The Prognostic Importance of Abnormal Heart Rate Recovery and Chronotropic Response Among Exercise Treadmill Test Patients

Thomas M. Maddox, MD, MSc, FACC; Colleen Ross, MS; P. Michael Ho, MD, PhD, FACC; Frederick A. Masoudi, MD, MSPH, FACC; David Magid, MD, MPH; Stacie L. Daugherty, MD, MSPH; Pam Peterson, MD, MSPH, FACC; John S. Rumsfeld, MD, PhD, FACC

Disclosures

Am Heart J. 2008;156(4):736-744. 

In This Article

Results

In our study cohort, 9,519 outpatients underwent ETT and were followed for a median length of time of 3.2 years. Of the patients, 12.2% (n = 1,163) had abnormal CR only, 19.8% (n = 1,889) had abnormal HRR only, and 11% (n = 1,038) had abnormal HRR and CR.

Patient demographics, ETT indications, clinical history, ETT characteristics, and DTS of the study cohort are listed in Table 1 In general, patients with abnormal HRR and/or CR (n = 4,090; 43% of cohort) were older, female, and had a higher prevalence of preexisting CAD, cardiac risk factors, and other comorbidities as compared to patients with normal HRR and CR. Approximately two thirds of the patients in the cohort (n = 6,130, 64.4%) were referred for ETT to evaluate chest pain. In addition, they were more likely to have higher risk treadmill results.

During the study period, 87 (1.6%) patients with normal HRR and CR, 34 (2.9%) patients with abnormal CR only, 70 (3.7%) patients with abnormal HRR only, and 70 (6.7%) patients with combined abnormal HRR and CR experienced the primary outcome of all-cause mortality or nonfatal MI ( Table 2 , Figure 1, log-rank P value < .0001). Similar relationships were seen among the individual outcomes of all-cause mortality and nonfatal MI ( Table 2 , Figures 2-3).

Unadjusted Kaplan-Meier curve of all-cause mortality or nonfatal MI by HRR and CR on ETT (n = 9,519). ______ indicates normal HRR and CR; __ __ __ __ __ __, abnormal CR only; __ __ __, abnormal HRR only; and +++++, abnormal HRR and CR.

Figure 2.

Unadjusted Kaplan-Meier curve of all-cause mortality by HRR and CR on ETT (n = 9,519). ______ indicates normal HRR and CR; __ __ __ __ __ __, abnormal CR only; __ __ __, abnormal HRR only; and +++++, abnormal HRR and CR.

Unadjusted Kaplan-Meier curve of nonfatal MI by HRR and CR on ETT (n = 9,519). ______ indicates normal HRR and CR; __ __ __ __ __ __, abnormal CR only; __ __ __, abnormal HRR only; and +++++, abnormal HRR and CR.

After multivariable adjustment, patients with abnormal HRR and CR had a significantly higher risk of the primary outcome (hazard ratio [HR] 1.90, 95% CI 1.35-2.69) as compared to patients with normal HRR and CR. Results of the multivariable model are displayed in Table 3 . Patients with abnormal HRR only had a significantly higher risk of the primary outcome (HR 1.41, 95% CI 1.02-1.97) than patients with normal HRR and CR (Figure 4). The point estimates of risk for the primary outcome increased in a stepwise fashion with abnormalities of HRR and CR. Similar findings were noted among the individual secondary outcomes. Inclusion of the HRR and CR parameters significantly added to the prognostic information of the DTS model (- 2 log likelihood value decreased from 4,591.99 to 4,544.73, P value < .05) and improved the overall model discrimination (c-statistic increased from 0.61 to 0.68) ( Table 4 ).

Adjusted outcomes by HRR and CR on ETT (n = 9,519).

After stratification of the cohort by DTS, 6,726 (70.7%) patients had low-risk DTS (≥5) and 2,793 (29.3%) patients had intermediate-risk DTS (4 to -10). Low-risk DTS patients with abnormal HRR and CR had a higher risk of the primary outcome (HR 2.59, 95% CI 1.55-4.32), as compared to low-risk DTS patients with normal HRR and CR (Figure 5). Low-risk DTS patients with abnormal HRR only had a significantly higher risk of the primary outcome (HR 1.6, 95% CI 1.01-2.51), as compared to low-risk DTS patients with normal HRR and CR. Similar findings were noted among the individual, secondary outcomes. Intermediate-risk DTS patients had no significant association between abnormalities of HRR or CR and either primary or secondary outcomes (Figure 6).

Adjusted outcomes by HRR and CR on ETT among patients with low-risk DTS (n = 6,726).

Adjusted outcomes by HRR and CR on ETT among patients with intermediate-risk DTS (n = 2,793).

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