B1. Feasibility of combined Doppler-ECG assessment of internal jugular veins.

INTRODUCTION: Studying the venous compartment may add valuable information on background mechanisms and (patho)physiology of the cardiovascular system in normal pregnancies and pregnancies complicated by preeclampsia. Every component of the venous pulse wave is reflecting a specific stage of the cardiac cycle in the right atrium, and can be recognized in the neck veins, the hepatic and the renal veins. Previous studies have demonstrated the repeatability and reproducibility of venous Doppler sonography and venous pulse transit time in renal interlobar and hepatic veins. In this study we focus on the Doppler assessment of the triphasic pulse wave in the internal jugular vein, the easily accessible vein between brain and right atrium of the heart.

METHODS: A standardized combined Doppler-ECG technique was used for measurement of the triphasic waveform characteristics in the internal jugular vein. Similar to reported studies in renal interlobar and hepatic veins, the following parameters were measured: flow velocities at ''A''-, ''X''-, ''V''- and ''Y''-peak, the venous impedance index ([X - A]/X) and the time relation between the ''P'' (ECG) & ''A'' and the ''R'' (ECG) & ''X''. The examination was performed at three different locations: (1) the right proximal, (2) the right distal and (3) the left proximal internal jugular vein. At each location, six measurements were performed by two ultrasonographers in 23 randomly selected women (almost all pregnant). For the evaluation of inter and intra rater agreement a mixed model was used (Barnhart 2007). A bootstrap experiment was used to evaluate the stability of the averaged values. To illustrate this combined Doppler-ECG assessment of the internal jugular vein, a three-minute English spoken video sequence has been recorded.

RESULTS: The Concordance Correlation Coefficient was >0.6 for all the parameters at the three locations, with exception of the inter rater agreement of the ''X''-, ''V''- and ''Y'' peak in the right and left proximal internal jugular vein and the intra rater agreement of the ''X''-peak in the left proximal internal jugular vein of one of both raters (Table 1). The bootstrap experiment showed that four measurements are sufficient to obtain stable values (no further decrease of the standard deviation by additional measurements).

CONCLUSION: Combined Doppler-ECG assessment is a simple, safe, easily accessible and noninvasive bed-side technique to measure the venous waveform characteristics in the internal jugular vein. Statistical models showed for most parameters an acceptable inter and intra rater agreement for averaged 4-point values at all three locations.