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Funding Acknowledgements Type of funding sources: None. Introduction Department for nuclear medicine in the University medical centre Ljubljana provides nuclear medicine diagnostic procedures for approximately 1.000.000 inhabitants of Slovenia. As many countries in Europe, Slovenia was faced with the first wave of the COVID-19 pandemic in early spring of 2020. Since our country is situated next to the northern part of Italy, where the situation was critical, our Ministry of health issued specific recommendations in March 2020. The aim was to increase hospital capacities for COVID-19 patients through limiting non-urgent diagnostic tests including myocardial perfusion scintigraphy (MPS) and to minimize the spread of the virus into hospital departments. The epidemiologic situation of the first wave resolved within 3 months. In the second wave of the pandemic in autumn 2020, the recommendations on patient care in non COVID-19 cases were less limiting to avoid worsening of non COVID-19 related diseases and patient prognosis. Purpose The aim of our study was to evaluate the influence of the COVID-19 pandemic on MPS in our medical institution. Methods Data on numbers of MPS, clinical characteristics of the patients and findings of MPS were prospectively collected for the first wave (in spring from March 15th to June 15th 2020) and second wave (in autumn from September 15th to December 15th 2020) of the pandemic and were compared with the same periods in 2019. Results During the first wave we performed 40% less MPS, significantly more patients had pharmacological stress and were outpatients than in spring 2019. There were no significant differences in other clinical characteristics and MPS findings (Table 1 and Figure 1). In autumn 2020 we reorganized our schedule to increase the number of patients, which was once again comparable to previous year’s autumn. Although the number of patients was comparable, patients were now significantly older and had more often pharmacological stress, but there were no significant differences in other clinical data or MPS findings (Table 1 and Figure 1). Conclusions In our hospital, during the first wave of COVID-19 pandemic, we performed significantly less MPS than in the same period of the previous year. To minimize the possibility of virus transmission from asymptomatic patients, we followed international recommendations and avoided exercise stress tests but increased the percentage of pharmacological stress tests. A similar approach regarding the type of stress tests was chosen for the second wave in autumn of 2020. However, we decided to increase the number of MPS performed, in order to lessen the negative impact of the pandemic on non COVID-19 related diseases, focusing on coronary artery disease.

Funding Acknowledgements Type of funding sources: None. Background In selected patients, stress-only myocardial perfusion imaging (MPI) has been proposed as an alternative to rest-stress MPI to reduce radiation exposure and enhance laboratory efficiency. The use of attenuation correction improves the diagnostic accuracy of stress-only imaging. However, criteria for selecting appropriate patients for stress-first imaging protocol are not uniform. There is limited data about stress-only MPI in hospitalized patients. The purpose of this study was to compare the proportion of suitable hospitalized and outpatient patients with normal MPI on a routine two-day protocol for stress-only MPI. Methods In a retrospective longitudinal cohort study, stress scintigrams (with and without attenuation correction) of consecutive hospitalized and outpatient patients who underwent MPI at our department by a routine two-day protocol and had a normal MPI were visually and semi-quantitatively re-examined. Patients with summed stress score 0 or 1 were considered as candidates for stress-only MPI. We also obtained data on the patients" clinical characteristics and their treatment. Results We studied 178 patients (mean age 68.8 ± 13.4 years, 89 hospitalized, 89 outpatient patients, 55.6 % female). Hospitalized patients were significantly older than outpatient participants (72.4 ± 13.0 vs. 65 ± 12.9 years, p < 0.001) with no significant differences in risk factors and clinical characteristics. Proportion of inpatients and outpatients suitable for stress-only MPI with and without attenuation correction is shown on Figure 1. There was no significant difference in stress-only MPI with and without attenuation correction between hospitalized and outpatient patients (Figure 1). 9.1% of patients in whom stress only MPI was possible had known coronary artery disease, whereas it was present in 25.0% of patients in whom stress-only MPI was not possible (p = 0.004). By using attenuation correction stress-only MPI could be performed in 54% of patients without known coronary artery disease. There was no difference between hospitalized patients and outpatients (52% vs. 56%, p = 0.700). Absence of coronary artery disease turned out as the only independent prognostic factor for application of stress-only MPI (odds ratio 3.433, 95% confidence interval 1.44-8.17, p = 0.003). There was no influence of hospitalization on the application of stress-only MPI. Conclusions When we choose the right patients (especially those without a known coronary artery disease) and use modern cameras that enable attenuation correction, we can perform stress-only MPI in 50% of patients with a normal MPI result. The same approach can be used for outpatients and inpatients.

