Direct thermography-a new in vitro method to characterize temperature kinetics of ablation catheters.

PURPOSE: For the treatment of increasingly complex cardiac arrhythmias, new catheter designs as well as alternative energy sources are constantly being developed. However, there is presently no in vitro method available for assessment of the temperature changes induced at various myocardial levels during energy delivery. Therefore, our study was aimed at developing an in vitro model to record and display the temperature kinetics during ablation in the entire muscle cross section. METHODS AND RESULTS: A sapphire glass pane was inserted into one wall of the in vitro experimental set-up. Due to its thermodynamic properties, the temperature distribution in an adjacent cross section of the cardiac muscle can be measured exactly ( 1 °C) through this pane by means of a thermography camera. Computer-supported image processing enables the colour-coded and two-dimensional display of the temperature kinetics during the energy application at any location of the myocardial cross section (± 0.5 mm). This new measuring methodology was validated by direct temperature measurements utilizing several intramyocardial thermo elements. CONCLUSION: This new method allows a temporal and spatial analysis of the temperature phenomena during ablation without the interference and spatial limitation of intramyocardial temperature probes. New ablation technologies can thus be evaluated, independent of the catheter configuration or source of energy used.

[Invasive electrophysiology: complications, nightmares and their management]. / Invasive Elektrophysiologie: Komplikationen, Alpträume und deren Management--Rechtskardiale Katheterablationen.

Most minor side effects of ablation in the right atrium and right ventricle relate to femoral venous catheterization but there is a small risk of severe complications including atrioventricular (AV) block, damage of surrounding structures and thromboembolic events. Impairment of AV conduction can occur during ablation of atrioventricular re-entrant tachycardia, ablation of anteroseptal, mid-septal and parahisian accessory pathways, ablation of ectopic atrial tachycardia originating from the vicinity of the atrioventricular node and when ablating the septal isthmus for typical atrial flutter. Damage of the right coronary artery is a very rare complication after inferior isthmus ablation with high energy. The thromboembolic risk during and after cardioversion and ablation of atrial flutter is higher than previously recognized and anticoagulation therapy decreases this risk. The risk of perforation and tamponade during ablation in the right atrium and right ventricle is very low but particular caution is necessary in thin-walled structures such as the coronary sinus and the upper right ventricular outflow tract. Phrenic nerve injury can be avoided by pacing from the mapping electrode before application of radiofrequency energy at the right atrial free wall. Limitation of power output depending on the site of ablation and titration of energy application with continuous control of temperature and impedance should be considered to minimize the risk of complications.

[Analysis of the cause of death of ICD patients during long-term follow-up]. / Analyse der Todesursachen von ICD-Patienten in der Langzeitbeobachtung.

BACKGROUND: Implantable cardioverter defibrillators represent an effective therapy to prevent sudden cardiac death in patients with ventricular arrhythmias. This implies a change in the spectrum of causes of death. There exist no large studies providing an exact differentiation of these causes of death. METHODS: During a mean observation period of 41+/-29 months (3 d-12 yrs), we analyzed the outcome of 429 ICD patients (CAD n=274, dilative CMP n=97, others n=23, no structural heart disease n=35), mean age 62+/-12 years (23-87 yrs). RESULTS: The overall survival rate was 79.7% whereby 3.5% of these patients underwent successful heart transplantation and 2.1% died suddenly. 60.9% of all deaths showed a non-sudden cardiac cause (heart failure 56.3%, myocardial infarction 4.6%). In 28.7% a non-cardiac fatal event was present (cancer 11.5%, septicemia 6.9%, stroke 4.6%). The deceased showed significantly more often structural heart disease (100 vs 92%, p<0.02) and a lower left ventricular ejection fraction (37+/-14 vs 44+/-18%, p<0.02). Significant higher survival rates were associated with medication with beta blockers (88 vs 75%, p<0.02) and the class III antiarrhythmic agents sotalol und amiodarone (85 vs 77%, p<0.03). CONCLUSIONS: Mortality due to sudden death was reduced to 2.1% in ICD patients associated with a shift of causes of death towards severe heart failure. Therefore, special attention should be paid to the signs of heart failure in these patients to enable early initiation of appropriate therapeutic strategies.

