Comparison of defibrillation thresholds using monodirectional electrical vector versus bidirectional electrical vector.

BACKGROUND: Currently, two main lead configurations are used for implantable cardioverter-defibrillators (ICD). One generates a monodirectional electrical vector by using the can surface as an active part (hot can) together with a right ventricular defibrillation coil. The other one (TRIAD) produces a bidirectional electrical vector by adding a proximal defibrillation electrode on the same lead. The purpose of this prospective study was to determine whether there is a difference between these configurations in terms of the acute defibrillation threshold (DFT). The secondary objective was to evaluate the possible sequential effect of successive arrhythmia induction and defibrillation shocks on the final DFT value. METHODS: In 44 patients (37 males, 7 females, mean age 59.18 +/- 12.05 years; mean ejection fraction 35.21 +/- 11.69%), a Hot Can Ventak family ICD (Guidant, St. Paul, MN, USA) was implanted in a left pectoral pocket. During the implant procedure, step-down to failure DFT testing was performed twice in each patient using the two different above-mentioned configurations: the bidirectional and the monodirectional. The first configuration to be tested was determined by a 1:1 randomization by center. RESULTS: The step-down DFT protocol was followed in 35 patients. The average DFT was 8.6 +/- 4.0 J for TRIAD and 10.4 +/- 4.3 J for the monodirectional (p = 0.009) lead configuration; this represents a 16.3% decrease in the DFT using a bidirectional configuration. Furthermore, no relationship between the final DFT and the number of ventricular fibrillation inductions and shocks received was observed, confirming the secondary objective. CONCLUSIONS: Compared to the monodirectional electrical vector, the bidirectional electrical vector is clearly more beneficial for the patient.

Different patterns of atrial activation in idiopathic atrial fibrillation: simultaneous multisite atrial mapping in patients with paroxysmal and chronic atrial fibrillation.

OBJECTIVES: We aimed to evaluate: 1) the behavior of electrical activity simultaneously in different atrial regions during atrial fibrillation (AF); 2) the difference of atrial activation between paroxysmal and chronic AF; 3) the atrial refractoriness dispersion; and 4) the correlation between the effective refractory periods (ERPs) and the FF intervals. BACKGROUND: Little data exist on the electrophysiologic characteristics of the different atrial regions in patients with AF. A more detailed knowledge of the electrical activity during AF may provide further insights to improve treatment of AF. METHODS: Right and left atria were extensively mapped in 30 patients with idiopathic AF (18 paroxysmal and 12 chronic). In different atrial locations, we analyzed 1) the FF interval duration; and 2) the grade of organization and, in case of organized electrical activity, the direction of atrial activation. Furthermore, in patients with paroxysmal AF, we determined the atrial ERP, evaluated the ERP dispersion and assessed the presence of a correlation between the ERPs and the FF intervals. RESULTS: In patients with chronic AF, we observed a shortening of the FF intervals and a greater prevalence of disorganized activity in all the atrial sites examined. In patients with paroxysmal AF, a significant dispersion of refractoriness was observed. The right lateral wall showed longer FF intervals and more organized atrial activity and, unexpectedly, the shortest mean ERPs. In contrast, the septal area showed shorter FF intervals, greater disorganization and the longest mean ERPs. CONCLUSIONS: Electrical activity during AF showed a significant spatial inhomogeneity, which was more evident in patients with paroxysmal AF. The mean FF intervals did not correlate with the mean ERPs.

Atrial mapping by basket catheter in patients with atrial fibrillation submitted to linear ablation.

Recently non-pharmacological therapies for atrial fibrillation (AF) have been developed. The electrophysiological mechanisms of AF is thought to be the development of multiple reentrant wavelets circulating around anatomic barriers and variable regions of functional conduction block responsible of the perpetuation of the arrhythmia. Also the role of the triggering foci has been highlighted. To cure AF by means of non pharmacological therapy we may eliminate and/or modify the substrate. To better understand the mechanism underlying the AF and to choose the best ablation strategy is of fundamental importance to map the right and the left atrium during AF. Our experience shows that in chronic idiopathic AF disorganized atrial activity is observed at all atrial regions while in paroxysmal idiopathic AF the left septum and the right atrial posterior areas are highly disorganized while the lateral region shows more organized atrial electrical activity. Multipolar basket catheters are extremely useful in mapping right and left atrium in order to guide the best ablation strategy.