Funding Acknowledgements Type of funding sources: None. Background Myocardial fibrosis is a known prognostic factor in patients with systemic right ventricle (SRV). In these patients fixed myocardial perfusion defects are a common finding and are thought to represent areas of myocardial infarction and fibrosis. However, no study has yet correlated myocardial perfusion imaging findings with cardiac magnetic resonance (CMR) imaging, which is the imaging gold standard for detecting myocardial fibrosis. Purpose Our aim was to evaluate whether fixed myocardial perfusion defects in adult patients with SRV represent myocardial fibrosis. Methods Patients with SRV followed at our outpatient clinic for congenital heart disease were prospectively included. Myocardial perfusion was evaluated with a two-day stress/rest single-photon emission computed tomography (SPECT) protocol, focal myocardial fibrosis with late gadolinium enhancement (LGE) and diffuse myocardial fibrosis with T1 mapping by CMR. The 12-segment model of the right ventricle was used to report segments with myocardial perfusion defects and fibrosis (Figure 1). Results Fifteen patients with SRV (12 patients with transposition of the great arteries following atrial switch procedure and 3 patients with congenitally corrected transposition of the great arteries; 4 (26.7%) females; mean age 34.6 ± 10.0 years) were included. Myocardial perfusion defects were present in 14 patients (93%), with predominate fixed perfusion defects (73%) and less common reversible perfusion defects (27%). Fixed myocardial perfusion defects were most frequent in anterior RV segments (figure 1), with multiple segments affected in 11 patients (median number of affected segments – 2 segments). CMR was possible in 11 (73%) patients, others had a permanent pacemaker. LGE indicating focal myocardial fibrosis was detected in only 1 (9%) patient, while increased T1 values indicating diffuse myocardial fibrosis were present in 7 (64%) patients. There was no matching between areas of fixed myocardial perfusion defects and focal myocardial fibrosis in individual patients. Conclusions In our study, fixed myocardial perfusion defects detected on SPECT in patients with SRV did not represent areas of focal myocardial fibrosis on CMR. Other causes than scar may explain the frequently reported fixed perfusion defects, such as SRV anatomy with anterior position of the outflow tract and aorta, SRV morphology with variable degree of wall thickness and hypertrophy that influences tracer accumulation and image quality, or difficulties due to complex image acquisition and interpretation. To improve the diagnostic accuracy, the use of fused imaging modalities (SPECT-CT or PET-CT) is recommended in patients with SRV. Figure 1. Bull`s eye 12-segment plots of the right ventricle (RV) representing the number of segments with fixed myocardial perfusion defects detected by SPECT (1A) and LGE by CMR (1B) in patients with SRV. ANT – anterior, FW – free wall, INF – inferior, SEP – septal wall of RV. Abstract Figure.

To investigate the impact of myocardial perfusion scintigraphy results on the decision for invasive coronary angiography in elderly patients (≥75 years) with suspected coronary artery disease hospitalized in a single tertiary medical center.In the retrospective study, data of 276 (136 elderly) consecutive hospitalized patients referred to myocardial perfusion imaging were analyzed. The clinical characteristics, myocardial perfusion scintigraphy results, invasive coronary angiography and revascularization rates and in-hospital adverse events were identified by manually reviewing the patients' records.Ischemia was found in 40.2% of patients. There was no significant difference in the proportion of ischemia between elderly and younger patients (38.2% vs. 42.1%, P=0.508). Invasive coronary angiography was performed in 64.0% of patients with ischemia and in 6.8% of patients with normal myocardial perfusion imaging (P0.001). The referral rate for invasive coronary angiography was not different between elderly and younger patients with ischemia (63.5% vs. 64.4%, P=0.848). Ischemia on myocardial perfusion imaging was the most predictive variable for a referral to invasive coronary angiography (odds ratio 31.8, 95% confidence interval 14.6-69.5, P0.001). There was no significant difference between the younger and elderly patients in revascularization rate and adverse events until discharge (39% vs. 40%, P=0.99 and 7.1% vs. 8.8%, P=0.6, respectively).Ischemia on myocardial perfusion scintigraphy is a powerful predictor for in-hospital invasive coronary angiography independent of the patient's age. Elderly patients with ischemia received invasive coronary angiography equally as their younger counterparts and have similar rates of adverse events until discharge.

Purpose Noncompaction cardiomyopathy (NCC) results as an arrest of the myocardial compaction process in the embryonic period, leading to the impaired formation of the microvasculature. Myocardial perfusion abnormalities have already been described, however, the functional impact in NCC patients remains undefined. We sought to analyze a potential correlation between myocardial ischemia and heart failure progression in patients with NCC. Methods We enrolled 37 (24 male, 13 female) patients with NCC, average age 47±15 years. Echocardiography determined left ventricular end diastolic diameter and volume (EDD and EDV) and ejection fraction (LVEF). Global longitudinal strain (GLS) postprocessing has been performed. Serum levels of NT-proBNP have been measured. Cardiac MRI has been performed to confirm the diagnosis. Myocardial SPECT was performed at rest and on stress, determining summed difference score (SDS). Significant myocardial ischemia was defined as SDS≥2. Results Myocardial ischemia has been shown in 15 patients (41%, Group A), 22 patients (59%) showed no significant ischemic changes (Group B). The two groups did not differ in sex (male 73% vs. 59% in Group B), age (48±15 years vs. 46±14 years, P=0.65), creatinine (76±14 μmol/L vs. 76±16 μmol/L, P=0.98) or bilirubin (11±6 μmol/L vs. 12±5 μmol/L, P=0.46). When compared to Group B, Group A had significantly lower LVEF (38±15% vs. 55±13% in Group B, P=0.001), higher EDD (6.3±0.9 cm vs. 5.2±0.7 cm, P Conclusion In patients with NCC myocardial ischemia correlates with lower ejection fraction and dilation of the left ventricle, leading to greater neurohumoral activation. As medical heart failure therapy has not been shown to be successful in NCC patients, progressive LV systolic dysfunction due to myocardial ischemia often warrants heart transplantation or left ventricular assist device implantation. Treatment approaches targeting myocardial ischemia, such as CD34+ cell therapy, could slow the progression of disease in NCC patients.