RR Variability in Acute Coronary Syndromes

American Journal of Cardiology, 1994

The relation between both time and frequency domain analyses of RR variability and mortality was examined in a series of 226 consecutive patients with acute myocardial infarction admitted to 3 district hospitals in London. All patients underwent 2440~ Holter monitoring early after infarction (mean 83 hours, range 48 to lSO), and time and frequency domain analyses of RR variability were performed using commercially available software. During an &month follow-up period (range 3 to 12 months), there were 19 cardiac deaths (8.4%). Time domain analysis confirmed reduced RR variability (SDRR, SDANN, SD) among nonsurvivors compared with survivors. However, there was no difference between the groups when the percentage of absolute diiep ences between successive RR intervals ~50 ms (pNN50) and the root-meausquare of successive differences (RMSSD)-vagai measures of RR variabllii-were analyzed. Frequency domain analysis demonstrated a signiiicant difference between those who died and the survivors when the low-frequency component-modulated by both vagai and sympathetic mechanisms-was analyzed; however, this was less marked when the hiiuency component~oduiated by vagal activity-was analyzed. None of these measures of RR variability was related to infarct site or left ventricular ejection traction. In conciusion, the data confirm the association between low RR variability and mortality after acute my ocardial hrfarction. However, the mechanism does not appear to relate exclusively to decreased parasympathetic tone. 7he data suggest that the increased risk of early mortality associated wlth reduced RR variability reflects an imbalance in sympathovagai function that is unrelated to left ventricular function.

Circulation, 1992

Background. After acute myocardial infarction (AMI), several abnormalities of the autonomic control to the heart have been described. Heart rate (HR) variability has been used to explore the neural control to the heart. A low HR variability count measured 7-13 days after AMI is significantly related to a poor outcome. Little information is available on HR variability early after AMI and its relation to clinical and hemodynamic data.

The American Journal of Cardiology, 1987

A hgh degree of heart rate (HR) variability is found in compensated hearts with good function, whereas HR variability can be decreased with severe coronary artery disease, congestive heart failure, aging and diabetic neuropathy. To test the hypothesis that HR variability is a predictor of long-term survival after acute myocardial infarction (AMI), the Holter tapes of 808 patients who survived AMI were analyzed. Heart rate variability was defined as the standard deviation of all normal RR intervals in a 24hour continuous electrocardiogram recording made 11 f 3 days after AMI. In all patients demographic, clinical and laboratory variables were measured at baseline. Mean follow-up time was 31 months. of all Holter variables measured, HR variability had the strongest univariate correlation with mortality. The relative risk of mortality was 5.3 times higher in the group with HR variability of less than 50 ms than the group with HR variability of more than 100 ms. HR variability remained a significant predictor of mortality after adjusting for clinical, demographic, other Holter features and ejection fraction. A hypothesis to explain this flndlng is that decreased HR variability correlates with increased sympathetic or decreased vagal tone, which may predispose to ventricular fibrillation. (Am J Cardiol 1987;59:258-282) S everal studies have documented the prognostic information, primarily ventricular arrhythmias, provid-

Medical & Biological Engineering & Computing, 1992

American Journal of Cardiology, 1996

The occurrence of an autonomic disturbance early in acute myocardial infarction (AMI) has been reported: signs of sympathetic activation were mainly observed in relation to an anterior localization, whereas signs of vagal overactivity were more frequent in inferior wall AMI. Information is limited in relation to the persistence of these alterations during the early hours of AMI. We studied 33 patients with an AMI within 188 2 16 minutes from the onset of symptoms and 1 week after hospital admission. From a 20-minute Holter recording, we computed with autoregressive methodology, time and frequency domain indexes of heart rate variability.

Ann. Pak. Inst. Med. Sci, 2011

Objective: To compare heart rate variability in patients of acute myocardial with that of healthy individuals and to establish correlation between time and frequency domain indices of heart rate variability in patients with AMI and healthy individuals. Study Design: Non-interventional descriptive study. Place and Duration: Armed Forces Institute of Cardiology (AFIC)/National Institute of Heart Diseases(NIHD), Rawalpindi over six months. Materials and Methods: We studied 45 patients of AMI and same number of age and sex matched normal healthy volunteers. Their 24-hour holter recordings within 48h of acute myocardial infarction were analyzed for HRV in time and frequency domains. Results: The time domain indices; SDNN (healthy volunteers=133±35ms vs. AMI=75±29ms), SDANN (healthy volunteers=118±34ms vs. AMI=65±28ms), SDNNi (healthy volunteers=59±18ms vs. AMI=35±14ms), rMSSD (healthy volunteers=40±17ms vs. AMI=28±13ms) and pNN50 (healthy volunteers=13±9% vs. AMI=6±11%) were significantly decreased (P less than 0.001) in patients with AMI when compared with healthy volunteers. Comparison of frequency domain indices; TP (healthy volunteers=3525±2671ms 2 vs. AMI=1296±1178ms 2 ), VLF (healthy volunteers=2485±2201ms 2 vs. AMI=902±928ms 2 ), LF (healthy volunteers=695±391ms 2 vs. AMI=246±251ms 2 ), HF (healthy volunteers=315±259ms 2 vs. AMI=100±96ms 2 ) between healthy volunteers and patients after myocardial infarction revealed a significant decline (P less than 0.001) in the parameters of patients. SDNNi was significantly correlated with power and VLF in normal healthy volunteers (power; r=0.92, VLF; r= 0.89) as well as in patients with AMI (power; r=0.85, VLF; r= 0.78). Conclusion: Time domain and frequency domain indices of HRV are significantly affected by early phase of AMI. This indicates HRV assessment after AMI may be useful in noninvasive risk stratification. It is suggested that mortality should be verified after followup studies of AMI. Time and frequency domain indices are significantly correlated.