Should stimulation therapy for congestive heart failure be combined with defibrillation backup?

Biventricular pacing has been proposed to resynchronize ventricular contraction in patients with congestive heart failure (CHF) and interventricular conduction delay. However, the sudden death rate is still high despite the improvement in cardiac performance. Devices combining biventricular pacing with implantable cardioverter defibrillator (ICD) backup are now under clinical investigation to demonstrate whether they can decrease sudden death. From the first implant of an ICD with biventricular transvenous pacing on August 1998 to April 2000, 96 patients underwent such implants: 67 (70%) received pacemakers alone and 29 (30%), who had class I ICD indications, received combined pacemaker/ICD systems. During a mean follow-up of 283 +/- 170 days, 13 (14%) patients died: 5 of 29 (17%) in the ICD group and 8 of 67 (12%) in the pacemaker group. A total of 15 patients (52%) had ICD shocks and 6 patients (21%) had 113 episodes of ventricular tachyarrhythmias, of which 96 (85%) were converted to sinus rhythm with antitachypacing. The echocardiograms showed a narrowing of the delay between the onset of right and left ventricular outflow from 40 +/- 37 msec to 17 +/- 16 msec (p = 0.03) and a reduction of the mitral regurgitation area from 7 +/- 3.8 cm2 to 5 +/- 4 cm2 (p = 0.04) at 3 months. Functional class improved from 2.8 +/- 0.7 to 1.6 +/- 0.5 (p <0.001) 3 months after implant. Thus, ischemic patients with reduced left ventricular ejection fraction and ventricular tachyarrhythmias seem good candidates for biventricular pacing with ICD backup. The sudden death risk for those with idiopathic dilated cardiomyopathy, however, is difficult to stratify, and the choice of ICD backup has to be considered on the basis of patient safety, as well as of costs.

Efficacy of biventricular sensing and treatment of ventricular arrhythmias.

While much is known concerning the hemodynamic effects of biventricular (BV) pacing, little has been reported concerning the efficacy of BV sensing and pacing in the detection and treatment of ventricular tachyarrhythmias. Two hundred nineteen heart failure (HF) patients with VT or VF and a QRS > or = 120 ms during sinus rhythm received an ICD capable of BV pacing and sensing. Detection times of induced VF and success rates for terminating induced VT were measured. The ICD system used a left ventricular epicardial lead implanted via thoracotomy (52 patients) or a specially designed percutaneous, over-the-wire lead inserted in the coronary venous system. VF detection times and VT termination rates by antitachycardia pacing (ATP) were compared with those measured in a population of recipients of ICD using a RV lead alone. Median induced VF detection times were comparable (2.0-s BV vs 1.8-s RV). Termination of induced VT on the first attempt was comparable with BV pacing (87.4%) versus RV pacing (89.6%). The time to detect induced VF was not different with ICDs using BV sensing versus conventional ICDs using RV sensing alone. Similarly, the rates of successful termination of induced VT by ATP with BV or RV pacing were comparable.

Impact of biventricular pacing on mortality in a randomized crossover study of patients with heart failure and ventricular arrhythmias.

Biventricular (BV) pacing is under clinical investigation for the treatment of heart failure. Its impact on mortality is unknown. Patients with heart failure and ventricular tachyarrhythmias received an implantable cardioverter defibrillator with BV pacing capability. Patients were randomized 1:1 to BV pacing or no pacing, then crossed over to the alternate mode after 3 months. All-cause mortality was measured in each arm up to the point of crossover. Fifteen of 222 patients died between implant and crossover. Five patients died while programmed to BV pacing and 19 died while programmed to no pacing. Survival in the BV pacing arm was 93 +/- 4% versus 86 +/- 6% in the no pacing arm (P = 0.18). In a patient population with symptomatic heart failure and ventricular arrhythmias, BV pacing does not appear to be associated with excess mortality. Larger and longer studies will be needed to determine if BV pacing confers a survival benefit.