[Surgical and interventional use of radiofrequency current: is there interference with implantable cardioverter/defibrillators?]. / Operativer und interventioneller Einsatz von Radiofrequenzstrom: gibt es Interferenzen mit implantierbaren Cardioverter/Defibrillatoren?

BACKGROUND: During surgical and interventional procedures, interactions between implantable cardioverter defibrillators (ICD) and electrical cautery, respectively, application of radiofrequency (RF) energy may occur. Induction of inadequate shock therapies or device malfunction may result and represent a potential perioperative hazard for the patient. METHODS: Hence, we analyzed the intraoperative interactions in 23 consecutive ICD patients with regard to different surgical and interventional procedures. Sixteen surgical operations (general surgery n = 7, urologic n = 5, abdominal n = 2, gynecological n = 1, thoracic n = 1) and 7 interventional therapies (RF catheter ablation n = 5, endoscopic papillotomy n = 2) were performed. The ICD devices were all located in the left pectoral position and consisted of 15 single and 8 dual chamber defibrillators. During the procedure tachyarrhythmia detection (VF 295 +/- 21 ms, VT 370 +/- 55 ms) of the devices was maintained active (monitoring mode); only ICD therapies were inactivated. The indifferent electrode of the electrical cauter/RF generator was placed in standard positions (right mid femoral position n = 18, thoracic spine area n = 5). After the procedure, the ICD memory was checked for detections, respectively, for changes of the programming. RESULT: There was no misdetection or reprogramming of the ICD caused by electrical cautery or RF energy. CONCLUSIONS: Despite the lack of undesired interactions ICDs should be inactivated preoperatively to assure maximum patient safety. However, should inactivation be ineffective or not manageable, electromagnetic interference is highly unlikely.

[Long-term efficacy of antitachycardia pacing for treatment of ventricular tachycardia in patients with implantable cardioverter/defibrillator]. / Effizienz der antitachykarden Stimulation bei Patienten mit implantierbarem Cardioverter/Defibrillator und monomorphen ventrikulären Tachykardien im Langzeitverlauf - Gibt es Prädiktoren für eine erfolgreiche Uberstimulation?

UNLABELLED: Antitachycardia pacing techniques (ATP) have proved useful for termination of ventricular tachycardia (VT). However, little is known about the efficacy and safety off ATP during long-term follow-up in a larger study population. We analyzed the data of 80 ICD patients (pts) with spontaneous monormorphic VT, mean age 59 +/- 12 years, the mean follow-up was 26 +/- 17 months. 50 pts (62.5%) had coronary artery disease, 18 (22.5%) dilative cardiomyopathy (DCM), the remaining 12 pts (15%) had no or other cardiac diseases. 2926 episodes of ventricular tachycardia (cycle length 349 +/- 51 ms, 240-520 ms) occurred in 64/80 pts (80%), overall efficacy of ATP was 89.9%, acceleration occurred in 4.1% of VTs. Success of ATP did not correlate with positive ATP testing on induced arrhythmias, LVEF, NYHA class or aneurysm. Neither underlying heart disease nor antiarrhythmic medication had an impact on the ATP success rate. ATP efficacy was linked significantly to short VT cycle length (VTCL, 240-300 ms, p < 0.01) and long coupling intervals (91-97%), p < 0. 01). Acceleration occurred in 32% of pts and in 4.1% of VT episodes; it was also dependent on short VT cycle length (< 300 ms vs > 300 ms, p < 0.04) and short coupling intervals (< 81% vs >/= 81%, p

The combined transvenous implantation of cardioverter defibrillators and permanent pacemakers.

We developed criteria for implantation and programming of permanent endocardial pacemakers in patients with a nonthoracotomy ICD system. These criteria were prospectively used in 10 patients who recieved an ICD prior to (n = 5) or following (n = 5) implantation of a dual chamber (n = 6) or ventricular (n = 4) pacemaker with a unipolar (n = 4) or bipolar (n = 6) lead configuration. All patients were tested for interactions or malfunctions. Undersensing of ventricular fibrillation by the atrial sense amplifier and inadequate atrial pacing occurred in one patient with a unipolar dual chamber system programmed to AAIR but didn't impair ICD sensing. Transient or permanent loss of capture or sensing of the pacemaker was not observed after ICD shocks with the output programmed to double pulse width and voltage of stimulation threshold and the sensitivity to 50% of the detected R wave. One episode of transient reprogramming occurred without clinical consequences. One unipolar ventricular pacemaker lead had to be exchanged against a bipolar lead because of oversensing of the pacing artifact by the ICD. There was no failure of an ICD to detect ventricular arrhythmias due to inadequate pacemaker activity. During a follow-up period of 21 +/- 11 months, a total of 78 ventricular arrhythmias were effectively treated in six patients. Thus, a combined use of transvenous ICD and pacemaker is possible despite the close vicinity of pacing and defibrillations leads. Optimized programming different to the common settings is required. As interactions occurred only in unipolar pacemaker leads bipolar systems should be used in these patients.

