Gottliebson WM, Effat MA. Influence of heart rate on fractional flow reserve, pressure drop coefficient, and lesion flow coefficient for epicardial coronary stenosis in a porcine model. Am J Physiol Heart Circ Physiol 300: H382-H387, 2011. First published October 8, 2010 doi:10.1152/ajpheart.00412.2010.-A limitation in the use of invasive coronary diagnostic indexes is that fluctuations in hemodynamic factors such as heart rate (HR), blood pressure, and contractility may alter resting or hyperemic flow measurements and may introduce uncertainties in the interpretation of these indexes. In this study, we focused on the effect of fluctuations in HR and area stenosis (AS) on diagnostic indexes. We hypothesized that the pressure drop coefficient (CDPe, ratio of transstenotic pressure drop and distal dynamic pressure), lesion flow coefficient (LFC, square root of ratio of limiting value CDP and CDP at site of stenosis) derived from fluid dynamics principles, and fractional flow reserve (FFR, ratio of average distal and proximal pressures) are independent of HR and can significantly differentiate between the severity of stenosis. Cardiac catheterization was performed on 11 Yorkshire pigs. Simultaneous measurements of distal coronary arterial pressure and flow were performed using a dual sensor-tipped guidewire for HR Ͻ 120 and HR Ͼ 120 beats/min, in the presence of epicardial coronary lesions of Ͻ50% AS and Ͼ50% AS. The mean values of FFR, CDPe, and LFC were significantly different (P Ͻ 0.05) for lesions of Ͻ50% AS and Ͼ50% AS (0.88 Ϯ 0.04, 0.76 Ϯ 0.04; 62 Ϯ 30, 151 Ϯ 35, and 0.10 Ϯ 0.02 and 0.16 Ϯ 0.01, respectively). The mean values of FFR and CDPe were not significantly different (P Ͼ 0.05) for variable HR conditions of HR Ͻ 120 and HR Ͼ 120 beats/min (FFR, 0.81 Ϯ 0.04 and 0.82 Ϯ 0.04; and CDPe, 95 Ϯ 33 and 118 Ϯ 36). The mean values of LFC do somewhat vary with HR (0.14 Ϯ 0.01 and 0.12 Ϯ 0.02). In conclusion, fluctuations in HR have no significant influence on the measured values of CDP e and FFR but have a marginal influence on the measured values of LFC. However, all three parameters can significantly differentiate between stenosis severities. These results suggest that the diagnostic parameters can be potentially used in a better assessment of coronary stenosis severity under a clinical setting. coronary disease; hemodynamics; catheterization CORONARY ANGIOGRAPHY is the current gold standard for detecting epicardial coronary artery disease. Augmenting this anatomical data with coronary functional parameters (pressure, flow, and/or velocity) provides unique information that facilitates fully informed therapeutic decision making in the catheterization laboratory. Several invasive functional approaches have been used for the past several years within the cardiac catheterization laboratory that allow for a determination of the functional significance of epicardial coronary stenoses. These methods include measurement of coronary flow reserve [CFR, the ratio of hyperemic flow to basal flow (10) (9), an advanced func...
