Use of a Single ¹¹C-Meta-Hydroxyephedrine Scan for Assessing Flow–Innervation Mismatches in Patients with Ischemic Cardiomyopathy

Abstract

Mismatch between areas of reduced myocardial blood flow (MBF) and reduced myocardial innervation (defect areas) may be used to estimate the risk for ventricular arrhythmias. The presence of a mismatch zone can be derived using a combined protocol consisting of both an MBF scan and an 11 C-meta-hydroxyephedrine ( 11 C-HED) scan. The rate of influx from blood to myocardium (K 1 ) of 11 C-HED is proportional to MBF and can potentially be used as an index for defining MBF defects. The aim of this study was to assess whether K 1 derived from an 11 C-HED scan can be used as an index of MBF, potentially allowing for an assessment of MBF-innervation mismatch areas from a single 11 C-HED scan. Methods: Seventeen patients with known ischemic cardiomyopathy underwent dynamic 15 O-water and 11 C-HED scans. Discrete arterial blood samples were taken during 11 C-HED scans for metabolite correction of the image-derived input function. 11 C-HED influx rate was obtained using a single-tissue-compartment model and compared with transmural MBF (MBF T ), defined as MBF as measured with 15 O-water multiplied by perfusable tissue fraction. Defect sizes were obtained from parametric K 1 and MBF T images, using 50% of a remote control segment as the cutoff value. Results: There was a significant correlation between MBF T and K 1 (y 5 0.40x 1 0.05 mLÁg −1 Ámin −1 , r 5 0.80, P , 0.001), although K 1 was significantly lower than MBF T (slope of the regression line significantly different from 1, P , 0.001). Correlation between MBF T and K 1 defect sizes was high (y 5 0.89x 1 1.38%, r 5 0.95, P , 0.001), with no significant difference in mean defect size based on K 1 or MBF T (20.9% ± 11.3% and 20.1% ± 10.7% for MBF T and K 1 , respectively, P 5 0.41). Conclusion: 11 C-HED influx rate K 1 can be used as an alternative to a separate MBF scan for assessing mismatch areas between MBF and myocardial innervation.

Noninvasive Quantification of Myocardial 11C-Meta-Hydroxyephedrine Kinetics

“…Considering that K 1 itself can be used as a marker of myocardial blood flow in this patient group (22), this suggests that both innervation parameters have a significant contribution of myocardial blood flow to their signal and this has to be considered. However, the strength of the correlation was significantly higher for retention index than for V T , advocating use of V T as a less flow-dependent marker of innervation.…”

Automatic Extraction of Myocardial Mass and Volume Using Parametric Images from Dynamic Nongated PET

“…This advantage provides an inherent filtering step in the analysis, potentially resulting in higher reliability, accuracy, and precision of the estimates than is possible with electrocardiogramgated images. The cutoffs used for removal of blood regions from parametric images were based on previous studies (20). The twothirds cutoff used during the radial profile step of segmenting the LV wall, and the 3-cm maximum distance of LV tissue from the blood, were chosen empirically because these values showed the most consistent results and required minimal manual intervention in a pilot subset of 10 patients.…”

“…0.60, V A 1 V V . 0.75, or anatomic tissue fraction , 0.25 were set to 0 as described previously (20).…”

Impaired Myocardial Sympathetic Innervation Is Associated with Diastolic Dysfunction in Heart Failure with Preserved Ejection Fraction: 11C-Hydroxyephedrine PET Study

“…To quantify perfusion abnormality, we estimated the 11 C-HED influx rate from blood to myocardium (mLÁg 21 Ámin 21 ) using a single-tissue-compartment model (21) as an indicator of myocardial blood flow (22).…”