Automatic filtering of outliers in RR intervals before analysis of heart rate variability in Holter recordings: a comparison with carefully edited data

<p>Abstract</p> <p>Background</p> <p>Undetected arrhythmic beats seriously affect the power spectrum of the heart rate variability (HRV). Therefore, the series of RR intervals are normally carefully edited before HRV is analysed, but this is a time consuming procedure when 24-hours recordings are analysed. Alternatively, different methods can be used for automatic removal of arrhythmic beats and artefacts. This study compared common frequency domain indices of HRV when determined from manually edited and automatically filtered RR intervals.</p> <p>Methods and Results</p> <p>Twenty-four hours Holter recordings were available from 140 healthy subjects of age 1-75 years. An experienced technician carefully edited all recordings. Automatic filtering was performed using a recursive procedure where RR intervals were removed if they differed from the mean of the surrounding RR intervals with more than a predetermined limit (ranging from 10% to 50%). The filtering algorithm was evaluated by replacing 1% of the beats with synthesised ectopic beats. Power spectral analysis was performed before and after filtering of both the original edited data and the noisy data set. The results from the analysis using the noisy data were used to define an age-based filtering threshold. The age-based filtration was evaluated with completely unedited data, generated by removing all annotations from the series of RR intervals, and then comparing the resulting HRV indices with those obtained using edited data. The results showed equivalent results after age-based filtration of both the edited and unedited data sets, where the differences in HRV indices obtained by different preprocessing methods were small compared to the mean values within each age group.</p> <p>Conclusions</p> <p>The study showed that it might not be necessary to perform the time-consuming careful editing of all detected heartbeats before HRV is analysed in Holter recordings.</p> <p>In most subjects, it is sufficient to perform the regular editing needed for valid arrhythmia analyses, and then remove undetected ectopic beats and artefacts by age-based filtration of the series of RR intervals, particularly in subjects older than 30 years.</p

Screening for atrial fibrillation with baseline and intermittent ECG recording in an out-of-hospital population

BACKGROUND: the objective of this study is to investigate the detection rate of undiagnosed atrial fibrillation (AF) with short intermittent ECG recordings during four weeks among out-of-hospital patients, having at least one additional risk factor (CHADS(2)) for stroke. METHOD: Design: Cross-sectional study. Setting: Eight family practice centres and two hospital-based out-patient clinics in Sweden. Subjects: 989 out-of-hospital patients, without known AF, having one or more risk factors associated with stroke (CHADS(2)). Interventions: All individuals were asked to perform 10-second handheld ECG recordings during 28 days, twice daily and when having palpitations. Main outcome measures: Episodes of AF on handheld ECG recordings were defined as irregular supraventricular extrasystoles in series with a duration of 10 seconds. RESULTS: 928 patients completed registration. AF was found in 35 of 928 patients; 3.8% (95% confidence interval [CI] 2.7–5.2). These 35 patients had a mean age of 70.7 years (SD ± 7.7; range 53–85) and a median CHADS(2) of 2 (range 1–4). CONCLUSIONS: Intermittent handheld ECG recording over a four week period had a detection rate of 3.8% newly diagnosed AF, in a population of 928 out-of-hospital patients having at least one additional risk factor for stroke. Intermittent handheld ECG registration is a feasible method to detect AF in patients with an increased risk of stroke in whom oral anticoagulation (OAC) treatment is indicated

Cardiac arrhythmias and heart rate variability in familial amyloidotic polyneuropathy : A clinical study before and after liver transplantation

Familial amyloidotic polyneuropathy (FAP), found in the northernmost counties in Sweden, is a rare, lethal and inherited amyloidosis. The disease is caused by mutated transthyretin (TTR). The mutation is characterized by an exchange of valine for methionine at position 30 (ATTRVal30Met). FAP is characterised by progressive polyneuropathy affecting both the peripheral and autonomic nervous system (ANS). Cardiac arrhythmia and autonomic disturbances are common as well as gastrointestinal symptoms: such as constipation and diarrhoea. Today, orthotopic liver transplantation (LTx) is the only treatment to stop the progression of FAP. The rationale for this is because 95% of TTR is synthesized by the liver, a liver transplantation should abolish the production of new mutated amyloidogenic TTR. The first liver transplantation for FAP was performed in Sweden 1990. Heart complications and autonomic disturbances are common in FAP patients both before and after liver transplantation. The aim of the present study was three-fold: to determine whether liver transplantation affects the natural course of cardiac arrhythmias and cardiac autonomic function; to predict the risk of ventricular arrhythmias; and to elucidate heart rate variability (HRV) patterns by power spectrum analysis and Poincaré plots. In total, ninety-seven Swedish FAP patients were included in the studies. The patients underwent 24-hours electrocardiography (Holter) recordings, and/or signal averaged electrocardiography (SAECG) and heart rate variability. The study showed that many patients developed cardiac arrhythmias and conduction disturbances after LTx. Approximately 25 percent of patients were pacemaker treated after LTx. The SAECG recordings disclosed that many FAP patients had ventricular late potentials (LP) compared with healthy subjects, and that LP were associated with nonsustained ventricular arrhythmia. Analyses of heart rate variability (HRV) showed reduced autonomic function in the majority of patients. Some patients had high HRV with broadband power spectra and Poincaré graphs with a fan or complex pattern. These novel findings could be an indicator of ECG abnormalities (subtle atrial arrhythmia) in FAP patients instead of reflecting normal cardiac autonomic modulation. The HRV studies also showed that LTx preserves cardiac autonomic function in FAP. In conclusion, cardiac arrhythmias, late potentials and reduced heart rate variability were common in Swedish patients with FAP, whether they underwent liver transplantation or not. The absence of LP may indicate a low risk for ventricular tachycardia in FAP patients

