Correlation between surface and intracardiac electrocardiogram in a patient with inappropriate defibrillation shocks due to hyperkalemia

A case of inappropriate implantable cardioverter defibrillator therapy induced by T-wave oversensing due to hyperkalemia

There have been reports of hyperkalemia-induced T-wave oversensing in patients with implantable cardioverter defibrillators (ICDs). However, a comparison of T-wave amplitudes and morphologies between the surface 12-lead electrocardiogram (ECG) and ICD electrogram has not been reported. We present the case of a 70-year-old man who received inappropriate ICD shocks due to hyperkalemia-induced T-wave oversensing. The T-wave amplitudes on both the ICD electrogram and 12-lead ECG corresponded and normalized after normalization of the potassium level.

An inappropriate defibrillator shock during ventricular tachycardia

Ventricular oversensing in patients with defibrillators is an infrequent but deleterious condition. We report a patient with a cardiac resynchronization–defibrillation device that presented with hyperkalemia and syncope. Device interrogation revealed ventricular double-counting within the QRS of a slow ventricular tachycardia, resulting detection of the slow ventricular tachycardia in the ventricular fibrillation zone, and delivery of an effective therapy, below device programmed detection rate. This case of defibrillator inappropriate detection emphasizes the relevance of device electrogram interrogation in order to minimize inappropriate therapies.

Laboratory markers of ventricular arrhythmia risk in renal failure

Sudden cardiac death continues to be a major public health problem. Ventricular arrhythmia is a main cause of sudden cardiac death. The present review addresses the links between renal function tests, several laboratory markers, and ventricular arrhythmia risk in patients with renal disease, undergoing or not hemodialysis or renal transplant, focusing on recent clinical studies. Therapy of hypokalemia, hypocalcemia, and hypomagnesemia should be an emergency and performed simultaneously under electrocardiographic monitoring in patients with renal failure. Serum phosphates and iron, PTH level, renal function, hemoglobin and hematocrit, pH, inflammatory markers, proteinuria and microalbuminuria, and osmolarity should be monitored, besides standard 12-lead ECG, in order to prevent ventricular arrhythmia and sudden cardiac death.

Inappropriate pacing inhibition triggered by QT prolongation due to T wave oversensing in an ICD recipient presenting with long QT syndrome

Inappropriate inhibition of atrial pacing due to T-wave oversensing (TWOS) was observed in a patient presenting with congenital long QT syndrome, treated with an implantable cardioverter defibrillator (ICD) and beta-adrenergic blocker. Development of TWOS was associated with further QT interval prolongation in the absence of amplitude changes in the intracardiac T and R waves. Replacement of the ICD generator with a sensing filter designed to attenuate the intracardiac T wave suppressed TWOS and normalized the pacing functions.