Poor Glycemic Control Correlates with Worse Myocardial Flow Measured by Ammonia-13 Positron Emission Tomography in Cardiac Transplant Recipients.

PURPOSE: Increased hemoglobin A1C was reported to be a predictor of angiographically detected CAV. Our study examined the impact of glycemic control on myocardial blood flow (MBF) measured by 13 N-ammonia positron emission tomography (PET) in transplant recipients.

METHODS: We reviewed the records of patients who had heart transplant in the past 5 years at our center, and who had regadenoson-stress 13 N-ammonia PET imaging. Three PET flow parameters were measured: stress MBF, myocardial flow reserve (MFR), and coronary vascular resistance (CVR = systolic blood pressure / stress MBF). Age, time from heart transplant to PET imaging, cold ischemia time during transplant, history of ≥ 2R cellular rejection, cholesterol level and A1C within 3 months of PET were recorded as potential risk factors. Correlations between PET and potential risk factors were analyzed (Pearson and Spearman's rank). Mann-Whitney test was used to compare PET flow between patients with A1C < 6.5% and A1C ≥ 6.5%.

RESULTS: 57 patients (median age 57.6 years, 73% men) were identified. Median time from transplant to PET imaging was 25 months. Median stress MBF was 2.8 (2.3-3.2) ml/min/g, CVR was 46.7 (39.1-54.0) mmHg/ml/min/g, and MFR was 3.0 (2.6-3.6). A1C (median 6.4%) correlated significantly with stress MBF: r -0.395 (P 0.006), and with CVR: r 0.392 (P 0.006). Time from transplant to PET imaging showed weaker correlation with stress MBF: r -0.284 (p 0.032) and CVR: r 0.279 (p 0.035). Patients with A1C < 6.5% had significantly higher stress MBF (median 3.0 VS. 2.4, P 0.002), and lower CVR (median 42.1 VS. 52.8, P 0.022) compared to patients with A1C ≥ 6.5% (Fig. 1). MFR was also higher in patients with A1C < 6.5% (3.3 VS. 2.8, P 0.079), although not significant.

CONCLUSION: Time from heart transplant and A1C level significantly correlated with MBF by 13 N-ammonia PET. Patients with high HbA1C level had significantly lower MBF, suggesting that glycemic control may have an important role in prevention of CAV.