current of injury (COI) — ST elevation ≥25% of the intrinsic R wave on the unipolar EGM, reflecting tissue trauma at the electrode
• Tip COI vs ring COI — tip reflects the helix's contact; ring reflects the more proximal electrode
• COItip/COIring ratio — a depth index; falls as the lead advances, <1 suggests microperforation
• Evident vs microperforation — loss of capture from both electrodes versus tip-only loss with preserved ring capture
• Capture threshold recovery — the decline from ≥1.5 V to <1.5 V over 10–20 minutes, predicted by residual COI
• Sti-LVAT and PoLBB — the capture criteria used independently of COI
• Injury-current persistence — the general principle from conventional active-fixation leads that COI predicts acute stability

Key Entities Mentioned

• concepts/Left-Bundle-Branch-Area-Pacing — primary concept page
• Zhongshan Hospital, Fudan University, Shanghai — the investigating centre
• Shalaimaiti Shali; Xueying Chen; Junbo Ge; Yangang Su — the investigators
• GE CardioLab 2000 — the EP recording system
• Medtronic 2290 — the pacing system analyser
• Saxonhouse; Redfearn; Shali — the prior work establishing COI as a predictor of active-fixation lead performance
• Heart Rhythm Society / Elsevier — publisher

Wiki Pages Updated

• Created: wiki/sources/coi-lead-depth-hrs-2022.md
• Updated: wiki/concepts/Left-Bundle-Branch-Area-Pacing.md
• Updated: wiki/concepts/Conduction-System-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md