Electrophysiologically guided amiodarone therapy versus the implantable cardioverter-defibrillator for sustained ventricular tachyarrhythmias after myocardial infarction: results of long-term follow-up

OBJECTIVES

We sought to compare the long-term survival rates of patients with sustained ventricular tachyarrhythmia after myocardial infarction (MI) who were treated according to the results of electrophysiological (EP) study either with amiodarone or an implantable cardioverter-defibrillator (ICD).

BACKGROUND

Patients with sustained ventricular tachyarrhythmias after MI are at high risk of sudden cardiac death (SCD). However, data comparing the long-term survival rates of patients treated with amiodarone or ICD, according to the results of EP testing, are lacking.

METHODS

Patients underwent a first EP study at baseline and a second one after a loading dose of amiodarone of 14 +/- 2.9 g. According to the results of the second EP study, patients were classified either as responders or non-responders to amiodarone; non-responders were eventually treated with an ICD.

RESULTS

Eighty-four consecutive patients with MI (78 men; 21-77 years old; mean left ventricular (LV) ejection fraction 36 +/- 11%) were consecutively included. Forty-three patients (51%) were responders, and 41 patients (49%) were non-responders to amiodarone therapy. During a mean follow-up period of 63 +/- 30 months, SCD and total mortality rates were significantly higher in the amiodarone-treated patients (p = 0.03 and 0.02, respectively).

CONCLUSIONS

The long-term survival of patients with sustained ventricular tachyarrhythmias after MI, with depressed LV function, is significantly better with an ICD than with amiodarone therapy, even when stratified according to the results of the EP study. These patients should benefit from early ICD placement, and any previous amiodarone treatment seems to have no additional value.

[Open heart radio frequency left atrial compartmentation during mitral valve surgery: an alternative to the labyrinth procedure?]

The authors report their experience of radiofrequency left atrial compartimentation during open heart mitral valve surgery on 37 patients with a 42 +/- 12 months history of atrial fibrillation. The preoperative left ventricular ejection fraction was 62 +/- 8%; the left atrial diameter was 59 +/- 11 mm. The mean operative time was 245 +/- 60 minutes, which included 19 +/- 5 minutes for the ablation procedure. There were 2 early postoperative deaths and 2 deaths from non-cardiac causes at 3 and 6 months. The left ventricular ejection fraction and left atrial dimension were significantly decreased at the time of hospital discharge (54 +/- 12% and 51 +/- 7 mm respectively) (p < 0.01). After an average follow-up of 1 year, 81% of patients were free of atrial fibrillation: 6 patients had undergone DC cardioversion and 1 had a dual-chamber pacemaker. Patients in sinus rhythm after the ablation were associated with shorter periods of atrial fibrillation and smaller left atrial dimensions postoperatively than those who remained in fibrillation. The authors conclude that radiofrequency compartimentation of the left atrium associated with antiarrhythmic therapy can interrupt atrial fibrillation in 81% of patients at 1 year: the ablation procedure takes only 8% of the operation time. Predictive factors of success of ablation should be defined to determine which patients benefit most from this technique.

[Implantable defibrillator. Update]

The implantable cardioverter-defibrillator is a device able to detect and efficiently treat life-threatening ventricular arrhythmias. Its decisive accomplishment in reducing sudden cardiac death and total cardiac mortality, opposed to the insufficient reliability of the traditional therapies explains its present ascendancy. In this review, the working principles and the implant techniques are developed, as well as the complications and the usual problems which could be encountered in implanted patients. Finally, the current indications are discussed in the light of recent clinical trials.

Late clinical outcome after successful radiofrequency catheter ablation of accessory pathways

AIMS

To evaluate the long-term clinical results of patients who underwent successful radiofrequency catheter ablation of a symptomatic drug-resistant accessory-pathway-mediated tachycardia.

