Clinical Experience with Orthocor II Antitachycardia Pacing System for Recurrent Tachyarrhythmia Termination

Between June 1986 and December 1988, eight patients were treated with an Orthocor II 284 A antitachycardia pacemaker (Cordis Corp., Miami, FL, USA) forsupraventricular tachycardia (SVT) and ventricular tachycardia (VT) termination. Four patients had intra-AV nodal reentrant tachycardias; 1 patient had AV reentrant tachycardia with an atrio-nodal accessory bypass tract; 2 patients had AV reentrant tachycardias with concealed Kent bundle, and 1 patient had ventricular tachycardia. All patients had been treated with three or more drugs and were considered to be drug refractory. The programmed antitachycardia mechanism used for patients with SVT were: automatic overdrive in five patients and burst scanning in two patients. In the patient with VT, a critically timed double extrastimulus with fixed coupling interval was programmed. Follow-up ranged from 2 to 30 months. The pacemaker proved to be effective in terminating tachycardias in all cases with SVT; in the patient with VT, the programmed antitachycardia mechanism was effective for a long time, but after an episode of sustained VT not interrupted by the pacemaker, the patient underwent automatic cardioverter/defibrillator (AICD) implantation. Additional antiarrhythmic therapy was required in 3 patients to control their maximum sinus rate, in 1 patient to reduce tachycardia episodes and to enable termination, and in 2 patients to prevent spontaneous atrial fibrillation. It is concluded that Orthocor II is a flexible and versatile antitachycardia pacemaker providing a safe and effective control of recurrent tachycardia in selected patients.     

Programming Antitachycardia Pacing for Primary Prevention in Patients With Implantable Cardioverter Defibrillators: Results From the PROVE Trial

Programming ATP for ICD Patients. Objectives: The PROVE trial was designed to determine if antitachycardia pacing (ATP) is clinically beneficial for primary prevention in patients who have implantable cardioverter defibrillators (ICDs) or cardiac resynchronization therapy defibrillators (CRT‐Ds). Background: Use of ICDs and CRT‐Ds reduces mortality in patients with ventricular dysfunction and mild to moderate heart failure. However, in studies of the primary prevention population, shock‐only ICDs are predominantly used, without ATP programming for less painful termination of ventricular tachycardia (VT). Methods: We conducted a prospective, nonrandomized, multicenter study using market‐released ICDs and CRT‐Ds. Patients received devices programmed to deliver ATP for VT cycle lengths of 270–330 ms. Follow‐up evaluation was performed at 3, 6, and 12 months. The incidence of VT and the rate of successful termination by ATP were analyzed. Results: Of 830 patients in the study population (men, 73%; mean age, 67.3 ± 12 years), 32% received single‐chamber ICDs, 44% dual‐chamber ICDs, and 24% CRT‐Ds. ATP was attempted for 112 VT episodes in 71 patients, and 103 (92%) of the VT episodes were successfully terminated. Three VT episodes were accelerated by ATP and required termination by ICD shock; 6 episodes terminated spontaneously or by ICD shock. Conclusions: VT is common in patients without a history of this arrhythmia who have received ICDs or CRT‐Ds for primary prevention indications. Programming ICDs for ATP therapy at the time of implantation could potentially terminate most VT episodes and reduce the number of painful shocks for these patients. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1349‐1354, December 2010)     

Efficacy of intrinsic antitachycardia pacing for ventricular tachycardia refractory to conventional burst pacing: A case series

Intrinsic antitachycardia pacing (iATP) is a novel automated ventricular ATP algorithm that designs ATP sequences based on the analysis of prior failed ATP. Real-world data on the efficacy and safety of iATP are lacking. Among 124 ventricular tachycardia (VT) episodes in 130 consecutive patients (mean age at implantation: 63.8 ± 14.9 years; sex, 95 male and 35 female) for whom implantable cardioverter defibrillator or cardiac resynchronization therapy defibrillator equipped with iATP algorithm was implanted, we investigated the efficacy and safety of iATP for VT refractory to conventional burst pacing. Eight patients had a total of 17 episodes of iATP therapy after failed conventional burst pacing within 11.2 ± 6.6 months of follow-up. Eleven VT episodes (64.7%) in seven patients (87.5%) were successfully terminated by iATP, and only one patient (12.5%) experienced VT acceleration. iATP might be useful for VTs refractory to conventional burst pacing with a low risk of VT acceleration.     

