Prognostic significance of heart rate variability in dilated cardiomyopathy

The effects of anesthetic drug choice on heart rate variability and echocardiography parameters in cats

Heart rate variability (HRV) is one of the assessments of cardiovascular risk during general anesthesia. This study aimed to assess the effects of an anesthetic drug on HRV in cats and to provide information for clinical applications. Twenty-four healthy client-owned cats of various breeds, 12 females and 12 males scheduled for elective surgery, were enrolled in this study. The cats were premedicated and induced with 4 protocols: protocol 1, diazepam (0.3 mg/kg) and propofol (2-4 mg/kg) IV; protocol 2, diazepam (0.3 mg/kg) and alfaxalone (1-3 mg/kg) IV; protocol 3, diazepam (0.3 mg/kg) and ketamine (3-5 mg/kg) IV; and protocol 4, xylazine (1 mg/kg) and tiletamine/zolazepam (Zoletil) (5 mg/kg) IM. The heart rate and HRV of the 24 cats were collected before and at least 1 h after administering the anesthetic drugs. Echocardiography was performed to evaluate heart function. Oscillometric blood pressure monitoring was used to obtain the mean blood pressure. After anesthetic drug administration, higher heart rates were found in cats premedicated and induced with alfaxalone (p = 0.045) than in the other protocols. The lowest heart rate (HR) values were found in cats in protocol 4 using xylazine and Zoletil. The HRV low frequency (LF) and high frequency (HF) power ratios increased in all protocols except for cats premedicated and intubated with propofol. The standard deviation of the regular sinus beats (SDNN) was higher in cats premedicated and induced with ketamine than in other anesthetic protocols (p = 0.015). An increase in sympathetic activity and reduced HRV is associated with high blood pressure and left atrial dimension. The percentage of fractional shortening (FS) decreased in cats premedicated with ketamine. The results showed that the anesthesia method using diazepam and propofol caused the least disturbance of HRV compared with other anesthesia methods that were used in this study.

Impact of a combination of pimobendan, furosemide, and enalapril on heart rate variability in naturally occurring, symptomatic, myxomatous mitral valve degeneration dogs

BACKGROUND

Pimobendan, diuretics, and an angiotensin-converting enzyme inhibitor (ACEi) are widely used for the management of chronic valvular heart disease in dogs; however, the effects of that combination on heart rate variability (HRV) are unknown. The purpose of this study was to assess the HRV of symptomatic myxomatous mitral valve degeneration (MMVD) dogs in response to therapy with a combination of pimobendan, diuretics, and ACEi.

RESULTS

MMVD stage C (n = 17) dogs were enrolled and a 1-hour Holter recording together with echocardiography, blood pressure measurement, and blood chemistry profiles were obtained before and 1, 3, and 6 months after oral treatment with pimobendan (0.25 mg/kg), enalapril (0.5 mg/kg), and furosemide (2 mg/kg) twice daily. The results revealed that MMVD stage C dogs at the baseline had lower values of time-domain indices, low frequency (LF), high frequency (HF), and total power, as well as higher value of LF/HF. Triple therapy significantly increases these parameters in MMVD stage C dogs (P < 0.05). A positive moderate correlation was observed between time domain parameters and a left ventricular internal diastole diameter normalized to body weight (P < 0.05).

CONCLUSIONS

It can be concluded that MMVD stage C dogs possess low HRV due to either the withdrawal of parasympathetic tone or enhanced sympathetic activation, and a combination therapy was shown to enhance cardiac autonomic modulation inferred from the increased heart rate variability. Therefore, a combination therapy may be useful for restoring normal autonomic nervous system activity in dogs with MMVD stage C.

