Cardiac Devices

Cardiac Devices - Mark Sonderman

  • Permanent Pacemaker
    • A battery that provides electrical current to 1 or 2 leads (RA and/or RV) which stimulates the myocardium when the innate electrical activity of the heart is insufficient
    • Indications (typically requires symptoms):
        • Sinus Node Dysfunction
        • AV node dysfunction (2nd Degree Type II with sx or Type 3 block, carotid sinus hypersensitivity, after catheter ablation of AV node for AF)
        • Bifascicular or alternating L and RBBB
  • ICD
    • RV Lead (can also be epicardial) that contains a coil for defibrillation in case of VF or VT; additionally performs ATP (anti-tachycardia pacing) to ideally prevent a shock
    • Indications:
        • Primary Prevention: In general, think about those at risk for sudden cardiac death.
          • CHF with EF <35%and NYHA II-III on max GDMT
          • LVEF <30% and post-MI >40d
          • Consider Brugada, ARVC, HCM, sarcoid, Long QT, congenital disease (SCD) 
        • Secondary Prevention: Survivors of VF arrest, unstable VT w/o reversible cause, and structural heart disease with history of sustained VT
  • CRT
    • 3 Lead Pacemaker (RA, RV, coronary sinus to LV) that coordinates LV/RV contraction through synchronized activation of each ventricle
    • Patients with HFrEF and ventricular conduction delay (prolonged QRS) are at highest risk for HF progression and this aims to reverse it.
    • Indications:
        • Class I: EF<35%, NYHA II- IV ambulatory, on GDMT, NSR with LBBB and QRS 150
        • Class IIa: Above criteria with minor differences (LBBB & QRS 120-149, non-LBBB and QRS 150) OR EF<35% and expected to require >40% ventricular pacing


Interpreting Pacemaker Codes


1st Letter

2nd Letter

3rd Letter

4th Letter

A: atrial, V: ventricular, D: dual, O: none, I: inhibition, R: rate-adaptive

Chamber Paced

Chamber Sensed

Response to Sensed Beat

Program Features


Examples of Common Pacing Modes:

  • VVI: Single RV lead that delivers a beat if no beat sensed. Often used with chronic AF with bradycardia
  • DDDR:  Senses and paces both the atria and ventricle. If beat not sensed within a predefined interval, beat delivered. R indicates rate responsivity (changes rate based on changes in patient activity)
  • Magnet: Paces at a fixed rate without respect to native electrical activity (AOO,VOO,DOO). Deactivates ICD shock. Often used in surgery or at end of life to avoid ICD shocks


Additional Information

  • The Pacemaker ID app is free and is useful for identifying device brand for interrogation


Device leads