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Steps to Checking Pacing Thresholds

Control irregular heartbeats more effectively by checking pacemaker pacing thresholds. According to the National Heart, Lung, and Blood Institute, a pacemaker fixes a heart's faulty sinoatrial node, which uses electrical signals to control the rhythm and rate of a heart's contractions and pumping. Either temporary or permanent, pacemakers must be programmed to find the right pacing threshold for each individual patient to prevent dependency.

  1. Types

    • The heart has two atriums and two ventricles.

      Three basic types of pacemakers are available for patients with abnormal heart rhythms. Single-chamber atrial pacers are for patients who have an intact cardiac conduction system, which means that the basic structure of the heart is sound. These pacemakers only enhance the heart to produce an optimum heart rhythm. Ventricular pacers are for patients who need to speed up their heart rates. Atrioventricular sequential pacers use leads in the atriums and ventricles to synchronize the heart's rhythm.

    Implanting

    • The doctor makes a 2-inch-long incision in the upper chest to implant the pacemaker. He guides one or two insulated wires through a vein into the right atrium or the right ventricle. The right atrium is the chamber above the right ventricle. The wires are carefully marked and later connected to the pacemaker. Doctors first must set the correct output in terms of rate of stimulations per minute, amount of energy needed and its location.

    Testing

    • Doctors first measure intrinsic heart signals before the pacemaker is fully connected. They perform this to prevent the patient from becoming pacemaker dependent. The patient's pacing threshold is tested by an intracardiac electrogram, which measures the heart's electrical activity from inside its chambers. Leads are moved to different areas and tested, which is called mapping.

    PSA

    • A Pacing System Analyzer or PSA delivers and measures electrical pulses before the wires are plugged into the pacemaker. It is first programmed to a pacing rate beyond the patient's intrinsic heart rhythm to mimic how the pacemaker will work. This captures the heart, or initiates a response which is seen as a spike on the intracardiac electrogram. Then the output electrical pulse is lowered on the PSA until the capture is lost. The point right before it is lost is considered the pacing threshold, or the minimum energy needed to capture the heart.

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