Implantable cardioverter-defibrillator: beyond efficacy.

OBJECTIVES: The introduction of the implantable cardioverter-defibrillator was a very important advance in the treatment of malignant ventricular arrhythmias. However, its use is associated with some possible adverse events, which should be taken into consideration when a patient is proposed for implantation. These complications may occur early after implantation and be associated with the procedure itself, or they may be late complications, usually associated with the device or the arrhythmia. It was our objective to assess the incidence of these complications in our population of patients. POPULATION AND METHODS: We describe the complications found in 98 patients (55.9 +/- 13.9 years, 89% male) with an implantable cardioverter-defibrillator and compare our results with the incidence of complications described by other authors. RESULTS: We found complications associated with the presence of the implantable cardioverter-defibrillator in 32% of patients. The most frequent complication was inappropriate shocks in 13%. The presence of infection was detected in 4%, lead insulation faults in 5%, need for lead extraction in 2%, repositioning in 1% and re-establishment of the connection with the generator in 2%. In 5% of patients, there was inefficacy of the device, 3% due to non-detected ventricular tachycardias (slow tachycardias) and 2% due to electrical storms. There was syncope in 2% of patients. The total mortality in a 2.9 +/- 1.9 year follow-up was 13% (sudden death in 3%). CONCLUSIONS: Major complications associated with implantable cardioverter-defibrillators were in our experience relatively rare, our results agreeing with those of other centers.

[Atrial fibrillation: current trends]. / Fibrilhação auricular--tendências actuais.

The author analyses the current relevance of atrial fibrillation (AF), an arrhythmia no longer viewed as a benign situation, being the first arrhythmic cause of hospitalisation. New data related to the conversion of this arrhythmia to sinus rhythm is reviewed, namely internal atrial defibrillation with low energy shocks and the efficacy of new drugs such as ibutilide. The current role of transesophageal echocardiography in permitting a shorter scheme of anticoagulation before the DC shock is also reviewed. About the importance of maintaining sinus rhythm, the author mentions new data from the Framingham Study showing that AF is an independent predictor of mortality. Attention is drawn to the important role of AF duration before cardioversion, since an "electrical remodeling" does occur, quickly reducing the probability of maintaining sinus rhythm. Concerning the limitations of pharmacological therapy, the author mentions the AFFIRM study that, in a few years, will hopefully solve the controversy concerning the best strategy--maintenance of sinus rhythm versus rate control. Also concerning pharmacological therapy, the author mentions two trials suggestive of the efficacy of amiodarone and dofetilide in AF patients with congestive heart failure. Regarding non-pharmacological options, reference is made to recent advances in surgery of AF and to the search for more simplified operative procedures to reduce intervention risks and duration. To overcome the difficulties in reproducing the maze operation with catheter ablation, new alternatives have appeared, such as energy application inside the pulmonary veins, known as the source of most ectopic atrial beats that trigger AF episodes. The author concludes that since AF is a heterogeneous entity, different therapies must exist, but the pharmacological approach will maintain a central role and non pharmacological therapies should be used as an alternative in refractory cases.

[The patient at risk of sudden death:value of drug therapy]. / O doente em risco de morte súbita: valor da terapêutica farmacológica.

The evaluation of antiarrhythmic therapy should be based on its effects on total mortality assessed by controlled trials. The author reviews the large trials on antiarrhythmic drugs, during the past ten years, and concludes with the current importance of such therapy. Trials have been conducted in three kinds of high-risk populations: patients with malignant ventricular arrhythmias, survivors of myocardial infarction and patients with congestive heart failure. The results have been disappointing, showing either an increase in mortality with antiarrhythmic drugs (class I, d-sotalol) or a neutral effect (amiodarone). Trials conducted in patients with malignant arrhythmias have shown that the implantable cardioverter-defibrillator was superior to the best available antiarrhythmic therapy. In other high-risk populations, the only drugs that consistently reduced mortality were betablockers, which might have other mechanisms of action besides the antiarrhythmic effect. Amiodarone, the most potent suppressor of ventricular arrhythmias, is indicated in highly symptomatic patients; dl-sotalol is a good alternative to amiodarone. We may conclude from these large trials that study endpoints must be correctly chosen in order to assess the real value of an antiarrhythmic drug. The study population must have a high risk of sudden death and be within an appropriate time window of maximal risk. Antiarrhythmic trials must proceed, learning the lessons from the old studies, trying to test new drugs or new therapeutic strategies, better selecting study populations and new risk markers superior to those currently available.

Microwave ablation of atrial flutter.

Radiofrequency (RF) ablation of the isthmus between the inferior vena cava and the tricuspid ring has proven to be a safe and successful method of treating atrial flutter (AF). However, RF ablation lesions are small in size requiring a considerable number of energy applications to ablate the AF circuit. The aim of this study was to evaluate the feasibility and efficacy of microwave energy for AF ablation. We report a case of sustained typical AF treated successfully and safely by 1 pulse of microwave (MW) energy. This showed it is possible to treat AF with a small number of pulse applications.

