Prevalence and Clinical Characteristics of Patients with Torsades de Pointes Complicating Acquired Atrioventricular Block

Background: Female gender, degree of QT prolongation, and genetic susceptibility are known risk factors for developing torsades de pointes (TdP) during high-grade atrioventricular block (HG-AVB). Our objective was to analyze the prevalence and clinical characteristics of patients presenting with TdP and AVB (TdP [+]) in comparison with non-TdP patients with AVB (TdP [-]). Methods: All the ECGs from patients prospectively admitted for AVB (2 to 1, HG, and complete) at the University Hospital of Nice were analyzed. Automated corrected QT (QTc), manual measurements of QT and JT intervals, and Tpeak-to-end were performed at the time of the most severe bradycardia. Results: From September 2020 to November 2021, 100 patients were admitted for HG-AVB. Among them, 17 patients with TdP were identified (8 men; 81 +/- 10 years). No differences could be identified concerning automated QTc, manual QTc (Bazett correction), baseline QRS width, or mean left ventricular ejection fraction between the two groups. Potassium serum level on admission and mean number of QT-prolonging drugs per patient were not significantly different between the two groups, respectively: 4.34 +/- 0.5 mmol/L in TdP [+] versus 4.52 +/- 0.6 mmol/L (p = 0.33); and 0.6 +/- 0.7 in TdP [+] versus 0.3 +/- 0.5 (p = 0.15). In contrast, manual QTc(FR) (Fridericia correction), JT (Fridericia correction), Tpeak-to-end, and Tpe/QT ratio were significantly increased in the TdP [+] group, respectively: 486 +/- 70 ms versus 456 +/- 53 ms (p = 0.04); 433 +/- 98 ms versus 381 +/- 80 ms (p = 0.02); 153 +/- 57 ms versus 110 +/- 40 ms (p < 0.001); and 0.27 +/- 0.08 versus 0.22 +/- 0.06 (p < 0.001). Conclusions: The incidence of TdP complicating acquired AVB was 17%. Longer QTc(FR), JT, and Tpeak-to-end were significantly increased in the case of TdP but also in the presence of permanent AVB during the hospitalization.