[Atrial fibrillation]. / Fibrilación atrial.

Atrial fibrillation (AF) is the most common sustained arrhythmia. AF has now been exhaustively studied: more is known about its mechanism and research is moving towards new forms of treatment. For chronic AF, basically the control of ventricular rate and the brain protection are the main issues. It is well known that with the identification of high risk group for embolism, oral anticoagulation should be administered. Ventricular rate control can be achieved by using betablockers or calcium channel blockers, unless these are contraindicated for the elderly. Oral anticoagulation prevents the stroke. The main mechanism of AF is the re-entry of multiple wavelets, but now it is more frequently found on patients with focal AF. Therapies are employed to bring the patient to a sinusal rhythm as soon as possible with antiarryhthmics or electric cardioversion externally or internally. The internal procedure includes 1 to 15 J and the success rate is of 91% vs 67% in relation to the external one. The introduction of the catheter ablation has opened new frontiers for the treatment of AF, first as the ablate-and-pace technique and now trying to mimic the maze procedure or with the ablation of the focal tachycardia. The stimulation for prevention of AF under research, as well as the implantable dysfibrillation for selected patients. On going studies will show the possible benefit of this type of benefits.

[Electrocardiographic changes during stress test in a patient with "Brugada syndrome"]. / Alteraciones electrocardiográficas durante el esfuerzo en un paciente con "síndrome de Brugada".

We report a 28 year old man with the Brugada syndrome characterised by an electrocardiographic pattern of a right bundle branch block and an ST segment elevation in the right precordial leads as well as syncope. During an exercise test, we observed a normalization of the ST segment in V2+ while in the postexercise phase, the ST segment elevation in the right leads was established. This is the first case reported of the Brugada syndrome in Mexico, with spontaneous changes on the EKG masked during exercise and apparent during postexercise phase.

[Ventricular tachycardia associated with isolated right ventricular dysfunction as indicator of arrhythmogenic dysplasia of the right ventricle]. / Taquicardia ventricular asociada a disfunción del ventrículo derecho aislada como indicador de displasia arritmogénica del ventrículo derecho.

We report the case of a 21 year-old patient with arrhythmogenic right ventricular dysplasia manifested by episodes of QRS tachycardia greater than 0.12 sec and isolated dysfunction of the right ventricle. The patient treated with amiodarone however, the tachycardia episodes persisted. The surface electrocardiogram showed left branch block with the axis down, which suggested a right ventricle origin, and was therefore considered an arrhythmogenic dysplasia. Echocardiography and cardioangiography showed alterations in the anatomy of the outflow tract of the right ventricle. A myocardial gammagraphy revealed no perfusion alterations. The endomyocardial biopsy showed perivascular fibrosis. An electrophysiology study was performed, stimulating the outflow tract of the right ventricle, which induced two types of ventricular tachycardias, one of them identical to that recorded clinical. The patient was treated with sotalol, and has been being free of ventricular tachycardia episodes for 18 months of follow-up. We consider that this entity should be studied in a systematic way in those patients with ventricular tachycardia originated in the outflow of the right ventricle and with primary cardiac illness.

[Experience in 1,500 patients undergoing radiofrequency ablation in the treatment of tachycardias]. / Experiencia en 1,500 pacientes sometidos a ablación con radiofrecuencia en el tratamiento de las taquicardias.

