Severely malfunctioning defibrillator with cardiac resynchronization therapy showing no abnormalities during testing with the programming head in place

In June 2005, a 78-year-old man with complete AV block and junctional escape rhythm in the setting of idiopathic cardiomyopathy with NYHA class III symptoms underwent a pectoral implantation of a Model InSync Maximo 7303 (Medtronic, Inc., Minneapolis, MN, USA) dual chamber implantable cardioverter defibrillator with cardiac resynchronization therapy (CRT-D). The LV lead was placed in the great cardiac vein. In June 2007 at a clinic visit, the Cardiac Compass Trends Report showed that an abrupt change had taken place on 1 December 2006 (see August 2007 Cardiac Compass Trends Report, Figure 1 ). From only a few per cent previously, atrial pacing was now 100%, resulting in DDD pacing at a constant rate of 60 bpm, and based upon the activity indicator, a decline in patient activity. The patient was complaining of fatigue and dyspnoea on exertion, but no dizziness or syncope. A decision to turn rate responsiveness on resulted in a return to the previous level of physical activity and an increase in the heart rate as evidence of at least intermittent ventricular capture. The daily automatic impedance measurements were all normal and stable, but there were no P wave amplitude measurements after 1 December 2006. Whether atrial pacing (competing with spontaneous sinus rhythm) was intermittently captured …