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[Ablation of the bundle of His in atrial arrhythmia. A solution when the drugs fail].

Radiofrequency ablation of the bundle of His was performed in 33 patients with intractable atrial arrhythmias (fibrillation in 23, flutter in seven, atrial tachycardia in three). Complete AV block was produced in 30 patients, and clinically satisfactory incomplete block in another two. All were subsequently treated by pacemaker. The ablation was a failure in one patient with hypertrophic cardiomyopathy. Today ablation can be targeted at atrial tachycardias and flutter, and ablative modification of the AV node can reduce ventricular rate in chronic atrial fibrillation. However, His bundle ablation is still the treatment of choice in drug refractory atrial fibrillation when no other measure can provide adequate rate control.

Adult↗

Ibutilide--recent molecular insights and accumulating evidence for use in atrial flutter and fibrillation.

Ibutilide is a 'pure' class III antiarrhythmic drug, used intravenously against atrial flutter and fibrillation. At a cellular level it exerts two main actions: induction of a persistent Na+ current sensitive to dihydropyridine Ca2+ channel blockers and potent inhibition of the cardiac rapid delayed rectifier K+ current, by binding within the channel pore cavity upon channel gating. Ibutilide has been shown to terminate atrial flutter and fibrillation in animal studies, with some risk of ventricular pro-arrhythmia. Experimental models of hypertrophy/heart failure show altered sensitivity to ibutilide, with increased dispersion of repolarisation and incidence of pro-arrhythmia. Patient trials show that ibutilide is effective at terminating atrial arrhythmias when given alone, and that it can increase effectiveness and reduce energy requirements of electrical cardioversion. The risk to patients of polymorphic ventricular tachycardia necessitates careful patient selection and monitoring during and after treatment. An ibutilide analogue, trecetilide, requires further investigation but may offer a less readily metabolised and pro-arrhythmic alternative to ibutilide.

Animals↗

Efficacy of pacing therapies for treating atrial tachyarrhythmias in patients with ventricular arrhythmias receiving a dual-chamber implantable cardioverter defibrillator.

BACKGROUND: Although overdrive pacing for treating atrial flutter is well established, the efficacy of device-based atrial pacing for treating spontaneous atrial tachyarrhythmias in patients with implantable cardioverter defibrillators (ICD) is unknown. This study evaluated the efficacy of novel pacing therapies for treating atrial tachyarrhythmias in patients receiving a dual-chamber ICD to treat ventricular tachyarrhythmias. METHODS AND RESULTS: A Jewel AF ICD was implanted in 537 patients with ventricular arrhythmia who were followed for 11.4+/-8.2 months (74% had a documented history of atrial tachyarrhythmias). The device discriminated atrial tachycardia (AT) from atrial fibrillation (AF) on the basis of cycle length and regularity, and it used 3 different methods of overdrive atrial pacing (Ramp, Burst+, and 50-Hz burst) to treat AT episodes and one method (50-Hz burst) to treat AF episodes. Pacing successfully terminated 59% of 1500 spontaneous AT episodes in 127 patients and 30% of 880 AF episodes in 101 patients (P<0.001). With AT and AF episodes combined, pacing efficacy was 48%. Pacing efficacy was significantly reduced at AT cycle lengths </=220 ms and AF cycle lengths </=160 ms (P<0.01) The median time from pacing to AT/AF termination was 1.1 minute for the pacing successes and 96 minutes for the failures (P<0.001). CONCLUSIONS: Atrial pacing terminated 48% of AT/AF episodes in patients with a history of ventricular arrhythmias. Pacing efficacy was greater for device-classified AT than AF. Pacing efficacy was significantly influenced by tachycardia cycle length. Successful pacing significantly reduces the time required for AT/AF termination.

Aged↗

Surgical treatment of cardiac arrhythmias.