Comparison of burst versus ramp antitachycardia pacing therapy for ventricular tachycardia: A meta-analysis

Current guidelines recommend at least one attempt of defibrillator antitachycardia pacing (ATP) therapy, showing preference for burst therapy. The objective of this study is to compare ramp versus burst ATP therapy proportion of success and acceleration in treating spontaneous or induced ventricular tachycardia (VT). The review protocol was previously published in PROSPERO. Data synthesis and measures of heterogeneity (I²) was performed by CMA® software v.3 comparing proportions in both groups. Sensitivity analysis was performed as subgroup or meta-regression according to quality, clinical characteristics, and differences in design. Thirteen studies including 30,117 VT episodes in 1672 patients were analyzed. There was no significant difference in the proportion of success between burst and ramp therapy in spontaneous VT (odds ratio = 1.116; 95% confidence interval [CI] = 0.788–1.579; I² = 89%). There was no significant difference in the proportion of success between burst and ramp therapy in induced VT (odds ratio = 0.820; 95% CI = 0.468–1.437; I² = 93%). No significant difference was found in the proportion of acceleration between burst and ramp in spontaneous VT (odds ratio = 0.792; 95% CI = 0.476–1.317; I² = 83%). No significant difference was found in the proportion of acceleration between burst and ramp in induced VT (odds ratio = 1.234; 95% CI = 0.802–1.898; I² = 55%). Sensitivity analysis did not change main results. There is no difference in success or in acceleration proportion between burst or ramp ATP therapy irrespective if the VT was spontaneous or induced. Future implantable cardioverter defibrillator programming guidelines should offer both ATP therapies without preference in one of them.     

Efficacy of Atrial Antitachycardia Functions for Treating Atrial Fibrillation: Observations in Patients with a Dual-Chamber Defibrillator

In patients with conventional indication for ICD implantation, atrial fibrillation may occur in more than 50% during the life-span of the device and may lead to severe adverse events. Dual chamber defibrillators with atrial antitachycardia functions, including prevention algorithms, arrhythmia detection capability and atrial therapy options (antitachy pacing and cardioversion) have been recently introduced. The aim of this review is to examine the effectiveness of these new devices and to identify patients who may benefit. We recently studied 112 patients who received the device because of life-threatening ventricular arrhythmias. Fifty-five percent of them had atrial fibrillation prior to implantation. During the follow-up (one year on average), 27% had at least one episode of sustained atrial tachyarrhythmia. Effectiveness of atrial antitachy pacing was 71% on regular atrial tachycardia and 36% on irregular atrial tachyarrhythmias. Atrial shock efficacy was over 90% when adequately programmed. Interestingly, near half of the episodes started as regular atrial tachycardia and accelerated and became less organized in few minutes. Early delivery of antitachy pacing may increase success rate and decrease the need for atrial shock. Furthermore, it may prevent atrial remodeling and reduce atrial fibrillation burden.Based on our experience, we recommend that all patients with a class I indication for defibrillator implantation (related to risk of ventricular arrhythmias) who have a history of or are at risk of developing atrial tachyarrhythmias should receive a dual chamber defibrillator equipped with atrial antitachycardia functions. Furthermore, patients either with a history of heart failure, with poor functional capacity (functional class III or IV), depressed left ventricular ejection fraction, a need for monitoring of atrial rhythm, or in whom there is some concern about appropriate detection of ventricular arrhythmias, may benefit from a single device capable of managing ventricular and supraventricular arrhythmias.     

Mayo Clinic VT calculator: A practical tool for accurate wide complex tachycardia differentiation

The discrimination of ventricular tachycardia (VT) versus supraventricular wide complex tachycardia (SWCT) via 12-lead electrocardiogram (ECG) is crucial for achieving appropriate, high-quality, and cost-effective care in patients presenting with wide QRS complex tachycardia (WCT). Decades of rigorous research have brought forth an expanding arsenal of applicable manual algorithm methods for differentiating WCTs. However, these algorithms are limited by their heavy reliance on the ECG interpreter for their proper execution. Herein, we introduce the Mayo Clinic ventricular tachycardia calculator (MC-VTcalc) as a novel generalizable, accurate, and easy-to-use means to estimate VT probability independent of ECG interpreter competency. The MC-VTcalc, through the use of web-based and mobile device platforms, only requires the entry of computerized measurements (i.e., QRS duration, QRS axis, and T-wave axis) that are routinely displayed on standard 12-lead ECG recordings.     

Transcatheter cryotherapy for the treatment of supraventricular tachyarrhythmias in children: A single center experience

Introduction Transcatheter cryotherapy is an emerging technology for the treatment of children with supraventricular tachyarrhythmias. Limited data exist regarding the use of cryoablation therapy in children. We report a single center’s experience with transcatheter cryoablation in the pediatric population.Methods and results A retrospective review of demographic, procedural and outcome data was performed for patients undergoing cryoablation for treatment of supraventricular tachycardia (SVT). A historical control group was taken from the 3 years preceding the introduction of cryoablation. Between August 2003 and November 2005, 83 cryoablation procedures were performed in 81 patients (age: 4 to 21 years, mean: 13.4 years) for AV nodal reentrant tachycardia (AVNRT—53), AV reentrant tachycardia (AVRT—20), ectopic atrial tachycardia (EAT—9), and junctional ectopic tachycardia (JET—1). The acute success rate for all procedures was 88% (AVNRT: 96%, AVRT: 85%, EAT: 55%, and JET: 100%). Of 72 patients that underwent successful cryoablation, nine experienced recurrence of SVT (12.5%). The control group consisted of 73 patients (AVNRT − 60, AVRT − 13). There were no differences in demographic data between the two groups. The overall success rate for the RFA group (96%) was identical to that for patients with AVNRT and AVRT undergoing cryoablation. The recurrence rate for RFA (10%) was less but not significantly different than that for cryoablation (12%). There were no complications in either group.Conclusions Cryoablation is a safe and effective alternative for the treatment of SVT in children.The authors received no financial support in relation to this study. One of the authors (Dick II) owns common stock in CryoCath Technologies.     

