Prevalence of potential noninvasive arrhythmia risk predictors in healthy, middle-aged persons

Electromuscular incapacitating devices discharge and risk of severe bradycardia

Electromuscular incapacitating devices (EMDs) are high-voltage, low-current stimulators causing involuntary muscle contractions and sensory response. Existing evidence about cardiac effects of EMD remains inconclusive. The aim of our study was to analyze electrocardiographic, echocardiographic, and microvolt T-wave alternans (MTWA) changes induced by EMD discharge.

We examined 26 volunteers (22 men; median age 30 years) who underwent single standard 5-second duration exposure to TASER X26 under continuous echocardiographic and electrocardiographic monitoring. Microvolt T-wave alternans testing was performed at baseline (MTWA-1), as well as immediately and 60 minutes after EMD exposure (MTWA-2 and MTWA-3, respectively).

Mean heart rate (HR) increased significantly from 88 ± 17 beats per minute before to 129 ± 17 beats per minute after exposure (P < 0.001). However, in 2 individuals, an abrupt decrease in HR was observed. In one of them, interval between two consecutive beats increased up to 1.7 seconds during the discharge. New onset of supraventricular premature beats was observed after discharge in 1 patient. Results of MTWA-1, MTWA-2, and MTWA-3 tests were positive in one of the subjects, each time in a different case.

Standard EMD exposure can be associated with a nonuniform reaction of HR and followed by heart rhythm disturbances. New MTWA positivity can reflect either the effect of EMD exposure or a potential false positivity of MTWA assessments.

Microvolt T-wave alternans in patients undergoing elective coronary artery bypass grafting: a pilot study

INTRODUCTION

We designed a prospective observational study targeting a selective population of patients undergoing elective coronary artery bypass grafting with normal systolic function. In this study we looked at the prevalence of pre-operative microvolt T-wave alternans and if it predicts atrial fibrillation after surgery.

METHODS

The inclusion criteria included all patients referred to the cardiothoracic outpatient clinic for elective bypass, who can perform aerobic exercise, with a recent exercise stress test exercising at least to 85% of the maximal predicted heart rate (220 - age) and with non-limiting chest pain at maximal exercise. Twenty patients met the inclusion/exclusion criteria between May 2008 and February 2010. The hospital course of those patients was followed, and in-hospital events were recorded.

RESULTS

Nine out twenty (45%) of patients had a non-negative microvolt T-wave alternans tracing. Six patients (30%) developed new onset atrial fibrillation post surgery. Patients with non-negative microvolt level T-wave alternans are more likely to develop atrial fibrillation post coronary artery bypass grafting then patients with negative microvolt level T-wave alternans (p=0.05).

CONCLUSIONS

This pilot study provides the first clinical evidence that patients with ischemic heart disease and normal systolic function have a high prevalence of abnormal microvolt T-wave alternans and might be at higher risk of sudden cardiac death. In addition our results show that microvolt level T-wave alternans predicts post coronary artery bypass grafting new onset atrial fibrillation.

Safety and tolerability of the novel inhaled corticosteroid fluticasone furoate in combination with the β2 agonist vilanterol administered once daily for 52 weeks in patients >=12 years old with asthma: a randomised trial

Background

The inhaled corticosteroid fluticasone furoate (FF) in combination with the long-acting β₂ agonist vilanterol (VI) is in development for asthma and chronic obstructive pulmonary disease.

Objective

To assess the safety and tolerability of FF/VI over 52 weeks in patients with asthma.

Methods

Patients (aged ≥12 years; on inhaled corticosteroid) were randomised (2:2:1) to FF/VI 100/25 µg or FF/VI 200/25 µg once daily in the evening, or fluticasone propionate (FP) 500 µg twice daily. Safety evaluations included adverse events (AEs), non-fasting glucose, potassium, 24-h urinary cortisol excretion, ophthalmic assessments, heart rate and pulse rate.