Surgical treatment of cardiac arrhythmias will continue to evolve as advances in understanding of the mechanisms of these arrhythmias and technological developments in the areas of mapping and noninvasive diagnostic capabilities are made. As limitations with many aspects of pharmacological therapy become more apparent, surgical therapies will continue to play a pivotal role in the definitive treatment of these supraventricular and ventricular tachyarrhythmias.

Arrhythmias, Cardiac↗

Modification of supraventricular tachyarrhythmias by stimulating atrial neurons.

The effects of stimulating the right atrial ventral ganglionated plexus on ventricular performance during atrial tachycardia was studied in 8 lightly sedated (pentobarbital, 2.5 mg/kg intravenously) dogs with sterile pericarditis. Atrial arrhythmias were induced by electrical stimulation (10 V, 4 ms, 100 Hz) of the right atrium through previously inserted temporary bipolar pacemaker wires. Various types of supraventricular tachycardias were produced. Atrial fibrillation was produced in 3 dogs, atrial tachycardia in all 8 dogs, different atrioventricular nodal ectopic rhythms in 6 dogs, and atrial flutter in 1 dog. These arrhythmias were associated with irregular ventricular contractions that resulted in low ventricular pressures during many cardiac cycles such that low or no aortic pressure was generated. Right atrial ventral ganglionated plexus stimulation induced slowing of ventricular rate so that every ventricular contraction resulted in aortic pressure generation, thus increasing mean aortic pressure. Responses elicited by atrial ganglionated plexus stimulation were eliminated after atropine administration. We conclude that electrical stimulation of the right atrial ventral ganglionated plexus results in slowing of ventricular contractile rate during supraventricular tachycardia, presumably by activating efferent vagal neuronal elements, thereby improving ventricular performance. If applicable in humans, this technique may be of use in management of postoperative atrial arrhythmias after cardiac operations.

Animals↗

Apparent extension of the atrioventricular interval due to sensor-based algorithm against supraventricular tachyarrhythmias.

Rapid ventricular tracking response to supraventricular tachyarrhythmia is one major limitation to DDD pacing. In a DDDR pacemaker, sensor-based algorithms have been used to control these arrhythmias. These include the use of an interim rate limit (conditional ventricular tracking limit) or a separate maximum tracking and sensor rate limits (discrepant upper rate). These algorithms limit inappropriate ventricular pacing rate during tracking of pathological supraventricular tachyarrhythmia and atrial flutter by Wenckebach-like prolongation of the AV interval. We observed that this may cause an unexpected extension of the AV interval in patients with high atrial rate and intact AV nodal conduction. This was due to P wave rate above the conditional ventricular tracking limit or maximum tracking limit, but AV paced interval prolongation was avoided by the occurrence of intrinsic conduction, albeit at an AV interval longer than the programmed AV interval. This might appear as failure of ventricular pacing on the ECG. This phenomenon is a modified form of "upper rate" behavior occurring in the AV interval, and should be recognized as a normal behavior rather than pacemaker malfunction.

Algorithms↗

[Tachycardia-induced cardiomyopathy, unusual and reversible cause of left ventricular dysfunction: report of 9 cases].

In this study, 9 cases of tachycardia-induced cardiomyopathy have been reported, with a 7-year follow-up period. The patient population consisted of 5 males and 4 females with a mean age of 41 +/- 18 years (range: 10-70 years). It was difficult to determine the onset of the arrhythmia, due to its frequently asymptomatic course until such time as cardiac insufficiency became apparent (this was the case in 7 patients, while 2 subjects had palpitations). Four cases of AV intranodal reentry tachycardia (3 with an accessory pathway), 2 cases of atrial fibrillation, 1 case of auricular flutter, 1 case of atrial tachycardia and 1 case of ventricular tachycardia were observed. Disappearance of the symptomatology following restoration of sinus rhythm was accompanied by echocardiographically-determined normalization of systolic function on average 5 +/- 4 months post-arrhythmia (range: 1-12 months). Left-ventricular end-diastolic volumes decreased from 60 +/- 5 mm to 51 +/- 4 mm (P < 0.01), and end-systolic volumes from 50 +/- 7 mm to 35 +/- 4 mm (P < 0.001), while the left ventricular shortening fraction increased from 17 +/- 5% to 33 +/- 4% (P < 0.0001). In the differential diagnosis for primary dilated cardiomyopathy, tachycardia-induced cardiomyopathy appears very similar to the former, and only an adequate period of follow-up after the restoration of sinus rhythm can confirm the diagnosis.

