Long-term Electrocardiographic Recordings Research Articles

La fibrillation atriale à l'Hôpital Principal de Dakar au Sénégal : résultats et limites de la prise en charge

ObjectivesThe aim of the study was to determine the prevalence of AF in the cardiology department of the Hospital Principal of Dakar, then to evaluate the clinical, paraclinical, etiological and evolutionary profiles of AF and finally to identify the limits of its management in our context. Patients and methodsThis was a retrospective, descriptive, analytical, mono-centric study carried out at Hospital Principal of Dakar from January 2019 to August 2021. Were included, all patients admitted for atrial fibrillation, or patients who presented an atrial fibrillation during hospitalization, confirmed by electrocardiogram or long-term electrocardiographic recording during the study period. ResultsThe prevalence of atrial fibrillation during the period of our study compared to the hospital population was 7.71%, with a sex ratio of 1.03. The mean age was 67.88 ± 14.09 years. We noted that 83.64% of patients had at least one cardiovascular risk factor, with 56.36% suffering from hypertension, 50.91% of sedentary person and 23.64% of diabetics. Clinically, 92.72% of the patients were symptomatic, with dyspnea predominating (70.91%). Cardiac arrhythmia was present in 85.45% of patients, and congestive heart failure in 47.27%. Long-term electrocardiographic recording was performed in 10 patients, showing 50% of paroxysmal atrial fibrillation. Sixty-three patients (57.27%) had permanent AF, twenty-three patients (20.91%) had persistent AF, fourteen patients (12.73%) had long-term persistent AF and ten patients (9.09%) had paroxysmal AF. Transthoracic echocardiography showed 57.27% of left atrial dilatation and 72.3% of reduced left ventricular ejection fraction. Etiologies for cardiac causes were dominated by dilated cardiomyopathy (21.82%), followed by ischemic heart disease (17.27%). In terms of treatment, the most commonly used molecule was bisoprolol (38.18%), followed by digoxin (21.81%). Anticoagulants were used in 85.46% of cases. Acenocoumarol alone was used in 69.09% of patients. Drug-induced cardioversion was attempted in 2 patients without success, and 4 patients benefited from external electric shock with 3 successes. Most patients had a favorable outcome, but 34.54% suffered hemodynamic complications (18.18%) and thromboembolic ones as well (16.36%). In-hospital mortality in our series was 20%. It was significantly related to heart failure, with a left ventricular ejection fraction < 35% (p < 0.001). ConclusionAtrial fibrillation is serious because of its hemodynamic, thromboembolic and rhythmic complications. The high mortality is explained by the underlying condition, but also by the delay in management with late diagnosis and, above all, the unavailability of ablation procedures in our context.

Adaptive bradycardia assessment in preterm infants

In preterm infants, bradycardias associate to critical health conditions. Standard algorithm for bradycardia identification assumes baseline heart rate (BHR) equal to 150bpm and identifies bradycardias when heart rate (HR) decreases below 100bpm. Since preterm infants show BHR varying from 120bpm to 160bpm, a new adaptive algorithm for real-time bradycardia identification was presented. The adaptive algorithm continuously adjusts BHR by averaging HR over the preceding 10-minute window after eliminating out-of-range HR values, and identifies bradycardias when HR decreases below 67% of BHR. Both standard and adaptive algorithms were evaluated using long-term (20.3–70.3h) electrocardiographic recordings of ten preterm infants ("Preterm Infant Cardio-respiratory Signals" database by Physionet). Bradycardias were characterized in terms of rate (BR, h−1) and depth (BD, bpm). Being also indexes of infants’ health conditions, gestational age at birth (GA, days), birth weight (BW, kg) and HR were used to evaluate performances of the algorithms. Association between BR and BD vs GA, BW and HR was evaluated by computation of the correlation coefficient (ρ). Overall, standard and adaptive algorithms identified 516 and 546 bradycardias, respectively; median BR and BD values were comparable (1.25h−1 and 76bpm vs 1.26h−1 and 70bpm, respectively). However, the adaptive algorithm provided higher BD for HR>150bpm, and vice versa. Significant (p value<0.05) correlations were found between BR and HR (ρ=0.69), BR and BW (ρ=−0.76), and BR and HR (ρ=0.76) only when using the adaptive algorithm. Thus, the adaptive algorithm is superior to the standard algorithm and represents a potentially clinically useful tool for real-time bradycardia assessment in preterm infants.

