Novel Index (PIMR) in PAH

NCT05812976 | Completed

• 1 other identifier: IRB#22-001088
• Study Type: observational
• Target: 22
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Pulmonary Hypertension

Keywords

Pulmonary Hypertension; Pulmonary Index of Microcirculatory Resistance; Pulmonary Arterial Hypertension; Index of Microcirculatory Resistance

Outcome Measures

Primary Outcomes (3)

• PAH hospitalization or all-cause mortality at 1 year

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

  1 year

• PIMR change from baseline

  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.

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

• RV-IMR

  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.

  Baseline

Study Arms (1)

PAH Patients

Pulmonary Index of Microcirculatory Resistance (PIMR) and Right Ventricle Index of Microcirculatory Resistance (RV-IMR) measurements during standard-of-care right +/- left heart catheterization at baseline and among those who undergo a standard-of-care right heart catheterization at 6 months.

Other: Pulmonary Index of Microcirculatory Resistance; Other: Right Ventricle Index of Microcirculatory Resistance

Interventions

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.

Also known as: PIMR

PAH Patients

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.

Also known as: RV-IMR

PAH Patients

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Adult PAH patients

You may qualify if:

• 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

You may not qualify if:

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

Sponsors & Collaborators

• University of California, Los Angeles: lead
• Bayer: collaborator

Study Sites (1)

Ronald Reagan UCLA Medical Center

Los Angeles, California, 90095, United States

Location

MeSH Terms

Conditions

Hypertension, Pulmonary; Pulmonary Arterial Hypertension

Condition Hierarchy (Ancestors)

Lung Diseases; Respiratory Tract Diseases; Hypertension; Vascular Diseases; Cardiovascular Diseases

Study Officials

• Rushi Parikh, MD

  University of California, Los Angeles

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: April 1, 2023
• First Posted: April 14, 2023
• Study Start: February 1, 2023
• Primary Completion: April 8, 2025
• Study Completion: April 8, 2025
• Last Updated: August 1, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)