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Fixed coupling: different mechanisms revealed by exercise-induced changes in cycle length

E L Michelson, J Morganroth, J F Spear

    Circulation
    |December 1, 1978
    PubMed
    Summary
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    Fixed coupled ventricular premature depolarizations (VPDs) can arise from parasystolic rhythms, not just reentry. Exercise-induced changes in heart rhythm help differentiate VPD mechanisms.

    Area of Science:

    • Cardiology
    • Electrophysiology
    • Cardiac Arrhythmias

    Background:

    • Ventricular premature depolarizations (VPDs) with fixed coupling are typically attributed to reentry mechanisms.
    • Recent experimental data suggest parasystolic rhythms can also manifest as fixed coupled patterns.
    • Understanding the underlying mechanisms of VPDs is crucial for effective clinical management.

    Purpose of the Study:

    • To investigate the mechanisms of fixed coupled VPDs.
    • To analyze the relationship between VPD coupling intervals and the dominant supraventricular rhythm cycle length during exercise.
    • To determine if exercise can help differentiate between reentrant and parasystolic VPDs.

    Main Methods:

    • Sixty exercise tests were analyzed from patients with frequent, unifocal, fixed coupled VPDs.

    Related Experiment Videos

  • VPD coupling intervals were assessed against varying dominant supraventricular rhythm cycle lengths.
  • Patients were categorized into three groups based on the response of VPD coupling intervals to cycle length changes.

    • Main Results:

    • 32 patients showed a direct linear relationship between VPD coupling intervals and cycle length (suggesting reentry).
    • 16 patients had coupling intervals independent of cycle length (Group 2).
    • 12 patients displayed no consistent relationship (Group 3).
    • Parasystole criteria were met by 2 patients in Group 2 and 4 in Group 3.
    • Fixed coupling of VPDs was not exclusively indicative of reentry.

    Conclusions:

    • Fixed coupling of VPDs does not solely diagnose reentry.
    • Some patients with fixed coupled VPDs exhibit parasystolic rhythms.
    • Exercise-induced changes in cycle length are valuable for analyzing VPD mechanisms.