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PubMedDate not supplied

A wide, complex look at cardiac dysrhythmias.

The diagnosis and treatment of cardiac dysrhythmias answers the following four questions: Is the patient stable? Is the rate fast or slow? Are the ventricular complexes wide or narrow? Is the rhythm regular or irregular? The most common narrow complex regular tachycardias are sinus tachycardia, atrial flutter, atrial tachycardia that blocks, and paroxysmal supraventricular tachycardia. Carotid sinus massage is useful in differentiation. Irregular narrow-complex tachycardias are usually atrial fibrillation. An ultra-rapid wide-complex or polymorphous irregular tachycardia is likely to be atrial fibrillation with ventricular preexcitation. Wide-complex regular tachycardias present a special challenge, since wide beats may result from supraventricular or ventricular impulse formation. Ventricular tachycardia is more likely than supraventricular tachycardia in the presence of underlying ischemic heart disease, atrioventricular dissociation, fusion or capture beats, or a very broad (greater than .14 seconds) QRS complex. Still, misdiagnosis is common; the most costly mistake is over-diagnosis of SVT. In emergencies, where vital organ hypoperfusion is present, the origin of the impulse and the name of the dysrhythmia are unimportant. With the exception of sinus tachycardia, all life-threatening, rapid tachycardias should be terminated by electrical cardioversion.

Anti-Arrhythmia Agents↗
PubMed2004

The value of the electrocardiogram and chest X-ray for confirming or refuting a suspected diagnosis of heart failure in the community.

BACKGROUND: There is a common assumption that a normal ECG or a normal heart size on chest X-ray virtually rules out a diagnosis of heart failure. AIMS: To assess the value of the electrocardiogram and chest X-ray in identifying patients with chronic heart failure in the community. METHODS AND RESULTS: This study was a secondary analysis of data prospectively collected at the time of patient's enrollment in the EPICA study, an epidemiological study of the prevalence of heart failure in Portugal. A total of 6300 subjects were clinically evaluated. Patients who presented with symptoms or signs of heart failure, and/or were receiving diuretics for chronic heart failure (CHF) had a chest X-ray, ECG, and echocardiogram. The diagnosis of heart failure was confirmed in 551 cases. Patients with right atrial enlargement, atrial flutter, atrial fibrillation, 2nd degree-Mobitz I atrioventricular block, 1st degree atrioventricular block, left bundle branch block, lung interstitial oedema, and bilateral pleural effusion were more likely to be diagnosed with heart failure. For the diagnosis of heart failure, in the Portuguese population aged over 25 years, an abnormal electrocardiogram had an estimated sensitivity of 81%, and negative predictive value of 75%; an abnormal chest X-ray had an estimated sensitivity of 57%, and negative predictive value of 83%. Twenty five percent of patients with CHF had a normal ECG or chest X-ray. CONCLUSION: Our results show that electrocardiographic and roentgenographic features are not sufficient to allow heart failure to be reliably predicted in the community and support the recommendation that all patients with suspected heart failure should undergo echocardiography.

Adult↗
PubMed2004

Influence of age and gender on the mechanism of supraventricular tachycardia.

OBJECTIVES: The objective of this study was to determine the impact of age and gender on the mechanism of paroxysmal supraventricular tachycardia (PSVT). BACKGROUND: Previous studies have indicated that PSVT mechanism may be influenced by age and gender, but contemporary data are limited. METHODS: In 1,754 patients undergoing catheter ablation of 1,856 PSVTs between 1991 and 2003, the mechanism was classified as atrioventricular reentrant tachycardia (AVRT), atrioventricular nodal reentrant tachycardia (AVNRT), or atrial tachycardia (AT). Patients with inappropriate sinus tachycardia, atrial flutter, atrial fibrillation, and age <5 years were excluded. RESULTS: The mean age was 45 +/- 19 years (range 5-96), and the majority were women (62%). Overall, AVNRT was the predominant mechanism (n = 1,042 [56%]), followed by AVRT (n = 500 [27%]) and AT (n = 315 [17%]). There was a strong relationship between age and PSVT mechanism; the proportion of AVRT in both sexes decreased with age, whereas AVNRT and AT increased (PM < .001 by ANOVA). The majority of patients with AVRT were men (273/500 [54.6%]), whereas the majority of patients with AVNRT and AT were women (727/1,042 [70%] and 195/315 [62%], respectively). The distribution of PSVT mechanism was significantly influenced by gender (P < .001). In women, 63% had AVNRT, 20% had AVRT, and 17.0% had AT. In men, 45% had AVNRT, 39% had AVRT, and 17% had AT. AVNRT replaced AVRT as the dominant PSVT mechanism at age 40 in men and at age 10 in women. CONCLUSIONS: The mechanism of PSVT in patients presenting for ablation is significantly influenced by both age and gender.

