Time-domain Heart Rate Variability Parameters Research Articles

Heart rate turbulence and variability in patients with ventricular arrhythmias

Background:To evaluate the changes in autonomic neural control mechanisms before malignant ventricular arrhythmias, we measured heart rate variability (HRV) and heart rate turbulence (HRT) in patients with ventricular tachycardia or fibrillation (Group I; n=6), non sustained ventricular tachycardia (Group II; n=32), frequent premature ventricular beats (Group III; n=26) and with ICD implantation (Group IV; n=11).Methods:Time domain parameters of HRV and turbulence onset (TO) and slope (TS) were calculated on 24 hour Holter recordings. Normal values were: SDNN > 70 msec for HRV, TO <0% and TS >2.5 msec/RR-I for HRT.Results:Whereas SDNN was within normal range and similar in all study groups, HRT parameters were significantly different in patients who experienced VT/VF during Holter recording. Abnormal TO and/or TS were present in 100% of Group I patients and only in about 50% of Group II and IV. On the contrary, normal HRT parameters were present in 40–70% of Group II, III and IV patients and none of Group I.Conclusions:These data suggest that HRT analysis is more suitable than HRV to detect those transient alterations in autonomic control mechanisms that are likely to play a major trigger role in the genesis of malignant cardiac arrhythmias.

Modulation of Cardiac Autonomic Nervous Activity Early after Cardioversion of Atrial Fibrillation by Biphasic Waveform

Imbalance of cardiac autonomic nervous modulation might prominently contribute to early relapses of atrial fibrillation (AF) after cardioversion (CV). The biphasic (Bi) waveform is more effective than the monophasic (Mo) waveform in CV of AF. Whether these waveforms have different effects on autonomic modulation early after CV is unknown. We investigated 171 consecutive patients after successful electrical CV (mean age 65.4 years, 82% male, 80% structural heart disease). Bi waveform was used in 89, Mo waveform in 82. Heart rate variability (HRV) was analyzed from 24-hour Holter recordings, started directly after CV. Mean delivered total energy was significantly lower in the Bi group (Bi 223 +/- 163 W, Mo 355 +/- 211 W, P < 0.001). Mean RR interval decreased within 5 hours after CV and increased again within the remaining hours, without significant differences between Bi and Mo groups. Time courses of time domain parameters of HRV revealed Bi profiles with the lowest levels 6 hours after CV in both groups. However, the hourly values of HRV were significantly higher in the Bi subgroup. Our study indicates that waveform and total delivered energy significantly influence autonomic modulation of the sinus node in the early phase after CV of AF. In contrast to Bi CV, Mo CV is characterized by a significant decrease of cardiac vagal modulation, which may have an arrhythmic effect by increasing the degree of early electrical stunning after CV of AF.

Heart rate variability in neurally mediated reflex syncope

Objective — The aim of this study was to investigate the heart rate variability (HRV) parameters in patients with neurally mediated reflex syncope.Methods — Thirty-three patients (10men, age range 16-50years) who were scheduled to undergo head-upright tilt test (HUTT) with a typical history of vasovagal syncope (VVS) underwent 24-hour Holter monitoring in an attempt to study HRV parameters. Sixteen individuals without syncope and similar baseline characteristics made up the control group.Results — Seventeen of the 33syncopal patients showed HUTT positivity. All the time domain HRV parameters except the mean RR interval were higher in the HUTT (+) syncopal patients than in the negative responders. Although not statistically significant, the positive responders had higher NN50, pNN50, RMSSD and SDNNi values than the control group. HUTT (-) VVS patients had lower SDNN and SDANN values when compared with the control group.The other HRV parameters did not differ significantly between the HUTT (-) patients and the control group.Conclusion — Increased parasympathetic tonus as reflected by significantly higher HRV parameters is associated with a greater frequency of HUTT positivity in patients with syncope and no organic heart disease.

