Coefficient Of Variation Of The R-R Interval Research Articles

Heart rate variability in patients presenting with neurally mediated syncope in an emergency department

BackgroundNeurally mediated syncope (NMS) is a disorder of autonomic nervous system (ANS) regulation. Orthostatic stress is one of the most common causative factors seen in clinical practice. Analysis of heart rate variability (HRV) is a non-invasive method that is used to assess ANS regulation. In this study, we investigated the pathophysiology of NMS using HRV in our emergency department. MethodsThe subjects were 19 patients (age 25.8 ± 6.2 years old) who presented with NMS and 20 healthy individuals (age 26.6 ± 2.7 years old) who served as controls. HRV was measured in supine, sitting and standing positions. Heart rate (HR), low frequency (LF 0.04–0.15 Hz), high frequency (HF > 0.15 Hz), and coefficient of variation of the R-R interval (CVRR) were determined. ResultsLF and HF in the supine position were significantly lower in the patients with NMS (p < 0.05). HR was higher in all positions in patients with NMS than in healthy individuals (p < 0.05). CVRR in the supine position was lower in the patients with NMS (p < 0.001), and it was significantly lower in patients who were positive in an orthostatic test (p = 0.0017). Area under the curve was calculated to be 0.824, and at the cutoff value of 4.997 of CVRR in supine, the sensitivity and the specificity were 78.9% and 85.0%. ConclusionThe sympathetic and parasympathetic nervous systems were both suppressed in patients with NMS. In post-syncope, parasympathetic withdrawal, rather than sympathetic reactivation, was responsible for the increased HR after syncope. CVRR may serve as a new clinical biomarker in the emergency department.

Effect of Myoarchitectonic Spinolaminoplasty on Concurrent Hypertension in Patients With Cervical Spondylotic Myelopathy.

ObjectiveWhen treating patients with cervical spondylotic myelopathy (CSM), we often note amelioration in concomitant hypertension after surgery. To assess the effects of surgery and the mechanisms thereof, blood pressure (BP) and parasympathetic nervous activity were monitored prospectively in CSM patients undergoing surgery. MethodsSixty-eight consecutive CSM patients who underwent surgery with myoarchitectonic spinolaminoplasty were enrolled. BP and electrocardiography were recorded preoperatively and at 1, 3, and 6 months postoperatively. Forty-six patients completed the scheduled follow-ups and were analyzed. Preoperatively, 17 had a mean BP higher than 100 mmHg (the HT group) and 12 had hypertension despite taking medication (the HT-refractory group). To evaluate alterations in parasympathetic function, the coefficient of variation of the RR interval (CVRR) was evaluated. ResultsA significant BP reduction was observed in the HT group 6 months after surgery, but not in the normotensive group (n=29). The effect was more remarkable in the HT-refractory group. A transient BP increase at 1 and 3 months after surgery was observed in all groups. Comparisons were made between groups classified by age (over 65 years or younger than 60 years) and the presence or absence of an intramedullary hyperintense T2 signal on magnetic resonance imaging, but no significant differences were detected. Measurements of CVRR did not significantly differ between the groups over the course of follow-up. ConclusionHypertension coexisting with CSM can be ameliorated after surgical treatment. The effect is likely to be mediated by moderation of sympathetic activity, rather than parasympathetic activation. We believe that a combination of adequate decompression of the spinal cord and relief from musculoskeletal stresses effectuate this moderation.

Association Between Diabetic Microangiopathies and Glycemic Variability Assessed by Continuous Glucose Monitoring.

The aim of this retrospective study was to elucidate the association between glucose profile using the continuous glucose monitoring system (CGMS) and microvascular complications in patients with type 2 diabetes mellitus (T2DM). The subjects were 160 inpatients with T2DM. The mean blood glucose (MBG) level, percentage of time in a 24-hour period spent with blood glucose level higher than 180 mg/dl (time at >180 mg/dl), standard deviation (SD), and mean amplitude of glycemic excursions (MAGE) were measured continuously over 48 hours using the CGMS. The primary outcome was the association between microvascular complications and glycemic variability. The secondary outcome was the association between microangiopathies and MBG. The SD and MAGE were not associated with presence of microangiopathies or number of complications. There were also no associations between abnormal vibratory sensation in the bilateral lower extremities, coefficient of variation of the R-R interval (CVRR), retinopathy stage, nephropathy stage, or microalbuminuria. MBG was associated, however, with retinopathy, retinopathy stage, and number of complications. Time at >180 mg/dl correlated with abnormal vibratory sensation in the bilateral lower extremities and presence or stage of retinopathy. MBG and time at >180 mg/dl were not associated with presence or stage of nephropathy. Our findings suggest that broad glycemic variability was not associated with microvascular complications, the number of which increased in patients with a high mean glucose level and long time spent with hyperglycemia. It is important, therefore, to reduce the mean glucose level and time spent with hyperglycemia to prevent future microangiopathies.

