Pulmonary HypertensionNCT05812976
Novel Index (PIMR) in PAH
An observational study of Pulmonary Hypertension, run by University of California, Los Angeles at 1 site in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Pulmonary Hypertension
- What is being tested?
- Pulmonary Index of Microcirculatory Resistance and Right Ventricle Index of Microcirculatory Resistance
- How many people
- 22 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Feb 2023to 8 Apr 2025
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: Adult PAH patients
Who may be able to join
- 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
Who cannot join
- Other groups/forms of pulmonary hypertension (i.e. groups 2-5)
- Contraindicated to undergo fluoroscopy and/or coronary angiography
- Pregnancy
Trial locations and contacts
1 site in 1 country.
United States1 site
Ronald Reagan UCLA Medical Center
Los Angeles, California, 90095
About this study
Official title: Impact of the Pulmonary Index of Microcirculatory Resistance in Pulmonary Arterial Hypertension
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
- Being tested
- Pulmonary Index of Microcirculatory Resistance, Right Ventricle Index of Microcirculatory Resistance
- Keywords
- Pulmonary Hypertension, Pulmonary Index of Microcirculatory Resistance, Pulmonary Arterial Hypertension, Index of Microcirculatory Resistance
- Medical subject headings
- Hypertension, Pulmonary, Pulmonary Arterial Hypertension
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Pulmonary Index of Microcirculatory ResistanceOther
Also called PIMR
PIMR measurement involves placing a coronary pressure wire in the pulmonary arteries and making pressure/time measurements during maximal flow down the artery.
Right Ventricle Index of Microcirculatory ResistanceOther
Also called RV-IMR
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.
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: Other: Pulmonary Index of Microcirculatory Resistance; Other: Right Ventricle Index of Microcirculatory Resistance |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: 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.
Measured: 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.
Measured: Baseline
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted14 Apr 2023
- Study start1 Feb 2023
- Primary completion8 Apr 2025
- Study completion8 Apr 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Pulmonary HypertensionStudies of the same condition, open and under way.
- More trials run by University of California, Los AngelesThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 22 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of California, Los Angeles
- Sponsor type
- University, hospital or other
- Collaborators
- Bayer
- Responsible party
- Principal investigator, Rushi V. Parikh, University of California, Los Angeles
- Investigators
- Rushi Parikh, MD, Principal investigator, University of California, Los Angeles
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05812976
- Sponsor's protocol ID
- IRB#22-001088
- Status last verified
- Jul 2025
- First submitted
- 1 Apr 2023
- Last updated
- 1 Aug 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 1 Aug 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Impact of the Pulmonary Index of Microcirculatory Resistance in Pulmonary Arterial Hypertension
- ClinicalTrials.gov ID
- NCT05812976
- Acronym / sponsor ID
- IRB#22-001088
- Conditions
- Pulmonary Hypertension
- Keywords
- Pulmonary Hypertension, Pulmonary Index of Microcirculatory Resistance, Pulmonary Arterial Hypertension, Index of Microcirculatory Resistance
- Study type
- Observational
- Recruitment status
- Completed
- Enrolment
- 22 participants (actual)
- Lead sponsor
- University of California, Los AngelesUniversity, hospital or other
- Collaborators
- Bayer
- Study start
- 1 Feb 2023 (actual)
- Primary completion
- 8 Apr 2025 (actual)
- Study completion
- 8 Apr 2025 (actual)
- First posted
- 14 Apr 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| PAH Patients | – | Other: Pulmonary Index of Microcirculatory Resistance, Other: Right Ventricle Index of Microcirculatory ResistancePulmonary 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. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- Adult PAH patients
Key inclusion criteria (3 listed)
- 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
Key exclusion criteria (3 listed)
- Other groups/forms of pulmonary hypertension (i.e. groups 2-5)
- Contraindicated to undergo fluoroscopy and/or coronary angiography
- Pregnancy
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Pulmonary Index of Microcirculatory ResistanceAlso: PIMRPIMR measurement involves placing a coronary pressure wire in the pulmonary arteries and making pressure/time measurements during maximal flow down the artery. | Other | PAH Patients |
| Right Ventricle Index of Microcirculatory ResistanceAlso: RV-IMRRV-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 | PAH Patients |
Primary outcome
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.
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.
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.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 1 Aug 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Rushi Parikh, MD principal investigator
University of California, Los Angeles
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Pulmonary Hypertension, run by University of California, Los Angeles at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 1 Aug 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
PAH hospitalization or all-cause mortality at 1 year (time frame: 1 year). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Aug 2025.