Effects of Different Size Particulate Matters on Heart Rate Variability in the Elderly People

P-399 Introduction: Environmental epidemiologic studies have shown that the elderly people are susceptible for particulate air pollution. The decreases in heart rate variability (HRV) are important indices of health effect caused by particulate matter (PM). The objective of this study was to investigate the short-term effects of submicron particle (PM1), PM1–2.5, and coarse particle (PM2.5–10) on HRV parameters in the elderly. Method: The study population consisted of 15 non-smoking volunteers aged from 53 to 75 yrs, all of whom resided in the metropolitan Taipei area, Taiwan. Personal PM exposures were measured using a direct-reading portable dust monitor (GRIMM Model 1.108, Germany) in 1-minute interval, while each subject’s 24-hour electrocardiographics were recorded by a PacerCorder® holter recorder (DELMAR™ Medical LLC., model 461A, USA) in 5-minute interval. For each subject, health status and environmental factors were assessed by questionnaire and activity diary. The mass concentrations of PM1, PM1–2.5, and PM2.5–10 were measured and recorded as 1-hour, 2-hour, 3-hour, 4-hour, 5-hour, 6-hour, 7-hour, and 8-hour moving averages. Linear mixed-effects models were applied to estimate the effects of PM on time domain indices and frequency domain indices of HRV, using interquartile range (IQR) increase in PM concentrations. Time domain HRV parameters included the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD). Frequency domain HRV parameters included low frequency (LF) and high frequency (HF). Results: After adjusting for gender, age, body mass index, sleeping hours, β-block medicine, disease type, temperature, and relative humidity, the 3-hour moving averages of PM1 concentrations were found to have the strongest impact on HRV parameters. The strongest effects of PM1–2.5 on the decreases in SDNN, LF, and HF were shown for the 3-hour moving average, while the effect on r-MSSD decrease was the strongest for the 4-hour moving average. The largest decreases in SDNN, LF, r-MSSD, and HF for the effects of PM2.5–10 were found for 8 hours, 8 hours, 7 hours, and 4 hours moving averages, respectively. In addition, the impact of 3-hour PM moving average on the HRV decrease displayed the order of PM2.5–10 > PM1 > PM1–2.5, while only PM2.5–10 showed a significant impact on the HRV decrease after 5 hours. Conclusions: Results of our study indicated that PM may have both of the short-term effects and the delayed effects on HRV reduction in the elderly, with stronger delayed effect found for coarse particles in comparison with particles of other size ranges. Compared to the IQR concentrations of PM1 and PM1–2.5, coarse particles demonstrated a larger impact on the decrease in HRV for the elderly people.

Heart rate turbulence and heart rate variability in patients with mitral valve prolapse

Heart rate turbulence (HRT) and heart rate variability (HRV) have been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. However, the predictive values of HRV alone is modest and information on HRV in patients with mitral valve prolapse (MVP) has so far been conflicting. In addition, no studies have previously evaluated HRT in patients with MVP. To define better the effects of MVP on cardiac autonomic function, we assessed HRT and time-domain parameters of HRV in patients with MVP. Fifty patients with MVP and 70 controls without MVP were investigated. The diagnosis of MVP was confirmed by cross-sectional echocardiography in the parasternal long-axis view and apical 4-chamber view. The HRV and turbulence analysis were assessed from a 24-hour Holter recording. When HRT parameters were compared, the values of the HRT onset and slope were significantly lower in MVP patients than in the controls group (-0.109+/-0.207 vs. -0.289+/-0.170%, P=0.001 and 8.6+/-7.2 vs. 11.5+/-7.4 ms/RRI, P=0.043, respectively) and the number of patients who had abnormal HRT onset was significantly higher in the MVP group than in controls (15 vs. 8, P=0.011). In addition, HRV parameters were not statistically different between the two groups. Although we found that the decrease in HRV parameters was not significantly different between MVP patients and controls, HRT variables (especially HRT onset) were significantly lower in MVP patients. Therefore, in our opinion, HRT is an attractive, easily applicable, and better way of non-invasive risk prediction compared with another non-invasive risk predictor, HRV.

