This is a mechanistic clinical trial with randomization to guidance for the CRT procedure using cardiac magnetic resonance (CMR) and computed tomography angiography (CTA) versus a standard procedure.

At baseline, patients will have CMR, CTA, echocardiography, blood testing, and cardiopulmonary exercise testing. They will also complete a heart failure questionnaire. In patients randomized to CMR guidance for the CRT procedure, LV lead placement will be guided by the MRI information related to scar, activation and anatomy. Patients will have follow-up assessments at 6 and 12 months. There will also be clinical follow-up for survival free of appropriate ICD therapies over 3 years.

Inclusion Criteria:

1. Chronic systolic HF
2. LVEF 35% or less
3. Guideline-based class I or II indication for CRT

Exclusion Criteria:

1. Inability to provide informed consent
2. Pregnancy
3. Presence of metal embedded in the body due to prior accident or injury, as documented by skull films or other imaging
4. Cerebral aneurysm clips
5. Cochlear implants
6. Other metallic implants known to be contraindications to CMR (does not include pacemakers and ICDs)
7. Severe claustrophobia
8. Acute kidney injury
9. Acute renal failure or chronic kidney disease with GFR < 45 cc/min/1.73m2
10. Liver transplant
11. Gadolinium allergy
12. >10% premature ventricular contraction (PVC) burden; and 13) estimated >10% atrial fibrillation (AF) burden based on available clinical data.