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Heart rate score, a measure related to chronotropic incompetence in pacemaker patients
Arjun D Sharma1, Mark Richards2, Brian Olshansky3
1Medical Devices Consultants LLC, St Paul, Minnesota.
Insights
Heart rate score (HrSc) predicts mortality in defibrillator patients. In pacemaker patients, a high HrSc (≥70%) indicates chronotropic incompetence (CI) and correlates with sick sinus syndrome.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Device Technology
Background:
- Heart rate score (HrSc) ≥70% predicts 5-year mortality in defibrillator patients.
- High HrSc indicates few sensed cardiac cycles above the programmed lower rate.
Purpose of the Study:
- To determine if HrSc relates to chronotropic incompetence (CI) in pacemaker (PM) subjects.
- Investigate HrSc as a potential non-invasive marker for CI.
Main Methods:
- Retrospectively analyzed 1-month postimplant PM rate histograms for HrSc (percentage of events in the tallest 10 beats/min bin).
- Compared HrSc to treadmill-based CI measures and clinical indications in the prospective LIFE study.
- Utilized DDD 60/min pacing mode for analysis.
Main Results:
- 43% of subjects had HrSc ≥70%, correlating with sick sinus syndrome (P < .001).
- Treadmill-based CI measures showed poor agreement (39%-83%).
- HrSc ≥70% strongly correlated with unpaced heart rate <70% of age-predicted maximum (67%) (OR 3.7, P < .001).
Conclusions:
- HrSc ≥70% correlates with treadmill-derived CI measures and clinical sick sinus syndrome.
- HrSc is a validated, inexpensive, repeatable, and quantitative measure of CI in pacemaker patients.
Background:
Heart rate score (HrSc) ≥70% in cardiac resynchronization therapy defibrillator and implantable cardioverter-defibrillator subjects predicts 5-year mortality risk. A high HrSc suggests few sensed cardiac cycles above the programmed lower rate.
Objective:
To determine if HrSc is related to chronotropic incompetence (CI) in pacemaker (PM) subjects.
Methods:
HrSc is the percentage of all atrial-paced and sensed events in the single tallest 10 beats/min histogram bin programmed to DDD 60/min. The prospective LIFE study of PM subjects examined multiple treadmill-based measures of CI. The 1-month postimplant DDD 60/min PM rate histogram prior to treadmill was retrospectively analyzed for HrSc. Measures of CI were applied to submaximal treadmill data in the DDD mode. HrSc was compared to these CI measures and to clinical indications for PM.
Results:
The 1-month histogram demonstrated HrSc ≥70% in 43% of subjects. HrSc ≥70% correlated with a clinical diagnosis of sick sinus syndrome (P < .001). CI was present in 34%-88% of subjects by treadmill-based measures. Agreement between treadmill-based measures for CI was poor and varied from 39% to 83%. HrSc ≥70%, as a measure of CI, was most highly correlated with unpaced heart rate <70% of age-predicted maximum heart rate (67%) (odds ratio 3.7, P < .001).
Conclusions:
HrSc ≥70% correlates with treadmill measures of CI and clinical sick sinus syndrome. HrSc ≥70% is a measure of CI in PM subjects that is inexpensive, repeatable, and quantitative.
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