METHODS AND RESULTS

Clinical follow-up was done by direct contact with the patients and their physicians. One hundred and eighty consecutive patients (113 males, 67 females) were followed during a median period of 48.1 months. There were seven procedure related complications (4%). During the follow-up period, 79% of the patients remained asymptomatic; 14% complained of short bouts of palpitations due to isolated or short runs of atrial or ventricular premature beats; 7% had sustained palpitations due either to accessory pathway recurrence (4%) or supraventricular tachyarrhythmias not associated with an accessory pathway (3%). Symptoms due to accessory pathway recurrence appeared either in the first month following the ablation or at least later than 3 months when sustained supraventricular arrhythmias occurred related to another cause.

CONCLUSIONS

Initially successful radiofrequency catheter ablation has a low, long-term recurrence rate (4%). Recurrence of accessory-pathway-mediated tachycardia is observed during the first month while later symptoms suggest supraventricular arrhythmias from another cause.

Cytogenetic alignment of the bovine chromosome 13 genome map by fluorescence in-situ hybridization of human chromosome 10 and 20 comparative markers

A bovine bacterial artificial chromosome (BAC) library was screened for the presence of six genes (IL2RA, VIM, THBD, PLC-II, CSNK2A1 and TOP1) previously assigned to human chromosomes 10 or 20 (HSA10 or HSA20). Four of the genes were found represented in the bovine BAC library by at least one clone. The identified BAC clones were used as probes in single-color fluorescence in-situ hybridization (FISH) to determine the chromosomal band location of each gene. As predicted by the human/bovine comparative map and comparative chromosome painting analysis, the four genes mapped to bovine chromosome 13 (BTA13). Dual-color FISH was then used to integrate these four type I markers into the existing BTA13 genome map. These FISH results anchor the BTA13 genome map from bands 14-23, and confirm the presence of a conserved HSA10 homologous synteny group on BTA13 centromeric to a HSA20 homologous segment.

Chromosome identification and assignment of DNA clones in the dog using a red fox and dog comparative map

We have developed a novel method for identifying dog chromosomes and unambiguously mapping specific clones onto canine chromosomes. This method uses a previously established red fox/dog comparative chromosome map to guide the FISH mapping of cloned canine DNA. Mixing metaphase preparations of the red fox and dog enabled a single hybridization to be performed on both species. We used this approach to map the chromosomal locations of twenty-six canine cosmids. Each cosmid contains highly polymorphic microsatellite markers currently used by the DogMap project to compile the canine linkage map. All but two cosmids were successfully assigned to subchromosomal regions on red fox and dog chromosomes. For eight cosmids previously mapped on dog chromosomes, we confirmed and refined the canine chromosomal assignments of seven cosmids and corrected an erroneous assignment regarding cosmid CanBern1. These results demonstrate that the red fox and dog comparative chromosome map can greatly improve the accuracy and efficiency of chromosomal assignments of canine genetic markers by FISH.

[Cardiac pacing. Percutaneous extraction of infected pacing catheter]

Infection of a cardiac pacemaker is a rare but serious complication. Percutaneous ablation of the pacemaker and pacing catheter is the only effective treatment. Techniques of extraction of pacing systems have been evaluated but the long term results require analysis. Eighteen patients with infection of cardiac pacemakers underwent extraction of one or more pacing catheters (14 atrial and 20 ventricular) in one same centre. The indication was infection of the pacemaker unit (12 cases) or septicaemia (6 cases) The causal organism was a staphylococcus (aureus: 7 cases, epidermidis: 10 cases, capitis: 1 case). Three techniques were used: 1) direct external manual traction, 2) internal traction with several devices, 3) endovascular counter-traction (Byrd-Cook system). The time from primary implantation of the pacing catheter to its extraction was 42 months and from last pacemaker manipulation to infection, 23 months. The average duration of the extraction procedure was 120 +/- 45 minutes; that of fluoroscopy was 10 +/- 6 minutes. The first technique was used 12 times, the second 8 times and the third 14 times, with complete extraction of the catheter in 88.2% of cases. The metallic tip of the distal electrode embolised in 2 cases and remained stuck in the right ventricle in 1 case. Only one pacing catheter was abandoned. After an average follow-up of 45 months, none of the patients had recurrent infection or any other complication. The authors conclude that extraction of infected pacing catheters is safe and effective. It is the treatment of choice of this complication.

