Acute success and short-term follow-up of catheter ablation of isthmus-dependent atrial flutter; a comparison of 8 mm tip radiofrequency and cryothermy catheters

Objectives

To compare the acute success and short-term follow-up of ablation of atrial flutter using 8 mm tip radiofrequency (RF) and cryocatheters.

Methods

Sixty-two patients with atrial flutter were randomized to RF or cryocatheter (cryo) ablation. Right atrial angiography was performed to assess the isthmus. End point was bidirectional isthmus block on multiple criteria. A pain score was used and the analgesics were recorded. Patients were followed for at least 3 months.

Results

The acute success rate for RF was 83% vs 69% for cryo (NS). Procedure times were similar (mean 144 ± 48 min for RF, vs 158 ± 49 min for cryo). More applications were given with RF than with cryo (26 ± 17 vs. 18 ± 10, p < 0.05). Fluoroscopy time was longer with RF (29 ± 15 vs. 19 ± 12 min, p < 0.02). Peak CK, CK-MB and CK-MB mass were higher, also after 24 h in the cryo group. Troponin T did not differ. Repeated transient block during application (usually with cryoablation) seemed to predict failure. Cryothermy required significantly less analgesia (p < 0.01), and no use of long sheaths (p < 0.005).

The isthmus tended to be longer in the failed procedures (p = 0.117). This was similar for both groups, as was the distribution of anatomic variations. Recurrences and complaints in the successful patients were similar for both groups, with a very low recurrence of atrial flutter after initial success.

Conclusions

In this randomized study there was no statistical difference but a trend to less favorable outcome with 8 mm tip cryocatheters compared to RF catheters for atrial flutter ablation. Cryoablation was associated with less discomfort, fewer applications, shorter fluoroscopy times and similar procedure times. The recurrence rate was very low. Cryotherapy can be considered for atrial flutter ablation under certain circumstances especially when it has been used previously in the same patient, such as in an AF ablation.

Coronary risk factors and inflammation in patients with coronary artery disease and internal cardioverter defibrillator implants

BACKGROUND

The internal cardioverter defibrillator (ICD) is increasingly used to treat ventricular tachyarrhythmias in patients with coronary artery disease (CAD). The burden of coronary risk factors and inflammation is however not well studied in these high risk patients.

STUDY AIMS

The aim of the present study was to describe the prevalence of coronary risk factors (including lipid values) and inflammation (including high sensitive-C-reactive protein, hs-CRP) in patients with CAD and ICD implants.

METHODS

Baseline clinical characteristics and laboratory results of all eligible patients for the Cholesterol Lowering and Arrhythmias Recurrences after Internal Defibrillator Implantation trial (CLARIDI trial) were used. All patients had documented CAD, an ICD implant and were not yet treated with statins. Coronary risk factors, lipid values, glycated haemoglobin (HbA(1c)) and hs-CRP levels were determined.

RESULTS

In the 110 included patients (mean age 68+/-9 years, LVEF 40+/-17%, NYHA class II-III in 47%), a high prevalence of coronary risk factors was documented: current smoking in 18%, body mass index > or =30 kg/m(2) in 16%, blood pressure > or =140/90 mm Hg in 40%, history of diabetes in 12%, and HbA(1c) > or =6% in 16% of patients not known with diabetes. A total cholesterol >175 mg/dl was found in 76% of patients and an LDL cholesterol >100 mg/dl in 83%. Finally, median hs-CRP was 4.8 mg/l (interquartile range 2.5-13.9 mg/l). Hs-CRP values > or =2 mg/l were noted in 83% of all patients and in 68% of patients who had an ICD implant more than 6 months before inclusion.

CONCLUSION

In CAD patients with ICD implants, the burden of coronary risk factors is high, often unrecognized and/or under-treated. Persistent inflammation is found in the majority of these patients.

