Abstract

Background: Increased sympathetic drive resulting in decreased heart rate variability (HRV), has been linked to cardiovascular diseases such as heart failure and myocardial infarction (MI). Dynamic electrophysiological changes due to acute ischemia and chronic MI are known to be pro-arrhythmic. Objective: Evaluate the changes in autonomic tone resulting from substrate remodeling during the development of chronic MI in an in-vivo ovine model. Methods: ECG recordings were collected at baseline, post occlusion and 6 weeks post MI, in young adult sheep (n=16). Time domain, frequency domain and non-linear measures of HRV were evaluated from 10 minutes of ECG data at the 3 time points. RR interval, heart rate, SDRR (standard deviation of the RR intervals), RMSSD (root mean square of successive differences between normal heartbeats), QTc interval, pNN 50 , LF/HF ratio and SD1/SD2 ratio were calculated and compared between baseline, post acute coronary artery occlusion and after 6 weeks of chronic MI. 24-hour telemetry was also performed in an ambulatory animal for 6 weeks to monitor the progression of alterations in the T-wave morphology or duration, i.e. T-wave alternans, a known marker of ventricular tachyarrhythmias, with chronic MI. Results: Chronic MI led to significantly decreased RR interval (Fig.1A) and increased heart rate (Fig.1B), along with a significant prolongation of the QTc interval (Fig.1C). Significant rise was also observed in the SDRR (Fig1D) and LF/HF ratio (Fig1E) indicating a shift towards increased sympathetic tone and reduced parasympathetic drive. In addition to the autonomic changes, a significant rise in T-wave alternans burden (Fig1F) and localized action potential alternans inducibility was observed with progression of MI indicating increased arrhythmogenicity. Conclusion: Skewed autonomic balance is evident in chronic MI and may be closely linked to increased arrhythmogenicity.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.