Adolescent↗

Cooled ablation.

Research on cooled ablation has been evolving for the last 10 years. Findings and current applications are reviewed. A cooled ablation catheter is approved by the FDA for use in idiopathic ventricular tachycardia (VT) patients, based on data originally submitted by Cardiac Pathways, Inc. This technology has subsequently been used by the clinicians in atrial flutter cases, nonischemic VT, epicardial accessory pathways, and atrial fibrillation. The experience at Johns Hopkins suggests that cooled radiofrequency ablation has utility in a variety of situations and in some instances has come to be the ablation system of choice.

Atrial Flutter↗

Follow-up of radiofrequency catheter ablation in children: results in 100 consecutive patients.

OBJECTIVES: The purpose of this study was to determine the outcome of a group of closely followed-up pediatric patients who had undergone radiofrequency ablation for cardiac arrhythmias. BACKGROUND: Although radiofrequency ablation in children has been shown to be effective and safe in the short term, results of longer term follow-up of these children must be considered when determining the place of radiofrequency ablation in the management of pediatric arrhythmias. METHODS: One hundred children aged 2 months to 17 years underwent a total of 119 radiofrequency ablation procedures for cure of tachycardia. Follow-up clinical data, electrocardiograms and 24-h Holter monitors were obtained and analyzed. RESULTS: All patients were alive, and none were lost to follow-up after a mean follow-up of 21.5 months (range 6 to 50). Success at last follow-up included accessory pathways in 66 (89%) of 74 patients, atrioventricular (AV) node reentry in 15 (88%) of 17, intraatrial reentry in 2 (67%) of 3, atrial flutter in 3 (100%) of 3, atrial ectopic tachycardia in 2 (67%) of 3, junctional ectopic tachycardia in 1 (100%) of 1 and ventricular tachycardia in 2 (100%) of 2 (overall success, 90 [90%] of 100). All recurrences were observed within 6 months of ablation. Major and minor complications (7%) included chest burn (one patient), foot microembolus (two patients), hematoma without pulse loss (four patients), femoral arteriovenous fistula requiring repair (one patient) and transient Mobitz I AV block (one patient). Immediate success, recurrence and complication rates were similar in the > or = 12-year old versus the < 12-year old group. Echocardiograms, available in 109 (92%) of 119 patients, showed possible procedure-related abnormalities in 2 (mitral regurgitation in 1, tricuspid regurgitation in 1, both mild), with no aortic insufficiency after 30 left-sided ablations performed by the retrograde approach. Follow-up Holter monitors, available in 77 (77%) of 100 patients, showed possible procedure-related abnormalities in 5 (frequent atrial ectopic tachycardia in 2, atrial flutter in 1, accelerated ventricular rhythm in 2). There were no early or late deaths. CONCLUSIONS: In children, the risks of radiofrequency ablation are low at follow-up evaluation. Longer-term follow-up of children undergoing radiofrequency ablation will be necessary to determine whether coronary abnormalities or serious new arrhythmias will develop.

Adolescent↗

[Hypertrophic myocardiopathy (II). 24-hour electrocardiographic monitoring and its relation to the echocardiographic characteristics].