[Stored electrograms to differenciate between adequate and inadequate ICD therapy]. / Bedeutung der Speicherelektrogramme zur Differenzierung adäquater und inadäquater ICD-Therapien.

The introduction of implantable cardioverter defibrillators in 1980 by Mirowski et al, offered a new therapeutic device for the treatment of ventrikular tachyarrhythmias. In the beginning it was only possible to evaluate arrhythmic events by analysis of the therapy-counter in combination with clinical symptoms. Even rapid ventricular tachyarrhythmias may not produce significant symptoms prior to ICD shock in more than 50% of patients. On the other hand the ICD device will initiate inappropriate therapy due to sensing error and non sustained tachyarrhythmias in 20-40% of patients. Third generation ICD devices provide sophisticated diagnostic information by stored electrograms. Intracardiac electrograms are recorded by the bipolar tip electrode of the sensing lead, located in the right ventricel (near field) or by the electrodes used for energy delivery (far field). These ECG recordings provide valuable information to evaluate the type of arrhythmia, trigger mechanisms and therapeutic efficacy. The arrhythmia leading to device therapy is judged by cycle length and stability and morphology of the intracardiac signal. A correct arrhythmia classification using electrogram analysis is possible in 92-98% of arrhythmias. Evaluation is limited in 5-10% of patients with bundle branch block or aberand conduction. Inappropriate ICD therapy is caused by atrial fibrillation in more than 50% and by supraventricular tachycardia or sinus tachycardia in about 20%. Sensing of artefacts can be attributed to lead failure in about 17%. The distinction between appropriate and inappropriate therapeutic intervention by the ICD allows the prevention of unnecessary shock delivery and early diagnosis of lead failure. The development of dual chamber systems with enhanced storage capacity and improved algorithms for detection of arrhythmias may further decrease the incidence of inappropriate ICD therapies.

Comparison of a unipolar defibrillation system with a dual lead system using an enlarged defibrillation anode.

The unipolar system for transvenous defibrillation, consisting of a single right ventricular lead as the cathode and the device shell as anode, has been shown to combine low defibrillation thresholds (DFTs) and simple implantation techniques. We compared the defibrillation efficacy of this system with the defibrillation efficacy of a dual lead system with a 12-cm long defibrillation anode placed in the left subclavian vein. The data of 38 consecutive patients were retrospectively analyzed. The implantation of an active can system was attempted in 20 patients (group 1), and of the dual lead system in 18 patients (group 2). Both groups had comparable demographic data, cardiac disease, ventricular function, or clinical arrhythmia. The criterion for successful implantation was a DFT of < or = 24 J. This criterion was met in all 18 patients of group 2. The active can system could not be inserted in 3 of the 20 group 1 patients because of a DFT > 24 J. In these patients, the implantation of one (n = 2) or two (n = 1) additional transvenous leads was necessary to achieve a DFT < or = 24 J. The DFTs of the 17 successfully implanted group 1 patients were not significantly different from the 18 patients in group 2 (12.3 +/- 5.7 J vs 10.8 +/- 4.8 J). The defibrillation impedance was similar in both groups (50.1 +/- 6.1 omega vs 48.9 +/- 5.2 omega). In group 1, both operation duration (66.8 +/- 17 min vs 80.8 +/- 11 min; P < 0.05) and fluoroscopy time (3.3 +/- 2.1 min vs 5.7 +/- 2.9 min; P < 0.05) were significantly shorter. Thus, the active can system allows reliable transvenous defibrillation and a marked reduction of operation duration and fluoroscopy time. The dual lead system, with an increased surface area defibrillation anode, seems to be a promising alternative for active can failures.