Moffitt Cardiology Pearls 6.13.17

Thank you, Salman, for presenting a case of a middle-aged man with HIV presenting with repeated “ICD zaps,” fevers, back pain, and night sweats over the last several months. This patient was ultimately found to have a dual-chamber pacemaker with right ventricular under-sensing and spine imaging with evidence of septic emboli and discitis! His unifying diagnosis was enterococcus device infection complicated by endocarditis and discitis.

Key Pearls:

  1. Chest imaging can provide important information about the type of cardiac conduction device and can be used to assess lead placement for pacemakers and ICDs.
  2. MRIs and Pacemakers – almost all newer pacemakers are compatible with MRIs (see below for more details).
  3. You can breakdown the likely bacterial organisms to cause infection of cardiac conduction devices into early and late device infections, similar to how we classify other prosthetic hardware infections.



What can a chest radiograph tell you about a cardiac conduction device?

  1. ICD vs. Pacemaker – can differentiate based on size of generator, presence or absence of a “coil” – the thicker wire that is present in ICDs
  2. Lead placement – can assess for presence of leads in the right atrium, right ventricle, and coronary sinusCheck out this radiology pictorial review of pacemakers and ICDs:

Approach to Pacemaker Malfunction:

  • Under-sensing – inability for PM to detect native beats, often resulting in inappropriate pacing.
    • Lead failure: fracture, misplacement/migration, infection
    • Program failure: not sensitive enough
    • Change in patient’s intrinsic amplitude (infiltrative cardiomyopathy, scar)
  • Over-sensing – PM detecting electricity other than native heart beats, resulting in a failure to pace when it should.
    • Lead misplacement/migration, inappropriate programming (too sensitive)
    • Interference from alternative electronic device
  • Loss of Capture – inability for PM to capture the heart and cause contraction when it delivers a paced beat.
    • Lead failure: fracture, misplacement, infection
    • Metabolic derangements: electrolytes, acidosis

My patient has a pacemaker. Can she get an MRI?

  • Most modern pacemakers are “MRI compatible” and should be safe (though not all radiology departments are comfortable). Interestingly, even older devices are likely safer than previously thought. In this 2017 NEJM study of 1500 patients with non-MRI-conditional pacemakers or ICDs, there were no deaths, lead failures, losses of capture, or ventricular arrhythmias during non-thoracic MRI!
  • Institutions have varying levels of comfort with pacemakers. If the imaging is of high clinical importance, consider involving your EP colleagues to assess safety and facilitate the imaging.

Approach Cardiac Conduction Device Infections (from NEJM link below)




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