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Aims: This report describes the initial clinical results with a newly designed guiding catheter and an 'over the wire' pacing lead based on angiolasty technology to stimulate the left ventricle using the transvenous route via the coronary sinus (OTW-CV lead)., Methods and Results: In 75% of the 15 patients (6 males, 9 females, mean age of 53 +/- 9 years) with congestive heart failure, access to coronary sinus required less than 2 min; in one patient. the attempt failed. Mean R wave amplitudes plus or minus the standard deviation, measured at apical, mid-ventricular and basal positions the anterior (11.4 +/- 9.2, 10.8 +/- 6.2, 9.3 +/- 6.3 mV) and lateral or posterior veins (10.1 +/- 10.7, 8.6 +/- 6.4, 7.7 +/- 4.3 mV) showed a trend favouring the apex without statistical significance. Pacing impedance, measured at the same sites and vein tributaries, ranged from 670 +/- 191 to 915 +/- 145 ohms. Pacing thresholds measured at apical and mid ventricular sites were significantly lower than at the base in the anterior vein 2.5 +/- 2.8 and 2.8 +/- 1.8 vs 5.6 +/- 2.7 V at 0.5 ms, P<0.001). Thresholds in the lateral/posterior veins showed a similar trend but did not reach statistical significance (3.0 +/- 1.7, 3.6 +/- 1.4 +/- 1.8 V at 0.5 ms). In patients, in whom thresholds were determined in more than one vein, the 'best' mean threshold was 1.6 +/- 0.7 V., Conclusion: The new 'over the wire' lead and guiding catheter system allows uncomplicated access to the coronary sinus and the depth of the coronary vein tributaries. Left ventricular sensing and pacing thresholds are acceptable for chronic use in implanted cardiac rhythm management systems.

Sensing of the intracardiac evoked response (ER) after a pacing stimulus has been used in implantable pacemakers for automatic verification of capture. Reliable detection of ER is hampered by large residual afterpotentials associated with pacing stimuli. This led to the development of various technological solutions, like the use of triphasic pacing pulses and low polarizing electrode systems. This study investigated the effect of reducing the coupling capacitance (CC) in the pacemaker output circuitry on the magnitude of afterpotential, and the ability to automate detection of ventricular evoked response. A CC of 2.2 microF and four different blanking and recharge time settings were clinically tested to evaluate its impact on sensing of the ventricular ER and pacing threshold. Using an automatic step-down threshold algorithm, 54 consecutive patients, aged 70 +/- 10 years with acutely (n = 27) or chronically (n = 27) implanted ventricular pacing leads were enrolled for measurement testing. Routine measurements, using a standard pacing system analyzer (PSA), were (mean +/- SD) impedance 569 +/- 155 omega, R wave amplitude baseline to peak 9.8 +/- 3.7 mV and threshold 0.9 +/- 0.7 V at 0.4-ms pulse width. This new capture verification scheme, based on a CC of 2.2 microF and recharge/blanking timing setting of 10/12 ms, was successful in 52 patients which is equivalent to a success rate of 96%. In a subgroup of 26 patients implanted with bipolar ventricular leads (10 chronic, 16 acute), data were collected in unipolar (UP) and bipolar (BP) pace/sense configurations. Also, ER signals were recorded with two different band-pass filters: a wider band (WB) of 6-250 Hz and a conventional narrow band (NB) of 20-100 Hz. WB sensing from UP lead configuration yielded statistically significant larger signal to artifact ratios (SAR) than the other settings (P < 0.01). A dedicated unipolar ER sensing configuration using a small output capacitor and a wider band-pass filter enables adequate automatic capture verification, without any restrictions on pacing lead models or pacing/sensing configurations.