Screening for atrial fibrillation with baseline and intermittent ECG recording in an out-of-hospital population. BMC Cardiovasc Disord 2013;13:41

This is a published version of a paper published in BMC Cardiovascular Disorders. Citation for the published paper: Hendrikx, T., Hörnsten, R., Rosenqvist, M., Sandström, H. Background: the objective of this study is to investigate the detection rate of undiagnosed atrial fibrillation (AF) with short intermittent ECG recordings during four weeks among out-of-hospital patients, having at least one additional risk factor (CHADS 2 ) for stroke. Method: Design: Cross-sectional study. Setting: Eight family practice centres and two hospital-based out-patient clinics in Sweden. Subjects: 989 out-of-hospital patients, without known AF, having one or more risk factors associated with stroke (CHADS 2 ). Interventions: All individuals were asked to perform 10-second handheld ECG recordings during 28 days, twice daily and when having palpitations. Main outcome measures: Episodes of AF on handheld ECG recordings were defined as irregular supraventricular extrasystoles in series with a duration of 10 seconds

Are ECG changes in heart-healthy individuals of various ages related to cardiac disease 20 years later?

Background: This research study aimed at assessing the electrocardiographic (ECG) changes caused by ageing in a cohort of healthy subjects with normal echocardiographic examinations. Methods: A total of 219 healthy individuals (119 males and 100 females) were evaluated for possible arrhythmias with a standard 12-lead resting ECG and 24-h Holter ECG. As the recordings were performed between 1998 and 2000, a 20-year follow-up study was carried out by assessing the local medical records to investigate whether the subjects had experienced any cardiovascular health complications or disease since the baseline assessment. Results: Eighty-three subjects (45 males and 38 females) presented with pathological ECG findings at baseline. The most common finding on analysis of Holter ECG recordings was premature atrial contractions, and the most severe pathological finding was episodes of ventricular tachycardia (eight subjects). Regarding the analysis of the standard 12-lead ECG, the most common finding was left ventricular hypertrophy, and the most severe pathological findings were ST-T changes and prolongation of the QT interval. Despite other cardiac examinations performed on these patients showing normal results, in combination with a strict inclusion criterion, this study showed that 28% of all subjects had pathological resting 12-lead ECGs at rest and 35% had pathological heart rhythms when assessed by 24-h Holter ECG. At follow-up, 21% of females and 43% of males had presented with ECG abnormalities, and 30% of females and 36% of males had cardiovascular disease. There was hypertension in 45% of females and in 58% of males. However, no association was found between the follow-up findings and ECG changes seen at baseline. Conclusion: Although most ECG changes found at baseline could be considered as a normal variation, they may progress to more severe heart complications as the subject ages. The results of this study also validate ECG findings of previous studies and underline that diagnostic criteria should be based on gender and age

Normal scores of deep breathing tests : beware of dysrhythmia in transthyretin amyloidosis

Background: The heart rate (HR) response to paced deep breathing (DB) is a common test of cardiac autonomic function, where high heart rate variability (HRV) is considered to reflect normal autonomic function. We evaluated the DB test in patients with hereditary transthyretin amyloid (ATTRm) amyloidosis, where autonomic dysregulation and atrial arrhythmias are common.Methods: Paced DB was performed during one minute (six breaths/min) in 165 recordings in adult ATTRm amyloidosis patients with the TTR Val30Met mutation, 42 hypertrophic cardiomyopathy (HCM) patients and 211 healthy subjects. HRV was scored by traditional DB indices and by a novel regularity index, estimating the fraction of the HRV that was coherent with the breathing pattern.Results: Twenty per cent of ATTRm amyloidosis patients presented with age-adjusted HRV scores within normal limits but poor regularity due to subtle atrial arrhythmias and cardiac conduction disturbances. Forty-seven per cent of ATTRm amyloidosis patients presented with HRV scores below normal limits, whereas HCM patients presented with higher HRV than ATTRm amyloidosis patients.Conclusions: Reduced HRV is common in ATTRm amyloidosis patients during DB, however, autonomic function cannot be evaluated in patients presenting with the combination of normal scores and low regularity, since their HR responses often reflects dysrhythmias

