Simplified Integrated Clinical and Electrocardiographic Algorithm for Differentiation of Wide QRS Complex Tachycardia — The Basel Algorithm

Authors, Journal, Affiliations, Type, DOI

• Authors: Federico Moccetti, Mrinal Yadava, Yllka Latifi, Ivo Strebel, Nikola Pavlovic, Sven Knecht, Babken Asatryan, Beat Schaer, Michael Kühne, Charles A. Henrikson, Frank-Peter Stephan, Stefan Osswald, Christian Sticherling, Tobias Reichlin
• Journal: JACC: Clinical Electrophysiology, Vol. 8, No. 7, July 2022, pp. 831–839
• Affiliations: Division of Cardiology, University Hospital Basel, Basel, Switzerland; Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon, USA; Inselspital Bern University Hospital, Bern, Switzerland
• Type: Original research — derivation and validation cohort study
• DOI: https://doi.org/10.1016/j.jacep.2022.03.017

Overview

Wide QRS complex tachycardia (WCT) represents a diagnostically challenging emergency, as ~80% of cases are ventricular tachycardia (VT) while the remainder are SVT with aberrant conduction or other causes. Existing algorithms (Brugada 1991, Vereckei 2008) have high reported sensitivity/specificity in original cohorts but demonstrate poor real-world reproducibility due to their complexity. Moccetti et al. derived and externally validated a 3-criterion algorithm combining one clinical parameter and two ECG measurements. In a head-to-head clinical applicability test against 5 existing algorithms performed by 8 physicians across training levels, the Basel algorithm achieved superior or equivalent diagnostic accuracy in significantly shorter time.

Keywords

ECG, cardiac arrhythmia, wide QRS complex tachycardia, ventricular tachycardia, supraventricular tachycardia, sudden cardiac death, algorithm

Key Takeaways

Study Design and Patient Population

• Derivation cohort: 206 WCT episodes (153 VT, 53 SVT) from 124 patients at University Hospital Basel, Switzerland (2010–2014); all EP-confirmed diagnoses.
• Validation cohort: 203 WCT episodes (151 VT, 52 SVT) from 112 patients at Knight Cardiovascular Institute, OHSU, Portland, Oregon.
• WCT is VT in ~80% of cases; misdiagnosis (e.g., treating VT as SVT with adenosine or verapamil) carries potentially lethal consequences.

Derivation of the Basel Algorithm

• From multiple ECG candidate criteria tested in the derivation cohort, lead II time to first peak and lead aVR time to first peak had the best performance (AUC 0.91 each). ROC-derived optimal cutoffs were 51 ms (lead II) and 46 ms (lead aVR); a 40 ms cutoff was chosen to facilitate user-friendly clinical application.
• Three criteria of the Basel Algorithm:
  1. Clinical high-risk feature — prior myocardial infarction, OR congestive heart failure with LVEF ≤35%, OR implanted ICD or CRT-D
  2. Lead II time to first peak >40 ms — positive if time from QRS onset to first peak (positive or negative deflection) exceeds 40 ms
  3. Lead aVR time to first peak >40 ms — same measurement applied to aVR
• Diagnosis: VT if ≥2 of 3 criteria are met; SVT if 0 or 1 criterion is met.
• Observer agreement was excellent: r² = 0.94 (lead II) and r² = 0.92 (lead aVR); Bland-Altman bias ≤0.8 ms.

Physiological Rationale

• In SVT with bundle branch block: impulse enters via the His-Purkinje system → rapid initial ventricular activation → steep initial QRS → narrow first peak in both leads.
• In VT: initial activation is muscle-to-muscle → slow initial spread → broad, delayed first peak (>40 ms); conduction system mediates only the terminal portion → steeper terminal QRS.
• This is the same theory underlying the Vereckei aVR step (RWPT >40 ms) and the Pava RWPT algorithm (>50 ms in lead II); the Basel algorithm integrates both into a 2-ECG-lead measurement framework.

Performance in Derivation and Validation Cohorts

• Basel algorithm: SN 91.5%, SP 88.7% (derivation); SN 93.3%, SP 90.4% (validation) — comparable to Brugada and Vereckei algorithms (see Supplemental Table 3 in original article).
• No statistically significant difference in SN, SP, or overall accuracy vs Brugada or Vereckei in either cohort.

Clinical Applicability (Head-to-Head vs 5 Algorithms, 8 Physicians)

• 8 physicians (2 EPs, 2 general cardiologists, 2 cardiology fellows, 2 internal medicine residents) analyzed 50 WCT ECGs (25 VT, 25 SVT) at 6 time points using Brugada, Vereckei, Pava, Jastrzebski, Chen, and Basel algorithms.
• Diagnostic accuracy: Basel 81% (IQR 76.5–83.5%) vs Vereckei 72% (IQR 65–76%; P=0.002) and Chen 72% (IQR 58–73%; P=0.03); no significant difference vs Brugada.
• Specificity: Basel 80% vs Vereckei 58% (P=0.007).
• Time to diagnosis: Basel 38 sec (IQR 29–47) vs Brugada 106 sec (IQR 76–135; P=0.002) vs Vereckei 48 sec (IQR 43–59; P=0.02). Benefit most pronounced in fellows and internal medicine residents.

Clinical Implications

• Suitable for emergency settings due to reliance on only limb leads II and aVR (no precordial morphology assessment required).
• Potentially compatible with Holter and telemetry software that includes only limb leads.
• Low complexity makes it particularly valuable for physicians in training and non-EP practitioners.

Special Situations — Poor Performance

• All three compared algorithms (Brugada, Vereckei, Basel) performed poorly in:
  • Fascicular VT (n=3)
  • Antidromic AV re-entrant tachycardia (n=1)
  • Mahaim fiber tachycardia (n=3)
• These rare preexcitation and fascicular entities represent important exceptions requiring additional clinical context.

Limitations of the Document

• Derivation and validation cohorts were both from tertiary EP centres — referral bias cannot be excluded; prevalence of VT (74–75%) may exceed community-based settings.
• Only EP-confirmed diagnoses included — selection bias since not all WCT patients undergo EP study.
• Relatively low number of preexcitation-related tachycardias in both cohorts; algorithm needs further evaluation in this subgroup.
• Some patients contributed multiple ECGs (different VT morphologies counted separately).
• No prospective validation in diverse community/emergency medicine settings.
• No automated application tested; potential for software integration noted as future direction.

Key Concepts Mentioned

• concepts/Wide-Complex-Tachycardia — primary focus; Basel Algorithm development and validation
• concepts/ECG-Conduction-Disturbances — LBBB/RBBB pattern relevance in WCT differential
• concepts/Cardiac-Action-Potential — physiological basis of slow initial vs rapid terminal QRS activation in VT vs SVT with BBB

Key Entities Mentioned

• entities/Brugada-Syndrome — Brugada algorithm (1991) for WCT differential, not Brugada syndrome per se; frequently referenced as standard of care comparator

Wiki Pages Updated

• Created: wiki/sources/svt-vt-basel-jaccep-2022.md
• Created: wiki/concepts/Wide-Complex-Tachycardia.md
• Updated: wiki/wikiindex.md
• Updated: wiki/sourceindex.md
• Updated: log.md