Performance of a new steroid-eluting coronary sinus lead designed for left ventricular pacing.

The Ventak CHF/CONTAK CD Biventricular Pacing Study is a prospective randomized trial to examine the safety and efficacy of biventricular (BV) pacing in patients with standard indications for an ICD, symptomatic heart failure, a LVEF < or = 0.35, and a QRS > or = 120 ms. Patients underwent implantation of a BV pacing and sensing system with backup defibrillation capability, which includes a steroid-eluting coronary venous lead that is advanced into the coronary venous vasculature by over-the-wire techniques. LV pacing threshold, BV impedance, and BV R wave amplitude were measured in 58 consecutive patients. Using a percutaneous over-the-wire insertion technique, steroid-eluting coronary venous leads were associated with satisfactory mean LV pacing threshold, BV impedance, and BV R wave amplitude acutely up to 4 months after implantation. Pacing threshold stabilized 2 weeks after lead implantation and sensing threshold remained stable from the time of implant.

[Idiopathic ventricular tachycardia with onset in the verapamil-sensitive left ventricle: the clinical characteristics and long-term follow-up of 37 patients]. / Tachicardia ventricolare idiopatica ad insorgenza dal ventricolo sinistro sensibile al verapamil: caratteristiche cliniche e follow-up a lungo termine di 37 pazienti.

BACKGROUND: Idiopathic verapamil-responsive left ventricular tachycardia (IVRLVT) is a rare, well known form of ventricular tachycardia. Issues concerning long-term prognosis, drug prophylaxis and non-pharmacological therapy are rarely reported in the literature. We report the long-term follow-up, the efficacy of various drugs in the prophylaxis and the role of catheter ablation in a large group of patients with IVRLVT. METHODS AND RESULTS: This retrospective study involves 37 patients with a mean age of 28.3 +/- 14.8 years at first IVRLVT episode. The tachycardia morphology was typically with a right bundle-branch block configuration in all cases, with left axis deviation in 33 and right axis deviation in 5 (one patient had the 2 morphologies). Four patients had a mitral valve prolapse; the remaining 33 patients had neither clinical nor echocardiographic signs of heart disease. Only sporadic ventricular extrasystoles were detected at Holter monitoring in 73% of cases; 30% of patients had positive criteria for the presence of late potentials at signal averaged ECG. During electrophysiologic study, the tachycardia could be easily induced in 91% of patients. Mean follow-up is 7.3 +/- 4.7 years; all patients are alive at the end of follow-up. A mean of 2.3 +/- 1.2 drugs was prescribed in 35 patients (94.6%); betablockers were effective in 66% of the cases, verapamil in 20%, class I drugs in 22%, class III drugs in 15%. Both the 2 patients, who never received prophylaxis, and the 4 who stopped medication, utilize verapamil in case of recurrences. Eight patients were submitted to catheter ablation, with DC shock the first 2 patients, with RF energy from the third on; all but one (with DC shock) were successfully cured. CONCLUSIONS: Long-term follow-up confirmed the good prognosis of this form of ventricular tachycardia; a new insight that has been addressed about prophylaxis is the high efficacy of betablockers in preventing relapse and the poor efficacy of verapamil per os in chronic prophylaxis. Radiofrequency catheter ablation is effective and safe, using the earliest ventricular potential and the pace-mapping reproducing the same morphology of the tachycardia in all the 12 leads as a marker to identify the site of RF application, and may be proposed to all patients suffering from frequent episodes of IVRLVT.

[Usefulness of a protocol for carotid sinus massage in supine and erect postures in patients with syncope without other cardiovascular or neurological diseases]. / Utilità di un protocollo di massaggio del seno carotideo in clino ed ortostatismo in pazienti con sincope senza altre patologie cardiovascolari o neurologiche.