New Insights into the clinical evaluation of hereditary transthyretin amyloidosis patients : A single center’s experience

Over the last decade, new medical treatment modalities have emerged based on increased insights into amyloid formation. With the increased possibilities for treatment of amyloidosis caused by transthyretin (TTR) amyloid deposits comes the need for diagnostic procedures for early diagnosis and better tools to follow disease progression. This is of particular importance in clinical trials evaluating the efficacy of new treatments. Until recently, the treatment of TTR amyloidosis (ATTR) was based solely on liver transplantation, a procedure that has halted disease progression in many patients. Liver transplantation has been especially effective in patients under the age of 50 years carrying the TTR V30M mutation, whereas the outcome of the procedure has been variable for others, particularly elderly male patients and those carrying a non-V30M mutation. This review concentrates on new insights derived from our center's experience with liver transplantation, how to implement this experience in evaluation of new treatment modalities for ATTR, and how to facilitate early diagnosis of neuropathy with easily available diagnostic tools. Attention has focused on manifestations of the disease that involve the heart and the peripheral nervous system; change in peripheral nerve function has been the primary endpoint in two controlled clinical trials, one finished and one ongoing. New insights into the amyloid formation process and the lessons learned from liver transplantation give the opportunity to design potentially effective treatment modalities for ATTR. It appears reasonable to suspect that a combination of different treatment modalities may be required to treat the disease, and that different treatment regimes will be designed according to the phenotype of the disease. For the patients and their relatives there is now a solid foundation for optimism, with prospects of several effective medical treatment possibilities within the coming decade

Reduced left atrial myocardial deformation irrespective of cavity size : a potential cause for atrial arrhythmia in hereditary transthyretin amyloidosis

BACKGROUND: Cardiac amyloidosis (CA) is a myocardial disease and commonly under-diagnosed condition. In CA patients, atrial fibrillation might occur in the absence of left atrial (LA) enlargement. OBJECTIVES: The aim of this study is to assess LA size and function, and its relationship with atrial arrhythmia in patients with hereditary transthyretin amyloidosis (ATTR). METHODS: Forty-six patients with confirmed ATTR amyloidosis on abdominal biopsy were studied. Assessment with 2D echocardiography and 2D strain showed 31 patients had increased LV wall thickness (LVWT) (septal thickness &gt;12 mm), and 15 had normal LVWT. In addition to conventional measurements, LV and LA global longitudinal strain (GLS%) and strain rate (SR) were obtained. Western blot analysis was done to assess fibril type. ATTR patients with increased LVWT were compared with 23 patients with hypertrophic cardiomyopathy (HCM) and 31 healthy controls. ATTR amyloidosis patients also underwent 24 hour Holter monitoring to determine the presence of atrial arrhythmia. RESULTS: Atrial deformation during atrial systole was reduced in ATTR amyloidosis patients with increased LVWT independent of LA size and in contrast to HCM. Twenty of the ATTR amyloidosis patients (54%) had ECG evidence of significant atrial arrhythmic events. LA strain rate, during atrial systole, was the only independent predictor of atrial arrhythmia (β = 3.28, p = .012). CONCLUSION: In ATTR cardiomyopathy with increased LVWT, LA myocardial function is abnormal, irrespective of atrial cavity size. Reduced LA myocardial SR during atrial systole, irrespective of cavity volume, E/e' and LV deformation, is also a strong predictor for atrial arrhythmic events

Atrial fibrillation among patients under investigation for suspected obstructive sleep apnea

STUDY OBJECTIVES: Obstructive sleep apnea is common among patients with atrial fibrillation, but the prevalence and risk factors for atrial fibrillation among patients who are being investigated on suspicion of sleep apnea are not well known. The aim of the study was to estimate the prevalence of atrial fibrillation among patients investigated for suspected obstructive sleep apnea and to identify risk factors for atrial fibrillation among them. METHODS: The prevalence of atrial fibrillation was investigated among 201 patients referred for suspected obstructive sleep apnea. Patients without known atrial fibrillation were investigated with a standard 12-lead ECG at hospital and short intermittent handheld ECG recordings at home, during 14 days. RESULTS: Atrial fibrillation occurred in 13 of 201 subjects (6.5%), and in 12 of 61 men aged 60 years and older (20%). The prevalence of atrial fibrillation increased with sleep apnea severity (p = 0.038). All patients with atrial fibrillation were men and all had sleep apnea. Age 60 or older, the occurrence of central sleep apnea and diabetes mellitus were independent risk factors for atrial fibrillation after adjustments for body mass index, gender, sleep apnea and cardiovascular disease. CONCLUSIONS: Atrial fibrillation is common among subjects referred for sleep apnea investigation and the prevalence of atrial fibrillation increases with sleep apnea severity. Independent risk factors for atrial fibrillation among patients investigated for suspected obstructive sleep apnea include the occurrence of coexisting central sleep apnea, age 60 years or older and diabetes mellitus