Changes in Heart Rate Variability after Coronary Artery Bypass Grafting and Clinical Importance of These Findings.

Nenad Lakusic,Darija Mahovic,Dusko Cerovec,Peter Kruzliak,Jasna Cerkez Habek,Miroslav Novak

doi:10.1155/2015/680515

Abstract

Heart rate variability is a physiological feature indicating the influence of the autonomic nervous system on the heart rate. Association of the reduced heart rate variability due to myocardial infarction and the increased postinfarction mortality was first described more than thirty years ago. Many studies have unequivocally demonstrated that coronary artery bypass grafting surgery generally leads to significant reduction in heart rate variability, which is even more pronounced than after myocardial infarction. Pathophysiologically, however, the mechanisms of heart rate variability reduction associated with acute myocardial infarction and coronary artery bypass grafting are different. Generally, heart rate variability gradually recovers to the preoperative values within six months of the procedure. Unlike the reduced heart rate variability in patients having sustained myocardial infarction, a finding of reduced heart rate variability after coronary artery bypass surgery is not considered relevant in predicting mortality. Current knowledge about changes in heart rate variability in coronary patients and clinical relevance of such a finding in patients undergoing coronary artery bypass grafting are presented.

Highlights

Sinus rate is neither constant nor uniform but is changing all the time under the influence of the sympathetic and parasympathetic systems
The mechanisms of heart rate variability reduction associated with acute myocardial infarction and coronary artery bypass grafting are different
The following measures are used in frequency domain: Total Power—variance of all RR intervals obtained by spectral analysis that corresponds to the standard deviation of all normal RR intervals (SDNN) variable in time domain; components of the ultralow frequency spectrum (ULF; 0.0–0.0033 Hz); very low frequency spectrum (VLF; 0.0033–0.04 Hz); low frequency spectrum (LF; 0.04–0.15 Hz); high frequency spectrum (HF; 0.15–0.4 Hz); and their ratio (LF/HF) (Figure 1), [3]

Summary

Introduction

Sinus rate is neither constant nor uniform but is changing all the time under the influence of the sympathetic and parasympathetic systems. The impact of the autonomic nervous system on the occurrence and mortality of malignant arrhythmias was demonstrated on an experimental animal model as early as some thirty years ago. Decreased parasympathetic tone or increased sympathetic tone predisposes patients to the occurrence of malignant arrhythmias, even ventricular fibrillation. Vice versa, increased parasympathetic tone or decreased sympathetic tone reduces myocardial vulnerability and the occurrence of ventricular rhythm disturbances [1]. Such unambiguous experimental evidence has encouraged researchers to search for and develop a method to quantitatively measure autonomic nervous activity. Analysis of heart rate variability (HRV) is one of such indicators of the autonomic nervous system activity

Heart Rate Variability

Heart Rate Variability and Myocardial Infarction

Findings

Heart Rate Variability and Coronary Artery Bypass Grafting