Effects of catecholamine stress on diastolic function and myocardial energetics in obesity

Mediator complex dependent regulation of cardiac development and disease

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality. The risk factors for CVD include environmental and genetic components. Human mutations in genes involved in most aspects of cardiovascular function have been identified, many of which are involved in transcriptional regulation. The Mediator complex serves as a pivotal transcriptional regulator that functions to integrate diverse cellular signals by multiple mechanisms including recruiting RNA polymerase II, chromatin modifying proteins and non-coding RNAs to promoters in a context dependent manner. This review discusses components of the Mediator complex and the contribution of the Mediator complex to normal and pathological cardiac development and function. Enhanced understanding of the role of this core transcriptional regulatory complex in the heart will help us gain further insights into CVD.

Molecular and cellular basis for diastolic dysfunction

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent and is frequently associated with metabolic risk factors. Patients with HFpEF have only a slightly lower mortality than patients with HF and reduced EF. The pathophysiology of HFpEF is currently incompletely understood, which precludes specific therapy. Both HF phenotypes demonstrate distinct cardiac remodeling processes at the macroscopic, microscopic, and ultrastructural levels. Increased diastolic left-ventricular (LV) stiffness and impaired LV relaxation are important features of HFpEF, which can be explained by changes in the extracellular matrix and the cardiomyocytes. In HFpEF, elevated intrinsic cardiomyocyte stiffness contributes to high diastolic LV stiffness. Posttranslational changes in the sarcomeric protein titin, affecting titin isoform expression and phosphorylation, contribute to elevated cardiomyocyte stiffness. Increased nitrosative/oxidative stress, impaired nitric oxide bioavailability, and down-regulation of myocardial cyclic guanosine monophosphate and protein kinase G signaling could trigger posttranslational modifications of titin, thereby augmenting cardiomyocyte and LV diastolic stiffness.

Cardiac structure and function are altered in adults with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is associated with a twofold greater risk of developing cardiovascular disease. Despite this, little is known about the effect of NAFLD upon cardiac function, limiting our ability to identify therapeutic strategies. This study aimed to address this by defining the effect of NAFLD on cardiac function, structure, and metabolism.

METHODS

Nineteen adults with NAFLD were age-, sex-, and BMI-matched to healthy controls without liver or metabolic disease. Cardiac structure and function were assessed using high-resolution cardiac MRI and tagging at 3.0 T. High-energy phosphate metabolism was assessed using (31)P-magnetic resonance spectroscopy to measure the PCr/ATP ratio.

RESULTS

Adults with NAFLD had significantly thicker left ventricular walls at systole (14 ± 3 vs. 12 ± 2 mm; p <0.01) and diastole (8 ± 1 vs. 7 ± 1 mm; p <0.01) than those without fatty liver and showed decreased longitudinal shortening (14 ± 3 vs. 17 ± 3%; p <0.01). The eccentricity ratio was significantly higher in the NAFLD group (1.1 ± 0.2 vs. 0.9 ± 0.2 g/ml; p <0.01) indicating concentric remodelling. Peak whole wall strain was higher in the NAFLD group (19 ± 2 vs. 17 ± 3%; p <0.01), as was peak endocardial strain (28 ± 4 vs. 22 ± 5%; p <0.01). Cardiac metabolism, measured by PCr/ATP ratio, was not altered in NAFLD (1.8 ± 0.3 vs. 1.9 ± 0.3; p=0.36).

CONCLUSIONS

Significant changes in cardiac structure and function are evident in adults with NAFLD in the apparent absence of metabolic changes or overt cardiac disease. Clinicians should continue to explore therapies to improve cardiac function as a means to modify the excess risk of cardiovascular disease associated with NAFLD.

Association between inotrope treatment and 90-day mortality in patients with septic shock

BACKGROUND

Administration of inotropes in septic patients with low cardiac output or low central/mixed venous saturation is recommended in current guidelines. However, the impact of inotrope use on the outcome of these patients is controversial. We aimed to analyse the association of inotrope treatment with 90-day mortality.

METHODS

Data from 420 consecutive patients with septic shock were retrospectively collected from the intensive care unit (ICU) data management system. Factors associated with inotrope treatment were assessed. The association of 90-day mortality with inotrope treatment was first analysed using logistic regression analysis, and second including propensity score based on observed variables for selection to inotrope treatment. A subgroup analysis was performed for the 252 patients with pulmonary artery catheter.

RESULTS

One hundred eighty-six (44.3%) patients received inotrope treatment during the first 24 h in ICU. Of those, 168 (90.3%) received dobutamine, 29 (15.6%) levosimendan, and 23 (12.4%) epinephrine. Blood lactate (P < 0.001), central venous pressure, (P < 0.001), and norepinephrine dose (P = 0.03) were independently associated with inotrope treatment. Patients with inotrope treatment had a higher 90-day mortality (42.5% vs. 23.9%, P < 0.001). Age (P < 0.001), Acute Physiology and Chronic Health Evaluation II score (P < 0.001), and inotrope treatment (P = 0.003) were independently associated with 90-day mortality also after adjustment with propensity score.

CONCLUSION

The use of inotrope treatment in septic shock was associated with increased 90-day mortality without and after adjustment with propensity to receive inotrope. To differentiate between non-observed biases of severity of septic shock and an unfavourable effect of inotropes, prospective studies are needed.