Results

On-treatment AEs were similar across groups (FF/VI 66–69%; 73% FP). Oral candidiasis/oropharyngeal candidiasis was more common with FF/VI (6–7%) than FP (3%). Twelve serious AEs were reported; one (worsening hepatitis B on FP) was considered drug related. Statistically significant cortisol suppression was seen with FP compared with both FF/VI groups at Weeks 12 and 28 (ratios [95% CI] to FP ranged from 1.43 [1.11 to 1.84] to 1.67 [1.34 to 2.08]; p≤0.006), but not at Week 52 (ratios to FP were 1.05 [0.83 to 1.33] for FF/VI 100/25 µg and 1.09 [0.87 to 1.38] for FF/VI 200/25 µg). No clinically important changes in non-fasting glucose, potassium, QT interval corrected using Fridericia's formula (QTc[F]) or ophthalmic assessments were reported. Pulse rate (10 min post dose [T_max], Week 52) was significantly increased with FF/VI versus FP (3.4 bpm, 95% CI 1.3 to 5.6; p=0.002 [FF/VI 100/25 µg]; 3.4 bpm, 95% CI 1.2 to 5.6; p=0.003 [FF/VI 200/25 µg]). Mean heart rate (24-h Holter monitoring) decreased from screening values in all groups (0.2–1.1 bpm FF/VI vs 5 bpm FP; Week 52).

Conclusions

FF/VI (100/25 µg or 200/25 µg) administered once daily over 52 weeks was well tolerated by patients aged ≥12 years with asthma. The overall safety profile of FF/VI did not reveal any findings of significant clinical concern.

ClinicalTrials.gov

NCT01018186

Heart rate variability and heart rate turbulence in hypothyroidism before and after treatment

BACKGROUND

Cardiac autonomic dysfunction may develop in patients with clinical or subclinical thyroid hormone deficiency. Heart rate variability (HRV) and heart rate turbulence (HRT) are used for evaluating changes in cardiac autonomic functions and also used to provide risk stratification in cardiac and noncardiac diseases. The aim of this study is to evaluate cardiac autonomic functions before and 6 months after thyroid replacement therapy in patients with thyroid hormone deficiency.

METHODS

Forty hypothyroid patients (mean age 48 ± 13, four male) and 31 healthy controls (mean age 51 ± 12, three male) were included in the study. Twenty-four hour ambulatory electrocardiogram recordings were taken using Pathfinder Software Version V8.255 (Reynolds Medical). The time domain parameters of HRV analysis were performed using the Heart Rate Variability Software (version 4.2.0, Norav Medical Ltd, Israel). HRT parameters, Turbulence Onset (TO), and Turbulence Slope (TS) were calculated with HRT! View Version 0.60-0.1 software.

RESULTS

HRV and HRT parameters were decreased in the patient group (SDNN; P < 0.001, SDANN; P < 0.009, RMSSD; P = 0.049, TO; P = 0.035, TS; P < 0.001). After 6 months of thyroid replacement therapy, there were no significant changes observed in either HRV or HRT.

CONCLUSIONS

Hypothyroidism may cause cardiac autonomic dysfunction. Treating hypothyroidism with L-thyroxine therapy does not effectively restore cardiac autonomic function. HRV and HRT can be used as to help monitor cardiovascular-related risk in this population.

Cardiac autonomic dysfunction in hemodialysis patients: The value of heart rate turbulence

Patients with end-stage renal disease (ESRD) are likely to have cardiac autonomic dysfunction, which is related with an increased risk of sudden death. The aim of this study is to detect cardiac autonomic dysfunction in patients with ESRD and to evaluate the possible acute effects of hemodialysis (HD) on cardiac autonomic functions measured by heart rate variability (HRV) and heart rate turbulence (HRT). Thirty-one (mean age 50 ± 13 years, 15 males) with ESRD on regular HD program and 31 healthy volunteers (mean age 51 ± 12 years, 15 males) were included in the study. Twenty-four-hour ambulatory electrocardiogram recordings were taken from the subjects before and after HD and from the control group. Heart rate variability and HRT parameters were calculated from these recordings. All of the HRV and HRT parameters were found to be significantly blunted in patients in comparison with healthy individuals. There were significant differences in HRV after HD, but similar differences were not observed in HRT parameters. Cardiac autonomic functions were significantly altered in patients with ESRD. Heart rate turbulence parameters seemed to be less affected from HD and may be more useful in the evaluation of cardiac autonomic functions in the ESRD population.

Influence of diabetes and/or myocardial infarction on prevalence of abnormal T-wave alternans

BACKGROUND

Subjects with microvolt-level T-wave alternans (TWA) in association with structural heart disease have an increased risk for sudden cardiac death. The presence of diabetes (DM) is associated with an increased risk of sudden death but there is limited data on the impact of DM and previous myocardial infarction (MI) on TWA prevalence.