Orthostatic heart rate variability analysis in idiopathic Parkinson's disease

We evaluated time and spectral analyses of 24-h heart rate variability (HRV) and the heart rate responses to passive tilt in patients with idiopathic Parkinson's disease (IPD) in order to investigate cardiovascular autonomic functions. Twenty-three subjects with IPD without autonomic symptoms and 15 age-matched healthy controls were enrolled. Frequency- and time-domain HRV parameters were studied during resting and passive head-up tilt (HUT) test. All time-domain parameters were found to be low in patients with IPD. In patients with IPD, both low frequency (LF) and high frequency (HF) decreased during HUT period and no significant change in LF to HF ratio was noted. Both time- and frequency-domain HRV indices showed no correlation with age, disease severity and duration, and with l-dopa medication. The results indicate that impairment of autonomic nervous system function in IPD without autonomic symptoms is frequent, and does not show clear association with clinical stage and the age of the patients.

Heart rate variability during extracorporeal membrane oxygenation and recovery in severe neonatal disease

Background Heart rate variability (HRV) reveals information on the functional state of the autonomic nervous system (ANS) in neonates. During severe illness, heart rate variability is impaired. Aim This study was initiated to measure the changes in HRV in neonates during extracorporeal membrane oxygenation (ECMO) and recovery from severe respiratory and circulatory failure. Moreover, we compared our data with HRV data of healthy newborns and we investigated the differences in HRV parameters between ECMO-survivors and non-survivors. Study design This study is of an observational character. We performed short-term recordings of heart rate variability in 14 neonates during ECMO and recovery. We computed time- and frequency-domain HRV parameters. Results ECMO significantly affects time-domain HRV parameters. Severe neonatal illness causes a significant reduction of all calculated HRV parameters; clinical recovery is accompanied by an increase of HRV. In comparison with normative data of healthy newborns, however, HRV remains impaired. The ECMO–development ratio separated the non-survivors from the survivors during ECMO therapy. Conclusions During severe neonatal illness, HRV is impaired. It remains to be clarified whether the impairment of HRV during severe illness can predict the neurological outcome. The ability of the E/D ratio as an HRV parameter to serve as a predictive tool has to be corroborated in larger group of patients.

Comparison of the Short-term Effects of Salmeterol and Formoterol on Heart Rate Variability in Adult Asthmatic Patients

We investigated the effects of beta2-adrenergic agonists salmeterol and formoterol on heart rate variability (HRV) in adult asthmatic patients using time-domain measures of HRV. Thirty-nine adult patients with asthma were studied. All patients showed a mild-to-moderate decrease in baseline FEV1. Any diseases that might have influenced the autonomic function were excluded. All patients underwent a complete physical examination and medical history that revealed no cardiovascular disease or medication. The beta2-adrenergic inhaled agonists salmeterol, 50 microg, and formoterol, 12 microg, were used in the study. HRV analysis was performed for each 5-min segment: 5 min and 10 min before inhalation of the study drug, and 5, 10, 15, 20, 25, and 30 min after inhalation. Time-domain parameters of HRV were calculated: (1) the SD all normal-to-normal intervals; (2) the SD of the mean of all normal-to-normal intervals in all 5-min segments of the entire recording; (3) the root mean square of differences between adjacent normal-to-normal intervals; (4) the mean of the SD of all normal-to-normal intervals in all the 5-min intervals; and (5) the SD of the SD of all normal-to-normal intervals in all the 5-min intervals. Baseline HRV parameters were not significantly different between formoterol and salmeterol groups. There were no significant differences in HRV parameters after formoterol and salmeterol inhalation. The HRV parameters in each 5-min segment in the formoterol group were not statistically significant different when compared to the same segment in the salmeterol group. Salmeterol and formoterol have no short-term adverse effects on HRV.

Sympatho-vagal control of heart rate variability in patients treated with suppressive doses of L-thyroxine for thyroid cancer