BACKGROUND: Carotid sinus massage is a first level test when investigating the cause of syncope. It is normally performed in the supine and erect positions. However, there is no standard complete protocol. So we have devised a new protocol to evaluate the utility of carotid sinus massage in different postures and the influence of patients age on the response. METHODS: Two groups of subjects were selected: a group of 167 patients (mean age 50 ys +/- 18, 105 males, 62 females) with a history of syncope without cardiovascular and neurological disease and 20 asymptomatic control subjects (mean age 52 ys +/- 13, 11 males, 9 females). Carotid sinus massage was performed supine, just after passive tilt, after 5 minutes of tilt and just after passive return to supine. If a pause > 3" was detected, the protocol was repeated after atropine i.v. injection. DEFINITIONS: Borderline vasodepressor: blood pressure reduction > 30 but < 50 mm Hg without symptoms; vasodepressor: blood pressure reduction > 50 mm Hg or > 30 mm Hg with symptoms like dizziness, vertigo or syncope; cardioinhibitory: pause > 3"; mixed: cardioinhibitory with blood pressure reduction > 30 mm Hg after atropine. RESULTS: Carotid sinus massage gave all informations in the supine position in 14 (12%) patients, after passive tilt in 67 (57%), after 5 minutes of tilt in 30 (26%), and after return to supine in 6 (5%). The responses were: 13 (8%) borderline vasodepressor, 32 (19%) vasodepressor, 2 (1%) cardioinhibitory, 70 (42%) mixed, 50 (30%) negative. Positive responses were more frequent in patients over 45 years (90% versus 43%). In the control group only 3 (15%) positive responses were elicited (2 borderline vasodepressor, and 1 vasodepressor, all in subjects over 45). CONCLUSIONS: This protocol for carotid sinus massage evidenced positive responses in 70% of patients with syncope without cardiovascular and neurological disease; cardioinhibitory responses are rare (2%); positive responses are more frequent in patients over 45 years; the protocol specificity was 85%.

[Ablation of supraventricular paroxysmal nodal reentrant tachycardia]. / Ablazione del circuito delle tachicardie parossistiche sopraventricolari da doppia via nodale.

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most frequent supraventricular tachycardia. The reentry circuit had been said to be localized within the AV node for many years and the first non pharmacological therapy was the surgical or catheter ablation of the AV node. This was, however, too high a price for a generally well tolerated and non life-threatening arrhythmia. Only recently, the endocardial mapping and the results of surgical perinodal dissection showed that part of the reentry circuit was localized in the atrial myocardium near the AV node. The first approach was the ablation of the fast pathway as it is easier to map during AVNRT. However, this pathway is located very close to the AV node, so that its ablation is complicated by a percentage of AV block that is too high (6.2%) considering the good prognosis of this arrhythmia. In order to reduce this risk, the ablation of the slow pathway which is located more posteriorly and more distant from the AV node, was then proposed. Three different approaches have been suggested; one purely anatomic and the other two guided by electrophysiologic markers. If the posterior and middle part of the septum during sinus rhythm is mapped, more posteriorly, near the coronary sinus os, the sharp potential, described by Jackman, is recorded. It is a sharp spike with a high amplitude, associated with an atrial electrogram of very low amplitude. It cannot be modified by atrial pacing and may also be recorded during the uncommon form of AVNRT.(ABSTRACT TRUNCATED AT 250 WORDS)

[Nodal reentry tachycardia: short- and long-term effectiveness and safety of a selective ablation technique of the slow pathway]. / Tachicardia da rientro nodale: efficacia e sicurezza a breve e lungo termine di una tecnica di ablazione selettiva della via lenta.