METHODS

We performed a case-control cross-sectional study in 140 patients referred for routine exercise testing within a large multispecialty clinic. All patients with a history of DM and MI status within the past year were eligible: group 1 (no DM or MI), group 2 (DM only), group 3 (MI only), group 4 (DM and MI). Patients performed a symptom-limited Bruce protocol exercise test with assessment of TWA by the spectral method using commercially available equipment. We used published criteria for the blinded interpretation of TWA; all tests not unequivocally negative were considered abnormal.

RESULTS

Age and gender were similar in all groups. The prevalence of abnormal TWA in groups 1-4 was 24%, 20%, 48%, and 62%, respectively (between group P = 0.002). Logistic regression analysis in all patients showed that abnormal TWA was related to prior MI [OR (95% CI): 4.0 (1.8-8.9), P < 0.001] but not to prevalent DM [0.9 (0.4-1.8), P = 0.72]. In patients with DM, the prevalence of abnormal TWA was related to reduced ejection fraction (P = 0.034) but not to BMI, DM duration, glycemic control, insulin use, or the presence of microvascular complications.

CONCLUSION

The presence of DM alone does not increase risk of abnormal TWA. Prospective studies are required to establish the prognostic value of TWA in patients with DM.

T-wave alternans: reviewing the clinical performance, understanding limitations, characterizing methodologies

Accurate recognition of individuals at higher immediate risk of sudden cardiac death (SCD) is still an open question. The fortuitous nature of acute cardiovascular events just does not seem to fit the well-known model of ventricular tachycardia/fibrillation induction in a static arrhythmogenic substrate by a synchronous trigger. On the mechanism of SCD, a dynamical electrical instability would better explain the rarity of the simultaneous association of a correct trigger and an appropriate cardiac substrate. Several studies have been conducted trying to measure this cardiac electrical instability (or any valid surrogate) in an ECG beat stream. Among the current possible candidates we can number QT prolongation, QT dispersion, late potentials, T-wave alternans (TWA), and heart rate turbulence. This article reviews the particular role of TWA in the current cardiac risk stratification scenario. TWA findings are still heterogeneous, ranging from very good to nearly null prognostic performance depending on the clinical population observed and clinical protocol in use. To fill the current gaps in the TWA base of knowledge, practitioners, and researchers should better explore the technical features of the several technologies available for TWA evaluation and pay greater attention to the fact that TWA values are responsive to several factors other than medications. Information about the cellular and subcellular mechanisms of TWA is outside the scope of this article, but the reader is referred to some of the good papers available on this topic whenever this extra information could help the understanding of the concepts and facts covered herein.

Outcome of heart rate variability and ventricular late potentials after liver transplantation for familial amyloidotic polyneuropathy

Reduced heart rate variability (HRV) is common in familial amyloidotic polyneuropathy (FAP), as well as cardiac arrhythmias. We examined the effects of liver transplantation (LTx) on 24-h HRV and ventricular late potentials. Twenty-one liver-transplanted FAP patients underwent Holter-ECG recordings and signal average electrocardiography recordings (SAECG) before and after LTx. Mean follow-up time after LTx was 21.7 months. Three patients had marked increased HRV after LTx, but this was in all cases caused by the development of subtle atrial arrhythmia and did not reflect an improvement in the cardiac autonomic control. In total, ten patients were excluded from analysis of HRV because of arrhythmia. Spectral analysis of HRV showed no significant differences before and after LTx in the remaining 11 patients. Positive late potentials were found in 33% of patients before LTx and this proportion was unchanged after LTx. Reduced HRV and positive late potentials are common in Swedish FAP patients, and remain stable, at least within the short term after transplantation. If an increase of HRV after transplantation is observed, it should raise the suspicion that the patient has developed subtle atrial arrhythmia.

Relationship Between Abnormal Microvolt T-Wave Alternans and Poor Glycemic Control in Type 2 Diabetic Patients

BACKGROUND

Abnormal microvolt T-wave alternans (TWA) predicts the risk of ventricular arrhythmias and sudden cardiac death. Although type 2 diabetes is associated with an increased risk of these events, there is a dearth of available data on microvolt TWA measurements in type 2 diabetic populations.

METHODS

We studied 59 consecutive type 2 diabetic outpatients without manifest cardiovascular disease (CVD) and 35 non-diabetic controls who were matched for age, sex, and blood pressure values. Microvolt TWA analysis was performed non-invasively using the CH-2000 system during a sub-maximal exercise with the patient sitting on a bicycle ergometer.