This study aimed to analyze the autonomic control of heart rate variability (HRV) in subjects receiving chronic l-thyroxine (l-T4) treatment after total thyroidectomy and (131)I therapy for differentiated thyroid carcinoma. Blood pressure (BP) and sympatho-vagal activity (evaluated by power spectral analysis (PSA) of time-domain parameters of HRV) were studied in clinostatism and after orthostatism in 24 healthy controls, and in 12 patients taking l-T4 (125-200 mug/day) to maintain serum TSH levels at <0.01 muIU/ml. The study of HRV by PSA is a non-invasive method of analyzing sympatho-vagal control of HRV by quantifying high-frequency (HF) (0.15-0.4 Hz) and low-frequency (LF) (0.04-0.15 Hz) powers. Patients on L-T4 treatment had undetectable TSH levels, serum free T4 (fT4) above the normal range or at the upper limit in one case, and normal free tri-iodothyronine (fT3) levels. Heart rate and R-R intervals were not different in the two groups, both in clinostatism and in ortostatism. Systolic and mean BP were higher in patients than in controls and were inversely correlated with actual serum fT4 levels. During clinostatism, thyroid patients showed significantly lower LF power (P = 0.035), LF/(LF + HF) (P = 0.008) and LF/HF (P = 0.01) than controls. When patients moved from lying to standing, there was a significantly different decrease in orthostatic LF power (P = 0.001), LF/(LF + HF) (P = 0.044) and LF/HF (P = 0.047) versus controls. Changes in autonomic control of HRV, characterized by decreased sympathetic activity and impaired sympatho-vagal balance with preserved vagal tone, are detectable in patients with hyperthyroxinemia due to suppressive l-T4 therapy and increased systolic and mean, but not diastolic, BP.

Effects of amlodipine and lacidipine on heart rate variability in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction

Objective To estimate the influence of therapy with amlodipine (A) or lacidipine (L) on heart rate variability (HRV) time and frequency domain parameters in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction. Methods After a 1-week washout period, the patients were randomized to receive amlodipine 10 mg (30 patients) or lacidipine 6 mg (30 patients) once-daily for 4 weeks. HRV parameters were determined over a period of 24 h, echocardiography and exercise test were performed before and after treatment. Results All HRV time domain parameters after applying amlodipine did not change significantly. A reliable decrease only of the root mean square of differences between adjacent normal-to-normal intervals (RMSSD)—32.9±13 vs. 27.5±9—was noticed after treatment with lacidipine. In the lacidipine group, the change of RMSSD negatively correlated with the extent of ST segment depression during exercise testing ( R=−0.43; P<0.05). Both drugs reduced total power (A, 2234±1270 vs. 1813±889; L, 2205±1151 vs. 1825±896; P<0.01), very low (A, 1451±733 vs. 1143±534; L, 1413±759 vs. 1213±616; P<0.05), and low frequency power (A, 610±459 vs. 447±321; L, 569±323 vs. 442±241; P<0.01). After amlodipine, high frequency power remained unchanged, whereas low–high frequency ratio decreased (4.54±1.72 vs. 3.77±1.73; P<0.05). After lacidipine, high frequency power decreased (178.8±153.2 vs. 132.1±79.3; P<0.05), whereas the ratio of low frequency to high frequency did not change. Conclusions Amlodipine and lacidipine reduce the influence of humoral control and sympathetic autonomic nervous system activity. The autonomic balance becomes shifted toward the increased vagal activity only by amlodipine.

The relationship between plasma endothelin-1, nitric oxide levels, and heart rate variability in patients with coronary slow flow.

Coronary slow flow (CSF) is characterized by delayed opacification of coronary arteries in the absence of epicardial occlusive disease. In this study, we aimed to determine endothelin-1 (ET-1), nitric oxide (NOx) levels and time domain heart rate variability (HRV) parameters in patients with CSF and relationship among these parameters. Thirty-three patients with CSF detected in the coronary angiography (17 females; mean age 55 +/- 7) and 19 patients with normal coronary flow (10 females; mean age 54 +/- 11) as a control group were enrolled in the study. Patients were divided into two groups according to exercise testing as if positive (group A, n = 8) or negative (group B, n = 25). Plasma ET-1 levels were higher in the group A patients (28.7 +/- 17.4 pg/ml) than that of group B (15.9 +/- 10.6 pg/ml) and control group (6.0 +/- 5.7 pg/ml); and higher in group B patients than that of control group (P < 0.05). Although groups A and B did not differ according to plasma NOx levels (23.4 +/- 13.5 micromol/L vs. 32.8 +/- 22.7 micromol/L, P > 0.05), NOx levels in group A were lower than the control group (23.4 +/- 13.5 micromol/L versus 42.5 +/- 15.9 micromol/L, P < 0.05). Time domain HRV parameters were decreased in all patient groups. This was more prominent in group A. Additionally, HRV parameters were negatively correlated with ET-1 and TIMI frame counts. TIMI frame count was also significantly correlated with ET-1 and NOx levels (r = 0.61, P < 0.0001, r =-0.30, P < 0.05). Upon intravascular ultrasonography investigation, the common finding was longitudinally extended massive calcification throughout the epicardial arteries. Mean intimal thickness was 0.50 +/- 0.13 mm (group A; 0.58 +/- 0.11 mm, group B 0.47 +/- 0.12 mm, P = 0.029). The present study demonstrated that in patients with CSF, both increased plasma ET-1, decreased plasma NOx and diffuse atherosclerosis may cause the decrease in HRV by effecting myocardial blood flow.

