Impact of Preoperative FFR on Arterial Bypass Graft Functionality (IMPAG)

January 8, 2024 updated by: Ottawa Heart Institute Research Corporation

Impact of Preoperative FFR on Arterial Bypass Graft Functionality: Towards a New CABG Paradigm

This study was designed to evaluate the correlation between pre-operative FFR and the functionality of arterial bypass grafts six months after coronary artery bypass grafting. Patients with multi-vessel coronary artery disease will undergo both a coronary angiogram and FFR during their diagnostic workup. All patients will be referred for surgical revascularization (CABG) with planned use of arterial grafts. Six months after surgery, patients will undergo an angiogram to assess the functionality of the bypass graft and anastomosis.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

The objective of surgical coronary revascularization is to restore blood flow supply to a myocardial territory that is ischemic or at risk of infarction, by interposing a low-resistance conduit in parallel to a major diseased coronary artery segment. The conductance of this additional conduit must be sufficient to accommodate high flow demands with minimal pressure drop at the site of distal implantation. Such a conduit may be used either as single independent graft, or assembled in a variety of sequential configurations, according to the preferred technique and based on the underlying coronary artery disease (CAD). Saphenous vein grafts (SVGs), most commonly used as single free grafts reimplanted on the aorta, are large conduits with very limited vasomotion. Their resistance to blood flow is negligible due to their large diameter, absence of muscular layer and usually short length, but their long-term patency is hindered by the development of premature atherosclerosis. In contrast, arterial grafts are usually of smaller diameter and more resistive due to their histological features. These arterial conduits are usually used in situ, as the second or third order of branches from the aorta and, therefore, have higher pressure drops compared to grafts implanted directly onto the aorta. Alternatively, the creation of composite T grafts with the free right internal thoracic artery (RITA) connected to the in situ left internal thoracic artery (LITA) can allow revascularization of all myocardium at risk. However, consequences of such a combination are that the flow supply is entirely dependent on the flow capacity of the proximal LITA, and that resistance along the graft may become a concern, particularly at the more distal anastomoses of the configuration (due to the cumulative length and distal graft tapering).

Competitive flow typically occurs when the resistance of the graft closely matches that of the native coronary artery target. In this situation, both the native coronary artery and the bypass graft contribute to distal perfusion, each providing resistance to blood flow from the other. Schematically, these resistances are arranged in parallel with input pressure at the coronary ostium or at the ostium of the graft, and output pressure at the anastomotic target site. The pressures at the two ends of the circuit are identical with only minor phasic variations in proximal pressure due to the delay in progression of the systolic pressure wave from the coronary ostium to the more distal ostium of the graft. According to Ohm's law, blood flow is directly proportional to pressure gradient and inversely proportional to resistance. Consequently, the relative contribution of the graft and of the native circulation to distal perfusion will be inversely proportional to their own resistance: if the resistance of the graft exceeds that of the native vessel (for instance, in situations of non-severely obstructive CAD), the distal territory will be predominantly perfused by the native coronary artery; if the resistance of the native vessel remains higher, the flow through the graft will be predominant; if both conduits oppose near-identical resistances to flow, their contribution to distal blood flow will be equivalent.

Many reports have consistently suggested that competitive flow in arterial bypass grafts negatively affects patency: more graft failures are observed when native coronary stenosis is less severe. Further, the misunderstanding of competitive flow also impairs multiple arterial grafting adoption rates, which remain quite low worldwide despite proven superior outcomes, due in large part to incomplete understanding of the effects of flow competition by surgeons. Current methods to evaluate coronary stenosis are: visual inspection, quantitative computerized angiography (QCA) and fractional flow reserve (FFR). Several studies have compared these three methods, demonstrating that visual assessment and QCA are of limited value for accurately predicting the significance of most intermediate narrowings and, therefore, at predicting a competition phenomenon. In contrast, FFR measures the consequence of the stenosis in terms of reduction of blood flow capacity. FFR reliably identifies stenoses associated with inducible ischemia with more than 93% accuracy, a rate higher than any other test. Despite these advantages, FFR is not widely applied especially in coronary surgery whereas in interventional cardiology, it is used near systematically. What the investigators propose in this collaborative study is a complete paradigm shift in how coronary surgery is carried out - total arterial grafting supported by a true physiologic basis, and a correlated proof of its outcomes.

Currently, indications for surgical coronary revascularization still largely rely only on visual estimation of stenoses. Unfortunately, the estimation of the true coronary lesion severity by visual estimation is especially poor for moderate lesions, i.e. between 50 to 70% stenosis. An FFR cutoff value of 0.8 is obtained in only 35% of these moderate lesions. When using saphenous vein, the impact of competition flow on graft patency is minimal in this situation but when an artery conduit is preferred, it impacts the functionality of the graft significantly.

