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Abstract
Optimal contrast within the pulmonary artery is achieved by the maximum amount of contrast-enhanced blood flowing through the superior vena cava (SVC), while minimum amounts of non-contrasted blood should originate from the inferior vena cava (IVC). This study aims to clarify whether "suction against resistance" might optimise this ratio.
Phase-contrast pulse sequences on a 1.5T MRI magnet were used for flow quantification (mean flow (mL/s), stroke volume (Vol) in the SVC and IVC in volunteers. Different breathing manoeuvers were analysed repeatedly: free breathing; inspiration; expiration; suction against resistance, and Valsalva. To standardise breathing commands, volunteers performed suction and Valsalva manoeuvers with an MR-compatible manometer.
Suction against resistance was associated with a significant drop of the IVC/SVC flow quotient (1.63 [range 1.3-2.0] p<0.05 at -10 mmHg and 1.48 [1.1-1.9] p<0.01 at -20 mmHg) corresponding to increased blood flow from SVC and diminished flow originating from the IVC. The remaining breathing commands (free breathing 2.2; inspiration 2.4; expiration 2.4; Valsalva 10 mmHg 2.3; Valsalva 20 mmHg 2.6; and Valsalva 30 mmHg 2.2) showed no differences (p>0.05).
Suction against resistance caused a significant drop in the IVC/SVC quotient. Theoretically, this breathing manoeuver might significantly improve the enhancement characteristics of CT angiography.
* Suction provokes reduction in blood flow in the inferior vena cava.
* Ratio between the inferior and superior vena cava blood flow diminished during suction.
* Manometer used during breathing standardises MR phase-contrast blood flow measurements. [PUBLICATION ABSTRACT]