Aims: The aim of the study was to compare the defibrillation energy requirements and the probability of successful defibrillation at multiples of the minimum defibrillation energy requirements in active pectoral implantable defibrillators with single- and dual-coil lead systems., Methods and Results: Eighty-three consecutive patients undergoing implantation of an active pectoral cardioverter-defibrillator were randomized to receive a dual- or single-coil lead system. Defibrillators of two manufacturers with a fixed tilt biphasic defibrillation waveform were used. Defibrillation energy requirements were determined using a step-down defibrillation testing protocol. According to the randomization protocol, the patients were assigned to three additional consecutive defibrillation attempts during device implantation and during pre-discharge testing of either 1.0, 1.5 or 2.0 times the determined defibrillation energy requirement. Patients presenting defibrillation energy requirements > 15 J were excluded from analysis. Eighty of 83 patients (96%) completed the study protocol. Three patients were excluded due to elevated defibrillation energy requirements. The defibrillation energy requirements in the dual- and single-coil patient groups were 8.0 +/- 3.6 J and 8.4 +/- 3.7 J (ns), respectively. A comparable percentage of study patients showed defibrillation energy requirements <10 J (dual-coil: 88% vs single-coil: 83%). Defibrillation impedance was significantly different (dual-coil: 50 +/- 5.8 Ohm; single-coil: 39.8 +/- 4.2 Ohm). Regarding the probabilities of successful defibrillation, there were no significant differences between the two patient groups. The probabilities of defibrillation at the three multiples of the defibrillation energy requirement using a dual- and single-coil lead system were 82, 89.7 and 93.6 and 77.8, 94.1 and 95.8%, respectively (P=0.88, P=0.42, P=0.62, respectively)., Conclusions: Dual- and single-coil active pectoral defibrillator systems show no difference in defibrillation energy requirements and no difference in the probability of successful defibrillation at multiples of the minimum defibrillation energy requirement. The use of more simplified defibrillator lead systems may contribute to a future lead design focusing on improvement in lead durability.

Aims: Thermal injury of subendocardial tissue leads to a release of electrolytes and free radicals from the intracellular site creating a change in electrochemical potential (eP) between the distal and the proximal catheter tip electrodes. The aim of the study was to verify the detection of ablation-induced release of electrolytes and free radicals and to assess the suitability of control-line energy delivery at ablation by measuring eP., Methods and Results: In vitro tests under constant flow conditions were performed in a 101 bath of physiological saline solution or bovine blood. Endomyocardial preparations of fresh bovine hearts were used. Closed-loop temperature-controlled, irrigated and closed-loop eP-controlled ablations were performed. In vivo animal investigations were performed in six anaesthetized and ventilated pigs. The existence of the eP was established in the tank model and was confirmed in animal investigations. High correlations were found between eP and catheter tip temperature (r=0.87) and between maximum eP and induced lesion size (r=0.85). Also a high correlation (r=0.85, P<0.001) was found between eP and lesion volume., Conclusions: Control of energy delivery during RF ablation by the measurement of eP is feasible. In comparison with temperature controlled RF ablation, ablation guided by eP-measurement revealed a superior correlation with induced lesion size. Especially during cooled radiofrequency catheter ablation eP is the only parameter for control of energy delivery.

The aim of study was to investigate the extent of myocardial injury incurred by creation of continuous RF current induced linear ablation lesions (LL; ablation of atrial fibrillation, right atrial procedure) in comparison to focal RF lesions (FL; AV node reentry tachycardia, WPW tachycardia). In 23 patients with LL (age 51.3 +/- 11.2 years, 18 men, 5 women) and in 16 patients with FL (age 53.9 +/- 5.1 years, 8 men and 8 women), levels of creatine kinase (CK), myoglobin (MG), CKMB mass (CKMB M), CKMB activity (CKMB A), and cardiac troponin T (cTnT) were determined before and 2, 4, 8, 24, and 48 hours after ablation. CKMB A was normal in 87% in LL and 100% in FL (< 6% of CK) with median maximum CK values of 214 (45-1583) U/L in LL and 36 (29-212) U/L in FL. Peak values of all parameters were significantly higher in LL than in FL. The sensitivity of cTnT was 50% in FL and 100% in LL. In FL MG, total CK, and CKMB M were abnormal in only 12.5% of cases while in LL MG and CKMB M were pathological in 100% and total CK was abnormal in 91.3% of patients. The amount of energy and number of RF applications correlated with cTnT, MG, and CKMB M (P = 0.01). In conclusion, (1) long linear RF current lesions for ablation of atrial fibrillation are associated with significantly greater myocardial injury than focal ablations. (2) In focal lesions only cTnT provided a sensitivity of 50% in the detection of myocardial injury while in linear lesions cTnT, CKMBM, and CKMB M seemed suitable for detection of RF current induced myocardial damage with 100% sensitivity. All biochemical parameters do not differentiate patients with coronary ischemia up to 48 hours after an ablation. (3) Further investigations are necessary to determine if RF current linear lesions lead to impaired atrial contractility in cases of extensive tissue damage.