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular and ventricular tachycardias. This report details the results of radiofrequency catheter ablation in 1500 consecutive patients with a wide variety of supraventricular and ventricular tachycardias treated in the Instituto Nacional de Cardiología "Ignacio Chavez", between April 22, 1992 until December of 1999. Tachycardias were associated with the presence of an accessory pathway in 987 patients (65.8%). Dual accessory pathways were present in 24 patients giving a total of 1,012 accessory pathways. The mechanism of the arrhythmia was atrioventricular nodal reentrant tachycardia in 321 patients (21.4%). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 109 (7.2%) patients and a primary atrial tachycardia in 13 patients (0.8%). Atrioventricular node ablation and permanent pacemaker implantation were performed in 26 patients (1.7%). Finally we performed radiofrequency catheter ablation in 37 (2.4%) patients with ventricular tachycardia. Radiofrequency catheter ablation was successful in 908 of 1012 (89.7%) patients with accessory pathways with a complication rate of 10 (0.98%) and a recurrence rate of 92 (9%). AV nodal reentry was successfully abolished in 319 of 321 patients by selective ablation of the slow pathway in 297/321 (92.5%) patients and the fast pathway in 22/24 (92%) patients. The complication rate of this group was 8/321 (2.4%) with a recurrence rate of 34 patients (10.5%). The reentrant circuit of atrial flutter was ablated successfully in 86 of 109 (76.8%) patients with a recurrence flutter in 14 (12.8%) patients. Five of 13 (38.4%) cases of primary atrial tachycardia were successfully ablated. Complete AV block was achieved in 26 of 26 (100%) patients with atrial fibrillation or flutter treated by AV nodal ablation. The procedure was successful in 28 of 37 (75.6%) patients with fascicular ventricular tachycardia. The results of this series of patients demonstrates the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of taquicardias with high rate of success 1375 of 1500 patients (91.6%), with 142 recurrences (9.4%), 15 complications (1%), and no mortality.

[Radiofrequency ablation in the treatment of tachyarrhythmias. Experience concerning 1,000 consecutive patients]. / Ablación con radiofrecuencia en el tratamiento de las taquiarritmias. Experiencia en 1000 pacientes consecutivos.

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of tachyarrhythmias. This report details the results of radiofrequency catheter ablation in 1,000 consecutive patients with a wide variety of tachyarrhythmias treated in the Instituto Nacional de Cardiología "Ignacio Chavez". Tachyarrhythmias were associated with the presence of an accessory pathway in 700 patients (70%). Dual accessory pathways were present in 21 patients, giving a total of 722 accessory pathways. The mechanism of the arrhythmia was AV nodal reentrant tachycardia in 204 patients (20.4%). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 56 (5.6%) patients and a primary atrial tachycardia in five patients (0.5%). AV node ablation and permanent pacemaker implantation were performed in 17 patients (1.7%). Finally we performed radiofrequency catheter ablation in 22 (2.2%) patients with ventricular tachycardia. Radiofrequency catheter ablation was successful in 630 of 700 (90%) patients with accessory pathways with a complication rate of 9/700 (1.2%) and a recurrence rate of 73 (12.4%). AV nodal reentry was successfully abolished in 190 of 204 (93%) patients by selective ablation of the slow pathway in 168/180 (93.3%) patients and the fast pathway in 22/24 (92%) patients. The complication rate of this group was 7/204 (3.4%) with a recurrence rate of 30 patients (14.2%). The reentrant circuit of atrial flutter was ablated successfully in 41 of 56 (73%). Four/five (80%) of patients with primary atrial tachycardia were successfully ablated. Complete AV block was achieved in 17/17 patients with atrial fibrillation or flutter treated by AV nodal ablation without complications or recurrence. The procedure was successful in 17/22 (77%) of patients with ventricular tachycardia. The results of this series of patients demonstrate the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of tachyarrhythmias with high rate of success 899/1,000 (89.9%) and with an 1 1.8% of recurrence, low risk of complications (1.5%) and no mortality.

[The familial incidence of accessory atrioventricular pathways (the pre-excitation syndrome)]. / Frecuencia familiar de vías accesorias atrioventriculares (síndrome de preexcitación).

Cases of familial preexcitation syndrome represent a specific subgroup of patients that may result from diverse mechanisms: failure in development and genetic predisposition are the main mechanism involved. We determined the prevalence of this syndrome in first degree relatives of patients with proved accessory pathways by electrophysiologic study and compared such prevalence with the general population (0.15%). In five out of 469 patients (1.06%) we found an accessory pathway in one or more member of their family. Only 6 out of 3752 had preexcitation (0.15%); this prevalence was similar to the general population (P = NS). The identification of family members with this syndrome may be incomplete because we only chose for the study symptomatic patients. We did not observed multiple pathways and in one case we found atrial septal defect. Our data demonstrated familial preexcitation in five families suggesting hereditary predisposition.

[Double tachyarrhythmia: left anterior fascicular ventricular tachycardia associated with atrial flutter and fibrillation. Report of a case]. / Doble taquiarritmia: taquicardia ventricular fascicular anterior izquierda asociada a fibrilación y flutter auriculares. Reporte de un caso.

