85% of maximal age-predicted heart rate is not a valid endpoint for exercise treadmill testing

Exercise Stress Testing in Athletes

Exercise stress testing (EST) is indicated for diagnostic and prognostic purposes in the general population. In athletes, stress tests can also be useful to inform the risk of high-intensity training and competition, to assess athletic conditioning, and to refine training regimens. Many specific indications for EST are unique to athletes. Treadmill and cycle ergometer protocols each have their strengths and disadvantages; extensive protocol customization may be necessary to answer the clinical question at hand. A comprehensive understanding of the available tools for exercise testing, their strengths, and their limitations is crucial to providing cardiovascular care to athletic individuals.

HR Max Prediction Based on Age, Body Composition, Fitness Level, Testing Modality and Sex in Physically Active Population

Maximal heart rate (HRmax) is associated mostly with age, but age alone explains the variance in HRmax to a limited degree and may not be adequate to predict HRmax in certain groups. The present study was carried out on 3374 healthy Caucasian, Polish men and women, clients of a sports clinic, mostly sportspeople, with a mean age of 36.57 years, body mass 74.54 kg, maximum oxygen uptake (VO₂max, ml^∗kg^–1∗min^–1) 50.07. Cardiopulmonary exercise tests (CPET) were carried out on treadmills or cycle ergometers to evaluate HRmax and VO₂max. Linear, multiple linear, stepwise, Ridge and LASSO regression modeling were applied to establish the relationship between HRmax, age, fitness level, VO₂max, body mass, age, testing modality and body mass index (BMI). Mean HRmax predictions calculated with 5 previously published formulae were evaluated in subgroups created according to all variables. HRmax was univariately explained by a 202.5–0.53^∗age formula (R² = 19.18). The weak relationship may be explained by the similar age with small standard deviation (SD). Multiple linear regression, stepwise and LASSO yielded an R² of 0.224, while Ridge yielded R² 0.20. Previously published formulae were less precise in the more outlying groups of the studied population, overestimating HRmax in older age groups and underestimating in younger. The 202.5–0.53^∗age formula developed in the present study was the best in the studied population, yielding lowest mean errors in most groups, suggesting it could be used in more active individuals. Tanaka’s formula offers the second best overall prediction, while the 220-age formula yields remarkably high mean errors of up to 9 bpm. In conclusion, adding the studied variables in multiple regression models improves the accuracy of prediction only slightly over age alone and is unlikely to be useful in clinical practice.

Usefulness of the Duke Activity Status Index to Select an Optimal Cardiovascular Exercise Stress Test Protocol

Exercise testing represents the preferred stress modality for individuals undergoing evaluation of suspected myocardial ischemia. Patients with limited functional status may be unable to achieve an adequate exercise stress, thus influencing the diagnostic sensitivity of the results. The Duke Activity Status Index (DASI) is a clinically applicable tool to estimate exercise capacity. The purpose of the current study was to assess the utility of the DASI to identify patients unable to achieve an adequate exercise stress result. Patients referred for exercise stress testing were administered the DASI pre-exercise. Baseline characteristics and exercise variables were evaluated including DASI-metabolic equivalents (DASI-METs), peak METs, exercise time (ET), and %-predicted maximal heart rate (%PMHR). Criteria for determining adequate exercise stress was defined as ≥85%PMHR or ≥ 5-METs at peak exercise. In 608 cardiovascular stress tests performed during the study period; 314 were exercise stress. The median DASI-METs (8.4 [interquartile range; 6.7 to 9.9]) was associated with estimated peak exercise METs (R=0.50, p <0.001), ET (R=0.29, p <0.001), and %PMHR (R=0.19, p = 0.003). DASI-METs were different between those with < or ≥85%PMHR (7.9 [6.6-9.0] vs. 8.9 [7.1-9.9], P=0.025) and those with < or ≥5-METs (5.8 [4.6 to 6.6] versus 8.9 [7.3-9.9], p <0.001). Receiver operating characteristic curve analysis identified a DASI-MET threshold of ≤/>7.4 to optimally predict adequate exercise stress (sensitivity=93%, specificity=71%). In conclusion, the DASI correlates with peak METs, ET, and %PMHR among patients referred for exercise testing and can be used to identify patients with an increased likelihood of an inadequate stress test result.

[Negative result of exercise testing in patient with severe coronary artery disease]

The ECG stress test allows to determine possible presence of obstructive coronary atherosclerosis. The more severe the atherosclerotic lesion of coronary arteries the more likely a ST segment depression during the stress test. The article provides a description of a negative result of a stress test in a patient with multivessel coronary disease.