A patient with recurrent syncope due to polymorphic ventricular tachycardia was diagnosed with Brugada syndrome. Programmed right ventricular stimulation could not induce arrhythmia. Epicardial stimulation from a left ventricular site through the coronary sinus led to polymorphic VT. The stimulation protocol for risk stratification in Brugada syndrome is discussed.

Background: For invasive treatment of atrial fibrillation, linear lesions induced with multipolar ablation catheters (MAC) are needed to prevent recurrence. The aim of the study was to compare the efficacy of pulsed versus continuous radiofrequency (RF)-energy delivery using MAC., Methods: In vitro tests were performed using endomyocardial preparations of fresh pig hearts in a 10-liter-bath of physiologic saline solution (37 degrees C) at constant flow conditions (1.5 l/min). The MAC were placed with a constant pressure of 20 ponds onto the endocardium. The energy (generator: Osypka HAT 200 S) was delivered either pulsed (4 electrodes simultaneously, 5ms duty-cycle) or continuously (each electrode separately). In vivo experiments were performed in 6 anesthetized pigs using fluoroscopic positioning of MAC at 40 different intracardial positions and with similar conditions as in vitro experiments. Lesion volume (LV) was calculated after measuring lesion diameter with a microcaliper. The homogeneity of the lesions (LH) was classified from 1-4; with 1 as highest homogeneity., Results: Pulsed energy delivery produced more homogeneous linear lesions in significantly less time. There was no difference in electrode temperature values (50.2 +/- 0.8 and 51.3 +/- 1.4 degrees C) in vitro and in vivo. In the in vivo experiments, lesion depth and calculated lesion volume were less in both modes of energy delivery but pulsed energy delivery was superior regarding lesion depth and homogeneity., Conclusion: With pulsed energy delivery it is possible to create linear lesions of significantly greater homogeneity. Moreover, larger lesions are induced in less time by pulsed energy delivery in vitro and in vivo.

The automated measurement of the main electrical parameters of pacemakers, such as battery voltage, current drain, pacing impedance, sensing levels, and pacing thresholds enables a continuous monitoring of the adequate functioning of the implanted device. New technologies in device interrogation, data transfer, and patient alert functions will enhance therapy safety significantly by the immediate detection of all, including transient, device malfunctions. The introduction of this technology will result in major changes in follow-up of patients with pacemakers. Technically we are very close to the goal of a fully automated pacemaker, although clinical acceptance lags behind. Clinical studies are necessary to demonstrate the beneficial effects of automated device functions, with regard to the main rationales for pacemaker automatization: increased patient safety, improved quality of life, and an improvement in the cost-benefit ratio in pacemaker therapy.

The aim of this study was to compare the efficacy of pulsed versus continuous RF energy delivery via multipolar ablation catheters. In vitro tests were performed in endomyocardial preparations of fresh bovine hearts in a both of physiological saline solution (37 degrees C) at constant flow conditions (1.5 L/min). The catheters were applied to the endocardium at a constant pressure. Energy was delivered pulsed (to 4 electrodes simultaneously, 5-ms duty cycle) or continuously (to each electrode separately). In vivo experiments were performed under fluoroscopy in eight anesthetized pigs, guided by endocardial electrograms to place the catheters in 22 different intraatrial positions. Lesion volume was calculated from measurements of the lesion diameter with a microcaliper. The homogeneity of the lesions was classified from 1 (highest) to 4 (least). More homogeneous linear lesions were produced in significantly less time with pulsed than with continuous energy delivery. There were no differences in electrode temperature or impedance values in vitro and in vivo. The results in the in vitro experiments were reproducible in the intact animal experiments. Significantly larger and more homogeneous linear lesions were created more rapidly with pulsed than with continuous energy delivery.

Background: In about a third of cases of recurrent syncope a diagnosis cannot be established despite extensive cardiovascular and neurologic testing. In patients without underlying heart disease the sensitivity of conventional diagnostic testing is low., Case Report: A 33-year-old male patient underwent implantation of a loop recorder (Reveal) after negative neurological and cardiovascular testing. One month after implantation sinus node arrest could be documented during a presyncope. The patient underwent pacemaker implantation and remains asymptomatic since then., Conclusion: In patients with syncope and a negative conventional diagnostic workup the implantable loop recorder is a helpful and cost-effective diagnostic tool.

