Simultaneous real-time flow dynamics in the azygos vein and descending aorta during physiological stress

Zielsetzung:

Aim of this study was to measure blood flow in the descending aorta (AD) and azygos vein (Az) using Mueller maneuver (MM) as physiological stress test in real-time cardiac magnetic resonance imaging technique (RT-CMR) using a further development of established fast low-angle shot (FLASH) sequence with high temporal and spatial resolution.

Material und Methodik:

Blood flow was measured in n = 20 healthy volunteers in the AD and Az simultaneously with RT-CMR including an image acquisition of 40 ms and under-sampled radial FLASH. The volunteers were instructed to perform MM (“reversed” Valsalva maneuver) in comparison to normal breathing phases.

Ergebnisse:

At the beginning of MM, flow per heartbeat (hb) in the AD (56 ± 9.4 ml/hb) decreased significantly (p.< 001) (to 46±10.4ml/hb ˜ 82%±13ml/hb at early strain). In the Az flow per heartbeat increased significantly (p < 0.01) during MM (normal breathing 1.8±1.5ml/hb vs. early strain 5.5±3.6ml/hb ˜ 309%±555ml/hb). Heart rate increased significantly (p.< 001) during MM (normal breathing 74±9.9 bpm vs. early strain 79±12.6 bpm ˜ 108%±8 bpm). Average peak velocity decreased significantly (p < 0.01) in AD (normal breathing 62±11.8cm/s vs. early strain 52±11.6cm/s ˜ 84%±10cm/s) and increased significantly (p < 0.1) in the Az (normal breathing 16±4.4cm/s vs. early strain 25±8.4cm/s ˜ 162%±56cm/s). Average area in AD (p < 0.01) and Az (p < 0.5) increased during MM.

Schlussfolgerungen:

RT-CMR using undersampled FLASH reliably and simultaneously determines flow dynamics during physiological stress and normal breathing over two different vessel areas. Compared to routinely used Cine-CMR it is able to show single heart beat-to-beat variability without interpolation. Even in small vessels flow can be measured.

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