Prognostic Contribution of Exercise Capacity, Heart Rate Recovery, Chronotropic Incompetence, and Myocardial Perfusion Single-Photon Emission Computerized Tomography in the Prediction of Cardiac Death and All-Cause Mortality.
Chronotropic incompetence, measured by the percentage (%) of heart rate (HR) reserve achieved (%HR reserve), abnormal HR recovery, reduced exercise capacity (EC), and myocardial perfusion single-photon emission computerized tomography (SPECT MPS) abnormalities are known predictors of all-cause mortality (ACM) and cardiac death (CD). The aim of this study was to determine if EC, %HR reserve, and HR recovery add incremental value to MPS in the prediction of ACM and CD. A total of 11,218 patients without valvular disease and not on β blockers underwent symptom-limited exercise MPS. %HR reserve was (peak HR - rest HR)/(220 - age - rest HR) × 100, with %HR reserve <80 defined as low. HR recovery was peak HR - recovery HR. An HR recovery <22 beats/min at 2 minutes after peak exercise was considered abnormal. Poor EC was defined as exercise duration ≤6 minutes (7 metabolic equivalents). Summed stress scores (SSSs) were calculated using a 20-segment, 5-point MPS model. Statistical analysis was performed using Cox regression models. There were 445 deaths (148 CD) during a mean follow-up of 3.2 ± 2.5 years. In multivariate analysis, the independent predictors of ACM were age, χ(2) = 154.81; EC, χ(2) = 74.00; SSS, χ(2) = 32.99; %HR reserve, χ(2) = 24.74; abnormal electrocardiogram at rest, χ(2) = 23.13; HR recovery, χ(2) = 18.45; diabetes, χ(2) = 17.75; and previous coronary artery disease, χ(2) = 11.85 (p ≤0.0006). The independent predictors of CD were SSS, χ(2) = 54.25; EC, χ(2) = 49.34; age, χ(2) = 46.45; abnormal electrocardiogram at rest, χ(2) = 30.60; previous coronary artery disease, χ(2) = 20.69; Duke treadmill score, χ(2) = 19.50; %HR reserve, χ(2) = 11.43; diabetes, χ(2) = 10.23 (all p ≤0.0014); and HR recovery, χ(2) = 5.30 (p = 0.0214). The exercise variables showed increases in Harrell's C static and net improvement reclassification, with EC showing the strongest incremental improvement in predicting ACM and CD (respective C-index 76.5% and 83.3% and net reclassification index 0.3201 and 0.4996). In conclusion, EC, %HR reserve, and HR recovery are independent predictors of ACM and CD and add incremental prognostic value to extent and severity of MPS.
Sulpizio Cardiovascular Center, University of California, San Diego, La Jolla, California.
Boris
B
Arbit
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
Babak
B
Azarbal
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
Sean W
SW
Hayes
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
Heidi
H
Gransar
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
Guido
G
Germano
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
John D
JD
Friedman
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California.
Louise
L
Thomson
Cedars-Sinai Heart Institute, Cedars-Sinai, Los Angeles, California. Electronic address: Daniel.Berman@cshs.org.
Daniel S
DS
Berman
D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000503:physiopathology; D002423:Cause of Death; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D011379:Prognosis; D015899:Tomography, Emission-Computed, Single-Photon