Allergy to pacemaker silicone compounds: recognition and surgical management.

Silicone is a widely used biomaterial. Contact allergy, particularly to silicone components of pacemaker coatings, is uncommon. We present a 12-year-old girl with a history of complex congenital heart disease and acquired complete heart block excluding transvenous lead placement.

Divergent proarrhythmic potential of macrolide antibiotics despite similar QT prolongation: fast phase 3 repolarization prevents early afterdepolarizations and torsade de pointes.

Macrolide antibiotics are known to have a different proarrhythmic potential in the presence of comparable QT prolongation in the surface ECG. Because the extent of QT prolongation has been used as a surrogate marker for cardiotoxicity, we aimed to study the different electrophysiological effects of the macrolide antibiotics erythromycin, clarithromycin, and azithromycin in a previously developed experimental model of proarrhythmia. In 37 Langendorff-perfused rabbit hearts, erythromycin (150-300 microM, n = 13) clarithromycin (150-300 microM, n = 13), and azithromycin (150-300 microM, n = 11) led to similar increases in QT interval and monophasic action potential (MAP) duration.