[Electric cardioversion in atrial and ventricular ectopic arrhythmias. Study of 50 cases].
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Adult↗
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Preliminary investigation of the efficacy of sublingual verapamil in the management of acute atrial fibrillation and flutter.
The antiarrhythmic properties of sublingual verapamil were investigated in seven patients with acute fast atrial flutter (n = 2) or fibrillation (n = 5). A rapid and significant (P < 0.05) reduction in the ventricular rate was achieved in all seven patients. The ventricular rate at peak plasma verapamil concentration (+/- s.d.) was significantly slower than on admission (101.6 +/- 11.3 and 159 +/- 5.3 beats min-1 respectively, P < 0.01). The ventricular rate remained controlled for over 4 h. Sublingual verapamil was rapidly absorbed with the maximum peak plasma concentration (153.3 +/- 15.5 ng ml-1) being achieved after 1.21 +/- 0.18 h. Side-effects of sublingual verapamil were limited to one report of a bitter taste. The sublingual administration of verapamil may provide an alternative method for the control of acute fast atrial fibrillation and flutter in selected patients.
Acute Disease↗
Efficacy and safety of ibutilide fumarate for the conversion of atrial arrhythmias after cardiac surgery.
BACKGROUND: Atrial arrhythmias occur commonly after cardiac surgery and are a cause of significant morbidity and increased hospital costs, yet there is no well-studied treatment strategy to deal with them expeditiously. The purpose of this study was to determine the efficacy and safety of ibutilide fumarate, an approved drug for the rapid conversion of atrial fibrillation and flutter, in patients after cardiac surgery. METHODS AND RESULTS: Patients with atrial fibrillation or flutter occurring 1 to 7 days after surgery and lasting 1 hour to 3 days were randomized to receive two 10-minute blinded infusions of placebo or 0.25, 0.5, or 1.0 mg of ibutilide fumarate. Treatment was considered successful if sinus rhythm was restored for any period of time by hour 1.5. A total of 302 patients were randomized, 201 with fibrillation and 101 with flutter. Treatment with ibutilide resulted in significantly higher conversion rates than placebo, and efficacy was dose related (placebo 15%; ibutilide 0.25 mg 40%, 0.5 mg 47%, and 1.0 mg 57%). Conversion rates at all doses were higher for atrial flutter than for atrial fibrillation. Mean time to conversion decreased as the dose was increased. Polymorphic ventricular tachycardia was the most serious adverse effect and occurred in 1.8% of the ibutilide-treated patients compared with 1.2% of patients who received placebo. CONCLUSIONS: Ibutilide is a useful and safe treatment alternative for the atrial arrhythmias that occur after cardiac surgery.
Adult↗
[Prevention of atrial flutter with Chinidin retard].
The action of the preparation Chinidin retard, tablets of 0.250, was studied with a view to its effects of preserving the recovered sinus rhythm after regularization in 32 patients with atrial flutter, as well as its effect on central hemodynamics and functions of parenchymal organs. The successful anti-recurrence treatment and the maintenance of lasting sinus rhythm after regularization in 90.6 per cent of the patients for more than 6 months with only 2 tablets daily, provided grounds to recommend chinidin retard as an agent of choice for long-term prophylaxis against the paroxysm of atrial flutter. The preparation has a lightly manifested negative inotropic action, but with the doses administered--it leads to no left-ventricular dysfunction. The long-term treatment with chinidin retard has no toxic effect on parenchymal organs.
Atrial Flutter↗
Clinical interest of a sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia in dual chamber pacing.
UNLABELLED: A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called "conditional ventricular tracking limit" (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/min. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. METHOD: A Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3-month follow-up. RESULTS: In seven patients, Holter recordings showed supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR (one patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). CONCLUSION: The CVTL algorithm is effective in protecting against high ventricular pacing rates during supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.
Acceleration↗
Mechanoelectrical interaction in tetralogy of Fallot. QRS prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death.
