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Completed

NCT Number: NCT05812976

Novel Index (PIMR) in PAH

The chief regulator of resistance in pulmonary arterial hypertension (PAH) is the small arteries. In the heart, the invasive measurement of the resistance of the small arteries has been shownto be safe, easy, reliable, and prognostic. This study is intended to translate prior work in heart arteries to the PAH space and invasively measure the resistance of the small arteries of the lung (pulmonary index of microcirculatory resistance [PIMR]) and the coronary artery supplying the right ventricle (acute marginal of the RCA; RV-IMR). Importantly, these measurements will be made during standard of care cardiac catheterizations (right heart catheterization [RHC] +/- left heart catheterization). The correlation between these new indices and the standard ones measured during RHC typically used to determine the severity of pulmonary hypertension will be analyzed. In addition, among newly diagnosed patients, the study will evaluate how these indices change 6 months after starting treatment. Finally, the association of these indices with clinical outcomes at 1 year will be assessed. The findings from this study may deliver an immediate impact to patient care by identifying a new metric to help better identify those who may benefit from a more intensive, personalized treatment regimen.

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Key information

Conditions

Pulmonary Hypertension Cardiovascular Diseases Hypertension Hypertension, Pulmonary Lung Diseases Pulmonary Arterial Hypertension Respiratory Tract Diseases Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Ronald Reagan UCLA Medical Center

Los Angeles, California, 90095, United States

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Diagnosis of Group 1 PAH with invasive pulmonary hypertension defined as: Mean pulmonary arterial pressure ≥ 20 mmHg, pulmonary capillary wedge pressure < 15 mmHg, and pulmonary vascular resistance ≥ 3 Wood units.
  • Serum creatinine < 2.0 mg/dL
  • Able to provide informed written consent

Exclusion criteria

  • Other groups/forms of pulmonary hypertension (i.e. groups 2-5)
  • Contraindicated to undergo fluoroscopy and/or coronary angiography
  • Pregnancy

Treatment and study plan

Pulmonary Index of Microcirculatory Resistance

Other

PIMR measurement involves placing a coronary pressure wire in the pulmonary arteries and making pressure/time measurements during maximal flow down the artery.

Other names: PIMR

Right Ventricle Index of Microcirculatory Resistance

Other

RV-IMR measurement involves placing a coronary pressure wire in the acute marginal branch of the right coronary artery and making pressure/time measurements during maximal flow down the artery.

Other names: RV-IMR

Primary outcomes

  1. PAH hospitalization or all-cause mortality at 1 year

    Time frame: 1 year

    The primary outcome is the composite of PAH hospitalization or all-cause mortality at 1 year.

  2. PIMR change from baseline

    Time frame: Baseline, 6 months only if repeat RHC as standard of care

    PressureWire advanced to distal third of segmental pulmonary artery (PA) for measurement of pulmonary hemodynamics. The derivation of IMR involves the application of Ohm's law (V=IR) to the coronary microcirculatory circuit, where the relationship between resistance (R) = IMR, voltage (V) = pressure (P), and current (I) = flow (Q) can be expressed as follows: IMR = ∆P/Q. ∆P = the change in pressure across the microvasculature (mean distal coronary artery pressure [Pd] - coronary venous pressure (Pv); Pv is typically disregarded because it is negligible relative to Pd. Based on the principles of thermodilution, flow is inversely proportion to mean transit time (Q ~ 1/Tmn). Lastly, the minimal achievable resistance occurs during maximal hyperemic flow when all available microvessels have theoretically been recruited. Hence, the calculation of IMR simplifies to the following formula: IMR = Pd (pulmonary artery) x TmnHyp.

  3. RV-IMR

    Time frame: Baseline

    PressureWire advanced to distal third of acute marginal branch of the right coronary artery (RCA) for measurement of pulmonary hemodynamics. The derivation of IMR involves the application of Ohm's law (V=IR) to the coronary microcirculatory circuit, where the relationship between resistance (R) = IMR, voltage (V) = pressure (P), and current (I) = flow (Q) can be expressed as follows: IMR = ∆P/Q. ∆P = the change in pressure across the microvasculature (mean distal coronary artery pressure [Pd] - coronary venous pressure (Pv); Pv is typically disregarded because it is negligible relative to Pd. Based on the principles of thermodilution, flow is inversely proportion to mean transit time (Q ~ 1/Tmn). Lastly, the minimal achievable resistance occurs during maximal hyperemic flow when all available microvessels have theoretically been recruited. Hence, the calculation of IMR simplifies to the following formula: IMR = Pd (RCA marginal branch) x TmnHyp.

Sponsors and collaborators

Lead sponsor

University of California, Los Angeles

Other

Collaborators

  • Bayer

Registry information

Official study title

Impact of the Pulmonary Index of Microcirculatory Resistance in Pulmonary Arterial Hypertension

Important dates

Study start
2023
Primary completion
2025
Study completion
2025
First posted
Apr 14, 2023
Registry last updated
Aug 1, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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