Non-invasive markers for sudden cardiac death risk stratification in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a common yet challenging cardiac disease. Great strides have been made in improving DCM prognosis due to heart failure but sudden cardiac death (SCD) due to ventricular arrhythmias remains significant and challenging to predict. High-risk patients can be effectively managed with implantable cardioverter defibrillators (ICDs) but because identification of what is high risk is very limited, many patients unnecessarily experience the morbidity associated with an ICD implant and many others are not identified and have preventable mortality. Current guidelines recommend use of left ventricular ejection fraction and New York Heart Association class as the main markers of risk stratification to identify patients who would be at higher risk of SCD. However, when analysing the data from the trials that these recommendations are based on, the number of patients in whom an ICD delivers appropriate therapy is modest. In order to improve the effectiveness of therapy with an ICD, the patients who are most likely to benefit need to be identified. This review article presents the evidence behind current guideline-directed SCD risk markers and then explores new potential imaging, electrophysiological and genetic risk markers for SCD in DCM.

SDNN24 Estimation from Semi-Continuous HR Measures

The standard deviation of the interval between QRS complexes recorded over 24 h (SDNN24) is an important metric of cardiovascular health. Wrist-worn fitness wearable devices record heart beats 24/7 having a complete overview of users' heart status. Due to motion artefacts affecting QRS complexes recording, and the different nature of the heart rate sensor used on wearable devices compared to ECG, traditionally used to compute SDNN24, the estimation of this important Heart Rate Variability (HRV) metric has never been performed from wearable data. We propose an innovative approach to estimate SDNN24 only exploiting the Heart Rate (HR) that is normally available on wearable fitness trackers and less affected by data noise. The standard deviation of inter-beats intervals (SDNN24) and the standard deviation of the Average inter-beats intervals (ANN) derived from the HR (obtained in a time window with defined duration, i.e., 1, 5, 10, 30 and 60 min), i.e., ANN=60HR (SDANNHR24), were calculated over 24 h. Power spectrum analysis using the Lomb-Scargle Peridogram was performed to assess frequency domain HRV parameters (Ultra Low Frequency, Very Low Frequency, Low Frequency, and High Frequency). Due to the fact that SDNN24 reflects the total power of the power of the HRV spectrum, the values estimated from HR measures (SDANNHR24) underestimate the real values because of the high frequencies that are missing. Subjects with low and high cardiovascular risk show different power spectra. In particular, differences are detected in Ultra Low and Very Low frequencies, while similar results are shown in Low and High frequencies. For this reason, we found that HR measures contain enough information to discriminate cardiovascular risk. Semi-continuous measures of HR throughout 24 h, as measured by most wrist-worn fitness wearable devices, should be sufficient to estimate SDNN24 and cardiovascular risk.

Error Estimation of Ultra-Short Heart Rate Variability Parameters: Effect of Missing Data Caused by Motion Artifacts

Application of ultra–short Heart Rate Variability (HRV) is desirable in order to increase the applicability of HRV features to wrist-worn wearable devices equipped with heart rate sensors that are nowadays becoming more and more popular in people’s daily life. This study is focused in particular on the the two most used HRV parameters, i.e., the standard deviation of inter-beat intervals (SDNN) and the root Mean Squared error of successive inter-beat intervals differences (rMSSD). The huge problem of extracting these HRV parameters from wrist-worn devices is that their data are affected by the motion artifacts. For this reason, estimating the error caused by this huge quantity of missing values is fundamental to obtain reliable HRV parameters from these devices. To this aim, we simulate missing values induced by motion artifacts (from 0 to 70%) in an ultra-short time window (i.e., from 4 min to 30 s) by the random walk Gilbert burst model in 22 young healthy subjects. In addition, 30 s and 2 min ultra-short time windows are required to estimate rMSSD and SDNN, respectively. Moreover, due to the fact that ultra-short time window does not permit assessing very low frequencies, and the SDNN is highly affected by these frequencies, the bias for estimating SDNN continues to increase as the time window length decreases. On the contrary, a small error is detected in rMSSD up to 30 s due to the fact that it is highly affected by high frequencies which are possible to be evaluated even if the time window length decreases. Finally, the missing values have a small effect on rMSSD and SDNN estimation. As a matter of fact, the HRV parameter errors increase slightly as the percentage of missing values increase.

Autonomic dysfunction in cardiac amyloidosis assessed by heart rate variability and heart rate turbulence

BACKGROUND

Cardiac amyloidosis (CA) is characterized by left ventricular hypertrophy (LVH) and autonomic nervous imbalance due to amyloid infiltration. However, autonomic dysfunction is often seen in heart failure (HF) with LVH from other etiologies. We aimed to characterize autonomic dysfunction in CA from other etiologies of LVH.

