Per Insulander

Acute and long-term outcome of cryoablation therapy of typical atrioventricular nodal reentrant tachycardia

AIMS The purpose of this study was to evaluate the safety and efficacy of cryoablation in a large series of patients with typical (slow-fast) atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS Between 2003 and 2007, 312 patients with typical AVNRT--median age of 53 years (range 10-92), 200 women (64%)--underwent cryoablation, using exclusively a 6 mm tip catheter tip. Acute success was achieved in 309 of 312 patients (99%). The overall recurrence rate was 18 of 309 (5.8%) during a mean follow-up of 673 +/- 381 days. Sixteen of these patients (89%) were successfully reablated. The recurrence rate was 9% in patients with residual dual atrioventricular (AV) nodal pathway post-ablation compared with 4% in those with complete elimination of slow pathway conduction (P = 0.05). No patient developed permanent AV block. CONCLUSION Cryoablation of AVNRT can be achieved with a high acute success rate and a reasonable recurrence rate at long-term follow-up. Complete abolition of slow pathway conduction seems to predict better late outcome.

Gender differences in electrophysiologic effects of mental stress and autonomic tone inhibition: A study in healthy individuals

Introduction: Gender differences exist in electrophysiologic properties and the occurrence of certain arrhythmias. Mental stress may trigger serious arrhythmias, including ventricular tachycardias and ventricular fibrillation. This study investigates gender differences in the electrophysiologic effects on different levels of the cardiac conduction system elicited by mental stress and autonomic tone inhibition.

High success rate with cryomapping and cryoablation of atrioventricular nodal reentrytachycardia.

Introduction: Cryoablation is a new alternative to radiofrequency (RF) ablation for treatment of atrioventricular nodal reentry tachycardias (AVNRT). Mapping with reversible effect on the arrhythmia substrate or the AV node can be done before irreversible ablation is performed. This study evaluates an approach with systematic cryomapping, ablating only in areas with prompt effect on the arrhythmia substrate and evaluates whether the success rates and procedure times are similar to RF ablation.

Cryoablation of substrates adjacent to the atrioventricular node: acute and long-term safety of 1303 ablation procedures

AIMS Radiofrequency (RF) ablation is effective for ablation of atrial arrhythmias. However, RF ablation in the vicinity of the atrioventricular (AV) node is associated with a risk of inadvertent, irreversible high-grade AV block, depending on the type of substrate. Cryoablation is an alternative method. The objective was to investigate the acute and long-term risks of AV block during cryoablation. METHODS AND RESULTS We studied 1303 consecutive cryoablations of substrates in the vicinity of the AV node in 1201 patients (median age 51 years, range 6-89 years) on acute and long-term impairment to the AV nodal conduction system. The arrhythmias treated were AV nodal reentrant tachycardias (n=1116), paraseptal and superoparaseptal accessory pathways (n=100), and focal atrial tachycardias (n=87). In 158 (12%) procedures, cryomapping (38 cases) or cryoablation (120 cases) were stopped due to transient AV block (first-degree AV block 74 cases, second-degree AV block 67 cases, and third-degree AV block 17 cases) after which another site was tested. Transient AV block occurred within seconds of mapping up to 3 min of ablation. The incidence of AV block was similar for different substrates. In most cases, AV nodal conduction was restored within seconds but in two cases transient AV block lasted 21 and 45 min, respectively. There were no cases of acute permanent AV blocks. No late AV blocks occurred during follow-up (mean 24 months, range 6-96 months). CONCLUSION Cryoablation adjacent to the AV node carries a negligible risk of permanent AV block. Transient AV block during ablation is a benign finding.

