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Background/Introduction Cardiac contractility modulation (CCM) is an FDA approved device therapy for systolic heart failure patients with narrow QRS complex who are symptomatic despite optimal medical therapy. It is used in patients with a wide range of different cardiomyopathies. However, little is known whether the therapy is comparably effective in different entities. Purpose This work investigated the long-term therapeutic effect in patients with ischemic (ICMP) compared to patients with non-ischemic cardiomyopathy (NICMP). Methods 102 patients of our single center registry with known form of cardiomyopathy were included in this retrospective analysis (from 2011–2019). In 68 patients data of a clinical 3-year follow-up were available. The actual mortality rate within one and three years was compared with the one predicted by the MAGGIC risk score and compared between the two groups. In addition, changes in NYHA class, left ventricular ejection fraction (LVEF), LV end-diastolic diameter (LVEDD) and NT-proBNP values were compared as functional parameters. Results Patients with an ICMP (65%) were older (67±1 vs. 57±2 years (SD±SEM); p Conclusions NICMP patients had a significantly greater increase in LVEF. Moreover, reverse remodeling with reduction of the LVEDD was only observed in NICMP patients. In summary, significant differences in functional therapy response could be identified between ICMP vs. NICMP patients. Funding Acknowledgement Type of funding source: None

Aims Atrial fibrillation (AF) prevalence increases with advanced stages of left ventricular (LV) dysfunction. Remote proarrhythmic effects of ventricular dysfunction on atrial electrophysiology remain incompletely understood. We hypothesized that repolarizing K(2P)3.1 K+ channels, previously implicated in AF pathophysiology, may contribute to shaping the atrial action potential (AP), forming a specific electrical substrate with LV dysfunction that might represent a target for personalized antiarrhythmic therapy.Methods and results A total of 175 patients exhibiting different stages of LV dysfunction were included. Ion channel expression was quantified by real-time polymerase chain reaction and Western blot. Membrane currents and APs were recorded from atrial cardiomyocytes using the patch-clamp technique. Severely reduced LV function was associated with decreased atrial K(2P)3.1 expression in sinus rhythm patients. In contrast, chronic (c) AF resulted in increased K(2P)3.1 levels, but paroxysmal (p) AF was not linked to significant K(2P)3.1 remodelling. LV dysfunction-related suppression of K(2P)3.1 currents prolonged atrial AP duration (APD) compared with patients with preserved LV function. In individuals with concomitant LV dysfunction and cAF, APD was determined by LV dysfunction-associated prolongation and by cAF-dependent shortening, respectively, consistent with changes in K(2P)3.1 abundance. K(2P)3.1 inhibition attenuated APD shortening in cAF patients irrespective of LV function, whereas in pAF subjects with severely reduced LV function, K(2P)3.1 blockade resulted in disproportionately high APD prolongation.Conclusion LV dysfunction is associated with reduction of atrial K(2P)3.1 channel expression, while cAF leads to increased K2P3.1 abundance. Differential remodelling of K(2P)3.1 and APD provides a basis for patient-tailored antiarrhythmic strategies.

Background TASK-1 (K2P3.1) is an atrial-specific two-pore domain potassium channel that is significantly upregulated in atrial fibrillation (AF) patients resulting in shortened atrial action potential duration (APD). Inhibition of TASK-1 in human atrial cardiomyocytes reverses AF-related APD shortening to values observed in patients with sinus rhythm (SR). By in silico-modelling and experimental characterization of drug binding sites, doxapram was identified as specific inhibitor of TASK-1. Purpose In this study, we investigated the antiarrhythmic efficacy of doxapram in a porcine model of AF to convert and suppress AF. Methods We established a new porcine model of persistent AF without induced tachymyopathy. AF was induced in domestic pigs by intermittent atrial burst stimulation using implanted pacemakers. During AF episodes, burst stimulation was inhibited by an integrated pacemaker biofeedback algorithm. AV-node ablation was performed to prevent AF-associated heart failure. All pigs underwent catheter-based electrophysiological investigations prior to and after 14 days doxapram treatment. Pigs in the treatment group received intravenous applications of doxapram twice per day. Rhythm status was continuously recorded by intracardiac long-term ECG monitors. The application of doxapram for cardioversion and long term suppression of AF in pigs with persistent AF was evaluated. Subsequent to the doxapram treatment, porcine cardiomyocytes were isolated from right and left atria and electrophysiologically investigated by patch-clamp and multi-electrode experiments. Atrial electrical remodeling was characterized by analyses of ion channel expression at mRNA and protein levels. Results TASK-1 mRNA, protein and transmembrane current were significantly increased in AF pigs compared to SR controls, resulting in shortened atrial APDs. In doxapram-treated AF pigs the AF burden was significantly reduced. After 14 days treatment with doxapram, TASK-1 currents and atrial APDs recorded in porcine cardiomyocytes were reduced and similar to values of SR animals. Doxapram could be successfully applied for cardioversion in pigs with persistent AF. On average, cardioversion was observed 3 minutes after doxapram application. Conclusion Doxapram significantly suppressed AF episodes and normalized cellular electrophysiological characteristics in a porcine model of AF through inhibition of the TASK-1 ion channel. Furthermore, doxapram rapidly converted AF into SR in pigs. Therefore, doxapram might serve as a new antiarrhythmic drug to treat AF in patients.