Adenosine and Preexcitation Variants: Reappraisal of Electrocardiographic Changes.

Intravenous adenosine is a short-acting blocker of the atrioventricular node that has been used to unmask subtle or latent preexcitation, and also to enable catheter ablation in selected patients with absent or intermittent preexcitation. Depending on the accessory pathway characteristics, intravenous adenosine may produce specific electrocardiographic changes highly suggestive of the preexcitation variant. Herein, we view different ECG responses to this pharmacological test in various preexcitation patterns that were confirmed by electrophysiological studies. Careful analysis of electrocardiographic changes during adenosine test, with emphasis on P-delta interval, preexcitation degree, and atrioventricular block, can be helpful to diagnose the preexcitation variant/pattern.

The appearance of ventricular preexcitation during exercise testing reproduced by dobutamine administration.

A 33-year-old woman presented with exercise-related palpitations after an apparently successful catheter-ablation of overt midseptal accessory pathway. Post procedure, the electrocardiogram at rest was normal, while the progressive appearance of delta-wave during treadmill stress testing was recorded. In addition, the occurrence of ventricular preexcitation was reproduced by controlled administration of dobutamine. Detailed understanding of the unusual pathway electrophysiology resulted in specific planning of the second procedure. In the basal state, pacing maneuvers did not demonstrate any evidence of pathway conduction. However, during infusion of dobutamine bidirectional conduction in the right anterior pathway was restored, enabling definitive cure by radiofrequency.

Optical imaging of spiral waves: pharmacological modification of spiral-type excitations in a 2-dimensional layer of ventricular myocardium.

Differential effects of sodium channel blockers, an I(Kr) blocker (nifekalant) and amiodarone on the spiral-type reentry, were investigated in rabbit hearts by using a high-resolution optical mapping system. Two-dimensional subepicardial layer of left ventricular myocardium with uniform anisotropy was prepared by endocardial cryoablation. During ventricular tachycardia (VT) elicited by cross-field stimulation, spiral-type excitations rotating around functional block lines (FBLs) were visualized. All the sodium channel blockers stabilized rotors; VT duration was prolonged in association with increases of FBLs and VT cycle length. The rotors in the presence of nifekalant were characterized by large meandering, long FBLs, and frequent front-tail interactions generating wave breaks. Amiodarone (acute application) increased FBLs and VT cycle length, but shortened the VT duration with minimal front-tail interaction. These results suggest that multifaceted drug action on both depolarization and repolarization may be required for the early termination of spiral-type reentry without causing breakup of rotors.

Intermittent noninfarction Q waves: a finding suggestive of latent preexcitation.

OBJECTIVE: To describe 3 patients who presented with chest pain and intermittent Q waves on the electrocardiogram (ECG) and were subsequently found to have latent preexcitation. PATIENTS AND METHODS: During a span of 8 years, 3 patients were evaluated because of atypical chest pain and pathologic Q waves in the inferior leads; in all 3 patients, the Q waves were intermittent. No patient had a history of arrhythmia or had Wolff-Parkinson-White pattern on the ECG. Diagnostic and therapeutic interventions for suspected myocardial infarction included cardiac catheterization in 2 patients, intravenous thrombolytic therapy in 1 patient, and heparin in 2 patients. Ischemic heart disease was excluded in all. Patients underwent pharmacological testing and/or electrophysiologic study for suspected preexcitation. RESULTS: Despite the absence of ECG markers of preexcitation, the presence of a latent accessory atrioventricular connection was confirmed in each patient by pharmacological or electrophysiologic studies. CONCLUSION: In patients who present with intermittent noninfarction Q waves, the most likely diagnosis is latent preexcitation. Clinicians need to be educated about this clinical diagnosis and encouraged to pursue confirmatory testing. Such patients should be informed about the nature and importance of their electrocardiographic abnormality.

Clinical and evolutive aspects in ventricular preexcitation syndromes in child.

