What causes a pacemaker to fail to capture?

Updated: Feb 13, 2017
  • Author: Daniel M Beyerbach, MD, PhD; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

Answer

Failure to capture occurs when a pacing artifact is not followed by an atrial or a ventricular complex (see the image below). This may be due to the following:

  • Lead fracture

  • Lead dislodgement

  • Fractured lead insulation

  • Elevated pacing threshold

  • MI at the lead tip

  • Drugs (eg, flecainide)

  • Metabolic abnormalities (eg, hyperkalemia, acidosis, alkalosis)

  • Cardiac perforation

  • Poor lead connection at the takeoff from the generator

  • Improper amplitude or pulse-width settings

    Intermittent periods of ventricular capture. Intermittent periods of ventricular capture.

Fibrosis at the endocardial surface where leads were implanted may also occur in the weeks following pacemaker implantation. The fibrosis may create an electrical resistance barrier preventing ventricular depolarization. This may detected as an abnormally high change in impedance (Δ impedance).


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