ECG Limb Lead Algorithm Sensitive, Specific for Wide Complex Tachycardia Diagnosis

The limb lead algorithm (LLA) is a simple, accurate method that can be used to diagnose ventricular tachycardia approaching wide QRS complex tachycardia on an electrocardiogram (ECG), according to research published in Heart Rhythm.

Researchers sought to identify a simple, accurate, and rapid algorithm based on ECG limb lead patterns for aid in the diagnosis of ventricular tachycardia.

Data from 528 monomorphic wide QRS complex tachycardia readings with an established diagnosis of electrophysiology were included in the study. Investigators defined wide complex tachycardia as a regular rhythm with a monomorphic wide complex QRS (duration ≥0.12 sec) and a heart rate ≥100 bpm. Electrophysiology studies were performed between January 2015 and December 2018.

Each patient received a 12-lead ECG of the wide complex tachycardia at the same time as their electrophysiology procedure. All ECGs were independently analyzed by 2 electrophysiologists, each of whom were blinded to patient information, and requested to conduct 4 separate analyses according to the following algorithms: the 4-step Brugada algorithm, the aVR Vereckei algorithm, the R-wave peak time (RWPT) algorithm, and the LLA. The presence or absence of ventricular tachycardia was detected at each step in each of the 4 methods.

To create the LLA, investigators first developed an opposing QRS complex in limb leads algorithm, through the retrospective analysis of 130 readings of electrophysiology-proved wide complex tachycardia, using the different depolarization directions of ventricular tachycardia and supraventricular tachycardia with aberrant ventricular conduction on frontal plane as a foundation. Although the specificity of this algorithm was high, sensitivity was “relatively low.” To correct this, the algorithm was revised and additional criteria were added. Currently, the algorithm criteria cover “most [ventricular tachycardias] originating [from] the left ventricle,” according to the researchers.

The mean age of participants was 54.1±17.3 years. Results of the electrophysiology study indicated that 75.2% of wide complex tachycardia were ventricular in nature, and 24.8% had supraventricular tachycardia. For all 3 methods, excellent interobserver agreement was noted (k >0.8), with the LLA demonstrating superior results compared with the Brugada, Vereckei, and RWPT methods (k =0.98, 0.89, 0.9, and 0.83, respectively).

The LLA correctly identified 465 of 528 cases, with an overall test accuracy of 88.1% (95% CI, 85%-90.7%); this accuracy was similar to that for both Brugada and Vereckei (85.4% and 88.5%, respectively). LLA sensitivity was 87.2% (95% CI, 83.5%-90.3%), which was lower than that for both Brugada and Vereckei (94% and 92.4%) but higher than that for RWPT (67.8%). Significantly, the LLA demonstrated the highest specificity among all 4 methods (LLA [90.8%] vs Brugada [59.5%], Vereckei [76.3%], and RWPT [80.2%]).

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Compared with the other 3 algorithms, the positive predictive value of the LLA was best (96.7% vs 87.6%, 92.2%, and 91.2%, respectively). The negative predictive value of the LLA was significantly higher than that of the RWPT algorithm (70% vs 45.1%).

In the ROC curve analysis, the area under the curve for the LLA was superior to that of both the Brugada and RWPT algorithms (0.89 vs 0.77 and 0.74, respectively) but comparable with that for the Vereckei algorithm (0.84).

The primary limitation of the LLA is the algorithm’s inability to identify ventricular tachycardias originating from the conduction system in addition to the intracavitary structures. In addition, more cases and studies of the LLA may be needed in populations with abnormal baseline QRS.

“The LLA is a novel simple ECG algorithm to quickly diagnose [ventricular tachycardia] with good specificity and inter-observer agreement, thus complementing the diagnostic algorithms previously described in the literature,” the researchers concluded.

Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Chen Q, Xu J, Gianni C, et al. Simple electrocardiographic criteria for rapid identification of wide QRS complex tachycardia: the new limb lead algorithm [published online September 20, 2019]. Heart Rhythm. doi: 10.1016/j.hrthm.2019.09.021