Effect of prone position on right ventricular dysfunction due to pulmonary embolism assessed by speckle tracking echocardiography

Abstract

Prone position has shown beneficial hemodynamic effects in patients with right ventricular dysfunction associated with acute respiratory distress syndrome decreasing the right ventricle afterload. We describe the case of a 57-year-old man with right ventricular dysfunction associated with pulmonary thromboembolism with severe hypoxemia that required mechanical ventilation in prone position. With this maneuver, we verified an improvement not only in his oxygenation, but also in his right ventricular function assessed with speckle tracking echocardiography. Our case shows the potential beneficial effect of the prone position maneuver in severely hypoxemic patients with right ventricular dysfunction associated with pulmonary thromboembolism.

Introduction

Prone position has shown beneficial hemodynamic effects in patients with right ventricular dysfunction and acute respiratory distress syndrome (ARDS) based on the decrease in right ventricle (RV) afterload by improving oxygenation and pulmonary recruiting, which reversed the mechanisms triggered by hypoxic vasoconstriction [1]. However, the potential benefit of such maneuver has not been proven so far in patients with right ventricular dysfunction associated with another cause. We will present the case of a patient with right ventricular dysfunction associated with pulmonary thromboembolism which required the prone position maneuver. Its effect was assessed by means of transthoracic echocardiography using the speckle tracking method.

Case presentation

A 57-year-old patient with a history of type II diabetes, dyslipidemia, and obesity (BMI 57), who had recently undergone gastric by-pass surgery, complained of shortness of breath and abdominal pain. Physical examination confirmed the occurrence of tachypnea and desaturation, which required oxygen therapy with a high-flow nasal cannula. An electrocardiogram was carried out showing T-wave inversion from V2 to V6, a blood chemistry result of 1.5 mg/dl creatinine, and 306 ng/l troponin. A CT angiography of the lungs showed images with marginal defects of tree fillings in the upper right lobe, mid-right lobe, and lower left lobe with peripheral arrangement consistent with blood clots. Therefore, anticoagulation was started with sodium heparin infusion and the patient was admitted to the ICU. An echocardiogram was performed evidencing dilation of the RV with a right ventricle/left Ventricle (RV/LV) ratio greater than 1, with paradoxical movement of the interventricular septum, systolic function impairment of the right ventricle with a fractional area change (FAC) of 26%, 1.4 cm tricuspid annular plane systolic excursion (TAPSE), right ventricle outflow tract (RVOT) acceleration time of 56 ms with presence of systolic notch, consistent with increased distal vascular resistance, and mild tricuspid regurgitation with an estimate pulmonary systolic pressure (PSP) of 60 mmHg (Fig. 1). The speckle tracking method was also performed, whereby a value of -5.6% for the free-wall RV global longitudinal strain (GLS) was established (Fig. 2). A vein Doppler ultrasound of the lower limbs showed no deep vein thrombosis. Since it evolved into shock, kidney dysfunction and increased hypoxemia, endotracheal intubation and mechanical ventilation in volumen-control ventilation (VCV) mode was decided with 70% fraction of inspired oxygen (FIO2), 8 cm H₂O PEEP, 15 cm H₂O driving pressure (DP), with vasopressor support with up to 0.5 mcg/kg/min noradrenaline and inotrope with 0.375 mcg/kg/min milrinone, as well as renal replacement therapy with high-flow veno-venous hemofiltration. A new echocardiogram was carried out which showed no significant change in the 2D and Doppler mode, and continued with compromise of the right ventricular dysfunction. However, speckle tracking echocardiography evidenced an improvement in free-wall RV GLS value of − 8.1% (Fig. 3). The patient developed febrile events and purulent respiratory secretions associated with a chest X-ray showing bibasal radiopacity. A lung ultrasound scan also evidenced bibasal consolidation, so a respiratory sample was taken and empiric antibiotic treatment was started on the grounds of suspected pneumonia. Due to increased hypoxemia, it was decided to put the patient in VCV mode mechanical ventilation in prone position with 100% FiO₂, 12 cm H₂O PEEP, and 12 cm H₂O DP. A transthoracic echocardiogram was performed in prone position, placing the transducer between the mid-clavicular line and the left anterior axillary line, with the transducer indicator directed toward the left armpit, thus obtaining a 4-chamber apical view which showed a dilated RV with persistence of the septum’s paradoxical movement, FAC 40%, 2.2 cm TAPSE, a mild tricuspid regurgitation with an estimate PSP of at least 40 mmHg (Figs. 4, 5). The free-wall RV GLS value by speckle tracking improved to − 13.9%, although the vasoactive drug dose was not changed (Fig. 6). After several sessions of mechanical ventilation in prone position, patient oxygenation improved, and ventilation continued in supine position. The echocardiography parameters also got better and, eventually, normalized. During hospitalization, the patient presented intercurrent peritonitis associated with bowel perforation requiring surgery. The patient was then clinically stable, extubated after several hospitalization days, was discharged from the ICU, and later from the hospital.