Tachycardiomyopathy with familial predisposition masquerading as peripartum cardiomyopathy

A 28-year-old pregnant lady presented with cardiomyopathy and atrial tachycardia. The patient had severe heart failure and syncope. Her past medical history was uneventful. Her mother, however, had received an implantable cardioverter defibrillator (ICD) after an out-of-hospital cardiac arrest due to idiopathic ventricular fibrillation. The patient was scheduled for programmed stimulation, during which a monomorphic ventricular tachycardia was induced. An ICD was then implanted. Following radiofrequency ablation of the atrial tachycardia, left ventricular function recovered completely. Given the family history, a genetic predisposition to both arrhythmias and tachycardiomyopathy needs to be considered.

The role of remote monitoring in the reduction of inappropriate implantable cardioverter defibrillator therapies

Implantable cardioverter defibrillators (ICDs) with the integrated Home Monitoring feature use dedicated mobile phone and internet links to provide the physicians and technicians in the ICD clinic with the essential device- and arrhythmia-related data stored in the ICD diagnostic memory. Various counters, graphs and intracardiac electrograms are automatically transmitted via Home Monitoring each day to allow prompt, remote presentation of arrhythmias or detection of technical problems. One of the most inconvenient side-effects of the ICD therapy is inappropriate intervention of the device. Home Monitoring data can help the physician to identify and subsequently reduce the incidence of inappropriate ICD therapy.

Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation

OBJECTIVE

To compare the efficacy of cardioversion in patients with atrial fibrillation between monophasic damped sine waveform and rectilinear biphasic waveform shocks at a high initial energy level and with a conventional paddle position.

DESIGN

Prospective randomised study.

PATIENTS AND SETTING

227 patients admitted for cardioversion of atrial fibrillation to a tertiary referral centre.

RESULTS

70% of 109 patients treated with an initial 200 J monophasic shock were cardioverted to sinus rhythm, compared with 80% of 118 patients treated with an initial 120 J biphasic shock (NS). After the second shock (360 J monophasic or 200 J biphasic), 90% of the patients were in sinus rhythm in both groups. The mean cumulative energy used for successful cardioversion was 306 J for monophasic shocks and 159 J for biphasic shocks (p < 0.001).

CONCLUSIONS

A protocol using monophasic waveform shocks in a 200-360 J sequence has the same efficacy (90%) as a protocol using rectilinear biphasic waveform shocks in a 120-200 J sequence. This equal efficacy is achieved with a significantly lower mean delivered energy level using the rectilinear biphasic shock waveform. The potential advantage of lower energy delivery for cardioversion of atrial fibrillation needs further study.

An equine model of chronic atrial fibrillation: methodology

We describe the development and the different features of an experimental model of chronic atrial fibrillation (AF) in equines. In four healthy ponies a dual-chamber pacemaker, with an adapted pacemaker program, was implanted transvenously in the standing animal. This adapted pacemaker induced episodes of AF by delivering a 2s burst of electrical stimuli (42 Hz) as soon as sinus rhythm was detected. Simultaneous with a surface electrocardiogram, the intra-atrial electrogram could be recorded to determine the atrial electrogram morphology. Programmed electrical stimulation (PES) was used to determine the atrial effective refractory period (AERP) and the rate adaptation of the AERP, the sinus node recovery time (SNRT) and the corrected SNRT, AF vulnerability, AF cycle length and AF duration. This experimental AF model can be used to study the pathophysiology of chronic AF in equines.

Hybrid pharmacological and ablative therapy for the management of symptomatic atrial fibrillation

BACKGROUND

Hybrid therapy for atrial fibrillation class 1C and class III antiarrhythmic drugs (AAD) can convert atrial fibrillation (AF) into an isthmus-dependent atrial flutter (AFL) in more than 10% of patients. Hybrid pharmacological and ablative therapy offers a safe and effective approach to achieving and maintaining sinus rhythm. We evaluated the efficacy of this hybrid approach in the management of paroxysmal or persistent AF.

METHODS

Eighteen patients with symptomatic AF treated with AAD and typical anticlockwise/clockwise AFL underwent radiofrequency (RF) ablation of AFL with an anatomical approach.