Seventy-two patients with hypertrophic cardiomyopathy were evaluated by 24 hours of electrocardiographic ambulatory monitoring. The results were related to echocardiographic extent of hypertrophy, left ventricular outflow obstruction at rest, and transmitral flow parameters. Also, the symptoms and functional classification of NYHA were related to ventricular arrhythmias. Ventricular arrhythmias were detected in 68% of our patients: high degree of ventricular ectopia in 26 (36.1%), and ventricular tachycardia in 14 (19.4%). Most important supraventricular arrhythmias were: atrial fibrillation in 7 patients, atrial flutter in one, and supraventricular tachycardia in five. Asymmetric hypertrophy type I of Maron classification showed the lower number of ventricular arrhythmias. High degree of ventricular arrhythmias were more frequent in patients with: apical hypertrophy, worse functional classification of NYHA (I: 20%; II: 50%; III: 80%), and in patients with impaired distensibility detected by Doppler (80.7% vs 56.7%; p less than 0.05). There was no relationship between left ventricular outflow obstruction at rest and ventricular arrhythmias.

Adolescent↗

Thromboembolism following cardioversion of "common" atrial flutter. Risk factors and limitations of transesophageal echocardiography.

Based on multiple recent studies, anticoagulant therapy is recommended prior to elective cardioversion for patients with atrial fibrillation of more than 24 h duration. The value of anticoagulation in patients with atrial flutter, however, is less well established. Published recommendations for pericardioversion anticoagulation of atrial fibrillation often do not extend to patients with atrial flutter. We evaluated the risk of thromboembolism in our patient population undergoing cardioversion for atrial flutter. Over a period of 30 months, clinically indicated electrical cardioversions were performed in 41 patients with "common" atrial flutter. Sixteen of these patients underwent transesophageal echocardiograms immediately prior to cardioversion to exclude a left atrial thrombus. Three of the 41 patients with atrial flutter developed neurologic ischemic syndromes within 48 h of elective cardioversion. All three patients who developed ischemic neurologic complications had undergone transesophageal echocardiography immediately prior to cardioversion and did not have any evidence of left atrial clot. One patient had cardiomyopathy and the other two had left ventricular hypertrophy. Thus, electrical cardioversion without anticoagulation in patients with atrial flutter and associated heart disease is associated with a risk of thromboembolic events. A normal transesophageal echocardiogram is of doubtful value in prevention of thromboembolic complications.

Aged↗

Anti-arrhythmic agents in ischemic heart disease: supraventricular arrhythmias, digitalis toxicity and chronic stable ventricular ectopic beats.

Digoxin remains a very useful agent for chronic atrial fibrillation or for the ectopic beats associated with heart failure. But when rapid control of the ventricular rate is required to arrhythmias such as atrial fibrillation, atrial flutter, or paroxysmal atrial tachycardia, a slow infusion of verapamil is the agent of choice. In general, verapamil may be added to digoxin or given intravenously while a digoxin effect is awaited, unless there is digitalis toxicity. In digitalis toxicity, lignocaine remains the agent of choice for ventricular arrhythmias, and is given in the same doses as for acute myocardial infarction; phenytoin is used for digitalis-arrhythmias with A-V block. Verapamil may be infused very cautiously for digitalis-induced supraventricular tachyarrhythmias. The use of oral agents such as quinidine, disopyramide and mexilitene for chronic prophylaxis of ventricular ectopic beats is of doubtful effectiveness, unless the ectopic activity is symptomatic. Serious ventricular arrhythmias may be induced by quinidine and disopyramide. Beta-blockade is especially useful for ectopic beats associated with anxiety, or when arrhythmias are associated with angina of effort or hypertension. As always, major contraindications to the use of beta-blockade include cardiomegaly, heart failure or asthma.

Aged↗

[Cibenzoline versus propafenone by the oral route for preventing recurrence of atrial arrhythmia: multicenter, randomized, double-blind study].

