Strategic Management to Optimize Response To Cardiac Resynchronization Therapy

Inclusion Criteria:

- Subject must be indicated to receive a de novo quadripolar Boston Scientific Cardiac
Resynchronization Therapy Defibrillator (CRT-D) in conjunction with an ACUITY X4 LV
lead. This includes subjects who are indicated to receive an upgrade to a BSC X4 CRT-D
from a previously implanted device.

- In order to achieve a homogenous population for the study, qualifying subjects are
those with heart failure who meet BSC US indications for use defined as those subjects
who receive stable optimal pharmacologic therapy (OPT) for heart failure and who meet
any one of the following classifications:

- Moderate to severe heart failure (NYHA Class III-IV) with EF ≤ 35% and QRS
duration ≥ 120 ms

- Left bundle branch block (LBBB) with QRS duration ≥ 130 ms, EF ≤ 30%, and mild
(NYHA Class II) ischemic or nonischemic heart failure or asymptomatic (NYHA Class
I) ischemic heart failure

- Subject is age 18 or above, or of legal age to give informed consent specific to each
country and national laws

- Subject is willing and capable of providing informed consent

- Subject is willing and capable of complying with visits and procedures as defined by
this protocol

Exclusion Criteria:

- Subjects with documented permanent complete AV block

- Subjects with permanent or chronic atrial fibrillation (AF) or in AF at the time of
enrollment

- Subjects who have previously received cardiac resynchronization therapy with pacing in
the left ventricle

- Subjects on the active heart transplant list or who has or is to receive ventricular
assist device (VAD)

- Life expectancy shorter than 12 months due to any medical condition (e.g., cancer,
uremia, liver failure, etc…)

- Subject with a known or suspected sensitivity to dexamethasone acetate (DXA)

- Subject is enrolled in any other concurrent clinical study, with the exception of
local mandatory governmental registries and observational studies/registries, without
the written approval from Boston Scientific

- Women of childbearing potential who are or plan to become pregnant during the course
of the trial

- Subjects currently requiring dialysis