METHODS

Fifty-five HF patients with LVH (35 males, mean age 65 ± 16 years) were enrolled. LVH was defined as left ventricular mass index measured by echocardiography >95 g/m2 in women and 115 g/m2 in men. The etiology was as follows: amyloid light chain (AL)-CA, n = 14; hypertrophic cardiomyopathy, n = 21; and aortic stenosis (AS), n = 20. With the patient in a clinically stable condition, heart rate variability (HRV) and heart rate turbulence (HRT), which reflect autonomic dysfunction, were measured using Holter monitoring and compared among the three groups.

RESULTS

Brain natriuretic peptide levels, LVH severity, left ventricular ejection fraction, and tissue Doppler index E/e' did not differ among the three groups. However, severe abnormalities of HRV and HRT were obtained in AL-CA. In the ROC analysis to identify AL-CA in HF with LVH, the best cutoff value for standard deviation of all R-R intervals, standard deviation of the 5-min mean R-R intervals, turbulence onset, and turbulence slope were 68.5 ms (AUC: 0.865), 58.5 ms (AUC: 0.834), 0.25% (AUC: 0.813), and 1.00 ms/RR (AUC 0.736), respectively.

CONCLUSION

Autonomic dysfunction is a hallmark of AL-CA, and its noninvasive assessment by Holter monitoring may be a useful tool for differential diagnosis of HF with LVH.

The effects of anesthetic drug choice on heart rate variability in dogs

Objective:

The objective of this study was to assess the effects of anesthetic drugs on heart rate (HR) and heart rate variability (HRV) in dogs.

Materials and Methods:

Twelve healthy client-owned dogs of various breeds, including five females and seven males were used for elective surgery in this study. The dogs were pre-medicated with four protocols; (1) alfaxalone [at 3 mg/kg body weight (bwt)], (2) zolazepam + tiletamine (Zoletil) (at 5 mg/kg bwt), (3) diazepam (at 0.3 mg/kg bwt) + ketamine (at 5 mg/kg bwt), and (4) diazepam (at 0.3 mg/kg bwt) + propofol (at 5 mg/kg bwt). The HR and HRV of 12 dogs were recorded 20 min before and after the administration of the anesthetic drugs. Doppler was used to obtain systolic, diastolic, and mean blood pressures.

Results:

After anesthetic drug administration, the dogs pre-medicated and inducted with alfaxalone had the lowest HR values as compared with those of other protocols. The HRV low frequency and high frequency power ratio decreased in the dogs pre-medicated and intubated with alfaxalone.

Conclusion:

This study demonstrates that alfaxalone preserves the cardiovascular function; and hence, is considered as safe to use for the surgical applicability in dogs.

Clinical and Echocardiographic Predictors of Arrhythmias Detected With 24-Hour Holter Electrocardiography Among Hypertensive Heart Failure Patients in Nigeria

Background

Hypertensive heart failure (HHF) is the commonest form of heart failure in Nigeria. There is paucity of data in Nigeria on 24-hour Holter electrocardiography (24-HHECG) and important predictors of arrhythmias among HHF patients.

Objectives

To determine the 24-HHECG characteristics among HHF patients. To determine the clinical and echocardiographic predictors of arrhythmias detected using 24-HHECG among HHF patients.

Methods

A total of 100 HHF patients as well as 50 age-matched and sex-matched apparently healthy controls were prospectively recruited over a period of 1 year. They all had baseline laboratory tests, echocardiography, and 24-HHECG.

Results

Hypertensive heart failure patients had significantly higher counts of premature ventricular contractions (PVCs) than the controls (P ≤ .001). Ventricular tachycardia (VT) was recorded in 29% of HHF patients as compared with controls who had no VT on 24-HHECG. The standard deviation of all normal to normal sinus RR intervals over 24 hours (SDNN) was abnormally reduced among HHF patients when compared with controls (P = .046). There was positive correlation between atrial fibrillation (AF) and the following parameters: PVCs (r = .229, P = .015), New York Heart Association (NYHA) (r = .196, P = .033), and VT (r = .223, P = .018). Following multiple linear regression, left ventricular ejection fraction (LVEF) (P ≤ .001) and serum urea (P = .037) were predictors of PVCs among HHF patients. Serum creatinine (P ≤ .001), elevated systolic blood pressure (SBP) (P = .005), and PVCs (P ≤ .001) were important predictors of VT among HHF patients.

