Serial stenosis assessment-can we rely on invasive coronary physiology

Abstract

Atherosclerosis is a widespread disease affecting coronary arteries. Diffuse atherosclerotic disease affects the whole vessel, posing difficulties in determining lesion significance by angiography. Research has confirmed that revascularization guided by invasive coronary physiology indices improves patients' prognosis and quality of life. Serial lesions can be a diagnostic challenge because the measurement of functional stenosis significance using invasive physiology is influenced by a complex interplay of factors. The use of fractional flow reserve (FFR) pullback provides a trans-stenotic pressure gradient (ΔP) for each of the lesions. The strategy of treating the lesion with greater ΔP first and then reevaluating another lesion has been advocated. Similarly, non-hyperemic indices can be used to assess the contribution of each stenosis and predict the effect of lesion treatment on physiology indices. Pullback pressure gradient (PPG) integrates physiological variables of coronary pressure along the epicardial vessel and characteristics of discrete and diffuse coronary stenoses into a quantitative index that can be used to guide revascularization. We proposed an algorithm that integrates FFR pullbacks and calculates PPG to determine individual lesion importance and to guide intervention. Computer modeling of the coronaries and the use of non-invasive FFR measurement together with mathematical algorithms for fluid dynamics can make predictions of lesion significance in serial stenoses easier and provide practical solutions for treatment. All these strategies need to be validated before widespread clinical use.

Keywords: IFR; coronary artery stenosis; fractional flow reserve (FFR); pullback pressure gradient; serial stenosis.

Figure 1

The schematic diagram of serial coronary artery stenoses and pressures measured using pressure wire Pa—proximal arterial pressure; Pd, distal arterial pressure; Pm, medial (between lesion) pressure.

Figure 2

Serial lesion assessment by pullback FFR measurement using Coroventis CoroFlow cardiovascular software (Coroventis AB, Uppsala, Sweden), followed by PCI of the lesion with greatest ΔP and retesting after stent implantation leading to the deferral of further intervention due to an increase in FFR.

Figure 3

Distal left main lesion evaluation with downstream stenosis in LAD using Coroventis CoroFlow cardiovascular software (Coroventis AB, Uppsala, Sweden). Placing a pressure sensor in distal LAD FFR 0.76 was acquired while placing a sensor in distal Cx, free from disease, obtained FFR was 0,86. The lesion of distal LM was deemed insignificant.

Figure 4

Serial lesion assessment using iFR and co-registration with “Sync Vision” software (Philips Healthcare, The Netherlands). The images show mid-LAD serial lesions assessed by iFR, and each yellow dot represents a 0.01 value in iFR Reading. The white-butted line in the right image demonstrates the potential effect of stent implantation on iFR value change (ΔiFR).

Figure 5

The image represents serial lesion assessment in a 39 year-old patient using resting full-cycle ratio (RFR) and FFR pullback with papaverine as the hyperemic agent. The obtained values were abnormal for RFR and normal for FFR. The possible reason for this could be that there was a diffuse atherosclerotic disease and pullback pressure gradient (PPG showing an intermediate value of 0.65) and the operator decided to defer revascularization due to a normal FFR value and diffuse disease in the left main and LAD.

Figure 6

The diagram demonstrates practical approach to a patient with serial stenoses using invasive physiology (iFR – instantaneous wave free ratio, FFR – fractional flow reserve and PPG – pullback pressure gradient).