External Cardiac Loop Recorders: Functionalities, Diagnostic Efficacy, Challenges and Opportunities.

According to the World Health Organization's (WHO) report of 2016, cardiovascular diseases (CVDs) accounted for mortality of an estimated 17.9 million people globally. Of these deaths, 85% were due to myocardial infarction and stroke. Further, the pre-dominant atrial fibrillation (AF) arrhythmia has been the most suspected underlying cause of transient ischemic attack or stroke. Thus, the etiologies of early symptoms like syncope and palpitations in patients needs to be evaluated by employing proper diagnostic tests to make early treatment decisions. The most widely referred 24 to 48 hour Holter electrocardiographic (ECG) monitoring tests have not been proved to be much effective in recognizing infrequent intermittent arrhythmic episodes. These drawbacks have led to the development of long-term ambulatory ECG (AECG) monitoring devices. This review reports the state-of-the-art existing AECG monitoring devices and their role of long-term ECG recording in patients suspected with cardiac syncope and palpitations to understand the underlying arrhythmic cause, as well as in the diagnosis and management of AF. Primarily, the utility and diagnostic yield of external cardiac recorders or event loop recorders (ELRs) in capturing the symptom-rhythm correlation which constitutes a clinically useful recordings of heart's electrical activity during infrequent arrhythmic conditions was critically reviewed. Furthermore, a brief case study on challenges involved in clinical data acquisition at a cardiac care unit using ambulatory external monitoring device has been presented. Finally, improvements in design engineering and algorithmic developments to enhance the diagnostic yield and usability of ELRs in clinical settings have been proposed.

The yield of long-term electrocardiographic recordings in refractory focal epilepsy.

ObjectiveTo determine the incidence of clinically relevant arrhythmias in refractory focal epilepsy and to assess the potential of postictal arrhythmias as risk markers for sudden unexpected death in epilepsy (SUDEP).MethodsWe recruited people with refractory focal epilepsy without signs of ictal asystole and who had at least one focal seizure per month and implanted a loop recorder with 2‐year follow‐up. The devices automatically record arrhythmias. Subjects and caregivers were instructed to make additional peri‐ictal recordings. Clinically relevant arrhythmias were defined as asystole ≥ 6 seconds; atrial fibrillation < 55 beats per minute (bpm), or > 200 bpm and duration > 30 seconds; persistent sinus bradycardia < 40 bpm while awake; and second‐ or third‐degree atrioventricular block and ventricular tachycardia/fibrillation. We performed 12‐lead electrocardiography (ECG) and tilt table testing to identify non–seizure‐related causes of asystole.ResultsWe included 49 people and accumulated 1060 months of monitoring. A total of 16 474 seizures were reported, of which 4679 were captured on ECG. No clinically relevant arrhythmias were identified. Three people had a total of 18 short‐lasting (<6 seconds) periods of asystole, resulting in an incidence of 2.91 events per 1000 patient‐months. None of these coincided with a reported seizure; one was explained by micturition syncope. Other non–clinically relevant arrhythmias included paroxysmal atrial fibrillation (n = 2), supraventricular tachycardia (n = 1), and sinus tachycardia with a right bundle branch block configuration (n = 1).SignificanceWe found no clinically relevant arrhythmias in people with refractory focal epilepsy during long‐term follow‐up. The absence of postictal arrhythmias does not support the use of loop recorders in people at high SUDEP risk.

Focal epileptic seizures anticipation based on patterns of heart rate variability parameters

Background and ObjectiveHeart rate variability parameters are studied by the research community as potential valuable indices for seizure detection and anticipation. This paper investigates heart activity abnormalities during focal epileptic seizures in childhood. MethodsSeizures affect both the sympathetic and parasympathetic system which is expressed as abnormal patterns of heart rate variability (HRV) parameters. In the present study, a clinical dataset containing 42 focal seizures in long-term electrocardiographic (ECG) recordings from drug-resistant pediatric epileptic patients (with age 8.2 ± 4.3 years) was analyzed. ResultsResults indicate that the time domain HRV parameters (heart rate, SDNN, standard deviation of heart rate, upper envelope) and spectral HRV parameters (LF/HF, normalized HF, normalized LF, total power) are significantly affected during ictal periods. The HRV features were ranked in terms of their relevance and efficacy to discriminate non-ictal/ictal periods and the top-ranked features were selected using the minimum Redundancy Maximum Relevance algorithm for further analysis. Then, a personalized anticipation algorithm based on multiple regression was introduced providing an “epileptic index” of imminent seizures. The performance of the system resulted in anticipation accuracy of 77.1% and an anticipation time of 21.8 s. ConclusionsThe results of this analysis could permit the anticipation of focal seizures only using electrocardiographic signals and the implementation of seizure anticipation strategies for a range of real-life clinical applications.