Cardiac rehabilitation in patients with cardiovascular disease leads various hemodynamic parameters obtained using simple non-invasive tests to their appropriate levels

We evaluated whether comprehensive cardiac rehabilitation (CR) in patients with cardiovascular disease (CVD) could improve various hemodynamic parameters obtained using simple non-invasive tests. We analyzed 48 CVD patients with (n=38, CR group) or without (n=10, non-CR group) a CR program, and prospectively followed them for 12months. Various parameters were measured at baseline and after 12months using 3 simple non-invasive tests: blood pressure (BP) and severity of atherosclerosis [arterial velocity pulse index (AVI) and atrial pressure volume index] were determined using PASESA®, an index of total autonomic nerve activity and a coefficient of variation of the R-R interval (CVRR) were determined using eHEART®, and the total peripheral resistance, stroke volume and cardiac index (CI) were determined using nico®. The main hemodynamic parameters did not change between baseline and 12months in both groups. Patients in the CR group were divided into higher (H-) and lower (L-) systolic BP (SBP) or AVI according to the average value of SBP or AVI at baseline in the CR group. Patients with H-SBP or H-AVI in the CR group showed a significant reduction of SBP or AVI at 12months. In addition, patients in the CR group were divided into H- and L- CI or CVRR according to the average value of CI or CVRR at baseline in the CR group. Patients with L-CI or L-CVRR in the CR group significantly improved after 12months. In conclusion, CR may lead various hemodynamic parameters obtained using simple non-invasive tests to their appropriate levels.

Body mass index and severity of Parkinsonism in multiple system atrophy

Patients with neurodegenerative disorders lose body weight as their diseases progress. In Parkinson’s disease (PD), however, autonomic dysfunction is associated with increased body mass index (BMI). We investigated the correlation between BMI, clinical features, and autonomic dysfunction in patients with multiple system atrophy with predominant parkinsonism (MSAP). BMI, clinical features, cardiac 123Imetaiodobenzylguanidine scintigraphy (MIBG), Hoehn and Yahr (H-Y) stage, and the coefficient of variation of the R-R interval (CVRR) were analyzed in 50 patients with MSA-P. BMI showed no significant correlation with MIBG parameters or CVRR. On the other hand, the H-Y stage was significantly negatively correlated with BMI. Higher H-Y stage indicates a more severe neuromuscular state in MSA-P and is considered to be related to higher energy expenditure and decrease of BMI. Patients with MSA-P lose weight as the disease progresses. This is the first report indicating a significant correlation between disease severity and BMI decrease in MSA.

Body mass index and severity of parkinsonism in multiple system atrophy

Patients with neurodegenerative disorders lose body weight as their diseases progress. In Parkinson’s disease (PD), however, autonomic dysfunction is associated with increased body mass index (BMI). We investigated the correlation between BMI, clinical features, and autonomic dysfunction in patients with multiple system atrophy with predominant parkinsonism (MSAP). BMI, clinical features, cardiac 123Imetaiodobenzylguanidine scintigraphy (MIBG), Hoehn and Yahr (H-Y) stage, and the coefficient of variation of the R-R interval (CVRR) were analyzed in 50 patients with MSA-P. BMI showed no significant correlation with MIBG parameters or CVRR. On the other hand, the H-Y stage was significantly negatively correlated with BMI. Higher H-Y stage indicates a more severe neuromuscular state in MSA-P and is considered to be related to higher energy expenditure and decrease of BMI. Patients with MSA-P lose weight as the disease progresses. This is the first report indicating a significant correlation between disease severity and BMI decrease in MSA.

PP.12.01

Objective: We evaluated orthostatic upright postural blood pressure (BP) changes and autonomic nervous function during simple standing-up test in community-based subjects. The present study was conducted to evaluate the influences of age on the results of BP changes and autonomic nervous function in orthostatic changes. Design and method: A total of 1915 subjects ranging from 15 to 80 years of age (mean age = 54.0 y.o;795 males and 1120 females) were selected from the participants in a Wakayama population-based health study. They underwent a simple standing-up test, and during the test brachial BP was measured every min and the R-R intervals of ECG were continuously evaluated. To evaluate autonomic fluctuations, we calculated the coefficient of variation of the R-R interval (CVRR), the ratio of low to high frequency heart rate variability (LF/HF), and the coefficient of component variance of high frequency (CCVHF).The results of BP and autonomic function at standing were analyzed chronologically in 10-year age intervals. Results: SBP (R2 = 0.987) and pulse pressure significantly increased and heart rate (HR), log LF/HF, CCVHF and CVRR significantly decreased substantially with age at baseline. When changing positions from sitting to standing, SBP, HR, log LF/HF, CVRR significantly decreased and CCVHF significantly increased chronologically. Systolic BP when changing positions from sitting to standing was defined δSBP, δ SBP was higher in males than in females (5.90 vs 4.43 mmHg, p = 0.008). δ SBP significantly correlate with CVRR, CCVHF both baseline and at standing, age and gender. In multiple regression analysis, SBP changes after standing resulted to be significantly associated to CVRR at standing (β=0.122, p = 0.0001), age and gender. Conclusions: At the orthostatic position, the differences of SBP, HR, log LF/HF, CVRR significantly decreased and CCVHF significantly increased substantially with age. SBP changes after standing resulted to be significantly associated to CVRR at standing, age and gender. These results demonstrate that aging clearly influences autonomic nervous function and blood pressure-changes at standing may relate to parasympathetic nervous activity.

