Correlating QLV Interval to Left Ventricular (LV) Lead Position in Patients Receiving Cardiac Resynchronization Therapy.

Heart failure is a growing epidemic in the United States. Heart failure is associated with
shortness of breath, reduced exercise tolerance, and manifestations of peripheral fluid
retention. As the disease progresses, there is development of cardiac dyssynchrony (failure
of the heart to act as one unit) in the electrical and mechanical functions of the
myocardium.

During implantation of a cardiac resynchronization therapy defibrillator (CRT-D) device,
three electrical wires are placed in the right atrium (RA), right ventricle (RV) and
coronary venous system that drains blood from the left ventricle (LV). The LV lead is placed
in the posterolateral tributaries of the coronary venous system using special delivery
tools. Pacing therapies to resynchronize the heart have been shown to improve functional
class and mortality in patients with severe heart failure i.e. New York Heart Association
(NYHA) class III and IV functional status. Current indications for cardiac resynchronization
therapy (CRT-D) include severe cardiomyopathy (Ejection Fraction < 35%), with shortness of
breath at rest or minimal exertion (NYHA class II, IV), prolonged QRS > 130ms on surface
echocardiogram (ECG) and life expectancy more than one year. CRT-D therapy results in
decrease of heart failure admissions and improvements in quality of life.

Response to CRT is associated with improvement in functional status by one NYHA functional
class schema or by evidence of reverse remodeling (decrease in end systolic LV dimension by
15%). However across clinical trials, a third of the patients are non-responders to CRT
therapy. Non-ischemic etiology of heart failure and presence of electrical dyssynchrony on
surface ECG suggested by QRS >150ms are associated with better response with CRT. Non
response to CRT can be due to inappropriate patient selection, inappropriate device
programming, and inappropriate lead placement. However, inappropriate lead placement is the
factor that can be changed during device implantation. Adverse changes in morality and heart
failure can occur with sub-optimal position of the LV lead. Most echocardiographic
parameters to predict responders were not clinically useful. Appropriate positioning near
the area of the heart with latest activation (usually posterolateral segment of the left
ventricle) is associated with better response. Inter-ventricular delay as measured by the
time delay between the two leads in the left and right ventricles (RV-LV delay) was shown to
be a better predictor of response. Interval from the first deflection of the surface ECG to
the bipolar electrogram (QLV interval) can be used as a surrogate to identify the delayed
segments of the left ventricle. Preliminary studies have shown better response using this
approach of lead placement in the regions of latest activation. SMART AV study which used a
similar algorithm in assessing delay also showed a trend for better response using QLV
interval. However, the fluoroscopic lead position was not correlated with QLV interval for
that study. We plan to measure this area of delayed activation to target effective lead
placement and map the coronary veins to target the longest QLV interval in each patient.

For this study, medical history and demographic information will be collected from patients
as well as clinical information from the procedure. The QLV measurements will be collected
prior to implant of LV lead. The QLV interval is defined as the measurement from the onset
of the QRS width of the surface ECG to the first large positive or negative peak of the LV
electrogram (EGM) during a cardiac cycle. QLV EGM will be taken from either the LV pacing
lead and/or .014 wire. QLV EGM's will be measured at three distinct points (basal, mid, and
distal) within each target vessel. Each data point will be the average of four to six beats
to allow for respiratory variance, and recorded using the Bard mapping system. The final
lead position will be the area of vein that has the longest QLV interval with appropriate
sensing and pacing thresholds. The QLV measurements will be conducted, in addition to all
standard of care procedures for CRT-D implantation for patients enrolled in the clinical
trial.

Inclusion Criteria:

- Patients who are indicated for CRT-D devices according to the current guidelines for
implantation of cardiac pacemakers and antiarrhythmia devices

Exclusion Criteria:

- Patients who are under the age of 18

- Patients who are pregnant

- Patients who cannot have intravenous contrast due to allergic reactions or chronic
renal insufficiency

- Patients who are unable or unwilling for any reason to consent for this study