Evaluation of the Opsens Fractional Flow Reserve (FFR) Wire as a "Work Horse" Wire

EVALUATION OF THE OPSENS FRACTIONAL FLOW RESERVE (FFR) WIRE AS A "WORK HORSE" WIRE

INVESTIGATORS:

PRINCIPAL INVESTIGATOR: BARRY F URETSKY, MD CO-INVESTIGATOR: ABDUL HAKEEM, MD CO-INVESTIGATOR: MALEK AL-HAWWAS, MD

Introduction The use of fractional flow reserve (FFR) has improved outcomes in percutaneous coronary interventions (PCI) in patients with symptomatic stable coronary artery disease (CAD) with intermediate angiographic stenoses. It is a clinical tool used routinely in cardiac catheterization laboratories throughout the world including the Little Rock VA hospital. The technique utilizes a pressure transducer constructed as part of an 0.014" guidewire. The wire is passed distal to the stenosis. Under the condition of maximal hyperemia induced by a drug, typically adenosine, the pressure proximal to the stenosis, i.e. aortic pressure or Pa and the pressure distal to the stenosis, Pd, are measured. The ratio, Pd/Pa, under maximal flow or hyperemia is known as the fractional flow reserve (FFR). An FFR of <0.80 has been correlated with observed myocardial ischemia using other diagnostic methods, particularly nuclear stress and dobutamine echo stress testing. The FAME trial clearly demonstrated its value in improving long-term outcomes as compared to use of angiography alone (1). As such, the use of FFR is incorporated into both AHA ACC and European PCI guideline recommendations as part of routine care for intermediate lesions (2,3).

One of the limitations of the use of the FFR pressure wire itself is that its handling characteristics are somewhat inferior to a standard "work horse" guide wire used for PCI. A "work horse" guide wire is so defined because it can be used in most PCI cases. It combines a low tip load (to avoid intimal dissection) with excellent (ideally, one-to-one) torque transmission and trackability through tortuous lesions. There are several different work horse wires available. Although the wires may be different for different Cath Labs and operators, the wires are universally used to maximize safety, efficacy, and efficiency of PCI.

In patients specifically requiring FFR to determine the value of PCI, it would be ideal if an FFR wire was as effective as a work horse wire so it could be used in difficult-to-traverse lesions. However, due to the complex electronics within current FFR wires, handling characteristics of previously used wires are inferior to current work horse wires. Recently the FDA has approved an FFR guide wire, OptoWire, (Opsens, Quebec City, Quebec, CAN) using light transmission to measure pressure rather than electrical transduction (4). It is commercially available in the United States. Its handling characteristics appear to approach that of a work horse guide wire and may represent an improvement over electrical transduction wires. The primary purpose of the present study is to determine how effective this wire is as a work horse wire in patients in whom FFR is required.

The OptoWire may also have the advantage of less "drift" occuring during the procedure. Drift refers to the change in pressure due to issues related to the wire and measuring system, rather than a true change in pressure. All current FFR wire systems demonstrate some degree of drift requiring measuring pressure of the wire in the aorta after the procedure is completed to determine if, and to what extent, drift has occurred. Thus, a secondary aim of this study will determine the degree of drift.

In clinical practice, FFR is performed before, and often after, PCI. In a study of 574 patients treated at the Little Rock VA (IRB Study, #779601), teh investigators found that approximately 20% of angiographically optimized PCI still had an ischemic FFR. The investigators further found that this ischemic value could be improved by further treatments including balloon angioplasty and stenting. Thus, the secondary purpose is to measure FFR after successful PCI to ascertain the incidence of persistently ischemic FFR after optimized angiographic stenting to confirm the result from out previous study.

Statistical analysis

This study is descriptive. It will use means and standard deviation for continuous variables and prevalence or incidence in percentages as appropriate to show results. As there is no comparator group, comparative statistics will not be employed.

Research aspect of study

The research aspect of the study is limited to the systematic collection and analysis of data using the Opsens FFR wire with plan for publication. The other aspects of the study are considered part of routine clinical care. They include passage of FFR wire, measurement of FFR pre- and post-PCI, and performance of PCI itself.

Significance of study

A wire that can be used as a workhorse as well as be able to measure FFR would be of great value. The more effective and efficient is the FFR wire in not only measuring pre-PCI FFR but being able to be used for PCI and be stable and durable enough to be used for post-PCI optimization, the greater is the probability that this approach will be more generally adopted into clinical practice. Demonstration that the Opsens FFR wire is effective in this regard should further this goal.

The investigators previously demonstrated that 21% or about 1 in 5 patients had an ischemic FFR after satisfactory angiographic result. This study will confirm previous results or suggest either an over- or under-estimation of that incidence.