Cardiac Pacemakers The heart is bestowed with a specialized system that automatically generates rhythmic control via the sinus node, located in the superior lateral wall of the right atrium near the opening of the superior vena cava. The specialized pacemaker cells dictate control of the rest of the heart through regular electrical impulses that propagate from the right atria to the lower ventricles. The rapid conduction of these impulses cause the muscle cells of the atria to contract and squeeze blood into the ventricles, which contract and force blood into the aorta and pulmonary arteries. Abnormalities of the heart rhythm, called arrhythmias