Accelerated Idioventricular Rhythm↗
PubMed2006

Cardiac arrhythmias in the fetus and newborn.

Arrhythmias are potentially life-threatening problems in the fetus and newborn. Appropriate management depends on accurate diagnosis. Atrioventricular re-entry is the most common type of supraventricular tachycardia in both the fetus and newborn. It should be distinguished from other types of tachycardia - such as atrial flutter, atrial ectopic tachycardia, permanent junctional re-entry tachycardia, and ventricular tachycardia. Neonatal and fetal bradycardias are less common clinical problems. Sustained bradycardia is most often caused by complete atrioventricular block. It can be mimicked by the more common but benign occurrence of non-conducted atrial premature beats.

Anti-Arrhythmia Agents↗
PubMed1994

Sensitivity and specificity of a dual-chamber arrhythmia recognition algorithm for implantable devices.

Present ventricular rate-based arrhythmia detection algorithms lack specificity. Using a training set of 109 endocardial electrogram recordings, a sensitive and specific dual-chamber arrhythmia recognition algorithm has been developed. The algorithm uses atrial and ventricular rates, irregularity, degree of beat-to-beat similarity, and measure of electrogram complex distinctiveness to arrive at a diagnostic conclusion. A test set of 121 endocardial electrogram recordings obtained during provocative electrophysiology studies was then used for blinded validation of the algorithm. In normal rhythm, 1:1 tachycardia, atrial tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation, the percentages of sensitivity/specificity were, respectively, 100/99, 100/99, 80/99, 89/98, 91/97, 92/100, and 100/98. Although ventricular rate alone can usually distinguish normal rhythm, ventricular tachycardia, and ventricular fibrillation, it is confounded by atrial arrhythmias and 1:1 tachycardias. When tested on a database, a ventricular rate-only algorithm resulted in sensitivity/specificity of 100/65, 90/78, and 100/99%, respectively, for these three rhythms. Therefore, the dual-chamber algorithm based on both temporal and morphologic measures provides better distinction of normal rhythm and ventricular tachycardia than existing methods, without sacrificing sensitivity.

Arrhythmias, Cardiac↗
PubMed1999

Temperature-controlled radiofrequency catheter ablation with a 10-mm tip electrode creates larger lesions without charring in the porcine heart.

BACKGROUND: Radiofrequency catheter ablation of atrial flutter, atrial fibrillation or ventricular tachycardia may be favoured by large lesions. We compared lesions created in unipolar mode using 10-mm/8 F electrodes with those of 4-mm/7 F catheters. METHODS: Ablations were first performed in porcine hearts in vitro (70 degrees C, 60 s, tangential catheter tip-tissue orientation). Anaesthetized pigs were thereafter ablated with 10- or 4-mm catheters in the right atrial free wall (RAFW), inferior vena cava-tricuspid valve (IVC-TV) isthmus and left ventricle (LV). RESULTS: In vitro, lesion length doubled and lesion volume tripled using the 10-mm catheter. Average power supply was 69 (SD12) (10-mm tip) versus 26 (SD7) W (4-mm tip). In vivo, lesion length increased by 50% and lesion volume fivefold. Charring at the lesion surface or sudden impedance rises were not observed in vivo. Histologically, coagulation necrosis and minor haemorrhages were found. One RAFW lesion (10-mm) showed a dissection approaching the epicardium. Fibrinous platelet clots or overt thromboses covered the endocardial surface in half of all lesions. Three 10-mm electrode isthmus lesions extended to the right descending posterior artery and one LV lesion to the left anterior descending artery, but there was no damage to the arterial walls. Following six ablations with the 10-mm electrode and two with the 4-mm tip, injury to the adjacent lung tissue of 0.5 to 6.0 mm depth was found (p = 0.22). CONCLUSION: RF ablation using 10-mm/8 F electrodes created significantly larger lesions. 10-mm electrodes appeared safe in the porcine IVC-TV isthmus and LV, but not in the RAFW.

