Is the blood velocity beat-to-beat variation in the descending aorta similar to the arterial pulse pressure variation?

Introduction

The beat-to-beat analysis of the arterial pulse pressure (PP) [1] and of the maximal aortic velocity measured by the transesophageal echocardiographic Doppler technique (TEE) [2] have been demonstrated as good predictors of volume responsiveness in patients with circulatory failure. However, the PP analysis requires an invasive procedure for arterial catheter placement and TEE does not allow long-term continuous analysis. Therefore, we have tested the hypothesis that the beat-to-beat variation of the peak of velocity of blood in the descending aorta (PV Ao), measured by a transesophageal echo-doppler device (a less invasive monitoring technique using a small probe) was of the same degree as the beat-to-beat PP variation measured by an arterial catheter.

Patients and methods

In 12 patients receiving mechanical ventilation, the arterial pressure curve (arterial catheter) and the descending aorta velocity signal (transesophageal echo-doppler; HemoSonic100 - Arrow Intl.) have been recorded simultaneously on a computer allowing beat-to-beat analysis of the PP and PV Ao values.

Results

Three hundred and sixty measurements were obtained (30 per patient). Six patients had atrial fibrillation, three had a sinus rhythm with numerous supraventricular extra systoles and three had a regular sinus rhythm. There was an excellent correlation between beat-to-beat PP and PV Ao variation in every patient (r = 0.85, 0.88, 0.89, 0.90, 0.92 [three times], 0.94, 0.95 [two times], 0.96 and 0.98).

Conclusion

The beat-to-beat variation of blood velocity in the descending aorta obtained by the minimally invasive transesophageal echo-doppler method is quite similar to the beat-to-beat variation of the pulse pressure. This may open a large field of clinical investigation in the perspective of detecting cardiac preload dependence and fluid responsiveness in patients under mechanical ventilation.