BACKGROUND: Life-threatening ventricular arrhythmia and sudden death remain serious late complications after tetralogy of Fallot repair. Nevertheless, there remains no clear way of predicting which patients are at risk. METHODS AND RESULTS: The study population included a total of 178 adult survivors (mean follow-up, 21.4 years) of tetralogy of Fallot repair who were currently attending our clinic. Mechano-electrical relations were sought in 41 of the patients (mean follow-up, 23.6 years) who were operated on by one surgeon and who were prospectively studied with a 12-lead ECG, chest radiography, and two-dimensional and Doppler echocardiography. Nine patients (mean follow-up, 17 years) from the total group of 178 were identified as having had sustained ventricular tachycardia (8 with near-miss sudden death), and their ECGs, Holter monitor readings, electrophysiological studies, and chest radiographs were reviewed. The case notes of an additional 4 patients with postoperative sudden cardiac death also were available for review. QRS duration in the 41 patients in whom mechanoelectrical interaction was sought ranged between 90 and 200 milliseconds and correlated with cardiothoracic ratio (CTR) on chest radiography (r = .64, P < .001) and with right ventricular size on echocardiography (r = .43, P < .02). Twenty of the 41 patients had restrictive right ventricular Doppler physiology (reduced ventricular compliance) with mean QRS duration of 129.3 +/- 20 milliseconds and mean CTR of 0.51 +/- 0.03. The remaining 21 patients with no evidence of right ventricular restriction had prolonged QRS duration of 157.5 +/- 13.2 milliseconds (P < .001) and CTR of 0.55 +/- 0.04 (P < .04) compared with the restrictive. In the 9 patients with ventricular tachycardia, the QRS duration ranged from 180 to 230 milliseconds (mean, 198.9 +/- 17.6 milliseconds), and the CTR ranged from 0.54 to 0.9 (mean, 0.67 +/- 0.12) (P < .0001 and P < .01, respectively, compared with patients without life-threatening arrhythmias). All patients with documented sustained ventricular tachycardia and the 4 patients with sudden death had a QRS duration of > or = 180 milliseconds (100% sensitivity). CONCLUSIONS: Chronic right ventricular volume overload after tetralogy of Fallot repair is related to diastolic function and correlated with QRS prolongation. The risk of symptomatic arrhythmia is high when marked right ventricular enlargement and QRS prolongation develop. A QRS duration on the resting ECG of > or = 180 milliseconds is the most sensitive predictor of life-threatening ventricular arrhythmias yet described.
Adult↗
Assessment and follow-up of pediatric survivors of sudden cardiac death.
In the young patient resuscitated from sudden cardiac arrest, the risks of recurrence are uncertain and so are the criteria defining therapeutic efficacy for the presumed cause of the initial event. In this study, we analyzed the outcome of 15 consecutive young patients, who were resuscitated from pulseless ventricular tachycardia or ventricular fibrillation and who were evaluated by comprehensive hemodynamic and electrophysiological testing. Patients were 11.2 +/- 2.7 (mean +/- SD) years old at the time of their event, and each was known to have some form of heart disease before sudden cardiac arrest. Ventricular tachycardia or fibrillation was inducible by programmed electrical stimulation in eight patients. Accessory atrioventricular connections, with antegrade effective refractory periods less than 220 msec, were identified in three patients. Sustained atrial flutter was the only arrhythmia inducible in two patients, and no arrhythmias were inducible in two other patients. Surgical or electrophysiological-guided medical therapy resulted in noninducibility of the ventricular arrhythmias in six patients. Surgical division of the accessory atrioventricular connections was performed in three patients, and arrhythmias were not inducible after operation. The four patients with atrial flutter or without defined arrhythmia were treated with an empiric therapy. During 37 +/- 14 months of follow-up, the nine patients with documented noninducibility of a defined cause of sudden cardiac arrest were free of recurrent events. In contrast, during 18 +/- 10 months of follow-up, two of the six patients with empiric therapy or persistent inducibility of ventricular tachycardia died suddenly, and three others had recurrence of ventricular tachycardia or fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Anatomic and electrophysiological differences between chronic and paroxysmal forms of common atrial flutter and comparison with controls:.
