Recent cardiotropic drug developments have focused on cardiac myofilaments. Danicamtiv, the second direct myosin activator, has achieved encouraging results in preclinical and clinical studies, thus implicating its potential applicability in the treatment of heart failure with reduced ejection fraction (HFrEF). Here, we analyzed the inotropic effects of danicamtiv in detail. To this end, changes in sarcomere length and intracellular Ca²⁺ levels were monitored in parallel, in enzymatically isolated canine cardiomyocytes, and detailed echocardiographic examinations were performed in anesthetized rats in the absence or presence of danicamtiv. The systolic and diastolic sarcomere lengths decreased; contraction and relaxation kinetics slowed down with increasing danicamtiv concentrations without changes in intracellular Ca²⁺ transients in vitro. Danicamtiv evoked remarkable increases in left ventricular ejection fraction and fractional shortening, also reflected by changes in systolic strain. Nevertheless, the systolic ejection time was significantly prolonged, the ratio of diastolic to systolic duration was reduced, and signs of diastolic dysfunction were also observed upon danicamtiv treatment in vivo. Taken together, danicamtiv improves cardiac systolic function, but it can also limit diastolic performance, especially at high drug concentrations.

Hypertrophic cardiomyopathy (HCM) is a primary disease of the myocardium most commonly caused by mutations in sarcomeric genes. We aimed to perform a nationwide large-scale genetic analysis of a previously unreported, representative HCM cohort in Hungary. A total of 242 consecutive HCM index patients (127 men, 44 ± 11 years) were studied with next generation sequencing using a custom-designed gene-panel comprising 98 cardiomyopathy-related genes. A total of 90 patients (37%) carried pathogenic/likely pathogenic (P/LP) variants. The percentage of patients with P/LP variants in genes with definitive evidence for HCM association was 93%. Most of the patients with P/LP variants had mutations in MYBPC3 (55 pts, 61%) and in MYH7 (21 pts, 23%). Double P/LP variants were present in four patients (1.7%). P/LP variants in other genes could be detected in ≤3% of patients. Of the patients without P/LP variants, 46 patients (19%) carried a variant of unknown significance. Non-HCM P/LP variants were identified in six patients (2.5%), with two in RAF1 (p.Leu633Val, p.Ser257Leu) and one in DES (p.Arg406Trp), FHL1 (p.Glu96Ter), TTN (p.Lys23480fs), and in the mitochondrial genome (m.3243A>G). Frameshift, nonsense, and splice-variants made up 82% of all P/LP MYBPC3 variants. In all the other genes, missense mutations were the dominant form of variants. The MYBPC3 p.Gln1233Ter, the MYBPC3 p.Pro955ArgfsTer95, and the MYBPC3 p.Ser593ProfsTer11 variants were identified in 12, 7, and 13 patients, respectively. These three variants made up 36% of all patients with identified P/LP variants, raising the possibility of a possible founder effect for these mutations. Similar to other HCM populations, the MYBPC3 and the MYH7 genes seemed to be the most frequently affected genes in Hungarian HCM patients. The high prevalence of three MYBPC3 mutations raises the possibility of a founder effect in our HCM cohort.

To assess how ovarian-derived sex hormones (in particular progesterone) modify the effects of single acute stress on the mechanical and biochemical properties of left ventricular cardiomyocytes in the rat. Non-ovariectomized (control, n=8) and ovariectomized (OVX, n=8) female rats were kept under normal conditions or were exposed to stress (control-S, n=8 and OVX-S, n=8). Serum progesterone levels were measured using a chemiluminescent immunoassay. Left ventricular myocardial samples were used for isometric force measurements and protein analysis. Ca(2+)-dependent active force (Factive), Ca(2+)-independent passive force (Fpassive), and Ca(2+)-sensitivity of force production were determined in single, mechanically isolated, permeabilized cardiomyocytes. Stress- and ovariectomy-induced alterations in myofilament proteins (myosin-binding protein C [MyBP-C], troponin I [TnI], and titin) were analyzed by sodium dodecyl sulfate gel electrophoresis using protein and phosphoprotein stainings. Serum progesterone levels were significantly increased in stressed rats (control-S, 35.6±4.8 ng/mL and OVX-S, 21.9±4.0 ng/mL) compared to control (10±2.9 ng/mL) and OVX (2.8±0.5 ng/mL) groups. Factive was higher in the OVX groups (OVX, 25.9±3.4 kN/m(2) and OVX-S, 26.3±3.0 kN/m(2)) than in control groups (control, 16.4±1.2 kN/m(2) and control-S, 14.4±0.9 kN/m(2)). Regarding the potential molecular mechanisms, Factive correlated with MyBP-C phosphorylation, while myofilament Ca(2+)-sensitivity inversely correlated with serum progesterone levels when the mean values were plotted for all animal groups. Fpassive was unaffected by any treatment. Stress increases ovary-independent synthesis and release of progesterone, which may regulate Ca(2+)-sensitivity of force production in left ventricular cardiomyocytes. Stress and female hormones differently alter Ca(2+)-dependent cardiomyocyte contractile force production, which may have pathophysiological importance during stress conditions affecting postmenopausal women.

