Hindawi
Anesthesiology Research and Practice
Volume 2018, Article ID 5912726, 5 pages
https://doi.org/10.1155/2018/5912726
Research Article
Comparison of Preoperative Assessment of Patient’s Metabolic
Equivalents (METs) Estimated from History versus Measured by
Exercise Cardiac Stress Testing
Adam S. Weinstein ,1 Martin I. Sigurdsson,2 and Angela M. Bader1
1Department of Anesthesiology, Perioperative and Pain Medicine Brigham and Women’s Hospital, 75 Francis Street, CWN-L1,
Boston, MA 02115, USA
2Department of Anesthesiology, Duke University, 2301 Erwin Road, Durham, NC 027701, USA
Correspondence should be addressed to Adam S. Weinstein; asweinstein@bwh.harvard.edu
Received 5 May 2018; Revised 29 July 2018; Accepted 12 August 2018; Published 3 September 2018
Academic Editor: Michael Frass
Copyright © 2018 Adam S. Weinstein et al. )is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Background. Preoperative anesthetic evaluations of patients before surgery traditionally involves assessment of a patient’s
functional capacity to estimate perioperative risk of cardiovascular complications and need for further workup.)is is typically
done by inquiring about the patient’s physical activity, with the goal of providing an estimate of the metabolic equivalents
(METs) that the patient can perform without signs of myocardial ischemia or cardiac failure. We sought to compare estimates
of patients’ METs between preoperative assessment by medical history with quantified assessment of METs via the exercise
cardiac stress test. Methods. A single-center retrospective chart review from 12/1/2005 to 5/31/2015 was performed on 492
patients who had preoperative evaluations with a cardiac stress test ordered by a perioperative anesthesiologist. Of those, a total
of 170 charts were identified as having a preoperative evaluation note and an exercise cardiac stress test. )e METs of the
patient estimated by history and the METs quantified by the exercise cardiac stress test were compared using a Bland–Altman
plot and Cohen’s kappa. Results. Exercise cardiac stress test quantified METs were on average 3.3 METS higher than the METs
estimated by the preoperative evaluation history. Only 9% of patients had lower METs quantified by the cardiac stress test than
by history. Conclusions. )e METs of a patient estimated by preoperative history often underestimates the METs measured by
exercise stress testing. )is demonstrates that the preoperative assessments of patients’ METs are often conservative which errs
on the side of patient safety as it lowers the threshold for deciding to order further cardiac stress testing for screening for
ischemia or cardiac failure.
1. Background querying them for a description of their physical activities
and using activity scales, which correlates a physical activity
One metabolic equivalent (MET) is defined as the basal with a quantified number of METs [2–4]. )is assessment
oxygen consumption of a 40-year-old 70 kg man [1]. )e provides an estimate of a patient’s METs that is assumed to
maximum amount of metabolic work that an individual can correspond to a formal quantitative measurement of METs
perform can be described in METunits and this corresponds performed during a cardiac exercise stress test.
to overall cardiovascular fitness. )ese measurements have It is well known that patients with low METs are at
been utilized in preoperative assessments of patients where increased risk for perioperative morbidity and mortality
a patient’s functional capacity is described in METs and for [1, 2, 5, 6]. An accurate preoperative assessment of a patient’s
risk stratification for perioperative complications for pa- METs is important. If a patient cannot perform four METs,
tients undergoing noncardiac surgical procedures. Tradi- this could prompt further cardiac workup by the Stepwise
tionally, a patient’s maximum METs are quantified by Approach to Perioperative Cardiac Assessment Treatment
2 Anesthesiology Research and Practice
algorithm from the ACC/AHA Guidelines on Perioperative Table 1: Activities and their MET equivalents.
Cardiovascular Evaluation and Management of Patients METs Activity
Undergoing Noncardiac Surgery, because these patients
have increased postoperative complications [1]. Previous 1 Eating, getting dressed, working at a desk2 Showering, walking down eight steps
studies have focused on quantifying physical activities with 3 Walking on a flat surface for one or two blocks
quantified METs and correlating the METs to outcomes. )e Raking leaves, weeding or pushing a power mower,
focus of this study was the accuracy of the patient’s METs 4 walking up two flights of stairs
obtained by history in the anesthesia preoperative
5 Walking four miles per hour, social dancing, washingevaluation. a car
)erefore, we performed a single-center retrospective 6 Nine holes of golf carrying clubs, heavy carpentry
study over a ten-year period to examine the accuracy of using a push mower
anesthesiologists’ assessments of patient’s METs in the an- 7 Digging, spading soil, singles tennis, carrying 60
esthesia preoperative evaluation by comparing the pre- pounds
operative metabolic equivalents (METs) estimated from 8 Moving heavy furniture, jogging slowly, rapidly
history to the formally quantified METs during exercise climbing stairs, carrying 20 pounds upstairsBicycling at a moderate pace, sawing wood, slow
cardiac stress testing. 9 jumping rope
10 Brisk swimming, bicycling uphill, walking briskly,uphill jogs 6mph
2. Methods 11 Cross-country skiing, full-court basketball
12 Running continuously at 8mph
)e Brigham and Women’s Hospital (BWH) Institutional
Review Board (IRB) granted approval for the chart review
and waived individual consent. BWH uses the computer 3. Results
software program Precipio to order cardiac stress tests.