Comparison of Heart Rate Blood Pressure Product Versus Age-Predicted Maximum Heart Rate as Predictors of Cardiovascular Events During Exercise Stress Echocardiography

Exercise stress echocardiograms (ESEs) are a functional cardiovascular (CV) test typically used for the investigation of coronary artery disease. ESEs are often terminated at a predetermined age-predicted maximum heart rate (APMHR) to facilitate timely acquisition of ultrasound images at peak exercise. Although an APMHR of 85% is often used, this has not been validated as a suitable termination end point. Heart rate blood pressure product (HRBPP) as an established measure of myocardial work may provide a more reliable assessment of cardiac workload. The aim of this study was to assess maximal HRBPP (MHRBPP) and APMHR as markers of cardiac workload during ESE, using CV events at mean follow-up as the outcome variable. After exclusions, 712 patients being investigated for ischemic heart disease, performed an ESE to volitional fatigue using the standard Bruce protocol. Patient demographics and test data were collected and patients followed for 4.4 ± 2.1 years. Cut-points for MHRBPP (25,060; area under curve 0.77) and APMHR (93.8% and 97.9%; area under curve 0.71; p = 0.12 for difference) were established from receiver operating characteristic analysis. Those achieving an APMHR >85% but MHRBPP <25,060 had significantly more CV events than achieving an MHRBPP >25,060 regardless of APMHR (p <0.05). In conclusion, the current study demonstrates the superior prognostic power of MHRBPP over APMHR alone for the prediction of future CV events in patients performing an otherwise negative ESE for the detection of myocardial ischemia.

Exercise stress test in apparently healthy individuals - where to place the finish line? The Ferrari corporate wellness programme experience

AIMS

The aim of our study was to assess the clinical significance of the exercise stress testing endpoints, namely 85% of maximal theoretical heart rate (MTHR), metabolic equivalent of task, and rating of perceived exertion (RPE), and their relation to electrocardiographic (ECG) changes in a healthy adult population.

METHODS

A cross-sectional study was conducted on 408 males and 52 females (mean age 39.4 ± 8.6 years) who performed the maximal cycle ergometer exercise stress test until volitional exhaustion, reporting the RPE score at 85% of MTHR and at peak exercise. Metabolic equivalents of task were indirectly calculated from the maximum workload and compared with the predicted values. Sitting torso-lead ECG and blood pressure were recorded at rest, during exercise and during recovery.

RESULTS

Of 460 participants, 73% exceeded 85% of MTHR. The RPE score represented the overall most significant endpoint of exercise stress testing, with the median value of 17 at peak exercise. ECG events were detected in 23/124 (18.5%) who reached ≤ 85% of MTHR and in 61/336 (18.2%) who achieved >85% of MTHR ( p = 0.92). In the latter group, 54% of ECG changes occurred at < 85% of MTHR and 46% at > 85% of MTHR ( p = 0.51). If the exercise stress testing had been interrupted at ≤ 85% of MTHR, almost half of the ECG events would have remained undetected and 35% of the cardiovascular abnormalities observed at the diagnostic follow-up would have remained undiagnosed.

CONCLUSION

Terminating exercise stress testing before volitional exhaustion and an RPE score of 17 limits the test accuracy and reduces the possibility to detect cardiovascular abnormalities in apparently healthy adult populations.

Is downstream cardiac testing required in patients with reduced functional capacity and otherwise negative exercise stress test? A single center observational study

BACKGROUND

Exercise stress testing (EST) in patients with poor functional capacity measured by time on treadmill is typically deemed inconclusive and usually leads to further downstream testing. The aim of this study was firstly to evaluate the maximum rate pressure product (MRPP) during initial EST to assessthe need for follow-up testing; and secondly to investigate if MRPP is better than age predicted maximum heart rate (APMHR) for diagnostic outcome based on follow up cardiovascular (CV) events in patients with inconclusive EST due to poor functional capacity.

METHODS

From a total of 2761 tests performed, 236 tests were considered inconclusive due to poor functional capacity which were available for analysis. From receiver operating characteristic (ROC) analysis, a cut-off value for MRPP of 25000 was chosen using CV events as the outcome measure (sensitivity 97%, specificity 45%). Cases were then categorised into those with an MRPP > 25000 and < 25000.

RESULTS

Regardless of treadmill time, any patient attaining an MRPP > 25000 had no abnormal downstream testing or CV events at 2 years follow-up. On ROC analysis MRPP outperformed APMHR for sensitivity and specificity (area under curve 0.76 vs. 0.59, respectively).