History: Some weeks previously a 34-year old athlete, specializing in the triathlon, had 6 syncopes in one day. They had caused abrasions and contusions resulting from the falls. At another hospital paroxysmal atrial fibrillation had been diagnosed and treatment with disopyramide (2 x 200 mg) initiated, but she had about 15 further syncopes within 2 weeks. She was admitted for establishing their cause., Investigations: Initial ECGs and neurological examination failed to provide a diagnosis and she was discharged with an "event recorder"., Diagnosis, Treatment and Course: Three weeks after discharge she had another syncope. The event recorder was activated by the patient's partner and revealed polymorphous ventricular tachycardia. She underwent extensive invasive cardiological tests, including a right ventricular biopsy, but no abnormality was demonstrated. However, a provocation test with ajmaline produced ST segment elevations in V1 and V2 typical of the syndrome previously described by the Brugadas (right bundle branch block, precordial ST elevations in V1-V3 and sudden cardiac death). A cardioverter-defibrillator was implanted. During the subsequent observation period of 2 month the ICD delivered one countershock, triggered by the onset of polymorphous ventricular tachycardia with syncope., Conclusion: In patients with serious ventricular arrhythmias but no diagnostic findings, including a normal resting ECG, a drug provocation test should be performed to exclude a Brugada syndrome.

In the current clinical cardiac electrophysiology well-defined and effective concepts regarding the diagnostic and treatment of cardiac arrhythmias have been introduced. A further improvement in the cost-benefit and the cost-effectiveness relationships in several fields of cardiac electrophysiology depends on the future technical progress and on the results of ongoing and future scientific studies. On the other side very cost-saving electrophysiological treatments had been developed; the broader clinical use of these treatments is a possibility to optimize the costs for patients' care with cardiac arrhythmias.

Unlabelled: A recently developed algorithm that is based on symbolic dynamics and computation of the normalized algorithmic complexity (C(alpha)) was applied to basket-catheter mapping of the atrial fibrillation (AF). The aim of our study was to analyze the spatial distribution of the C(alpha) during AF and effects of propafenone on this distribution. During right atrial mapping in 25 patients with AF 31 intra-atrial and 1 surface bipolar channels were acquired. The anatomical location of the intra-atrial electrodes was defined fluoroscopically. C(alpha) was calculated for a moving window (size: 2000 points; step 500 points). Generated C(alpha) was analyzed within 10 minutes before and after administration of propafenone. The inter-regional C(alpha) distribution was analyzed using the Friedman-test (intra-individually) and Kruskall-Wallis-H-test (inter- individually). A value of p=0.05 was set for an error probability. Inter-regional C(alpha) differences were found in all patients (p<0.001). The right atrium could be divided in high- and low complexity areas according to individual patterns. A significant C(alpha) increase in cranio-caudal direction (with the exception of septum) was confirmed inter-individually (p<0.01). The administration of propafenone enlarged the areas of low complexity., Conclusions: This new method utilizing the combination of symbolic dynamics and adaptive power estimation can provide complex evaluation of the dynamics of AF in man. High-density mapping will be required for further evaluation of results.

Aims: In newer implantable cardioverter-defibrillators with automatic gain control amplifiers the maximum possible sensitivity is programmed with the aim of securing optimal detection of ventricular fibrillation. This study was designed to prove that a reduction in maximum sensitivity is safe with respect to appropriate sensing of ventricular fibrillation, while avoiding sensing of extracardiac signals., Methods and Results: Forty-two consecutive patients, undergoing defibrillator implantation/replacement with programmable maximum auto-gain sensing sensitivity (Ventak Mini III, Ventak AV , Guidant, St. Paul, MN, U.S.A.), were prospectively investigated. Thirty-four patients were implanted with a dual-coil lead system, providing integrated bipolar sensing (Endotak, Guidant, St. Paul, MN, U.S.A.), eight patients received a single-coil lead system with true bipolar sensing (Sprint, Medtronic, Minneapolis, MN, U.S.A.). During device implantation and pre-discharge testing, arrhythmia detection times of induced ventricular fibrillation were compared at programmed maximum (0.18 mV) and minimum (0.43 mV) sensitivity in a randomized manner. Seventy-six induced episodes of ventricular fibrillation were analysed. The mean arrhythmia detection times did not differ between the programmed sensing levels (maximum sensitivity: 1612 +/- 307 ms, vs minimal sensitivity: 1,602 +/- 330 ms; P = ns). The results were not affected by the type of implanted lead system (integrated bipolar versus true bipolar sensing)., Conclusion: In the implantable defibrillator devices, reduction in maximum sensitivity did not impair the detection of induced episodes of ventricular fibrillation.

