Establishing an accurate arrhythmia diagnosis

Many arrhythmias are asymptomatic, and even symptomatic patients may grossly underestimate the frequency and duration of arrhythmic episodes. The conventional medical history, clinical examination, routine electrocardiogram, and routine rhythm strip are inadequate for the detection of transient arrhythmias. Holter electrocardiography is the only currently available clinically documented technique for diagnosing transient arrhythmias. A wide selection of Holter equipment is now available, providing recorders and scanners with different performance characteristics. Portable ECG telephone transmitters and alarms are not Holter recorders, and they will probably have a different clinical application. The emerging concept of quantitative Holter electrocardiography will permit better selection of patients for drug therapy and provide a rational basis for therapeutic follow-up.     

Arrhythmias during halothane anaesthesia II: the influence of atropine

The effect of i.v. atropine premedication on cardiac rhythm was studied in healthy adult patients during thiopental-N2O/O2-halothane anesthesia without intubation. A higher incidnece of arrhythmias was seen in younger patients in close relation to administration of atropine, but the overall incidence during anesthesia was identical in atropine groups and the control groups. The most common arrhythmias were supraventricular ectopies. None of the ECG irregularities led to serious arrhythmias. No consistent changes in blood pressure were observed as the result of arrhythmias or changes in heart rate. It is concluded that atropine should be reserved for situations where severe bradycardia and hypotension occur, or can be expected to occur, and not given automatically, since cardioacceleration which is inherent in its action may be injurious to patients with limited cardiac reserve.     

Artifacts and pitfalls in MR imaging of the orbit: a clinical review

High-resolution magnetic resonance (MR) imaging of the orbit has become widely accepted as a valuable diagnostic technique. However, there are a number of artifacts and pitfalls associated with orbital MR imaging. Chemical shift artifacts may be induced by orbital fat or silicone oil used to treat retinal detachment. Motion artifacts are caused primarily by unavoidable globe motion during imaging. Artifacts due to a nonuniform magnetic field are particularly noticeable at air-tissue interfaces but may also be caused by incomplete fat saturation or highly magnetic materials near the orbit. Protocol errors may cause artifacts such as saturation, phase wraparound, truncation, shading, and partial-volume artifacts. This information can be used to improve orbital image quality and avoid misinterpretation of image artifacts. Use of fat saturation, silicone saturation, and careful patient screening for metal near the eyes and instruction to reduce motion can help reduce the occurrence of artifacts. In addition, optimal imaging technique is essential and should include use of proper surface coils, plane of section, and pulse sequences.     

Cardiopulmonary complications in acute subarachnoid hemorrhage

Pathologic electrocardiogram (ECG) may be present in more than 90% of patients with subarachnoid haemorrhage. The ECG findings are often transient and may mimic acute myocardial ischaemia or infarction. These ECG findings may cause diagnostic problems in patients with subarachnoid haemorrhage who are unconscious or who have atypical symptoms. Life-threatening arrhythmias are also seen and may be responsible for sudden deaths in patients with subarachnoid haemorrhage. Other signs of myocardial injury, such as ventricular wall motion dysfunction, elevated enzymes, and histological evidence of contraction band necrosis are described. The myocardial dysfunction known as neurogenic stunned myocardium is reversible if the patient survives the acute phase, but it may lead to haemodynamic instability and contribute to the origin of neurogenic pulmonary oedema. The myocardial injury in subarachnoid haemorrhage may be due to a massive sympathetic stimulation of the myocardium in response to rapidly increasing intracranial pressure. We illustrate myocardial injury and dysfunction in a case report where a patient had subarachnoid haemorrhage with ventricular fibrillation, pulmonary oedema, left ventricular dysfunction and ST-segment elevation, initially thought to be acute myocardial infarction.     

Cardiology: prolapsed mitral valve syndrome

A patient with the prolapsed mitral valve syndrome may have no symptoms referable to the heart or, at the other extreme, may have disabling chest pain, severe arrhythmias, and electrocardiographic abnormalities. The syndrome is characterized by a midsystolic click and a late systolic murmur. The mechanism responsible for the valve deformity appears to be related to myxomatous degeneration. Associated ECG abnormalities strongly suggest myocardial disease. The diagnoses is established by echocardiography or cineangiocardiography.     