Five new linkage groups in the canine linkage map

Nineteen further polymorphic loci were typed on the DogMap reference panel. Five new linkage groups were identified. Additionally, five markers were added to earlier defined linkage groups. Three of the new linkage groups contain markers mapped earlier to specific dog chromosomes by physical mapping. These results make a further contribution to the canine genome map and provides more linkage groups physically assigned to known chromosomes.

Recurrent cardioembolic stroke related to late dislodgement of a right atrial pacing lead into the left atrium

A 76-year-old woman had a permanent transvenous DDDR pacemaker implanted for complete atrioventricular block. She was hospitalized 4 years later for recurrent transient ischaemic attacks related to dislodgment of the atrial lead into the left atrium through a patent foramen ovale. The patient was successfuly treated by transvenous extraction of the atrial lead. The follow-up has been uneventful 12 months after the procedure. Left atrially dislodged pacemaker leads have to be retracted under full anticoagulation.

What risk should justify implantable cardioverter defibrillator therapy?

Implantable cardioverter defibrillators (ICDs) were developed to prevent sudden cardiac death in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Their safety and efficacy have been proved in multiple retrospective and prospective studies. Many of the published trials were directed at secondary prevention for patients who had already had a sudden cardiac death or a sustained VT. For primary prevention, the information available is limited, as only 2 trials have yet been published. Ongoing trials will probably allow us to broaden the indications for prophylactic ICD implantation. Justification of the risk will have to be evaluated against complexity of the implant, the latter including not only cost but quality of life and morbidity associated with an ICD. However, our efforts still have to be directed to improve risk stratification and to decrease the complexity of the procedure.

Ventricular arrhythmia and torsade de pointe: dose limiting toxicities of the MDR-modulator S9788 in a phase I trial

BACKGROUND

S9788 is a triazineaminopiperidine derivative capable of reversing multidrug resistance (MDR) in vitro. In preclinical models S9788 was several fold more potent MDR inhibitor than verapamil or cyclosporine. At P-glycoprotein (Pgp) blocking concentrations, S9788 appeared to have only very little toxicity.

PATIENTS AND METHODS

In a two step phase I trial we treated 39 patients with refractory cancer with S9788 and bolus doxorubicin. The steps differed mainly in the S9788 infusion duration; in the first part 23 patients received the MDR-reversing drug S9788 over 30 minutes, in the second step of the study 16 patients were administered S9788 over 150 minutes. The doses of S9788 were escalated in cohorts of three patients up to a dose level (DL) of 96 mg/m2 on the 30 minutes infusion, and to 144 mg/m2 on the 150 minutes infusion. The pharmacokinetics of S9788 were determined.

RESULTS

With the 30-minute infusion schedule symptomatic cardiac arrhythmia were found to be dose limiting. In all patients at the highest DL transient cardiac repolarization prolongation with a long QT-interval on ECG was demonstrated. With the 150-minute administration schedule, S9788 could be escalated up to 144 mg/m2 without subjective toxicity. However, transient QT prolongation was present in all patients. A third degree AV-block and a QT increase of about 40% occurred at the highest DL. Asymptomatic torsade de pointe (DL 96 mg/m2) was demonstrated on Holter recording in one patient. Theses repolarization disturbances with QT increase were considered dose limiting toxicity and the trial was closed. No arrhythmia related death was noted. Pharmacokinetics were similar with both infusion schedules with a mean alpha half life of 11.3 and 13.2 minutes, for the 30-minute and 150-minute infusion, and a terminal half life of 13.5 and 15 hours, respectively. QTc prolongation duration appeared to be dose-dependent.

CONCLUSIONS

With the tested infusion schedules, cardiac toxicity, in particular AV-blocks and QT prolongation, leading to ventricular arrhythmia and torsade de pointe, are the dose limiting toxicities of S9788. Our experience together with the observation of asymptomatic torsade de pointe in two other phase 1 trials of S9788 infused over six hours precluded the further clinical development of S9788.