Sunday, January 27, 2019

Myths in Diagnosis of ACS

Myth 1
Absence of Classic Chest Pain obviates the need for ACS work up

The absence of chest pain in no way excludes the diagnosis of ACS. Around 33-50% of the patients with ACS present to the hospital without chest pain. Close to 20% of patients diagnosed with acute MI present with symptoms other than chest pain. Risk factors associated with the absence of chest pain included age, female gender, non-white race, diabetes mellitus, and a prior history of congestive heart failure or stroke. Over the age of 85, 60–70% of patients with acute MI present without chest pain; shortness of breath is the most frequent anginal equivalent in this population.

Patients experiencing an acute MI without chest pain are more likely to suffer delays in their care. They were also more likely to die in the hospital compared to patients who presented with chest pain. Over the age of 85, 60–70% of patients with acute MI present without chest pain.

Myth 2
Reproducible chest wall tenderness on palpation rules out ACS
The combination of three variables – sharp or stabbing pain, no history of angina or acute MI, and pain that was pleuritic, positional, or reproducible – is considered as a very low-risk group. Chest pain localized to a small area of the chest is often thought to suggest a musculoskeletal etiology. In one study, however, 27 of 403 patients (7%) with acute MI localized their pain to an area as small as a coin. On examining the patient, one should be careful in determining if the pain induced by chest palpation is the same pain as the presenting pain and more importantly think if the history is congruent with MSK pain. If there is no defined injury or event that could have led to a soft tissue injury, we should be reluctant to render a diagnosis of musculoskeletal pain.

Several studies have shown that chest wall tenderness can be misleadingAlthough certain chest pain characteristics decrease the likelihood of acute MI, none is powerful enough to support discharging at-risk patients without additional testing. In patients with chest pain, chest wall tenderness may suggest that acute MI is less likely but it does not effectively rule out the diagnosis. Given the potential implications of missing ACS, using chest wall tenderness as an independent rule out strategy is not recommended in patients at risk for ACS.

Myth 3
A normal ECG and normal cardiac enzymes rule out ACS
No historical complaint, physical finding, or ECG pattern has a negative predictive value of 100% for MI. Rather the correct statement would be this - Patient is less likely to be experiencing an MI if the ECG is normal, but further work up is needed to discard the diagnosis. Use ECG as more of a rule-in test, not a rule-out test. 

Cardiac markers provide a non-invasive means of determining whether myocardial damage has occurred. When ischemia gives way to infarction, the myocardial cell membrane is disrupted and various chemical markers are released into the systemic circulation. 
Cardiac Troponins  (I or T) are now the preferred cardiac markers for identifying myocardial damage. It is important to remember that troponin can only detect myocardial cell death but not ischemia.

Take Home:
  • Do not exclude the diagnosis of acute cardiac ischemia or MI based on the absence of pain, especially when evaluating dia- betic patients, the elderly, and women.
  • Never use reproducible chest wall tenderness to exclude the diagnosis of acute MI.
  • Neither a single normal ECG nor a single negative set of cardiac enzymes should be used to rule out acute cardiac schema. 


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Posted by:

     Lakshay Chanana
     ST4 Trainee
     Royal Infirmary of Edinburgh
     Department of Emergency Medicine


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