The Effect of CRT on the Frank Starling Mechanism

(Control Group): One test of the Starling mechanism Visit 1: Sign consent form, doctor assessment, electrocardiogram (ECG), Starling Test. If patients are in this category, this will be their only research visit

(CRT Group): Two tests of the Starling mechanisms Visit 1: Sign consent form, assessment by doctor, electrocardiogram (ECG), Test of the Starling mechanism Visit 2: CRT upgrade procedure - your Cardiologist will explain this procedure to you. Visit 3: CRT pacing check at 6 weeks post-procedure Visit 4: Assessment by doctor, ECG, Echocardiogram, Test of the Starling mechanism at 6 months post-procedure.