Conceptual and Literature Basis for Wide Complex Tachycardia and Baseline ECG Comparison

Authors, Journal, Affiliations, Type, DOI

• Evenson CM, Kashou AH, LoCoco S, DeSimone CV, Deshmukh AJ, Cuculich PS, Noseworthy PA, May AM
• Journal of Electrocardiology, 2021;65:50–54
• Department of Medicine/Cardiovascular Diseases, Washington University School of Medicine, St. Louis, MO; Mayo Clinic, Rochester, MN
• Short review / correspondence
• DOI: 10.1016/j.jelectrocard.2021.01.007
• No conflicts of interest declared

Overview

A focused 2021 correspondence from the May/Kashou/DeSimone group articulating the theoretical and historical basis for comparing the WCT ECG to the patient's baseline ECG as a differentiation strategy. SWCT is constrained to His-Purkinje-mediated ventricular activation patterns, producing a limited variety of QRS/T-wave morphologies that often resemble the baseline ECG; VT has "electrical freedom" and routinely produces markedly different depolarisation and repolarisation patterns. The paper reviews the historical literature (Sandler 1965 → Dongas 1985 → Griffith 1991 → Pachón 2019) and introduces the WCT Formula II as the third automated baseline-comparison method.

Keywords

ECG, electrocardiogram, supraventricular tachycardia, wide complex tachycardia, ventricular tachycardia

Key Takeaways

Conceptual Framework: Electrical Constraint vs Electrical Freedom

• SWCT: Ventricular activation constrained by the His-Purkinje network → limited variety of QRS/T-wave patterns; functional aberrancy (new BBB) changes QRS configuration vs baseline but remains within His-Purkinje-permitted patterns; exception: SWCT with preexisting aberrancy often produces near-identical QRS morphology to the baseline ECG
• VT: Originates from any ventricular region; wavefront propagation multidimensional and unconstrained → routinely produces QRS/T-wave patterns markedly different from baseline; exceptions: fascicular VT and bundle branch re-entry — the only VT varieties that may closely resemble the baseline ECG

Historical Literature Basis for Baseline ECG Comparison

• Sandler & Marriott (1965): Compared initial QRS activation vector of wide complex beats (RBBB morphology) to baseline — 44% of SVT aberrant beats shared the same initial vector as baseline vs only 4% of PVCs; conclusion: identical initial vector to baseline sinus rhythm implies unchanged ventricular septal activation → aberrancy
• Dongas et al. (1985): WCTs with unchanged QRS morphology at V1/II/III vs preexisting BBB in sinus → almost invariably SWCT; different QRS morphology → usually VT; SWCT QRS axis ≈ baseline axis; VT QRS axis significantly different from baseline; more extensive QRS duration changes in VT
• Griffith et al. (1991): QRS axis change ≥40° from baseline was the third strongest independent VT predictor (after MI history and aVF QRS configuration); 83% of VT patients had ≥40° axis shift vs only 36% of SWCT patients

Pachón et al. (2019) — Baseline-Comparison Criteria

Four of the seven Pachón algorithm criteria explicitly capitalise on WCT–baseline ECG comparison:

1. Sudden QRS normalisation in patients with baseline AF — 11% sensitive, 100% specific for VT
2. QRS duration narrower during WCT than baseline rhythm — 10% sensitive, 99% specific for VT
3. Discordant BBB pattern in patients with baseline BBB — 15% sensitive, 99% specific for VT
4. WCT QRS morphology identical to baseline ECG — 37% sensitive, 99% specific for SWCT

All four criteria are individually low sensitivity but near-perfect specificity — useful as rule-in criteria when present.

Automated Methods: Performance Data

Three automated methods from the same group, all using logistic regression on computerised ECG measurements between paired WCT and baseline ECGs:

• VT demonstrates far greater frontal PTVAC than SWCT: 226.5% vs 53.6% (p<0.001) — WCT Formula II derivation data
• VT demonstrates greater T-wave axis change than SWCT: 92° vs 41° (p<0.001) — VT Prediction Model derivation data
• All three require a paired baseline ECG (recorded before or after the WCT event); not applicable when no prior ECG is available

Limitations of the Document

• Short correspondence (5 pages), no new primary data — a conceptual and literature review only
• All three automated methods reviewed are by the same author group (May, Kashou, DeSimone, Deshmukh); no independent replication reported
• No head-to-head comparison with traditional manual algorithms reported
• Performance figures are from derivation datasets only; external validation not reviewed in this paper
• Extremely narrow scope (baseline comparison only); does not address most WCT differentiation scenarios

Key Concepts Mentioned

• concepts/wide-complex-tachycardia — primary subject; baseline comparison framework, Pachón criteria details, WCT Formula II
• concepts/Fascicular-Ventricular-Tachycardia — exception: closely resembles baseline ECG (limits all algorithms including baseline comparison)

Key Entities Mentioned

• None specific

Wiki Pages Updated

• wiki/sources/wct-baseline-jecg-2021.md — created
• wiki/concepts/wide-complex-tachycardia.md — added: SWCT electrical constraint vs VT electrical freedom conceptual framework; Pachón 4 baseline-comparison criteria with specificity data; WCT Formula II (AUC 0.96); AUC data for all three automated methods; Sandler/Dongas/Griffith baseline-comparison data
• wiki/sourceindex.md — updated
• wiki/wikiindex.md — updated