HeartFlowNXT - HeartFlow Analysis of Coronary Blood Flow Using Coronary CT Angiography

To determine the diagnostic performance of FFRCT by coronary computed tomographic angiography (cCTA), as compared to cCTA alone, for non-invasive determination of the presence of a hemodynamically significant coronary lesion, using direct measurement of fractional flow reserve (FFR) during cardiac catheterization as a reference standard.

Recently, coronary Computed Tomography Angiography (cCTA) of 64-detector rows or greater has emerged as a novel non-invasive imaging modality that is capable of providing high-resolution images of coronary artery lesions (Budoff 2008; Miller 2008; Meijboom 2008). While cCTA demonstrates good diagnostic performance for detection and exclusion of anatomic coronary artery stenoses, numerous prior studies have revealed an unreliable relationship between detection of obstructive anatomic coronary artery stenoses by cCTA and hemodynamically (HD)-significant coronary artery disease (CAD), identified by myocardial perfusion SPECT or fractional flow reserve (FFR) (Di Carli 2007; Klauss 2007; Rispler 2007; van Werkhoven 2009). Individual subjects may have HD-significant CAD despite cCTA assessment demonstrating angiographically mild (\<50%) maximal stenosis (Schuijf 2006). These findings emphasize the need for additional measures beyond anatomic stenosis severity for the detection and exclusion of HD-significant CAD.

Measurement of FFR during invasive cardiac catheterization represents the "gold standard" for assessment of the hemodynamic significance of coronary artery lesions (Kern 2010). Anatomic coronary artery stenosis assessment by quantitative coronary angiography (QCA) also correlates very poorly with FFR Melikian 2010). This was highlighted by the results of the FAME study in which FFR-guided coronary revascularization improved healthcare and economic outcomes compared to the conventional angiographically guided strategy (Pijls 2010; Tonino 2009; Tonino 2010).

The major disadvantage of FFR is that it has to be measured invasively. HeartFlow, Inc. ('HeartFlow') has recently developed a non-invasive method to determine FFR which computes the hemodynamic significance of CAD (FFRCT) from subject-specific cCTA data using computational fluid dynamics under rest and simulated maximal coronary hyperemic conditions. Preliminary results in subjects suggest that FFRCT accurately predicts the hemodynamic significance of coronary lesions when compared to directly-measured FFR during invasive cardiac catheterization (Koo 2011).

Eligibility Criteria:
Inclusion Criteria:

* Age ≥18 years
* Subject providing written informed consent
* Scheduled to undergo a clinically indicated Invasive Coronary Angiogram (ICA)
* Has had ≥64 multidetector row cCTA within 60 days prior to ICA or agrees to undergo cCTA with ≥64 multidetector row cCTA within 60 days prior to ICA

Exclusion Criteria:

* Percutaneous coronary intervention (PCI) has been performed any time prior to ICA.
* Prior coronary artery bypass graft (CABG) surgery
* Contraindication to beta blocker agents, nitrates, or adenosine, including 2nd or 3rd degree heart block; sick sinus syndrome; long QT syndrome; severe hypotension; severe asthma, severe COPD or bronchodilator-dependent COPD
* Suspicion of acute coronary syndrome (acute myocardial infarction and unstable angina)
* Recent prior myocardial infarction within 30 days prior to cCTA or between cCTA and ICA
* Known complex congenital heart disease
* Prior pacemaker or internal defibrillator lead implantation
* Prosthetic heart valve
* Tachycardia or significant arrhythmia
* Impaired chronic renal function (serum creatinine \>1.5 mg/dl)
* Subjects with known anaphylactic allergy to iodinated contrast
* Pregnancy or unknown pregnancy status in subject of childbearing potential
* Body mass index \>35 at time of cCTA
* Subject requires an emergent procedure
* Evidence of ongoing or active clinical instability, including acute chest pain (sudden onset), cardiogenic shock, unstable blood pressure with systolic blood pressure \<90 mmHg, and severe congestive heart failure (NYHA III or IV) or acute pulmonary edema
* Any active, serious, life-threatening disease with a life expectancy of less than 2 months
* Inability to comply with study procedures