RESULTS

The frequency of abnormal TWA was significantly higher in diabetic patients than in controls (25.4 vs 5.7%; P < 0.01). Among diabetic patients, those with abnormal TWA (n = 15) had remarkably higher hemoglobin A1c (HbA1c) (8.1 +/- 0.9 vs 7.1 +/- 0.8%, P < 0.001) and slightly smaller time-domain heart rate variability parameters (i.e., RMSSD, root mean square of difference of successive R-R intervals) than those with normal TWA (n = 44). Gender, age, body mass index, lipids, blood pressure values, cigarette smoking, diabetes duration, microvascular complication status, QTc interval, and current use of medications did not significantly differ between the groups. In multivariate regression logistic analysis, HbA1c (OR 13.6, 95% CI 2.0-89.1; P = 0.0076) predicted abnormal TWA independent of RMSSD values and other potential confounders.

CONCLUSIONS

Our findings suggest that abnormal TWA is a very common condition (approximately 25%) among people with type 2 diabetes without manifest CVD and is closely correlated to glycemic control.

Effects of synthetic progestagens on autonomic tone, neurohormones and C-reactive protein levels in young healthy females in reproductive age

BACKGROUND

Heart rate variability and baroreceptor sensitivity are measures of autonomic control. While progestagen-containing replacement therapy in postmenopausal women adversely affects autonomic balance, the impact of hormonal contraceptives with synthetic progestagens on autonomic activity, neurohormones and C-reactive protein levels is not well characterized.

METHODS AND RESULTS

We analyzed parameters of heart rate variability and baroreceptor sensitivity in young healthy females without (n = 27) or on oral contraceptives with synthetic progestagens (n = 31). Demographic characteristics were not different among the examined groups. Total power (controls: 5682+/-3618 vs. hormones: 4800+/-2957 ms2; NS), standard deviation of beat-to-beat intervals (SDNN; 66+/-24 vs. 63+/-20 ms; p = 0.74), other time- and frequency-dependent parameters of heart rate variability and baroreceptor sensitivity (6.0+/-3.2 vs. 6.5+/-2.7 ms/mm Hg; NS) were not significantly different among the groups. Total cholesterol and triglyceride as well as C-reactive protein (CRP) levels were significantly higher in users of hormonal contraceptives than in non-users (cholesterol: 187+/-37 vs. 166+/-28 mg/dL; p = 0.05; triglycerides: 110+/-35 vs. 68+/-30 mg/dL; p = 0.01; CRP: 2.7+/-2.1 vs. 1.0+/-1.4 mg/L; p < 0.001). Heart rate variability, baroreceptor sensitivity, lipid parameters and CRP levels were not affected during the ovarian cycle in non-users of hormonal contraception.

CONCLUSIONS

The use of oral contraceptives containing synthetic progestagens was not associated with a modulation of autonomic tone, while lipid parameters and CRP levels were adversely affected. These data suggest that synthetic progestagens in modern oral contraceptives do not modulate the autonomic balance, but probably affect the atherogenic risk profile of young females in reproductive age.

Measurement of microvolt T-wave alternans, a new arrhythmic risk stratification test, in Type 2 diabetic patients without clinical cardiovascular disease

AIMS

Patients with a positive microvolt T-wave alternans (TWA) are at increased risk of ventricular arrhythmias and sudden cardiac death. Although Type 2 diabetes is associated with an increased risk of these events, there is a dearth of available data on measurements of TWA in people with Type 2 diabetes.

METHODS

We studied 43 Type 2 diabetic volunteers who were free of diagnosed cardiovascular disease (CVD). Microvolt TWA analysis was performed non-invasively using the CH 2000 system during submaximal exercise with the patients sitting on a bicycle ergometer.

RESULTS

TWA analysis was positive in 9 (21%) patients, negative in 32 (74.4%) and indeterminate in 2 (4.6%) subjects. TWA positive patients had significantly higher HbA(1c) levels than those with TWA negativity (8.1 +/- 0.9 vs. 7.2 +/- 0.8%, P < 0.01). Age, sex, BMI, blood pressure, lipids, 24-h heart rate variability, QTc interval duration, smoking history, diabetes duration and treatment, and microvascular complication status did not differ between the groups. In regression logistic analysis, HbA(1c) was the only significant predictor of TWA positivity (odds ratio 5.7, 95% CI 1.3-26, P = 0.023) after controlling for potential confounders.

