Heart failure is a progressive disease that decreases the pumping action of the heart. This may cause a backup of fluid in the heart and may result in heart beat changes. When there are changes in the heart beat sometimes an implantable heart device is used to control the rate and rhythm of the heart beat. In certain heart failure cases, when the two lower chambers of the heart no longer beat in a coordinated manner, cardiac resynchronization therapy (CRT) may be prescribed.

Left Ventricular Capture Management (LVCM) refers to the overall method for determining left ventricular thresholds (level of energy needed to effectively pace the tissue in the lower left chamber of the heart) by measuring, analyzing, and adjusting energy delivered from the CRT device to the pacing lead.

The purpose of the Left Ventricular Capture Management Software Download Clinical Trial was to evaluate the accuracy of the Left Ventricular Capture Management (LVCM) feature to support LVCM feature approval in future cardiac resynchronization therapy with defibrillation (CRT-D) devices

Inclusion Criteria:

• Subjects who successfully underwent implantation of an InSync II Marquis system

Exclusion Criteria:

• Subjects who are post-heart transplant
• Subjects enrolled in a concurrent study that may confound the results of this study