Pulmonary embolism is both over-investigated in young people and missed in elderly people and those with comorbid conditions, and those with PE can have a benign or complicated course. I’ve shared some bounceback cases on PE, and here are a few studies to keep in mind to better assess and manage patients with potential PE
The fear of missing a PE in young people leads to both short and long-term complications (anaphylaxis and radiation from the CT, and the risk of bleeding from anti-coagulation), and the challenges of interpreting sub-segmental PEs. Thankfully the PERC rule has emerged to stratify very low risk patients for whom these risks of investigation/treatment are greater than their risk of PE. It is undergoing RCT in the PROPER trial,
My mnemonic for remembering PERC is that is it’s negative then “NO D-DIMER” needed
- North of 50 (age)
- Oral blood (hemoptysis)
- DVT in the past
- Double estrogen (exogenous)
- Massive leg (unilateral swelling)
- Elevated HR >100
- Reduced )2 sat <95%
A couple of caveats: the vitals refer to triage vitals, and normalization of vitals does not reduce the risk. And secondly, PERC should not trump clinical decision; like any test it should be applied after you determine your pre-test likelihood, and only in low-risk patients. Here are my mnemonics for the PERC rule (very low risk, no D-dimer) and Well’s criteria (risk stratify to D-dimer or immediate CTPA)
On other other end of the spectrum from young and healthy people, elderly patients and those with co-morbid conditions often have delayed diagnosis of PE:
Prospective Study of the Clinical Features and Outcomes of Emergency Department Patients with Delayed Diagnosis of Pulmonary Embolism. Acad Emerg Med 2007 July;14(7):592-598. In this analysis of 161 patients admitted to hospital and diagnosed with PE, 88% were diagnosed in the emergency department and 21% had a delayed diagnosis. Those with delayed diagnosis had equal or worse measures of PE severity and had higher rate of in-hospital adverse events. Risk for delayed diagnosis included age and altered mental status (defined in a very broad way to include altered, syncope, seizure, dementia, organic brain syndrome, mental retardation).
Delay and misdiagnosis in sub-massive and non-massive acute pulmonary embolism. Eur J Int Med 2010 Aug;21(4):278-282. In this retrospective analysis of 375 elderly patients (mean age 75) with PE, misdiagnosis occured in 50% of cases and delay in diagnosis longer than 6 days occured in 50%. Factors associated with misdiagnosis included age, absence of syncope and absence of sudden onset dyspnea.
Risk Factors Associated with Delayed Diagnosis of Acute Pulmonary Embolism. J Emerg Med 2012 Jan;42(1):1-6. In this study of 400 patients diagnosed with PE, 18% had were diagnosed greater than 12 hours after presentation. Factors associated with earlier diagnosis included immobility and tachycardia, and risk factors for delayed diagnosis included age, coronary artery disease and morbid obesity.
As they conclude, “Older patients with cardiovascular comorbidities had longer times from ED arrival to CT diagnosis. Our data suggest that these patients represent more of a diagnostic challenge than those presenting with traditional risk factors for PE, such as tachycardia and recent immobilization. Physicians should consider these factors to diagnosis acute PE promptly in the ED.”
This can be a challenge as both PE and ACS can have overlapping symptoms, ECG changes and troponin elevation. If we think of unstable angina we should consider if it’s unstable due to a PE. Similarly, if a patient has a COPD exacerbation, we should consider if PE was a precipitant–in one metaanalysis, one in four COPD patients requiring admission for an acute exacerbation have PE.
There’s also increasing awareness of bedside tests to help in the early diagnosis of PE.
1) ECG: while we’re taught to look for S1Q3T3, this is just one of many signs of pulmonary hypertension and RV strain
12-Lead ECG Findings of Pulmonary Hypertension Occur More Frequently in Emergency Department Patients With Pulmonary Embolism Than in Patients Without Pulmonary Embolism. Ann Emerg Med 2010 Apr;55(4):331-335. None of these likelihood ratios are very high, but they are worth considering when reading an ECG on a patient with chest/back/flank pain, shortness of breath, syncope, etc.
- S1Q3T3 8.5% with pulmonary embolism versus 3.3% without pulmonary embolism (LR+ 3.7; 95% CI 2.5 to 5.4)
- nonsinus rhythm, 23.5% versus 16.6% (LR+ 1.4; 95% CI 1.2 to 1.7)
- inverted T waves in V1 to V2, 14.4% versus 8.1% (LR+ 1.8; 95% CI 1.3 to 2.3)
- inversion in V1 to V3, 10.5% versus 4.0% (LR+ 2.6; 95% CI 1.9 to 3.6)
- inversion in V1 to V4, 7.3% versus 2.0% (LR+ 3.7; 95% CI 2.4 to 5.5)
- incomplete right bundle branch block, 4.8% versus 2.8% (LR+ 1.7; 95% CI 1.0 to 2.7)
- tachycardia (pulse rate >100 beats/min), 28.8% versus 15.7% (LR+ 1.8; 95% CI 1.5 to 2.2
These ECG changes not only help diagnose but also risk stratify patients:
Findings From 12-lead Electrocardiography That Predict Circulatory Shock From Pulmonary Embolism: Systematic Review and Meta-analysis. Acad Emerg Med 2015 Oct;22910):1127-1137. This review of 10 studies of 3007 patients found six findings of RV strain that are associated with an increased risk of circulatory shock
- T wave inversion V1-4
- ST elevation in aVR
- Atrial fibrillation
In the HEARTS approach to ECG this includes: Heart rate/rhythm (sinus tach, Afib), Electrical (RBBB), Axis (S1Q3T3), R-wave, Tension, ST (Tw inversion anterior, ST elevation aVR).
AF can mimic PE symptoms but there is not a strong association. If PE is suspected on the basis of dyspnea, the presence of AF decreases the risk of PE; but if PE is suspected on the basis of chest pain without dyspnea, then the presence of AF increases the risk of PE.
2) Point of Care Ultrasound (POCUS) is also emerging as a helpful diagnostic aid to early diagnosis of PE (with the caveat of false positives from chronic pulmonary hypertension and false negatives from small PEs)
Right Ventricular Dilatation on Bedside Echocardiography Performed by Emergency Physicians Aids in the Diagnosis of Pulmonary Embolism. Ann Emerg Med 2014 Jan;63(1):16-24. In this prospective observational study of 146 patients with moderate to high pre-test probability of PE, 30 patients had PE, and bedside ultrasound was found to be highly specific but poorly sensitive
- RV dilation (RV>LV): 50% sensitive, 98% specific, LR+29, LR- 0.5
- RV dysfunction (hypokinesis, paradoxical septal motion, McConnel’s sign) were less sensitive but as specific
- McConnell sign is mid wall akinesia and apical motion normal