Myocardial adaptation and exercise performance in patients with pulmonary arterial hypertension assessed with patient-specific computer simulations

Computer simulations of the myocardial mechanics and hemodynamics of rest and exercise were performed in nine patients with pulmonary arterial hypertension and 10 control subjects, with the use of data from invasive catheterization and from cardiac magnetic resonance. This approach allowed a detailed analysis of myocardial adaptation to pulmonary arterial hypertension and showed how reduction in right ventricular inotropic reserve is the important limiting factor for an increase in cardiac output during exercise.

Possibilities of preclinical diagnosis of anthracycline cardiotoxicity using the technique of "speckle-tracking echocardiography"

In case of antitumour anthracyclines therapy of patients with non-Hodgkin lymphomas the possibility of using speckle-tracking echocardiography is being considered. It was found that patients with non-Hodgkin lymphomas have early violations of the left ventricular myocardium during the course of antitumor chemotherapy using anthracyclines. They are characterized by reducing of longitudinal deformation of the myocardium with a gradual spread from the apical to the basal segments of the left ventricle. A statistically significant reduction in global and segmental systolic deformation after the 4th course of chemotherapy (cumulative dose of doxorubicin 333.5 88.5 mg/m2) is the earliest marker of left ventricular mechanical dysfunction, appearing before the development of diastolic dysfunction and ejection fraction reduction of the left ventricular. Early violations of myocardial mechanics in the dynamics of the course of antitumour therapy with anthracyclines are identified in the apical area of the left ventricle, it can be connected with circulatory failure in this area. Violations of myocardial mechanics in the apical area of the left ventricle can be an erly predictor of ischemia of this area with possible progression to global contractile muscle dysfunction of the left ventricular. The global longitudinall deformation of the left ventricular myocardium in contrast to ejection fraction of the left ventricular is more sensitive to myocardial damages against the backdrop of chemotherapy using anthracyclines. So, it can be used as an early preclinical marker of myocardial damage, that takes echocardiography closer to the most advanced methods of myocardial visualization.

Modelling of fibre dispersion and its effects on cardiac mechanics from diastole to systole

Detailed fibre architecture plays a crucial role in myocardial mechanics both passively and actively. Strong interest has been attracted over decades in mathematical modelling of fibrous tissue (arterial wall, myocardium, etc.) by taking into account realistic fibre structures, i.e. from perfectly aligned one family of fibres, to two families of fibres, and to dispersed fibres described by probability distribution functions. It is widely accepted that the fibres, i.e. collage, cannot bear the load when compressed, thus it is necessary to exclude compressed fibres when computing the stress in fibrous tissue. In this study, we have focused on mathematical modelling of fibre dispersion in myocardial mechanics, and studied how different fibre dispersions affect cardiac pump function. The fibre dispersion in myocardium is characterized by a non-rotationally symmetric distribution using a $$\pi $$ π -periodic Von Mises distribution based on recent experimental studies. In order to exclude compressed fibres for passive response, we adopted the discrete fibre dispersion model for approximating a continuous fibre distribution with finite fibre bundles, and then the general structural tensor was employed for describing dispersed active tension. We first studied the numerical accuracy of the integration of fibre contributions using the discrete fibre dispersion approach, then compared different mechanical responses in a uniaxially stretched myocardial sample with varied fibre dispersions. We finally studied the cardiac pump functions from diastole to systole in two heart models, a rabbit bi-ventricle model and a human left ventricle model. Our results show that the discrete fibre model is preferred for excluding compressed fibres because of its high computational efficiency. Both the diastolic filling and the systolic contraction will be affected by dispersed fibres depending on the in-plane and out-of-plane dispersion degrees, especially in systolic contraction. The in-plane dispersion seems affecting myocardial mechanics more than the out-of-plane dispersion. Despite different effects in the rabbit and human models caused by the fibre dispersion, large differences in pump function exist when fibres are highly dispersed at in-plane and out-of-plane. Our results highlight the necessity of using dispersed fibre models when modelling myocardial mechanics, especially when fibres are largely dispersed under pathological conditions, such as fibrosis.

Amiodarone inhibits arrhythmias in hypertensive rats by improving myocardial biomechanical properties

The prevalence of arrhythmia in patients with hypertension has gradually attracted widespread attention. However, the relationship between hypertension and arrhythmia still lacks more attention. Herein, we explore the biomechanical mechanism of arrhythmia in hypertensive rats and the effect of amiodarone on biomechanical properties. We applied micro-mechanics and amiodarone to stimulate single ventricular myocytes to compare changes of mechanical parameters and the mechanism was investigated in biomechanics. Then we verified the expression changes of genes and long non-coding RNAs (lncRNAs) related to myocardial mechanics to explore the effect of amiodarone on biomechanical properties. The results found that the stiffness of ventricular myocytes and calcium ion levels in hypertensive rats were significantly increased and amiodarone could alleviate the intracellular calcium response and biomechanical stimulation. In addition, experiments showed spontaneously hypertensive rats were more likely to induce arrhythmia and preoperative amiodarone intervention significantly reduced the occurrence of arrhythmias. Meanwhile, high-throughput sequencing showed the genes and lncRNAs related to myocardial mechanics changed significantly in the spontaneously hypertensive rats that amiodarone was injected. These results strengthen the evidence that hypertension rats are prone to arrhythmia with abnormal myocardial biomechanical properties. Amiodarone effectively inhibit arrhythmia by improving the myocardial biomechanical properties and weakening the sensitivity of mechanical stretch stimulation.