We had a great discussion this morning about a
patient presenting with classic concerning cardiac chest pain who had minimal
cardiac risk factors, negative biomarkers and no significant ECG changes. One
of the points we discussed was: Should this patient be treated for ACS prior to
risk stratification? The answer is the same as for most of our decisions in
medicine – it is a balance of risks vs benefits.
I will present a general approach to ACS. But remember – this is just a guide and all patients with chest pain are unique and can have subtle differences that can completely change management!
First, decide if the patient has an Acute Coronary Syndrome (ACS). Remember, ACS represents ‘acute’ plaque rupture and can include unstable angina, NSTEMI and STEMI. On your initial assessment, there are 4 things to consider when making this decision.
1) History
2) Physical
Exam
3) ECG
4) Biomarkers
Use these tools to
determine whether or not your patient has a high likelihood of ACS. If there is
objective evidence of ACS (positive troponin, ECG changes) or if the likelihood
of ACS is high then you will treat. If you do not think that there is an ACS or
if the likelihood of ACS is low, look for another cause of chest pain. If you
can’t find one, consider risk stratification as an outpatient (assuming there
are no other concerning features).
And don't forget to include other diagnoses on your
differential that may mimic ACS (ie. PE, pericardititis, etc...) and those
conditions that are treated entirely differently (ie. aortic dissection).
If you decide that your patient has an NSTEMI or unstable angina, you can use various risk calculators to determine prognosis and decide on a strategy (conservative or early invasive). The TIMI risk score is a commonly used scoring system (http://www.timi.org/index.php?page=calculators) that predicts 14 day risk of mortality, new/recurrent MI or severe ischemia requiring urgent revascularization. The TIMI risk score calculator is based on 7 factors: age>65, 3 or more CAD risk factors, known CAD, ASA use in the past 7 days, 2 or more episodes of angina in 24 hours, ST changes >0.5mm, positive cardiac biomarker.
Key Point: Remember, only use this risk calculator once you have decided your patient has or likely has ACS. It is not appropriate to use this scoring system to determine if your patient has ACS.
In general, use a conservative strategy for low
risk (medication and non-invasive risk stratification) and use an early
invasive approach for high risk (medication and angiogram within 24-48hrs).
Patients diagnosed with ACS should receive ASA and anticoagulation along with
the other cocktail of cardiac medications which we won’t go into in this blog.
So, how do you manage a patient with classic chest pain but no ECG changes and normal troponin? This patient could be labelled as ‘possible’ ACS. This is a grey zone that may lead to some confusion and maybe even variation in practice among internists.
- If the ECG is non-ischemic and serial
troponins negative and the patient remains free of
chest pain BUT there is still a suspicion of ACS, a
stress test is generally required to rule out unstable angina. This can be
done as an inpatient (if intermediate/high risk features) or as an
outpatient within 72 hours (if low risk features and no other concerns).
Regarding acute medical management, the AHA guidelines suggest treating
(ASA and anticoagulation) patients with definite or likely ACS.
- According to AHA guidelines
(2014), for patients with possible ACS but no objective evidence of
myocardial ischemia (non-ischemic ECG and normal troponin):
- It is reasonable to observe them in a
telemetry unit with serial ECGs and troponin at 3-6 hour intervals.
- It is reasonable to perform non-invasive risk
stratification before discharge or within 72-hours of discharge.
- In low-risk patients who can be discharged with outpatient risk
stratification it is reasonable to give them daily ASA, short acting
nitro and provide instructions about activity level and follow-up.
So the bottom line is: In general, patients with ‘possible’ ACS without objective ischemia (negative trops, normal ECG) do not require full anticoagulation prior to risk stratification. However, there are exceptions to every rule and these patients should be carefully assessed. The guidelines say that ‘likely’ or definite ACS should be treated. So how do we determine what to do for patients who fall in the grey zone between ‘possible’ ACS and ‘likely’ ACS? This is a case by case decision where you need to weigh the risks and benefits of therapy. This is where clinical experience and judgement are paramount.
Reference:
Amsterdam, Ezra A., et al. "2014 AHA/ACC guideline for the management of
patients with non–ST-elevation acute coronary syndromes: a report of
the American College of Cardiology/American Heart Association Task Force
on Practice Guidelines." Journal of the American College of Cardiology 64.24 (2014): e139-e228.
