Case Report

Virtual FFR: A Simple, Reliable, Angiography-Based Method to Assess Physiological Lesion Severity in the Cath Lab

Hussein Rahim, MD1

Ziad Ali, MD, DPhil1,2

1New York Presbyterian Hospital / Columbia University Medical Center, New York, New York; 2Cardiovascular Research Foundation, New York, New York  

Hussein Rahim, MD1

Ziad Ali, MD, DPhil1,2

1New York Presbyterian Hospital / Columbia University Medical Center, New York, New York; 2Cardiovascular Research Foundation, New York, New York  

Percutaneous coronary intervention (PCI) in stable coronary disease can improve quality of life and may reduce type 1 MI.1 Identifying significant coronary lesions that will benefit from PCI can sometimes be challenging. FFR is the gold standard for evaluating the functional significance of a coronary lesion.2 Fractional flow reserve (FFR)-guided PCI has been shown in multiple studies to improve clinical outcomes and coronary physiology can lead to reclassification of treatment strategy in up to 40% of cases.3,4 Despite the undeniable utility of an FFR-guided treatment strategy it remains underutilized in clinical practice due to several disadvantages. FFR requires extra equipment, time, and medication administration, making its use cumbersome in a busy clinical practice. 

FFR derived from routine coronary angiography is a novel technology for assessing the functional significance of a lesion by creating a 3-dimensional reconstruction of the artery and assessing the resistance across a lesion. Angio-derived FFR values can be calculated quickly without invasive pressure measurements. In the following case, we describe how angio-derived FFR can be integrated into normal workflow to provide almost instantaneous physiological assessment of an intermediate coronary artery stenosis. 

Case Report

A 62-year-old female with multiple cardiac risk factors presented for coronary angiography. The patient was a former smoker and had a history of hypertension, hyperlipidemia, peripheral arterial disease, and end-stage renal disease on dialysis. She was referred for coronary angiography, given multiple risk factors and stable anginal symptoms. 

Right radial access was obtained and routine diagnostic angiography was performed, revealing an intermediate lesion, 50-70% stenosis, in the mid left anterior descending (LAD) artery (Figure 1). To determine the physiological significance of the lesion, angio-derived FFR was calculated using the Cardiovascular Angiography Analysis System Workstation (Pie Medical Imaging and Siemens Healthineers). 

We selected two angiographic views for analysis at least 30 degrees apart with minimal foreshortening and overlap of vessels (Figure 2). We selected the appropriate cath lab setup from a drop-down menu. Next, a frame within each angiographic view during diastole with good contrast filling was selected. To automatically generate vessel contours, we clicked along the length of the LAD (Figure 3). The contour lines were slightly adjusted to ensure the vessel was contoured appropriately (Figure 4). A common image point on both views was identified (Figure 5) and the blood pressure was entered. A 3D model of the artery and an angio-derived FFR value of 0.68 was calculated (Figure 6). Invasive FFR performed on the lesion yielded a value of 0.71 (Figure 7). 

The lesion was subsequently imaged with optical coherence tomography (OCT) and stented with a 2.25 x 33 mm drug-eluting stent. The patient tolerated the procedure well. She experienced relief of angina and was well at follow-up. 

Discussion 

The patient described herein represents a very typical patient. Intermediate coronary lesions are common in the cath lab. The identification of an intermediate lesion in standard clinical practice often necessitates the use of invasive physiology to help determine suitability for stenting or deferral. Angio-derived FFR is a novel technology that allows virtual physiological assessment of intermediate lesions in a rapid and easy manner that can be seamlessly integrated into normal cath lab workflow. 

Angio-derived FFR has a high correlation with invasive FFR. In the FAST study5 evaluating the accuracy of angio-derived FFR versus standard invasive FFR, the per-vessel sensitivity and specificity were 94% (95% confidence interval [CI], 88% to 97%) and 91% (86% to 95%). The diagnostic accuracy of angio-derived FFR was 92%. Angio-derived FFR requires no medication administration or additional wires. Perhaps its biggest advantage over invasive FFR is that it can be calculated from standard angiographic views, frequently in less than a minute (Video 1).



Angio-derived FFR does have several potential limitations. In order to generate an angiogram that can be analyzed, no panning nor excessive motion of the patient is allowed. Foreshortening and vessel overlap need to be minimized and can contribute to inaccurate results. To obtain adequate angiograms, occasionally slightly more contrast may be necessary. While angio-derived FFR does correlate closely with invasive FFR, there are currently no large clinical outcomes trial results, although they are in progress.

Physiology is an integral part of the evaluation of intermediate coronary stenoses. While invasive FFR is currently considered the gold standard for evaluation, angio-derived FFR represents a new technology that may be more cost effective, faster, comfortable, and potentially, just as accurate. As evidence accrues, more studies will be necessary to validate this promising technology and its place in the modern cath lab. 


Read the accompanying interview with Dr. Ziad Ali:

This article is supported by Siemens Healthineers.

Disclosures: Dr. Ali reports grants from National Heart, Lung, and Blood Institute during the conduct of the study; grants and personal fees from Abbott Vascular, grants and personal fees from Cardiovascular Systems, Inc., personal fees from Amgen, AstraZeneca, Abiomed, Boston Scientific, Cardinal Health, OpSens Medical, and ACIST Medical; and other from Shockwave Medical, outside the submitted work. 

Ziad A. Ali, MD, DPhil, can be contacted at zaa2112@columbia.edu.

References
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  3. Andell P, Berntorp K, Christiansen EH, et al. Reclassification of treatment strategy with instantaneous wave-free ratio and fractional flow reserve: a substudy from the iFR-SWEDEHEART trial. JACC Cardiovasc Interv. 2018; 11(20): 2084-2094. doi:10.1016/j.jcin.2018.07.035
  4. van Nunen LX, Zimmermann FM, Tonino PA, et al. Fractional flow reserve versus angiography for guidance of PCI in patients with multivessel coronary artery disease (FAME): 5-year follow-up of a randomised controlled trial. Lancet. 2015; 386(10006): 1853-1860. doi:10.1016/S0140-6736(15)00057-4
  5. Fearon WF, Achenbach S, Engstrom T, et al. Accuracy of fractional flow reserve derived from coronary angiography. Circulation. 2019; 139(4): 477-484. doi:10.1161/CIRCULATIONAHA.118.037350