NICE guideline focuses on diagnosis of acute chest pain to improve outcomes
BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c1670 (Published 24 March 2010) Cite this as: BMJ 2010;340:c1670
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I suspect that the ECG machine operator in the photograph
accompanying your news article works in a parallel NHS, as I note her to
be wearing both a wrist watch and a bracelet.
Competing interests:
None declared
Competing interests: No competing interests
NICE’s use of probability to assist in the diagnosis of chest pain is
to be welcomed[1,2]; but why stop with symptoms?
Since 1999 we have asked every person attending the Rapid Access
Chest Pain Clinic at Imperial College Healthcare NHS Trust (Hammersmith
Hospital) to complete a questionnaire[3] before being seen. From this and
from the 12 lead ECG, the probability of CAD (pCAD) is calculated[4]. All
those undergoing Bruce treadmill exercise testing also have their post-
exercise pCAD calculated using Bayes’ Theorem: where pre-exercise pCAD is
the prior probability and the sensitivities and specificities are obtained
from the maximum ST segment shift[5]. As NICE’s adaptation of reference 4
excludes the 12 lead ECG information, I have recalculated the pre- and
post-exercise pCAD of 5369 persons (5177 referred direct from primary
care) excluding the 12 lead ECG information.
Legend: the graph shows how post-exercise pCAD falls if the maximum
ST segment shift is less than 50 microvolts and how it increases if the ST
shift is more than 100 microvolts.
NICE recommends that chest pain management differs when pCAD
thresholds of 30% and 60% are crossed. The use of the post-exercise pCAD
would have changed the management of 1868 (34.8%) of these persons with
chest pain:
a) 549 persons had a pre-exercise pCAD > 60% and a post-exercise
pCAD <60%; 236 persons had a pre-exercise pCAD <60% and a post-
exercise pCAD > 60%
b) 1064 persons had a pre-exercise pCAD > 30% and a post-exercise
pCAD <30%; 194 persons had a pre-exercise pCAD <30% and a post-
exercise pCAD > 30%
Including ECG information in the derivation of the pre-exercise pCAD,
a similar result is obtained: the management of 1915 (35.7%) of these
persons is changed following exercise.
The results call into question NICE’s recommendation “Do not use
exercise ECG to diagnose or exclude stable angina for people without known
CAD”.
[1] Kmietowicz Z. NICE focuses on diagnosis to improve chest pain
outcomes. BMJ 2010;340:c1670. (27 March.)
[2] Chest pain of recent onset: Assessment and diagnosis of recent
onset chest pain or discomfort of suspected cardiac origin. NICE Clinical
Guideline 95, March 2010
[3] Joswig BC, Glover MU, Nelson DP, Handler JB, Henderson J.
Analysis of historical variables, risk factors and the resting
electrocardiogram as an aid in the clinical diagnosis of recurrent chest
pain. Comput Biol Med 1985;15:71-80
[4] Pryor DB, Shaw L, McCants CB et al. Value of the history and
physical in identifying patients at increased risk for coronary artery
disease. Ann Intern Med 1993;118:81–90
[5] Diamond GA, Forrester JS. Analysis of probability as an aid in
the clinical diagnosis of coronary-artery disease. NEJM 1979;300:1350-8
Thanks are due to the members of the ECG Team who entered the data
into the bespoke database
Peter J Bourdillon p.bourdillon@imperial.ac.uk
Competing interests:
None declared
Competing interests: No competing interests
The NICE guideline on the management of stable angina and acute
coronary
syndromes, now in preparation and mentioned in the News section, 1 will be
welcome. The importance of a prompt ECG for patients with possible heart
attacks was quoted in your report. It is therefore unfortunate that the
accompanying photograph showed markedly misplaced precordial electrodes.
V1 and V2 should be in the fourth intercostal space identified by using
the
sternal angle as a landmark for the second rib. Your illustration shows
them no
lower than the second intercostal space: a position that would give
diminutive
or absent r waves with a pattern likely spuriously to suggest the presence
of an
old anteroseptal infarct. Sadly, many electrocardiograms are taken with
precordial leads placed too high on the chest. The British Medical
Journal should
not help to perpetuate this important error.
1. NICE focuses on diagnosis to improve chest pain outcomes. BMJ
2010;340:c1670.
Competing interests:
None declared
Competing interests: No competing interests
Changes to QOF ?
NICE now states "If people have features of typical angina based on
clinical assessment and their estimated
likelihood of CAD is greater than 90% (see table 1), further diagnostic
investigation is unnecessary. Manage as angina." Before the GMS Quality
and Outcomes Framework ( QOF ) was introduced 5 years ago many patients
with stable angina were diagnosed clinically and only a proportion were
referred. Is NICE now agreeing that such outmoded practice was in fact
rational ?
One consequence of this new guideline, now that NICE has been lined
up to take over QOF rule-setting, will presumably be the rapid reduction
in referral for exercise-testing under IHD02.
Or maybe not. Perhaps the '&/or referral for specialist assessment '
will fill that particular void.
Competing interests:
I am a GP performing QOF
Competing interests: No competing interests