BACKGROUND: Various ablation methods have been proposed in the last few years in order to find a radical solution for atrioventricular nodal reentrant tachycardia. The first techniques were surgical, followed by modulation of the fast pathway, causing a prolongation of the P-R interval, the latter involving a 2 to 10% atrioventricular block risk. To reduce this risk, slow pathway ablation was then suggested, with the objective of abolishing atrioventricular reentry. The aim of our study was to evaluate how frequently the recording of peculiar slow potentials was possible in patients with atrioventricular nodal reentrant tachycardia, and to assess short-and long-term efficacy of an ablation technique involving the use of these potentials as electrophysiologic markers. METHODS: One hundred and eighty-eight patients with typical atrioventricular nodal reentrant tachycardia were studied (mean age 47 +/- 18 years). Radiofrequency ablation was guided by peculiar slow potential recordings; when this was not possible, fast pathway ablation, or slow pathway ablation guided only by anatomic markers, were performed. RESULTS: Potentials with peculiar electrophysiologic characteristics were found during sinus rhythm in the median posterior region of the septum, anteriorly to the coronary-sinus ostium, in 92% of patients. These characteristics included: low amplitude; the fact that they occupy the first part of the interval between the atrial and ventricular electrogram; their amplitude diminishes and disappears with increased frequency of atrial stimulation and/or with atrial extrastimulus. Typical atrioventricular nodal reentry tachycardia was no longer inducible in any patient at the end of the procedure with a median of 2 radiofrequencies application per patient. No II or III degree atrioventricular block was caused when ablation was guided by slow potential recordings. During an attempt at fast pathway ablation a complete atrioventricular block was caused in 1 patient. One hundred and eighty-four patients remained asymptomatic during a follow-up of 2 to 24 months; no one showed either a modification of atrioventricular conduction if compared to that found at hospital discharge or proarrhythmic effects. Four patients had one atrioventricular nodal reentrant tachycardia recurrence and a second successful ablation was performed in 2 of these 4 patients. CONCLUSIONS: Peculiar slow potentials, that can be used as electrophysiologic markers for slow pathway ablation, were recorded in the medio-posterior region of the septum in the majority of patients. The fact that this technique, using slow potential as an electrophysiologic marker, was successful in all patients, with very few recurrences and with no serious complications (no II or III degree atrioventricular block) makes it trustworthy and safe.

Catheter ablation of accessory pathways in patients with Wolff-Parkinson-White syndrome.

PATIENTS: Fifty-two patients with Wolff-Parkinson-White syndrome underwent transcatheter ablation. All patients were symptomatic. Eighteen had documented episodes of atrial fibrillation, 14 of which also had reentrant tachycardias; the remaining 34 had only episodes of reentrant tachycardias. Forty-nine patients had both anterograde and retrograde conduction through the accessory pathway; 3 had retrograde conduction alone; 2 patients had 2 accessory pathways and 1 had 3. All patients were resistant or intolerant to at least 2 antiarrhythmic drugs. METHODS: All patients were treated with radiofrequency current. Ablation was considered successful if the anterograde and retrograde conduction were completely abolished. Ablation was considered unsuccessful if ablation of only 1 pathway in patients with 2 or more accessory pathways and/or modification of the accessory pathway conduction without interruption was achieved. RESULTS: Accessory pathway ablation was successfully performed in 46 out of 52 patients (88%). Fifty out of 56 accessory pathways were effectively ablated (89%). Thirty-eight required a single session of ablation and 8 additional patients were successfully ablated during a second session. The number of radiofrequency current applications ranged from 2 to 13 (mean 4.1 +/- 2.5). The mean duration of the sessions was 4.30 +/- 1.50 hours (range 2.30 to 9). The mean radiation exposure for session was 55 +/- 25 minutes (range 20 minutes to 2.30 hours). Complications were observed in 2 out of 52 patients. One patient had a transient II degree type 1 atrioventricular block; another patient with severe arterial hypertension had a mild hemorrhagic stroke with complete neurological remission. FOLLOW-UP. Forty-five out of the 46 patients in whom ablation was successful were asymptomatic for arrhythmias during a mean follow-up of 8 months (range 4 to 16), without antiarrhythmic treatment, and without reappearance of preexcitation. One patient showed reappearance of preexcitation at electrocardiogram one month after the ablation, followed by an episode of reentrant tachycardia; this patient underwent a second successful ablation session. CONCLUSIONS: Our results show that ablation techniques have high success rates with no serious complications.

Short- and long-term effects of propafenone in ventricular arrhythmias.

