The Case:
The patient is a 64-year-old female with an unknown past medical history who presented to the ED with altered mental status. Her BP was 100/80 mmHg, HR 101 BPM, RR 21 bpm, SPO2 63% on room air, and T 36.8ºC (98.3ºF). The patient was placed on a non-rebreather mask at 15L, and her oxygen saturation improved to 97%. She was given sedatives for acute agitation and delirium. On exam, the patient was tachypneic and had bilateral crackles and decreased breath sounds throughout all lung fields. Her cardiac exam was notable for a regular rhythm without murmur. The remainder of the physical exam was unremarkable.
Point-of-care ultrasound was performed and demonstrated B-lines throughout all lung fields, and a subxiphoid cardiac view demonstrated a dilated right ventricle (RV) and trace pericardial effusion. A point-of-care echocardiogram was performed, which re-demonstrated right ventricular dilation and further revealed a D-sign.
Laboratory work-up was significant for high-sensitivity troponin of 18.1 ng/L (normal < 5) and BNP of 951 ng/L (normal < 100) in addition to hyponatremia, hyperkalemia, and acidosis. Chest X-ray showed diffuse bilateral lung opacities. Computed tomography with angiography of the chest was notable for changes consistent with interstitial lung disease (ILD) and right heart dysfunction.
Figure 1. Point-of-care echo from this case with D-sign and trace pericardial effusion.
What signs of right heart strain can be identified on point-of-care ultrasound?
Signs of right heart strain on point-of-care echo include:
Increased right-to-left ventricle (LV) size ratio: A normal RV:LV ratio is ≤0.67:1 (1). A ratio greater than 0.67:1 indicates an increase in pulmonary vascular resistance, which causes a rapid dilation of the right ventricle due to significant RV wall compliance. This can be assessed in the parasternal short axis (PSAX) and apical four-chamber (A4C) view.
Abnormal interventricular septal motion: Also referred to as septal bowing or the D-sign, the interventricular pressure in the LV is usually greater than the RV which results in septal motion toward the RV in a normal state (2). However, when there is increased RV pressure, the septum flattens or bows toward the LV, best visualized in the PSAX view.
McConnell's sign: This sign appears as RV free wall hypo- or akinesis with apical sparing in the A4C view (3). The mechanism is not completely understood but is thought to be due to tethering of the apex of the RV to the LV. The contraction of the LV pulls the apex within while the remainder of the RV-free wall has little to no motion due to RV overdistension from pressure overload.
Tricuspid regurgitation: As the RV dilates from increasing RV pressures, the tricuspid annulus dilates, pulling the valve leaflets apart. This allows for regurgitant flow through the tricuspid valve (1). This can be assessed in the A4C view with color doppler placed over the valve.
Decreased tricuspid annular plane systolic excursion (TAPSE): This finding results from tracing the displacement of the tricuspid annulus during systole using M-mode in the A4C view. A normal TAPSE is >17mm. When right heart pressures are increased, RV dilation occurs which decreases the contractility of the RV and, therefore, the range of motion of the tricuspid annulus.
How can you distinguish between acute and chronic right heart strain?
Determining acute versus chronic right heart strain can assist in narrowing your differential diagnosis. These point-of-care ultrasound findings can assist in determining the acuity of RV strain:
RV wall thickness: Normal RV wall thickness is less than 5mm (3). In the setting of RV dilation with signs of RV failure, a wall thickness greater than 5mm supports the diagnosis of chronic right heart strain as the cardiac muscle hypertrophied with long-term exposure to increased strain.
60/60 sign: This sign refers to a tricuspid regurgitation pressure gradient (TRPG) ≤60mmHg and a pulmonary artery acceleration time (PAAT) <60ms. If obtained values are both less than 60, this supports the diagnosis of acute right heart strain whereas if they are both greater than 60, chronic right heart strain is more likely. TRPG is obtained by using continues wave doppler over the tricuspid valve in the A4C view. When chronic right heart strain occurs, RV hypertrophy and tricuspid annular dilation result, which increases the regurgitation velocity and correlates with the pressure gradient across the valve. PAAT is obtained by using pulse wave doppler proximal to the pulmonic valve in the right ventricular outflow tract view. A decreased PAAT, seen in acute right heart strain, occurs due to increased RV pressure shortening the amount of time it takes for the blood to reach peak velocity across the pulmonic valve due to decreased pulmonary vascular compliance.
Case Discussion:
The patient was diagnosed with acute right heart failure secondary to ILD and admitted to intensive care. The patient was started on epinephrine and vasopressin to improve hypotension and cardiac inotropy, bicarbonate infusion to improve acidosis, and nitroglycerin and furosemide to reduce afterload.
Chronic lung disease, such as ILD, increase the afterload of the RV, and, therefore, RV pressure due to increased alveolar pressures from fibrosis, which decreases gas exchange, increased vascular constriction from alveolar hypoxia, and local inflammatory processes (4). Treatment is aimed at reducing pulmonary vascular resistance and right heart strain. Mainstays of treatment include oxygen therapy for hypoxia, diuretics for volume overload, vasopressors and inotropic agents for hypotension and cardiac dysfunction, and pulmonary vasoactive agents (5). Intubation should be avoided if possible as this can increase RV pressure due to increased intrathoracic pressures. However, if acute respiratory failure is present and intubation is required, ventilator settings should aim to minimize PEEP and peak pressures and maximize FiO2 to improve hypoxia and decrease hypercapnia.
Authored by Michael Hohl, MD.
References:
Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr. 2010;23(7):685-788. doi:10.1016/j.echo.2010.05.010
Dinh, V. (n.d.). The D sign - right heart strain from pressure vs volume overload. POCUS 101.https://www.pocus101.com/the-d-sign-right-heart-strain-from-pressure-vs-volume-overload/#:~:text=The%20%E2%80%9CD%20Sign%E2%80%9D%20is%20an,Pressure%20and%2For%20Volume%20overload.
Alerhand S, Sundaram T, Gottlieb M. What are the echocardiographic findings of acute right ventricular strain that suggest pulmonary embolism?. Anaesth Crit Care Pain Med. 2021;40(2):100852. doi:10.1016/j.accpm.2021.100852
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