Effect of Omacor on HRV parameters in patients with recent uncomplicated myocardial infarction - A randomized, parallel group, double-blind, placebo-controlled trial: study design [ISRCTN75358739

BackgroundA large body of data derived from animal, epidemiological and clinical studies indicate that n-3 polyunsaturated fatty acids have a favourable effect on the prognosis of patients with cardiovascular disease in general, and on reducing sudden death in particular.Depressed heart rate variability (HRV), an indicator of impairment of the autonomic nervous system, has been shown to be a powerful predictor of subsequent mortality in patients surviving an acute myocardial infarction. A multitude of studies have demonstrated this strong association, suggesting that the imbalance in the sympathic/parasympathetic system may facilitate emergence of ventricular arrhythmias.Heart rate variability parameters will be assessed in the present study, with the primary objective of evaluating the possible superiority of Omacor (a highly refined, concentrated omega-3 fatty acid) versus placebo in improving HRV from baseline to endpoint in patients with recent uncomplicated myocardial infarction. Both groups will receive optimal conventional treatment.The study will also explore and quantify improvement in time domain HRV indices and will assess the safety of administering Omacor to optimally treated post-infarction patients (conventional treatment).MethodsThis multi-centre study will evaluate the effect of Omacor 1 g, o.d. on time-domain HRV parameters in comparison to placebo o.d. in patients with recent uncomplicated transmural myocardial infarction.Patients will be screened during the first few days after the acute event as appropriate for the patient's condition, and after obtaining informed consent. Based on inclusion/exclusion criteria, a first 24-hour Holter recording will be performed. Two to five days later, screened patients still eligible for the study will undergo a second 24-hour Holter recording. After the second Holter recording, all patients will be randomly allocated to treatment with Omacor 1 g, o.d. or placebo o.d.One hundred patients will be followed in double-blind fashion for a six-month period after randomization. Visits, including 24-hour Holter recording and assessment of adverse events, will take place at one-month intervals ± five days after randomization, i.e., six times in all.

Time domain heart rate variability as a predictor of long-term prognosis after acute myocardial infarction.

Decreased heart rate variability (HRV) has been shown to be a predictor of both sudden cardiac death and cardiovascular death among patients surviving acute myocardial infarction (MI). However, the prognostic significance of time domain HRV in patients with MI is still controversial. In addition to the mean of all normal-to-normal (NN) intervals, we analyzed the prognostic significance of the 5 most widely used time domain parameters of HRV during long-term follow-up in patients surviving their first MI. Five time domain measures of HRV from 24-hour ECG were obtained after discharge in 260 consecutive patients (207 males; mean age, 60 years) surviving their first MI. These parameters included: standard deviation of all NN intervals, mean of standard deviations of all NN intervals in all 5-minute segments (SDNNi), standard deviation of the average of all NN intervals in all 5-minute segments, the square root of the mean of the sum of the squares of differences between adjacent NN intervals, and percentage of differences between adjacent NN intervals > 50 ms. The study endpoint was cardiovascular death. After follow-up for 67 months (range, 1 to 114 months), there were 55 cardiovascular deaths (21%) including 39 sudden deaths (15%). Multivariate Cox regression analysis showed that SDNNi < 30 ms was a significant predictor of cardiovascular death (hazard ratio, 4.98; 95% confidence interval [CI], 2.03 to 12.21; p < 0.001) as was number of ventricular premature complexes >/= 10 beats/hour (hazard ratio, 5.34; 95% CI, 2.26 to 12.62; p < 0.001), age >/= 70 years (hazard ratio, 3.65; 95% CI, 1.44 to 9.23; p = 0.006), and left ventricular ejection fraction < 45% (hazard ratio, 3.29; 95% CI, 1.13 to 9.57; p = 0.03). SDNNi < 30 ms was also an important predictor of sudden cardiac death (hazard ratio, 5.02; 95% CI, 1.49 to 16.85; p = 0.009). These data suggest that SDNNi is a significant time domain parameter of HRV for long-term prognosis in post-MI patients.