Using this software, we identified patients that underwent A total of 492 cardiac stress tests (one per patient) ordered by
cardiac stress tests ordered by an anesthesiologist at the an anesthesiologist at the BWH preoperative evaluation
BWH preoperative evaluation clinic from 12/1/2005 to clinic from 12/1/2005 to 5/31/2015 were identified. For 124
5/31/2015. Clinical data were extracted from the medical of the cardiac stress tests ordered, the accompanying pre-
charts in a de-identified manner and stored in an encrypted operative evaluation clinic visit notes were unobtainable or
and password protected excel spreadsheet that was created incomplete and were not analyzed for indication. At the
specifically for this study. study’s institution, the transition in 2015 from paper-based
Medical charts with patients undergoing cardiac stress medical records to electronic medical records resulted in
tests without an available preoperative anesthesia evaluation a loss of some original paper-based notes and some pre-
note (N � 96) or an incomplete anesthesia evaluation note operative evaluation clinic visit notes not obtainable either
(N � 28) were excluded. )e types of cardiac stress tests, due to them not ever being scanned in, incompletely scanned
exercise or nonexercise, were assessed. For those patients in, or misclassified as a different note type in the electronic
that had exercise cardiac stress tests (N � 170), we noted the medical record. )e remaining 368 cardiac stress tests were
METs of the patient estimated by history and the METs analyzed, and of those, 198 were identified as nonexercise
quantified by the exercise cardiac stress test following the cardiac stress tests as the cardiac stress test modality, leaving
visit. Exercise cardiac stress tests at BWH use the Bruce 170 charts for final analysis (Figure 1).
Protocol for quantification of METs. During preoperative )e patient demographics are shown in Table 2.
assessments at the BWH preoperative evaluation clinic, the Mean and median estimated METs by history were 4.9±
METs of a patient are estimated by history using the BWH 1.6 and 5 respectively, and mean and median measured
preoperative evaluation clinic METs Table (Table 1), which METs by the cardiac stress test were 8.3± 3.0 and 7.8, re-
gives examples of physical activities and their MET equiv- spectively. Although there was a modest correlation between
alents based on known standards. the two measurements (Spearman’s rho 0.37, p< 0.001), the
)e two METs assessments were compared using agreement between the two methods was generally poor
a Bland–Altman plot and by calculating a Spearman’s (Figure 2).
correlation. Furthermore, distribution of METs values into )e exercise cardiac stress test measured METs was on
categories of poor (less than 4METs), moderate (4–6METs), average 3.3 METs higher than the METs estimated from the
good (7–10 METs), and excellent (10 or higher METs) was preoperative evaluation clinic history. Only 16 (9%) patients
compared between the two assessments using Cohen’s had lower METs quantified by exercise cardiac stress test
kappa. Calculations were done in R (version 3.0, )e R than estimated by history. )e agreement between the two
foundation, Austria), and a p value< 0.05 was considered methods compared between patient groups of poor (less
significant. Comparison was repeated after excluding all than 4 METs), moderate (4–6 METs), good (7–10 METs),
patients that had an estimated MET by history of four and excellent (10 or higher METs) functional capacity was
(N � 53) to eliminate error from inadequate full assessment very poor (Cohen’s kappa 0.02, p � 0.446). Of the 170
of a patients full MET potential since 4 METs is a decision patients, the categorization of the patients’ METs by history
point in the ACC/AHA Guidelines. and exercise cardiac stress test into poor, moderate, good, or
Anesthesiology Research and Practice 3
Table 2: Patient demographics.