Therefore, the investigators are proposing a prospective FFR evaluation of surgical patients with 3-vessel CAD, whose disease severity will be estimated by visual inspection during diagnostic angiogram. FFR will be performed and all values will be recorded; however, the patient, interventional cardiologist, and surgeon will be blinded to its results. All patients will then undergo coronary surgery with planned arterial revascularization. Six months after surgery, a control angiogram will be performed to evaluate functionality of the grafts. The results of this functional assessment will be correlated with the preoperative FFR values, in order to find a cutoff above which the arterial grafts are not functional, which will also be analyzed by subgroups defined according to configuration (i.e. in situ or composite).

Study Type

Interventional

Enrollment (Estimated)

120

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Belgium
      • Bouge, Belgium
        • Clinique Saint-Luc Bouge
  • Canada
    • Ontario
      • Ottawa, Ontario, Canada, K1Y4W7
        • University of Ottawa Heart Institute

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. All patients with multi-vessel coronary artery disease undergoing elective or urgent first time coronary artery bypass grafting (CABG).
  2. All patients undergoing diagnostic angiography and suspected to have multi-vessel disease for referral to CABG
  3. Patients requiring both on-pump or off-pump CABG are accepted, as long as a arterial revascularisation is planned.
  4. The patients must be over the age of 18.
  5. CABG is the only procedure being conducted

Exclusion Criteria:

  1. Planned simultaneous surgical procedure unrelated to coronary revascularization (e.g. valve repair/replacement, aneurysmectomy, carotid endarterectomy or carotid stenting)
  2. Redo CABG, or a percutaneous coronary intervention (PCI) within the last 6 months.
  3. Severe renal insufficiency (preoperative creatinine >150umol/L) contraindicating postoperative coronary angiography
  4. Significant leukopenia, neutropenia, thrombocytopenia, anemia, or known bleeding diathesis
  5. Women who are pregnant or are seeking to become pregnant
  6. Must not have severe congestive heart failure (class III or IV New York Heart Association) at enrollment
  7. Left ventricular ejection fraction less than 30%
  8. Prior history of significant bleeding that might be expected to recur with CABG
  9. Prisoners or institutionalized individuals
  10. Geographic inaccessibility for the follow-up visits required by protocol
  11. Concurrent enrollment in another clinical trial
  12. Extra-cardiac illness that is expected to limit survival to less than 5 years

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Diagnostic
  • Allocation: Non-Randomized
  • Interventional Model: Single Group Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Functional graft
Follow-up angiography of all bypass grafts and anastomoses six months after surgery: anastomotic function was scored as 0 for an occluded graft, 1 when the flow from the native coronary artery was dominant, 2 when flow supply from the native coronary and from the graft was balanced, and 3 when the native coronary was fully opacified by the graft. An anastomosis was considered "functional" for score of 3.
Procedure: Fractional Flow Reserve (FFR)
An FFR will be performed pre-operative to the CABG procedure
Active Comparator: Non functional graft
Follow-up angiography of all bypass grafts and anastomoses six months after surgery: anastomotic function was scored as 0 for an occluded graft, 1 when the flow from the native coronary artery was dominant, 2 when flow supply from the native coronary and from the graft was balanced, and 3 when the native coronary was fully opacified by the graft. An anastomosis was considered "non functional" for scores of 0 to 2.
Procedure: Fractional Flow Reserve (FFR)
An FFR will be performed pre-operative to the CABG procedure

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Correlation between pre-operative FFR and anastomosis function
Time Frame: Up to 12 months
The primary outcome was the evaluation of the correlation between target vessel pre-operative FFR value and the anastomosis function as measured by angiogram approximately 6 months after surgery.
Up to 12 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Correlation between pre-operative FFR and anastomosis occlusion
Time Frame: Up to 12 months
The evaluation of the correlation between target vessel pre-operative FFR value and occlusion of the anastomosis measured by angiogram approximately 6 months after surgery.
Up to 12 months
Major Adverse Cardiac Events
Time Frame: Up to 12 months
Major adverse cardiac events (MACE) is a qualitative measurement of any adverse cardiac events such as death or myocardial infraction after the operative procedure.
Up to 12 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ottawa Heart Institute Research Corporation

Investigators

  • Principal Investigator: David Glineur, MD, PhD, Ottawa Heart Institute Research Corporation

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

November 1, 2015

Primary Completion (Estimated)

November 1, 2028

Study Completion (Estimated)

November 1, 2028

Study Registration Dates

First Submitted

August 11, 2015

First Submitted That Met QC Criteria

August 17, 2015

First Posted (Estimated)

August 18, 2015

Study Record Updates

Last Update Posted (Actual)

January 10, 2024

Last Update Submitted That Met QC Criteria

January 8, 2024

Last Verified

January 1, 2024

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 4385

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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