Hemodynamic evaluation
Patients were evaluated in the electrophysiology laboratory to select the pacing site and atrioventricular (AV) delay that provided the best hemodynamic response. This was determined by the largest increase in aortic pulse pressure and LV maximum pressure rate increase measured by a dual-pressure transducer catheter inserted into the LV via the femoral artery. For this test, standard electrophysiologic catheters were advanced from the femoral vein to pace inside the right ventricle (RV). An over-the-wire EASYTRAK lead (model 4512, Guidant Corp., St. Paul, Minnesota) was advanced from the jugular vein into the coronary sinus to pace LV sites through the coronary veins. Left ventricular pacing was compared at two to four different sites in all patients. Right ventricular pacing was tested only in patients having right bundle branch block. The best pacing site was documented radiographically to guide permanent lead placement during device implantation. Details of the hemodynamic evaluation protocols and instrumentation have been previously described 21 and 22.