Objectives Atrial oversensing by a ventricular lead may cause asystole in a pacemaker dependent patient or inappropriate shocks in an implanted cardioverter defibrillator recipient patient. In cardiac resynchronization therapy (CRT) devices from Boston Scientific, atrial oversensing by the left ventricular (LV) lead may inhibit LV pacing and impair resynchronization.
Methods A 72-year-old man was implanted with a CRT-D (Cognis 100D, Boston Scientific) in October 2011 for symptomatic (NYHA class 3) ischaemic cardiomyopathy in chronic atrial fibrillation (AF).
Results The LV lead was placed in a large lateral coronary vein. One month later, the LV lead was found displaced at the coronary venous ostium but still captured the myocardium with a low threshold (1 V). In January 2012, the patient was rehospitalized for heart failure. Percentage of stimulation was less than 70% due to AF with a rapid ventricular rate. AV junction ablation was performed and the device programmed in VVI 80 bpm. In February 2012, remote monitoring of the device revealed 99% of RV pacing and 58% of LV pacing. On EGM analysis, intermittent detection of atrial far-field activity led to inhibition of LV pacing. The patient was contacted and LV detection was programmed off. Since that time, the patient remained in NYHA class 2 and remote monitoring confirmed stable 99% of biventricular pacing.
Conclusions In Boston Scientific CRT devices, LV detection is allowed to inhibit pacing in the vulnerable period of an LV premature beat (LV protection period). Atrial LV oversensing has been described during sinus rhythm or atrial flutter. To the best of our knowledge, this is the first case of impairment of resynchronization due to intermittent oversensing of atrial fibrillation potentials by the LV lead. Remote monitoring permitted to make rapidly the diagnosis and to solve the problem.