Animals↗
PubMed2001

Electrocardiographic manifestations of pulmonary embolism.

The electrocardiogram (ECG) may be entirely normal in the patient with pulmonary embolism (P/E); alternatively, any number of rhythm and/or morphologic abnormalities may be observed in such a patient. The abnormal ECG may deviate from the norm with alterations in rhythm, in conduction, in axis of the QRS complex, and in the morphology of the P wave, QRS complex, and ST segment/T wave. The electrocardiographic findings associated with PE are numerous, including arrhythmias (sinus tachycardia, atrial flutter, atrial fibrillation, atrial tachycardia, and atrial premature contractions), nonspecific ST segment/T wave changes, T wave inversions in the right precordial leads, rightward QRS complex axis shift and other axis changes, S1Q3 or S1Q3T3 pattern, right bundle branch block, and acute cor pulomnale. This review focuses on the ECG and the various abnormalities seen in the patient with PE.

Adult↗
PubMed1995

Atrial arrhythmias and pacing after orthotopic heart transplantation: bicaval versus standard atrial anastomosis.

BACKGROUND: Right and left atrial configuration is more normal when the donor left atrium is anastomosed to a recipient left atrial cuff with direct anastomoses of the donor and recipient vena cavas on the right side. The right atrium and sinus node may be less disturbed by the technique of bicaval anastomosis than by the standard procedure. OBJECTIVE: To compare the incidence of atrial arrhythmias and pacing after bicaval and standard anastomoses. METHODS: 75 patients had heart transplants between January 1991 and December 1993. The notes were reviewed. Nine patients who died within the first 30 days were excluded from further analysis (seven patients with standard anastomoses, one with bicaval anastomosis, and one with a hybrid technique). RESULTS: 66 patients survived for more than 30 days. Thirty five patients had standard anastomoses and 31 bicaval anastomoses. Atrial tachyarrhythmias (atrial fibrillation, atrial flutter, atrial tachycardia, or supraventricular tachycardia) occurred on four days in three patients in the bicaval group compared with 27 days in 13 patients in the standard group (P = 0.009). The relative risk of atrial tachyarrhythmias with standard anastomosis was 5.52 (P = 0.015) compared with that of bicaval anastomosis. Atrial tachyarrhythmias requiring treatment occurred less often in the bicaval group (four episodes in three patients in the bicaval group and eight episodes in four patients in the standard group), and fewer patients with a bicaval anastomosis required temporary pacing (pacing on 20 days in 10 patients in the bicaval group, but pacing on 49 days in 16 patients in the standard group) and late permanent pacing (no patients in the bicaval group and three patients in the standard group), although these differences were not statistically significant. Patients in the bicaval group were discharged from hospital sooner than those in the standard group (mean 24.1 v 29.1 days, P = 0.024). CONCLUSIONS: The technique of bicaval anastomosis, in addition to theoretical advantages from maintaining a more normal atrial configuration, has a lower incidence of postoperative atrial tachyarrhythmias, may reduce the need for pacing, and allows earlier discharge from hospital.

Adult↗
PubMed1979

Computer diagnosis of supraventricular and ventricular arrhythmias. A new esophageal technique.

Computerized arrhythmia monitors recognize only a few of the significant arrhythmias and generally fail to detect arrhythmias of supraventricular origin. This is because conventional surface leads, which are sufficient for QRS recognition, are highly inadequate for automated P-wave detection. A new two-lead system, which includes a swallowable capsule-electrode for esophageal monitoring of atrial activity, is used in an on-line arrhythmia monitor. Three interval measurements (AA, AR and RR) and a QRS shape measurement provide the foundation for a detailed interpretation of each beat. Building on the single-beat analysis, a contextual diagnostic algorithm then recognizes and reports on-line the following arrhythmias: couplets, bigeminy, trigeminy, ventricular tachycardia, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia with retrograde conduction to the atria, first-degree block, second-degree block, Wenckebach periodicity, advanced block, third-degree block and sinus bradycardia.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Tachyarrhythmia therapy utilizing electrical stimulation: a review.

