Background The respiratory variation (RV) in inferior vena cava (IVC) caliber is routinely evaluated on echo for assessment of systemic venous congestion. In obese patients or in those who have recently undergone abdominal or thoracic surgery, IVC visualization can be difficult. We assessed whether RV in the right subclavian vein (RSV) caliber can serve as a surrogate for the RV in the IVC and whether the correlation would be better with the imaging performed in supine position or at a 458 reclining position.
Methods In 40 patients, IVC long axis echocardiograms were recorded for 10 beats with patient breathing normally. M-mode recordings were made of the IVC segment 2 to 4 cm inferior to the entry of the IVC into the right atrium, and the minimum (MIN) and maximum (MAX) IVC diameters were obtained. RSV was visualized from the right supraclavicular region. Two-dimensional recordings were made over 10 beats during normal quiet respiration in the supine and in the 458 reclining position; MIN and MAX diameters were obtained and ratio calculated. Correlation between ratio of the MIN to MAX IVC caliber and ratio of RSV MIN to MAX caliber was tested by statistical analysis.
Results The mean ratio of respiratory variation of IVC caliber was different from the mean ratio of the respiratory variation in the RSV in the supine position but not from the mean ratio of the respiratory caliber variation in the RSV at 458 position. Using the paired t-test, the IVC respiratory variation correlated better with the RSV respiratory variation in the 458 reclining position.
Conclusions Respiratory variation in RSV caliber at 458 correlates well with the IVC respiratory variation and can be used for noninvasive assessment of systemic venous congestion if the IVC cannot be visualized well due to obesity, recent surgery, or other reasons.
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