The data are first to show that systemic inflammation via elevated IL-6 levels may represent a novel QT-prolonging risk factor contributing to TdP occurrence in the presence of other classical risk factors. If confirmed, this could open new avenues in antiarrhythmic therapy.

Background— In patients with autoimmune disease, anti-Ro/SSA antibodies (anti-Ro/SSA) are responsible for a novel autoimmune-associated long-QT syndrome by targeting the hERG potassium channel and inhibiting the related current ( I Kr ). Because anti-Ro/SSA are also present in a significant proportion of healthy subjects and may be associated with torsades de pointes (TdP) arrhythmia, we tested the hypothesis that anti-Ro/SSA may represent a silent risk factor in patients developing TdP. Methods and Results— Twenty-five consecutive patients who experienced TdP were prospectively collected independent of ongoing therapies and concomitant diseases. Anti-Ro/SSA were detected by fluoroenzyme immunoassay, immuno–Western blotting, and line-blot immunoassay. Purified IgGs from anti-Ro/SSA-positive and anti-Ro/SSA-negative patients were tested on I Kr using HEK293 cells stably expressing the hERG channel. As expected, in TdP patients, many known corrected QT interval–prolonging risk factors were simultaneously present, including hypokalemia that was the most common (52%). Anti-Ro/SSA were present in 60% of the subjects, mostly the anti-Ro/SSA-52-kD subtype detected by immuno–Western blotting only. A history of autoimmune disease was found in only 2 of anti-Ro/SSA-positive patients. Experimental data demonstrated that purified anti-Ro/SSA-positive IgGs significantly inhibited I Kr and cross reacted with hERG-channel proteins. Moreover, anti-Ro/SSA-positive sera exhibited high reactivity with a peptide corresponding to the hERG-channel pore-forming region. Conclusions— Anti-Ro/SSA may represent a clinically silent novel risk factor for TdP development via an autoimmune-mediated electrophysiological interference with the hERG channel. We propose that TdP patients may benefit from specific anti-Ro/SSA testing even in the absence of autoimmune diseases as immunomodulating therapies may be effective in shortening corrected QT interval and reducing TdP recurrence risk.

Objective. Recent evidence suggests that anti-Ro/SSA antibodies, strongly associated with the development of congenital heart block, may also be arrhythmogenic for the adult heart. In fact, anti-Ro/SSA-positive patients with connective tissue disease (CTD) frequently display corrected QT (QTc) prolongation associated with an increase in ventricular arrhythmias. However, QTc prolongation prevalence markedly differs throughout the studies (10 -60%), but the reason why is not yet clear. The aim of this study was to evaluate whether anti-Ro/SSA-associated QTc prolongation in adult patients with CTD is related to antibody level and specificity. Methods. Forty-nine adult patients with CTD underwent a resting 12-lead electrocardiogram recording to measure QTc interval, and a venous withdrawal to determine anti-Ro/SSA antibody level and specificity (anti-Ro/SSA 52 kd and anti-Ro/SSA 60 kd) by immunoenzymatic methods and Western blotting. Results. In our population, a direct correlation was demonstrated between anti-Ro/SSA 52-kd level and QTc duration (r ‫؍‬ 0.38, P ‫؍‬ 0.007), patients with a prolonged QTc had higher levels of anti-Ro/SSA 52 kd with respect to those with a normal QTc (P ‫؍‬ 0.003), and patients with a moderate to high level (>50 units/ml) of anti-Ro/SSA 52 kd showed a longer QTc interval (P ‫؍‬ 0.008) and a higher QTc prolongation prevalence (P ‫؍‬ 0.008) than those with a low positive/negative level (<50 units/ml). On the contrary, no association was found between QTc and anti-Ro/SSA 60-kd level. Conclusion. In anti-Ro/SSA-positive adult patients with CTD, the occurrence of QTc prolongation seems strictly dependent on the anti-Ro/SSA 52-kd level. This finding, possibly explaining the different QTc prolongation prevalence reported, strengthens the hypothesis that an extremely specific autoimmune cross-reaction is responsible for the antiRo/SSA-dependent interference on ventricular repolarization.