I will start by thanking those who shared their ideas on the diagnosis of the retrocardiac structure and will allow myself to suggest why it is unlikely to be a thrombosed left superior vena cava (which I grant you is a very attractive idea), or a thombosed coronary sinus. First, the diameter is too large, close to the diameter of the left ventricle. Second, the contents of this structure appear heterogeneous and mobile which may not be easily appreciated due to the low resolution of the video.
The correct diagnosis is: Hiatal hernia
CT images show nicely this hernia with air and fluid inside it and the typical gastric rugae.(images 1 and 2 below).
Nishimura et al. were the first to report that hiatal hernia can simulate a left atrial mass on 2-dimensional echocardiographic imaging by encroaching on the posterior aspect of the left atrium, and sometimes posterior to the left atrio-ventricular junction (ref.1).
In addition to it being an echocardiographic curiosity this condition has been associated with cardiac symptomatology namely dyspnea and postprandial syncope.
There is a recent report on 30 patients who were planned to undergo surgical correction of large hiatal hernias. These patients underwent pulmonary function and exercise testing before and after the surgery as well as contrast CT angiography. The decision to perform the surgery had been taken prior to the testing and was not influenced by the findings.(ref.2)
Exertional dyspnea was present in 25 of 30 patients (83%) despite normal mean baseline respiratory function. Moderate to severe LA compression was qualitatively present in 23 of 30 patients (77%) on computed tomography. Of note one liter of water was orally ingested to distend the hernia before image acquisition. Right and left inferior pulmonary vein and coronary sinus compression was present in 11 of (40%), and 26 of 30 (87%) patients, respectively.
Post-operatively, New York Heart Association functional class and exercise capacity improved significantly and METs [percentage predicted]: 75 ± 24% vs. 112 ± 23%, p 0.001) and resolution of cardiac compression was observed. Absolute change in LA diameter on the echocardiogram was the only independent cardiorespiratory predictor of exercise capacity improvement post-operatively. The results of this study provide evidence of left atrial, pulmonary venous, and coronary sinus compression by large hiatal hernias, with improvement of left ventricular and left atrial dimensions, as well as a normalization of atrial inflow velocities after surgery.
Others have suggested consideration be given to extrinsic compression when syncope or dyspnea are provoked by lying down, typically after a large meal. In this circumstance, distention of the hernial sac by fluid loading before testing, may be a valuable “stress test.”(ref.3).
In conclusion, this finding is not uncommon and whenver you see a mass especially containing fluid in motion think about hiatus hernia.
I hope you found this case interesting and informative.
1. Diaphragmatic hernia mimicking an atrial mass: a two-dimensional echocardiographic pitfall. Nishimura RA, Tajik AJ, Schattenberg TT, et al. J Am Coll Cardiol 1985; 5:992.
2. Left Atrial Compression and the Mechanism of Exercise Impairment in Patients With a Large Hiatal Hernia . Christopher Naoum, MBBS, Gregory L. Falk, MBBS, Austin C. C. Ng, MBBS, MMED,
Tony Lu, MBBS, Lloyd Ridley, MBBS, Alvin J. Ing, MD, Leonard Kritharides, MBBS, PHD, John Yiannikas, MBBS J Am Coll Cardiol 2011; 58:1624–34.
3. Echocardiographic Aspects of Hiatal Hernia: A Review. Rami N. Khouzam, MD, Asif Akhtar, MD, Daniel Minderman, RDCS, Jacqueline Kaiser, RDMS, RDCS, Ivan A. D’Cruz, MD, FRCP J Clin Ultrasound 35:196–203, 2007