This multicentre, randomized, double-blind study, conducted in parallel groups, was designed to compare the efficacy and safety of cibenzoline (C) and oral propafenone (P) in the prevention of recurrent atrial arrhythmias (M) over a 6-month period. Patients of either sex with reduced atrial fibrillation or flutter and predominantly in sinus rhythm (> 50%), with a left ventricular shortening fraction greater than or equal to 20% and not receiving any antiarrhythmic treatment were included. Patients presenting severe conduction disorders, severe heart failure (NYHA class III or IV), marked hypotension or recent myocardial infarction were not included. Treatments were administered at the dosage of one tablet twice a day, i.e. 260 mg/day of cibenzoline or 600 mg/day of propafenone. This dosage was reduced by one half in elderly patients (> 70 years). Patients were seen on inclusion (Dzero), and at the third and sixth months or in the case of recurrence of symptoms. Recurrent arrhythmias were assessed by ECG and 24-hour Holter monitoring and according to the symptoms experienced by the patients. Sixty-five patients, 36 men and 29 women, between the ages of 34 to 86 years and presenting an atrial arrhythmia-atrial fibrillation (80%) or atrial flutter (20%)-were included in the trial: 34 patients received cibenzoline and 31 received propafenone. The arrhythmia had already been treated in 78% of cases. Its aetiology was related to hypertensive heart disease (32%), valvular heart disease (8%), other (17%) or idiopathic (43%). The arrhythmia was symptomatic in 91% of patients on inclusion. The ultrasonographic left ventricular shortening fraction was 32.8 +/- 8.1% in group C and 32.6 +/- 6.4% in group P. The two groups were comparable before treatment. The efficacy of the two treatments was comparable: no significant difference in the number of recurrences was demonstrated: 11 patients treated with C and 12 patients treated with P; cumulative percentages of patients without recurrence with good tolerance of treatment (Kaplan-Meier acturial curves) at 6 months were 55.9% with C and 48.4% with P(NS); probability of no recurrence at 6 months (0.63 +/- 0.09 in group C and 0.57 +/- 0.09 in group P); mean time to recurrence (53.4 +/- 44.3 days in group C and 61.6 +/- 35.3 days in group P). Adverse events leading to discontinuation of treatment occurred in 4 patients from each group, and one proarrhythmic effect at 6 months in a patient in group P. The treatments were well tolerated in the majority of cases: there was no significant difference in the number of patients presenting at least one adverse event: 9(26.5%) in group C, 11(35.5%) in group P. Most events were considered to be mild or moderate. The effects of the two treatments on the course of blood pressure, heart rate, PR interval and QT interval calculated at 3 and 6 months compared to DO were not statistically different. The QRS interval increased to a significantly greater extent in group C that in group P (p = 0.02 at 3 months; p = 0.0005 at 6 months). No significant difference was observed between the two groups for the course of laboratory parameters at 3 and 6 months compared to DO in the patients present at these three visits. Cibenzoline can therefore constitute a good alternative to propafenone in the prevention of symptomatic recurrences of atrial tachyarrhythmias. The preferential use of one or other treatment can be guided by individual factors, including tolerance.

Administration, Oral↗

Cardiac arrhythmias and conduction disturbances in autoimmune rheumatic diseases.

Rhythm and conduction disturbances and sudden cardiac death (SCD) are important manifestations of cardiac involvement in autoimmune rheumatic diseases (ARDs). In patients with rheumatoid arthritis (RA), a major cause of SCD is atherosclerotic coronary artery disease, leading to acute coronary syndrome and ventricular arrhythmias. In systemic lupus erythematosus (SLE), sinus tachycardia, atrial fibrillation and atrial ectopic beats are the major cardiac arrhythmias. In some cases, sinus tachycardia may be the only manifestation of cardiac involvement. The most frequent cardiac rhythm disturbances in systemic sclerosis (SSc) are premature ventricular contractions (PVCs), often appearing as monomorphic, single PVCs, or rarely as bigeminy, trigeminy or pairs. Transient atrial fibrillation, flutter or paroxysmal supraventricular tachycardia are also described in 20-30% of SSc patients. Non-sustained ventricular tachycardia was described in 7-13%, while SCD is reported in 5-21% of unselected patients with SSc. The conduction disorders are more frequent in ARD than the cardiac arrhythmias. In RA, infiltration of the atrioventricular (AV) node can cause right bundle branch block in 35% of patients. AV block is rare in RA, and is usually complete. In SLE small vessel vasculitis, the infiltration of the sinus or AV nodes, or active myocarditis can lead to first-degree AV block in 34-70% of patients. In contrast to RA, conduction abnormalities may regress when the underlying disease is controlled. In neonatal lupus, 3% of infants whose mothers are antibody positive develop complete heart block. Conduction disturbances in SSc are due to fibrosis of sinoatrial node, presenting as abnormal ECG, bundle and fascicular blocks and occur in 25-75% of patients.