Effect of uterine contractions on fetal heart rate in pregnancy: a prospective observational study.

The new Holter monitoring technology enables long-term electrocardiographic recording of the fetal heart rate without discomfort for the mother. The aim of the study was to assess the feasibility of a fetal Holter monitor. This technology was further used to study fetal heart rate outside the hospital setting during normal daily activities and to test the hypothesis that uterine activity during pregnancy influences fetal heart rate. Prospective observational study including 12 healthy pregnant women at 20-40weeks of gestation. Data were collected using the Monica AN24 system. Outcome measures were fetal heart rate, maternal heart rate, and uterine activity categorized according to the strength of the electrohysterographic signal. The recordings had a median length of 18.8h, and fetal heart rate and maternal heart rate were obtained with success rates of 73.1 and 99.9%, respectively. Uterine activity was found to affect fetal heart rate in all participants. Compared with the basal tone and mild levels of uterine activity, moderate and strong levels of uterine activity were associated with increases in fetal heart rate of 4.0 and 5.7beats/min, respectively. At night, the corresponding increases were 4.9 and 7.6beats/min. Linear correlations were found between maternal heart rate and fetal heart rate in 11 of the 12 cases, with a mean coefficient beta of 0.189. Both maternal heart rate and fetal heart rate exhibitedadiurnal pattern, with lower heart rates being recorded at night. Uterine activity during pregnancy is associated with a graded response in fetal heart rate and may represent a physiological challenge for the development and adaptation of the fetal cardiovascular system.

Ventricular tachycardias in patients with pulmonary hypertension: an underestimated prevalence? A prospective clinical study.

Sudden cardiac death (SCD) accounts for approximately 30 % in patients with pulmonary arterial hypertension (PAH). The exact circumference for SCD in this patient population is still unclear. Malignant cardiac arrhythmias are reported to be rarely present. There are no systematic data concerning long-term electrocardiographic (ECG) recording in patients with PAH. We sought to investigate the rate of potentially relevant arrhythmias in patients with pulmonary hypertension (PH). Consecutive patients without diagnosis of known cardiac arrhythmias followed in our outpatient clinic for PH were enrolled in the study. All patients underwent a 72-h Holter ECG. Clinical data, 6-min walk distance, laboratory values, and echocardiography were collected/performed. Ninety-two consecutive patients (New York Heart Association class (NYHA) III/IV: 65.2 %/5.4 %, PH Group 1: 35.9 %, Group 3: 10.9 %, Group 4: 28.3 %, Group 5: 2.2 %) were investigated. Relevant arrhythmias were newly detected in 17 patients: non-sustained ventricular tachycardia (n = 12), intermittent second-degree heart block (n = 1), intermittent third-degree heart block (n= 3), and atrial flutter (n = 1). Echocardiographic systolic pulmonary pressure and diameter of the right heart were elevated in patients with relevant arrhythmias. Right heart catheterization revealed higher pulmonary vascular resistance (672 vs. 542 dyn · s · cm(-5), p = 0.247) and lower cardiac index (2.46 vs. 2.82 l/min/m(2), p = 0.184). Ventricular tachycardias occur more often in PH patients than previously reported. However, the prognostic relevance of non-sustained ventricular tachycardias in this cohort remains unclear. As a large number of PH patients die from SCD, closer monitoring, e.g., using implantable event recorders, might be useful to identify patients at high risk.

