Cardiac resynchronization therapy (CRT) or biventricular pacing is a useful treatment for heart failure and those suffering from arrhythmias. The purpose of this research study is to determine the effect left-ventricular pacing has on patients who have a ventricular assist device.

As part of the study participation the following two visits will be completed as listed below.

Baseline Visit: The following procedures will be conducted at this visit:

• Review of past medical history and medical records;
• A limited echocardiogram will be performed. This is a test that uses ultrasound to evaluate the size of the heart and how well the heart is pumping blood.
• The investigators will use a computer-like device, called a programmer, that "talks" to the CRT device using radio signals or by using wanded telemetry to adjust the CRT device's programmed settings. The left ventricular lead of your device will be turned off. The defibrillator will continue to function and back-up pacing will continue if needed.
• Complete the Kansas City Cardiomyopathy Questionnaire (KCCQ).
• A 6 minute walk test will be done.

Regularly Scheduled Clinic Visit: At the next regularly scheduled Left Ventricular Assist Devices (LVAD) clinic visit, approximately 4 weeks after the baseline visit, the following procedures will be done:

• A second limited echocardiogram.
• The investigator will use a computer-like device, called a programmer, that "talks" to the CRT device using radio signals or by using a wand to obtain a report that will give the current program settings and any heart rhythm events that have occurred since the last CRT device was checked. Once the information from the CRT is obtained, the study doctor will reprogram the device to its original settings.
• Complete the Kansas City Cardiomyopathy Questionnaire (KCCQ).
• A 6 minute walk test will be done.

Inclusion Criteria:

• Presence of LVAD support and CRT device with working LV lead in patients > 18years of age
• Left ventricular pacing at time of enrollment

Exclusion Criteria:

• LV lead dysfunction
• Prior AV node ablation
• Presence of total heart block
• Presence of significant bradycardia/lack of underlying rhythm
• Inability to complete 6 minute walk test
• Inability to return to clinic for repeat assessment
• Any LVAD programmed speed change within the prior 30 days
• Any CRT programming changes within the prior 30 days

Adults with ventricular dysfunction, dyssynchrony, functional capacity presence of arrhythmia. LVAD patients undergo 6 minute walk testing and complete a quality of life questionnaire routinely as part of their care on our LVAD clinic. Additionally, periodic echcoardiography is obtained to determine LVAD dynamics and ventrocular dimensions. We will utilize this information for our study, as well as information from their cardiac resynchronization devices, which is part of routine care for patietns with pacemakers and defibrillators.