Acute physical and mental stress resulted in an increase in fatty acids,norepinephrine, and hemodynamic changes in normal individuals: A possible pathophysiological mechanism for hypertension—Pilot study

Hypertension is often associated with metabolic changes. The sustained increase in sympathetic activity is related to increased blood pressure and metabolic changes. Environmental stimuli may be related to increased sympathetic activity, blood pressure, and metabolic changes, especially in genetically predisposed individuals. The aim of this study was to evaluate the response of fatty acids to physical and mental stress in healthy volunteers and the hemodynamic, hormonal, and metabolic implications of these stimuli. Fifteen healthy individuals with a mean age of 31 ± 7 years, of both sexes, were evaluated. They were assessed at baseline and after combined physical and mental stress (isometric exercise test, Stroop color test). Blood samples were collected at baseline and after stimulation for glucose, insulin, fatty acid, and catecholamine levels. Blood pressure, heart rate, cardiac output, systemic vascular resistance, and distensibility of the large and small arteries were analyzed. The data obtained at baseline and after stimuli were from the same individual, being the control itself. Compared to baseline, after physical and mental stress there was a statistically significant increase (p < .05) in free fatty acids, norepinephrine, diastolic blood pressure, peripheral vascular resistance, and distensibility of the large and small arteries. In conclusion, the combination of physical and mental stress raised fatty acids, norepinephrine, diastolic blood pressure, and peripheral vascular resistance in healthy individuals.     

A Novel Catheter Design for Laser Photocoagulation of the Myocardium to Ablate Ventricular Tachycardia

Nd:YAG laser energy has been proposed as an alternative to radiofrequency energy for ablation of ventricular tachycardia (VT) associated with coronary artery disease (CAD) in an effort to increase lesion size and success rates. However, issues of catheter design to maintain flexibility and ensure adequate tissue contact have hindered development of laser catheters.We developed and tested a prototype 8 Fr. steerable catheter with a flexible and extendible tip (designed to ensure tissue contact and efficient ventricular mapping), which projects the laser beam through a side port containing a lens-tipped optical fiber that rests against the endocardial surface. The catheter has a channel for simultaneous saline irrigation to displace the interceding blood and discharge a laser beam between two electrodes for bipolar mapping and a thermocouple for temperature monitoring. The catheter was tested on bench top using the epicardial surface of freshly slaughtered bovine hearts and in vivo using six anaesthetized closed-chest sheep. In vitro experiments demonstrated that lesion size increased linearly with applied power up to 40 watts. When compared to radio frequency, laser energy penetrated more deeply into the myocardium. In the in vivo studies, using increasing powers of up to 40 watts for application times of 60 to 120 seconds created circular or elliptical lesions with surface dimensions up to 12 mm × 12 mm and depth of 9 mm (full LV wall thickness with a mean lesion diameter of 9.9 ± 5.2 mm and depth 5.8 ± 3.2 mm). Most lesions, 16 total in both right and left ventricular walls were transmural or near transmural in thickness. Lesions demonstrated coagulation necrosis with smooth well-demarcated borders. No animal suffered cardiac perforation, hypotension, hemopericardium, damage to cardiac valves, or cavitation effect from any of the ablations. Runs of VT were seen during energy application at the highest laser outputs in two animals.In conclusion, this catheter design provides effective endocardial delivery of laser energy and is capable of creating transmural or nearly transmural lesions in vivo and in vitro, thereby potentially increasing the efficiency of VT ablation in CAD patients.     

Atrial Macroreentry Involving the Myocardium of the Coronary Sinus: A Unique Mechanism for Atypical Flutter

Macroreentry Involving the Coronary Sinus. Atrial flutter involving either clockwise or counterclockwise rotation around the tricuspid annulus utilizing the subeustachian isthmus has been well described. However, macroreentrant atrial circuits in atypical atrial flutter in patients who have not undergone previous surgery or without atrial disease are not well defined. We describe a patient without structural heart disease who presented with an atrial macroreentrant rhythm. Entrainment mapping demonstrated a critical isthmus within the coronary sinus. Activation mapping demonstrated double potential throughout the length of the coronary sinus with disparate activation sequences. A circuit involving the myocardium of the coronary sinus, exiting in the lateral left atrium, down the interatrial septum, and reentering into the coronary sinus was identified. Successful ablation of the rhythm was accomplished by a circumferential radiofrequency application within the coronary sinus.