[Catheter ablation with radiofrequency energy in 100 patients with Wolff-Parkinson-White syndrome]. / Ablação por cateter com energia de radiofrequência de 100 doentes com síndrome de Wolff-Parkinson-White.

OBJECTIVE: The aim of this paper was to evaluate our results of radiofrequency catheter ablation (RFCA) of accessory pathways in patients with WPW syndrome. STUDY PATIENTS: We studied 100 consecutive patients with WPW syndrome, 52 men and 48 women, mean age 37 +/- 15 years who underwent RFCA. All patients were symptomatic, with documented episodes of supraventricular tachycardia and 9% of patients had underlying cardiac disease. METHODS: The RFCA was performed without antiarrhythmic drugs in the same session of the electrophysiologic diagnosis. The location of the accessory pathway site was obtained by catheter mapping, based on the premature and/or the presence of Kent potentials. According to the location of the accessory pathway, the ablation catheter was introduced either by the femoral vein or artery with mapping of the tricuspid or mitral ring. In the first cases performed energy application was manually controlled and thereafter was temperature guided with an upper temperature limit of 70 degrees C. We considered primary success criteria the disappearance of the delta wave in the surface ECG and the absence of ventricular preexcitation under atrial pacing and after adenosine injection. Clinical success was defined as the absence of clinical recurrence of tachycardia during the follow-up period. RESULTS: The primary success rate achieved was 88%; 91% in the left free wall pathways, 100% in the right free wall and 85% in the septal pathways (antero-septal-83%; right postero-septal-76.5%; left postero-septal-92%). A second ablation procedure was performed in seven of the twelve patients with primary unsuccess obtaining a final success rate of 93% (left free wall-94.5%; septal pathways-91.6%). After a mean follow-up period of 8 +/- 7 months clinical recurrence occurred in 9% (eight patients), five of which are under anti-arrhythmic therapy (62.5%). Clinical success rate at the end of the follow-up period was 88%. CONCLUSIONS: In our experience RFCA has shown to be safe and with a high success rate in patients with symptomatic pre-excitation. In this group of patients it was an effective therapy.

[Acute myocardial infarct in a young cocaine user]. / Enfarte agudo do miocárdio num jovem consumidor de cocaína.

In patients less than 40 years of age, acute myocardial infarction (AMI) has special clinical and pathophysiologic characteristics. Its prevalence varies between 5 and 10%. In such patients, AMI associated with chronic cocaine abuse has a non-negligible prevalence of 6%. The purpose of this report is to describe the case of a 24-year old male patient with smoking habits and chronic abuse of cocaine and hallucinogenic drugs. This patient developed clinical, enzymatic and electrocardiographic criteria of anterior AMI, two hours after the ingestion of an LSD-like hallucinogenic drug. The coronary angiography revealed a critical stenosis of the medium segment of the left anterior descendent artery, and a pre-stenotic aneurysmatic dilatation. In order to determine the etiology of the aneurysm, various laboratory and histologic tests were performed. The results of these were normal. We review the pathophysiology, clinical manifestations and prognosis of cocaine-associated AMI.

[The radiofrequency catheter ablation of ventricular tachycardia]. / Ablação por cateter de taquicardia ventricular com energia de radiofrequência.

OBJECTIVE: The aim of this study was to evaluate our results of radiofrequency catheter ablation (RFCA) of ventricular tachycardia. PATIENT SELECTION: We treated with RFCA nine patients, six male and three female, mean age 36 +/- 12 years with ventricular tachycardia (VT), who fulfilled the following criteria; 1) recurrent VT; 2) resistant fo medical therapy despite the use of more than one antiarrhythmic drug; 3) inducible by programmed ventricular stimulation; 4) hemodynamically well tolerated. The VT etiology was coronary artery disease (CAD) in three patients, dilated cardiomyopathy in one, right ventricular dysplasia in one and it was idiopathic in four (being fascicular in three and catecholaminergic right ventricular outflow tract VT in one). METHODS: The RFCA was performed under antiarrhythmic medication. The adequate ablation site was obtained by mapping of the VT, looking for the earliest ventricular activation, identification of isolated mid-diastolic potentials during sinus rhythm or presystolic during VT, good pace mapping (at least 10 of the 12 standard ECG leads), and high frequency short duration spikes, the so called P potentials in fascicular VT. Primary success achieved when occurred termination of VT during application of RF energy and/or VT was no longer inducible by programmed stimulation with the same stimulation protocol. RESULTS: Global primary success rate was 89%, being 100% in idiopathic VT, and 80% in VT associated with structural heart disease. In a follow-up period of 12 +/- 14 months all patients were alive, 75% free of VT in the idiopathic VT group; and 50% in patients with structural heart disease. One of these patients underwent cardioverter defibrillator implantation to treat a fast VT with a new morphology not treated by ablation, and the other two had VT modification with a significant reduction in the number of episodes. CONCLUSIONS: Radiofrequency catheter ablation of VT has shown a good success rate, and it is a valuable alternative in patients with hemodynamically tolerable VT, refractory to drug treatment, highly symptomatic and without surgical indication. In cases of idiopathic VT we had a high rate success and we think that RFCA will probably become the primary indication in symptomatic patients.