Ventricular preexcitation syndromes (VPS) are very important between cardiac rhythm disturbances in childhood, because their presence can change the clinical and ECG picture and thus the treatment can be very difficult. The authors studied 58 cases of VPS in children (2 weeks-15 years old) admitted in a period of 3 years. The surface ECG showed VPS aspects: in 30% of cases we noticed WPW syndrome type B and the rest presented VPS with Mahaim pathways and Lown-Ganong-Levine syndrome. 4 cases were familial and 1 child a hidden WPW syndrome. In 65% of cases the cardiac symptoms put the diagnosis and 1/3 of cases were discovered by common ECG. The most important cardiac sign of the children with WPW syndrome was the paroxysmal supraventricular tachycardia, 4 cases presenting wide QRS complex. Others types of VPS were without clinical symptoms. The intravenous administration of digoxin + propranolol was the therapy of choice for paroxysmal supraventricular tachycardia in infants and children until 2-3 years old, and propranolol and chinidine after this age. The children older than 2-3 years and/or those with ineffective preventive for recurrent treatment received dysopiramide and specially amiodarone with satisfactory results; it was not necessary the surgical ablation of the aberrant pathway. Ventricular preexcitation syndromes and wrong treatment can induce severe ventricular arrhythmia, so all the tachyarrhythmias with unknown etiology and especially those with wide QRS complex must be investigated very carefully, using and Holter test and the endocavitary electrophysiology, for a correct medical and/or surgical treatment.

The natural history of postischemic T-wave inversion: a predictor of poor short-term prognosis?

BACKGROUND: This study followed up the natural history of T-wave inversion and assessed the short-term prognosis associated with the condition. METHODS: Forty patients with acute ischemic syndrome, without infarction, and with postischemic T-wave inversion (group 1) were followed during the persistence (inverted T-wave period) and after the resolution of T-wave inversion (positive T-wave period). Another 40 patients with acute ischemic syndrome, without infarction and with normal T waves (group 2), were also followed. RESULTS: Postischemic inverted T waves showed resolution within 3-21 days of presentation in 31 patients from group 1 on medical treatment alone. Further ischemic events (acute myocardial infarction, acute ischemic syndrome, angina pectoris, silent ischemia), inducible ischemia (during treadmill test), wall-motion abnormalities (demonstrated by echocardiography), all developing in the primarily ischemic myocardial area, were more frequent (P < 0.02) in group 1 patients during the inverted T-wave period compared with those experienced in the positive T-wave period of group 1 patients, and compared with group 2 patients. CONCLUSION: In most patients on medical treatment, postischemic inverted T-waves tended to resolve within 3 weeks. The presence of postischemic inverted T waves appears to be an independent marker of further ischemic events.

[Effects of rotundium on clinical electrophysiology in patients with pre-excitation syndrome].

Acute electrophysiologic effects of rotundium were studied with programmed electrical cardiac stimulation in 14 patients with paroxysmal tachyarrhythmias due to preexcitation syndrome after intravenous infusion of 2 mg/kg. The results showed that the drug depressed the function of the atrioventricular node markedly. Significant lengthening of A-H interval (from 75 +/- 19ms to 88 +/- 21ms, P < 0.01), AVNERP (from 246 +/- 47ms to 290 +/- 45ms, P < 0.01), AVNWCL (from 326 +/- 23ms to 388 +/- 42ms, P < 0.01) were seen. But no significant influence on SNRT, CSNRT and SACT (P < 0.05) were observed. Rotundium lengthened A-delta interval (from 97 +/- 18 ms to 106 +/- 19ms, P < 0.05) and the anterograde effective refractory period (ERP) of the accessory pathway (from 287 +/- 36ms to 320 +/- 43ms P < 0.05). It slightly lengthened V-A interval and the retrograde ERP of the accessory pathway. Rotundium lengthened AERP significantly (from 216 +/- 37ms to 244 +/- 41ms, P < 0.02). The effective rate of prevention of supraventricular tachycardia (SVT) by PES in this study was 77.8% (7/9). Rotundium showed no severe side effect in this study.

Supraventricular tachycardia and pre-excitation syndromes: pharmacological therapy.

Tachyarrhythmias which originate above the bifurcation of the bundle of His or incorporate tissue proximal to it are classified as supraventricular tachyarrhythmias (SVT). Primary treatment of SVT attempts to influence the underlying disease. Therapy is subdivided into drug therapy, electrotherapeutic tools (e.g. antitachycardia pacemakers, catheter ablation) and antiarrhythmic surgery. Antiarrhythmic agents which slow conduction and suppress premature beats are efficient for emergency and long-term treatment of supraventricular tachycardias. We evaluated some of the most relevant antiarrhythmic drugs for SVT including propafenone, diprafenone, cibenzoline, lorcainide and sotalol; in addition, usage and efficacy of quinidine/verapamil, disopyramide, amiodarone, ajmaline, adenosine and flecainide are summarized. The principles for acute management of tachycardia episodes with narrow and broad complexes are outlined. The reason for the selection as well as the efficacy in the termination of the tachycardias is described for different antiarrhythmic agents including verapamil, adenosine, ajmaline, propafenone and flecainide.

