Background: Bluntedcyclicvariationofheartrate(CVHR),measuredasadecrease in CVHR amplitude (Acv), predicts mortality risk after acute myocardial infarction (AMI).However,AcvalsocanbereducedinmildsleepapneawithmildO 2 desaturation.WeinvestigatedwhetherAcv'spredictivepowerforpost-AMImortalitycould be improved by considering the effect of sleep apnea severity.
Methods: In24-hrECGin265,291participantsoftheAllostaticStateMappingbyAmbulatoryECGRepositoryproject,sleepapneaseveritywasestimatedbythefre-quencyofCVHR(Fcv)measuredbyanautomatedalgorithmforauto-correlatedwave detectionbyadaptivethreshold(ACAT).ThedistributionofAcvontheAcv-Fcvrelation map was modeled by percentile regression, and a function converting Acv into percentile value was developed. In the retrospective cohort of the Enhancing RecoveryinCoronaryHeartDisease(ENRICHD)study,consistingof673survivors and 44 non-survivors after AMI, the mortality predictive power of percentile Acv calculatedbythefunctionwascomparedwiththatofunadjustedAcv.Results: AmongtheALLSTARECGdata,lowAcvvaluesappearedmorelikelywhen Fcvwaslow.ThelogisticregressionanalysisformortalityintheENRICHDcohort showed c-statistics of 0.667 (SE, 0.041), 0.817 (0.035), and 0.843 (0.030) for Fcv, unadjusted Acv, and the percentile Acv, respectively. Compared with unadjusted Acv,thepercentileAcvshowedasignificantnetreclassificationimprovementof0.90 (95%CI,0.51-1.42).