Approach to chest pain: Clinical sciences

Chest pain is a common chief complaint, with a broad differential diagnosis that includes some potentially life-threatening causes. So your workup needs to focus on ruling out these dangerous causes before considering more benign ones. 

Let’s take a look at this approach. 

Your first step in evaluating a patient presenting with chest pain is to systematically assess their ABCDEs, which stands for airway, breathing, circulation, then disability and exposure. This helps you judge if the patient is stable or unstable, so you can treat any issues at each step. Your patient may, for example, require endotracheal intubation.   
In an unstable patient, your priority is to stabilize their airway, breathing, and circulation. Once they are stabilized, your next step is to evaluate for life-threatening causes of chest pain, such as ST-elevation myocardial infarction or STEMI for short, cardiac tamponade, aortic dissection, pulmonary embolism, or tension pneumothorax. And remember, even if your patient is stable, it does not rule out these life-threatening conditions.   
So what do you do in the case of a stable patient presenting with chest pain?  

Your evaluation begins with a focused history and physical examination, or H&P, alongside an electrocardiogram, or ECG. That ECG needs to be performed and interpreted promptly! You’re going to use it to evaluate the patient for some life-threatening conditions.  

At the same time, if you suspect the patient has a critical illness or might become unstable, acute management will be required. First, place them on continuous cardiac monitoring with pulse oximetry and establish IV access. If they are hypoxemic, you should also provide supplemental oxygen. 

Okay, now that you’ve done the history and physical, the ECG, and acute management, it’s time to check for the acute coronary syndrome or ACS.  

The first condition to look for is an ST-elevation myocardial infarction, or STEMI. 
 
In an ECG, look for localized ST-elevations in 2 contiguous leads. If present, that’s diagnostic for a STEMI. 
  
However, a left bundle branch block or LBBB can mask ST elevation, so the diagnosis can also be made if there’s a new LBBB with a presentation consistent with ACS. LBBB typically presents as QRS longer than 120ms, a dominant S wave in V1, and broad notched R waves and absent Q waves in the lateral leads, like V6.   
If there is no ECG evidence of a STEMI, you need to assess clinical findings for other immediately life-threatening conditions.  

Remember that the ECG findings could still provide valuable data for a different diagnosis, so use them in combination with a more complete history and physical during your evaluation.  These conditions include cardiac tamponade, aortic dissection, pulmonary embolism, pneumothorax, and esophageal perforation.   

First, let’s look at cardiac tamponade.  

You should suspect this condition if your patient has hypotension, jugular venous distention, and muffled heart sounds on physical examination. You can also check for pulsus paradoxus where there’s an abnormally large drop in systolic blood pressure during inspiration that’s greater than 10 mmHg. During the physical exam, you can also do a point of care ultrasound, or POCUS, to check for pericardial effusion. 

The ECG may show sinus tachycardia, low QRS voltage, or electrical alternans, which refers to alternating QRS amplitudes.  

If you suspect cardiac tamponade, your next step is to promptly obtain a transthoracic echocardiogram or TTE. The presence of a pericardial effusion with findings like diastolic right ventricular collapse, systolic right atrial collapse, and dilated IVC with decreased respiratory variation confirm your diagnosis.   
Next up is aortic dissection.  

These patients often present with “tearing” pain that radiates to the back. Their past medical history can be significant for conditions like hypertension, or connective tissue disorder. The patient may have focal neurologic deficits, a new murmur, or asymmetric pulses on physical examination. The ECG is typically non-diagnostic.  

If you order a chest X-ray, you may see suggestive findings like a widened mediastinum, but a normal chest X-ray does not exclude the diagnosis.  

So if you suspect aortic dissection and the patient is stable, the next step is an immediate CT angiogram of the chest. This will show an intimal dissection flap and a true and false lumen. 

If the patient is unstable, the best initial test would be a transesophageal echocardiogram or TEE.     
Another common and sometimes life-threatening cause of chest pain is pulmonary embolism or PE.  
 
You should suspect PE in a patient who presents with sudden-onset chest pain associated with dyspnea, hypoxia, cough, and hemoptysis, especially if they have risk factors for venous thromboembolism like active malignancy, recent surgery, prolonged immobilization, pregnancy, or oral contraceptive use.  

The most common ECG finding for PE is actually just sinus tachycardia. A rare but specific ECG finding of PE is S1Q3T3, where there’s a prominent S wave in lead 1, Q waves in lead 3, and inverted T waves in lead 3. 

Now if you suspect PE, you should first calculate your patient’s Wells score. This tells you their risk of having a PE. In low-risk patients, order a D-dimer. If the D-dimer is normal, you have ruled out PE with excellent negative predictive value. If the D-dimer is elevated, get a CT pulmonary angiogram or CTPA.  A PE will show up as filling defects within the pulmonary vasculature. IV contrast is contraindicated in some patients, like those with renal disease. So we can order a ventilation perfusion, or V/Q scan. The scan will show normal ventilation in the lungs, but decreased perfusion if an embolus is present.  

What if the Wells score puts the patient at high risk for PE? In that case, the pre-test probability for PE is very high, so you skip the D-dimer and go straight to CT pulmonary angiogram or V/Q scan.