We set out to characterize the mechanical effects of myeloperoxidase (MPO) in isolated left-ventricular human cardiomyocytes. Oxidative myofilament protein modifications (sulfhydryl (SH)-group oxidation and carbonylation) induced by the peroxidase and chlorinating activities of MPO were additionally identified. The specificity of the MPO-evoked functional alterations was tested with an MPO inhibitor (MPO-I) and the antioxidant amino acid Met. The combined application of MPO and its substrate, hydrogen peroxide (H2O2), largely reduced the active force (Factive), increased the passive force (F-passive), and decreased the Ca2+ sensitivity of force production.(pCa(50)) in permeabilized cardiomyocytes. H2O2 alone had significantly smaller effects on Fact and Fpassive and did not alter pCa(50). The MPO-I blocked both the peroxidase and the chlorinating activities, whereas Met selectively inhibited the chlorinating activity of MPO. All of the MPO-induced functional effects could be prevented by the MPO-I and Met. Both H2O2 alone and MPO + H2O2 reduced the SH content of actin and increased the carbonylation of actin and myosin-binding protein C to the same extent. Neither the SH oxidation nor the tarbonylation of the giant sarcomeric protein titin was affected by these treatments. MPO activation induces a cardiomyocyte dysfunction by affecting Ca2+-regulated active and Ca2+-independent passive,force production and myofilament Ca2+ sensitivity, independent of protein SH oxidation and orbonylation. The MPO-induced deleterious functional alterations can be prevented by the MIND-I and Met. Inhibition of MPO may be a promising therapeutic target to limit myocardial contractile dysfunction during inflammation. (C) 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license.

Background: The 2023 ESC Heart Failure (HF) Guidelines recommend the rapid up-titration of guideline-directed medical therapy (GDMT) for all patients after HF hospitalisation. Real-world data on the implementation of a rapid up-titration programme (RTP) are scarce. Methods: We aimed to summarise the primary experiences of a six-week RTP in a multicentre observational study of five cardiology centres, evaluating the GDMT applied and the target doses (TDs) achieved during the RTP. The safety of RTP in relation to exceeding the “safety indicators” used in the STRONG-HF trial and any serious adverse events were observed. Changes in the left ventricular ejection fraction (LVEF) after RTP were evaluated. Results: Among the 90 consecutive patients (age: 56 [49–63] years, HFrEF: 96%, NT-proBNP at discharge: 1390 [735–2835] pg/mL; continuous variables are presented as median and interquartile ranges, while categorical variables are shown as absolute numbers and percentages, respectively), a remarkable proportion of patients received GDMT at hospital discharge; however, target doses were rarely achieved (RASi: 100%, TD RASi: 11%; βB: 97%, TD βB: 6%; MRA: 99%, TD MRA: 82%; SGLT2i: 98%, TD SGLT2i: 98%; triple therapy [TT: RASi + βB + MRA]: 96%, TD TT: 2%, quadruple therapy [QT: RASi + βB + MRA]: 94%, TD QT: 2%). After the six-week RTP, 100% of the total cohort (TC) were receiving RASi; 99–99–99% were receiving βB, MRA, and SGLT2i medications; and altogether, 98–98% were on TT and QT. In total, 78–78% of the patients received ≥50% of the TDs of TT and QT, while 51–51% of the TC were on TDs of TT and QT. During the RTP, no serious adverse events were observed. Between two and four months after the RTP, 51% of HFrEF patients evolved to the HFimpEF category. Conclusions: The present multicentre, observational study confirms that RTP is feasible and safe in real-world clinical practice, leading to a remarkably large proportion of patients receiving GDMT by the end of the six-week RTP, resulting in a significant increase in LVEF.