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Assessing the kinetics of microbubble appearance in cirrhotic patients using transthoracic saline contrast-enhanced
Adriano R Tonelli1, Tawfeq Naal2, Wael Dakkak3
1Department of Pulmonary, Allergy and Critical Care Medicine, Respiratory Institute, Cleveland Clinic, Cleveland, OH, USA.
Insights
Echocardiography can help exclude significant intrapulmonary shunts in cirrhosis patients. Observing microbubbles in the left heart within seven cycles suggests a shunt fraction below 3%.
Area of Science:
- Cardiology
- Pulmonology
- Radiology
Background:
- Hepatopulmonary syndrome (HPS) is a complication of advanced liver disease.
- Accurate assessment of intrapulmonary shunts is crucial for diagnosing and managing HPS.
Purpose of the Study:
- To determine the number of cardiac cycles needed during echocardiography to exclude significant intrapulmonary shunts in patients with cirrhosis.
- To correlate echocardiographic microbubble detection with radionuclide shunt fraction measurements.
Main Methods:
- Retrospective analysis of 64 patients with cirrhosis who underwent technetium-99m-labeled macroaggregated albumin scanning.
- Assessment of microbubble appearance kinetics in the left atrium and left ventricle during transthoracic echocardiography after agitated saline injection.
Main Results:
- A shunt fraction less than 3% was associated with no microbubble detection by the 7th cardiac cycle.
- Earlier microbubble appearance in the left heart chambers correlated with higher shunt fractions and more severe hypoxemia (arterial oxygen <60 mm Hg).
- The number of heart cycles before microbubble appearance was inversely associated with the nuclear scanning shunt fraction (R = -0.42 to -0.46).
Conclusions:
- Echocardiography, by observing microbubble transit, can effectively help exclude significant intrapulmonary shunts in cirrhosis patients.
- In patients with suspected HPS, a shunt fraction above 3% is indicated by microbubble detection within the first seven cardiac cycles.
Background:
The number of cardiac cycles that need to be reviewed by echocardiography before a significant intrapulmonary shunt can be excluded remains unclear.
Methods:
We retrospectively identified patients with cirrhosis who underwent technetium-99 m-labeled macroaggregated albumin scanning. The kinetics of bubble appearance after the injection of agitated saline during transthoracic echocardiograms were assessed in these patients.
Results:
For the 64 eligible patients, the mean ± SD age was 56 ± 9 years. The median (IQR) shunt fraction by radionuclide scanning was 7.7% (2.8%-19.9%). Microbubbles were seen in the left atrium (LA) and left ventricle (LV) at a median (IQR) of 4 (2-5) and 4 (2-5) beats, respectively. The number of heart cycles before microbubbles appeared in the LA or LV was inversely associated with the nuclear scanning shunt fraction (R = -0.42, P = .001, R = -0.46, P < .001, respectively). If no microbubbles were detected by heart cycle 7, the shunt fraction was uniformly less than 3%. Patients with arterial oxygen <60 mm Hg, compared to ≥60 mm Hg, had earlier appearance of microbubbles in the left heart chambers (2.6 ± 1.9 vs 4.0 ± 2.3 beats, P = .046).
Conclusions:
In patients with advanced cirrhosis suspected of having hepatopulmonary syndrome, a greater shunt fraction during nuclear scanning was associated with more pronounced hypoxemia and a prompt and more intense appearance of microbubbles in the left-sided heart chambers. Patients with a shunt fraction above 3% have microbubbles in the LA or LV at some point during the first seven heart cycles.
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