Heart rate turbulence in acute ischemic stroke

BACKGROUND

Heart rate turbulence (HRT), an ECG-based marker of autonomic cardiac regulation, has shown high prognostic value in patients with established cardiovascular diseases, while data in patients with acute ischemic stroke are scarce.

PATIENTS AND METHODS

The HRT parameters turbulence onset and turbulence slope were analyzed using Holter-ECG recordings from patients with acute ischemic stroke, consecutively enrolled in the prospective observational HEBRAS study. HRT was categorized as normal (category 0; both parameters normal), abnormal (category 1; one parameter abnormal), or severely abnormal (category 2; both parameters abnormal). Outcomes of interest were functional outcome according to modified Rankin Scale (mRS) score at 3 months, mortality at 1 year, newly detected atrial fibrillation (AF), and evidence of focal myocardial fibrosis on cardiovascular MRI.

RESULTS

HRT was assessed in 335 patients in sinus rhythm (median age 69 years, 37% female, median NIHSS score 2 on admission), including 262 (78%) with normal HRT, 47 (14%) with abnormal and 26 (8%) with severely abnormal HRT. Compared with normal HRT, severely abnormal HRT was associated with increased disability [higher mRS] at 3 months (adjusted odds ratio [aOR]: 2.9, 95% confidence interval [CI]: 1.3-6.6), new AF (aOR: 3.5, 95% CI: 1.1-10.6), MRI-detected myocardial fibrosis (aOR: 5.8, 95% CI: 1.3-25.9), but not with mortality at 1 year after stroke (aOR: 3.0, 95% CI: 0.7-13.9). Abnormal HRT was not associated with the analyzed outcomes.

CONCLUSIONS

Severely abnormal HRT was associated with increased disability and previously unknown cardiac comorbidities. The potential role of HRT in selecting patients for extended AF monitoring and cardiac imaging should be further investigated.

MCJ: A mitochondrial target for cardiac intervention in pulmonary hypertension

Pulmonary hypertension (PH) can affect both pulmonary arterial tree and cardiac function, often leading to right heart failure and death. Despite the urgency, the lack of understanding has limited the development of effective cardiac therapeutic strategies. Our research reveals that MCJ modulates mitochondrial response to chronic hypoxia. MCJ levels elevate under hypoxic conditions, as in lungs of patients affected by COPD, mice exposed to hypoxia, and myocardium from pigs subjected to right ventricular (RV) overload. The absence of MCJ preserves RV function, safeguarding against both cardiac and lung remodeling induced by chronic hypoxia. Cardiac-specific silencing is enough to protect against cardiac dysfunction despite the adverse pulmonary remodeling. Mechanistically, the absence of MCJ triggers a protective preconditioning state mediated by the ROS/mTOR/HIF-1α axis. As a result, it preserves RV systolic function following hypoxia exposure. These discoveries provide a potential avenue to alleviate chronic hypoxia-induced PH, highlighting MCJ as a promising target against this condition.

Targeting MuRF1 by small molecules in a HFpEF rat model improves myocardial diastolic function and skeletal muscle contractility

BACKGROUND

About half of heart failure (HF) patients, while having preserved left ventricular function, suffer from diastolic dysfunction (so-called HFpEF). No specific therapeutics are available for HFpEF in contrast to HF where reduced ejection fractions (HFrEF) can be treated pharmacologically. Myocardial titin filament stiffening, endothelial dysfunction, and skeletal muscle (SKM) myopathy are suspected to contribute to HFpEF genesis. We previously described small molecules interfering with MuRF1 target recognition thereby attenuating SKM myopathy and dysfunction in HFrEF animal models. The aim of the present study was to test the efficacy of one small molecule (MyoMed-205) in HFpEF and to describe molecular changes elicited by MyoMed-205.

METHODS

Twenty-week-old female obese ZSF1 rats received the MuRF1 inhibitor MyoMed-205 for 12 weeks; a comparison was made to age-matched untreated ZSF1-lean (healthy) and obese rats as controls. LV (left ventricle) function was assessed by echocardiography and by invasive haemodynamic measurements until week 32. At week 32, SKM and endothelial functions were measured and tissues collected for molecular analyses. Proteome-wide analysis followed by WBs and RT-PCR was applied to identify specific genes and affected molecular pathways. MuRF1 knockout mice (MuRF1-KO) SKM tissues were included to validate MuRF1-specificity.

RESULTS

By week 32, untreated obese rats had normal LV ejection fraction but augmented E/e' ratios and increased end diastolic pressure and myocardial fibrosis, all typical features of HFpEF. Furthermore, SKM myopathy (both atrophy and force loss) and endothelial dysfunction were detected. In contrast, MyoMed-205 treated rats had markedly improved diastolic function, less myocardial fibrosis, reduced SKM myopathy, and increased SKM function. SKM extracts from MyoMed-205 treated rats had reduced MuRF1 content and lowered total muscle protein ubiquitination. In addition, proteomic profiling identified eight proteins to respond specifically to MyoMed-205 treatment. Five out of these eight proteins are involved in mitochondrial metabolism, dynamics, or autophagy. Consistent with the mitochondria being a MyoMed-205 target, the synthesis of mitochondrial respiratory chain complexes I + II was increased in treated rats. MuRF1-KO SKM controls also had elevated mitochondrial complex I and II activities, also suggesting mitochondrial activity regulation by MuRF1.

CONCLUSIONS

MyoMed-205 improved myocardial diastolic function and prevented SKM atrophy/function in the ZSF1 animal model of HFpEF. Mechanistically, SKM benefited from an attenuated ubiquitin proteasome system and augmented synthesis/activity of proteins of the mitochondrial respiratory chain while the myocardium seemed to benefit from reduced titin modifications and fibrosis.