Whether chronic typical atrial flutter differs from paroxysmal atrial flutter regarding electrophysiological properties of reentry pathways and cardiac function remains unknown. If so, can remodeling due to long duration of persistently rapid atrial or ventricular rates explain these changes? The aim of the study was to compare RA local conduction velocities and heart function parameters between three groups: (1) chronic atrial flutter, (2) paroxysmal atrial flutter, and (3) controls. The study evaluated 52 patients undergoing radiofrequency ablation for typical atrial flutter. There were 35 patients with chronic atrial flutter (62.7 +/- 14 years) and 17 patients with paroxysmal atrial flutter (62.7 +/- 10 years). Underlying structural heart disease was present in 20 (57%) of 35 chronic atrial flutter patients and in 7 (41%) of 17 paroxysmal atrial flutter patients (P = 0.1). Chronic atrial flutter duration was 10.9 +/- 17 months and paroxysmal atrial flutter duration was 8.5 +/- 10 (P = 0.06). RA conduction velocity measurements were carried out before ablation during sinus rhythm under pacing (600-ms cycle length) with a 12-pole steerable catheter positioned in the high lateral RA (poles 11-12 [H6]), mid-lateral RA (poles 9-10 [H5]), and along the inferior vena caval tricuspid isthmus (poles 7-8 [H4]; 5-6 [H3]; 3-4 [H2]) with its distal electrode pair at the coronary sinus origin (pole 1-2 [H1]). Counter-clockwise RA conduction velocities were assessed from H6 to H1 and clockwise RA conduction velocities from H1 to H6. After successful ablation, RA and LA areas, LV volumes, LVEF, inferior vena caval tricuspid annulus, and coronary sinus tricuspid annulus (septal isthmus) lengths were measured by two-dimensional echocardiography. The control group included 12 patients without structural heart disease, referred for electrophysiological evaluation of AVN reentry. Counter-clockwise RA conduction velocities at the inferior vena caval tricuspid isthmus were lower in chronic atrial flutter than in paroxysmal atrial flutter (H4, 1.19 +/- 0.4 vs 1.89 +/- 1 m/s, P = 0.0051; H3, 1.14 +/- 0.4 vs 1.6 +/- 0.7 m/s, P = 0.0015; H2, 1.16 +/- 0.4 vs 1.53 +/- 0.5 m/s, P < 0.0056 and H1, 1.2 +/- 0.4 vs 1.5 +/- 0.4 m/s, P = 0.03, respectively). Counter-clockwise RA conduction velocities were identical at the high and mid-lateral RA. Counter-clockwise caval isthmus RA conduction velocities from H3 to H1 were significantly different between chronic atrial flutter and controls (H3, 1.14 +/- 0.4 vs 1.7 +/- 0.3 m/s, P = 0.0014; H2, 1.16 +/- 0.4 vs 1.83 +/- 0.4 m/s, P < 0.0001 and H1, 1.2 +/- 0.4 vs 1.94 +/- 0.4 m/s, P < 0.0001, respectively). A difference was found regarding clockwise isthmus RA conduction velocities between the two groups of atrial flutter and controls but not between chronic atrial flutter and paroxysmal atrial flutter. Respectively, chronic atrial flutter had greater RA and LA areas (24.5 +/- 5 vs 13 +/- 2 cm2; P < 0.0001 and 23 +/- 5 vs 16 +/- 3 cm2, P < 0.0001), LV end-systolic and end-diastolic volumes (50 +/- 25 vs 32 +/- 13 cm3, P = 0.0084 and 112 +/- 40 vs 85 +/- 25 cm3, P = 0.01), septal isthmus length (21 +/- 3 vs 13 +/- 2 mm, P < 0.0001), and inferior vena caval tricuspid isthmus length (39 +/- 6 vs 23 +/- 5 mm; P < 0.0001). Chronic common atrial flutter is characterized by more prolonged counter-clockwise conduction times and larger anatomic conduction pathways than the paroxysmal form, the causal relationship between electrophysiological and anatomic characteristics remains to be demonstrated.
