Philips offers a portfolio of advanced image-guided therapy devices, and has developed instant wave-free ratio (iFR), a method to assess if a coronary stenosis is causing myocardial ischemia.
If a coronary vessel is partially occluded, it is important to assess the extent to which it is reducing the blood supply to the myocardium, as this will affect treatment and prognosis. One way to do this is with a coronary pressure guide wire used to measure the pressure difference before and after the arterial blockage. Typically, clinicians will inject vasodilators to increase blood flow while performing these pressure measurements.
Philips has developed a technology called iFR, which clinicians can use to assess the adequacy of blood flow through a coronary stenosis, and which does not require the use of vasodilators. In data released from the DEFINE FLAIR clinical trial, researchers compared iFR with another technique that requires vasodilators called fractional flow reserve (FFR). In March 2017, this DEFINE FLAIR data was presented in a late-breaking session at the American College of Cardiology Annual Scientific Session and concurrently published in the New England Journal of Medicine.
Medgadget asked Andrew Tochterman, Coronary Segment Leader of Image Guided Therapy at Philips, some questions about the image guidance systems from Philips and the iFR results.
Conn Hastings, Medgadget: Please give us a little background on coronary artery disease and the decisions facing a clinician in assessing and treating such a patient.
Andrew Tochterman, Philips: Coronary artery disease is a blockage or narrowing (stenosis) of the arteries that supply blood to the heart muscle, often due to a buildup of fatty plaque inside the arteries. Severe blockages have the potential to cause a heart attack or even death. When clinicians are diagnosing patients, they’re assessing the risk of heart attacks and trying to reduce plaque buildup. For those that have an advanced form of the disease, doctors need to perform a bypass surgery or stenting to increase the opening of the artery to allow blood flow. Some patients do fine using standard medications prescribed by their cardiologist. The decision on which therapy to use can be complex, involving multiple pieces of information.
Medgadget: Please give us an overview of the image-guided therapy devices developed by Philips that are used for these types of coronary interventions.
Andrew Tochterman: The iFR technology, which is proprietary to Philips, makes the diagnosis simpler, more informative and less uncomfortable for patients. The Philips device featuring the iFR technology is the Core system with the Verrata Plus pressure wire. An additional device developed by Philips that helps coronary interventions is SyncVision, which is a guidance system that makes vessel sizing simpler and streamlines lesion assessment, enabling precise therapy delivery with the fluoroscopic image stream. This technology is unique in that it overlays the information related to the ischemic burden of the vessel (iFR or FFR) onto the angiogram for a single, integrated view of the physiologic disease burden of the artery. This is a great example of how information is being integrated for the clinician.
Medgadget: One of the drawbacks of FFR is the need to use a vasodilator. Can you tell us why this is a drawback, and why avoiding vasodilators is beneficial for patients?
Andrew Tochterman: The use of a vasodilator is a limitation to FFR because it is required and can cause potential side effects which can include increased heart rate, pounding of the heart, flushing, elevated temperature and feelings of impending doom, which stimulate physical and emotional distress. One of the major reasons Philips saw potential in iFR was due to reduced patient discomfort when compared to FFR because the procedure does not require hyperemic drugs. With iFR, severe patient symptoms are almost completely eliminated as compared to FFR. In many parts of the world, this hyperemic drug can also be difficult to obtain, or can be expensive. Having the potential to assess the severity of the disease without the additional cost is an additional benefit.
Medgadget: So, how does iFR work? How does it differ from FFR?
Andrew Tochterman: FFR and iFR both measure the difference in blood pressure (and by inference the blood flow) through a partially blocked coronary artery, otherwise known as stenosis, to assess whether the blockage is likely to cause a shortage of oxygen to the heart muscle, called myocardial ischemia. An FFR-guided strategy uses hyperemic drugs, which requires additional steps and costs to a procedure, and causes patient discomfort. An iFR-guided strategy does not require the administration of hyperemic drugs for assessment, making it an advantageous primary diagnostic tool. It’s been shown that an iFR-guided strategy reduces procedure time, cost and complexity when compared to FFR, allowing physicians to deliver care to help improve patient and economic outcomes without degradation of diagnostic accuracy.
Medgadget: What inspired Philips to develop iFR? How long has it been in use?
Andrew Tochterman: We are committed to enhancing the prevalence of physiology-guided decision-making relative to angiography, in terms of diagnostic catheterization. In 2013, we first released iFR as a unique index to Philips, allowing hyperemia-free physiological assessment of coronary blockages. In coronary artery disease assessment, clinicians have been using FFR in addition to angiographic images to assess the physiology of a suspected blockage in coronary arteries. However, we saw iFR as a next-generation physiologic measurement that uses the same pressure guide wires and equipment as FFR, but avoids the administration of hyperemic agents to the patient that is required with FFR. iFR had the potential to help physicians determine the most appropriate treatment and improve patient care, and has the potential to eclipse the previous gold standard of FFR in assessing coronary blockages.1
Medgadget: Can you sum up the main findings of the DEFINE FLAIR trial? What advantages did iFR show?
Andrew Tochterman: DEFINE FLAIR2 is a randomized, controlled, single-blinded comparison of clinical outcomes and cost efficiencies of iFR and FFR interventions of almost 2,500 patients in over 45 centers across Europe, Asia, North America, and Africa in the diagnosis and treatment of heart disease. The study conducted its comparison of iFR versus FFR using pressure guide wires and equipment from Philips. The primary endpoint was the rate of major adverse cardiac events between an FFR-guided strategy, and an iFR-guided strategy. The one year results of the study concluded that there were no significant differences in clinical event rates with a significant advantage of iFR in reducing patient discomfort, and in reducing procedure time. Importantly, at the American College of Cardiology meeting in Orlando this year the health economic analysis for the DEFINE FLAIR one-year results was presented, showing that by using an iFR-guided strategy you could reduce the cost of procedure by an average of $896 per patient compared to an FFR-guided strategy. iFR offers a total procedure cost savings of approximately 10% per patient over FFR, and patients treated with an iFR-guided strategy had fewer coronary artery bypass graft procedures and fewer subsequent revascularizations than those treated with an FFR-guided strategy. So, we are excited to see a technology that delivers comparable patient care, while reducing cost and time, and we were proud to sponsor the type of clinical research necessary to help support it.
Video of a case using iFR:
Technology info page: iFR modality…
More info on the DEFINE FLAIR study…
- Bhatt DL. Editorial: assessment of stable coronary lesions. N Engl J Med 2017;376:1879-81.
- Davies JE, Sen S, Dehbi H-M, et al. Use of the instantaneous wave-free ratio or fractional flow reserve in PCI. N Engl J Med 2017;376:1824-34.