Cryoablation of superoparaseptal and septal accessory pathways: a single centre experience

AIMS Radiofrequency (RF) catheter ablation in the septum close to the atrioventricular (AV) node or His bundle has an increased risk of irreversible complications. Cryothermal energy has the advantages of reversible cryomapping and increased catheter stability. This study evaluates the usefulness of cryoablation in superoparaseptal and septal accessory pathways (APs). METHODS AND RESULTS Twenty-seven consecutive patients (16 men, 11 women, median age 29 years, range 15-65) underwent cryoablation for APs either located in the superoparaseptal (n=18) or septal (n=9) area. Cryomapping, using exclusively a 6 mm tip catheter, at -30 degrees C was performed before ablation with a goal temperature of -80 degrees C for 240 s. Acute success was achieved in 26 out of 27 patients (96%). Total procedure and fluoroscopy time was 163+/-61 and 30+/-22 min, respectively. During a follow-up for a mean of 996+/-511 days, seven patients (27%) had recurrences of arrhythmia. Five out of these seven underwent a second cryoablation with successful results, giving a total success rate of 89%. Two patients developed transient second degree AV block during cryoablation; however, no permanent AV block was observed. The recurrence rate was significantly higher in patients with procedure-related transient mechanical AP block (6/7; 86%) due to catheter trauma compared with those without mechanical block (5/20; 25%; P=0.006). CONCLUSION Cryoablation of the superoparaseptal and septal APs is a safe and effective alternative to RF therapy. Procedure-related transient mechanical AP block predicts worse late outcome.

Electrophysiologic effects of mental stress in healthy subjects: a comparison with epinephrine infusion.

Mental stress has been associated with serious cardiac arrhythmias, including ventricular tachycardia and ventricular fibrillation. The purpose of this study was to assess cardiac electrophysiologic effects of mental stress and compare them with those of epinephrine infusion. Ten healthy male volunteers participated. Electrophysiologic and hemodynamic variables were measured at baseline, during mental stress produced by Stroops color word conflict test and during epinephrine infusion at 2 rates (0.025 micromol/kg/min and 0.3 micromol/kg/min). Mental stress produced significant effects on the electrophysiologic properties of the heart with shortening of all measured electrophysiologic variables except atrial, most markedly those of the sinus and the atrioventricular nodes. The effects on the right ventricular myocardium and the His-Purkinje conduction system were less pronounced. During infusion of epinephrine, corresponding effects could only be reproduced at a much higher plasma level. Circulating epinephrine apparently plays a minor role as a mediator of mental stress effects on the heart.

Safety and efficacy of cryoablation of atrial tachycardia with high risk of ablation-related injuries

AIMS The purpose of this study was to evaluate the safety and efficacy of cryoablation as an alternative to radio frequency (RF) ablation in high-risk-located atrial tachycardia (AT). METHODS AND RESULTS Between 2004 and 2007, 164 patients underwent catheter ablation due to AT at our institution. Twenty-six of these patients (22 women and 4 men), median age 58 years (range 14-76), were considered having high-risk-located AT and were treated by cryoablation. Seven patients had failed prior RF ablation due to high risk of complications. The AT foci distribution was: close to the AV node (n = 14), vicinity of the sinus node (n = 7), and crista terminalis adjacent to the phrenic nerve (n = 5). Cryomapping, using a 6 mm tip catheter, at -30 degrees C was performed before ablation with a goal temperature of -80 degrees C for 240 s. Acute success rate was achieved in 25/26 patients (96%). During a follow-up of 493 +/- 258 days, three patients had recurrences. Two of these underwent a second successful cryoablation procedure. Long-term success rate was 92%. Phrenic nerve palsy occurred in two patients with complete recovery after 1 day and 5 months, respectively. CONCLUSION Cryoablation of high-risk-located AT foci is a safe and effective alternative to RF therapy.

Selective Ik blocker almokalant exhibits class III--specific effects on the repolarization and refractoriness of the human heart: a study of healthy volunteers using right ventricular monophasic action potential recordings.