RESULTS

RF ablation was successful in all patients. All but one patient continued with AAD. Four patients (22%) had recurrences of AFL. Two of them also had a recurrence of AF. Another three patients had recurrences of AF only, and finally, one patient developed an atrial tachycardia more than one year after the procedure. In conclusion, 11 patients (61%) did not experience recurrences of AF/AFL after tricuspid valve annulus (TV)-inferior caval vein (IVC) isthmus ablation with continuing antiarrhythmic drugs.

CONCLUSION

Hybrid pharmacological and ablative therapy is a safe and effective treatment for the management of patients with symptomatic AF.

Effects of intravenous dofetilide on induction of atrioventricular re-entrant tachycardia

OBJECTIVE

To assess the efficacy and safety of intravenous dofetilide in preventing induction of atrioventricular re-entrant tachycardia.

DESIGN

A multicentre, open, dose ranging trial. Fifty one patients with electrically inducible atrioventricular re-entrant tachycardia were allocated to one of five doses of dofetilide (1.5, 3, 6, 9, and 15 microgram/kg), two thirds of the dofetilide dose being given over a 15 minute loading period and the remainder over a 45 minute maintenance period.

MAIN OUTCOME MEASURE

Responders were defined as patients in whom dofetilide prevented reinduction of atrioventricular re-entrant tachycardia at the end of the infusion.

RESULTS

Intravenous dofetilide had no effect on tachycardia inducibility at the two lower doses (1.5 and 3 microgram/kg) but prevented the reinduction of tachycardia at the three higher doses (6, 9, and 15 microgram/kg) at a rate of 36% (11/31). There was a clear relation between plasma dofetilide concentrations and efficacy (p = 0.009). In non-responders, dofetilide increased the cycle length of induced atrioventricular re-entrant tachycardia. Dofetilide increased the atrial and ventricular effective refractory periods, as well as the antegrade and retrograde effective refractory period of the accessory pathway. Treatment related side effects were reported in four patients, one with a new sustained incessant supraventricular tachycardia.

CONCLUSIONS

Dofetilide shows promise as an agent for the prevention of atrioventricular re-entrant tachycardia in patients without structural heart disease.

Dual-chamber pacemaker implantation via the cephalic vein in healthy equids

The purpose of the present study was to develop a feasible and safe technique for dual-chamber pacemaker implantation in healthy horses. Implantation was performed in a standing, tranquilized horse and in ponies. Atrial and ventricular leads were transvenously inserted through the cephalic vein, and a subcutaneous pacemaker pocket was created between the lateral pectoral groove and the manubrium sterni in 6 equids. Positioning of each lead was guided by echocardiography and by measuring the electrical characteristics of the lead. The implantation procedure lasted about 4 hours in each animal and was well tolerated. In all animals, dual-chamber pacemaker function was obtained, and these results remained good throughout the follow-up period. At the time of implantation, atrial and ventricular sensing were between 2.1 and 7.2 mV and 7.8 and 16.8 mV, respectively, and atrial and ventricular pacing thresholds at 0.5 millisecond varied from 0.5 to 0.7 V and from 0.3 to 1.0 V, respectively. Six months after the implantation, sensing values varied from 2 to 10 mV for the atrial lead and from 2 to 16 mV for the ventricular lead, while pacing thresholds at 0.5 millisecond varied from less than 0.5 to 2.5 V for the right atrium and from less than 0.5 to 5.0 V for the right ventricle. Atrial lead dislodgment occurred in 2 animals, requiring insertion of a new lead. Ventricular lead dislodgment was not observed.

Initial clinical experience with a new arrhythmia detection algorithm in dual chamber implantable cardioverter defibrillators

AIM

Inappropriate therapy, due to poor discrimination of supraventricular tachycardia (SVT) from ventricular tachycardia (VT) remains a major problem in patients with an implantable cardioverter defibrillator (ICD). Theoretically, the addition of atrial sensing in discrimination algorithms should improve this differentiation. The aim of the study is to evaluate the performance of a new tachycardia discrimination algorithm, SMART Detection.