A patient with episodes of palpitation in whom the electrocardiogram showed a right bundle branch (RBBB) configuration and right axis deviation underwent electrophysiologic study and radiofrequency ablation. Left ventricular endocardial mapping during ventricular tachycardia (VT) identified the earliest ventricular activation in the anterolateral wall of the left ventricle. The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 47 mseg, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. The stimulus to QRS time was equal to the Purkinje potential-QRS time. Several radiofrequency lesions were applied in this region, one of them resulted with termination of the tachycardia. Following delivery of this lesion the ventricular tachycardia couldn't be induced either at baseline or during isoproterenol infusion. During VT, atrial fibrillation and atrial flutter were observed, cardioversion was performed reverting to sinus rhythm.

[Radiofrequency ablation in the treatment of supraventricular arrhythmias in pediatrics. Experience with 203 consecutive patients]. / Ablación con radiofrecuencia en tel tratamiento de las arritmias supraventriculares en pediatría. Experiencia en 203 Pacientes consecutivos.

We report the results of radiofrequency catheter ablation in 203 patients under 18 years of age with supraventricular tachyarrhythmias between April 1992 and June 1997. The presence of an accessory pathway caused the tachyarrhythmia in 181 patients (89.1%) with a total of 187 accessory pathways; atrioventricular nodal reentry caused the arrhythmia in 18 patients (8.8%) and atrial flutter in only 4 patients (1.9%). We eliminated the accessory pathway in 171 patients (91.4%), 23 patients showed recurrence of the tachycardia and we had complications in 4 patients (2.1%). The procedure was successful in the treatment of the atrioventricular nodal reentry in the 18 cases, with ablation of the slow pathway in 17 cases and in only one patient of the fast pathway, one patient showed total A-V block, and recurrence of the arrhythmia in 3 cases (16.6%). Finally the procedure was successful in the 4 cases of atrial flutter with one recurrence (25%). In the total of the series, the radiofrequency catheter ablation was successful in 193 patients (95%), with recurrence of the arrhythmia in 27 cases (13.3%) and with complications in only 5 patients (2.6%). Radiofrequency catheter ablation is a safe and effective procedure for the definitive treatment of supraventricular tachyarrhythmias in children.

[Radiofrequency ablation of accessory pathways in the presence of atrial fibrillation]. / Ablación con radiofrecuencia de vías accesorias en presencia de fibrilación auricular.

Radiofrequency catheter ablation was performed in 595 consecutive patients with Wolff-Parkinson-White syndrome. We attempted ablation of right and left accessory pathways, during sustained atrial fibrillation with rapid anterograde conduction over the accessory pathway in three patients. In other patient, who had an accessory pathway with anterograde decremental conduction properties, referred to as Mahaim atriofascicular fiber, originating from the right posterolateral atrium, who also had sustained atrial fibrillation during the electrophysiological study to assess accessory pathway conduction properties, was also submitted to ablation of the accessory pathway. At the successful ablation sites, a ventricular electrogram was consistently recorded preceding the onset of preexcitation, in the surface electrogram by 20 ms, during atrial fibrillation. All patients were successfully ablated with a single radiofrequency impulse. After successful ablation direct current cardioversion with 200 joules terminated the atrial fibrillation. In conclusion, radiofrequency catheter ablation of accessory pathways during sustained atrial fibrillation is feasible with a high success rate.

[Usefulness of exercise test in programming dual chamber pacemakers]. / Utilidad de la prueba de esfuerzo en la programación de los marcapasos bicamerales.

Prospectively, we studied 42 patient to evaluate the usefulness of treadmill exercise to programme pacemaker DDD in relation to the functioning upper frequency (relation between block frequency of pacemaker and the upper rate frequency). We excluded patient who had no treadmill exercise test after implant pacemaker. During stress 7 (17%) patient presented AV conduction 1:1 (group I); 16 (38%) second degree AV block type Wenckebach (group II); 14 (33%) second degree AV block 2:1 (group III); and 5 (12%) showed inhibition of the pacemaker by intrinsic activity (group IV). Block frequency of the pacemaker in group I and II was superior in regard of the upper rate frequency, 156.85 +/- 22.16 vs 141.43 +/- 20.82 and 135.25 +/- 11.54 vs 121.25 +/- 5.9, respectively. In group III and IV, it was lower, 120.36 +/- 15.31 vs 138.57 +/- 13.29 and 121.0 +/- 7.38 vs 142.0 +/- 14.39. The comparative analysis of the block frequency of the pacemaker in relation with the upper rate frequency showed statistically significant differences (p < 0.05) between groups I and II, and between the group I and III. The appearance of second degree AV block 2:1 is nonphysiologic, is rather due to an abrupt falling in the cardiac output. This phenomenon is able to be predicted and corrected by programming with the use the telemetry with parameters as the AV delay, as well as upper rate frequency and post-ventricular refractory atrial period.

