Figure 2
From: A Simple Method for Noninvasive Quantification of Pressure Gradient Across the Pulmonary Valve
(A) Effects of respiration on the pulmonary regurgitation jet velocity and the pulmonary valve diastolic opening. The top panel shows a 2D echocardiogram in the parasternal short-axis view at the aortic valve level from a subject in the pulmonary regurgitation (PR) method group. The middle panel depicts the Doppler flow velocity curve (DFVC) of this healthy subject with mild PR. The Doppler flow velocity curve of the middle panel was recorded at end-expiration during breath holding. The peak PR velocity was slightly less than 1 m/sec, indicating that the pressure difference across pulmonary valve (PVPG) is close to 4 mmHg based on the modified Bernoulli equation. Note that the respiration curve is flat during the breath hold (RESP). The bottom panel showed that with the onset of inspiration (insp), the PR velocity decreased sharply and became erratic at the pulmonary valve orifice (red arrow, flow signals above and below the baseline). Subsequently, at end-inspiration, pulmonary arterial pressure was equal to or less than that in the right ventricle, and a discernable forward pulmonary arterial flow was detected (green arrow, PR nearly absent), indicating natural pulmonary valve diastolic opening. The PR velocity gradually increased with expiration (exp) and the waveform nearly normalized by end-expiration (arrowhead). (B) Exaggerated inspiratory effort leads to erroneous measurement of PVPG during the Muller maneuver. The top panel shows the same view as that in A, but from a subject in the Catheterization group. The middle panel shows the DFVC with the onset of a premature flow signal (arrow) at end-diastole during gradual Muller maneuver, indicating that at 10 mmHg of negative pressure, the pressure in the pulmonary artery is just below that of the right ventricle, the pulmonary valve opens prematurely, and forward flow occurs. The bottom panel demonstrates that with an exaggerated Muller maneuver, the premature flow was more prominent and was of greater velocity (green arrow) at 12 mmHg of negative pressure, resulting in an overestimation of PVPG.