CONCLUSIONS

The results suggest that regardless of functional capacity, individuals whose EST is terminated at maximal fatigue, with no electrocardiogram evidence or symptoms of myocardial ischemia and yields an MRPP > 25000, do not require further downstream testing. Furthermore, this group of patients, while not immune to future CV events, have significantly better outcomes than those not attaining a MRPP > 25000.

Assessment of Exercise Capacity and Oxygen Consumption Using a 6 min Stepper Test in Older Adults

It is often necessary to assess physical function in older adults to monitor disease progression, rehabilitation or decline in function with age. However, increasing frailty and poor balance that accompany aging are common barriers to exercise testing protocols. We investigated whether a 6-min stepper test (6MST) was acceptable to older adults and provided a measure of exercise capacity and a predicted value for peak aerobic capacity (VO_2max). 635 older adults from a tri-ethnic UK population-based cohort were screened to undertake a self-paced 6MST. Expired gas analysis, heart rate and blood pressure monitoring were carried out. A sub-set of 20 participants performed a second 6MST for assessment of reproducibility and a further sub-set of 10 performed the 6-min walk test as verification against a well-recognized and accepted self-paced exercise test. 518 (82%) participants met inclusion criteria and undertook the 6MST (299 men, mean age 71.2 ± 6.4). Step rate showed a strong positive correlation with measured VO₂ (r = 0.75, p < 0.001) and VO₂ was lower in women (male-female difference in VO₂ = 2.61 (95% confidence interval -3.6, -1.7) ml/min/kg; p < 0.001). 20 participants repeated a 6MST, step rate was higher in the second test but the predicted VO_2max showed good agreement (mean difference = 0.1 [3.72, 3.95] ml/min/kg). In 10 participants who completed a 6MST and a 6-min walk test there was a strong positive correlation between walking rate and step rate (r = 0.77; p < 0.009) and weaker positive correlations between the tests for measured VO₂ and peak heart rate. In conclusion, the 6MST is a convenient, acceptable method of assessing exercise capacity in older adults that allows VO_2max to be predicted reproducibly. The test shows good correlation between performance and measured physiological markers of performance and can detect the expected gender differences in measured VO₂. Furthermore, the 6MST results correlate with a previously verified and established self-paced exercise test.

ST-segment changes with exercise stress

The treadmill electrocardiogram (ECG) stress test is widely used to screen for obstructive coronary artery disease (CAD). The presence of STsegment changes, either depression or elevation, on the ECG during the treadmill test often suggests presence of CAD and warrants further management. We herein present three cases, with evidence of ischaemia on the treadmill ECG stress test. In addition, we discuss the use of the treadmill ECG stress test, including its indications, contraindications, reasons for termination and interpretation of the ST-segment changes, heart rate, as well as blood pressure responses to exercise.

Revisiting age-predicted maximal heart rate: Can it be used as a valid measure of effort?

INTRODUCTION

Despite high error ranges, age-predicted maximal heart rate (APMHR) is frequently used to gauge the achievement of adequate effort during an exercise test. The current analysis revisits this issue using the Fitness Registry and the Importance of Exercise: National Database (FRIEND Registry).

METHODS

A total of 4,796 (63% male) apparently healthy subjects underwent a maximal cardiopulmonary exercise test on a treadmill. The mean age, maximal heart rate (HR), and maximal aerobic capacity of the cohort were 43 ± 12 years, 178 ± 15 beats per minute, and 36.1 ± 10.6 mlO2 · kg(-1) · min(-1), respectively. All subjects reached or surpassed a peak respiratory exchange ratio of 1.10. A linear regression equation using age to predict maximal HR was validated in 3,796 subjects and cross-validated in the remaining 1,000 (randomly assigned).

RESULTS

The APMHR equation in the validation cohort was as follows: 209.3 - 0.72(age). The r value and standard error of estimate for this regression was 0.61 (P < .001) and 11.35 beats/min, respectively. A 1-sample t test revealed that the mean difference between actual maximal HR and APMHR was not significantly different from 0 (mean difference = 0.32, P = .43). However, Bland-Altman revealed high limits of agreement (upper 25.31 and lower -24.67) and a significant proportional bias.

DISCUSSION

The APMHR equation derived from this analysis included a large cohort of apparently healthy individuals with maximal exercise effort validated by the criterion standard (ie, peak respiratory exchange ratio). Using APMHR in this capacity should be discouraged, and new approaches to gauging an individual's exercise effort should be explored.