The review is structured in such a way as to fall naturally into four main sections. These are as follows: clinical overview of the common mechanisms leading to the generation of tachyarrhythmias; commonly used sensing techniques and algorithms for the detection of tachyarrhythmias; electrical stimulation algorithms used to terminate many of the rhythms; existing implantable devices and a brief look at the future. The clinical overview introduces the reader unfamiliar with tachyarrhythmias to such mechanisms as sinus tachycardia, supraventricular tachycardias (SVTs), ventricular tachycardia, 'torsade de pointes', and ventricular fibrillation. SVT includes paroxysmal SVT, atrial flutter, atrial tachycardia and junctional tachycardia (enhanced automaticity). Also there is a brief introduction to alternative therapies (drugs, surgery etc.) The sensing techniques section covers input signal processing to enable the R wave to be adequately detected; while the tachycardia detection algorithms section discusses such areas as simple rate detect, rate of change of rate detect, stability of rate, the so-called probability density function technique and some other more complex detection algorithms. The section on electrical stimulation algorithms used for tachycardia therapy discusses burst pacing techniques, special cases such as automatically decrementing bursts and automatically incrementing bursts, defibrillation shock therapy (since fibrillation is a form of tachyarrhythmia) and several other more complex algorithms. The review finishes up with a discussion of current implantable antitachy pacemakers and defibrillators. There is also a speculative look at the future to enable the reader to obtain a full picture.

Algorithms↗
PubMed1999

[Risk factors for in-hospital course and long-term outcome in myocardial infarction].

The aim of the present study is to separate the most important in-hospital and long term outcome risk factors in patients with myocardial infarction. We analysed 251 women and 630 men hospitalised for acute myocardial infarction between 1992-96. We compared history data, in-hospital course and long term observation within 2-6 years in a group of patients who died versus group of patients who survived. The most important risk factors of in-hospital death were: cardiogenic shock--with mortality rate--6.2, pulmonary oedema--2.8, ventricular fibrillation--2.7, third degree A-V block--2.5, supraventricular arrhythmia (atrial flutter, atrial fibrillation--2.4, previous myocardial infarction--2.4, diabetes--2.0, disturbances of intraventricular conduction--1.8. The most important risk factors of long term outcome were: congestive heart failure--III, IV class of NYHA at discharge--mortality rate--3.0, ejection fraction < 40%--2.7, disturbances of intraventricular conduction--2.2, in-hospital cardiogenic shock and/or oedema pulmonum--2.0, prior myocardial infarction--1.9, diabetes--1.7, in-hospital ventricular fibrillation--1.6, supraventricular arrhythmia--1.6. Better predictors of survival we can obtain using multivariate analysis. This analysis allows to separate groups of patient with good, mean and poor prognosis which finally simplify choice of efficient kind of therapy.

Aged↗
PubMed1992

[Paroxysmal atrial arrhythmias in arrhythmogenic cardiomyopathy of the right ventricle with a familial character: the role of right atrial involvement].

Arrhythmogenic right ventricular cardiomyopathy presents a rather frequent familial occurrence. In the present study the cases of two brothers (25 and 30 years old, respectively) presenting with the peculiar finding of early involvement of right atrium, are described. Both subjects were investigated because of recurrent complex arrhythmias, including supraventricular (sustained atrial flutter, atrial tachycardia) and ventricular tachyarrhythmias (very frequent premature beats, nonsustained ventricular tachycardia). The associated echo-angiographic aspects of the right atrium and right ventricle were those typically described in arrhythmogenic right ventricular cardiomyopathy. The familial occurrence of simultaneous right atrial and ventricular involvement, to the best of our knowledge not previously described, can likely be due to the similar phenotypic expression of the same genotype. The prognostic significance of atrial involvement in right ventricular arrhythmogenic dysplasia is still to be defined and the clinical follow-up of these two cases may contribute to it.

Adult↗
PubMedDate not supplied

Taking the mystery out of rhythm interpretation: atrial electrograms.

