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The risks for ventricular fibrillation (VF) or sudden cardiac arrest (SCA) were found to be associated with low T/R ratios at leads II and V5 in patients with spontaneous type-1 Brugada pattern (SBT1), according to a retrospective study published in the Journal of Electrocardiology.
Adults (N=115; 91.3% men) with SBT1 were recruited at 9 centers in France, 2 in Romania, and 2 in Switzerland to participate in this study. SBT1 was defined as ST-segment elevation ³2 mm in V1 and/or V2 with negative T waves in the absence of class I antiarrhythmic drugs. Patients underwent an electrophysiology study and their electrocardiogram data was digitized for analysis.
Of 115 participants, 45 (100% men; mean age, 38.7±11.5 years) had VF/SCA. Participants with vs without (n=70; mean age, 49.3±12.0 years) VF/SCA had significantly different rates of: syncope (76.5% vs 24.2%, respectively; P <.001), heart rate (80.0 vs 70.3 beats per minute, respectively; P <.001), median QRS in lead V2 (122.0 vs 108.0, respectively; P =.001), mean wide QRS in lead V2 (30% vs 22%, respectively; P =.002), Bazett QTc in lead II (413.0 vs 389.5, respectively; P <.001), Fredericia QTc in lead II (393.0 vs 381.0, respectively; P =.004), maximum Tpeak-Tend interval (98.6 vs 85.5, respectively; P <.001), early repolarization (20% vs 45%, respectively; P <.001), and BT1 in peripheral leads (12% vs 1%, respectively; P =.004).
Patients with vs without VF/SCA had: higher median R wave amplitudes in lead V5 (1.43 vs 1.13 mV, respectively; P =.03), lower T/R ratios in lead V5 (0.25 vs 0.34, respectively; P =.008), lower T/R ratios in lead II (0.41 vs 0.51; P =.04, respectively), and lower T/R ratios among leads II and V5 (0.24 vs 0.43, respectively; P =.006).
The lowest T/R ratio was observed at leads II and V5 (£0.17) in 44.4% and 11.4% of patients with and without VF/SCA, respectively (P <.001). This value corresponded to the best cutoff for patient stratification (area under the curve, 0.65; specificity, 88.6%; sensitivity, 44.4%; positive predictive value, 71.4%; negative predictive value, 71.3%).
Independent predictors of VF/SCA were: minimum T/R ratio £0.17 (odds ratio [OR], 6.10; 95% CI, 1.92-19.40; P =.002), early repolarization (OR, 3.60; 95% CI, 1.22-10.64; P =.02), and BT1 pattern in a peripheral lead (OR, 10.78; 95% CI, 1.21-96.13; P =.03).
A major limitation of this study was the fact that all assessments and correlations with overall disease state were determined from a single electrocardiograph.
The study authors concluded that low T/R ratio among leads II and V5 was an independent predictor of VF and/or SCA among patients with SBT1 pattern and may be a valuable tool for risk stratification, especially when combined with an early repolarization phenotype.
Reference
Delinière A, Baranchuk A, Bessière F, et al. Prognostic significance of a low T/R ratio in Brugada syndrome. J Electrocardiol. 2020;63:6-11. doi:10.1016/j.jelectrocard.2020.08.023