The effects of growth hormone therapy on heart rate variability in adults with growth hormone deficiency

Background: Growth hormone (GH) deficiency is associated with increased cardiovascular morbidity and mortality. Abnormalities in heart rate variability (HRV) (such as decreased cardiac sympathetic activity), which is a marker of cardiac autonomic tone, have been found in patients with GH deficiency. Objective: The purpose of this study was to investigate the effects of GH therapy on HRV in adults with GH deficiency. Methods: Adult patients with GH deficiency were eligible. HRV measurements were obtained by 24-hour measurements from Holter electrocardiography before and after 6 months of GH therapy in adult patients with GH deficiency. The following time domain parameters of HRV were calculated: the SD of the normal-to-normal (NN) interval (SDNN), the SD of the average NN interval (SDANN), the square root of the mean squared differences (RMSSD), and the proportion derived by dividing the number of interval differences of successive NN intervals >50 ms (NN50) by the total number of NN intervals (PNN50). Results: A total of 21 patients (7 men, 14 women; mean age, 46.0 ± 11.2 years) were enrolled. Thirteen patients had panhypopituitarism and 8 had normal adrenocorticotropic hormone secretion. At the end of 6 months of GH therapy, the mean values of the sympathetically influenced parameters SDNN (before GH treatment, 134.5 ± 6.0 ms; after GH treatment, 118.5 ± 8.0 ms) and SDANN (before GH treatment, 121.2 ± 6.0 ms; after GH treatment, 96.2 ± 9.1 ms) decreased significantly ( P < 0.05), but the parasympathetically influenced parameters RMSSD and PNN50 did not differ significantly from baseline. The mean heart rate and ventricular premature beats were not significantly different from baseline after GH therapy. Conclusions: In this patient population, cardiac sympathetic tone was increased, without an obvious arrhythmogenic effect, after 6 months of GH therapy.

Prognostic significance of heart rate variability in dilated cardiomyopathy

Background: Identifying high-risk individuals among patients with nonischemic dilated cardiomyopathy (DCM) is a major and unsolved task of clinical cardiology. We aimed to determine prognostic significance of heart rate variability (HRV) for predicting cardiac events in DCM patients with markedly depressed left ventricular function. Methods: In 69 DCM patients in sinus rhythm, with normal coronary angiography and mean ejection fraction 32 (11%) cardiac events defined as cardiac death or heart transplantation during a mean 20-month follow-up were related to baseline time-domain HRV parameters calculated from 24-h digital Holter monitoring. Results: There were 18 (26%) cardiac events (10 deaths and 8 heart transplantations). In multivariate Cox analysis, standard deviation of normal-to-normal intervals (SDNN) (hazard ratio: 1.35; 95% confidence interval 1.11–1.63; P=0.002) and ejection fraction (hazard ratio: 4.21; confidence interval 1.64–10.78; P=0.003) were significant and independent predictors of cardiac events. One-year event-free survival was significantly lower in patients with SDNN<80 ms compared to those with SDNN≥80 ms (35% vs. 89%, respectively; P<0.00005). Low SDNN was identifying high-risk patients among those with both depressed and relatively preserved left ventricular function. Conclusions: Broadly available time-domain HRV analysis adds independent prognostic information improving risk stratification of DCM patients and therefore it should be incorporated in routine clinical evaluation to determine patients’ priority for heart transplantation.