The effectiveness of short- (15 days) and long- (12 months) term propafenone treatment was assessed in 53 patients presenting with more than 30 premature ventricular complexes per hour as detected by 24-hour ambulatory Holter monitoring. Thirty-nine patients had no apparent concomitant heart disease while 14 had chronic coronary artery disease. The effects of propafenone were analysed by ambulatory Holter monitoring after 15 days and at 3, 6 and 12 months. The initial dose was 150 mg four times daily and was increased up to 300 mg four times daily when necessary. Favourable short-term effects were obtained in 39 patients (73.6%). After 12 months, 17 patients (32.1%) were still on propafenone treatment with good results. Treatment was discontinued on account of low compliance in 28.3%. This was because treatment was ineffective even at high doses in 15.2%, because of severe side effects in 13.2%, because of proarrhythmic effects in 5.6% and for other causes in 5.6%.

[Control of the efficacy of anti-arrhythmia drug therapy with the ambulatory electrocardiogram. Proposal for a new analytical statistical model]. / Controllo dell'efficacia della terapia antiaritmica con elettrocardiogramma dinamico. Proposta di un nuovo modello statistico di analisi.

Ambulatory electrocardiography is used for evaluating antiarrhythmic drug effectiveness. Statistical methods based on the analysis of the number of ventricular ectopic beats are currently employed. These techniques are not useful to compare groups of patients with different therapies, due to the wide spontaneous variability of the ectopic beats. We propose a new statistical method, based on the likelihood function. The new method has been tested both retrospectively on 102 patients treated with different antiarrhythmic drugs and prospectively on 12 patients subjected to three consecutive control ambulatory electrocardiograms and to a fourth one after treatment with propafenone. This new statistical method was found to be useful for comparing therapeutic effectiveness between groups of patients, whereas the traditional quantitative methods are to be preferred when drug effectiveness is evaluated in the single patient.

Holter monitoring and provocative maneuvers in assessment of unipolar demand pacemaker myopotential inhibition.

Myopotential inhibition was produced by a combination of different provocative maneuvers in 423 (77%) out of 550 consecutive unipolar pacemaker patients. The most useful maneuvers were the hand-to-shoulder press (90% positivity) and the hand-to-hand press (60% positivity). Three groups of 20 patients were then submitted to 24 hours of Holter monitoring. Group A during the provocative maneuvers had shown myopotential inhibition and symptoms of cerebral ischemia. In group B symptomless myopotential inhibition had been induced. Group C had no myopotential inhibition nor symptoms during the tests. Abnormal pacemaker pauses related to myopotential inhibition were recorded during Holter monitoring in 90% of group A and in 80% of group B patients, but only group A patients showed symptoms. Thus in patients who are able to practice provocative isometric maneuvers and who can be selected according to their response, Holter monitoring seems to offer few advantages in discovering myopotential inhibition and related symptoms.

[Spontaneous changes of ventricular ectopic beats in ischemic patients and subjects without other signs of cardiopathy]. / Variabilità spontanea dei battiti ectopici ventricolari in pazienti ischemici ed in soggetti senzi altri segni di cardiopatia.

Spontaneous variability of premature ventricular complexes was evaluated by 72 hour continuous ambulatory electrocardiographic monitoring in 38 patients. Nineteen patients had coronary artery disease and 19 subjects had no documented signs of cardiac disease. Using multifactorial analysis of variance we determined the minimal percent reduction of premature ventricular complexes frequency that could not be ascribed to spontaneous variability alone in both single subject and in groups of 10 and 19 individuals and analyzed the difference between the two groups of ischemic and healthy patients. Our results show that in each subject with or without coronary artery disease the minimal reduction of premature ventricular complexes is similar: 71% and 72% respectively. On the other hand when the two groups were compared the percentage of reduction was 49% in healthy subjects and 40% in patients with coronary artery disease. Spontaneous variability of premature ventricular complexes decreases as the period of monitoring lengthens; however the improvement obtained with longer electrocardiographic monitoring doesn't justify the prolongation of the examination beyond 24 hours.