Exercise heart rate gradient: a novel index to predict all-cause mortality.
BACKGROUND
Although substantial evidence relates reduced exercise heart rate (HR) reserve and recovery to a higher risk of all-cause mortality, a combined indicator of these variables has not been explored. Our aim was to combine HR reserve and recovery into a single index and to assess its utility to predict all-cause mortality.


METHODS
Retrospective cohort analysis.


METHODS
Participants were 1476 subjects (937 males) aged between 41 and 79 years who completed a maximal cycle cardiopulmonary exercise test while not using medication with negative chronotropic effects or having an implantable cardiac pacemaker. HR reserve (HR maximum - HR resting) and recovery (HR maximum - HR at 1-min post exercise) were calculated and divided into quintiles. Quintile rankings were summed yielding an exercise HR gradient (EHRG) ranging from 2 to 10, reflecting the magnitude of on- and off-HR transients to exercise. Survival analyses were undertaken using EHRG scores and HR reserve and recovery in the lowest quintiles (Q1).


RESULTS
During a mean follow up of 7.3 years, 44 participants died (3.1%). There was an inverse trend for EHRG scores and death rate (p < 0.05) that increased from 1.2% to 13.5%, respectively, for scores 10 and 2. An EHRG score of 2 was a better predictor of all-cause mortality than either Q1 for HR reserve (<80 bpm) or HR recovery alone (<27 bpm): age-adjusted hazard ratios: 3.53 (p = 0.011), 2.52 (p < 0.05), and 2.57 (p < 0.05), respectively.


CONCLUSIONS
EHRG, a novel index combining HR reserve and HR recovery, is a better indicator of mortality risk than either response alone.
Gama Filho University, Rio de Janeiro, Brazil.
Carlos Vieira
CV
Duarte
Stanford University, Palo Alto, USA.
Jonathan
J
Myers
Gama Filho University, Rio de Janeiro, Brazil CLINIMEX, Rio de Janeiro, Brazil cgaraujo@iis.com.br.
Claudio Gil Soares
CG
de Araújo
D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality*; D002423:Cause of Death; D003326:Coronary Circulation; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006305:Health Status Indicators; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020127:Recovery of Function; D012189:Retrospective Studies
Cardiopulmonary exercise testing; chronotropic response; heart rate recovery; heart rate reserve