COMPARISON OF TRANSTHORACIC ECHOCARDIOGRA PHY (VALSALVA MANEUVER) ANDTRANSESOPHAGEAL ECHOCARDIOGRAPHY (PEEP) FOR DETECTION OF PATENT FORAMEN OVALE

Preoperative detection of a patent foramen ovale (PFO) may be achieved employing either transthoracic echocardiography (TTE) with the Valsal va manoeuvre in the awake patient or trans-oesophageal echocardiograph y (TEE) in the anaesthesised patient. Our study was undertaken to vali date these methods with regard to their efficacy in identifying patien ts at risk for paradoxical air embolism (PAE). Methods. In 67 patients ranging from 28 to 70 years of age, TTE was performed utilising the V alsalva manoeuvre prior to surgery. The patients were informed about a ll procedures and agreed to take part in the study. After induction of anaesthesia the patients were evaluated with TEE in the supine and si tting positions. At end-inspiration 10 ml agitated gelatine solution ( Gelafundin) was injected through a central venous catheter into the ri ght atrium after airway pressure of 20 cm H2O had been maintained for 5 s. The injected bolus was observed throughout the ventilatory cycle, with special attention being given to early expiration and systole. A right-to-left shunt was assumed if five echo targets were observed in the left atrium. Results. The prevalence of PFO detected by TTE/Valsa lva was 9%. The diagnosis was confirmed by TEE in 2 patients in the su pine and 1 in the sitting position. An echocardiogram in these patient s showed bulging of the septum to the left, which was not seen in thos e patients in whom PFO was detected only by TTE. Discussion. The reaso n for the lower incidence of PFO detected by TEE during airway pressur e 20 cm H2O may have been an insufficient increase of pressure in the right atrium with a negative right-to-left atrial pressure gradient. A standardised ventilation manoeuvre with supra-atmospheric airway pres sure of 20 cm H2O is not sufficient. Bulging of the intra-atrial septu m from right to left during airway pressure is a possible indication o f the efficacy of the manoeuvre, regardless of the influence of the br eathing pattern.