[Radiofrequency ablation in multiple accessory pathways]. / Ablación con radiofrecuencia en vías accesorias múltiples.

Radiofrequency ablation were performed in 465 consecutive patients with Wolff-Parkinson-White syndrome. We demonstrated evidence of multiple accessory pathways in 18 patients (3.9%); 17 had two, and one had three accessory pathways. In three of these there was additional right atrio-fascicular connection. There were 27 manifest and 10 concealed accessory pathways. Six patients had Ebstein's anomaly associated with accessory pathways. The location of the accessory pathways was in the right posterior portion of the ventricular septum in 16, the left posterior portion of the ventricular septum in 5, the right free wall in 5, the left wall in 7, the right anteroseptal in 3, the midseptum in 1, and one right anterolateral. Of the 37 pathways, 32 (86%) accessory pathways were ablated successfully without complications. Duration of the procedure was 100 +/- 58 minutes, and fluoroscopic time 40 +/- 17 minutes. The mean applications were 26 +/- 17 and the power level of the radiofrequency current 41 +/- 6 W. A follow-up of 80 +/- 40 days after ablation demonstrated incidence of recurrent conduction in 3 accessory pathways (8%). In conclusion, patients with multiple accessory pathways can be treated by radiofrequency ablation in a single session with a high success rate although slightly less than that in patients with a single accessory pathway.

[Ablation using radiofrequency in the treatment of ventricular tachycardia]. / Ablación con radiofrecuencia en el tratamiento de la taquicardia ventricular.

We performed radiofrequency catheter ablation in 14 consecutive patients with Ventricular Tachycardia (VT) 10 of which had healthy hearts, one patient with ischemic heart disease, one with arrhythmogenic dysplasia, one with dilated cardiomyopathy, and one with congenital heart disease. The localization of the VT was: 10 in the left posterior fascicular region, 3 in the right ventricular outflow tract (RVOT), and one patient with ischemic heart disease with the substrate in the left ventricular apex. All of them with VT refractory to pharmacological management, using an average of 2.7 drugs per patient. After all patients underwent Electrophysiological Study (EPS), an intracavitary mapping was performed, in order to locate the arrhythmogenic substrate. Later on, the RF ablation was performed, delivering an average of 15 pulses, using 40 Watts, and an average time of 25 sec. per pulse. The procedure was successful in 60% of the fascicular VT, with a 16% of recurrence; 100% of success with those originated in the RVOT with no recurrence; in the ischemic patient we achieved primary success, but with recurrence, a second session was successful with no recurrence up to date. No major complications occurred in this group. Those patients which showed no success required the use of antiarrhythmic drugs. The total success of the series is 71.4% with 10% recurrence, and no mortality.

[Radiofrequency ablation in the treatment of supraventricular tachyarrhythmia. Experience with 500 consecutive patients]. / Ablación con radiofrecuencia en el tratamiento de las taquiarritmias supraventriculares. Experiencia en 500 pacientes consecutivos.