Conclusions

Renal dysfunction and reduced LVEF were important predictors of ventricular arrhythmias. High counts of PVCs and elevated SBP were predictive of the occurrence of VT among HHF patients. The NYHA class and ventricular arrhythmias have a significant positive correlation with AF. The SDNN is reduced in HHF patients.

Sildenafil improves heart rate variability in dogs with asymptomatic myxomatous mitral valve degeneration

Myxomatous mitral valve degeneration (MMVD) causes an imbalance of sympathovagal activity resulted in poor cardiac outcomes. Phosphodiesterase-5 inhibitors have been revealed cardioprotective effect in patients with heart diseases. This study aimed to 1) compare the heart rate variability (HRV) between asymptomatic MMVD and healthy dogs and 2) assess long-term effects of sildenafil and enalapril on time- and frequency-domains analyzes. Thirty-four dogs with MMVD stage B1 or B2 and thirteen healthy dogs were recruited into the study. MMVD dogs were divided into 3 subgroups: control (n=13), sildenafil (n=12) and enalapril (n=9). HRV was analyzed from 1-hr Holter recording at baseline (D0) in all dogs and at 30, 90 and 180 days after treatment. The results showed that MMVD dogs had significant higher heart rate (HR), systemic blood pressures, the ratio of low to high frequency (LF/HF) and had significant decreased standard deviation of all normal to normal RR intervals (SDNN) and the percentage of the number of normal-to-normal sinus RR intervals with differences >50 msec computed over the entire recording (pNN50) when compared with healthy dogs (P<0.05). Neither time nor frequency domain parameters were different among subgroups of MMVD dogs at D0. After treatment with sildenafil for 90 days, both time- and frequency-domain parameters were significantly increased when compared with control and enalapril groups. This study demonstrated that sildenafil improves HRV in asymptomatic MMVD dogs suggesting that sildenafil should be used in the MMVD dogs to restore the sympathovagal balance.

Ivabradine improves heart rate variability in patients with nonischemic dilated cardiomyopathy

Background

Ivabradine is a novel specific heart rate (HR)-lowering agent that improves event-free survival in patients with heart failure (HF).

Objectives

We aimed to evaluate the effect of ivabradine on time domain indices of heart rate variability (HRV) in patients with HF.

Methods

Forty-eight patients with compensated HF of nonischemic origin were included. Ivabradine treatment was initiated according to the latest HF guidelines. For HRV analysis, 24-h Holter recording was obtained from each patient before and after 8 weeks of treatment with ivabradine.

Results

The mean RR interval, standard deviation of all normal to normal RR intervals (SDNN), the standard deviation of 5-min mean RR intervals (SDANN), the mean of the standard deviation of all normal-to-normal RR intervals for all 5-min segments (SDNN index), the percentage of successive normal RR intervals exceeding 50 ms (pNN50), and the square root of the mean of the squares of the differences between successive normal to normal RR intervals (RMSSD) were low at baseline before treatment with ivabradine. After 8 weeks of treatment with ivabradine, the mean HR (83.6 ± 8.0 and 64.6 ± 5.8, p < 0.0001), mean RR interval (713 ± 74 and 943 ± 101 ms, p < 0.0001), SDNN (56.2 ± 15.7 and 87.9 ± 19.4 ms, p < 0.0001), SDANN (49.5 ± 14.7 and 76.4 ± 19.5 ms, p < 0.0001), SDNN index (24.7 ± 8.8 and 38.3 ± 13.1 ms, p < 0.0001), pNN50 (2.4 ± 1.6 and 3.2 ± 2.2 %, p < 0.0001), and RMSSD (13.5 ± 4.6 and 17.8 ± 5.4 ms, p < 0.0001) substantially improved, which sustained during both when awake and while asleep.