[The clinical cardiac electrophysiologic effects of tetrandrine].

Acute electrophysiologic effects of intravenous tetrandrine were evaluated with programmed electrical stimulation in 20 patients. The results showed that: (1) tetrandrine significantly lengthened SCL and A-H interval (P < 0.001), AVNERP, AVNWCL and SPERP (P < 0.05). It did not affect the SACT, SNRT, P-A, H-V, Q-T intervals and the ERP of atrium, ventricle and accessory pathway significantly. Its electrophysiologic property is similar to verapamil. (2) It prevented induction of SVT in 4 cases, 4 cases of sustained SVT were no longer sustained, the effective rate is 85.7%. The curative effect on AVNRT (100%) is better than that on AVRT (71.4%). (3) No severe side effect was observed. Therefore, tetrandrine is an effective drug for the treatment of SVT.

Electrophysiological and electropharmacological studies in pre-excitation syndromes: results with propafenone therapy and isoproterenol infusion testing.

To study the electrophysiological effects of oral propafenone on accessory pathways and determine the potential for catecholamine-mediated reversal of these effects, comprehensive electrophysiology studies (EPS) were conducted in 11 patients with manifest (n = 9) or concealed (n = 2) pre-excitation syndrome. EPS were performed at baseline (in the drug-free state), after oral propafenone loading, and with isoproterenol infusion during propafenone therapy. The study group included 10 men and 1 woman with a mean age of 39 +/- 13 years, who presented with symptoms of palpitations (n = 6), presyncope (n = 3) and syncope (n = 2). The clinical arrhythmia was atrioventricular reciprocating tachycardia (n = 6), atrial flutter/fibrillation (n = 3), or both (n = 2). During the baseline EPS the accessory pathway location was identified as left (n = 6) or septal (n = 5). The mean anterograde effective refractory period was 265 +/- 42 ms, the shortest pre-excited RR interval 259 +/- 20 ms and the retrograde refractory period 258 +/- 39 ms. Orthodromic atrioventricular reciprocating tachycardia was induced in 10 patients (mean cycle length = 324 +/- 31 ms). Antidromic reciprocating tachycardia was induced in one patient (cycle length = 340 ms). In all the 11 patients EPS were repeated after 4 days of oral propafenone loading (668 +/- 226 mg daily) when drug steady state was expected to have been achieved. One additional patient had baseline EPS but developed clinical arrhythmia recurrences after propafenone loading and thus he was excluded from the study; follow-up EPS were conducted on procainamide.(ABSTRACT TRUNCATED AT 250 WORDS)

[The prospective evolution of the efficacy of antiarrhythmia therapy in paroxysmal supraventricular tachycardia in patients with the ventricular pre-excitation syndrome]. / Prospektivnaia évoliutsiia éffektivnosti antiaritmicheskoi terapii pri paroksizmal'noi nadzheludochkovoi takhikardii u bol'nykh s sindromom prezhdevremennogo vozbuzhdeniia zheludochkov.

Evolution of the effectiveness of antiarrhythmic drugs used in 240 patients with preexcitation syndrome to arrest episodes of paroxysmal supraventricular tachycardia was analysed prospectively. The first intravenous administration was effective in 97, 93.3, 80.9, 75, 70.3, 60, 48% of cases for novocainamid, verapamil, cordarone, disopyramide, ajmaline, ethacizine, mexitil and inderal, respectively. When observed in prospective evolution for 10-14 years, overall group efficacy dropped from 81.3% at first administration to 21.4%.

[The diagnostic and treatment characteristics of cardiac arrhythmias in patients with the premature ventricular excitation syndrome]. / Osobennosti diagnostiki i lecheniia aritmii serdtsa u bol'nykh s sindromom prezhdevremennogo vozbuzhdeniia zheludochkov.

Studied were 24 patients with the syndrome of premature excitation of the ventricles. In 18 of them transesophageal electrophysiological examination was carried out. Reciprocal paroxysmal tachycardia was revealed in 16 patients (orthodromic form--in 14, antidromic--in 2 patients). Cardiac fibrillation with a cardiac contraction rate of 320-340 per minute was noted in 2 patients. Difficulties are noted in the differential diagnosis of antidromic form with ventricular paroxysmal tachycardia and risk of development of ventricular fibrillation in auricular fibrillation. The authors propose a method of diagnosis of latent forms of the syndrome of premature excitation of the ventricles using short-term pharmacological block of atrioventricular conduction in intravenous administration of ATP.

