Complete AV blocks and diseases involving sinus node dysfunction are the most frequent reasons for treating the patient with chronic pacing. This patient population makes up about 40% of all pacemaker implantations. Other indications for pacemaker placement include bradycardia, atrial fibrillation, bifascicular blocks, and incomplete trifascicular blocks. 

Patients with second-degree AV block, sick sinus syndrome, long QT interval syndromes, sleep apnea, hypertrophic obstructive cardiomyopathy, and heart failure with wide QRS complexes are also potential candidates for pacemaker implantation.

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Pacing In Heart Failure

Heart failure causes a prolonged QRS duration > 0.12 seconds, which can worsen left ventricular ejection fraction function in these patients, especially in light of dyssynchronous ventricular contraction. Synchronous pacing of the right and left ventricle allows the QRS complex to shorten and improves ventricular function. 

This method introduces a conventional electrode over the right ventricle and an additional electrode in the left ventricular epicardium. This approach to pacing is also effective in patients with left and right bundle-branch block.

Pacing In Hypertrophic Obstructive Cardiomyopathy

Cardiac pacing is indicated for patients with medically refractory and symptomatic hypertrophic obstructive cardiomyopathy. Dual-chamber pacing improves the symptoms by lowering the left ventricular outflow tract gradients. Right ventricular pacing moves the ventricular septum toward the right ventricle during systole, which widens the left ventricular outflow tract.