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Assessment of pulmonary hypertension has been performed non-invasively using Doppler echo tricuspid regurgitation (TR) velocity measurement with simplified Bernoulli equation (SBE). The Doppler echo based measurement is generally considered to underestimate pulmonary arterial systolic pressure (PASP) in patients with severe TR.
We evaluated the relationship between the severities of TR and PASP in a routine clinical echo database for 5 months. To produce an exact pressure gradient matching the varying sizes and flows of TR, we have developed a heart model using an air-pressure-based regulator with an electric motor to pump water through changeable panels with various-sized orifices (2 to 21 mm in 2-3 mm intervals). We recorded the orifice area, the exact pressure generated, and trans-orifice continuous wave Doppler signals (a GE Vivid I platform). We compared the produced pressure to the SBE predictions.
A total of 2697 reports have been retrieved with various degrees of TR (no: 0.4%, more than moderate: 2.8%), made a curve of R2 Cubic=0.292, declined from moderate to severe TR. The implemented system had rising and falling time of less than 30 ms and a flat frequency response up to 28 Hz with output pressure ranges from 20 to 400 mmHg, which was enough to simulate physiologic pressure events. The generated pressure and that of SBE showed a good correlation up to 2.54 cm2(r=0.991, p<0.01); at 3.46 cm2(r=0.741, p=0.091) there was underestimation by SBE in higher pressure setting. In each fixed pressure (from 20 to 90 mmHg), early flow termination and lack of plateau was observed (3.46 cm2, 30 mmHg; 2.54 cm2, 40 mmHg). Even with a smaller orifice (1.13 cm2), a 20% underestimation was observed at 30 ms pressure duration and 70 mmHg.
In vivo, there was a decline of PASP by SBE in severe TR. In vitro, the pressure controlled pump heart model revealed a significant underestimation by SBE in the setting of severe TR (larger orifice, higher flow), and shorter application duration. Further systemized tests are needed to evaluate the novel pressure controlled heart model. The use of computational fluid dynamics can overcome the limitations of SBE especially in severe TR.
Moderated Poster Contributions
Poster Sessions, Expo North
Saturday, March 09, 2013, 3:45 p.m.-4:30 p.m.
Session Title: Pulmonary Hypertension: Physiology/Hemodynamics
Abstract Category: 27. Pulmonary Hypertension
Presentation Number: 1164M-154
- 2013 American College of Cardiology Foundation