Comparison of heart rate variability and treadmill exercise score in patients with stable coronary artery disease

Depressed heart rate variability (HRV) is associated with increased mortality and morbidity with various forms of heart disease, and the Duke treadmill score (DTS) provides diagnostic and prognostic information for the evaluation of patients with coronary artery disease (CAD). Our study was aimed at assessing any possible correlation between HRV and DTS in stable CAD. We evaluated the correlation between the HRV assessed by using 24 hour ambulatory ECG monitoring, and treadmill exercise score in 37 patients with angiographically proven and clinically stable CAD. In univariate analysis, DTS showed a significant negative correlation with age (r = −0.89, p < 0.01) and a significant positive correlation with the square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) (r = 0.67, P < 0.05), percent difference between adjacent normal R-R intervals >50 ms (PNN50) (r = 0.69, P < 0.05), and mean of the standard deviation of all R-R intervals in all the 5-minute intervals (HRVM) (r = 0.63, P < 0.05). There is no significant correlation between DTS and standard deviation of all R-R intervals (SDNN), standard deviation of the averages of R-R intervals in all 5-minute segments of the entire recordings (SDANN) and standard deviation of the SDNN in all the 5-minute intervals (HRVSD). In multiple regression analysis, age was the only independent significant predictor of DTS (p < 0.01). DTS decreased with advancing age. SDNN, SDANN, RMSSD, HRVM and HRVSD were not apparent predictors for detecting of DTS. Age was an independent predictor of DTS. Although DTS was correlated with RMSSD, PNN50 and HRVM in patients with stable CAD, time domain parameters of HRV were not appearent predictor for DTS.

Effects of cigarette smoking on the circadian rhythm of heart rate variability

The effects of cigarette smoking on the circadian rhythm of heart rate variability (HRV) are not known. We studied the effects of cigarette smoking on the circadian rhythm of HRV in 24 smoking and 21 non-smoking healthy subjects. Twenty-four hour ambulatory electrocardiograms were recorded and time domain parameters of HRV (SDNN [standard deviation of all R-R intervals], SDANN [standard deviation of the averages of R-R intervals in all 5-minute segments of the entire recording], RMSSD [the square root of the mean of the sum of the squares of differences between adjacent R-R intervals]) were determined for the entire 24-hour period and for each 3-hour period. In total, SDNN and SDANN were significantly lower in smokers than non-smokers (116 +/- 26 vs 136 +/- 27, p < 0.05 for SDNN, 109 +/- 25 vs 121 +/- 24, p < 0.05 for SDANN). However, there were no statistical differences between smokers and non-smokers in heart rate (81 +/- 9 vs 76 +/- 10, p > 0.05) and RMSSD (32 +/- 12 vs 37 +/- 18, p > 0.05). These HRV parameters showed a circadian variation: they increased at night and decreased during the day in both groups. The parameters were lower in smokers than non-smokers during daytime (especially, between 8-14 hours). However, no differences were detected during night-time. Time domain parameters of HRV (SDNN, SDANN and RMSSD) in both smoking and non-smoking healthy subjects have a circadian rhythm. SDNN and SDANN were lower in smokers than non-smokers during daytime.

Effect of glycemic control on heart rate variability in type I diabetic patients with cardiac autonomic neuropathy

Diabetic cardiac autonomic neuropathy (CAN) is associated with a high risk of cardiovascular events. Previous studies have shown that strict glycemic control slows the deterioration of CAN as assessed by standard autonomic function tests but fails to show reversibility. The aim of this study was to evaluate the effect of glycemic control on early and advanced CAN in type I diabetic patients using power spectral analysis of heart rate variability (HRV). Ten patients with early and 13 patients with advanced CAN were enrolled in a program of intensified insulin treatment. Standard autonomic function tests and 24-hour time and frequency domain HRV parameters were obtained at baseline, 3, 6, and 12 months. Hemoglobin A 1C decreased from 9.5 ± 0.4% to 8.4 ± 0.5% (p = 0.02) in the early CAN group, and from 9.3 ± 0.4% to 8.2 ± 0.5% (p = 0.006) in the advanced CAN group. In general, both time and frequency domain HRV indexes tended to improve in patients with early CAN but continued to deteriorate in patients with advanced CAN. The low- and high-frequency power increased in patients with early CAN (229 ± 95 to 626 ± 563 ms 2 and 62 ± 30 to 183 ± 168 ms 2, respectively). The high-frequency power significantly improved at 12 months over baseline (p = 0.04), indicating increased parasympathetic tone. By contrast, these parameters continued to deteriorate in patients with advanced CAN (65 ± 32 to 46 ± 8 ms 2 and 193 ± 75 to 144 ± 33 ms 2, respectively). Autonomic function tests showed no significant change in both groups. These data show that a reversible metabolic component of CAN exists in patients with early CAN. Power spectral analysis of HRV allows early identification of potential reversibility as early as 1 year after the institution of strict glycemic control.