Cardiac stress tests ordered
492 Patient Demographics Mean (SD)/N(%)
Age 61± 11
Male gender 75 (44)
Excluded (N = 124) Type of surgery or procedure N (%)
unable to locate or General 51 (30)
incomplete Gastroenterology 1 (1)
preoperative Gynecology 30 (18)
evaluation clinic note Neurosurgery 8 (5)
Orthopedic 14 (8)
Otolaryngology 15 (9)
)oracic 22 (13)
Excluded (N = 198) Urology 26 (15)
cardiac stress test was Vascular 3 (2)
a non-exercise cardiac Indication for stress test N (%)
stress test ECG findings warranted stress test 99 (58)
Chest pain 37 (22)
METs less than 4 15 (9)
Stress test recommended by other medical
service 11 (6)
Charts analyzed
170 Other 8 (5)
Figure 1: Flow diagram of the charts analyzed and excluded.
15
excellent agreed for 38 (22%) of the patients. 124 (73%) 10
patients had a higher functional capacity grouping by 5
measured METs by exercise cardiac stress test than METs 0
quantified by history. Only 8 (5%) patients had a lower
functional capacity grouping by measured METs by exercise –5
cardiac stress test than METs estimated by history. In ad-
dition, only 7 (4%) patients had measured METs by the –15
exercise cardiac stress test of less than 4 and METs estimated 0 5 10 15
by history of greater than 4. Repeating the analysis but Average (METs)
excluding patients with a preoperative assessment visit note
that estimated 4 METs by history revealed similar results Figure 2: Bland–Altman plot of METs estimated from historyversus measured by exercise cardiac stress testing.
(data not shown).
4. Discussion of his or her exercise capacity. Furthermore, we could not
adjust for the practice of some preoperative clinicians to
We performed a single-center retrospective study of 170 document 4METs even if the patient is able to achieve higher
charts over a 10-year period comparing the preoperative METs. To help control for the latter limitation, we excluded
METs estimated from history to METs quantified during patients whose METs obtained by preoperative history at the
exercise cardiac stress testing.We found that, on average, the preoperative evaluation visit were documented as 4. Using
METS measured by the preoperative exercise cardiac stress this subset, the average METS measured by the preoperative
test was 3.3 METs higher than the METs estimated by exercise cardiac stress was still 3.3 METs higher than the
preoperative history at the preoperative evaluation clinic METs estimated by preoperative history at the preoperative
visit. )e Bland–Altman plot also demonstrates that gen- evaluation clinic visit.
erally the METs estimated by history are less than the METs Another limitation is that the indication for cardiac
measured by the exercise cardiac stress test with increasing stress testing is not random.)ere are many reasons to order
dispersion the higher the MET capacity of the patient. a cardiac stress test preoperatively, which is a vast topic of its
)ere are limitations to this study. )e assessment of own and outside the scope of this article. Looking at the table
METs was only semi-structured, meaning the clinician in- for the indications (Table 2) for which clinicians in this study
terviewer was provided a list of example activities and their ordered cardiac stress tests (METs< 4, ECG findings, chest
associated METs, but the recorded assessment was at the pain, and other), it is evident that the indications are car-
discretion of the clinician. Since this was a retrospective diovascular related. In addition, the inability to perform 4
study, we were unable to control for variables such as the METs or if it unknown whether 4 METs can be performed is
ability of the preoperative physician to adequately ascertain a strong indication for ordering a cardiac stress test if other
the patient’s METs from history and the patient’s knowledge criteria are met. An alternate perspective on this information
Difference (METs)
4 Anesthesiology Research and Practice
is that a patient who’s METs is greater than four, or exercises clearly is a difference in the preoperative estimate of METs
and knows their activity level well, is less likely to get between the exercise and nonexercise stress test patients.)e
a preoperative cardiac stress test. A reasonable assumption average METs estimated by history of patients who had an
can be made that patients who had cardiac stress tests or- exercise cardiac stress test compared with those who had
dered compared with those who did not are more likely to a nonexercise cardiac stress test were 4.9 and 3.6, re-
have cardiovascular pathologies and be less fit. spectively. In addition, the percentage of patients whose
)ere are published recommendations and appropriate METs estimated by history were less than 4 who had an
use criteria for specific types of cardiac stress tests [7–10]; exercise cardiac stress test compared with those who had
however, there is no consensus or recommendation about a nonexercise cardiac stress test were 15% and 49%, re-
which the modality of cardiac stress test to choose pre- spectively. )is difference in patients who had an exercise
operatively. )is decision is up to the discretion of the versus nonexercise cardiac stress test could be a limitation of
ordering clinician. )ere are multiple reasons why exercise this study. It can be inferred that clinicians in this study
versus nonexercise cardiac stress testing may have been favored nonexercise cardiac stress tests in patients with a low
chosen by the ordering clinician which were uncontrollable preoperative estimate of METs.
since the study is retrospective. )is may have led to a se- Furthermore, this study was a single-center study. While
lection bias in the study since patient-specific factors likely the BWH preoperative evaluation clinic is a high-volume
influenced the ordering clinician’s choice between an ex- clinic that sees over 25,000 patients a year and has been in
ercise and nonexercise cardiac stress test creating differences place for a relatively long time, this study examines only
in the two patient populations. )ese differences may derive a single institution’s clinicians. )erefore, our findings
from the following: First, a proportion of preoperative cannot be readily generalized to all preoperative
cardiac stress tests are a result of the Stepwise Approach to anesthesiologists.