Arrhythmias, Cardiac↗

Recurrence rates of arrhythmias during pregnancy in women with previous tachyarrhythmia and impact on fetal and neonatal outcomes.

In women with heart disease, sustained arrhythmias can result in an increased risk to the mother and fetus. The purpose of this study was to determine the recurrence rates of arrhythmias during pregnancy in women with cardiac rhythm disorders and examine the impact on fetal and neonatal outcomes. Women with tachyarrhythmias before pregnancy who underwent obstetric care at the Toronto General and Mount Sinai Hospitals from 1990 to 2002 were included. The recurrence rates of arrhythmias were calculated. A multivariate logistic model was used to identify predictors of fetal complications. Seventy-three women had 87 pregnancies; 36 pregnancies were in women with a history of paroxysmal supraventricular tachycardia, 23 with paroxysmal atrial fibrillation or atrial flutter (AF/Afl), 6 with persistent AF/Afl, and 22 with ventricular tachycardia. In the women in sinus rhythm at baseline, 44% (36 of 81 pregnancies) developed recurrences of tachyarrhythmias during pregnancy or in the early postpartum period. The specific recurrence rates during pregnancy in women with a history of supraventricular tachycardia, paroxysmal AF/Afl, and ventricular tachycardia were 50%, 52%, and 27%, respectively. The 6 women in AF/Afl at baseline remained in this rhythm throughout their pregnancy. Adverse fetal events occurred in 17 of the 87 pregnancies (20%). Adverse fetal events occurred more commonly in women who developed antepartum arrhythmias (RR 3.4, 95% confidence interval 1.0 to 11.0, p = 0.045) compared with those who did not. In conclusion, in women with preexisting cardiac rhythm disorders, exacerbation of arrhythmia during pregnancy is common. Recurrence of arrhythmia during the antepartum period increases the risk of adverse fetal complications, independent of other maternal and fetal risk factors.

Adult↗

A benefit-risk assessment of class III antiarrhythmic agents.

With beta-blockers as the exception, increasing doubt is emerging on the value of antiarrhythmic drug therapy following a series of trials that have either shown no mortality benefit or even an excess mortality. Vaughan Williams class I drugs are generally avoided in patients with structural heart disease, and class IV drugs are avoided in heart failure. Unfortunately, arrhythmias are a growing problem due to an increase in the incidence of atrial fibrillation and sudden death. The population is becoming older and more patients survive for a longer time period with congestive heart failure, which again increases the frequency of both supraventricular as well as ventricular arrhythmias. Class III antiarrhythmic drugs act by blocking repolarising currents and thereby prolong the effective refractory period of the myocardium. This is believed to facilitate termination of re-entry tachyarrhythmias. This class of drugs is developed for treatment of both supraventricular and ventricular arrhythmias. Amiodarone, sotalol, dofetilide, and ibutilide are examples of class III drugs that are currently available. Amiodarone and sotalol have other antiarrhythmic properties in addition to pure class III action, which differentiates them from the others. However, all have potential serious adverse events. Proarrhythmia, especially torsade de pointes, is a common problem making the benefit-risk ratio of these drugs a key question. Class III drugs have been evaluated in different settings: primary and secondary prevention of ventricular arrhythmias and in treatment of atrial fibrillation or flutter. Based on existing evidence there is no routine indication for antiarrhythmic drug therapy other than beta-blockers in patients at high risk of sudden death. Subgroup analyses of trials with amiodarone and dofetilide suggest that patients with atrial fibrillation may have a mortality reduction with these drugs. However, this needs to be tested in a prospective trial. Similarly, subgroups that will benefit from prophylactic treatment with class III antiarrhythmic drugs may be found based on QT-intervals or - in the future - from genetic testing. Class III drugs are effective in converting atrial fibrillation to sinus rhythm and for the maintenance of sinus rhythm after conversion. This is currently by far the most important indication for this class of drugs. As defined by recent guidelines, amiodarone and dofetilide have their place as second-line therapy except for patients with heart failure where they are first line therapy being the only drugs where the safety has been documented for this group of high risk patients.