Spectral analysis of periodic fluctuations in electrocardiographic repolarization

Repolarization alternans (RPA) indicates alternate-beat fluctuations in the temporal or spatial characteristics of the echocardiogram (ECG) STU segment which may represent dispersion in repolarization. Spectral decomposition has revealed microvolt-level RPA which has been found to correlate with ventricular tachycardia (VT) and fibrillation, and is increasingly being used for clinical risk stratification. However, while interruptions in periodicity are known to affect spectral decomposition, their quantitative impact on RPA and its clinical utility have been poorly described. We therefore studied the effect of variable alignment, extrasystoles, dissimilar beats and beat exclusion on RPA magnitude in simulations and on the sensitivity and specificity of RPA for VT in a pilot clinical study. RPA magnitude was exquisitely sensitive to QRS alignment such that +/- 1 ms random beat misalignment reduced it by 68% in simulations. Correspondingly, suboptimal QRS alignment in clinical ECG's caused the sensitivity of RPA for inducible VT to fall from 93% to as low as 63%; while JT alignment was also less effective for RPA recovery. As an experiment in minimizing morphometric irregularities in clinical ECG's, we found that RPA magnitude actually fell when replacing either measurably dissimilar or ectopic beats with more representative beats. In addition, inserting or deleting beats also reduced RPA magnitude in clinical sequences and simulations. These statistical analyses suggest that the precision of beat alignment and interruptions to ECG periodicity, which may occur physiologically, may greatly reduce the clinical utility of RPA for VT. Dynamic alterations in RPA in response to sequence irregularities require further study before RPA may be optimally applied to screen for ventricular arrhythmias.     

Arrhythmias in women

Implications for nurses caring for women with arrhythmias include maintaining close monitoring of the QTc interval when administering antiarrhythmic agents and frequent evaluation of patients on antihypertensive drugs, diuretics, and digoxin. Continuous ST segment monitoring should be implemented in female patients after MI. Nurses should serve as a patient advocate for appropriately timed aggressive therapy for the management of CAD or MI in women, comparable to that which would be offered to male patients in a similar clinical situation. ECG monitoring of pregnant patients is imperative if a history of arrhythmias or prolonged QTc is known or even suspected. Numerous research studies have been performed to evaluate the effects, dangers, complications, and contributing factors for cardiac arrhythmias in men and women. Few studies, however, have focused primarily on women in this area. Occasionally, studies may contain small secondary statements about gender differences, but in-depth research regarding arrhythmias if women is lacking. Furthermore, research findings vary among authors and often present conflicting information. Further studies are needed to evaluate the role of heart disease and arrhythmias in women and to determine if therapies for arrhythmias should be gender specific.     

Cardiac disease in intracerebral hematomas

INTRODUCTION AND OBJECTIVE: The Central Nervous System (CNS) plays an essential role in the regulation of the cardiac function. There is strong evidence that many CNS lesions, mainly those of hemorrhagic origin, may induce repolarization abnormalities and enlargement of the QT interval (ECG changes) and several types of arrhythmias. In some cases these changes have been related to sudden death. The imbalance between the sympathetic and parasympathetic systems, favoring the former, seems to be the etiopathogenic factor. MATERIAL AND METHODS: We have carried out a study on thirty-two in-patients suffering from non-severe intracerebral hemorrhage, by means of a Holter ECG examination within the first 72 hours and a second record after two months. We have assessed any significative differences on the ECG findings in relation to the location of the hematoma (left or right hemispheres) and the presence of a personal history of arterial hypertension and/or heart disease. RESULTS: One or more ECG changes were present in 69.2% of the patients and 73% showed one or more rhythm abnormalities. There was a higher incidence of supraventricular arrhythmias associated with the right hemisphere hematomas, with an statistical significance for the atrial extrasystolia. No differences were found between the group with a previous history of hypertension and/or heart disease and the one without these conditions. There were two cases of sudden death, both with left hemisphere hematomas, and in one of them the previous rhythm abnormalities were recorded. CONCLUSIONS: This study corroborates the hypothesis that right hemispheric hematomas induce supraventricular arrhythmias more frequently. The possible association between severe ventricular arrhythmias and sudden death with left-hemisferic hematomas should be studied in a higher number of patients. We recommend monitoring every acute case of intracerebral hematoma when possible.     

