• All Cause Mortality and Heart Failure-related Urgent Care Visits and Heart Failure ("HF") Hospitalizations. [ Time Frame: Enrollment to last visit (up to 45 months post-randomization) or death ] [ Designated as safety issue: No ]
  A composite endpoint of all cause mortality and HF hospitalizations or urgent care. (Emergency Department, Urgent Clinic visits, or hospitalizations wiht intravenous medications for HF)
  
  

• Occurrence of Worsening Heart Failure-related Adverse Events [ Time Frame: Enrollment to last visit (up to 45 months post-randomization) ] [ Designated as safety issue: No ]
  HF event meeting primary endpoint definition, or adverse events associated with, but not limited to, any of the following: symptoms or physical signs compatible with worsening HF, laboratory evidence of HF, any modification of oral heart failure therapy
  
  
• Distribution of Patients by NYHA (New York Heart Association) Functional Class Over Time [ Time Frame: Baseline, 12, 24 and 36 month visits ] [ Designated as safety issue: No ]
  NYHA Classification at each scheduled Follow-up visit. The scale for this measure is as follows: NYHA I= best, NYHA IV= worst.
  
  
• Heart Chamber Dimensions and Wall Thicknesses [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for each endpoint were obtained at multiple time points.
  
  
• Left Ventricular (LV) Ejection Fraction and Fractional Shortening [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]

  Echocardiogram measures for each endpoint were obtained at multiple time points.

  LV Ejection Fraction is the percentage of a patient's blood moved out of the left venricle when the heart pumps. The measure is recorded as a percentage(0-100%) and the normal range is 50-85%.

  LV Fractional Shortening is the percent change in a patient's LV internal dimensions between systole (when the ventricles contract and expel blood) and diastole (when the ventricles expand and receive blood). The measure is recorded as a percentage(0-100%) and the normal range is 30-45%.

  
  
• Left Ventricular (LV) and Left Atrial (LA) Volumes [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for each endpoint were obtained at multiple time points.
  
  
• Left Ventricular (LV) Sphericity Index [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]

  Echocardiogram measures for each endpoint were obtained at multiple time points.

  LV Sphericity Index is a ratio of LV long axis dimension to the LV short axis dimension. Healthy hearts have an elliptical LV cross-sectional shape. A value of 1 denotes a circular or more globular shape, while larger values denote healthier hearts with more elliptical cross sections. Literature has shown that when the ratio used is short axis/long axis, normal hearts have a median LV sphericity index of 0.56, with a range of (0.51-0.60). This translates to median=1.79,range=(1.67,1.96) for long/short axis.

  
  
• Hemodynamic Velocity Measures [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for each endpoint were obtained at multiple time points.
  
  
• Hemodynamic Deceleration Time [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for each endpoint were obtained at multiple time points.
  
  
• Left Atrial (LA) and Mitral Regurgitation (MR) Areas [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for each endpoint were obtained at multiple time points.
  
  
• Composite Mitral Regurgitation (MR) Severity Score [ Time Frame: Baseline, 12, and 24 month visits ] [ Designated as safety issue: No ]
  Echocardiogram measures for this endpoint were obtained at multiple time points. Composite MR Severity was measured on a scale of "None to Trivial" to "Grade IV", with Grade IV being the worst possible score and "None to Trivial" being the best possible score.
  
  
• Occurrence of Ventricular Tachycardia ("VT") and Ventricular Fibrillation ("VF") Episodes [ Time Frame: Enrollment to last collection of data from the implanted ICD (up to 45 months post-randomization) ] [ Designated as safety issue: No ]
  Annualized Rates of Days of True VT/VF and Inappropriately detected non-VT/VF
  
  
• Occurrence of Clinically Important or Persistent Atrial Tachycardia or Atrial Fibrillation (AT/AF) in Subjects With no Prior AF History [ Time Frame: Enrollment to last collection of data from the implanted ICD (up to 45 months post-randomization) ] [ Designated as safety issue: No ]

  Persistent AF was defined as any of the following:

  1. 2 consecutive visits in which the patient presents with AF
  2. 7 consecutive days of at least 22 hours per day of AT/AF
  3. A cardioversion prior to 7 consecutive days of at least 22 hours per day of AT/AF

  Clinically Important AF was defined as more than 20 hours of AT/AF in a single day

  
  
• Development of a Pacing Indication During the Study [ Time Frame: Enrollment to last visit (up to 45 months post-randomization) ] [ Designated as safety issue: No ]
  Physician identification of a Class I Pacing Indication. A Class I Pacing Indication implies that the benefit of pacing the heart far exceeds the risk, and that the procedure to implant the pacing device should be performed. For this indication there is general agreement that pacing the heart is beneficial, useful, and effective.
  
  
• Medication Usage Affecting Heart Rate and Atrioventricular ("AV") Conduction [ Time Frame: Enrollment, 6 Months, 12 Months, 24 Months, 30 Months, 36 Months ] [ Designated as safety issue: No ]
  Whether a subject is on each of a pre-specified set of drugs or classes of drugs.
  
  
• Percent Ventricular Pacing [ Time Frame: Enrollment, 6, 12, 24 and 36 month visits ] [ Designated as safety issue: No ]
  The percentage of a patients' ventricular beats that were paced by the device.
  
  
• Quality of Life ("QOL") Score [ Time Frame: Baseline, 12, 24, and 36 month visits ] [ Designated as safety issue: No ]

  Minnesota Living with Heart Failure Questionnaire ("MLWHFQ") and Kansas City Cardiomyopathy Questionnaire ("KCCQ") Quality of Life("QOL") Scores. For KCCQ, positive values mean improved QOL compared to baseline. For MLWHFQ, negative values mean improved QOL compared to baseline.

  Scales: KCCQ 0-100 (0=worst, 100 best); MLWHFQ 0-105 (105=worst, 0=best)

  
  
• All Cause Mortality [ Time Frame: Enrollment to last visit (up to 45 months post-randomization) or death ] [ Designated as safety issue: No ]
  Death from any cause
  
  
• ICD-indicated Patients With Class I Pacemaker Indication. [ Time Frame: Period of time prior to patient consent when considering patient for Implant/Enrollment ] [ Designated as safety issue: No ]
  Number of subjects screened prior to enrollment that had Class I pacing indication at time of implant
  
  

Recent research supports the hypothesis that reducing the amount of pacing in the lower right chamber of the heart may prevent the progression of congestive heart failure (CHF) in some implantable cardioverter defibrillator (ICD) patients. CHF refers to symptoms (shortness of breath, fatigue, fluid overload) caused by decreased pumping action of the heart muscle. The ICD can be set to use one wire (top or bottom of the heart) or two wires (top and bottom). Both settings allow the heart to beat more naturally using its own electrical signals. Two device settings will be compared. Managed ventricular pacing (MVP) will allow the ICD to use both wires only as necessary. This setting allows the ICD to send electrical signals to the top and bottom chambers of the heart if needed. The other setting, ventricular pacing (VVI) will allow the ICD to operate the bottom chamber of the heart if it is needed.