What is the clinical significance of agitated saline contrast (ASC) intrapulmonary shunting?

From the Guidelines

Agitated saline intrapulmonary shunting is a clinically significant finding that indicates the presence of abnormal vascular communications, allowing blood to bypass normal gas exchange in the lungs, and is most commonly associated with pulmonary arteriovenous malformations (PAVMs). This condition can lead to potential complications such as paradoxical embolism, hypoxemia, and hemoptysis, as noted in the context of congenital heart disease management 1. The clinical significance of agitated saline intrapulmonary shunting lies in its ability to identify these abnormal communications, which can be crucial for preventing further complications. When detected during echocardiography with agitated saline contrast, intrapulmonary shunts are distinguished from intracardiac shunts by the delayed appearance of bubbles in the left heart, typically after 3-6 cardiac cycles. Key points to consider in the management of patients with agitated saline intrapulmonary shunting include:

• The need for further evaluation with CT angiography or pulmonary angiography to characterize the lesions
• Treatment recommendations for PAVMs with feeding vessels ≥3mm in diameter, typically through transcatheter embolization rather than medication, as suggested by guidelines for managing adults with congenital heart disease 1
• The importance of antibiotic prophylaxis for procedures with risk of bacteremia and counseling about the increased risk of neurological complications, particularly in patients with coexisting conditions that increase thrombotic risk. Overall, the detection of agitated saline intrapulmonary shunting has significant implications for patient management and outcomes, emphasizing the need for careful evaluation and appropriate intervention to mitigate potential complications.

From the Research

Clinical Significance of Agitated Saline Intrapulmonary Shunting

The clinical significance of agitated saline intrapulmonary shunting is a crucial aspect of diagnosing and managing various cardiovascular and pulmonary conditions.

• Agitated saline intrapulmonary shunting can be used to detect right-to-left shunts, which can lead to severe neurologic complications due to paradoxical embolization 2.
• The use of agitated saline contrast injection with transthoracic echocardiography can help diagnose intrapulmonary arteriovenous shunting, as seen in a case study where a 54-year-old man with end-stage cirrhosis of the liver presented with dyspnea 3.
• Small pulmonary shunts on saline transthoracic contrast echocardiography (TTCE) may lack clinical implications, as they are not associated with an increased risk for neurologic complications and represent pulmonary arteriovenous malformations too small for subsequent endovascular treatment 2.
• Point-of-care ultrasound (POCUS) with agitated saline bubble study can be used for early diagnosis of right-to-left cardiopulmonary shunts, allowing for expedited therapy in critically-ill perioperative patients 4.

Detection and Diagnosis

• Agitated saline contrast imaging can be used to detect right-to-left atrial communication, with a high sensitivity and specificity when compared to transesophageal echocardiography 5.
• The use of provocative maneuvers, such as the Valsalva maneuver, can increase the detection rate of right-to-left shunts 4, 6.
• Transthoracic echocardiographic agitated saline contrast injection (ASCi) is a simple and highly accurate method for detecting right-to-left atrial communication, and is recommended as the primary diagnostic tool for detecting patent foramen ovale (PFO) in clinical practice 5.

Clinical Implications

• Pulmonary shunting carries the risk for severe neurologic complications due to paradoxical embolization, and antibiotic prophylaxis is advised in case of any pulmonary shunt on saline TTCE to prevent brain abscesses after procedures with risk for bacteremia 2.
• In patients with hereditary hemorrhagic telangiectasia (HHT), additional chest computed tomography is recommended in case of any pulmonary shunt detected on saline TTCE, to evaluate the feasibility for transcatheter embolotherapy of pulmonary arteriovenous malformations 2.
• The detection of right-to-left shunts using agitated saline contrast imaging can have significant clinical implications, including the diagnosis of intrapulmonary arteriovenous shunting and the detection of PFO, which can lead to embolic events in younger patients 3, 5.