A patient with congenital heart disease who shows an abnormal cardiac response to exercise may show an increased risk of death.
Heart rate reserve is the increase in heart rate from resting levels to peak exercise levels.
heart rate reserve =
= (peak heart rate) - (resting heart rate)
Chronotropic incompetence is a blunted increase in heart rate during exercise.
chronotropic index =
= ((peak heart rate) - (resting heart rate)) / (220 - (age) - (resting heart rate))
Predictors of mortality:
(1) low peak heart rate
(2) low peak VO2 in mL per kg per min (not significant on multivariate analysis)
(3) low chronotropic index (below 0.80)
(4) low heart rate reserve
(5) NYHA functional class II or III
(6) antiarrhythmic therapy
(7) amiodarone therapy
(8) lower heart rate recovery at 3 and 5 minutes after exercise
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Heart Rate Reserve Group
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All-Cause Mortality at 1500 Days
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<= 51
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18%
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52 to 74
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7%
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>= 75
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2.5%
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