Perioperative Cardiac Assessment Treatment algorithm Last, the evaluation of METs of a patient using known
from the ACC/AHA Guidelines on Perioperative Cardio- standards of activities has some limitations. While published
vascular Evaluation and Management of Patients Un- standards of METs of specific activities have been validated,
dergoing Noncardiac Surgery [1]. Although these guidelines the most well known being the Duke Activity Scale Index,
have evolved from 2002 to 2014, the ability of a patient to the estimation of METs by history relies on the ability of the
perform 4 METs has remained an important decision point clinician to adequately assess the patient [3, 12]. )e ability
in the stepwise algorithm for cardiac assessment. )e in- of a patient to know their activity levels and the clinician to
ability to perform 4 METs or if it unknown whether 4 METs accurately obtain that information is the challenge. Less
can be performed is a strong indication for ordering a car- likely is a recalibration of the validated instrument tool
diac stress test if other criteria are met. In these patients, the needed, but rather a reassessment of a clinician’s ability to
most recent ACC/AHA Guidelines (2014) recommends get an accurate functional assessment from a patient’s
specifically pharmacologic (nonexercise) stress testing, history of activities.
which pertains to only a small portion of this study (since the
ACC/AHA Guidelines were updated in December 2014 and 5. Conclusions
this retrospective study ended in May 2015). Prior to the
2014 Guidelines, the decision of exercise versus the non- In summary, the METs of a patient estimated by pre-
exercise cardiac stress test was up to the ordering clinician. operative history is conservatively assessed and often un-
)us, from December 2014 to May 2015 there is a bias for derestimates the METs measured by exercise cardiac stress
more pharmacologic stress tests in patients whose pre- testing. A conservative estimate of a patients METs lowers
operative estimate of METS is 4 or less or unknown. Second, the threshold for ordering preoperative cardiac stress tests to
for clinical scenarios not specifically addressed by the assess for underlying ischemia, which is a known risk for
Stepwise Approach to Perioperative Cardiac Assessment perioperative complications.
Treatment algorithm from the updated 2014 ACC/AHA
Guidelines, the decision on exercise versus nonexercise Data Availability
cardiac stress test is up to the clinician. Examples of this
include patients with a history of atypical chest pain pre- )e datasets used and/or analyzed during the current study
operatively or concerning ECG findings on a preoperative are not publicly available due to their current use on other
ECG. From these considerations there may be selection bias research projects but are available from the corresponding
for a nonexercise versus exercise cardiac stress test based on author on reasonable request.
the patient’s history which is frequently dictated by whether
the patient has physical or orthopedic commodities that Conflicts of Interest
limit them from exercising. A preoperative assessment of
low METs due to a cardiovascular limitation rather than an )e authors declare that they have no conflicts of interest.
orthopedic limitation does not necessitate a nonexercise
cardiac stress test. Typically, all that is required for the References
patient to achieve a satisfactory workload, which can be [1] L. A. Fleisher, K. E. Fleischmann, A. D. Auerbach et al., “2014
defined by many variables, is to achieve 85% of the age ACC/AHA guideline on perioperative cardiovascular evalu-
predicted maximum heart rate [11]. In this study there ation and management of patients undergoing noncardiac
Anesthesiology Research and Practice 5
surgery: a report of the American College of Cardiology/ [11] R. J. Gibbons, G. J. Balady, J. W. Beasley et al., “ACC/AHA
American Heart Association task force on practice guide- guidelines for exercise testing: executive summary. A report of
lines,” Circulation, vol. 130, no. 24, pp. e278–e333, 2014. the American College of Cardiology/American Heart Asso-
[2] D. F. Reilly, M. J. McNeely, D. Doerner et al., “Self-reported ciation task force on practice guidelines (committee on ex-
exercise tolerance and the risk of serious perioperative ercise testing),” Circulation, vol. 96, no. 1, pp. 345–354, 1997.
complications,” Archives of Internal Medicine, vol. 159, no. 18, [12] C. N. B. Merz, M. Olson, S. McGorray et al., “Physical activity
pp. 2185–2192, 1999. and functional capacity measurement in women: a report
[3] M. A. Hlatky, R. E. Boineau, M. B. Higginbotham et al., “A from the NHLBI-sponsoredWISE study,” Journal of Women’s
brief self-administered questionnaire to determine functional Health and Gender-Based Medicine, vol. 9, no. 7, pp. 769–777,
capacity (the duke activity status index),” American Journal of 2000.