Atrial Flutter↗
The mechanisms of exercise provocation of supraventricular tachycardia.
Treadmill exercise tests, electrophysiologic studies, and isoproterenol infusions were performed in 14 patients with exercise provocable supraventricular tachycardia to delineate the mechanisms of exercise provocation of paroxysmal supraventricular tachycardia. Treadmill exercise tests reproducibly provoked supraventricular tachycardia in all patients. Supraventricular tachycardia similar to that provoked by exercise occurred spontaneously during isoproterenol infusions in 9 of 11 patients tested. The specific supraventricular tachycardia diagnoses of all patients were atrial reentrant tachycardia (two patients), automatic atrial tachycardia (three), atrial flutter-fibrillation (one), atypical junctional tachycardia (two), and orthodromic atrioventricular (AV) reentrant tachycardia (six) as defined by electrophysiologic studies. Various mechanisms of exercise or isoproterenol induction of supraventricular tachycardia were identified. A critical heart rate and/or appropriate sympathetic state was found to provoke all instances of reentrant or automatic atrial tachycardia and atypical junctional tachycardia. A properly timed atrial premature beat provoked five of six cases of AV reentrant tachycardia and the only case of atrial flutter-fibrillation. The remaining case of AV reentrant tachycardia was induced by a ventricular premature beat. In conclusion, the mechanisms of exercise provocation of reentrant or automatic supraventricular tachycardia are multiple and include a critical sinus rate, increased sympathetic tone, and properly timed atrial or ventricular premature beats.
Adrenergic beta-Agonists↗
Risk factors associated with new onset tachyarrhythmias after cardiac surgery--a retrospective analysis.
BACKGROUND: Tachyarrhythmias (TA) represent a frequent and serious problem after cardiac surgery. We retrospectively analyzed 987 cardiac surgery patients admitted to a surgical intensive care unit between 1996 and 1999 to assess incidence and risk factors associated with development of postoperative TA in the intensive care unit. METHODS: TA (n=149) were defined as non-sinus rhythm with a heart rate (HR) > or =100 bpm in patients with preoperative sinus rhythm or as heart rate > or =130 bpm in patients with preoperative atrial fibrillation. A total of 787 patients served as controls (C). Demographic, premorbidity and perioperative data, admission SAPS and MODS-score, presence of clinical syndromes systemic inflammatory response syndrome (SIRS) and sepsis were univariately compared between groups. For prediction of independent risk factors for TA-development two multiple logistic regression models were finally established. RESULTS: Concerning TA, atrial fibrillation and flutter (76%) were observed most frequently, followed by paroxysmal supraventricular tachycardia (15%) and ventricular tachycardia/fibrillation (11%). Age, a history or presence of congestive heart failure, development of SIRS and sepsis, severity of multiple organ dysfunction syndrome and in particular severity of cardiovascular failure proved to be independent risk factors for development of TA. CONCLUSION: In cardiac surgery patients, age, a history or presence of congestive heart failure, postoperative development of a systemic inflammatory response syndrome or sepsis and the severity of multiple organ function syndrome were independent predictors for development of TA in the intensive care unit. The association of severity of cardiovascular dysfunction with TA strongly suggests a causal relationship between catecholamine therapy and TA-development.
Aged↗
Sick sinus syndrome. Symptomatic cases in children.
In 20 children needing treatment for symptomatic sick sinus syndrome, the average age at presentation was 7.1 years and ranged from 9 months to 18 years. Symptoms were never precise but, in retrospect, 5 children had syncope, 7 had a rapid heart action, 6 had dyspnoea or tachypnoea, 2 had nonspecific chest pains, 2 had pale spells, and 1 had a sudden hemiplegia. Symptoms followed cardiac surgery in 15 cases and were related to unoperated congenital heart disease in 2 and to myocarditis in 2. The aetiology was unknown in 1 case. The type of cardiac surgery resulting in the development of the sick sinus syndrome was predominantly related to atrial suturing. Both tachy- and bradydysrhythmias were found, including wandering atrial pacemaker (9 cases), junctional rhythm (19 cases), supraventricular tachycardia (9 cases), atrial flutter (11 cases), and atrial fibrillation (2 cases). Both atrial (8 cases) and ventricular (7 cases) premature beats were seen. All patients were given trials of drug therapy but difficulties were encountered. Cardioversion was used for tachyarrhythmias in 11 cases without serious problems. Six children had permanent cardiac pacemakers inserted with good results. Recognition of the sick sinus syndrome in childhood is important and treatment must be regulated by the severity of symptoms.
