The Value of Fractional Flow Reserve Derived From Coronary CTA and in the Triage of Low to Intermediate Risk Chest Pain Patients: Design: Single Center Prospective Clinical Trial; Target Disease: Coronary Artery Disease

CCTA is increasingly becoming a preferred non-invasive imaging modality because of its high sensitivity and negative predictive value for the detection of CAD. It has been shown to be a robust imaging modality for evaluation of chest pain, and is associated with decreased unnecessary hospital admission, length of stay, major adverse cardiovascular event rates, recidivism rates, and downstream resource utilization compared to standard evaluation [5]. While findings so far are highly suggestive of CCTA's significance as a gatekeeper for Invasive Coronary Angiography (ICA) by ruling out obstructive CAD, fewer than half of obstructive stenosis identified by CCTA are ischemia-causing, signifying its poor positive predictive value and inherent lack of physiological information [6-8]. Consequently, utilization of CCTA has not entirely averted need for downstream testing for functional assessment of CCTA-detected obstructive lesions either by stress testing or ICA. Recently a major treatment modality, associated with the use of CCTA, has become available that offers promise for improving positive predictive value and physiological relevant hemodynamic data. Advances in computational fluid dynamic techniques applied to standard CCTA are now emerging as a powerful tool for virtual measurement of FFR from CCTA imaging (CT-FFR). This techniques correlate well with invasively measured FFR [1-4]. CT-FFR is not an investigational agent, having been approved by FDA in November, 2014. However, more work is necessary to delineate the patient population that could derive maximal benefit from this new technology.

While few publications regarding the use of CT-FFR specifically address the cost of diagnostic work-up for obstructive disease, it is clear that the cost structure resulting from changes in diagnostic testing will also change. Deferral or avoidance of cardiac catheterization and nuclear stress testing will likely yield significant reductions in the cost of the diagnostic testing.

From 1/1/2009 to 3/31/2015 our team introduced and operated a CCTA Chest Pain triage program for low to intermediate risk patients at Stony Brook University Hospital ED and non-emergency outpatient services, the only tertiary care hospital in Suffolk County. Concurrently, we established a registry to monitor patient outcomes for all patients receiving CCTA at Stony Brook Medicine. Our registry contained nearly 15,000 patient CCTA procedures. Our major registry study established the effectiveness of CCTA as an imaging modality for evaluating Emergency Department chest pain in a cost efficient manner with a false negative rate less than 1% [5]. However, our registry reflects the poorer positive predictive values documented by other industry studies [6-8].

False positive workup results in the necessity of performing cardiac catheterization on patients at risk for obstructive disease based on assessment with current standard of care (combined screening with CCTA and stress MPI). Reduction in the rate of false positive testing would lead to reduction in risk from invasive procedures and radiation exposure to patients and reduced cost to the health care system.

Several medical institutions currently use HeartFlow CT-FFR as standard of care for evaluating obstructive disease. Generally, the standard of care at these institutions is to refer patients who are 30 to 90 percent obstructed by CCTA and who have reduction of flow <= to 0.8 that is deemed to be medical significant by the attending cardiologist to Invasive FFR. HeartFlow has reported to us confidentially that this routine use of CT-FFR has resulted in a 54% reduction in false positive rate as compared to use of CCTA alone.