Author + information
- Niels Peter Rønnow Sand, MD∗ (, )
- Karsten Tange Veien, MD,
- Søren Steen Nielsen, MD,
- Bjarne Linde Nørgaard, MD and
- Lisette Okkels Jensen, MD
- ↵∗Department of Cardiology, Hospital of Southwest Denmark, Finsensgade 35, 6700 Esbjerg, Denmark
We thank Dr. Gallone and colleagues for their interest in our study and their thoughtful comments. We agree that the bewildering use of nomenclature related to coronary flow, myocardial perfusion, and ischemia is misleading. Accordingly, we should have more focus on a consistent use of these concepts in clinical practice, research, and guidelines.
In 1994 and 1996, respectively, De Bruyne et al. (1) and Pijls et al. (2) demonstrated a connection between fractional flow reserve (FFR) and coronary flow reserve by positron emission tomography (PET) and later documented a strong association between FFR and myocardial ischemia by 3 independent tests, which normalized after revascularization. Regardless of whether one accepts the association between low FFR and ischemia, the use of FFR has a level 1A recommendation for decision making in the catheterization laboratory in all major guidelines.
However, noninvasive diagnostic testing strategies in patients with stable chest pain have changed from modalities that induce myocardial ischemia by exercise or dobutamine to pharmacologically mediated vasodilatation by adenosine, creating maximal achievable heterogeneity of myocardial perfusion rather than myocardial ischemia. The modalities referred to by Dr. Gallone and colleagues, PET, cardiac magnetic resonance, computed tomography (CT), and myocardial perfusion imaging, merely reflect myocardial perfusion during maximal hyperemia and only occasionally do they refer to perfusion of ischemic myocardium. Accordingly, it seems unlikely that the presence of myocardial territories supplied by coronary arteries with profoundly positive FFR and at the same time a normal perfusion by single-photon emission computed tomography (SPECT) reflects solely different levels of severity of coronary artery disease (CAD); differences in diagnostic test performance results must play a role in such circumstances.
This study is the first of its kind to prospectively compare the diagnostic performance of SPECT, the most commonly used testing modality, versus coronary CT angiography (CTA)- derived FFR (FFRCT) in stable symptomatic patients who have CAD as determined by coronary CTA. In accordance with the recent Dan-NICAD (Danish study of Non-Invasive testing in Coronary Artery Disease) and PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography With Invasive Coronary Angiography) trials, our study demonstrated that SPECT, using FFR as the reference, had a poor diagnostic sensitivity, which was further emphasized by the fact that SPECT results were normal in 50% of patients who were undergoing multivessel revascularization and in 42% of patients who had an FFR ≤0.67 (3), whereas the diagnostic sensitivity of FFRCT was high in all subgroups.
In conclusion, contemporary testing strategies used to identify patients who may benefit from referral to invasive procedures or those who can be safely deferred from further testing do not induce myocardial ischemia. Under this paradigm, FFRCT is an applicable and sensitive modality for evaluating the hemodynamic significance of coronary lesions in patients with stable chest pain and CAD as demonstrated by coronary CTA.
Please note: Dr. Jensen has received institutional research grants from St Jude Medical, Biosensors, and Biotronik. Dr. Nørgaard has received unrestricted institutional research grants from Siemens and HeartFlow. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2019 American College of Cardiology Foundation
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