Conclusion

Our findings suggest that treatment with ivabradine improves HRV in nonischemic patients with HF.

Effect of methamphetamine dependence on heart rate variability

Methamphetamine (METH) is an increasing popular and highly addictive stimulant associated with autonomic nervous system (ANS) dysfunction, cardiovascular pathology and neurotoxicity. Heart rate variability (HRV) has been used to assess autonomic function and predict mortality in cardiac disorders and drug intoxication, but has not been characterized in METH use. We recorded HRV in a sample of currently abstinent individuals with a history of METH dependence compared to age- and gender-matched drug-free comparison subjects. HRV was assessed using time domain, frequency domain, and non-linear entropic analyses in 17 previously METH-dependent and 21 drug-free comparison individuals during a 5 minute rest period. The METH-dependent group demonstrated significant reduction in HRV, reduced parasympathetic activity, and diminished heartbeat complexity relative to comparison participants. More recent METH use was associated with increased sympathetic tone. Chronic METH exposure may be associated with decreased HRV, impaired vagal function, and reduction in heart rate complexity as assessed by multiple methods of analysis. We discuss and review evidence that impaired HRV may be related to the cardiotoxic or neurotoxic effects of prolonged METH use.

Fractal scaling properties of heart rate dynamics and myocardial efficiency in dilated cardiomyopathy

INTRODUCTION

Since altered heart rate (HR) fluctuations provide prognostic information in heart failure, we examined the associations between HR dynamics, myocardial efficiency and perfusion, among patients with dilated cardiomyopathy.

METHODS

Sixteen patients with dilated cardiomyopathy were enrolled. Patients received supervised strength and aerobic training for 5 months (n = 9) or standard care (n = 7). The short-term scaling exponent (alpha(1)) and frequency domain measures of HR behavior were assessed at baseline and after 5 months of intervention. The left ventricular (LV) function measured using echocardiography and oxidative metabolism measured using positron emission tomography (PET) and [(11)C]-acetate were used to estimate the myocardial efficiency.

RESULTS

Short-term fractal exponent alpha(1) correlated significantly with LV myocardial efficiency (r = 0.77, p = 0.002) at baseline. After the intervention period, the majority of patients showed improved myocardial efficiency and small or marked change in HR dynamics toward the natural fractal-like organization (alpha(1) value close 1). Parallel change in fractal properties of HR and myocardial efficiency after intervention was observed in 78% of the patients. Intervention had no significant effect on any other HR fluctuation indices.

CONCLUSIONS

The present study suggests that short-term fractal scaling exponent alpha(1), an important prognostic marker in heart failure, is related to LV myocardial efficiency.

Standard Deviation of normal interbeat intervals as a risk marker in patients with left ventricular systolic dysfunction: a meta-analysis

Our aim was to evaluate the Standard Deviation of Normal-Normal (SDNN) interbeat interval as a risk marker in left ventricular systolic dysfunction (LVSD) patients through a meta-analysis. We searched PubMed for studies that evaluated SDNN as a predictor of all-cause-death, cardiac death, transplantation, and progressive clinical deterioration using a search strategy validated for MEDLINE. Mean values and SD for SDNN in sixteen studies included were 115+/-48 ms in survivors versus 87+/-40 ms in non-survivors, resulting in a statistically significant standardized mean difference (0.594, 95%CI 0.385 to 0.803). In conclusion, SDNN may be a useful prognostic marker in LVSD. Additional studies must evaluate if SDNN may be used to subsidize therapeutic decisions.

Role of electrophysiologic study (EPS)-guided preventive therapy for the management of ventricular tachyarrhythmias in patients with heart failure

BACKGROUND

Ventricular tachyarrhythmias (VT/VF) are 1 of the most important factors determining the prognosis of patients with heart failure (HF). Although priority is given to implantable cardioverter defibrillator (ICD) therapy for the prevention of sudden cardiac death, electrophysiologic-study (EPS)-guided preventive therapy could be important for reducing the number of cardiac events.

