Why a 12-lead EKG, history are needed to diagnose patient's complaint

A differential diagnosis for a patient with two weeks of chest pain casts a wide net for all possible causes

Article updated July 30, 2017

You proceed to carry out an uneventful transport and eventual emergency department transfer of a 54-year-old male patient complaining of chest pain stemming from an incident from two weeks prior.

The patient's description of the chest pain is consistent with a clinical presentation of an acute coronary syndrome.

The EKG shows pathological Q-waves in the inferior leads, particularly III and aVF, which could be the result of a myocardial infarction. There is ST elevation in leads II, III, aVF, -aVR, and V2-V6. The “-aVR” concept refers to the inverse of the aVR lead, similar to viewing that lead through the back of the EKG paper.

It would be prudent to assume that this patient is indeed suffering from a myocardial infarction. The primary concern in this case is whether an infarction occured at the time of EMS activation, a few hours before or even two weeks prior.

In developing our differential diagnoses for this patient, MI should certainly be high on the list. However, it is not the only differential to consider. The clinical presentation of pleuritic chest pain alleviated in the sitting position (and probably after leaning forward, if evaluated), is consistent with a differential diagnosis of acute pericarditis.

The EKG somewhat supports this diagnosis with diffuse ST-segment elevations across many leads. Although we do not see PR-segment depression – note "segment” and not "interval" – this EKG shows a specific change in lead aVR. Lead aVR shows PR segment elevation, which if observed as –aVR, would in fact be PR depression and is a consistent finding with acute pericarditis.

A thorough clinical history should always be emphasized as the driving force for diagnosing acute pericarditis. Acute pericarditis is a possible complication of MI and is called Dressler's Syndrome when it presents weeks or months after an MI or cardiac injury. It is characterized by pleuritis and pericardial friction rub on auscultation. In any case, pericarditis can result in severe heart failure, tamponade and death if undetected.

Another cause for concern in this case, should we assume that the acute phase of the infarction occurred two weeks prior, is persistent ST elevation. The presence of persistent ST segment elevation greater than 1 mm in the precordial leads several days/weeks following an acute myocardial infarction is suggestive of a ventricular aneurysm.

This finding is most often associated with an acute anterior MI, when the ST segment elevation either reappears or persists beyond the subacute phase of MI. Elevation persisting for greater than one week – but typically greater than three months – warrants further investigation due to the fact that the aneurysmal ventricular wall can be a potential site of left ventricular thrombus and the initiation of ventricular arrhythmias.

Differential diagnoses for these EKG changes include:

  • Myocardial infarction
  • Transient myocardial ischemia
  • Benign early repolarization
  • Myocarditis
  • Pulmonary embolus
  • Cerebrovascular accident
  • Pneumothorax
  • Hyperkalemia
  • Subepicardial hemorrhage
  • Ventricular aneurysm

We know little about what happened to this patient two weeks prior to the activation of EMS, but as mentioned above, we can assume that this patient has recently experienced a MI. Further diagnostic studies are highly suggested and should probably include echocardiography, cardiac enzymes and cardiac catheterization. If the occlusion – and thus infarction – occurred two weeks ago, administration of aspirin would likely be of no benefit. Since an acute myocardial infarction could be evolving, Aspirin is warranted per the crew's chest pain protocol. However, aspirin may be useful for the management of pericarditis.

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