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular tachyarrhythmias. This report details the results of radiofrequency catheter ablation in 500 consecutive patients with a wide variety of supraventricular tachycardia treated at the Instituto Nacional de Cardiología "Ignacio Chaávez". Tachyarrhythmias were associated with the presence of an accessory pathway in 355 patients (71%). The accessory pathways were capable of both anterograde and retrograde conduction in 220 of cases (60%), only retrograde conduction in 146 (40%), dual accessory pathways were present in 11 patients (2.2%) giving a total of 366 accessory pathways. The mechanism of the arrhythmia was AV nodal reentrant tachycardia in 115 patients (23%). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 15 (15%) patients and a primary atrial tachycardia in 3 patients (0.7%). AV node ablation and permanent pacemaker implantation were performed in 11 patients (2%). Radiofrequency catheter ablation was successful in 312 of 355 (87.9%) patients with accessory pathways 312 of 366 (85.2%) pathways with a complication rate of 6/355 (2%) and a recurrence rate of (12.4%). AV nodal reentry was successfully abolished in 110 of 115 patients by selective ablation of the slow pathway in 92/96 (95.8%) patients and the fast pathway in 18/19 (94.7%) patients. The complication rate of this group was 7/115 (6.0%) with a recurrence rate of 16 patients (12%). The reentrant circuit of atrial flutter was ablated successfully in 13 of 15 patients with recurrent atrial flutter in (27%) patients. 2/3 (66%) primary atrial tachycardia were successfully ablated. Complete AV block was achieved in 11 of 11 patients with atrial fibrillation or flutter treated by AV nodal ablation without complications or recurrence. The results of this series of patients demonstrates the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of supraventricular arrhythmias with high rate of success and low risk of complications.

[Transtelephonic electrocardiography in Mexico. A report of the first 3434 cases]. / La electrocardiografía transtelefónica en México. Reporte de los primeros 3434 casos.

The transtelephonic electrocardiographic system started in the 70's and it was used mainly in the study of heart disease, cardiac arrhythmias, syncope and sudden death. This report, include 3434 electrocardiogram (ECG) of patients whom visit the emergency room at the General Hospital and private clinic, using three different forms of transtelephonic monitors. The total population were 1715 males and 1719 females with average age of 52.2 +/- 28.8 years. 26.9% had was present in history of systemic hypertension, non-insulin dependent diabetes 12.3% and myocardial ischemic disease in 5.3%. The main ECG indications were chest pain 38.7%, most of them atypical angina, palpitations in 6.9% and dyspnea in 6.5%. 50.1% of the ECG were abnormal. The most important diagnosis were: tachyarrhythmias (25.2%), intraventricular conduction abnormalities (17.7%), myocardial ischemic disease (16%), and premature ventricular and supraventricular beats (11.6%). We concluded that the transtelephonic electrocardiographic system is a very useful method, and available now in Mexico. We detected a high percentage of electrocardiographic abnormalities, it was possible to give the right diagnosis of arrhythmias, acute myocardial infarction, old infarction, and to evaluate the pacemaker functionality. Finally, it helped to get in brief time the diagnosis and treatment in cases of acute myocardial infarction or severe arrhythmias.

[Auricular flutter associated with an interatrial septal aneurysm submitted to radiofrequency ablation]. / Flutter auricular asociado a un aneurisma del septum interatrial, sometido a ablación con radiofrecuencia.

We present the case of a young man who began with type I atrial flutter, he had no response to antiarrhythmic drugs. The echocardiogram showed an atrial septal aneurysm in the region of the fossa ovalis. We performed an electrophysiologic study which showed an atrial flutter with atrial rate of 257 bpm, and 2:1/3:1 AV conduction. The flutter waves were negatives in leads II, III and a VF (type I atrial flutter). An endocardial mapping was obtained in order to localize the area of slow conduction. It was located in the isthmus of atrial tissue bounded by the inferior vena cava and the tricuspid valve annulus in the low posterior septal right atrium. In this area we applied radiofrequency energy in 10 occasions but the arrhythmia was not suppressed. With atrial pacing we achieve a concealed entrainment and then resumption of atrial flutter after cessation of pacing. After another 6 applications of radiofrequency in this same area in sinus rhythm, we paced the atrium without inducing any form of arrhythmia. He was asymptomatic 15 days later, but one month after the ablation, the flutter reappeared, we performed a second successful radiofrequency ablation. In this time he was asymptomatic.

[The DDD pacemaker implanted intravenously]. / El marcapaso DDD por vía transvenosa.

