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Funding Acknowledgements Type of funding sources: None. Background Current evidence suggests that incremental levels of PEEP generate an increase in right intracavitary pressures, diminishing venous return and consequently lessening left ventricular preload and stroke volume, resulting in a significant decrease of cardiac output. Nonetheless, most studies regarding these interactions have been done in patients requiring mechanical ventilation for non-cardiac disorders or in animals. We studied the effects of incremental levels of PEEP on cardiac intracavitary pressures and hemodynamics in mechanically ventilated patients admitted into the Cardiac Intensive Care Unit. Purpose We aimed to model how increments in PEEP alter cardiac output and other hemodynamic variables in patients with cardiac disfunction. Methods We included 14 mechanically ventilated patients admitted into a Cardiac Intensive Care Unit from 2018 to 2020. Data on intracavitary pressures and hemodynamics were recorded via Swan-Ganz catheterization and echocardiographic imaging. We documented measurements for all variables of interest at three different levels of PEEP: 5cmH2O, 10cmH2O and 15cmH2O. We conducted general descriptive statistics, mean comparison tests for paired data and linear regression models with Stata version 12.0 (StataCorp LP, College Station, TX). Results 7 (50%) patients admitted in the study had cardiogenic shock, 11 (79%) patients were mechanically ventilated in a volume-controlled setting and 3 (21%) were on pressure support ventilation. Seven (50%) patients needed vasoactive drugs during the study. Only 1 (7%) patient required an intra-aortic balloon pump. Seven (50%) patients had a visual left ventricular ejection fraction lesser than 40% and 3 (21%) had a moderate-severe mitral regurgitation. Paired mean testing by groups associated to gains of PEEP revealed statistically significant increments in Mean Pulmonary Artery Pressure (mPAP), Pulmonary Capillary Wedge Pressure (PCWP) and Central Venous Pressure (CVP). Inversely, increments of PEEP were linked to significant decrements in Cardiac Output (CO) [Figure 1 & Table 1]. Conclusions In mechanically ventilated patients admitted into the Cardiac Intensive Care Unit, rises in PEEP are associated to increments in intracavitary cardiac pressures, and inversely, with decrements in cardiac output. Although our findings are statistically significant, we have yet to clarify whether these are clinically meaningful, specifically within PEEP increments of 5 to 10cmH2O, the usual range in clinical practice.

Funding Acknowledgements Type of funding sources: None. Background Takotsubo syndrome (TKS) is characterized by the appearance of apical reversible dyskinesia in its typical form. Electrocardiogram (ECG) in the acute phase (<12 from symptom onset) generally shows anterior ST segment elevation. Nonetheless, other atypical forms of TKS have been described depending on the location of the dyskinetic segments, such as, mid-ventricular, basal and focal forms. Considering the different segments involved in these atypical forms, it seems reasonable to consider that ST changes in acute phase ECG could be different. Purpose To compare ECG in the acute phase of typical TKS versus mid-ventricular TKS, as it was the more frequent form of atypical TKS in our registry. Methods Patients included in the prospective TKS registry of our center according to the Mayo Clinic diagnostic criteria, with the first ECG performed less than 12 hours from the symptoms onset were reviewed. All cardiac left ventriculographies were reviewed to ensure a correct classification of the different types of TKS. Results A total of 297 patients were included in our local registry. 80 patients met our study inclusion criteria. 56 ECGs of typical apical TKS were compared to 24 ECGs of atypical midventricular TKS. There were no differences between the baseline characteristics in both groups, except for mid-ventricular TKS, that was more frequently triggered by physical stressor. Regarding the ECG analysis, the main difference found in our serie was related to ST-segment deviation (Table 1). While ST-segment elevation was more common in typical TKS than in atypical TKS (73% vs 50%), ST-segment depression (generally in inferior leads) was observed in 54% of patients with atypical TKS and in no patient with typical TKS (figure 1). Conclusion The different location of dyskinesia between typical TKS and mid-ventricular TKS is associated to significant differences in the ECG obtained in the first hours after the onset of the clinical symptoms. The presence of ST-segment depression is highly suggestive of mid-ventricular TKS. ECG characteristicsTypical (n = 56)Midventricular (n = 24)pSTe > 1mm, no (%)41 (73)12 (50)0,044STd >0,5 mm, no (%)013 (54)< 0,001T wave inversion, no (%)12 (21)4 (17)0,626Q wave, no (%)22 ( 39)12 (50)0,374cQT, mean (SD)445 (54)438 (37)0,578QRS low voltages*, n (%)9 ( 16)1 (4)0,328STe ST-segment elevation, STd: ST-segment depression, cQT: corrected QT interval *Voltages <5mm in all limb leads or <10mm in all precordial leads Abstract Figure. 12-lead ECG and left ventriculography