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Background The interaction of immunological determinants and classic cardiovascular risk factors can accelerate the development of cardiac allograft vasculopathy (CAV) with deleterious consequences for the graft function in heart transplantation (HTx). When it comes to immunological risk assessment, inverse CD4/CD8 ratio can be a poor prognostic marker in coronary artery disease, but its influence is unclear in CAV. Aim To evaluate the role of the T-lymphocyte count in peripheral blood as well as CD4/CD8 ratio as a predictive marker for CAV severity in a very long-term follow-up after HTx. Methods We performed a retrospective analysis of patient data collected during routine clinical follow-up visits. These data included innate and adaptive immune cell count in peripheral blood (lymphocyte count, CD3+, CD4+, CD8+ and CD19+ T cells and NK cells). Results The study population consisted of 174 patients with a mean follow-up of 13.1±6.5 years and a mean age at the time of HTx of 45.2±15.0 years. CAV was diagnosed in 71 patients (40.8%), more than half of which underwent interventional procedure or surgical therapy (n=40, 56.3%). A comparison of the cytoimmunological profile of patients with no CAV or mild disease (group 1, n=134) vs. with CAV requiring treatment (group 2, n=40), revealed significantly reduced percentage of CD4+ T cells (46.4±11.4% vs. 41.2±9.6%, p=0.01) and elevated percentage of CD8+ T lymphocytes in group 2 (28.3±14.1% vs. 35.8±13.7%, p=0.003). Thus, the CD4/CD8 ratio was altered in therapy requiring CAV (2.3±2.0 vs. 1.5±1.0, respectively, p Conclusions Decreased CD4+ T cell count along with increased cytotoxic T lymphocyte count resulting in inverse CD4/CD8 ratio is associated with increased CAV severity in HTx. Given the possible interactions with the immunosuppressive agents and prednisolone, monitoring of the cytomimmunological profile can help identify patients at risk and be useful in establishing therapeutic strategies. Funding Acknowledgement Type of funding sources: None.

Background When it comes to lipid-lowering therapy, the primary goal is still to reduce the low-density lipoprotein levels. Although remnant cholesterol (RC), including predominantly intermediate- and very-low-density lipoproteins, is a known cardiovascular risk factor, reliable reference values, as well as therapy strategies, are yet to be validated. Additionally, the role of RC after heart transplantation is still unclear. Aim To assess the clinical and prognostic relevance of lipid profile and, in particular, of remnant cholesterol in very long-term follow-up after HTx. Methods We performed a retrospective analysis of the clinical and laboratory parameters collected at last follow-up in an outpatient setting. Additionally, remnant cholesterol levels were estimated using the formula (in mg/dL): remnant cholesterol = total cholesterol – (HLD-C + LDL-C). Results Out of 174 patients with a mean age of 45.2±15.0 years at the time of HTx and a mean follow-up of 13.1±6.5 years, 142 (81.6%) were on statin treatment. Mean cholesterol level was borderline high (184.1±48.4 mg/dL), whereas mean LDL and triglyceride values were markedly elevated (103.6±39.2 and 161.8±83.8 mg/dL, respectively). HDL results were found to be 57.1±17.5 mg/dL. Statin treatment was associated with significantly lower LDL levels (124.6±53.5 vs. 98.8±33.6 mg/dL on statins, p=0.013), but failed to show prognostic relevance in a univariate cox-regression analysis (HR 0.79, 95% CI 0.37 – 1.72, p=0.57). RC was elevated in comparison to the background population with a mean level of 23.5±17.3 mg/dL (24.2±18.1 in male and 21.3±14.8 mg/dL in female) and a tendency for lower values when on treatment with statins but without statistical significance (28.5±19.2 vs. 22.3±16.8 mg/dL on statins, p=0.07). Treatment with higher doses of statins showed no relevant influence on the RC levels (p=0.62). Additionally, elevated RC was associated with higher C-reactive protein values as a sign of systemic inflammation (CRP >0.5 mg/dL, OR 1.1, 95% CI 1.007 – 1.046, p=0.007). In a multivariate cox-regression analysis (adjusted for total cholesterol, LDL and triglycerides) RC was identified as a significant factor influencing mortality (HR 1.11, 95% CI 1.05 – 1.17, p Conclusions When addressing dyslipidaemia in heart transplantation, statin therapy can help reduce LDL levels, but this approach seems to be insufficient in achieving clinical benefit. Remnant cholesterol is a factor, which has proinflammatory properties and can potentially influence the prognosis in HTx. The possible therapeutic alternatives for this overseen component of the lipid profile are yet to be elucidated. Funding Acknowledgement Type of funding sources: None.

Background Thromboembolic events, including stroke, are typical complications of COVID-19. Whether arrhythmias, frequently described in severe COVID-19, are disease-specific and thus promote strokes is unclear. We investigated the occurrence of arrhythmias, and stroke during rhythm monitoring in critically ill COVID-19, compared to severe pneumonias of other origin. Methods Recruited were 120 critically ill patients requiring mechanical ventilation in three European tertiary hospitals, including n=60 COVID-19, matched according to risk factors for occurrence of arrhythmias to n=60 patients from a retrospective consecutive cohort of severe pneumonias of other origin. Results Arrhythmias, mainly atrial fibrillation (AF), were frequent in COVID-19. However, when compared to nonCOVID-19, no difference was observed with respect to ventricular tachycardias (VT) and relevant bradyarrhythmias (VT 10.0 vs. 8.4%, p=ns and asystole 5.0 vs. 3.3%, p=ns) with consequent similar rates of cardiopulmonary resuscitation (6.7 vs. 10.0% p=ns). AF was even more common in nonCOVID-19 (AF 18.3 vs. 43.3%, p=0.003; newly onset AF 10.0 vs. 30.0%, p=0.006) which resulted in higher need for electrical cardioversion (6.7 vs. 20.0%, p=0.029). Despite these findings and comparable rates of therapeutic anticoagulation (TAC), the incidence of stroke was higher in COVID-19 (6.7.% vs. 0.0, p=0.042). These events happened also in absence of AF (50%) and with TAC (50%). Conclusion Arrhythmias were common in severe COVID-19, consisting mainly of AF, yet less frequent than in matched pneumonias of other origin. A contrasting higher incidence of stroke independent of arrhythmias observed also with TAC, seems to be an arrhythmia-unrelated disease-specific feature of COVID-19. Funding Acknowledgement Type of funding sources: None. Figure 1