• LV ejection fraction measured by radionuclide ventriculography (RVG).
  

• 1. left ventricular diastolic and systolic function indices 2-D echocardiogram/Doppler (ECHO/DOPP)
  
• 2. all cause mortality
  
• 3.non-fatal thromboembolic events including stroke
  
• 4.heart failure hospitalization or intravenous drug therapy in an outpatient heart failure clinic
  
• 5.occurrence of new-onset atrial fibrillation or progression to permanent atrial fibrillation
  
• 6. symptoms and quality of life scores (DUke Activity Status Index, short form (SF)-12 scores
  
• 7. NYHA class using SAS survey, 6 minute hall walk distance
  
• 8. serum brain natriuretic peptide level (BNP), which has been shown to be elevated in ventricular paced patients
  
• 9. lead-related complications such as lead dislodgement, myocardial perforation, lead integrity failure, high pacing threshold
  
• 10. total implant procedure and flouroscopy time
  

The primary objective of this study is to compare the effect of RV pacing site on LV systolic function as measured by LVEF (left ventricular ejection fraction).

Secondary objectives of this trial include:

1. to compare the effect of RVSeptal(RVS) versus RVApical(RVA)pacing on other indices of systolic and diastolic LV function
2. to compare the rate of heart failure-related hospitalization between RVS versus RVA pacing
3. to compare new-onset atrial fibrillation and stroke rates between RVS versus RVA pacing
4. to assess the effect of RVA versus RVS pacing on quality of life and functional capacity
5. to compare the rate of successful pacemaker lead implantation, complications and chronic electrical performance of RVS versus RVA pacing

Inclusion Criteria:

1. a)Fixed (third degree) AV block b) Atrial Fibrillation with average Ventricular rate on ECG </= 40bpm or mean heart rate on Holter monitor </= 60bpm c) Sinus node Dysfunction with PR interval >/= 300msec d) Paroxysmal, persistent or permanent AF undergoing AV node , AV node/HIS ablation
2. the subject is 18 years of age or older
3. the subject has provided written consent -

Exclusion Criteria:

1. Pre-existing permanent cardiac pacemaker or ICD (defibrillator)
2. Presence of Hypertrophic Obstructive Cardiomyopathy
3. Recent cardiac surgery (</= 30 days)
4. Recent myocardial infarction (</= 30 days)
5. Presence of mechanical prosthetic tricuspid valve
6. Patient inability or unwillingness to comply with study protocol and required study visit schedule
7. Concomitant research study whose protocol would conflict or affect the outcome of this study
8. Patient not expected to survive for the duration of the study follow-up due to co-morbid medical condition -