METHODS AND RESULTS

Twenty-six patients received a non-thoracotomy ICD system (Phylax AV, Biotronik, Germany). All documented spontaneous arrhythmia episodes were analyzed. During a mean follow-up of 8 months, a total number of 139 events with stored electrograms were recorded in 12 patients. The final diagnosis was ventricular fibrillation (VF) or polymorphic VT (n=20), monomorphic VT (n=69), SVT (n=26), other ventricular arrhythmia (n=3) and T wave oversensing (n=21). In 6 episodes a dual tachycardia was present. Considering SVT episodes, inappropriate therapy occurred in 2 cases of atrial flutter due to stable ventricular rate (<30 ms), 1 case of atrial tachycardia and 2 cases of sinus tachycardia due to a sudden onset (> 10%).

CONCLUSION

With the SMART Detection algorithm, discrimination of VT from SVT achieved a sensitivity of 100%, with an accuracy of 95.6% for all ventricular arrhythmias. In the case of SVT, the algorithm appropriately detected and inhibited therapy in 88% of atrial fibrillation.

Determinants of sudden death after discharge from hospital for myocardial infarction in the thrombolytic era

AIMS

The purpose of this study was to assess risk factors for sudden death after discharge from hospital for myocardial infarction in an era in which 50% of patients receive thrombolytic drugs.

METHODS AND RESULTS

We prospectively studied 708 consecutive survivors of myocardial infarction admitted to hospitals, which had registered their clinical, functional, and electrical parameters. A total of 83 patients died in the first 2 years (12%) after discharge. Sudden death was only observed in 12 patients. In multivariate analysis only NYHA class >I, and a filtered QRS duration > or =110 ms were important predictive variables for sudden death. A pre-defined high-risk group of 25 patients had no sudden death. When the strongest predictive variables in univariate analysis were combined to increase the positive predictive value for sudden death, we only achieved a maximal value of 27%.

CONCLUSIONS

In an unselected infarction population, the risk for sudden death is low in the first 2 years. Therefore, prediction and prophylactic intervention, such as defibrillator therapy become difficult. The event is related to cardiac dysfunction on admission, and with abnormalities in the filtered electrocardiogram.

Long term results of cardioverter-defibrillator implantation in patients with right ventricular dysplasia and malignant ventricular tachyarrhythmias

OBJECTIVE

To study the outcome of patients with arrhythmogenic right ventricular dysplasia treated with an implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias complicated by haemodynamic collapse.

DESIGN

Observational study.

SETTING

University hospital.

PATIENTS

Nine consecutive patients (eight male, one female; mean (SD) age, 36 (18) years) with arrhythmogenic right ventricular dysplasia presenting with ventricular tachycardia and haemodynamic collapse (n = 6) or ventricular fibrillation (n = 3), treated with an ICD.

MAIN OUTCOME MEASURES

Survival; numbers of and reasons for appropriate and inappropriate ICD interventions.

RESULTS

After a mean (SD) follow up of 32 (24) months, all patients were alive. Six patients received a median of 19 (range 2-306) appropriate ICD interventions for events detected in the ventricular tachycardia window; four received a median of 2 (range 1-19) appropriate ICD interventions for events detected in the ventricular fibrillation window. Inappropriate interventions were seen for sinus tachycardia (18 episodes in three patients), atrial fibrillation (three episodes in one patient), and for non-sustained polymorphic ventricular tachycardia (one episode in one patient).

CONCLUSIONS

Patients with arrhythmogenic right ventricular dysplasia and malignant ventricular arrhythmias have a high recurrence rate requiring appropriate ICD interventions, but they also often have inappropriate interventions. Programming the device is difficult because this population develops supraventricular and ventricular tachyarrhythmias with similar rates.