METHODS AND RESULTS

Of 864 patients with a history of HF, an EPS was performed in 168 and 121 had inducible VT/VF. Under the basic therapy of an ICD, additional catheter ablation was attempted for 95 of 124 monomorphic VT foci in 74 patients, and 78 of the VT were successfully ablated. The prognoses were compared among 5 patient groups with different results for the EPS and catheter ablation: (1) success group (n=43), (2) failure group (n=15), (3) not attempted group (n=16), (4) VF group (n=47), and (5) no inducible VT/VF group. During a follow-up period of 31+/-22 months, the incidence of VT/VF was lower in the success and no inducible VT/VF groups than in the other groups (p=0.0018), although a significant difference was not observed for the total deaths.

CONCLUSION

EPS-guided preventive therapy using an ICD and catheter ablation can be useful, at least for the reduction of arrhythmic events in patients with HF.

Orthopaedic surgeons' cardiovascular response during total hip arthroplasty

The literature contains limited and contradictory information regarding the amount of physical effort and/or emotional stress needed to perform surgery. We therefore investigated cardiovascular response to psychophysical stress in orthopaedic surgeons while they were performing surgery. We monitored 29 male orthopaedic surgeons from four university centers while they performed total hip arthroplasties. Changes in their cardiovascular parameters were recorded by ambulatory monitoring methods. Exercise stress testing of each participant was used as a control state. We compared the cardiovascular response during surgery to energy requirements of everyday activities. Preoperative and postoperative testing showed lower values of cardiovascular parameters than during physically less difficult parts of the operation; physically more difficult phases of the operation additionally increased the values of parameters. We concluded performing total hip arthroplasty increases surgeons' cardiovascular parameters because of psychologic stress and physical effort. Excitement of the cardiovascular system during total hip arthroplasty appears similar to the excitement during moderate-intensity daily activities, such as walking the dog, leisurely bicycling, or climbing stairs.

EFFECT OF BENAZEPRIL ON HEART RATE TURBULENCE IN PATIENTS WITH DILATED CARDIOMYOPATHY

1. Heart rate (HR) turbulence describes short-term sinus rhythmic fluctuation after a single premature ventricular beat. Turbulence onset (TO) and turbulence slope (TS) are two essential parameters in HR turbulence. Turbulence onset and TS have been used to evaluate cardiac autonomic nerve function. 2. In the present study, we measured the HR turbulence in dilated cardiomyopathy (DCM) and determined the possible role of benazepril, an angiotensin-converting enzyme inhibitor (ACEI), on these parameters. There were three groups: control, DCM and DCM treated with benazepril. The control group consisted of normal subjects with PVB, but no structural heart disease. Ambulatory electrocardiogram, blood pressure and echocardiography were analysed. 3. There was an increase in TO and a decrease in TS in DCM patients. Benazepril treatment (10 mg/day, p.o.) reduced those changes. There were no significant differences in blood pressure and left ventricular ejection fraction (LVEF) between DCM patients and DCM patients treated with benazepril. 4. Linear regression analysis showed that TO was negatively correlated with LVEF, whereas TS was positively correlated with LVEF, in the DCM group. After benazepril treatment, the correlations between TO and TS and LVEF disappeared. 5. It is concluded that the TO and TS of HR turbulence are altered in patients with DCM. These alterations indicate a dysfunction of the autonomic control of cardiac electrophysiology in DCM patients. Although TO and TS are correlated with LVEF in DCM patients, the effect of benazepril in improving HR turbulence parameters is not a result of its action on heart function, which suggests a new beneficial effect of ACEI in the treatment of DCM patients.

