Simplification of coronary continuous thermodilution

Abstract Background Continuous coronary thermodilution with saline permits the accurate measurement of volumetric blood flow (Q) and absolute microvascular resistance. However, this requires repositioning of the temperature sensor by the operator to measure the entry temperature of the saline infusate, denoted as Ti. Purpose We evaluated if Ti could be predicted based upon known parameters without compromising the accuracy of calculated Q. This would significantly simplify the technique and render it completely operator independent. Methods In a derivation cohort of 371 patients with Q measured both at rest and during hyperaemia, multivariate linear regression was used to derive an equation for the prediction of Ti. Agreement of standard Q (calculated with measured Ti) and simplified Q (calculated with predicted Ti) was assessed in a validation cohort of 120 patients that underwent repeat Q measurements. The accuracy of simplified Q was assessed in a second validation cohort of 23 patients with [15O]H2O positron emission tomography (PET)-derived Q measurements. Results Simplified Q exhibited strong agreement with standard Q (r=0.94 [95% CI 0.93-0.95], ICC 0.94 [95% CI 0.92-0.95], both p<0.001) (Figure 1). Simplified Q exhibited excellent agreement with PET-derived Q (r=0.86 [95% CI 0.75-0.92], ICC=0.84 [95% CI 0.72-0.91], both p<0.001) (Figure 2). Compared with standard Q, there was no statistically significant difference between correlation coefficients (p=0.29) or standard deviations of absolute differences with PET-derived Q (p=0.85). Conclusion Assessing volumetric coronary flow by continuous thermodilution with predicted Ti instead of measured Ti does not compromise its accuracy when compared to [15O]H2O PET. It significantly simplifies the technique and renders absolute coronary flow measurements completely operator independent.Figure 1.AgreementFigure 2.Accuracy