Abstract MP07: Increased Risk of Death in Individuals with Premature Atrial, but not Premature Ventricular Contractions on Screening Electrocardiogram

Introduction: Premature atrial contractions (PACs) and premature ventricular contractions (PVCs) detected by long-term electrocardiographic recording have been found to be a marker of increased cardiovascular risk. However, the prognostic significance of PACs and PVCs detected by routine 12-lead screening electrocardiogram (ECG) is not well-established. Methods: We investigated the association between PACs and PVCs detected by a single 12-lead ECG with the risks of death from any cause, cardiovascular (CVD) disease, and ischemic heart disease (IHD) in a nationally representative, community-dwelling cohort of 7642 individuals enrolled in the Third Health and Nutrition Examination Survey (NHANES III). Individuals with known coronary artery disease, congestive heart failure, paced rhythms, and atrial fibrillation were excluded. Results: Mean age was 60 (± 14) years, 53% were women, 24% were non-Hispanic black, and 23% were Hispanics. PACs were detected in 94 (1.2%) participants while PVCs were detected in 114 (1.5%). Over a follow up period of up to 18 years, the death rates per 1000 person-years were 97, 40, and 21 for all-cause, CVD, and IHD deaths, respectively. In a demographic adjusted model, presence of PACs was associated with 50%, 78% and 151% increased risk of all-cause death, CVD death, and IHD death, respectively. After further adjustment for CVD risk factors, ECG abnormalities, concomitant comorbidities and potential confounders, these risks remained significantly high (Table). For PVCs, however, no significant associations with any type of deaths in any model were detected. Conclusion: PACs, but not PVCs, on routine screening ECG are predictive of adverse events in community-dwelling individuals without known heart disease. Given the low cost and widespread use of 12-lead ECG, these findings warrant further investigation into mechanisms and interventions.

ECG Signal Acquisition with on Chip Compression Algorithm

In this paper ECG signal acquisition and compression of the ECG signal is presented. ECG is an electronic method of recording the heart beat of the patient. The characteristic of heart beat is determined by PQRST curve. The detection of QRS complexes in an ECG signal provides information about the heart rate. This paper includes all the details about how to get the proper ECG signal and how it can be compressed. The paper presents an Electrocardiographic (ECG) signal front-end amplifier or pre-amplification of ECG for further processing. The signal conditioning contains amplification and filtering. Compression is required for the fast transmission of ECG signal over wireless network and to reduce the amount of data storage in long-term ECG recording. A new algorithm named Partition Algorithm is proposed for ECG signal compression and reconstruction which involves the partitioning of input signal into eight digital threshold levels which are further reconstructed. Also, it is proved that eight threshold levels are sufficient for providing the necessary ECG information in digital format.

Role of editing of R–R intervals in the analysis of heart rate variability

This paper reviews the methods used for editing of the R–R interval time series and how this editing can influence the results of heart rate (HR) variability analyses. Measurement of HR variability from short and long-term electrocardiographic (ECG) recordings is a non-invasive method for evaluating cardiac autonomic regulation. HR variability provides information about the sympathetic-parasympathetic autonomic balance. One important clinical application is the measurement of HR variability in patients suffering from acute myocardial infarction. However, HR variability signals extracted from R–R interval time series from ambulatory ECG recordings often contain different amounts of artifact. These false beats can be either of physiological or technical origin. For instance, technical artifact may result from poorly fastened electrodes or be due to motion of the subject. Ectopic beats and atrial fibrillation are examples of physiological artifact. Since ectopic and other false beats are common in the R–R interval time series, they complicate the reliable analysis of HR variability sometimes making it impossible. In conjunction with the increased usage of HR variability analyses, several studies have confirmed the need for different approaches for handling false beats present in the R–R interval time series. The editing process for the R–R interval time series has become an integral part of these analyses. However, the published literature does not contain detailed reviews of editing methods and their impact on HR variability analyses. Several different editing and HR variability signal pre-processing methods have been introduced and tested for the artifact correction. There are several approaches available, i.e., use of methods involving deletion, interpolation or filtering systems. However, these editing methods can have different effects on HR variability measures. The effects of editing are dependent on the study setting, editing method, parameters used to assess HR variability, type of study population, and the length of R–R interval time series. The purpose of this paper is to summarize these pre-processing methods for HR variability signal, focusing especially on the editing of the R–R interval time series.