[Holter electrocardiography en pediatric cardiology: preliminary experience]. / Electrocardiografia de Holter em cardiologia pediátrica: experiência inicial.

PURPOSE: Evaluation of the diagnostic value of continuous electrocardiographic recording (Holter monitoring) in Paediatric Cardiology. STUDY DESIGN: Retrospective study based on the data records of the Arrhythmia Department regarding patients with less than 20 years of age with Holter monitoring performed between January 1983 and February 1995 (374 recordings). PATIENTS: 277 patients were studied, 163 were male and 114 female with a mean age of 12 +/- 5 years. Heart organic anomalies were present in 155 patients and 92 patients had previous cardiac surgery with cardiopulmonary bypass. Clinical indications for Holter recording were the evaluation of symptoms related to arrhythmias (38%), documented dysrhythmia (23%), arrhythmia detected on physical examination (18%) and evaluation of risk in patients without symptoms of arrhythmia (17%). METHODS: Holter recordings were performed during 24 hours with two channels (modified V1 and V5). RESULTS: Significant rhythm and conduction disturbances were found in 122 patients. These were ventricular premature complexes > or = 10/hour (27 patients), AV block (25 patients) and supraventricular premature complexes > or = 10/hour (22 patients). Holter recording revealed significant dysrhythmias in 52% of patients with previously documented dysrhythmia, in 43% of patients referred for assessment of risk without symptoms of arrhythmia, provided insight in 48% of requests due to arrhythmia detected on physical examination and 24% of requests for symptoms related to arrhythmias. In 13 patients the results of Holter recording led to therapeutic or diagnostic measures. CONCLUSIONS: Holter recording showed an overall sensitivity of 44% in the detection of significant arrhythmias and led to therapeutic and additional diagnostic measures in 11% of these patients. Holter recording seems to provide important information in the evaluation of arrhythmias in the paediatric age group.

[Antiarrhythmic agents: current situation]. / Fármacos antiarrítmicos: ponto da situação.

Cardiac Arrhythmia Suppression Trial (CAST) had a profound impact on the practice of cardiology. This trial showed the importance of placebo controls in judging the effects of therapy and the pitfalls of using surrogate end points for mortality in clinical disorders. The number of new prescriptions of class I drugs fell progressively after CAST; there was a change in antiarrhythmic drug labelling as well as on research and the "suppression hypothesis" was no more valuable as a theoretical support to the antiarrhythmic treatment of prognostical significant ventricular arrhythmias. Several arguments favour generalization of CAST results to the whole class I drugs. So, all those drugs depress cardiac conductivity, which is potentially arrhythmogenic, and the results of several trials and overviews are in consonance with CAST ones. Beta-blockers are the sole drugs that consistently decreased cardiac sudden death after myocardial infarction. An ancillary study from CAST trial suggests that those drugs can have also an anti-proarrhythmic effect, which needs further confirmation. Beta-blockers can join an important place in malignant ventricular arrhythmias therapy, used lonely or specially in association with drugs from other classes. CAST conclusions are probably not applicable to class III drugs, as they do not depress conductivity, acting mainly by prolonging repolarization. So, they are the most promising drugs in post CAST era: some trials seem to confirm the advantages of amiodarone and DL-sotalol in clinical use, and there are several other new class III drugs in development. A few little and medium dimension amiodarone trials showed a decrease in mortality in myocardial infarction survivors and in patients with cardiac insufficiency. We are waiting the results of some large trials to get more definitive conclusions. In malignant ventricular arrhythmias, empiric amiodarone have been superior to electrophysiological guided therapy. Also in malignant ventricular arrhythmias, DL-sotalol was significantly best than six class I drugs in the prevention of new arrhythmias, the therapy being guided by Holter monitoring or electrophysiological studies. We conclude that in the present state of our knowledge, the greatest promise might hold in the area of complex molecules with a diversity of electrophysiological actions, seeming critical the existence of a sympathicolitic effect for an effective protection against sudden death.

[Effects of coronary surgery on silent ischemia]. / Influência da cirurgia coronária na isquémia silenciosa.

In order to assess the effects of coronary artery bypass surgery on silent myocardial ischemia, we studied a group of 39 consecutive patients, 38 male and 1 female with a mean age of 56 + 7 years, with stable chronic angina pectoris, by 48 hours-Holter monitoring and maximal treadmill exercise test before and after operation. The reduction of angina was 92% (p less than 0.0001) and of ischemia 57% (p less than 0.0001) after operation. Silent myocardial ischemia was detected in 21 patients (54%) before operation, 13 by Holter, 4 by exercise test and 4 by the two methods. After operation 13 patients (36%) continue to have silent ischemia depicted in 7 by Holter and in 7 by exercise test. No new patient developed silent ischemia after operation. The group of patients with silent ischemia preoperatively was not significantly different from the group without silent ischemia based on clinical and angiographic characteristics, results of surgery and exercise test parameters with exception of ST segment depression. In conclusion, silent myocardial ischemia may persist after successful coronary artery bypass surgery for the relief of angina pectoris, and should be monitored by serial Holter recordings and treated medically, if its prognosis and consequences proved to be similar to manifest symptomatic ischemia.