Treatment of atrial tachyarrhythmias and preexcitation syndrome with flecainide acetate.

Sixteen consecutive patients who had ventricular preexcitation complicated by atrial fibrillation or flutter were treated with intravenous flecainide acetate after treatment with as many as 5 unsuccessful trial regimens with other drugs. In 15 patients who had atrial fibrillation, the shortest RR interval during spontaneous episodes was 210 +/- 39 ms (mean +/- standard deviation), and the average ventricular rate was 208 +/- 37 beats/min. Intravenous flecainide prevented induction of atrial fibrillation in 4 of 9 patients and eliminated anterograde accessory pathway conduction in 9 of the 16 patients. In 5 patients whose atrial fibrillation remained inducible and who continued to have preexcitation, the shortest preexcited RR interval increased from 185 +/- 29 to 281 +/- 46 ms (p less than 0.01). Fourteen patients who had favorable responses to intravenous flecainide were given an oral regimen of the drug. Oral treatment was discontinued early because of proarrhythmic effects in 2 patients, and after 2 1/2 months because of headaches in 1 patient. Eleven patients, 5 receiving concomitant beta-blockade therapy, have continued to receive a regimen of flecainide for a mean of 21 months (range 3 to 48). Seven patients have had no clinical recurrence of arrhythmias. Recurrences in 4 patients have been rare and brief with no changes in therapy required.

Periodic occurrence of premature atrial beats inducing alternation during supraventricular tachycardia in a case of pre-excitation syndrome.

During orthodromic atrioventricular reciprocating tachycardia (AVRT) in a patient with pre-excitation syndrome, 2:1 to 9:1 cycle length alternation was observed. The alternation was induced by the development of premature atrial beats (PABs) recurring in every three to ten AVRT beats. An electrophysiologic study revealed that: 1) PAB developed periodically during atrial/ventricular tachy-pacing (at a rate of 140-170 times/min), during atrial/ventricular extrastimulus study, and during electrically induced AVRT. 2) The PAB had a constant coupling interval to the preceding atrial complex, probably an atrial echo beat, and was associated with no His bundle or ventricular deflection. 3) An intensive search failed to reveal any third ventriculo-atrial conduction pathway. The PABs may have been induced by intra-atrial reentry or by triggered activity in the atrium.

Electrophysiological action of bepridil on atrioventricular accessory pathways.

The electrophysiologic properties of bepridil, a calcium channel blocker with additional effects on fast response tissues, were investigated in 10 patients with atrioventricular accessory pathways. Seven patients had Wolff-Parkinson-White syndrome, and three had concealed atrioventricular pre-excitation. A dose of 4 mg/kg was administered intravenously over five minutes. Bepridil increased the AH interval and the functional refractory period of the atrioventricular node. The effective refractory periods of the right atrium and right ventricle were also increased. Bepridil prolonged refractoriness in the accessory pathway both in the anterograde and retrograde direction. After bepridil administration it was impossible to induce reciprocating tachycardia electrically in two patients because of conduction block in the normal pathway. On the other hand, the zone of tachycardia was often increased after bepridil. Nevertheless, the heart rate during tachycardia was slowed by depression of conduction in both the normal and accessory pathways. The findings of this study provide a basis for the antiarrhythmic action of bepridil in patients with atrioventricular accessory pathways.

Effects of intravenous sotalol in patients with atrioventricular accessory pathways.

Effects of intravenous injection of 0.6 mg/kg sotalol, a beta-blocking agent with additional class III properties, were studied by means of electrophysiologic techniques in 14 patients, seven with the Wolff-Parkinson-White syndrome and seven with concealed atrioventricular (AV) accessory pathways. Sotalol brought about a significant increase in the retrograde effective refractory period of the anomalous pathway, whereas changes in the antegrade effective refractory period were more variable. In five of nine patients with electrically induced reciprocating tachycardia sotalol prevented the initiation of sustained reentry. In most cases the suppression of the circus movement was the result of the development of AV nodal block. Thus our data support the use of sotalol for the treatment of tachycardias incorporating anomalous AV conduction pathways.