Almokalant, a recently developed potassium-channel blocker, has exhibited properties of a selective class III agent in vitro and in animal experiments. We report the first invasive study in humans in which the electrophysiological characteristics of almokalant were assessed. Thirty-four healthy males received bolus and maintenance infusions of almokalant to two of our target plasma concentrations of 20, 50, 100, and 150 nM. Electrophysiological variables were assessed during stimulation at 100 and 120 beats/min at baseline and at two consecutive targeted levels. Almokalant dose-dependently increased the duration of the monophasic action potential (MAP) above a mean plasma concentration of 60 nM. The duration at 90% repolarization significantly increased by 20% from baseline at 100 beats/min (p < 0.00005), and by 19% at 120 beats/min (p < 0.00005), at a mean plasma concentration of 116 nM. During atrial stimulation, there was a significant increase in the QT interval, amounting to 24% at 100 beats/min (p < 0.00005) and to 30% at 120 beats/min (p = 0.0006), at 124 nM. During right ventricular stimulation in the apical region, the QT interval significantly increased by 17% at 100 beats/min (p < 0.00005), and 13% at 120 beats/min (p < 0.00005). During stimulation from the right ventricular outflow tract, the QT interval increased to a lesser extent and significantly only at 120 beats/min: 9% at 100 beats/min (p = NS) and 6% at 120 beats/min (p = 0.001) at 118 nM. The effective refractory period (ERP) of the atria increased by 18% at 100 beats/min at 119 nM (p = 0.005). The right ventricular ERP increased by 16% at both heart rates (HR) (p < 0.00005) during stimulation from the apical region, and by 11% during stimulation from the outflow tract (p = 0.0001 at 100 beats/min and p = 0.0006 at 120 beats/min). There was no effect on the ERP of the atrioventricular node, (AVN) on the sinus node function or cardiac conduction. Two individuals experienced a transient metallic taste during bolus infusion aiming at 50 and 100 nM, but this side effect did not occur in the group receiving the highest doses. Pronounced T-wave/U-wave (TU) morphology changes were observed in 4 individuals. Almokalant exhibited characteristics of a pure class III agent with no effects on cardiac conduction or sinus node function when given intravenously. Although no proarrhythmias were observed, the development of TU morphology changes and increased spatial dispersion of repolarization after the highest doses warrants further studies regarding the safety profile of the drug.

An active supply of analgesics during pulmonary vein isolation reduces pain

Abstract Aim. Pulmonary vein isolation (PVI) is an established method for treatment of drug refractory atrial fibrillation. The aim of this study was to evaluate whether a more active regular supply of analgesic and sedative drugs reduces pain and discomfort. We also wanted to evaluate gender differences in pain perception and to compare standard radiofrequency (RF) with cryo balloon ablation (Cryo) from this perspective. Methods. A total of 80 patients, 40 men, median age 58 (range 23–76) years, who underwent PVI under conscious sedation were studied. They were randomized to either standard treatment with morphine and diazepam (control group, C) or to a more active analgesic strategy (A) with pre-medication with oral midazolam mixture and intravenous alfentanil and midazolam regularly administrated during the procedure. Forty patients were treated with RF and 40 with Cryo. Results. The majority of the patients experienced pain during the procedure. The maximal pain assessed with numerical rating scale (NRS), was lower in the active group compared with that in controls (p = 0.02). Women experienced more pain than men (p = 0.01). RF was more painful than Cryo (p < 0.001). Conclusion. An active regular supply of analgesic and sedative drugs reduce pain and discomfort during PVI. Women experience more pain than men during this procedure and PVI performed with Cryo is less painful than with RF.

Surgery for ventricular tachycardia in patients undergoing surgical ventricular restoration: The Karolinska approach

This article presents a review on the efficacy of surgical ventricular restoration and direct surgery for ventricular tachycardia in patients with left ventricular aneurysm or dilated ischemic cardiomyopathy. The procedure includes a non-electrophysiologically guided subtotal endocardiectomy and cryoablation in addition to endoventricular patch plasty of the left ventricle. Coronary artery bypass surgery and mitral valve repair are performed concomitantly as needed. In our experience, this procedure yielded a 90% success rate in terms of freedom from spontaneous ventricular tachycardia, with an early mortality rate of 3.8%. A practical guide to the pre- and postoperative management of these patients is provided.