How effective is a pacemaker in preventing heart failure?

It's not: Heart failure can be the result of many different problems such as heart attacks which weaken the heart muscle, untreated hypertension which can leas to a stiff heart, or drug toxicity such as can occur with certain types of chemotherapy. Decrease your chances of developing heart failure by managing your identifed risk factors (i.e. Hypertension). A pacemaker may be needed in advanced heart failur.

Two scenarios: If low heart beat is contributing to heart failure a pacemaker might help. If you have a weak heart with ejection fraction less than 35% and a conduction abnormality known as LBBB ( left bundle branch block) a special type of pacemaker or defibrillator to overcome the conduction abnormality will help improve heart pump function and quality of life in 70% of such patients. This is known as crt.