Cardiovascular causes of exercise intolerance

Exercise intolerance, due to cardiovascular disease in horses, may be caused by cardiac arrhythmias, valvular regurgitation, congenital abnormalities, myocardial dysfunction, pericardial disease, and vascular thrombosis. The most common cardiovascular cause of exercise intolerance in horses is atrial fibrillation. Cardiovascular abnormalities such as cardiac arrhythmias or murmurs, however, are common in athletic horses and are not always associated with exercise intolerance. Use of an electrocardiography (during rest and exercise) and echocardiography may be necessary to better determine the significance of the cardiovascular abnormality.     

Bilateral stress-fracture of the calcaneal tubercle

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disease in which muscle tissue has been partially replaced by adipose or fibro-adipose tissue. Morphologic changes in the right ventricle and ventricular arrhythmias are characteristic. Pathomorphological changes should be confirmed by NMR or endomyocardial biopsy. Morphological changes ought to be found by ultrasound methods or angiographic examination. ECG exercise test, Holter monitoring, late potentials, total ventricular activation time and programmed stimulation of right ventricle are used to evaluate the risk of sudden death due to ventricular arrhythmias which is the most important problem. Those methods indicate pharmacologic or invasive therapy (RF ablation, implanted cardioverter-defibrillators), and are used to establish the effectiveness of treatment.     

Spectral analysis of electrocardiogram signals of the isolated guinea pig heart for the detection of arrhythmias

Fast Fourier Transform analysis of the electrocardiogram (ECG) signal of the isolated guinea pig heart has been used to investigate the subtle ECG changes that precede cardiac arrhythmias. During prolonged periods of regular contractile activity, spectral analysis of the isolated guinea pig heart ECG revealed that the major frequency components were evenly distributed over the range 0-64 Hz. Prior to arrhythmias or during ischaemia however, there was a major reduction in the amplitude of the higher frequency components. Thus, Fast Fourier Transform analysis of an ECG record enables the detection of the subtle ECG configuration changes that precede cardiac rhythm disturbances. The potential application of this technique for the prediction of cardiac arrhythmias is discussed.     

Aneurysm of the splenic artery

Electrocardiographic abnormalities had been reported, in patients with subarachnoid hemorrhage, with variable percentage from 2% to 91%, according to several studies. The most common changes are T wave inversion, ST segment elevation or depression, QT prolongation, U waves, atrial flutter and fibrillation, ventricular fibrillation, supraventricular tachycardia, premature atrial and ventricular contractions. These findings occur within the first forty-eight hours after the onset of the symptoms; they usually are benign and transient. In a small percentage of cases generally in severe ESA, the ECG changes are associated with ventricular asynergy, coronary vasospasm or subendocardic necrosis. The arrhythmias could be produced either by autonomic discharges to the heart, during increased sympathetic activity due to ESA, or by a damage of cerebral areas with arrhythmogenic capacity. The importance of ECG abnormalities towards mortality and morbidity in patients with ESA has not yet been cleared; however, a careful monitoring is recommended to prevent severe cardiac complications and to obtain an indirect, further evaluation of the neurologic pathology.     

基于一维卷积特征与手工特征融合的集成超限学习机心跳分类方法

融合手工特征和深度特征,提出了一种集成超限学习机心跳分类方法。手工提取的特征明确地表征了心电信号的特定特性,如相邻心跳时间间隔反映了心跳信号的时域特性,小波系数反映了心跳信号的时频特性。同时设计了一维卷积神经网络对心跳信号特征进行自动提取。基于超限学习机（Extreme leaning machine,ELM）,将上述特征融合进行心跳分类。由于ELM初始参数的随机给定可能导致其性能不稳定,进一步提出了一种基于袋装（Bagging）策略的多个ELM集成方法,使分类结果更加稳定且模型泛化能力更强。利用麻省理工心律失常公开数据集对所提方法进行了验证,分类准确率达到了99.02%,实验结果也表明基于融合特征的分类准确率高于基于单独特征的分类准确率。      

