March 16th, Pulmonary Embolus and shortness of breath

On Monday March 16th we discussed an interesting case of pulmonary embolus. We had a woman who presented with syncope, hypotension (that improved with fluids) and tachycardia.

As I was not aware of the syncopal episode, I gave an approach to shortness of breath :)

Basically, heart, lungs, low hemoglobin and anxiety are the causes of shortness of breath.

Heart:
a.  endocardium (valvular disease -  aortic stenosis, aortic regurg, mitral stenosis, MR)
b. conduction system issues,
     1. bradycardia - sick sinus, AV blocks,
     2. Tachycardias - a-fib, aflutter, AVNRT, also VTs

b. myocardium
     1. systolic failure (secondary to CAD, etoh, HTN, viral causes)
     2. Diastolic failure (HTN, AS, HOCM).

c.  CAD - shortness of breath can be an angina equivalent, mechanism is ischemia stiffens the myocardium, increasing pressures in the pulm circulation.

d. pericardium - tamponade, constrictive pericarditis

Lungs:
1. Alveol:
    a: pulmonary edema (HF, ARDS)
    b: pneumonia

2. Airways
    a. Suprathoracic - laryngeal edema, or tumor (generally normal oxygenation, STRIDOR - generally inspiratory high pitched sound)

    b. Intrathoracic - asthma, COPD

3. Blood vessels
     a. Pulmonary embolus
     b. primary pulmonary hypertension

4. Pleural
    a. pneumothorax
    b. pleural effusions (transudative/exudative)

5. Interstitium
     a. edema
     b. inflammatory
           1. Organic exposure (hay, cotton)
           2. Mineral exposures (asbestos, silicosis, coal)
           3. Idiopathic disease (sarcoid, lupus, slceroderms)

Anemia

When any adult patient comes into the emergency room with shortness of breath we always start with vital signs, ABCs and make sure they are stable. History, physical exam and then are starting point would be CXR, ECG, and hemoglobin (this are simple tests that can dramatically change management).

We discussed some Pulmonary embolus pearls in diagnosis:
We often use the Well's score for (PE and a separate for DVT), if the value is greater than 4 we consider v/q or CTPA. If less than 4 in the outpatient setting we consider D-Dimer which has GOOD negative predictive value (we can rule out PE).

When to consider someone's breathing is due to PE?
Clear chest x ray but low o2 saturation.
Risk factors for PE, specifically immobility, recent surgery within the past 3 weeks, active malignancy, history of PE.
The wells score also gives several points for no other cause best explains there shortness of breath.

V/Q scan is a great test and often undervalued amongst internal medicine residents, 2 features make it a poor test for our patient population occasionally

1. Abnormal cxr, patients with COPD often may have scarring evident on CXR, making it difficult to interpret the V/Q as there will be some V/Q mismatch.

2. Someone who is unable to inspire (as in someone with cognitive impairment).

** after a negative CXR, V/Q is the ideal test for pregnant patients.

ECG - most often sinus tachycardia, but we should always order it as a new RBBB, tall R wave in V1, the classic but rare S1/Q3/T3 and ST changes in anterior leads.

Blood gases for PE - may just show hypoxia, but in a patient with a COPD exacerbation whose PCO2 is 5 mmHg less than their baseline... consider PE.

Can you get pleural effusion? Yes! More often with chronic PE, but don't forget this on your differential of pleural effusion, it would usually be exudative.


CTPA - in some larger studies in patients with PE, about 20% of the time they were looking for PE, alternative diagnoses were made. Unfortunately, we now have an issue of picking up incidental subsegmental PE because CTPAs are too good for their own good!

There is debate how to treat these, often expert opinion is recommended, people generally treat patients with symptoms, or consider doing an US of the legs to see if a more impressive DVT is present when deciding to treat.

Finally, refer to the PERC score
http://www.mdcalc.com/perc-rule-for-pulmonary-embolism/

this is a scoring system that if negative, you may NOT even order a D-dimer, on room air, less than 50 years of age, no history of dvt (MEANS.... its probably not PE).