Case Details

A 38-year-old woman, previously healthy, was admitted to the neuroscience intensive care unit following a thoracic fusion. On post-op day four, the patient suffered a syncopal event and was hypotensive, tachycardic, and hypoxemic. A rapid response was called, she was started on oxygen by nasal cannula, given intravenous fluid boluses, and admitted to the neurocritical unit for further monitoring and work-up. An EKG was obtained, which demonstrated right axis deviation and a right bundle branch block [Figure 1]. Point-of-care ultrasonography (POCUS) was performed, which revealed right ventricular enlargement and dysfunction, with a D-sign and McConnell’s sign [Figure 2].  A computed tomography scan of her chest was obtained next [Figure 3], which demonstrated a large pulmonary embolism (PE) with bilateral clot burden, with suspicion for a saddle clot. She was taken for catheter-directed thrombolysis, followed by a heparin infusion. Over the following three days, she was monitored in the neurocritical care unit. Transthoracic echocardiography repeated on day two post-thrombolysis demonstrated normal right ventricular function, no regional wall abnormalities with the left ventricle, and normal systolic pressures measured in the pulmonary artery. She remained hemodynamically stable and was weaned to room air. She was transitioned to warfarin and the remainder of her hospital course was uneventful.  She was ultimately discharged home. 

Evidence, Pathophysiology, Views, and Differential Diagnoses 

Pulmonary Embolism (PE) is a life-threatening condition associated with significant morbidity and mortality, and requires prompt diagnosis and management. One of the quickest ways to assess for the presence of PE is through POCUS.  Studies have demonstrated that POCUS has a sensitivity ranging from 60 - 83% and specificity ranging from 50 - 90%¹. 

Large PEs will cause elevated pressures in the pulmonary vasculature resulting in right ventricular strain and dilation, manifesting as the so-called ‘D-sign’ on POCUS.  This is seen due to ventricular septal deviation and flattening. Ventricular interdependence causes a reduced left ventricular (LV) diastolic size with impaired LV filling and preload, with subsequent reduced cardiac output and hypotension.³ However, both acute and chronic pulmonary hypertension can cause a D-sign, so while sensitive, it is not always specific for pulmonary embolism, and merely indicates the presence of right ventricular strain with pulmonary hypertension. In cases of volume overload, the D-sign will be present only in diastole, whereas in acute pressure overload, it will be seen during the entire cardiac cycle. 

In addition, elevated pulmonary vascular pressures may also lead to ‘McConnell’s Sign’ in the right ventricle. McConnell’s Sign is defined as hypokinesis or akinesis of the free wall of the right ventricle, with normal function at the apex. The presence of a McConnell’s sign has mixed sensitivity and specificity, initially being described with sensitivity and specificity of 77% and 94%, respectively⁴ with a more recent study showing its presence in PE in 68% of patients and without PE in 32% of patients². Presence of McConnell’s sign mandates further workup for right heart pathology. Absence of McConnel’s sign also does not definitively rule out the presence of PE. Overall, however, McConnell’s sign is useful to have in mind when PE is on the differential. 

Conclusion

POCUS is a useful tool in the early diagnosis and management of pulmonary embolism in unstable patients.  While CT scan is the gold standard, the immediacy of POCUS can give early clues into diagnostic probabilities and expedite time to definitive treatment.   

Figures

Figure 1 – Initial electrocardiogram demonstrating the right axis deviation and right bundle branch block.

Figure 2 – Ultrasound images. A – Short axis view. B – Apical four chamber view.
 

A – Short Axis view
 

B – Apical Four Chamber View 
 

Figure 3 – Initial CTPA – coronal section – demonstrating the pulmonary embolism (arrow)