Fig. 1.

Echocardiography with the patient with high-flow nasal cannula in supine position. A Parasternal short axis view showing paradoxical movement of the interventricular septum (white arrow). B Apical 4-chamber view showing RV dilation. C Measurement of TAPSE of 1.37 cm using M-mode. D Measurement of mild tricuspid regurgitation using continuous wave Doppler with an estimate PSP of 60mHg

Fig. 2.

Free-wall RV GLS by speckle tracking method with high-flow nasal cannula in supine position with a value of − 5.6%

Fig. 3.

Free-wall RV GLS by speckle tracking method in mechanical ventilation in supine position under vasopressor support with noradrenaline and inotropic support with milrinone showing a value of − 8.1%

Fig. 4.

Echocardiographic evaluation in prone position

Fig. 5.

Echocardiography with the patient in mechanical ventilation in prone position under vasopressor support with noradrenaline and inotropic support with milrinone. A Apical 4-chamber view showing RV dilation. B Measurement of TAPSE of 2.2 cm using M-mode

Fig. 6.

Free-wall RV GLS by speckle tracking method in mechanical ventilation in prone position under vasopressor support with noradrenaline and inotropic support with milrinone showing a value of − 13.9%

Discussion

The right ventricle protection approach, especially in patients with ARDS, must focus on strategies towards protective ventilation to minimize lung stress, improve oxygenation, reverse hypoxic vasoconstriction, and reduce hypercapnia [2]. In severe patients, these goals can be achieved by using the prone ventilation maneuver, causing alveolar recruitment with no overstretching and, thus, protecting both the lungs and the right ventricle [3]. It has been proven that this maneuver can reduce mortality in moderate to severe cases of ARDS, a benefit which is associated with achieving a more homogeneous pulmonary ventilation and decreasing ventilator-induced lung injury [4].

In patients with ARDS, PROSEVA study results showed that patients requiring this maneuver had fewer cardiac arrest events and more days free of cardiovascular failure, suggesting its beneficial impact on hemodynamics [5]. Prone position reduces right ventricle afterload by improving oxygenation without significantly increasing PEEP, decreasing partial pressure of carbon dioxide by making pulmonary ventilation more homogeneous, and by lowering driving pressure due to the recruitment of back regions based on severity [6].

The mechanisms of hypoxemia involved in pulmonary thromboembolism are mainly related to the modification in the ventilation/perfusion (V/Q) ratio due to mechanic and functional obstruction of the vascular bed, and to inflammation, which leads to surfactant dysfunction, collapsed lungs, and intrapulmonary shunt [7]. As soon as emboli impact on pulmonary circulation, a hypoxic vasoconstriction event is triggered, thus leading to higher pulmonary pressure, which conditions an increase in the RV afterload, its stretching, a decrease in filling pressure of the LV due to ventricular interdependence, a reduction in cardiac output, and finally, cardiogenic shock [8].