Time-dependent changes of heart rate variability after percutaneous transluminal angioplasty

Objectives It is not known whether the improvement of myocardial perfusion by percutaneous transluminal coronary angioplasty (PTCA) is followed by a response of the autonomic nervous system depending on the recovery of the myocardium. In this study we investigated changes of heart rate variability parameters in patients before and after PTCA at different time intervals. Methods In 42 patients with coronary artery disease documented on angiography, before and after PTCA 24-hour measurements of heart rate variability (HRV) were performed from Holter tapes. The time elapsed between the two measurements was 3 to 4 days in 26 patients and 6 to 8 months in 16 patients. Time domain parameters of HRV were calculated. Results Comparison of the two recordings showed that the parameters rMSSD, pNN50, and SDNN index decreased, whereas SDNN and SDANN increased. These changes were not statistically significant. A subgroup analysis revealed different results for patients with and without previous myocardial infarction: the parasympathetically and more sympathetically influenced parameters revealed different changes in these groups. Other variables such as ejection fraction or severity of coronary artery disease did not influence the HRV results. Although no statistically significant difference was seen on comparison of the patients with different recording intervals, patients with a longer interval between the two measurement periods showed higher values of all HRV parameters closer to normalized values. This observation may be explained by a delayed recovery of myocardial function after successful revascularization by PTCA. (Am Heart J 1998;135:755-61.)

Optimal parameters of short-term heart rate spectrogram for routine evaluation of diabetic cardiovascular autonomic neuropathy

Our aim was to select those parameters of heart rate variability (HRV) within its short-term power spectral analysis (PSA), which have a capability similar to that of the standard Ewing battery of cardiovascular function tests in determining different degrees of cardiovascular autonomic neuropathy (CAN) in diabetes and to compare the usefulness of both methods for diagnostic purposes in the everyday routine. Commonly used standard battery of cardiovascular autonomic function tests evaluated as total Ewing score as well as short-term PSA of HRV were used in 119 diabetic patients (age: 52.7±9.8, diabetes duration: 22.2±12.7 years). From this cohort, patients were selected according to the total Ewing score by matching for age, gender, BMI and diabetes type for 3 groups, each of 17 patients, with no CAN (total Ewing score 0–0.5), with early involvement (score 1.0–2.5) and with definite or severe CAN (score 3.0–5.0). Short-term PSA of HRV performed in three positions (supine1–standing–supine2) included frequency-domain and time-domain parameters of HRV. Cumulative spectral power of total frequency band (0.06–0.50 Hz) and spectral power of low-frequency band (0.06–0.15 Hz) during both supine positions proved to be the most selective and discriminating among all patient groups in inter-group comparison and in analysis of discriminance. The correlation between the total Ewing score and the cumulative spectral power of total frequency band was r=−0.87 ( P<0.001). About 83.2% of cases classified by short-term PSA of HRV using the variables selected by analysis of discriminance was congruent with the classification by the total Ewing score alone. Time expenditure for the performance of each examination was 31±10 min for Ewing test battery vs. 14±2 min for short-term PSA of HRV ( P<0.001). In summary, the latter method showed similar diagnostic value concerning the CAN as the classical Ewing standard battery of cardiovascular function tests, although its application proved to be shorter, less stressful and more independent from patient cooperation. Cumulative spectral power of total frequency band (LFHF cumpower) can be used for overall description of the degree of cardiac denervation in diabetes while using short-term PSA of HRV.