OBJECTIVE: To verify cardiac rhythms in which diagnosis from conventional surface recordings was unclear. DESIGN: Approximately five electrograms were recorded each week from randomly selected patients who had undergone cardiac surgery in a two-year period from 1989 to 1991. SETTING: A 1000 bed acute care medical facility that provides care to more than 1300 patients per year after open heart surgery. PATIENTS: Adult patients in the surgical intensive care unit or stepdown units who were recovering from coronary artery bypass grafting, valve replacement or repair, aneurysm resection, and/or atrial and ventricular septal defect repairs. RESULTS: The atrial electrogram was used to diagnose various dysrhythmias. The most frequent application was the verification of atrial flutter, atrial fibrillation, and junctional rhythm. Another use was to differentiate between ventricular tachycardia and supraventricular tachycardia with aberrant conduction. CONCLUSION: Critical care clinicians caring for patients who have undergone cardiac surgery must be proficient at rapid, accurate rhythm interpretation to give appropriate treatment. The use of atrial electrograms can be extremely helpful in rhythm interpretation and clarification for this population of patients.

Arrhythmias, Cardiac↗
PubMed1992

Transcatheter ablation of cardiac tissue: advantages and disadvantages of different ablative techniques.

Transcatheter ablation techniques are emerging as an alternative therapeutical tool in the management of cardiac arrhythmias. Catheter ablation was initially introduced as the last resort to ablate the atrioventricular nodal conduction in patients with atrial fibrillation and uncontrolled ventricular response and in patients with drug refractory ventricular tachycardias. Direct current energy was used as the sole source of energy, but because of potential significant complications and early and late mortality, presumably mostly due to ventricular tachyarrhythmias, other sources of energy were sought. Radiofrequency current which does not produce barotrauma and does not require general anesthesia rapidly replaced direct current ablation in many centers. Early results with radiofrequency current ablation of the atrioventricular node and accessory atrioventricular pathways are very encouraging. The results of radiofrequency as well as direct current ablation for atrial flutter, atrial tachycardia and ventricular tachycardia, where the components of reentry circuit are less defined, are not as favorable as those of AV junctional tachycardias. However, improvement of catheter and generatory technology and better understanding of the mechanisms of ventricular tachycardias and characteristics of the target site will enhance the results of catheter ablation in ventricular tachcardias. The procedures are still considered investigational, and mostly done by very experienced groups at tertiary referral hospitals with surgical teams available in case of serious complications. Larger patient populations and longer follow-up periods are required before these techniques expand to community hospitals and to patients with minimal symptoms or asymptomatic individuals as a prophylaxis therapy.

Cardiac Catheterization↗
PubMed2002

Cardiac arrhythmias: diagnosis and management. The tachycardias.

OBJECTIVE: To review the diagnosis and management of cardiac arrhythmias in a two-part presentation. DATA SOURCES: Articles and published peer-review abstracts on tachycardias and bradycardias. SUMMARY OF REVIEW: Normal cardiac rhythm originates from impulses generated within the sinus node. These impulses are conducted to the atrioventricular node where they are delayed before they are distributed to the ventricular myocardium via the His-Purkinje system. Abnormalities in cardiac rhythm are caused by disorders of impulse generation, conduction or a combination of the two and may be life threatening due to a reduction in cardiac output or myocardial oxygenation. Cardiac arrhythmias are commonly classified as tachycardias (supraventricular or ventricular) or bradycardias. The differentiation between supraventricular and ventricular tachycardias usually requires an assessment of atrial and ventricular rhythms and their relationship to each other. In the critically ill patient the commonest tachycardia is sinus tachycardia and treatment generally consist of management of the underlying disorder. Other supraventricular tachycardias (SVTs) include, atrial flutter, atrial fibrillation and paroxysmal supraventricular tachycardia (PSVT) all of which may require cardioversion, although to maintain sinus rhythm, antiarrhythmic therapy is often needed. Adenosine is useful in management and treatment many SVTs although its use in PSVT with Wolff-Parkinson-White syndrome is hazardous. Multifocal atrial tachycardia is a characteristic supraventricular tachycardia found in the critical ill patient. While it usually responds to intravenous magnesium sulphate, its management also requires removal of various precipitating factors. Ventricular tachycardia (VT) and ventricular fibrillation (VF) require urgent cardioversion and defibrillation respectively. Torsade de pointes should be differentiated from these ventricular arrhythmias as antiarrhythmic therapy may be contraindicated. CONCLUSIONS: Supraventricular and ventricular tachycardias in the critically ill patient often have underlying disorders that precipitate their development (e.g. hypokalaemia, hypomagnesaemia, anti-arrhythmic proarrhythmia, myocardial ischaemia, etc). While antiarrhythmic therapy and cardioversion or defibrillation may be required to achieve sinus rhythm, correction of the associated abnormalities is also required.