Changes of autonomic information flow due to idiopathic dilated cardiomyopathy

Risk stratification of patients with idiopathic dilated cardiomyopathy (IDC) is an epidemiologically relevant question. But the results based on conventional heart rate variability (HRV) analysis are still unsatisfactory. The adjustments within the cardiovascular system incorporate nonlinear and complex mechanisms of information exchange which may have additional prognostic value. It is an objective of the present work to evaluate the prognostic value of autonomic information flow (AIF) measures in IDC patients compared to conventional HRV measures in a first explorative study. Holter recordings of 32 patients with idiopathic dilated cardiomyopathy (IDC) and 12 normal subjects (NRM) were analyzed. The IDC patients consisted of two groups: 10 high risk (HR) patients, after aborted sudden cardiac death (SCD); 22 low risk (LR) patients, without SCD. Sensitivity, specificity, positive predictive value, negative predictive value and ROC characteristics of a comprehensive set of AIF measures, organized according to the conventional HRV standards, and conventional HRV measures were investigated. The significant risk predictors were evaluated by Spearman's rank correlation. While the only traditional HRV measure discriminating IDC patients from NRM was ln(LF) most of the AIF measures had a discriminatory value. Concerning the prognosis of the IDC patients by conventional HRV we found that SDNN and all frequency band measures (lnHF, lnLF, lnVLF) significantly discriminated HR from LR. Among the AIF measures the time shift related peak decay (PD(dHF)) reflecting the HF band information flow had a prognostic value. PD(dHF) was identified as a promising candidate which might improve the predictive value of traditional HRV analysis, predominantly represented by SDNN. A subsequent comprehensive clinical study is necessary to validate this hypothesis.

Effects of concentrated ambient particles on heart rate variability in spontaneously hypertensive rats

In the present study, the cardiovascular toxicity of PM(2.5) was determined in spontaneously hypertensive (SH) rats using the standard deviation of normal-to-normal intervals (SDNN) and root mean square of successive differences of adjacent normal-to-normal intervals (RMSSD) as outcome measurements. Four SH rats implanted with radiotelemetry transmitters were repeatedly exposed to concentrated PM(2.5) in nose-only exposure chambers. Gravimetric analysis revealed the mean post-concentrating mass concentration of particles during the 5 h of exposure was 202 mug/m(3). Using each animal as its own control and linear mixed-effects model, to adjust for circadian nature and individual differences, we found that SDNN decreased by 15% initially then gradually decreased to 60% of the initial value at the end of exposure. Our results indicate that concentrated PM(2.5) may decrease SDNN on SH rats during PM exposure. The study also showed that SDNN is more sensitive to PM induced effects than RMSSD.

Comparison of the short-term effects of salmeterol and formoterol on heart rate variability in adult asthmatic patients

STUDY OBJECTIVES

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.

PATIENTS

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.

METHODS

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.

RESULTS

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.

CONCLUSION

Salmeterol and formoterol have no short-term adverse effects on HRV.

Heart rate variability in adult patients with isolated left ventricular noncompaction

BACKGROUND

Isolated left venticular noncompaction (IVNC) is a rare congenital heart disease charactrized by a pattern of an excessively prominent trabecular meshwork with deep intertrabecular recesses. Heart rate variability (HRV) has been reported to be impaired in various heart diseases, though little is known regarding HRV in adult patients with IVNC.

METHODS

We measured spectral components of HRV using fast Fourier transformation of 24-h Holter recordings in 10 adult patients with IVNC, 40 patients with myocardial infarction (MI), 40 patients with hypertrophic cardiomyopathy (HCM) and 40 healthy controls.

RESULTS

The low frequency component and the high frequency component of HRV were lower in IVNC patients tahn those in controls (265 +/- 213 ms(2) vs. 469 +/- 195 ms(2), p < 0.01; 80 +/- 51 ms(2) vs. 185 +/- 126 ms(2), p < 0.01). Furthermore, 3 IVNC patients with a previous history of heart failure exhibited more decreased HRV (low frequency, 75 +/- 56 ms(2); high frequency, 39 +/- 18 ms(2)). Contrary, the ratio of low frequency to high frequency component was higher in patients with IVNC than controls (3.5+/-0.5 vs. 3.2 +/- 0.3, p < 0.05). The degree of impaired HRV was severest in MI patients, intermediate in IVNC patients and mildest in HCM patients compared with controls.

CONCLUSIONS

HRV is impaired in adult patients with IVCN, especially in patients with a previous history of heart failure, suggesting vagal withdrawal or sympathetic enhancement. HRV in IVNC adults is less impaired than in MI patients, and more impaired than in HCM patients of our cohort.