Journal of Cardiovascular Electrophysiology, 1995

Since the MPIP report in 1987' showing a highly significant relationship between decreased heart rate variability and mortality post infarction, there has been increased interest in measuring heart rate variability for its potential in risk stratifying patients post infarction, in its potential for revealing the physiologic relationships between autonomic tone and malignant ventricular arrhythmias, and for its therapeutic implications. The MPIP study showed in over 800 survivors of myocardial infarction (MI) that those patients with SDNN < 50 msec, defined as the standard deviation of all normal cycles recorded during 24 hours of ambulatory monitoring, had a 5.3 relative risk of dying within 31 months compared to those with SDNN > 100 msec. Approximately 15% of the population with low heart rate variability (HRV) had 34% of the deaths in the total population, and a mortality of 34.4%. Thus, using SDNN < 50 msec alone, a test with sensitivity and positive predictive accuracy > 0.33 was identified. Subsequent studies of HRV in post infarct patients have further amplified these results and sought answers to the following questions: What methods and techniques of measuring HRV are most useful in the post infarct pafient? How can the risk stratificadon of patients post infarct be improved using HRV measurements? And, what are the mechanisms of the increased mortality seen in post infarct patients with low HRV?

Pacing and Clinical Electrophysiology, 1997

HOHNLOSER, S.H., ET AL.: Heart Rate Variability Used as an Arrhythmia Risk Stratifier After Myocardial Infarction. Heart rate variability (HRV) is considered to represent a noninvasive tool to assess cardiac autonomic tone at the level of the sinus node. It has been shown to have predictive power for risk assessment in patients surviving acute myocardial infarction. For this purpose, HRV should be assessed from 24-hour Holter recordings obtained 7-10 days following the infarction. Although there is some recovery of HRV during the first 3 months after infarction, HRV remains reduced in postinfarction patients compared to values obtained in healthy individuals. Compared to assessment of left ventricular function as a risk marker, HRV is superior with respect to prediction of arrhythmic events and sudden death whereas both parameters yield comparative power for prediction of total cardiac mortality. Since the predictive power of HRV analysis alone is relatively low, the combined use of HRV measurenients together with traditional risk markers (such as ventricular ectopic beats, signal-averaged ECG, or left ventricular function) results in improved risk prediction with positive predictive accuracy in the range of 30%-50%.

The American Journal of Cardiology, 1998

A low heart rate variability (HRV) has been shown to be a powerful predictor of cardiac events in patients surviving an acute myocardial infarction (MI), but it is not clear yet which among the HRV parameters has the best predictive value. Time domain and frequency domain HRV was assessed on 24-hour predischarge Holter recording of 239 patients with a recent MI. Patients were followed up for 6 to 54 months (median 28), during which 26 deaths (11%) occurred, 19 of which were cardiac in origin and 12 were sudden. Most HRVs did not show any difference between patients with or without mortality end points, but the average low-frequency and low-frequency/high-frequency ratio was lower in patients with events. However, when dichotomized according to cut points that maximized the risk of sudden death, several HRVs were significantly predictive of clinical end points. Overall, the mean of the standard deviations of all RR intervals for all 5-minute segments and the standard deviation of the mean RR intervals for all 5-minute segments were the time domain variables most significantly associated with mortality end points, whereas very low frequency was the most predictive frequency domain variable. Compared with the best time domain variables, very low frequency showed a better sensitivity (0.27 to 0.42 vs 0.19 to 0.33) for end points with only a small loss in specificity (0.92 vs 0.96). On multivariate Cox proportional analysis, a left ventricular ejection fraction <40% and a number of ventricular premature beats >10/hour were the most powerful independent predictors for all end points, whereas no HRV was independently associated with the events. A low frequency/high frequency ratio <1.05 only had a borderline association with sudden death (RR ‫؍‬ 2.86, p ‫؍‬ 0.076). Our data show a strong association between HRV and mortality in patients surviving a recent MI, with a slight better sensitivity of frequency domain analysis. In our study, however, HRV did not add independent prognostic information to more classic prognostic variables (e.g., left ventricular function and ventricular arrhythmias). ᮊ1998

International Journal of Cardiology, 2007

The need to refine the identification of patients who might benefit from implantation of an implantable cardioverter defibrillator has been risen by the results of many clinical trials on ICD therapy. Traditional parameters such as left ventricular ejection fraction and the presence of non-sustained ventricular tachycardia were not strong enough to achieve this goal with reasonable cost-effectiveness. Heart rate variability (HRV) is one of the most popular parameters used to assess the autonomic tone. HRV has been reported as a strong predictor of cardiovascular mortality. Currently, three different categories of methods in HRV analysis are being used; the time domain, frequency domain, and non-linear dynamic analysis. Both time domain and frequency domain analyses of HRV have been investigated extensively regarding their use as a prognostic marker for cardiovascular mortality. The non-linear dynamic analysis is the latest tool that has shown to have an even higher predictive value than any of the traditional parameters. However, standardized and supporting evidence on this new technique is still lacking. In this article, the current role of HRV in the prediction of cardiovascular mortality in myocardial infarction and heart failure patients has been reviewed.