CONCLUSIONS

These results suggest that in Type 2 diabetic patients without clinically manifest CVD, TWA positivity is common (approximately 20%) and is closely correlated with glycaemic control.

Ventricular late potentials in familial amyloidotic polyneuropathy

We investigated the occurrence of ventricular late potentials (LPs) in patients with familial amyloidotic polyneuropathy (FAP) and the possible association with ventricular arrhythmia on Holter electrocardiography and echocardiographic data. Fifty-five patients and 94 healthy controls were studied. LP were found in 46% of the FAP patients older than 60 years and in 15% of the controls (P = .02), whereas no difference was found in individuals younger than 60 years. The occurrence of LP was associated with nonsustained ventricular arrhythmia in the older FAP patients (P = .04). Older patients with LP had increased ventricular septum thickness (P = .02) and left posterior wall thickness (P = .01), as compared with those without LP. In conclusion, ventricular LPs are common in the FAP patients older than 60 years and associated with nonsustained ventricular arrhythmia and increased thickness of the left ventricular wall. Long-term follow-up studies are required to find the prognostic significance of these new findings.

Microvolt T-Wave Alternans for the Risk Stratification of Ventricular Tachyarrhythmic Events

OBJECTIVES

The objective of this study was to perform a meta-analysis of the predictive value of microvolt T-wave alternans (MTWA) testing for arrhythmic events in a wide variety of populations.

BACKGROUND

Previous studies describing the use of MTWA as a predictor of ventricular tachyarrhythmic events have been limited by small sample sizes and disparate populations.

METHODS

Prospective studies of the predictive value of exercise-induced MTWA published between January 1990 and December 2004 were retrieved. Data from each article were abstracted independently by two authors using a standardized protocol. Summary estimates of the predictive value of MTWA were made using a random-effects model.

RESULTS

Data were accumulated from 19 studies (2,608 subjects) across a wide range of populations. Overall, the positive predictive value of MTWA for arrhythmic events was 19.3% at an average of 21 months' follow-up (95% confidence interval [CI] 17.7% to 21.0%), the negative predictive value was 97.2% (95% CI 96.5% to 97.9%), and the univariate relative risk of an arrhythmic event was 3.77 (95% CI 2.39 to 5.95). There was no difference in predictive value between ischemic and nonischemic heart failure subgroups. The positive predictive value varied depending on the population of patients studied (p < 0.0001).

CONCLUSIONS

Microvolt T-wave alternans testing has significant value for the prediction of ventricular tachyarrhythmic events; however, there are significant limitations to its use. The predictive value of MTWA varies significantly depending on the population studied. Careful standardization is needed for what constitutes abnormal MTWA. The incremental prognostic value of MTWA when used with other methods of risk stratification is unclear.

Heart rate turbulence following ventricular premature beats in healthy controls

BACKGROUND

Heart rate turbulence (HRT) has recently been described as a strong, independent risk stratifier in postinfarct patients. To date, however, the incidence of false positive HRT findings in adults is unknown. Therefore, we performed a blinded, retrospective analysis of HRT in a prospectively collected database of 110 apparently healthy persons to determine the prevalence and clinical significance of abnormal HRT findings in healthy controls using previously published cut-off values.

METHODS AND RESULTS

The study included 43 out of 110 apparently healthy adults, in whom a sufficient number of ventricular premature beats were available for HRT analysis on 24-hour Holter recordings. The HRT slope was dichotomized at 2.5 ms per R-R interval and HRT onset was dichotomized at 0% using previously established criteria to define an abnormal HRT analysis in postinfarct patients. Using these definitions, abnormal HRT results were found in 2 out of 43 controls (5%) for HRT slope and in 8 out of 43 controls (19%) for HRT onset without any cardiac deaths during 32 +/- 15 months follow-up.

CONCLUSIONS

The incidence of false positive HRT results in healthy middle-aged volunteers is low for HRT slope (5%), but not for HRT onset (19%) when previously published cut-off values are used to define abnormal HRT results. Thus, HRT slope dichotomized at 2.5 ms per R-R interval, but not HRT onset dichotomized at 0%, may be used as a relatively specific tool for risk stratification in middle-aged persons.