Serum HDL-C is Positively Related to CVRR as an Index of ANS, which Relation is Attenuated by Rosuvastatin

An impairment of the Autonomic Nervous System (ANS) has been found in chronic heart failure (CHF). Decreased serum HDL-Cholesterol (HDL-C) level is associated with the progression of atherosclerosis. Few papers report that HDL-C is associated with HRV, which reflects ANS. MIBG is a tool to evaluate ANS, which isn't usually done in clinic. The coefficient of variation of the R-R interval (CVRR) could be used instead of MIBG, which could be obtained easily, even in clinic. So I studied the possible direct correlation between CVRR as one of the parameters of HRV on behalf of ANS and serum HDL-C levels in cardiovascular patients such as hypertention, angina pectoris and heart failure.

Cardiac and autonomic nerve function after reduced-intensity stem cell transplantation for hematologic malignancy in patients with pre-transplant cardiac dysfunction

Recent reports have shown that cardiomyopathy caused by hemochromatosis in severe aplastic anemia is reversible after reduced-intensity allogeneic stem-cell transplantation (RIST). We comprehensively evaluated cardiac and autonomic nerve function to determine whether cardiac dysfunction due to causes other than hemochromatosis is attenuated after RIST. In five patients with cardiac dysfunction before transplant, we analyzed the changes in cardiac and autonomic nerve function after transplant, using electrocardiography (ECG), echocardiography, radionuclide angiography (RNA), serum markers, and heart rate variability (HRV), before and up to 100 days after transplant. There was no significant improvement in cardiac function in any patient and no significant alteration in ECG, echocardiogram, RNA, or serum markers. However, on time-domain analysis of HRV, the SD of normal-to-normal RR intervals (SDNN) and the coefficient of variation of the RR interval (CVRR) decreased significantly 30 and 60 days after transplant (P = 0.04 and 0.01, respectively). Similarly, on frequency-domain analysis of HRV, low and high frequency power (LF and HF) significantly and temporarily decreased (P = 0.003 and 0.03, respectively). Notably, in one patient who had acute heart failure after transplantation, the values of SDNN, CVRR, r-MSSD, LF, and HF at 30 and 60 days after transplantation were the lowest of all the patients. In conclusion, this study suggests that (a) RIST is well-tolerated in patients with cardiac dysfunction, but we cannot expect improvement in cardiac dysfunction due to causes other than hemochromatosis; and (b) monitoring HRV may be useful in predicting cardiac events after RIST.

Successful Treatment of Obstructive Sleep Apnea Syndrome Improves Autonomic Nervous System Dysfunction

Autonomic nervous system (ANS) dysfunction may be implicated in the subsequent development of cardiovascular disease in patients with obstructive sleep apnea syndrome (OSAS). To confirm the relation between OSAS and ANS dysfunction, we prospectively investigated ANS function in 7 patients with moderate or severe OSAS; 7 healthy age-matched volunteers were for control. We also studied ANS function before and after treatment in the patients with OSAS to evaluate the effect of OSAS treatment on ANS dysfunction. The body mass index of patients with OSAS was 32.2 (27.4–45) (median [range]) kg/m2. The patients were treated by nasal continuous positive airway pressure (n = 5) or uvulopalatopharyngoplasty (n = 2). The apnea/hypopnea index decreased markedly from 42.1 (30.6–77.2) events/hr of sleep before treatment to 2.3 (1.4–3.8) after treatment. To evaluate ANS function, the coefficient of variation of the RR interval (CV-RR) and corrected QT (QTc) interval on the electrocardiogram at rest and the heart rate (HR) responses to blood pressure (BP) changes during the Valsalva maneuver were studied. Baseline HR of OSAS patients was significantly higher than that of the control subjects (p < .05). The Valsalva ratio (VR), baroreflex sensitivity (BRS), and CV-RR values in patients with OSAS were significantly lower than those of the control subjects (all, p < .005). However, there were no significant differences in systolic and diastolic BP or QTc intervals. After treatment, VR, BRS, and CV-RR values increased significantly compared with those before treatment in patients with OSAS (all, p < .05). There were no significant differences in systolic and diastolic BP, HR, or QTc intervals measured before and after treatment. These results suggest that impaired ANS function is present in patients with OSAS and can be improved by successful treatment of OSAS.

