An Algorithm for Individual Dosage in Cadmium–Zinc–Telluride SPECT-Gated Radionuclide Angiography

The aim of the present study was to test an individualised dose without compromising the ease of analysing data when performing equilibrium radionuclide angiography (ERNA) using cadmium–zinc–telluride (CZT) SPECT. From March 2018 to January 2019, 1650 patients referred for ERNA received either an individualised dose of 99mTc-labeled human serum albumin (HSA) according to their age, sex, height, and weight (n = 1567), or a standard dose of 550 MBq (n = 83). The target count rate (CRT) was reduced every two months from 2.7 to 1.0 kcps. A final test with a CRT of 1.7 kcps was run for three months to test whether an agreement within 2% points for the determination of LVEF, on the basis of only two analyses, was obtainable in at least 95% of acquisitions. All the included ERNAs were performed on a dedicated cardiac CZT SPECT camera. When using the algorithm for an individualised dose, we found that agreement between the measured and predicted count rate was 80%. With a CRT of 1.7 kcps, the need for more than two analyses to obtain sufficient agreement for LVEF was 4.9%. Furthermore, this resulted in a mean dose reduction from 550 to 258 MBq. Patients’ weight, height, sex, and age can, therefore, be used for individualising a tracer dose while reducing the mean dose.

Long-term follow-up of cardiac resynchronization therapy patients with non-ischemic dilated cardiomyopathy assessed by radionuclide angiography

Background While the beneficial effects of cardiac resynchronization therapy (CRT) have been widely investigated soon after CRT implantation, relatively few data are available on long-term clinical outcomes of CRT recipients. Aim To investigate long-term outcomes of CRT patients with non-ischemic dilated cardiomyopathy stratified as responders and non-responders according to radionuclide angiography. Methods Consecutive heart failure patients with non-ischemic dilated cardiomyopathy undergoing CRT implantation at our University Hospital between 2007 and 2013 were enrolled. All patients were assessed with equilibrium Tc99 radionuclide angiography at baseline and after 3 months of CRT. Left ventricular (LV) ejection fraction was computed on the basis of relative end-diastolic and end-systolic counts, and intraventricular dyssynchrony was derived by Fourier phase analysis. Response to CRT was defined by an absolute increase in LV ejection fraction (LVEF) ≥5% at 3-month follow-up. Clinical outcome was assessed after 10 years through hospital records review. Results Forty-seven patients (83% men, 63±11 years) were included in the study. At 3 months, 25 (53%) patients were identified as CRT responders according to LVEF increase (from 26±8 to 38±12%, p<0.001). In these patients, LV dyssynchrony decreased from 59±30° to 29±18° (p<0.001). Twenty-two (47%) patients were defined as non-responders. No significant changes in LVEF and LV dyssynchrony (50±30° vs. 38±19°, p=0.07) were observed in non-responders. At long-term follow-up (11±2 years), all-cause and cardiac mortality rates were 24% and 12% in responders vs. 32% and 27% in non-responders, respectively (p=ns). Heart transplantation was performed in 3 patients. One (4%) patient among CRT responders compared with 6 (27%) patients among non-responders died of worsening heart failure (p=0.03). Conclusions Although late overall mortality of non-ischemic CRT recipients was not significantly different between mid-term responders and non-responders, CRT responders were at lower risk of worsening heart failure death. Funding Acknowledgement Type of funding source: None