Acute Chest Syndrome and Right Ventricular Failure
- Faraz Afzal
- Nov 8
- 5 min read
Acute Chest Syndrome and Right Ventricular Failure in a Patient with Sickle Cell Disease
Case Presentation
A man in his 40s from West Africa was admitted with diffuse pain throughout his body, including the chest. He had recently completed a long flight from Africa to Norway. On admission, he appeared clammy, in significant pain, and somnolent but easily arousable. Physical examination revealed no specific findings, but the patient appeared acutely ill and required supplemental oxygen due to hypoxia. ECG showed changes suggestive of pulmonary embolism (see more on ECG findings here and here).
CT of the head was normal, while CT thorax revealed segmental pulmonary emboli. Echocardiography demonstrated signs of pulmonary hypertension with septal flattening and a failing right ventricle. Serum lactate was elevated (4 mmol/L). The initial assessment was acute pulmonary embolism with right heart strain, and catheter-directed thrombolysis with alteplase was initiated.
However, the CT also revealed splenic infarctions and characteristic H-shaped vertebrae (so-called “H-vertebrae”), a radiological sign of repeated bone marrow infarctions. Given these findings and the patient’s ethnic background, sickle cell disease was strongly suspected. The clinical picture did not fully align with the radiologic findings - segmental emboli alone could not explain the profound hypoxia and circulatory compromise. The condition was therefore reassessed as sickle cell crisis with acute chest syndrome (ACS).
During hospitalization, the patient developed fever and was started on antibiotics. Exchange transfusion was initiated, but his condition deteriorated further with worsening hypoxia, hypotension, and signs of cardiogenic shock. Echocardiography revealed progressive right ventricular dysfunction. Central venous oxygen saturation (SvO₂) was 29%, and he was transferred to a tertiary center with ECMO capability.
Despite treatment with vasopressors and inotropes (adrenaline, noradrenaline, dobutamine), he remained unstable and was subsequently placed on VA-ECMO. Cardiac output improved markedly over the next two days, but the patient never regained consciousness. Brain MRI demonstrated extensive microbleeds and cerebral fat embolism syndrome. He later died from complications.
Acute Chest Syndrome (ACS)
ACS is defined as a new infiltrate on chest imaging accompanied by at least one of the following: fever, chest pain, cough, tachypnea, hypoxia, or dyspnea.
The pathophysiology is complex. The primary mechanism is vaso-occlusion of small pulmonary vessels by sickled erythrocytes.ACS may be triggered by:
Infection
Fat embolism from bone marrow necrosis during a pain crisis
Atelectasis or hypoventilation due to chest pain. Often, multiple mechanisms act simultaneously.
In children, infection is the most common trigger; in adults, fat embolism predominates. In this case, the acute pulmonary embolism following a long flight may have triggered the development of ACS. It can thus be viewed as a “pain crisis in the lungs,” where inflammation, hypoxia, and microembolism lead to impaired gas exchange and increased pulmonary vascular resistance.
Treatment is an emergency and includes oxygen supplementation, pain control, antibiotics, and transfusion. In cases of severe hypoxia or rapid deterioration, exchange transfusion is essential to reduce the proportion of sickled cells (HbS < 30%) and improve oxygen transport.
Hemodynamics and Right Ventricular Failure
Repeated episodes of fat embolism may cause chronic pulmonary hypertension in some patients. In this case, echocardiography showed a clearly dilated and dysfunctional right ventricle with septal flattening and reduced cardiac output. Whether this patient had pre-existing pulmonary hypertension due to prior microembolization is uncertain.
When right ventricular (RV) failure develops, blood flow through the lungs decreases, leading to reduced left ventricular (LV) filling. As systemic blood pressure falls, coronary perfusion to the RV declines. Once pulmonary artery pressure approaches or exceeds systemic pressure, the heart loses the pressure gradient required to propel blood through the pulmonary circulation - often leading to rapid hemodynamic collapse.
In such cases, mean arterial pressure (MAP) must be maintained higher than the pulmonary pressure to preserve the gradient and ensure RV perfusion. At the same time, one must avoid further increases in pulmonary vascular resistance. Noradrenaline is commonly used to raise systemic pressure but may also increase pulmonary resistance. Vasopressin is sometimes preferred as it has less pulmonary vasoconstrictive effect, although it was not used in this case.
Hypoxia and Heart Failure – A Dangerous Combination
Hypoxia and low cardiac output potentiate each other.When cardiac output falls, peripheral tissues extract more oxygen, lowering central venous oxygen saturation (SvO₂). If gas exchange in the lungs is simultaneously impaired, this blood cannot be adequately reoxygenated. The result is critically low tissue oxygen delivery - a vicious cycle that quickly progresses to circulatory collapse unless both components are corrected.
Ventilation and the Right Ventricle
As ACS progressed, the patient required non-invasive ventilation (NIV) due to worsening gas exchange from vaso-occlusion. NIV improved oxygenation but caused hypotension. The mechanism lies in the effect of positive pressure ventilation: increased PEEP raises intrathoracic pressure, which increases RV afterload. The right ventricle, designed for low resistance, tolerates this poorly. In this patient, the severely weakened RV could not tolerate volume loading either.
While moderate PEEP may benefit LV performance, it can worsen RV failure. Thus, oxygenation must be balanced against the risk of increased afterload. The patient became increasingly confused, and airway protection was a concern. Normally, such deterioration would lead to intubation - but in this case, intubation could have been catastrophic, as it would further elevate intrathoracic pressure and RV afterload, precipitating cardiovascular collapse.
ECMO – When Neither Heart Nor Lungs Can Cope
Ultimately, the patient was placed on VA-ECMO (veno-arterial ECMO), a device that temporarily takes over the function of both heart and lungs. Blood is drained from a vein, oxygenated through a membrane lung, and pumped back into the arterial system.
While VV-ECMO supports only gas exchange, VA-ECMO provides both circulatory and respiratory support. It unloads the failing heart, maintains perfusion and blood pressure, and buys time for recovery or further therapy (e.g., LVAD or transplantation).
In this case, ECMO markedly improved circulation, but cerebral injury was irreversible. MRI revealed widespread microbleeds and fat embolism to the brain—a known but feared complication of sickle cell crisis.
Learning Points
Segmental pulmonary emboli do not always explain severe hypoxia and circulatory failure. In patients of African origin, consider sickle cell crisis or ACS.
ACS can be triggered by infection, fat embolism, hypoventilation, or vaso-occlusion—often in combination.
Exchange transfusion reduces the proportion of sickled erythrocytes and improves oxygen delivery.
Hypoxia plus RV failure is a life-threatening combination—both must be addressed simultaneously.
NIV and intubation may improve oxygenation but can increase RV afterload.
In severe pulmonary hypertension, MAP must remain higher than PAP to preserve coronary perfusion in RV and prevent collapse.
VA-ECMO is the final option when neither oxygenation nor circulation can be maintained by conventional therapy.
Summary
This case illustrates how sickle cell disease can lead to a dramatic and rapidly fatal course when acute chest syndrome and pulmonary hypertensiom occur simultaneously. It also highlights the close interdependence between the respiratory and circulatory systems - and how quickly this balance can unravel when the right ventricle fails.
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