Journal Article↗
PubMed2006

[Fetal magnetocardiography].

The electrical activities of the heart causes weak changes of the magnetic field, which can be recorded as magnetocardiogram (MCG). Fetal cardiac magnetic activity is measured in the order of less than 10 pT. An advance of the novel technology of a superconducting quantum interference device enabled the first recording of fetal MCG (FMCG) in 1974. In Japan, FMCG instrument (MC6400, Hitachi High-Technologies Ltd) was approved as a diagnostic tool by Japanese Government in 2003 owing to the cooperative studies of Tsukuba University, National Cardiovascular Center and Hitachi Ltd. FMCG offers similar information to a fetal electrocardiogram, which is difficult to be recorded because the fetal skin is covered with fatty caseous vernix of weak electrical conductivity in the second and third trimester of pregnancy. Magnetic flux can pass through the fat layer, and thus FMCG can measure the electrical activity of the fetal heart. Besides FMCG has far higher resolutions in time domain than echocardiography does. The amplitude of FMCG signals depends on the size of fetal heart and the distance between the sensors and the fetal heart. The amplitudes of the QRS, P and T waves increases with gestational age. Since the amplitudes of P and T waves are often weak, averaging of FMCG signals is needed to improve the signal-to-noise ratio. Current-arrow map is a useful mapping technique even in FMCG. FMCG has been applied in the prenatal diagnosis of fetal arrhythmias such as bradyarrhythmia (atrioventricular block, long QT syndrome, etc), tachyarrhythmia (supraventricular tachycardia, atrial flutter, atrial fibrillation and WPW syndrome, etc) and extrasystoles. Fetal cardiomegaly with myocardial abnormalities can be also diagnosed by FMCG. Applications of FMCG for fetal heart rate monitoring using beat-to-beat variability have been also studied to obtain better information on fetal well-beings.

Arrhythmias, Cardiac↗
PubMed2006

[Development of 64-channel magnetocardiography and clinical application].

A magnetocardiogram (MCG) can detect three-dimensional electric phenomena of the heart, because MCG does not influence the lung and torso form of the internal organs. In this symposium, we report the application of 64-channel MCG for the measurement of various arrhythmias (atrial flutter, atrial fibrillation), myocardial injury, and fetus arrhythmia. We composed function images of the conduction wave front and injured myocardium superimposed on a three-dimensional heart outline from the magnetic field. The injured myocardium was determined by a three-dimensional RT dispersion map. This algorithm allows the non-invasive determination of the space location of signal source and injured myocardium. In addition, 64-channel MCG can detect the fetal arrhythmias and autonomic nervous activity, which allows the diagnosis of fetus arrhythmia in detail before birth. Thus, MCG measurement is a useful non-invasive diagnostics procedure. However, there are several problems such as sealed room installation and the use of liquid helium. In the future, a newer technology that does not require liquid helium and a sealed room will be necessory.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[Clinical significance and treatment of cardiac arrhythmia in children].

Cardiac dysrhythmias during childhood are not infrequent. Often they are found in otherwise healthy children, sometimes in connection with myocarditis, cardiomyopathy, congenital heart defects or after cardiac surgery. Cardiac dysrhythmias may be subdivided in bradydysrhythmias (sinuatrial block, sinus arrest, atrioventricular block) and tachydysrhythmias (supraventricular extrasystoles, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular extrasystoles, and ventricular tachycardia). Frequently, cardiac dysrhythmias in children do not need treatment; in other cases, treatment is necessary and effective while for some cases a satisfactory treatment is not available at present.

Anti-Arrhythmia Agents↗