New trends in ECG Holter monitoring

The authors review contemporary possibilities of Holter ECG monitoring. In the first group of patients they emphasize possibilities and the yield of long-term ambulatory ECG monitoring by means of an apparatus started by the patient. The second group of patients was examined by Holter monitoring, using an oesophageal lead. It is a method hitherto not used in the Czech Republic, which if properly indicated, improves the non-invasive diagnosis of cardiac arrhythmias.     

Effect of visual cues, vital signs, and protocols on triage: a prospective randomized crossover trial

The purpose of this study is to review published data regarding gender differences in cardiac electrophysiology and in the occurrence of clinical arrhythmias. ECG differences between men and women include a faster resting heart rate in women, a longer corrected QT interval, and a lower QT dispersion than in men. The faster resting heart rate in women appears to be primarily related to differences in physical conditioning. The mechanism for the longer corrected QT interval in women is not completely known, but does not appear to be related to acute effects of estrogen or progesterone or differences in autonomic innervation. Women also appear to have a lower incidence of atrial fibrillation, a difference in the age distribution of supraventricular tachycardia, and a lower incidence of sudden death than men. Much of the lower incidence of sudden death in women may relate to a difference in the prevalence of coronary artery disease, but other factors such as inherent differences in repolarization, which may be reflected by a gender difference in the corrected QT interval, also may be operative. The paradox of a longer corrected QT interval and higher incidence of torsades de pointes, but lower population-based incidence of sudden death in women, has not been completely resolved. Further studies will be required to help better understand the basic mechanisms involved in gender differences in electrophysiology and arrhythmias and determine the extent to which these differences have implications for clinical management of cardiac arrhythmias.     

Transesophageal pacing and recording

Identification of P wave is essential for the diagnosis of various arrhythmias. The transesophageal ECG is useful for obtaining the relationship of atrial-ventricular activation when P wave is difficult to recognize on the surface ECG. Transesophageal pacing is also helpful to evaluate the function of the conduction system and to clarify the mechanism of arrhythmias. Thus, transesophageal pacing and recording can be used as beside electrophysiologic studies in patients with sick sinus syndrome, atrial-ventricular block, atrial flutter, and paroxysmal supraventricular tachycardia.     

Investigation of palpitations

The uncomfortable awareness of a beating heart--palpitations--is a common complaint that can occur under normal or abnormal circumstances. For example, normal palpitations occur with exercise, emotions, and stress, or after taking substances that increase adrenergic tone or diminish vagal activity (coffee, nicotine, and adrenergic or anticholinergic drugs). Normal palpitations are recognised as such because individuals who experience them realise or are told that something happened to accelerate the normal rhythm of the heart. However, some people find sinus tachycardia troublesome enough to seek medical attention. In other situations palpitations are clearly abnormal. The heart beat which is felt for no apparent reason, may be fast, or strong and slow, or feel like a missed or extra beat. Although these abnormal palpitations usually point to a cardiac arrhythmia, this is not always the case. Moreover, many patients with arrhythmias do not have palpitations but manifestations such as syncope, shock, and chest pain (sudden death is also possible). We will discuss the approach to the patient who seeks medical attention because of a history of palpitations, with special emphasis on the history, physical examination, and 12-lead electrocardiogram (ECG) because they are simple and inexpensive diagnostic tools that are available to most physicians.     

Should survivors of myocardial infarction with low ejection fraction be routinely referred to arrhythmia specialists?