Retrospectively, we studied 66 consecutive patients in whom we implanted an intravenous DDD pacemaker. The indications were: AV block in 52 patients (79%), sick sinus syndrome in 5 patients (7.5%), both AV block and sick sinus syndrome in 4 patients (6%), and other causes in 5 (7.5%). The venous access route was by subclavian punction in 38 cases (57.5%) and by cephalic vein dissection in 28 (42.5%). With a mean follow-up of 16 months, there were complications in 11 patients (17%), in 9 of them, it was necessary a change in pacing mode different to DDD, and was possible to maintain a DDD pacing mode in 2 patients with a minimal reprogramming. The complications were: A) lost of sense and/or atrial capture in 10 patients (3 of them, had also loss of ventricular capture, one had pacemaker-mediated tachycardia, other had diaphragmatic stimulation and other had a severe infection of the pocket), B) atrial fibrillation appeared in another patient. At the implantation time there were significant differences between patients with and without complications on follow-up, the P wave amplitude was 1.86 +/- 0.75 mV in the first group vs. 3.06 +/- 1.52 mV in the latter group, p < 0.005, and the atrial pacing threshold was 1.10 +/- 1.17 microJ in the first group vs. 0.65 +/- 0.66 microJ in the latter group, p < 0.005. We consider that dual chamber stimulation is a well established form of therapy, although, it requires a more laborious implantation and specialized personal for its follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

[A new electrocardiographic algorithm for localizing accessory pathways using only the polarity of the QRS complex]. / Un nuevo algoritmo electrocardiográfico para la localización de las vías accesorias utilizando únicamente la polaridad del complejo QRS.

From 250 consecutive patients who underwent radiofrequency ablation of accessory pathways, we studied 102 patients with successful ablation of a single overt accessory pathway. All patients had manifested preexcitation on a baseline 12 lead electrocardiogram. None of this patients had additional congenital or acquired cardiac abnormalities which could have affected the QRS morphology. A new algorithm for localizing the AP site was developed, based only on the polarity of the QRS complexes in DIII, V1 and V2, without analysis of the delta wave. We could localize the accessory pathway in five sites with 88% of probability of success. This simplify the electrocardiographic analysis of Wolff Parkinson White and improvement the results of radiofrequency ablation.

[The response of ventricular tachycardia to adenosine administration]. / Respuesta de la taquicardia ventricular a la administración de adenosina.

Ten patients with ventricular tachycardia were studied. Two groups were formed. Group A included 5 patients with idiopathic ventricular tachycardia and group B included 5 patients with coronary heart disease. In all patients an electrophysiologic study was performed and monomorphic sustained ventricular tachycardia was induced through programmed stimulation. All patients received 12 mg of intravenous adenosine. The response was satisfactory in 3 of 5 patients in group A, with the presence of sinus rhythm. No response was seen in the other 2 patients. None of the patients in group B responded to the administration of intravenous adenosine. We concluded that adenosine may be useful in patients with cyclic AMP-mediated triggered activity ventricular tachycardia, in contrast to the coronary heart disease patients in which the mechanism is reentry. This interpretation is supported by results obtained in 15 experiments in canine heart.

[A retrospective study for the analysis of collateral effects of amiodarone]. / Estudio retrospectivo para el análisis de los efectos colaterales de la amiodarona.

UNLABELLED: We analyzed retrospectively 130 patients treated with amiodarone. They were seen at the Arrhythmias Clinic of this Institute from march 1981 until may 1988 with the purpose of evaluate the frequency of the side effects of the drug. The group of patients consisted of 67 men and 63 women, the mean age was 32 years and they were followed for about 32 months. The average dose of the drug was 1.069 gr per week. All of them had a physical and radiological examination, an ECG and laboratory tests. Besides, 86 patients went through an electrophysiological study at least once. One hundred and eighteen patients had periodical tests for thyroid function. All of the patients had a check up every 3 or 6 months. RESULTS: the response to the drug was good or even excellent in 83% of patients. They did not show electrocardiographic changes of statistic significance (duration of the PR, QRS or QT). The ophthalmologic examination showed corneal deposits in 48% of patients, but in no case there was indication to stop the treatment. Ten patients had a spontaneous regression of these deposits. Alterations of the thyroid function were seen in 33.8% of patients, 14 had hypothyroidism and seven hyperthyroidism, the others simple goitre. In four of these cases the drug was discontinued. Dermatologic lesions were seen in only 4% of patients. Despite the high frequency of side effects the need for stopping the treatment was low, with a high percentage of drug efficacy.