Correlation between the high-frequency content of the QRS on murine surface electrocardiogram and the sympathetic nerves density in left ventricle after myocardial infarction: Experimental study

Abstract

Denervated post-infarct scar is arrhythmogenic. Our aim was to compare QRS frequency content in denervated and innervated left ventricular (LV) scar. In-vivo single lead ECG telemetry device was implanted in 17 heterozygous PTPσ (HET) and 7 lacking PTPσ (KO) transgenic mice. Myocardial infarction (MI) with reperfusion and sham surgery was performed. HET mice developed a denervated scar, whereas KO mice developed innervated scar. The power spectral density was used to assess the QRS frequency content. Denervated as compared to innervated post-MI scar was characterized by the higher relative contribution of 300–500Hz (14±1 vs. 9±1%; P=0.001) but reduced relative contribution of 200–300 Hz (86±1 vs. 91±1%; P=0.001). Norepinephrine concentration in peri-infarct zone correlated with both 1–200 Hz (r=0.75; p=0.03) and 200–500 Hz QRS power (r=0.73;P=0.04). Sympathetic fiber density within the infarct correlated with 200–300/200–500 Hz QRS power ratio (r=0.56;P=0.005). Intracellular sigma peptide injections in post-MI HET mice restored the QRS power.

Norepinephrine Turnover in the Left Ventricle of Subtotally Nephrectomized Rats

“…The tissue concentrations of norepinephrine were significantly lower in the left heart compartments of the SNX rats compared to the SHAM rats. Norepinephrine concentration in tissues may reflect the density of sympathetic innervation and dynamic balance between norepinephrine synthesis, release, uptake, and metabolism (Sedaghat et al 2017, Brodie et al 1966. Although the density of adrenergic nerves has not been quantified in this study, similar reduction in tissue levels of NPY and norepinephrine (localized in the sympathetic nerve endings, with substantially different synthesis, intraneuronal localization and metabolism), suggest that the density of sympathetic nerves might be compromised in hypertrophied left ventricles.…”

Enhanced ECG Record Quality: Integrated Artifact Suppression Using Soft Threshold on Wavelet Coefficients and Adaptive Filter Model

“…The frequencies of components participating in the ECG recording signal include muscle artifacts (5 -50 Hz), respiratory artifacts (0.12 -0.5 Hz), electrooculogram (EOG) artifacts (0.1 -20 Hz, corresponding to 8 -30 bpm), power line artifacts (50 or 60 Hz), and other electrical sources, typically greater than 10 Hz (e.g., muscle stimulators, strong magnetic fields, and pacemakers with impedance monitoring) [3,4]. The electrode-skin interface warrants particular attention as it constitutes the most significant source of interference, producing a DC component of approximately 200-300 mV [5,6]. Comparing the noise amplitude with the patient's heart electrical activity (typically between 0.1 and 2 mV) reveals that noise from this component is amplified through body movements or changes in the patient's position or respiration [7].…”