Because survivors of myocardial infarction are at risk for ventricular arrhythmias and sudden death, physicians must decide whether to refer these patients to specialists for arrhythmia assessment and therapy. However, this decision is complex as few randomized data are available concerning either diagnostic or therapeutic options. Therefore, we modeled the potential impact of current arrhythmia detection and management strategies on mortality in survivors of myocardial infarction with reduced left ventricular function who are managed in a contemporary manner. Based on recent data we estimated that the mortality for myocardial infarction survivors with left ventricular ejection fraction less than 0.40 is 20 percent over 3.5 years and that half of the deaths are sudden. The sensitivity and specificity of a Holter electrocardiogram (ECG), a signal-averaged ECG, and an invasive electrophysiology study for predicting sudden death were obtained from a literature review of trials published after 1990 that included more than 300 patients. A series of models were constructed to predict mortality achieved by different arrhythmia management strategies that reduced sudden death by 50 percent and 75 percent--reductions estimated to be within the range for amiodarone and implantable defibrillators. We found that, when routinely applied to all infarct survivors with depressed ventricular function, a therapy that reduces sudden death by 50 percent with 1 percent fatal adverse effects (potentially amiodarone) saves approximately 1 life for every 25 patients treated. Therapy that reduces sudden death by 75 percent with 2 percent fatal adverse effects (potentially implantable defibrillators) saves 1 life for every 14 patients treated. Using Holter ECG recordings, a signal-averaged ECG, or an invasive electrophysiology study to select higher-risk groups, 1 life can be saved for every 4 to 11 patients treated, and the negative impact of adverse effects can be reduced. However, to achieve this benefit, additional and potentially invasive arrhythmia testing must be applied to 28 to 47 patients for each life saved. Thus, with contemporary management of acute myocardial infarction, the risk of sudden death for survivors is sufficiently low that broad application of available antiarrhythmic therapies has limited potential for further improving survival, particularly if therapy also has significant adverse effects. Thus, routine referral to arrhythmia specialists is not warranted for the majority of infarct survivors and should be largely reserved for patients with serious, symptomatic arrhythmias.     

Mesosystolic click syndrome and arrhythmia

On 24-hour ambulatory ECG, 17 patients with mitral valve prolapse displayed more frequent and serious arrhythmias than a control group of 17. Neither resting ECG, treadmill ECG, nor other external recordings were capable of predicting which of the patients were prone to development of arrhythmias.     

Survival and incidence of myocardial infarction in men with ambulatory ECG-detected frequent and complex ventricular arrhythmias. 10 year follow-up of the 'Men born 1914' study in Malm?, Sweden

AIM: To assess to what extent do frequent or complex ventricular arrhythmias, detected during 24 h ambulatory electrocardiographic recording (ECG), influence prognosis with regard to survival and incidence of ischaemic heart disease. METHODS AND RESULTS: The study subjects were the 456 randomly selected men born in 1914, the population-based cohort study of 1982-83, in Malm?, Sweden. The main outcome measures were total mortality and incidence of cardiac event (myocardial infarction and death from ischaemic heart disease). Frequent or complex ventricular arrhythmias (Lown classes 2-5) were detected in 49% of the men with (n = 77), and in 35% of those without, a history of myocardial infarction or angina pectoris at baseline, P = 0.019. Independent of clinically evident coronary artery disease at baseline, and after adjustment for traditional atherosclerotic risk factors and use of digitalis or beta-blocker therapy, frequent or complex ventricular arrhythmias were associated with an increased mortality from ischaemic heart disease (relative risk (RR), 2.1; 95% confidence interval (CI), 1.2-3.9) and an increased cardiac event rate (RR, 1.6; 95% CI, 1.0-2.5)). Men free from both ischaemic-type ST depression and frequent or complex ventricular arrhythmias (used as the control group) had the lowest ischaemic heart disease death rate, 5.9 per 1000 person-years. The combination of ST depression and frequent or complex ventricular arrhythmias was associated with an ischaemic heart disease death rate of 20.9 per 1000 person-years. The cardiac event rate in these two groups was 15.6 and 76.1 per 1000 person-years, respectively (adjusted RR, 2.3; CI, 1.1-4.6). CONCLUSIONS: In elderly men without a history of myocardial infarction and angina pectoris, frequent or complex ventricular arrhythmias during ambulatory ECG recording is associated with an increased incidence of myocardial infarction and mortality. Men who, during ambulatory ECG recording, also demonstrate ST-segment depression have an even less favourable prognosis.