Right ventricular dysfunction is the most important mortality predictor in pulmonary thromboembolism. Therefore, early detection is of utmost importance in its management. Echocardiography continues to be the method of choice for diagnosis, considering its portability, low cost, and non-invasiveness [9]. However, it must be taken into account that some conventional parameters for its determination may be limited. Both TAPSE and the tissue S wave of the tricuspid annulus are limited in that they infer the RV global function from a part of it, thus failing to accurately represent its function when there is a discrepancy in motility with the rest of the RV regarding the tricuspid annulus.

In the past decades, speckle tracking 2D echocardiography has changed heart evaluation. The method is based on standard images in 2D mode, whereby special movements of speckles are followed over time to measure lengthening and shortening compared to its basal value. This allows for an angle-independent evaluation of the myocardial mechanics, enabling the estimation of myocardial deformation [10]. Because RV fibers are predominantly longitudinal, the longitudinal deformation of the free wall would adequately represent the RV systolic function [11]. It has been shown that speckle tracking of the RV free wall is a potentially better method to assess systolic function compared to traditional methods such as TAPSE, tissue S wave of the tricuspid annulus, and RV FAC [12]. A value lower than − 19% can be considered as normal [13].

On the other hand, hemodynamic evaluation of ventilated patients in prone position is of fundamental importance. For this, transesophageal echocardiography is considered as the ideal approach in critically ill patients. Nevertheless, the difficulties of this method must be taken into account, such as transesophageal probe availability, and the need for specific training. In view of this, transthoracic echocardiography has proved useful for hemodynamic assessment in patients ventilated in prone position [4]. To this effect, the transducer is placed at the apex beat, with the mark of the probe pointed towards the left armpit, which allows a 4 and 5-chamber apical view which, in our case, allowed us to asses not only conventional parameters, but also free-wall RV GLS by speckle tracking method.

In our patient, under high-flow oxygen cannula and supine position, free-wall RV GLS value was severely compromised at − 5.6%, which slightly improved to − 8.1% with inotropic support with milrinone, not affected later by positive pressure mechanical ventilation. With the prone position maneuver, a dramatic value improvement of − 13.9% was observed, in spite of being administered the same dose of vasopressor and inotropic support.

Our case demonstrates the beneficial impact of prone position in right ventricular dysfunction not associated with ARDS, such as pulmonary thromboembolism, checked by the speckle tracking transthoracic echocardiography. The mechanisms involved could be varied. On the one hand, in prone position, heart compression force on the back regions of the lung (largely implicated in V/Q ratio) would be eliminated. This change could lower the pressure required to obtain alveolar recruitment [14]. On the other hand, by recruiting the compressed back lung, the prone position could reduce pulmonary vascular resistance and improve oxygenation, thus easing hypoxemic vasoconstriction in the lung vascular bed [6, 15].

In our case, we must not rule out the fact that consolidation of both lung bases has contributed to hypoxemia, causing some degree of pulmonary hypoxic vasoconstriction, with the resulting increased RV afterload, which got better by performing the prone position maneuver.

To our knowledge, this is the first case described of a patient diagnosed with pulmonary thromboembolism and RV dysfunction in which the prone position maneuver was carried out due to severe hypoxia, and its beneficial impact on the RV could be demonstrated using speckle tracking echocardiography.

Conclusion

Our case shows the potential beneficial effect of the prone position maneuver in severely hypoxemic patients with right ventricular dysfunction associated with pulmonary thromboembolism evidenced by speckle tracking echocardiography.

Declarations

Conflict of interest

The authors have no relevant financial or non/financial interests to disclose.

Ethics statement

Approval for this study was waived in accordance with the local regulations because this study is a case report of a single patient and did not include protected health information, data analysis, or testing of a hypothesis, and was de-identified.

Consent to participate

Written consent was obtained from the patient before the publication of this case report.

Consent to publish

The authors affirm that patient provided informed consent for publication of the images in Figs. 1, 2, 3, and 4.

Authors contributions

Conceptualization: IC; methodology: IC; formal analysis and investigation: IC, LA, MVM; writing—original draft preparation: IC, LA, MVM; writing—review and editing: IC, LA, MVM, MB; supervision: GAB, MSS, RAG, PMM, FMT.