Impact of Septal Vs Apical Pacing on Right and Left Ventricular Performance

Prolonged pacing from the right ventricular (RV) Apex has been shown to be associated with progressive left ventricular (LV) dysfunction. This has led to an interest in alternative right ventricular pacing sites. Only very few studies investigated the effect of alternative right ventricular pacing sites using three dimensional imaging. Using cardiac MRI volumetric left- and right ventricular analysis and three-dimensional reconstruction is more accurate compared to trans-thoracic echocardiogram. St. Jude Medical has developed a MRI conditional pacemaker system enabling for the first time to investigate alternative pacing sites using cardiac MRI. Patients already implanted with an MRI conditional pacemaker system from St. Jude Medical will be enrolled in that study and subdivided into 4 groups (right ventricular pacing lead positioned apically or septally subdivided in patients paced for <50% of time or 50% or more). All patients will undergo cardiac MRI at enrollment and again 12 months later. Patients paced <50% of the time will undergo cardiac MRI with and without pacemaker stimulation at both visits.