risk assessment of possible acute coronary syndrome without ST elevation (NSTEACS)

introduction

one of the major difficulties for clinicians is deciding which patients with possible cardiac ischaemic chest pain to refer for further investigation and which investigation to consider
the current approach is to allocate the patient to either high, intermediate or low risk category based on risk assessment scoring systems, the best of these appears to be the new HEART score although this is awaiting further validation
patients with high risk generally are then referred for coronary angiography
patients with intermediate risk generally are then referred for cardiac stress testing
patients with low risk may not need further investigation

risk assessment systems

TIMI risk score

a 7 point score for patients with acute coronary syndromes derived by summing the presence of each of these factors:
- age > 64
- more than 3 coronary risk factors
- prior coronary angiographic coronary obstruction
- ST-segment deviation
- more than 2 angina events within 24 hours
- use of aspirin within 7 days
- elevated levels of cardiac biomarkers (eg. troponin)

TIMI score¹⁾	14 day adverse cardiac event rate
0/1	4.7%
2	8.3%
3	13.2%
4	19.9%
5	26.2%
6/7	40.9%

GRACE risk score

based on a large unselected population of an international registry of the full spectrum of ACS patients
although based on simple measures such as age, heart rate, systolic BP, serum creatinine level, Killip class, presence of ST-depression, and elevated biomarkers, it requires a calculator to generate a score - see http://www.outcomes.org/grace

GRACE score	risk category	in-hospital deaths (%)	post-discharge deaths to 6 months (%)
< 109	low risk	<1	<3
109-140	intermediate risk	1-3	3-8
> 140	high risk	>3	>8

FRISC score

FRISC score for selection of patients for an early invasive treatment strategy in unstable coronary artery disease. Heart 2005;91:1047-1052
Uses seven factors:
- age > 70 years
- male sex
- diabetes
- previous MI
- ST depression
- raised troponin
- raised inflammatory markers (CRP or interleukin 6)
at 1 year follow up:
- invasive strategy in patients with score > 4 resulted in reduction in mortality from 15.4% to 5.2% (RR 0.34)
- invasive strategy in patients with score 3-4 resulted in reduction in mortality/MI from 15.7% to 10.8% (RR 0.69)
- invasive strategy in patients with score < 3 resulted in NO reduction in mortality or MI
at 5 years follow up:
- the benefit of the invasive strategy was confined to male patients, non-smokers, and patients with two or more risk indicators ²⁾

the HEART score

perhaps the best tool for ED patients as of 2014 as it outperforms the TIMI and GRACE scores³⁾
the HEART score

parameter	score 0	score 1	score 2
*History	slightly suspicious	mod. suspicious	highly suspicious
*ECG	normal	non-specific repolarisation disturbance	significant ST depression
*Age	≤ 45 years	45 – 65 years	≥ 65 years
*Risk factors	no known factors	1-2 risk factors	> 2 risk factors
*Troponin	normal	1-3x normal limit	≥ 3x normal limit

risk factors defined as:
- hypercholesterolaemia
- hypertension
- diabetes mellitus
- cigarette smoking
- positive FH premature ischaemic heart disease
- obesity
probability of having a cardiac event:
- score 1-3: 1.7%
- score 4-6: 17%
- score >6: 50% chance of infarct, PTCA, CABG or death within 6 wks

risk stratification recommendations of NHFA 2006

as per National Heart Foundation of Australia 2006⁴⁾
does not use GRACE risk criteria nor FRISC criteria, but does use TIMI risk score criteria mainly as factors in the intermediate risk category.
personally, I have issues with this NHFA risk classification:
- it will be obvious that a patient with a HIGH TIMI score will more than likely end up in the NHFA Intermediate Risk Group when in fact they should be the ones considered for early invasive Mx (angiography)
  - ie. age > 64yrs, on aspirin, with 3 risk factors, and PH documented coronary obstruction with 2 episodes of pain within 48hrs gives a TIMI score of 5 but if there are no NHFA high risk factors means he might end up in the intermediate category and being discharged from the ED for a trial of death at home!
- it would seem more logical to have added an additional criteria to the High risk criteria - a TIMI score > 1.
- in fact the authors of the NHFA guidelines note regarding the Mx of the high risk group when considering invasive Mx “Additional risk stratification on the basis of a TIMI score of greater than 3 for deciding which patients might be transferred for early invasive management may be considered where funding is constrained, but it must be remembered that the 14-day cardiac event rates are still considerable, even for those with low TIMI scores”
- I thus would suggest the absence of the TIMI score criteria for the NHFA high risk criteria is probably an over-sight, and a potentially dangerous one.
- furthermore, it does not take into account the clinician's gestalt impression of how typical the pain is of being ischaemic cardiac pain - patients who have typical angina-like pain consistent with “unstable angina” and with an intermediate factor perhaps should be regarded as high risk.

high risk group criteria

clinical features consistent with acute coronary syndromes AND ANY ONE OF:
- repeated or prolonged (>10 minutes) ongoing chest pain or discomfort
- elevated troponin
- persistent or dynamic ECG changes of ST depression ≥0.5mm or new T wave inversion ≥ 2mm
- transient ST elevation [≥0.5mm] in more than 2 contiguous leads
- known left ventricular systolic dysfunction (LVEF <0.4)
- haemodynamic compromise –systolic BP <90mmHg, cool peripheries, significant diaphoresis, pulmonary crepitations and/ or new onset mitral regurgitation
- sustained VT
- syncope
- prior percutaneous coronary intervention within 6 months
- prior coronary artery bypass graft (CABG)
- known diabetes with typical symptoms
- known chronic renal disease [estimated GFR<60mL/min] with typical symptoms
- TIMI risk score > 2 (this is my addition as I am sure it was left out of the NHFA guidelines erroneously)

intermediate risk group criteria

clinical features consistent with acute coronary syndromes, NO HIGH RISK FACTORS AND ANY ONE OF:
- resolved chest pain or discomfort in the past 48 hours that occurred at rest or was repeated or prolonged (> 10 mins)
- age >65 years
- known chronic renal disease [estimated GFR<60mL/min] with atypical symptoms
- known coronary artery disease – prior AMI with LVEF >0.4 or known coronary lesion > 50%
- Two or more of: known HT, family history, active smoking or hyperlipidaemia
- Prior regular aspirin use
- Known diabetes with atypical symptoms

low risk group criteria

clinical features consistent with acute coronary syndromes, NO HIGH OR INTERMEDIATE RISK FACTORS
although not part of the NHFA guidelines, a subgroup of these perhaps could be regarded as VERY LOW RISK⁵⁾ and perhaps could be discharged from ED earlier, although this Vancouver Chest Pain Rule for early discharge requires further validation⁶⁾:
- age < 40 yrs or if age 40-64yrs, normal troponins at 0 and 2 hours.
- no PH ischaemic heart disease
- normal ECG