NON-SMOKE SPONTANEOUS CONTRAST IN LEFT ATRIUM INTENSIFIED BY RESPIRATORY MANEUVERS - A NEW TRANSESOPHAGEAL ECHOCARDIOGRAPHIC OBSERVATION

Objective-To elucidate why different types of contrast appear in the l eft atrium during transoesophageal echocardiographic contrast studies. This should lead to a more uniform definition of true patent foramen ovale. Background-The Valsalva manoeuvre and cough are routinely used to enhance right to left shunt for the detection of patent foramen ova le. No information is, however, available on the effect of these manoe uvres on the intrinsic echogenicity of blood in the left atrium. Metho ds-30 consecutive patients referred for transoesophageal echocardiogra phy were studied. Gain settings were relatively high so that no detail s were lost. The appearance of contrast during normal respiration, cou gh, and the Valsalva manoeuvre was looked for in the left atrium with and without venous injection of 10 ml of 5% dexbrose. Frequency of con trast appearance in the left atrium was expressed as a percentage. Int ensity of contrast, when present, was graded 1 (mild), 2 (moderate), o r 3 (equal to right atrial contrast during injection). Timing was asse ssed in cardiac cycles after the end of respiratory manoeuvres. Result s-Left atrial contrast appeared as a ''snowstorm'' flowing from the ri ght pulmonary veins towards the middle of the left atrium. It was pres ent respectively with and without contrast injection in eight and five patients during normal respiration, in 15 and seven during a cough, a nd in 20 and 14 during the Valsalva manoeuvre. When present, the mean intensity of contrast was 1.0 during normal respiration, 1.4 during a cough, and 1.4 during the Valsalva manoeuvre. The mean delay of contra st appearance was 3-4 cycles after release of the Valsalva manoeuvre a nd after onset of cough. Conclusions-Respiratory manoeuvres frequently induce the transient appearance of mild to moderate contrast in the l eft atrium, most often independently of venous injections. Mild contra st was seen only with high gain settings. This contrast is likely to b e related to transient stasis in the pulmonary circulation. In some ca ses peripheral venous injections of dextrose solution produced, withou t any respiratory manoeuvre, a similar contrast after the first four c ardiac cycles of the right atrium filling, which is likely to represen t recirculation of the injected bolus through the pulmonary capillary bed. Therefore respiratory manoeuvres should always be performed befor e contrast injections to allow better distinction between this backgro und and true patent foramen ovale or pulmonary arteriovenous fistula.