Fitness and Mortality Outcomes Associated With Supramaximal Peak Heart Rate on Treadmill Exercise Stress Testing

Inability to reach age-predicted peak heart rate (APPHR) on treadmill exercise testing (TMET) is associated with lower fitness and increased mortality. The significance of a "supramaximal" heart rate (≥105% of APPHR) is poorly understood; as such, we sought to investigate this relationship. We queried the Mayo Stress database from 1993 to 2010 for patients >30 years old without cardiovascular disease and not on antichronotropic therapy. Patients were stratified into groups based on APPHR: <75%, 75% to 84%, 85% to 94%, 95% to 104%, and ≥105%, with 105% to 114% and ≥115% subgroups. Functional aerobic capacity (FAC) was assessed by ANOVA and all-cause mortality by cox hazard regression; we adjusted for confounders. In total, 18,961 patients were included; 1150 (6.1%) died. 2,144 (11.3%) of patients achieved submaximal APPHR (<85%), 2,917 achieved supramaximal APPHR (≥105%). Patients with submaximal APPHR had significantly lower FAC: 76.4% (p <0.0001) [<75%], 83.5% (p <0.0001) [≥75% to <85%]. Those with supramaximal APPHR had significantly higher FAC: 102.0% (p <0.0001). Patients with submaximal APPHR had significantly higher mortality risks: <75% (adjusted HR 2.36 [1.83 to 3.04], p <0.0001) and ≥75 to <85% (adjusted HR 1.93 [1.62 to 2.31], p <0.0001). Those with supramaximal APPHR, after adjustment for cardiac risk factors and resting heart rate, had significantly lower mortality risk (adjusted HR 0.83 [0.70 to 0.99], p = 0.0414). In conclusion, supramaximal heart rate on TMET was associated with significantly higher FAC and lower all-cause mortality risk.