Adolescent↗
Dofetilide: a class III-specific antiarrhythmic agent.
OBJECTIVE: To review published reports on the pharmacology and clinical use of dofetilide in the management of cardiac dysrhythmias. DATA SOURCES: A MEDLINE search (January 1966-June 1999) was performed using dofetilide and UK-68,798 as key words. English-language articles were identified, and the references of these articles were used to further identify pertinent articles. STUDY SELECTION: All acquired studies and reviews discussing the pharmacology, pharmacokinetics, chemistry, and clinical efficacy of dofetilide were reviewed. DATA EXTRACTION: Articles were selected based on quality of review of the pharmacology and clinical use of dofetilide. Given the paucity of data on the clinical pharmacology and use of dofetilide, most articles obtained were used, including abstracts when full reports were not available. DATA SYNTHESIS: Dofetilide is a relatively specific class III antiarrhythmic agent. It increases action potential duration and effective refractory period without impacting conduction velocity. These actions of dofetilide are explained by its ability to inhibit the rapid component of the delayed, outward-rectifying potassium current, thus blocking the efflux of potassium during repolarization. Introductory investigations suggest that dofetilide may be of use in treating and preventing atrial dysrhythmias such as atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. Dofetilide may also have a role in preventing ventricular tachycardia from occurring. Some data also suggest that dofetilide may improve the morbidity of heart failure patients. Currently, the most troublesome adverse effect of dofetilide is its propensity to induce ventricular proarrhythmias, especially torsade de pointes. CONCLUSIONS: Based on the data currently available, dofetilide should have a role in the pharmacotherapy of cardiac dysrhythmias, especially those of atrial origin. More data on its efficacy and tolerability are needed, however, to fully delineate dofetilide's role amid currently available antiarrhythmic agents.
Adult↗
[A case of pheochromocytoma with an AMI-like ECG change corrected by an alpha-blocking agent].
A 59 year-old housewife was admitted to the emergency service with a sudden onset of chest pain and nausea. Initially she was treated as an acute myocardial infarction, but conventional treatments were not effective, and she was sent to our hospital for further evaluation. Her ECG showed several abnormal findings including T-wave inversion, atrial flutter, QT-time prolongation, ST-segment depression or elevation, and frequent ventricular ectopic beats. The echocardiogram, 201thallium scintigram and coronary angiography were almost normal. Both urinary and plasma levels of catecholamines were remarkably increased, and the plasma epinephrine was extremely high during attacks. Abdominal echotomography and CT-scanning showed a large left adrenal tumor. The 131MIBG scintiscan revealed a high accumulation in this tumor. Then the patient was diagnosed as having pheochromocytoma and catecholamine-induced myocarditis. The administration of phentolamine (10 mg) normalized the inversion of T-wave and the high blood pressure. But when propranolol (2 mg) was administrated in addition to phentolamine, the ECG showed a biphasic low T-wave change. According to these phenomena, we supposed that the alpha-adrenergic receptor was involved in the development of the ST-T changes of the ECG, and the alpha-adrenergic receptor of this patient might be sensitive under excessive catecholamines, according to the inhibition of the beta-receptor by propranolol.
Adrenal Gland Neoplasms↗
Enlarged effects of adenosine in a septic patient with multiple myeloma and atrial flutter.
We report the history of a 60-year-old patient with a multiple myeloma and Staphylococcus aureus associated sepsis to whom adenosine in a dose of 6 mg was administered, when a regular, narrow QRS complex tachycardia at a heart rate of 120 beats/minute started. Adenosine led to a complete AV-block and revealed atrial flutter. Atrial flutter waves persisted for about 15 seconds and were followed by atrial and ventricular asystole for about 20 seconds. Repeated nonsustained polymorphic ventricular tachycardias followed and after about 90 seconds sinus rhythm was restored.
