An 75 year old woman presented to the emergency department for evaluation of shortness of breath, generalized fatigue, and diarrhea. Initial nursing notes reported history of COPD with Sp02 of 89% on room air. The patient had been discharged two weeks ago after presenting for altered mental status and failure to thrive. She was placed on antibiotics for a possible UTI at that time. The patient reported an increase in dyspnea since her hospital stay, with acute worsening on the day of presentation. She noted no improvement with her typical inhalers for COPD.
Review of systems was otherwise negative for chest pain, cough, fever, leg pain and edema.
Her initial recorded vitals were BP: 123/74, HR 100, T 36.4C, RR 18, SP02 100% (on 5L NC).
Examination showed a frail appearing tachypneic female with end expiratory wheezes, no lower extremity edema or calf tenderness. EKG, labs, and point-of-care cardiac ultrasound were ordered after the initial exam. Shortly after labs were collected, the intern completed the following ultrasound:
Parasternal short axis views revealed massively dilated RV when compared to the LV.
Apical four chamber view showed enlarged and hypokinetic RV.
IVC diameter was approximately 2 cm with no respiratory variation.
The intern noticed her enlarged right ventricle and was concerned about increased right heart pressure, but was not sure if this represented a chronic condition in the setting of her long-standing COPD. He reviewed her previous ultrasound, performed in the emergency department 12 days prior at her last visit. Note the dramatic difference in RV size as well as LV end diastolic diameter.
Let’s take the findings of her most recent ultrasound one by one.
1) Right ventricular dilation
The normal ratio of right-to-left ventricular size is generally quoted as < 0.6, with a ratio of >1.0 considered to be significant right ventricular enlargement. This is not specific to PE, as other conditions including COPD, congenital anomalies, and primary pulmonary hypertension may also cause RV enlargement. One way to differentiate an acute vs chronic process is the appearance of the RV wall. If this is an acute process, classically the RV wall appears thin, representing rapid dilation. Normal RV free wall thickness is 2.4 +/- 0.5mm. Measurements greater than 5mm suggest RV hypertrophy and favor a chronic process (1).
2) McConnell’s sign
Did you notice the significant hypokinesis of the RV with sparing of the apex? This is “McConnell’s sign.” First reported in 1996, McConnell’s sign was described and validated in a small cohort of hospitalized patients with RV dysfunction. Findings of mid-free wall RV dysfunction with normal function of the apex were found to be insensitive, but 94% specific, for the diagnosis of acute pulmonary embolism (2). One prospective observational study in the emergency medicine literature found that among patients with suspected or confirmed pulmonary embolus, the presence of McConnell’s sign was 100% specific for the diagnosis (3). This finding should be taken in context however, as RV infarction may have similar songraphic appearance. There are case reports of other etiologies causing these findings as well, including COPD, SLE, etc (4).
3) D Sign
Click here for great image of D sign from the Hennepin Ultrasound Blog.
Another recognized sonographic finding in pulmonary embolism is the so-called “D sign,” or intraventricular septal wall flattening. Two factors lead to the pressure gradients that give the appearance of the D sign. Blocked flow to the pulmonary arteries can cause increased right ventricular pressures. Decreased venous return from the pulmonary vasculature to the left ventricle can subsequently cause decreased left ventricular end diastolic volume. In combination, this can cause abnormal leftward septal deviation, most prominent in diastole.
Case Conclusion
Initial lab results returned with an elevated troponin of 0.314 and Pro-BNP of 3084. Both had been within normal limits during her last hospital stay. CT PE study was performed showing large bilateral saddle emboli with extension into upper and lower lobe pulmonary arteries bilaterally. The patient was started on a heparin drip with continued stable blood pressures in the systolic 130s and heart rates in the 90s. She was admitted to the telemetry floor and ultimately discharged from the hospital to a skilled nursing facility in 4 days.
Learning Points
- In a patient with multiple etiologies for undifferentiated shortness of breath, use the ultrasound to guide additional testing. Don’t let recent evaluation re-assure you that the patient does not have the pathology of interest. She had both a cardiac ultrasound and CT PE done two weeks prior.
- McConnell’s sign: A highly specific but insensitive marker of pulmonary embolus. Look for relative hypokinesis of the RV with apical sparing.
- Spend time obtaining adequate apical 4 chamber views to assess relative sizes of LV and RV, as this may give clinical clues as to the cause of undifferentiated shortness of breath.
References
1. Ma and Mateer’s Emergency Ultrasound. Third Edition. New York, NY: McGraw Hill Education, 2014.
2. McConnell et al. Regional Right Ventricular Dysfunction Detected by Echocardiography in Acute Pulmonary Embolism. Am J Cardiology. 1996;78: 469-73.
3. Lodato, J., Ward, RP., Lang, R. Echocardiographic Predictors of Pulmonary Embolism in Patients Referred for Helical CT. Echocardiography. 2008; 25: 584-90.
4. Walsh, B. and Moore, C. McConnell’s Sign is Not Specific For Pulmonary Embolism: A Case Report and Review of the Literature. J of Emergency Medicine. 2015; 49: 301-304.
Patrick McCarthy is an emergency medicine physician completing a fellowship in emergency ultrasound at Hennepin County Medical Center.