Autonomic nervous function in patients with vertigo--evaluation for static function, variation and dynamic change using power spectral analysis of RR intervals

Power spectral analysis of RR intervals (PSA) of 94 vertiginous patients with associated autonomic nervous dysfunction (AND group), 31 patients with vertebro-basilar insufficiency (VBI group) and 25 controls were analyzed in supine and upright positions. In addition static function, variation from the supine to the upright position and dynamic change in autonomic nervous function (ANF) from the supine to the upright position were examined. Heart rate was recorded for 120 seconds in the supine and 40 seconds in the upright position. RR intervals for each 20-second period were computed using FFT (Fast Fourier Transformation), and the ratio of low frequency power (0.05-0.15 Hz) to high frequency power (0.15-0.4 Hz) (L/H) of PSA were analyzed as an index of sympathetic activity. The PSA was examined by the following three parameters; L/H at rest during the 80-second period from 20 to 100 seconds (static function), the L/H variation between each 20-second period from 0 to 160 seconds (variation) and the ratio of L/H to that in the upright position (dynamic change). The results of PSA were compared with those of pulse wave velocity (PWV) and the coefficient of variation of the RR interval (CVRR), and association between attacks of vertigo and ANF was determined. The results of static function of PSA and the results of PWV and CVRR were very similar, indicating that both methods are useful for evaluating ANF in vertiginous patients. In the AND group the variation in sympathetic activity tended to be larger in patients with sympathetic hyperfunction and parasympathetic hypofunction and in the patients with sympathetic hypofunction and parasympathetic hyperfunction resulting from PWV and CVRR, than in the controls. The dynamic change in patients with sympathetic hyperfunction and parasympathetic hypofunction resulting from PWV and CVRR was also significantly lower than that in the controls (p < 0.01). Some patients in the AND group already showed excessive sympathetic hyperfunction at rest, and changing the position from supine to upright might trigger sympathetic hypofunction, causing an attack of vertigo. The PSA results in the VBI group were similar to those in the controls, suggesting that sympathetic dysfunction did not affect VBI induced vertigo.

Prolonged QT interval in alcoholic autonomic nervous dysfunction.

QT prolongation on electrocardiography is related to sudden cardiac death and is frequently found in alcoholics. We studied QT prolongation in relation to the function of cardiac autonomic nerves assessed by the coefficient of variation of the R-R interval (CVRR) in three age-matched groups of men: 32 alcoholics with autonomic nervous dysfunction (AN), 32 alcoholics without AN, and 32 healthy controls. The QTc interval and CVRR were measured at rest on the 30th day of abstinence, when electrolyte imbalance had disappeared. Subjects with arrhythmia, conduction abnormality, cardiomegaly, ischemic heart disease or diabetes mellitus were excluded. A CVRR of less than 80% of standard predicted value was judged to represent AN. In alcoholics, QTc correlated negatively with the ratio of CVRR to its standard value (r = -0.49, p < 0.0001). The incidence of QTc prolongation was higher in alcoholics with AN (46.9%) than in alcoholics without AN (21.9%, p < 0.05). QTc prolongation was not observed in healthy controls. The QTc interval was significantly (p < 0.01) longer in alcoholics with AN (444 +/- 20 msec) than in alcoholics without AN (426 +/- 17) and in healthy controls (398 +/- 18). These results suggest that alcoholism causes dysfunction of the autonomic nerves as well as worsening QT prolongation, and this may predispose such patients to sudden cardiac death.

Loss of nocturnal decline in blood pressure in diabetic patients with autonomic neuropathy.

We investigated loss of the nocturnal decline in blood pressure (BP) and its mechanism in diabetes mellitus with autonomic neuropathy (ANP). BP was measured every 30 min using ambulatory BP recorders in 52 diabetic patients and 11 nondiabetic controls. As an index of autonomic nervous dysfunction, CVRR (the coefficient of variation of the R-R interval on ECGs) and diastolic blood pressure response on standing were measured. Plasma volume (PV) was measured with RISA. The difference between daytime mean BP (09:00 to 13:00) and nighttime mean BP (01:00 to 05:00) was analyzed. The normal control group showed a significant reduction in mean BP during the nighttime (-12.8 +/- 7.5 mmHg) as compared with the DM group (-3.3 +/- 8.6 mmHg, p < 0.001). The diabetic patients with loss of the nocturnal decline in blood pressure showed autonomic nervous dysfunction and increased PV. In conclusion, the nocturnal elevation of blood pressure might result from an imbalance between reduced tone of sympathetic and parasympathetic functions in addition to the postural effect and increased plasma volume present in diabetic patients.