The patient in this case did not exhibit the symptoms indicative of chronic obstructive pulmonary disease, such as an increase in shortness of breath, sputum production, and cough. Thus, this diagnosis is unlikely. Although his ECG shows evidence of left ventricular hypertrophy and he has a history of anterior myocardial infarction, the low BNP level and the lack of volume-overload status make heart failure less likely. Severe mitral valve regurgitation is unlikely, as auscultation revealed no murmurs. The patient's laboratory results and vital signs are not indicative of sepsis.
This patient is probably experiencing an acute pseudoallergic reaction to ultrasound contrast agent (UCA). Unlike "true" allergic reactions, immunoglobulin E is not involved; also, the pathophysiology of the response is different, requiring slightly different treatment. Pseudoallergic reactions can be brief and transient or longer lasting. Recognizing this response in a patient who presents with symptoms that may initially appear puzzling is important, as it is rare and may be unexpected.
Echocardiographic technology has been improving over the past few decades. However, as many as 30% of all ultrasound studies are considered "technically difficult," often because of obesity, lung disease, increased anterior-posterior dimensions, and the rapid heart rate associated with stress echocardiography or tachycardias. UCAs were developed to help overcome these limitations.[2,3]
This patient received a microsphere contrast agent, with a lipid coating around perflutren. Other UCAs may be composed of protein microspheres around perflutren. Perflutren is an octafluoropropane gas that vibrates when it encounters ultrasound waves and returns a resonant wave that improves the signal-to-noise ratio. Earlier forms of UCAs started with a sulfur hexafluoride core, which was chosen for its inert properties, surrounded by a phospholipid bubble.[1,2,3,4,5]
Since the 1980s, UCAs have been used to enhance imaging not only by providing a first set of harmonics in resonant waves, but also by adding a second set of harmonics. Local tissues do not resonate with the ultrasound waves, which assists with the visualization of structures. UCA microspheres are typically half the diameter of red blood cells (ranging from 1 to 7 microns in diameter) and can make an initial pass through the circulation with minimal degradation. This enables the microspheres to travel from peripheral injection sites to the heart intact, without signal diminution as they traverse the pulmonary vasculature.
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Cite this: A Patient Who Collapsed in Agony After Echocardiography - Medscape - May 19, 2022.