Adenosine↗
[Initial experience with adenosine triphosphate in supraventricular arrhythmia].
The author presents data from the literature pertaining to the possible use of adenine nucleosides in recent years. The main action of adenosine or adenosine triphosphate is focused above all on influencing supraventricular tachycardia which developed as a result of the reentry mechanism. Based on his own observation, the author presents his initial experience with adenosine triphosphate (ATP, Spofa) in different indications: interference with supraventricular tachycardia with slim QRS complexes, interference of tachycardia with wide QRS complexes, termination of atrial flutter in digitalis intoxication and finally induction of an electrocardiographic tracing of latent ventricular preexcitation of the Wolf-Parkinson-White syndrome type.
Adenosine Triphosphate↗
[Clinical and electrophysiological indications for surgical treatment in patients with Wolff-Parkinson-White syndrome].
20 patients with WPW syndrome and recurrent tachyarrhythmias were studied clinically and electrophysiologically. The localization and electrophysiological properties of accessory pathways and other heart structures were estimated before the surgical treatment. 13 patients (pts) suffered syncope in the course of atrial flutter or atrial fibrillation with heart rate greater than 300/min, often proceeding into ventricular fibrillation or atrioventricular tachycardia greater than 260/min, which sometimes proceeds into atrial/ventricular fibrillation. 6 pts experienced dizziness or fainted during tachyarrhythmias or rhythm changes. In 15 pts antiarrhythmic drugs in monotherapy or various combinations did not prevent recurrence of tachyarrhythmias. In 4 of 5 other pts only amiodarone was effective but the drug was discontinued due to serious adverse effects. The lack of good effect of antiarrhythmic drug therapy can be based on mutually unfavorable electrophysiologic properties of the accessory pathways and other heart structures. Pts who experienced syncope had a particularly short effective refractory period (ERP) of the accessory pathways in ante- and retro-grade direction and short ERP of the ventricle muscle. Additionally, there were multiple accessory pathways, heart muscle impairement and frequent ventricular premature beats--factors triggering the tachyarrhythmias.
Adolescent↗
[Qualitative and quantitative one- and two-dimensional echocardiography assessment of chronic aortic insufficiency].
It is reported on the results of one- and two-dimensional echocardiographic investigations, which were partly supplemented by investigations in Doppler-technique, in 20 patients with an aortic insufficiency in the clinical stage II and 20 patients with an aortic insufficiency in stage III. As comparison serve the results of the examinations of 20 normal persons. The diagnosis of an aortic insufficiency was to be made in all cases by the evidence of fluttering waves on the anterior and posterior mitral valve, partly also on the ventricular septum. The diagnosis can be ascertained by the Doppler-echocardiographic proof of a regurgitation through the aortic valve. Diameter, thickness of the wall, volumes and functional parameters of the left ventricle as well as the size of the left atrium and the diameter of the aortic root proved to be suitable for the judgment of the degree of severity. Severe aortic insufficiencies are characterized by a dilatation and hypertrophy of the left ventricle, a dilatation of the left atrium, an enlarged diameter of the aortic root, clearly increased volumes restricted functional parameters of the left ventricle.
Adult↗
[Transient entrainment of tachycardia].
Transient entrainment of tachycardia by pacing at a faster rate corresponds to its acceleration with return to sinus rhythm either when the pacing is interrupted or when the pacing rate is slowed. It conforms to strict criteria detectable either on the surface electrocardiogramme (constant fusion, progressive fusion, change of morphology before termination of a tachycardia) or on selective endocavitary recording when entrainment is hidden. The phenomenon described by Waldo in 1977 in atrial flutter is found in all reentrant tachycardias. It is currently being studied in ventricular tachycardia. The electrophysiological concept is useful because it facilitates the understanding of the mode of termination of tachycardia by stimulation and the localisation of zones for destruction during ablation.
Cardiac Pacing, Artificial↗