Arrhythmic Manifestations in Patients With Congenital Left Ventricular Aneurysms and Diverticula

Congenital left ventricular aneurysms and diverticula (LVA/Ds) are rare cardiac malformations that can be detected using echocardiography or other imaging techniques. Some of these patients present with ventricular arrhythmias. This study investigated clinical characteristics of patients with congenital LVA/D presenting with arrhythmic manifestations. Over the previous 20 years 250 patients were diagnosed to have congenital LVA/D at our institution. Diagnosis was made using echocardiography after exclusion of coronary artery disease, local cardiac inflammatory processes, traumatic causes, or cardiomyopathies. At initial presentation 32 of the 250 patients (13%, average age 45 years, range 25 to 65, 21 men and 11 women) exhibited arrhythmias. At least 2 LVA/Ds were present in 6 of these patients. LVA/Ds were localized at the posterobasal, apical, anteroseptal, and anterolateral walls in 12, 11, 4, and 5 patients, respectively. The most common complaints at presentation were syncope or presyncope in 18 patients and palpitations in 11 patients. One patient had survived sudden cardiac death. Long-term electrocardiographic recordings showed ventricular tachycardia (VT) or ventricular fibrillation in 17 patients (53%). Twelve patients underwent electrophysiologic testing. Nine patients had inducible ventricular tachyarrhythmia, whereas induced tachycardia was similar to that during spontaneous arrhythmia in 7 patients. In conclusion, patients with congenital LVA/Ds who present with arrhythmic manifestations commonly have VT. Electrophysiologic testing can reproduce clinical VT in most of these patients.

Asymptomatic rhythm and conduction abnormalities in children with acute rheumatic fever: 24-hour electrocardiography study

Some rhythm and conduction abnormalities can occur in children with acute rheumatic fever. These abnormalities have been defined based on standard electrocardiography; however, the real prevalence of these abnormalities has not been investigated previously by the evaluation of long-term electrocardiographic recordings. In this study, we evaluated the asymptomatic rhythm and conduction abnormalities in children with acute rheumatic fever by evaluating the 24-hour electrocardiography. We evaluated the standard electrocardiography and the 24-hour electrocardiography of 64 children with acute rheumatic fever. On standard electrocardiography, the frequency of the first-degree atrioventricular block was found to be 21.9%. Electrocardiography at 24 hours detected three additional and separate patients with a long PR interval. Mobitz type I block and atypical Wenckebach periodicity were determined in one patient (1.56%) on 24-hour electrocardiography. While accelerated junctional rhythm was detected in three patients on standard electrocardiography, it was present in nine patients according to 24-hour electrocardiography. Premature contractions were present in 1.7% of standard electrocardiography, but in 29.7% of 24-hour electrocardiography. Absence of carditis was found to be related to the presence of accelerated junctional rhythm (p > 0.05), and the presence of carditis was found to be related to the presence of premature contractions (p = 0.000). In conclusion, our results suggest that in children with acute rheumatic fever, the prevalence of rhythm and conduction abnormalities may be much higher than determined on standard electrocardiography. Further studies are needed to clarify whether or not these abnormalities are specific to acute rheumatic fever.

The electrocardiographic holter monitoring in experimental veterinary practice

The long-term electrocardiographic recording with retrospective evaluation (Holter system) has been widely used not only in cardiology, but also in other disciplines of internal medicine and in pharmaceutical research. The Holter system can be used in mini-pig, sheep, dog, cat, rabbit, ferret, and rat. In this paper hardware, software, and anesthesia requirements are summarized with respect to the experimental work with various species. As the Holter systems work in bipolar mode, the use of bipolar leads in sagittal and transversal planes has been proved to be the most appropriate because of large amplitude of QRS complex and uncomplicated consequent automatic analysis of the record. In conclusion, Holter electrocardiography represents a simple and applicable method for monitoring the electrical activity of the heart in small animals' experimental studies.

Altered diurnal autonomic variation and reduced vagal information flow in acute schizophrenia

Objective This study aimed to further investigate autonomic function in schizophrenic patients using long-term electrocardiographic (ECG) recordings. Methods Twenty unmedicated patients suffering from an acute episode of paranoid schizophrenia and 20 matched control subjects were recruited and 24-h ambulatory electrocardiograms were recorded. In order to investigate complexity of heart rate fluctuations related to different physiological time scales, linear heart rate variability (HRV) as well as autonomic information flow (AIF) parameters were calculated from day and night time intervals. Results While heart rates were increased, root mean successive square difference (RMSSD), a measure for vagal function as well as standard deviation of 5-min mean NN-intervals (SDANN), reflecting parasympathetic and sympathetic tone, were decreased in schizophrenia. Furthermore, a decrease of vagal information flow was apparent during night time (decreased mean high frequency peak decay (PD mHF)). In addition, increased INT NN (area under the AIF curve) as well as decreased beat decay (BD NN) and mean very low frequency PD (PD mVLF) indicated reduced complexity in patients during day and night time. Conclusions HRV and AIF parameters indicate altered diurnal autonomic variation in schizophrenia. Significance Reduced vagal modulation and loss of complexity might both contribute to the increased risk for sudden cardiac death in schizophrenia.