Diagnostic Value of the Updated Diamond and Forrester Score to Predict Coronary Artery Disease in Patients with Acute-Onset Chest Pain

OBJECTIVES

In the recently updated clinical guidelines from the European Society of Cardiology on the management of stable coronary artery disease (CAD), the updated Diamond Forrester score has been included as a pretest probability (PTP) score to select patients for further diagnostic testing. We investigated the validity of the new guidelines in a population of patients with acute-onset chest pain.

METHODS

We examined 527 consecutive patients with either an exercise-ECG stress test or single-photon emission computed tomography, and subsequently coronary computed tomography angiography (CCTA). We compared the diagnostic accuracy of PTP and stress testing assessed by the area under the receiver operating characteristic curve (AUC) to identify significant CAD, defined as at least 1 coronary artery branch with >70% diameter stenosis identified by CCTA.

RESULTS

The diagnostic accuracy of PTP was significantly higher than the stress test (AUC 0.80 vs. 0.69; p = 0.009), but the diagnostic accuracy of the combination of PTP and a stress test did not significantly increase when compared to PTP alone (AUC 0.86 vs. 0.80; p = 0.06).

CONCLUSIONS

PTP using the updated Diamond and Forrester Score is a very useful tool in risk-stratifying patients with acute-onset chest pain at a low-to-intermediate risk of having CAD. Adding a stress test to PTP does not appear to offer significant diagnostic benefit.

Measured maximal heart rates compared to commonly used age-based prediction equations in the Heritage Family Study

OBJECTIVE

The purpose of this study was to examine how well two commonly used age-based prediction equations for maximal heart rate (HRmax ) estimate the actual HRmax measured in Black and White adults from the HERITAGE Family Study.

METHODS

A total of 762 sedentary subjects (39% Black, 57% Females) from HERITAGE were included. HRmax was measured during maximal exercise tests using cycle ergometers. Age-based HRmax was predicted using the Fox (220-age) and Tanaka (208 - 0.7 × age) formulas.

RESULTS

The standard error of estimate (SEE) of predicted HRmax was 12.4 and 11.4 bpm for the Fox and Tanaka formulas, respectively, indicating a wide-spread of measured-HRmax values are compared to their age-predicted values. The SEE (shown as Fox/Tanaka) was higher in Blacks (14.4/13.1 bpm) and Males (12.6/11.7 bpm) compared to Whites (11.0/10.2 bpm) and Females (12.3/11.2 bpm) for both formulas. The SEE was higher in subjects above the BMI median (12.8/11.9 bpm) and below the fitness median (13.4/12.4 bpm) when compared to those below the BMI median (12.2/11.0 bpm) and above the fitness median (11.4/10.3) for both formulas.

CONCLUSION

Our findings show that based on the SEE, the prevailing age-based estimated HRmax equations do not precisely predict an individual's measured-HRmax .

Safety and feasibility of adjunctive regadenoson injection at peak exercise during exercise myocardial perfusion imaging: The Both Exercise and Regadenoson Stress Test (BERST) trial

BACKGROUND

The data existing in the literature regarding the safety of using regadenoson with symptom-limited exercise are limited, which motivated the authors to undertake this randomized study.

METHODS

We offered patients scheduled to undergo vasodilator stress nuclear myocardial perfusion imaging the opportunity to exercise instead. Patients who failed to reach target heart rate (THR) were randomized to (1) receive regadenoson at peak exercise or (2) stop exercise and receive regadenoson at rest. Patients who reached THR received a standard Tc-99m sestamibi injection with no regadenoson.

RESULTS

200 patients were included (66% male, mean age 52.5 ± 13.6). 125 patients (62%) reached THR with exercise alone. All stress protocols were well tolerated, and there were no significant adverse events. There were no statistically significant differences in the extent of perfusion abnormalities, image quality, or rate of referral to cardiac catheterization within 60 days between the groups. In fully adjusted logistic regression models, beta-blocker use and diabetes remained significant univariate predictors of failure to reach THR (OR 0.21, 95% CI 0.1-0.5, P < .0001, OR 0.34, 95% CI 0.2-0.7, P = .004, respectively).

CONCLUSIONS

A protocol combining regadenoson at peak exercise in patients unable to reach THR with exercise is feasible, well-tolerated, and yields comparable imaging results to a standard regadenoson injection at rest. In addition, pharmacologic stress testing may be over-ordered in current clinical practice, as patients referred for such testing were often able to exercise.

The prognostic significance of heart rate recovery is not dependent upon maximal effort in patients with heart failure

BACKGROUND

Heart rate recovery (HRR) has been observed to be a significant prognostic measure in patients with heart failure (HF). However, the prognostic value of HRR has not been examined in regard to the level of patient effort during exercise testing. Using the peak respiratory exchange ratio (RER) and a large multicenter HF database we examined the prognostic utility of HRR.

