Study of Paced QRS Duration as a Marker of Sudden Cardiac Death

• Methods and Procedures Subjects for this study will be enrolled from the ICD clinic at
Pocono Medical Center. The ICD clinic at Pocono Medical Center is located in the cardiology
office 2.4 miles from the main hospital building where patients undergo interrogation of
their ICD under the direction of the principal investigator.

During a routine ICD interrogation, the patient is attached to a 3 lead surface ECG. The ICD
is then checked to assess sensing and pacing parameters and impedance for leads in all
cardiac chambers. Battery voltage is assessed, and any stored events which include data from
any appropriate or inappropriate therapies, are examined. Appropriate therapies consist of
either an ICD shock or anti-tachycardia pacing for ventricular tachyarrhythmias.
Inappropriate therapies consist of either an ICD shock or anti-tachycardia pacing for an
event other than ventricular tachyarrhythmias, and may be triggered by supraventricular
tachyarrhythmias or electronic noise.

Once the subjects are enrolled in the study, a 12-lead ECG will be performed (instead of a 3
lead ECG) before ICD interrogation (baseline ECG). A 12 lead ECG will then be repeated while
performing right ventricular pacing through the programmer at 100 beats per minute at the
time of pacing threshold testing (paced ECG). QRS durations from the baseline and paced ECG
will be measured electronically in leads V3-V6. The measured QRS complexes should not be
preceded by an atrial or ventricular premature complex.

All subjects will then continue to be followed every three months in the ICD clinic for
routine ICD interrogation as clinically indicated for the duration of the study. Data for
any appropriate and inappropriate ICD therapies will be retrieved and documented in the case
report form. Subjects will be considered to have suffered SCD if they meet one of the
following criteria.

- An appropriate ICD therapy (shock or anti-tachycardia pacing)

- Death occurring within one hour of onset of cardiac symptoms

- Death during sleep

- Unwitnessed death in a formerly stable patient

- Death during attempted resuscitation Data regarding mortality will be obtained from
patient's family, family physician and hospital records.

- Project Plan Based on the current patient volume in the ICD clinic, and the rate of new
ICD implants, it is estimated that enrolling 250 patients will take 3 years. The study
will conclude when the last enrolled patient has been followed for 2 years. The
follow-up period will, therefore, be 2-5 years for patients enrolled in the study. The
total study duration is therefore expected to be 5 years.

- Data Analysis and Data Monitoring At enrollment and at each subsequent visit, the
following data will be collected.

- Demographic data: age, gender and racial and ethnic origin, height, weight and vital
signs including heart rate and blood pressure

- Co-morbid conditions: coronary artery disease, congestive heart failure, diabetes,
hypertension, smoking, dyslipidemia, family history of sudden cardiac death in a first
degree relative, renal failure, and others

- Medical regimen: all medications being taken at the time of visit

- Testing of Cardiac substrate: reports of most recent 24 hour ambulatory
electrocardiography, echocardiogram, stress test, multigated acquisition scan,, cardiac
catheterization and revascularization, coronary artery bypass surgery, and
electrophysiological evaluation

- Details of ICD implantation: indication for ICD implantation (primary versus secondary
prevention), type of ICD implanted (single chamber, dual chamber or biventricular) as
well as the manufacturer, and the position of the right ventricular lead (apical versus
septal)

- Prolonged paced QRS duration will be defined as ≥150 ms, narrow paced QRS duration will
be defined as <150 ms. All baseline characteristics of patient population will be
expressed as percentages. Relative risk of SCD with prolonged paced QRS duration will
be determined. Kaplan-Meier analysis will be done using the end-point of appropriate
ICD therapy used as a surrogate marker of SCD, and clinical SCD to generate survival
curves for each subgroup .

Inclusion Criteria:

- 18 years old or older

- Male or female

- Subjects followed in the ICD clinic at Pocono Medical Center who have undergone ICD
implantation within 3 years prior to the date of enrollment, and those who undergo
ICD implantation during the enrollment period, whether for primary prevention or for
secondary prevention based on standard indications will be included in the study.

- Patients with single chamber, dual chamber and biventricular devices manufactured by
all three major vendors (Boston Scientific, St Jude Medical and Medtronic) will be
considered.

Exclusion Criteria:

- Life expectancy of less than one year

- Severe reaction to the adhesive material on ECG patches