From the Guidelines
An echocardiogram with contrast (bubble) study is appropriate when evaluating for right-to-left shunts, particularly patent foramen ovale (PFO) or atrial septal defects (ASD), as it provides real-time visualization of blood flow patterns and is more sensitive than standard echocardiography for detecting small shunts. This is supported by the study published in the Journal of the American College of Radiology 1, which highlights the utility of saline contrast echocardiography in verifying the presence of a shunt and differentiating intracardiac from extracardiac shunts.
The following clinical scenarios warrant an echocardiogram with bubble study:
- Cryptogenic stroke or transient ischemic attack, especially in patients under 55 years old, to determine if paradoxical embolism through a cardiac shunt might be the cause
- Unexplained hypoxemia that might be due to right-to-left shunting
- Migraines with aura that are refractory to medical therapy
- Divers with decompression illness to assess for potential cardiac shunts
The procedure involves injecting agitated saline solution through a peripheral vein while performing an echocardiogram; the microbubbles are normally filtered by the lungs, but in the presence of a right-to-left shunt, they can be visualized crossing into the left heart chambers. According to the study published in Chest 2, an echocardiographic contrast (“bubble”) study using agitated saline solution is warranted to detect evidence of intracardiac shunting when pulmonary arterial hypertension is known or suspected in a patient without a specific causal diagnosis.
In terms of the technical aspects, transthoracic echocardiography (TTE) remains a first-line imaging examination in adults with known or suspected congenital heart disease, providing a unique 2-D, real-time evaluation of the anatomic and hemodynamic relationships of intracardiac lesions 1. However, TTE has difficulty in consistently providing high-quality, clinically useful information in some adult patients with intracardiac defects, and transesophageal echocardiography (TEE) and MRI may be necessary in these cases.
Overall, the use of echocardiogram with contrast (bubble) study is a valuable tool in the evaluation of right-to-left shunts and should be ordered in specific clinical scenarios where the detection of small shunts is crucial.
From the Research
Appropriate Use of Echocardiogram with Contrast (Bubble) Study
- The decision to order an echocardiogram with contrast (bubble) study should be based on the presence of cryptogenic stroke or transient ischemic attack (TIA) in patients, particularly those aged ≤ 60 years 3.
- The study is useful in detecting patent foramen ovale (PFO), a potential mechanism for paradoxical embolism in cryptogenic ischemic stroke or TIA 4, 5.
- The "bubble study" is typically performed using agitated saline during echocardiography, and transesophageal echocardiography (TEE) with agitated saline contrast is considered the gold standard for detection of PFO 5.
- However, the yield of echocardiography with bubble studies among acute ischemic stroke patients may be low, especially in older patients with established stroke etiologies, and may not always lead to a change in management 3.
Patient Selection
- Patients with cryptogenic stroke or TIA, particularly those aged ≤ 55 years, are more likely to benefit from an echocardiogram with contrast (bubble) study 6, 7.
- Patients with a high-risk transient ischemic attack (TIA) or a cryptogenic acute ischemic stroke may undergo a complete diagnostic workup, including contrast transcranial Doppler (cTCD) and TEE 6.
- The "modified" Risk of Paradoxical Embolism (RoPE) score can be used to identify patients who may benefit from the study 4.