Korean J Radiol.  2016 Jun;17(3):307-320. 10.3348/kjr.2016.17.3.307.

Physiologic Assessment of Coronary Artery Disease: Focus on Fractional Flow Reserve

• Hwang D
• Lee JM
• Koo BK

• KMID: 2451406
• DOI: http://doi.org/10.3348/kjr.2016.17.3.307

Abstract

The presence of myocardial ischemia is the most important prognostic factor in patients with ischemic heart disease. Fractional flow reserve (FFR) is a gold standard invasive method used to detect the stenosis-specific myocardial ischemia. FFR-guided revascularization strategy is superior to angiography-guided strategy. The recently developed hyperemia-free index, instantaneous wave free ratio is being actively investigated. A non-invasive FFR derived from coronary CT angiography is now used in clinical practice. Due to rapid expansion of invasive and non-invasive physiologic assessment, comprehensive understanding of the role and potential pitfalls of each modality are required for its application. In this review, we focus on the basic and clinical aspects of physiologic assessment in ischemic heart disease.

Keyword

Coronary artery disease; Physiology; Ischemia; Fractional flow reserve

MeSH Terms

Coronary Angiography
Exercise
Fractional Flow Reserve, Myocardial/*physiology
Heart/diagnostic imaging
Hemodynamics
Humans
Myocardial Ischemia/*diagnosis/diagnostic imaging
Stress, Physiological
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Relationship between pressure and flow during resting and hyperemic states. In resting state, coronary artery is under autoregulation to maintain adequate coronary flow according to oxygen demand. Pressure and flow are in linear correlation when microvascular resistance is minimal and constant.

• 

  Fig. 2 Concept of fractional flow reserve. Fractional flow reserve (FFR) is defined as ratio of maximal coronary blood flow in diseased artery (Qsmax) to normal maximal coronary blood flow in same artery (Qnmax). As venous pressure (Pv) is negligible compared to aortic (Pa) and distal coronary pressure (Pd), FFR can be calculated as ratio of Pd and Pa.

• 

  Fig. 3 Case with discrepancy between exercise stress test and fractional flow reserve (FFR). 76-year-old man with stable angina who underwent coronary CT angiography (A) and exercise stress test (B). There was intermediate stenosis in proximal left anterior descending coronary artery (LAD) and exercise stress test was negative. Invasive angiography revealed similar stenosis in LAD (C) and FFR measured in LAD was 0.70, which suggests presence of myocardial ischemia (D). Red arrows in (A) and (C) show same intermediate lesion in proximal LAD.

• 

  Fig. 4 Case with discrepancy between myocardial perfusion imaging and fractional flow reserve. A. 72-year-old woman with stable angina who underwent myocardial SPECT. Reversible perfusion defect was absent. B. Invasive coronary angiography revealed severe 3-vessel disease (arrows). C. FFR was 0.69 in left anterior descending coronary artery and 0.73 in left circumflex artery, respectively. FFR = fractional flow reserve, LAD = left anterior descending coronary artery, LCX = left circumflex artery, SPECT = single photon emission computed tomography

• 

  Fig. 5 Wave intensity analysis and concept of instantaneous wave-free ratio (iFR). Upper panel shows example of wave intensity analysis. Different types of waves originating from proximal and distal (from microcirculatory beds) sites during entire cardiac cycle are presented. After beginning of diastole and before start of systole, there is wave free period in which microvascular resistance is minimized and constant. iFR is calculated by ratio of proximal and distal pressures during this period (lower panel).

• 

  Fig. 6 Non-invasive hemodynamic assessment using coronary CT angiography and computational fluid dynamics. With recent advancement of computational fluid dynamics, non-invasive hemodynamic assessment has become feasible. Adding physiological modeling to coronary CT angiography-derived 3-dimensional coronary artery geometry enables assessment of several hemodynamic parameters, such as wall shear stress (A), pressure gradient (B), and fractional flow reserve (FFRCT) (C).

• 

  Fig. 7 Case example of microvascular disease. 69-year-old female patient presented with stable angina. Despite positive exercise stress test (ST segment depression in inferior and lateral leads) (A), there was no significant coronary artery stenosis (B). Invasive physiologic assessment was performed and fractional flow reserve, coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) were 0.94, 1.4, and 39, respectively (C). As there was no significant epicardial disease (high fractional flow reserve), low CFR and high IMR indicate presence of microvascular disease.

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