Parasympathetic dysfunction in hypertrophic cardiomyopathy assessed by heart rate variability: comparison between short‐term and 24‐h measurements

In this study, we evaluate cardiac autonomic function in hypertrophic cardiomyopathy (HCM) by assessing heart rate variability (HRV), comparing a short-term laboratory method with an ambulatory (24-h) method, in patients with and without beta-blockade. Reduced HRV is a risk factor for adverse events in some cardiac diseases, but is not a proven risk indicator in HCM. Analysis of HRV has been based on either short- or long-term electrocardiographic recordings and previous studies in HCM have shown conflicting results. There is no consensus on which method to prefer, and we evaluate, for the first time, both short- and long-term analyses in patients with HCM. Long- and short-term HRV analyses were performed in 43 patients with HCM. They were divided in two groups, 22 patients on beta-blockade and 21 non-treated patients. As controls, 121 healthy subjects were used. Young patients without beta-blockade showed a reduction in HRV parameters reflecting parasympathetic function, both in the short- and long-term registrations, which was attenuated by beta-blockade. Parasympathetic autonomic regulation was found to be impaired in young patients with HCM. This may be of clinical relevance as abnormal autonomic function might be a substrate for malignant dysrhythmias. The impairment was attenuated by beta-blockade, which might indicate a clinically useful effect. We also show that short- and long-term methods yield similar results, suggesting that a short-term registration might be sufficient to assess HRV in patients with HCM.

Fractal correlation properties of heart rate dynamics and adverse events in patients with implantable cardioverter-defibrillators

The aim of this study was to determine the prognostic significance of nonlinear and standard heart rate (HR) variability parameters in predicting future adverse events (AEs) in patients with implantable cardioverter-defibrillators. In postinfarction studies, nonlinear measures of HR variability obtained from long-term electrocardiographic recordings have been suggested to be better predictors of adverse outcomes than conventional HR variability measures. Fifty-five high-risk patients with reduced left ventricular function and an implantable cardioverter-defibrillator had a 10-minute, high-resolution electrocardiographic recording after which they were followed for 25 months on average. Implantable cardioverter-defibrillator shock or death was determined as the end point. The SD of all normal-to-normal RR intervals, the square root of the mean squared differences of successive normal-to-normal RR intervals, and the proportion of interval differences of successive normal-to-normal RR intervals >50 ms, low-frequency and high-frequency powers of the power spectrum and their ratio were calculated as conventional measures of HR variability. The short-term scaling exponent (α 1) and approximate entropy were determined as nonlinear measures of HR variability. AEs occurred in 23 patients (42%). Patients with AEs had significantly lower α 1 than event-free patients: 0.81 ± 0.29 (mean ± SD) versus 1.01 ± 0.30 (p = 0.02). None of the other HR variability parameters differed significantly between patients with and without AEs. In the Cox proportional-hazards model including age, gender, ejection fraction, occurrence of ventricular tachyarrhythmia before defibrillator implantation, β-blocker usage, and α 1, only α 1 was an independent predictor of AEs: hazard ratio 1.20 (95% confidence interval 1.03 to 1.39) for every 0.10 decrease in α 1 (p = 0.020). In conclusion, α 1 obtained from a 10-minute electrocardiographic recording yields important prognostic information about the risk of AEs in patients with implantable cardioverter-defibrillators.

Abnormal heart rate variability as a manifestation of autonomic dysfunction in hemispheric brain infarction.