[Ventricular repolarization and Holter monitoring. Effect of sympathetic blockage on the QT/RR ratio]

Circadian variations of the QT interval and its heart rate dependency have been established. However, the respective roles of the sympathetic and parasympathetic nervous systems in their regulation are still undetermined. Eighteen healthy volunteers (average age 39 +/- 7 years, 10 men) were recruited and selected randomly to receive either placebo or atenolol (100 mg/day). The treatments were crossed after 7 days. The rate dependency of the QT was assessed by day and by night by 24 hour Holter ECG monitoring. The effects of atenolol on the rate dependency of the QT interval depend on the time of day. During the daytime, the QT rate dependency was reduced by atenolol (0.180 (0.162:0.198) versus 0.216 (0.195:0.236) with placebo, p < 0.01) whereas during the night, the QT rate dependency was the same in both groups. Therefore, the betablocker is associated with an inversion of the daily modulation of the QT rate dependency. The daytime rate-dependency of the QT interval in decreased with betablocker therapy. This result suggests a direct or indirect influence of the sympathetic nervous system on the rate dependency of ventricular repolarisation.

Analysis of the P wave with signal averaging to assess the risk of atrial fibrillation after coronary artery bypass surgery

P wave signal averaging was performed in 91 consecutive patients undergoing coronary artery bypass grafting to detect patients at risk of postoperative atrial fibrillation (AF). Sixteen patients (17.5%) developed AF after surgery. The P wave duration on the signal-averaged electrocardiogram (ECG) and on surface ECG was prolonged in AF patients compared to others (respectively 141 +/- 12 vs. 132 +/- 12 ms and 124 +/- 9 vs. 113 +/- 9 ms). The root mean square voltages (RMS) of the total P wave were not different between the two groups; the RMS of the late portion of the P wave (late RMS) was significantly higher (0.25 +/- 0.15 vs. 0.17 +/- 0.10 microV) and the RMS of the first 110 ms of the P wave (early RMS) significantly lower (0.88 +/- 0.28 vs. 1.09 +/- 0.33 microV) in AF. The late/ early RMS ratio was different (0.29 +/- 0.16 vs. 0.17 +/- 0.11). In a multivariate analysis only age and the late/early RMS ratio were predictive for AF.

Pacing induced sustained atrial fibrillation in a pony

A transvenous, screw-in electrode was implanted in the right atrium of a healthy pony and connected with an implantable pulse generator programmed to deliver bursts of electrical stimuli to the atrium. Initially, cessation of burst pacing resulted in short (less than 1 minute), self-terminating episodes of atrial fibrillation. As burst pacing continued, the episodes of induced atrial fibrillation became longer. After 3 weeks of continuous atrial pacing, atrial fibrillation became sustained (56 hours). This model of pacing induced atrial fibrillation can be used to study the mechanisms leading to atrial fibrillation, its perpetuation and therapy. Our preliminary observations support the concept that once atrial fibrillation starts, it sets up changes in the electrical characteristics of the atrium that favor its own perpetuation.

Lipid lowering drugs and recurrences of life-threatening ventricular arrhythmias in high-risk patients

OBJECTIVES

To evaluate a possible effect of lipid lowering drugs on recurrences of ventricular arrhythmias (VA) after implantable cardioverter defibrillator (ICD) implantation.

BACKGROUND

In patients with coronary artery disease (CAD), lipid lowering drugs reduce total and sudden cardiac death. Because the mechanism is not completely understood, we studied whether these drugs have a favorable influence on the occurrence of life-threatening VA in patients with CAD and ICD implants.

METHODS

We conducted an observational study in 78 patients with CAD and life-threatening VA, treated with an ICD. After ICD implantation, 27 patients were on treatment with lipid lowering drugs (group I) and 51 were not (group II). Patients were studied for the following end points: recurrences of VA requiring ICD intervention, cardiac death and hospitalization.

RESULTS

After a mean follow-up of 490 +/- 319 days, 35 patients (45%) had recurrences of VA requiring ICD intervention. In multivariate analysis, the use of lipid lowering drugs (chi-square 6.33, p = 0.012) and poorly tolerated sustained monomorphic ventricular tachycardia as initial presentation (chi-square 4.84, p = 0.028) remained as independent predictors of recurrences of VA. Patients in groups I and II had similar baseline clinical characteristics, but patients in group I had a lower incidence of recurrences of VA (6/27 or 22% vs. 29/51 or 57%, p = 0.004) and of the combined end points of cardiac death and hospitalization (4/27 or 15% vs. 23/51 or 45%, p = 0.015) compared with patients in group II.

