Failure of myocardial inactivation: a clinical assessment in the hypertrophied heart

Insulin-like growth factor binding protein 2: a core biomarker of left ventricular dysfunction in dilated cardiomyopathy

BACKGROUND

RNA modifications, especially N6-methyladenosine, N1-methyladenosine and 5-methylcytosine, play an important role in the progression of cardiovascular disease. However, its regulatory function in dilated cardiomyopathy (DCM) remains to be undefined.

METHODS

In the study, key RNA modification regulators (RMRs) were screened by three machine learning models. Subsequently, a risk prediction model for DCM was developed and validated based on these important genes, and the diagnostic efficiency of these genes was assessed. Meanwhile, the relevance of these genes to clinical traits was explored. In both animal models and human subjects, the gene with the strongest connection was confirmed. The expression patterns of important genes were investigated using single-cell analysis.

RESULTS

A total of 4 key RMRs were identified. The risk prediction models were constructed basing on these genes which showed a good accuracy and sensitivity in both the training and test set. Correlation analysis showed that insulin-like growth factor binding protein 2 (IGFBP2) had the highest correlation with left ventricular ejection fraction (LVEF) (R = -0.49, P = 0.00039). Further validation expression level of IGFBP2 indicated that this gene was significantly upregulated in DCM animal models and patients, and correlation analysis validation showed a significant negative correlation between IGFBP2 and LVEF (R = -0.87; P = 6*10-5). Single-cell analysis revealed that this gene was mainly expressed in endothelial cells.

CONCLUSION

In conclusion, IGFBP2 is an important biomarker of left ventricular dysfunction in DCM. Future clinical applications could possibly use it as a possible therapeutic target.

Modification of human left ventricular relaxation by small-amplitude, phase-controlled mechanical vibration on the chest wall

BACKGROUND

Direct clinical manipulation to improve an impairment of left ventricular (LV) relaxation has not been reported. We investigated whether the LV relaxation rate in humans could be modulated by phase-controlled mechanical vibration applied to the patient's anterior chest wall and whether there are some quantitative differences in the responses of normal (N), hypertrophied (H), and failing (F) ventricle.

METHODS AND RESULTS

In 46 patients (N, 10; H, 18 [hypertrophic cardiomyopathy]; F, 18 [heart failure]), the vibrator was attached to the precordium and a 50-Hz, 2-mm sinusoidal mechanical vibration was applied, with the timing restricted from the onset of isovolumic relaxation to end-diastole during cardiac catheterization. Heart rate and peak LV pressure showed no difference with vibration. However, in all patients, precordial vibration caused an acceleration of the LV pressure fall. The magnitude of the induced reduction of the time constant of LV pressure decay (delta T) was larger (P < .01) in H and F than in N (4.6 +/- 2.3, 4.0 +/- 1.6, and 0.6 +/- 1.5 ms for H, F, and N, respectively). Delta T correlated strongly with the magnitude of impaired relaxation and the magnitude of transmitted vibration to the ventricle.

CONCLUSIONS

Phase-controlled, small-amplitude vibration on the chest wall can directly modulate LV relaxation rate, especially in those with hypertrophy or failing ventricle.

Endothelial control of vascular and myocardial function in heart failure

The effect of vascular endothelium, endocardium, and coronary endothelium on vascular tone and myocardial contraction-relaxation sequence in heart failure is discussed. Vascular endothelium affects underlying vascular smooth muscle through paracrine secretion of relaxing and constricting factors. In heart failure, systemic vasoconstriction results not only from neuroendocrine activation, but also from disturbed local endothelial control of vascular tone because of impaired endothelial-dependent vasodilation and because of increased plasma concentration of endothelin. Experimental evidence obtained in isolated cardiac muscle strips established the influence of endocardial endothelium on the duration of myocardial contraction and on the onset of myocardial relaxation. By analogy to vascular endothelium, both diffusible agents that abbreviate (endothelial-derived relaxation factor-like substance) and those that prolong (endocardin) myocardial contraction have been shown to be released from the endocardium. Similar agents are released from the coronary endothelium and, because of the close proximity of capillaries and myocytes, could exert a major effect on myocardial performance. Endothelial dysfunction and concomitant lack of release of myocardial relaxant factors could explain left ventricular relaxation abnormalities observed in the cardiac allograft or in arterial hypertension. Since endothelial-derived relaxation factor or nitric oxide mediates the coronary reactive hyperemic response, a negative inotropic action of nitric oxide could contribute to left ventricular failure when left ventricular wall stress is elevated, as occurs after myocardial infarction in the noninfarcted zone and during left ventricular volume or pressure overload in the absence of adequate hypertrophy.