Abnormal heart rate variability is related to prognostically unfavorable ventricular arrhythmias and sudden arrhythmic death in coronary artery disease. Short-term electrocardiographic (ECG) recordings have shown similar abnormalities of heart rate variability in patients with acute stroke. However, there is no information regarding the clinical significance of these abnormalities and of heart rate variability in long-term ECG recordings in stroke. In this prospective study, we analyzed the time domain and frequency domain measures of heart rate variability from 24-hour ECG recordings in 31 consecutive patients with hemispheric brain infarction in the acute phase and at 1 and 6 months after the infarction and in 31 age- and sex-matched healthy control subjects. All the measured components of heart rate variability, ie, standard deviation of RR intervals (P < .001), total power (P < .0001), very-low-frequency power (P < .0001), low-frequency power (P < .001), and high-frequency power (P < .05), were significantly lower than those of the control subjects in both the acute phase and 1 and 6 months later. Impaired heart rate variability correlated with the severity of neurological deficits and disability. In five patients with increased intracranial pressure due to large brain infarction, no relevant spectral components were found. Hemispheric brain infarction seems to cause significant long-lasting damage to the cardiovascular autonomic regulatory system manifested as abnormalities of heart rate variability. Distorted heart rate variability in the acute phase of stroke may be prognostically unfavorable.

Hypertension and ST segment depression during ambulatory electrocardiographic recording. Results from the prospective population study 'men born in 1914' from Malmö, Sweden.

The aim of this study in 341 men (aged 68 years) without history of ischemic heart disease was to study the relation between hypertension and silent ischemic-type ST segment depression during ambulatory long-term electrocardiographic recording and to assess the influence between these two variables on cardiovascular morbidity and mortality rates. Seventy-nine men (23%) demonstrated one or more episodes of silent ischemic ST segment depression. One hundred and sixty-seven men (49%) were considered to have hypertension (i.e., they had a diastolic blood pressure of 95 mm Hg or greater or were treated with antihypertensive therapy). Forty-nine (72%) of the 68 treated hypertensive subjects were classified as uncontrolled (i.e., their diastolic blood pressure was 95 mm Hg or greater). The occurrence of ischemic ST depression was higher in hypertensive men (28%) than in normotensive men (19%). The highest incidence of ischemic ST depression (41%) was observed in treated hypertensive men with inadequate blood pressure control. Cardiac event rate during a 53-month follow-up was 6.6% in hypertensive men and 4.6% in normotensive men. Uncontrolled treated hypertensive men had a higher event rate (14%) than hypertensive men overall. Hypertensive men with inadequate blood pressure control and who demonstrated ST segment depression had the highest event rate (25%).

Distribution patterns of ventricular premature complexes in long-term electrocardiographic recordings and their usefulness in disclosing modulated parasystole

Long-term electrocardiographic recordings from 25 patients with abundant ventricular premature complexes (VPCs) were screened with a computer program for sequences of interectopic intervals with the number of sinus beats consistent with manifest or concealed bigeminy/trigeminy. On average, 19.0% of VPCs in this patient series were followed by an uninterrupted sequence of ≥10 interectopic intervals with concealed bigeminy. The corresponding figure for concealed trigeminy was 2.2%, for manifest bigeminy 9.6%, and for manifest trigeminy 0.8%. The longest sequence with concealed bigeminy comprised 149 interectopic intervals. The corresponding figure for concealed trigeminy was 135 interectopic intervals. The sequences of concealed bigeminy occurred at significantly lower heart rates than those of concealed trigeminy. These findings can be explained by the entrainment phenomena described in experimental models of modulation of a ventricular parasystolic focus across a zone of impaired conduction.

Complex dynamics of cardiac arrhythmias.

In the case of a benign but very active cardiac arrhythmia often observed in healthy subjects, the behavior of the ventricular extrasystoles during long-term electrocardiographic recording was carefully scrutinized using the facilities of complex computerized programs of analysis. The presence or the absence of the extrasystoles, their distribution with respect to the normal beats, their time relationships, and the existence or the absence of a repetitive activity after the initial extrasystole follow complex, interactive rules that essentially depend on two determinants: the cardiac frequency as such (rate-dependence) and the autonomic nervous system (adrenergic dependence). It can be concluded, at variance from the random distribution suggested by a superficial examination, that an in-depth study allows the complex rules conditioning the various types and patterns of extrasystoles to be unearthed. Precise quantitative regularities underly the dynamics, and observing such rules gives the cardiologist hopes that one might distinguish various physiological mechanisms from a careful consideration of the dynamics. Collaboration of cardiologists and nonlinear dynamicists is needed to understand the origin of complex cardiac rhythms and to sort out the roles of chance and determinism in their genesis.