Background: Intraatrial electrocardiography (ECG) is a well-established method for central-venous catheter (CVC) placement and an intraatrial position is assumed, when a significantly increased P-wave is registered. However, an increase in P-wave amplitude also occurs in other positions. Therefore we evaluated CVC tip positioning by means of transesophageal echocardiography (TEE) at a maximum P-wave amplitude.
Patients and methods: In this prospective randomized study the right or left internal jugular vein was cannulated with 100 patients in each group and catheter tip positioning was guided by means of ECG. The catheter was fixed at the position of maximum P-wave amplitude and the insertion depth was registered. The relationship of the CVC tip position to the superior edge of the crista terminalis was demonstrated with the help of TEE.
Results: In all patients the catheter tip was found +/- 0.5 cm from the superior edge of the crista terminalis at the transition from the superior vena cava to the right atrium. On x-ray control, all catheters ran along the length of the vessel wall of the superior vena cava.
Conclusions: A maximum P-wave is derived even at the entrance to the right atrium. This explains why ECG-guided CVC placement -- based on the largest P-wave amplitude -- consistently resulted in correct positioning of the CVC tip at the transition from the superior vena cava to the right atrium.