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Risk Prediction After Myocardial Infarction by Cyclic Variation of Heart Rate, a Surrogate of Sleep-Disordered
Xu Cao1, Alexander Müller1, Ralf J Dirschinger1
1Klinik und Poliklinik für Innere Medizin I, University Hospital Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany.
Insights
Sleep-disordered breathing (SDB) in myocardial infarction (MI) survivors did not predict mortality. However, a flat heart rate tachogram on Holter ECGs strongly and independently predicted 5-year all-cause mortality in these patients.
Area of Science:
- Cardiology
- Sleep Medicine
- Medical Diagnostics
Background:
- Sleep-disordered breathing (SDB) is prevalent in cardiac patients, but its independent prognostic value post-myocardial infarction (MI) remains uncertain.
- Cyclic variation of heart rate (CVHR) is a physiological marker associated with SDB.
Purpose of the Study:
- To assess the association between SDB, identified by CVHR on Holter ECGs, and 5-year mortality in acute MI survivors.
- To investigate the predictive value of SDB-related CVHR for mortality after MI.
Main Methods:
- Prospective enrollment of 1590 acute MI survivors in sinus rhythm, followed for 5-year all-cause mortality.
- Analysis of nocturnal Holter ECGs to quantify minutes with CVHR, with SDB defined as ≥72 min of CVHR.
- Exclusion of 77 patients with flat HR tachograms, leaving 1513 for SDB classification.
Main Results:
- SDB was identified in 38.6% (584/1513) of eligible patients; no significant mortality difference was observed between SDB and non-SDB groups.
- Low CVHR duration, as a continuous variable, was associated with increased mortality.
- Patients with flat HR tachograms exhibited significantly increased mortality, independent of clinical risk factors and other ECG markers like HRV, HRT, and DC.
Conclusions:
- While SDB signs were common in MI survivors, they were not linked to mortality.
- A flat nocturnal heart rate tachogram emerged as a potent, independent predictor of 5-year all-cause mortality in this cohort.
Aims:
Sleep-disordered breathing (SDB) is common among cardiac patients, but its role as an independent risk predictor after myocardial infarction (MI) is unclear. SDB causes cyclic variation of heart rate (CVHR). The aim of this study was to score Holter ECGs of a large cohort of MI survivors for SDB-related CVHR to investigate its value for mortality prediction.
Methods:
A total of 1590 survivors of acute MI in sinus rhythm were prospectively enrolled and followed for 5-year all-cause mortality. Heart rate (HR) tachograms were generated from nocturnal (00:00-06.00 am) segments of Holter ECGs, and the minutes with CVHR were quantified by a previously developed algorithm. According to a pre-specified cutpoint, SDB was assumed if CVHR was present during ≥72 min.
Results:
Seventy-seven patients (4.8%) had flat HR tachograms which prohibited analysis for SDB. Of the remaining 1513 patients, 584 (38.6%) were classified as having SDB. Mortality rates in groups stratified according to ECG-derived SDB did not differ significantly. Taken as a continuous variable, low CVHR duration was associated with increased mortality.The mortality of patients with flat HR tachograms was significantly increased, even after adjustment for age, sex, LVEF, GRACE score and diabetes mellitus. Mortality prediction by a flat HR tachogram was also independent of heart rate variability (HRV), heart rate turbulence (HRT), and deceleration capacity (DC).
Conclusion:
In Holter ECG recordings of survivors of acute MI, signs suggestive of SDB were frequently present, but not associated with mortality. A flat nocturnal HR tachogram was a strong, independent predictor of 5-year all-cause mortality.
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