Use of a single [11C]-meta-hydroxy- ephedrine scan protocol for assessing flow innervation mismatch in patients with ischemic cardiomyopathy

Mismatch between areas of reduced myocardial blood flow (MBF) and reduced myocardial innervation (’defect’ areas) may be used to predict ventricular arrhythmias. The presence of a mismatch zone can be derived from a combined protocol consisting of both an MBF and [C]-meta-hydroxyephedrine ([C]HED) scans. The rate of influx of [C]HED from blood to myocardium (K1) is proportional to MBF and could potentially be used as an index for defining perfusion defects. The aim of this study was to assess whether K1 derived from an [C]HED scan can be used as an index of MBF, allowing for a single [C]HED scan protocol for defining MBF-innervation mismatch areas. Methods: 17 patients with known ischemic cardiomyopathy underwent dynamic [O]H2O and [ C]HED scans. Discrete arterial blood samples were taken during [C]HED scans for metabolite correction of the image derived input function. [C]HED influx rate was obtained using a single tissue compartment model and compared to transmural MBF (MBFT), defined as MBF multiplied by perfusable tissue fraction. Defect sizes were obtained from parametric K1 and MBFT images, using 50% of a remote control segment as cut-off value. Results: There was a significant correlation of MBFT and K1 (r 2 = 0.65, slope = 0.40, p < 0.001) although K1 was significantly lower than MBFT (slope of the linear fit significantly different from 1, p < 0.001). In addition, correlation between MBFT derived and K1 derived defect sizes was high (r 2 = 0.91, slope = 0.90, p < 0.001) with no significant difference in defect size based on K1 or MBFT (20.9±11.3% and 20.1±10.7% for MBFT and K1, respectively, p = 0.80). Conclusion: [11C]HED influx rate K1 can be used as an alternative to a separate MBF scan for assessing mismatch areas between reduced MBF and reduced myocardial innervation. This eliminates the use of a separate MBF scan and consequently reduces scan duration, radiation dose and risk of patient motion between scans.