CONCLUSIONS

This is the first observation that the use of lipid lowering drugs is associated with a reduction of recurrences of VA in patients with CAD and ICD implants. These data require confirmation in a prospective randomized trial.

[Clinical evaluation of a dual chamber implantable cardioverter-defibrillator]

Single-chamber ventricular cardioverter-defibrillator (ICD) has been shown to significantly reduce the incidence of sudden cardiac death due to malignant ventricular arrhythmias. However, inappropriate therapy due to supraventricular tachyarrhythmias (mainly atrial fibrillation) affects up to 34% of patients. Moreover, it has been estimated that up to 20% of ICD patients are in the need of physiological antibradycardia pacing. Use of dual-chamber ICD offers an atrial signal for better ability to discriminate atrial from ventricular tachyarrhythmias as well as a maintenance of AV synchrony, what may be of critical importance for patients with a compromised left ventricular function. In the present study we describe our preliminary clinical experience with a dual-chamber ICD's implanted in 20 patients. During the implantation and in-hospital testing, 95 induced VT/VF episodes were correctly diagnosed by ICD, as well as 28 induced FA episodes. Over a mean follow-up period of 10 +/- 6 months, 98 tachycardia episodes were recorded. All 76 VT/VF episodes were correctly diagnosed, as were 18 of 22 FA. Four FA episodes were diagnosed as VT/VF and treated by antitachycardia pacing in 2 cases and by shock in 2. Thus, sensitivity and specificity of VT/VF detection are 100% and 82% respectively. A dual-chamber ICD appears to improve discrimination of atrial from ventricular tachyarrhythmias without loss of sensitivity and to decrease occurrence of inappropriate therapy. AV synchrony, by improving the hemodynamic status of the patient (mainly in those with impaired left ventricular function), may demonstrate better survival and comfort of life.

Infarct size and recurrence of ventricular arrhythmias after defibrillator implantation

Infarct size as determined by perfusion imaging is an independent predictor of mortality after implantable cardioverter defibrillator (ICD) implantation in patients with coronary artery disease (CAD) and life-threatening ventricular arrhythmias (VA). However, its value as a predictor of VA recurrence and hospitalisation after ICD implantation is unknown. Therefore, the objective of this study was to evaluate whether infarct size as determined by perfusion imaging can help to identify patients who are at high risk for recurrence of VA and hospitalisation after ICD implantation. We studied 56 patients with CAD and life-threatening VA. Before ICD implantation, all patients underwent a uniform study protocol including a thallium-201 stress-redistribution perfusion study. A defect score as a measurement of infarct size was calculated using a 17-segment 5-point scoring system. Study endpoints during follow-up were documented episodes of appropriate anti-tachycardia pacing and/or shocks for VA and cardiac hospitalisation for electrical storm (defined as three or more appropriate ICD interventions within 24 h), heart failure or angina. After a mean follow-up of 470+/-308 days, 22 patients (39%) had recurrences of VA. In univariate analysis, predictors for recurrence were: (a) ventricular tachycardia (VT) as the initial presenting arrhythmia (86% vs 59% for patients without ICD therapy, P=0.04), (b) treatment with beta-blockers (36% vs 68%, P=0.03) and (c) a defect score (DS) > or = 20 (64% vs 32%, P=0.03). In multivariate analysis, VT as the presenting arrhythmia (chi2=5.51, P=0.02) and a DS > or = 20 (chi2=4.22, P=0.04) remained independent predictors. Cardiac hospitalisation was more frequent in patients with a DS > or = 20 (44% vs 13% for patients with DS < 20, P=0.015) and this was particularly due to more frequent hospitalisations for electrical storm (24% vs 3% for patients with DS < 20, P=0.037). The extent of scarring determined by perfusion imaging can separate patients with CAD into high- and low-risk groups for recurrence of VA and cardiac hospitalisation after ICD implantation.