Cardiology, vol. 64, no. 10, pp. 651–654, 1989.
[4] L. Goldman, B. Hashimoto, E. F. Cook, and A. Loscalzo,
“Comparative reproducibility and validity of systems for
assessing cardiovascular functional class: advantages of a new
specific activity scale,” Circulation, vol. 64, no. 6, pp. 1227–
1234, 1981.
[5] A. Tsiouris, H. M. Horst, G. Paone, A. Hodari, M. Eichenhorn,
and I. Rubinfeld, “Preoperative risk stratification for thoracic
surgery using the American College of Surgeons National
Surgical Quality Improvement Program data set: functional
status predicts morbidity and mortality,” Journal of Surgical
Research, vol. 177, no. 1, pp. 1–6, 2012.
[6] S. Goswami, J. E. Brady, D. A. Jordan, and G. Li, “Intra-
operative cardiac arrests in adults undergoing noncardiac
surgery: incidence, risk factors, and survival outcome,” An-
esthesiology, vol. 117, no. 5, pp. 1018–1026, 2012.
[7] R. J. Gibbons, G. J. Balady, J. T. Bricker et al., “ACC/AHA
2002 guideline update for exercise testing: summary article.
a report of the American College of Cardiology/American
Heart Association task force on practice guidelines (com-
mittee to update the 1997 exercise testing guidelines),” Journal
of the American College of Cardiology, vol. 40, no. 8,
pp. 1531–1540, 2002.
[8] R. C. Hendel, D. S. Berman, M. F. Di Carli et al., “ACCF/
ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 appropriate
use criteria for cardiac radionuclide imaging: a report of the
American College of Cardiology Foundation appropriate use
criteria task force, the American Society of Nuclear Cardi-
ology, the American College of Radiology, the American
Heart Association, the American Society of Echocardiogra-
phy, the Society of Cardiovascular Computed Tomography,
the Society for Cardiovascular Magnetic Resonance, and the
Society of Nuclear Medicine,” Journal of the American College
of Cardiology, vol. 53, no. 23, pp. 2201–2229, 2009.
[9] P. S. Douglas, M. J. Garcia, D. E. Haines et al., “ACCF/ASE/
AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011
appropriate use criteria for echocardiography. a report of the
American College of Cardiology Foundation appropriate use
criteria task force, American Society of Echocardiography,
American Heart Association, American Society of Nuclear
Cardiology, Heart Failure Society of America, Heart Rhythm
Society, Society for Cardiovascular Angiography and In-
terventions, Society of Critical Care Medicine, Society of
Cardiovascular Computed Tomography, and Society for
Cardiovascular Magnetic Resonance endorsed by the
American College of Chest Physicians,” Journal of the
American Society of Echocardiography, vol. 24, no. 3,
pp. 229–267, 2011.
[10] P. A. Pellikka, S. F. Nagueh, A. A. Elhendy, C. A. Kuehl, and
S. G. Sawada, “American Society of Echocardiography rec-
ommendations for performance, interpretation, and appli-
cation of stress echocardiography,” Journal of the American
Society of Echocardiography, vol. 20, no. 9, pp. 1021–1041,
2007.
MEDIATORS
of
INFLAMMATION
The Scientific Gastroenterology Journal of
World Journal Research and Practice Diabetes Research Disease Markers
Hindawi
Hindawi Publishing Corporation Hindawi www.hindawi.com Volume 2018 Hindawi Hindawi
hwtwtpw:/./hwinwdwaw.hii.ncodmawi.com Volume 20183 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018
Journal of International Journal of
Immunology Research Endocrinology
Hindawi Hindawi
www.hindawi.com Volume 2018 www.hindawi.com Volume 2018
Submit your manuscripts at
www.hindawi.com
BioMed 
PPAR Research Research International
Hindawi Hindawi
www.hindawi.com Volume 2018 www.hindawi.com Volume 2018
Journal of
Obesity
Evidence-Based 
Journal of Stem Cells Complementary and Journal of
Ophthalmology International Alternative Medicine Oncology
Hindawi Hindawi Hindawi Hindawi Hindawi
www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2013
Parkinson’s 
Disease
 Computational and  
Mathematical Methods Behavioural AIDS Oxidative Medicine and 
in Medicine Neurology Research and Treatment Cellular Longevity
Hindawi Hindawi Hindawi Hindawi Hindawi
www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018