Action Potentials↗

Cardiac disturbances in thyrotoxicosis: diagnosis, incidence, clinical features and management.

In the present paper we studied 403 patients with different etiopathogenic and clinical forms of thyrotoxicosis: toxic multinodular goiter (36.7%), toxic adenoma (4.9%), Graves' disease (27.04%), transient thyrotoxicosis (subacute thyroiditis, painless thyroiditis, Hashitoxicosis) (21.09%), T3-thyrotoxicosis (9.42%), thyrotoxicosis factitia (0.74%). Eighty-seven patients (21.5%) had cardiac disturbances. The following arrhythmias were most common: atrial fibrillation (4.00%), ventricular premature beats (2.77%), paroxysmal supraventricular tachycardia (2.23%), atrial flutter (1.00%). Congestive heart failure occurred in 10.42% of the cases. Paroxysmal tachyarrhythmias were converted to sinus rhythm in 90% of the subjects, by a selected and sustained treatment: drug therapy (carbimazole 30-40 mg/day, Lugol solution 1/2/20, 10-15 drops/day, beta-adrenergic blockers (propranolol--60-120 mg/24 hrs), calcium channel blockers (verapamil--40-60 mg/24 hrs), cardiac glycosides (deslanosid) or DC cardioversion. In order to prevent recurrences and/or complications, drug therapy was subsequently completed with subtotal thyroidectomy or radioactive iodine (131I) therapy. Thus, we succeeded in maintaining the patients in a euthyroid state, in sinus rhythm and with an adequate cardiovascular function in 95.4% of the cases.

Adult↗

[Verapamil in the study and treatment of supraventricular tachycardias, with special reference to pre-excitation].

Verapamil is a novel antiarrhythmic agent which appears to act as a calcium-ion antagonist, blocking calcium transport across the myocardial cell membrane. It was given intravenously, in a dose of 10 mg, to thirty-two patients suffering from paroxysmal supraventricular tachycardia, and sinus rhythm was achieved promptly in all. Identical results were obtained in a further ten patients with supraventricular tachycardias associated with the Wolff-Parkinson-White or other pre-excitation syndromes. In a separate group of eighteen patients in whom A-V junctional tachycardias were induced during intracardiac electrography, conversion to sinus rhythm was achieved in fifteen patients, with prolongation of the cycle length in the others. Circus-movement tachycardias were induced in eight patients with the Wolff-Parkinson-White syndrome, and conversion to sinus rhythm was achieved in seven. The results were less consistent in patients with other supraventricular arrhythmias including ectopic atrial tachycardia and atrial flutter, and, in the single patient with supraventricular and ventricular tachycardias, only the former was controlled. In the single patient with atrial fibrillation complicating the wolff-Parkinson-White syndrome who received Verapamil, sinus rhythm was restored. Side effects were few and mild, with rare exceptions of profound hypotension, bradycardia and asystole; their management is discussed, and reasons are advanced why their occurrence is likely to be related either to the concomitant administration of beta-adrenergic blockers or to the presence of sinoatrial disease. It appears that Verapamil is particularly suitable for the treatment of supraventricular tachycardias due to a circus movement as calcium antagonism is likely to be most effective in the N region of the atrioventricular node.

Adrenergic beta-Antagonists↗