Mortality and Heart Failure After Upgrade to Cardiac Resynchronization Therapy oleh Bogdan Beca, MASc, John L. Sapp, MD, FHRS, Martin J. Gardner, MD, Christopher Gray, MD, Amir AbdelWahab, MSc, MD, Ciorsti MacIntyre, MD, Steve Doucette, MSc, Ratika Parkash, MS, MD