METHODS

Cardiopulmonary exercise testing (CPX) was performed in 806 HF patients who then underwent an active cool-down of at least 1 min. Peak oxygen consumption (VO2), ventilatory efficiency (VE/VCO2 slope), and peak RER were determined with subjects categorized into subgroups according to peak RER (<1.00, 1.00-1.09, ≥ 1.10). HRR was defined as the difference between heart rate at peak exercise and 1 min following test termination. Patients were followed for major cardiac events for up to four years post-CPX.

RESULTS

There were 163 major cardiac events (115 deaths, 20 left ventricular assist device implantations, and 28 transplantations) during the four year tracking period. Univariate Cox regression analysis results identified HRR as a significant (p<0.05) univariate predictor of adverse events regardless of the RER achieved. Multivariate Cox regression analysis in the overall group revealed that the VE/VCO2 slope was the strongest predictor of adverse events (chi-square: 110.9, p<0.001) with both HRR (residual chi-square: 16.7, p<0.001) and peak VO2 (residual chi-square: 10.4, p<0.01) adding significant prognostic value.

CONCLUSIONS

HRR after symptom-limited exercise testing performed at sub-maximal efforts using RER to categorize level of effort is as predictive as HRR after maximal effort in HF patients.

Safety and feasibility of regadenoson use for suboptimal heart rate response during symptom-limited standard Bruce exercise stress test

BACKGROUND

Regadenoson during exercise stress test (ETT) can provide maximal hyperemia for myocardial perfusion imaging (MPI), along with exercise information. Our aim was to study the feasibility and safety of regadenoson injection at peak ETT for submaximal heart rate (HR) response.

METHODS

Consecutive patients who underwent SPECT MPI with standard Bruce ETT or supine-regadenoson (Supine-Reg) were analyzed. ETT patients were grouped as ETT-Max [maximal HR > 0.85 * (220 - age), N = 1,522], ETT-Submax (submaximal HR no regadenoson, N = 504), ETT-Reg (submaximal HR and regadenoson, N = 211).

RESULTS

The HR during ETT was submaximal in 715 (32%) patients. Of these, 211 patients (30%) underwent ETT-Reg (mean exercise duration: 5.5 ± 2.5 minutes). ETT-Reg patients had a higher frequency of hypertension, diabetes, smoking and beta-blocker use, similar rest systolic blood pressure (SBP), but lower rest and peak HR and peak SBP compared to ETT-Max patients. There were no serious complications with regadenoson. Side effects (49% vs 6%, P < .0001) were fewer and aminophylline use was lower with ETT-Reg compared to Supine-Reg (0.5% vs 8.1%, P = .001).

CONCLUSIONS

Submaximal HR response to ETT is common. ETT-Reg is safe, feasible, and well-tolerated. ETT-Reg facilitates a diagnostic MPI with reporting of functional capacity, exercise ECG/hemodynamic changes and MPI at maximal hyperemia.

⁸²Rb PET myocardial perfusion imaging is superior to ⁹⁹mTc-labelled agent SPECT in patients with known or suspected coronary artery disease

PURPOSE

We compared the quality, interpretive confidence and interreader agreement between SPECT and PET myocardial perfusion imaging (MPI) in the same group of patients.

METHODS

The study group comprised 27 patients (age 55 ± 8.5 years, 12 men) with known or suspected coronary artery disease (CAD) who had undergone gated rest/stress MPI with (99m)Tc-labelled agent SPECT (with and without attenuation correction, AC), and subsequent clinical confirmation with (82)Rb PET. Three experienced readers blinded to the clinical information interpreted all MPI studies.

RESULTS

Interreader agreement was significantly superior for PET studies than for SPECT studies. Following consensus interpretation, the quality of 22 % of the non-AC SPECT studies, 33 % of the AC SPECT studies and 63 % of the PET studies was assessed as excellent or good (p = 0.016). Interpretations were definitely normal or abnormal in 7 % of non-AC SPECT studies, 30 % of AC SPECT studies and 85 % of PET studies (p = 0.046). In 13 patients who had received either invasive coronary angiography or CT angiography with no significant CAD, the true-positive rate for significant CAD was higher for PET, and the true-negative rate was equal for PET and AC SPECT, and lower for non-AC SPECT.

CONCLUSION

(82)Rb PET MPI, used as a confirmatory test after SPECT, offers improved image quality, interpretive confidence and interreader agreement.