Conduction System Pacing With Left Bundle Branch Pacing as Compared to Standard Right Ventricular Pacing

This study compares two ways of placing a pacemaker in people with heart block (where signals between the heart's upper and lower chambers are blocked). It compares traditional right ventricle pacing to a newer technique called left bundle branch pacing, which mimics the heart's natural rhythm more closely. **You may be eligible if...** - You are 18 or older - Your heart's pumping strength (ejection fraction) is greater than 35% - You have been diagnosed with high-degree heart block requiring a pacemaker, and your doctor expects you to need pacing more than 90% of the time - You had a recent echocardiogram (heart ultrasound) within the last 3 months - You have third-degree AV block, second-degree AV block, or significant first-degree AV block with symptoms **You may NOT be eligible if...** - Your ejection fraction is 35% or less - You have had a prior pacemaker or defibrillator implanted - You are not expected to require frequent pacing - You have active infection or other conditions making surgery unsafe Talk to your doctor to see if this trial is right for you.