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Feasibility of Routine Pulmonary Arterial Impedance Measurements in Pulmonary Hypertension: Pharmacologic Interventions

Inhaled NO therapy decreased Ppa and PVR, while Q, HR, and Psa remained unaffected. Z0, Z1; and Zc decreased, while Fmin, phase indexes, and RF were unchanged (Table 2). Epoprostenol therapy decreased PVR and Psa, increased Q, while HR remained unaffected, and decreased Z0, Z1, and Zc, while Fmin, phases indexes, and RF were unchanged (Table 2). Dobutamine therapy increased Q, HR, and Ppa, did not affect Psa, and decreased PVR and Z0, while Z1, Zc, Fmin, and phase indexes remained unaffected (Table 2). Figures 1 to 3 illustrate the typical PVZ spectra modifications observed with each intervention. Source

Discussion
The present results show that it is possible to analyze Ppa and flow waves obtained during routine right heart catheterization with thermodilution fluid-filled pulmonary artery catheters and concomitant transthoracic Doppler echocardiography. Derived PVZ spectra are realistic, as they were similar to those previously reported with sophisticated high-fidelity equipment, and were sensitive to pharmacologic interventions.
Right heart catheterization for the diagnosis and therapeutic follow-up of PAH patients in clinical practice relies on measurements of mean flow (by thermodilution or the Fick method) and mean Ppa, and on the derived PVR calculations. This “steady-flow” hemodynamic approach neglects the natural pulsatility of the pulmonary circulation, and the pressure and wave morphology changes induced by the disease. The rationale for using the steady-flow hemodynamic approach is its simplicity, the inherent technical limitations of commercially available catheters, and the fact that the pathologic changes in PAH patients are essentially limited to the small resistive pulmonary arteries, to which PVR is sensitive. In addition, the quantification of pressure and waveform morphology requires a mathematical analysis, with results expressed in the frequency domain unfamiliar to clinicians. The frequency response of fluid-filled catheters is thought to be insufficient for accurate instantaneous pressure measurements anyway.
Table 2—Hemodynamic Effects of Pharmacologic Interventions in 22 Patients With PAH

Variables

Baseline

NOt

Baseline

Epoprostenolj

Baseline

Dobutamine§

HR, ppm

84 ± 3

81 ± 3|

86 ± 3

90 ± 4

85 ± 3

101 ± 5|

Psa, mm Hg

88 ± 3.1

92 ± 2.9

81 ± 2.2

59 ± 3.1|

90 ± 5.1

87 ± 5

Ppa, mm Hg

60 ± 2.3

56 ± 2.4|

56 ± 1.9

53 ± 3.4

56 ± 3.6

65 ± 4.6|

Q, L/min

3.5 ± 0.22

3.6 ± 0.28

3.7 ± 0.39

5.3 ± 0.81|

3.6 ± 0.38

5.1 ± 0.55|

PVR, wood units

15.3 ± 1.4

13.7 ± 1.5|

11.7 ± 1.1

8.1 ± 1.3||

17.2 ± 2.3

14.1 ± 1.5|

Z0, dyne-s-cm

1,463 ± 138

1,345 ± 141|

1,208 ± 103

820 ± 124|

1,376 ± 221

1,097 ± 165|

Z1, dyne-s-cm

292 ± 23

255 ± 22|

258 ± 25

190 ± 20|

267 ± 26

262 ± 35

Z1 phase, rad

– 0.93 ± 0.06

– 1.03 ± 0.06

– 0.9 ± 0.1

– 0.9 ± 0.1

– 0.9 ± 0.1

– 0.8 ± 0.1

Zc, dyne-s-cm

124 ± 14

103 ± 10|

90 ± 6

73 ± 10|

99 ± 11

104 ± 15

Fmin, Hz

6.5 ± 0.5

6 ± 0.3

5.9 ± 0.4

5.7 ± 0.5

6.5 ± 0.8

6.7 ± 0.5

F0 crossing, Hz

7 ± 0.9

6.5 ± 0.7

5.5 ± 0.8

4.6 ± 0.6

7.9 ± 1.6

6.1 ± 0.7

RF

0.837 ± 0.001

0.848 ± 0.012

0.859 ± 0.009

0.836 ± 0.012

0.854 ± 0.017

0.819 ± 0.02|