AV nodal ablation with pacemaker implantation nor AV nodal modification is the therapy of the choice in patients with permanent or paroxysmal atrial tachyarrhythmias. Both methods of treatment are limited to patients with drug refractory atrial tachyarrhythmias. Therapy indication requires the complete knowledge of the current clinical status and medical history of the patient regarding the time course of the disease and the results of previous treatments. Both methods are effective and palliative treatments which may not modify the underlying arrhythmias. Neither treatment showed an improvement in patients prognosis; therefore a restrictive indication is mandatory.

The aim of this prospective and randomized study was to evaluate the safety and efficacy of a reduced shock strength in transvenous implantable defibrillator therapy. So far clinical data concerning the safety margin of the shock energy in ICD therapy do not exist. The shock energy tested during long-term follow-up in this study was twice the intraoperatively measured defibrillation threshold (DFT). A total number of 176 consecutive patients representing a typical cohort of ICD patients were evaluated. All patients received a non-thoracotomy lead system (CPI, Endotak 0070, 0090) and a biphasic cardioverter-defibrillator with the ability to store episodes (Cardiac Pacemakers Inc., Ventac TM PRx II, PRx III). The intraoperative defibrillation threshold (DFT) was evaluated in a step-down protocol (15, 10, 8, 5 J) and had to be < or = 15 J for inclusion into the study. The lowest effective energy terminating induced ventricular fibrillation had to be confirmed and was defined as DFT+ augmented defibrillation threshold. The DFT+ value was tested immediately after successful implantation, at discharge, and after a follow-up period of one year. Prior to implantation the patients were randomized into two groups. The energy of the first shock in the study group was programmed at twice DFT+ and in the control group at the maximum energy output (34 J). The efficacy of the first shock and its reproducibility in DFT testings and in spontaneous episodes during long-term follow-up of the study group were compared to those in the control group. A DFT+ value was found to be < or = 15 J in 166 of 176 patients (94%). The DFT+ in the study group was 9.6 +/- 3.2; in control group 10.1 +/- 3.5 J. The prohability of successful defibrillation at DFT+ level after one year was 84%. The success rate of the first shock meant to terminate induced ventricular fibrillation (VF) was 99.5% in the study group (217 of 218 episodes) and 99% in the control group (201 of 203 episodes). During follow-up of 24 +/- 9 months spontaneous episodes in the study group, 83/86 (96.5%) monomorphic ventricular tachycardias (MVT) and 38/40 (95%) VF-episodes were converted successfully by the 2x DFT+ shock. In the control group the first shock was successful in 151/156 (96.8%) spontaneous MVTs and in 30/33 (91%) VF episodes. The efficacy of the first shock was not influenced by clinical data such as the underlying cardiac disease, left ventricular function, ongoing antiarrhythmic therapy with amiodarone, or the number of spontaneous episodes per day or by the DFT itself. At a mean follow-up of two years there was no significant difference between the two groups concerning the incidence of sudden cardiac death (2.4% in the study group vs. 3.8% in the control group). In conclusion programming the first shock with the ICD lead system used in this study at 2x DFT+ is as efficient as a shock energy of 34 J in order to terminate induced and spontaneous episodes of VT/VF. Thus, the safety of ICD-therapy is not impaired when programming the shock energy at the 2x DFT+ value.

Unlabelled: Dual chamber ICD systems use two separate leads for sensing. We developed and tested a new prototype of a single pass dual chamber passive fixation lead for dual chamber ICDs., Methods and Results: The prototype was a modification of the Guidant CPI Endotak DSP lead. The additional sensing electrode for the right atrium consisted of a side-mounted porous atrial ring electrode (AR). Atrial signals were recorded from the lead in patients during normal sinus rhythm (NSR), atrial fibrillation (AFib), and/or atrial flutter (AFl) with the AR in stable contact with the atrial wall or floating. During NSR, with the AR in contact with the atrial wall, an average P wave amplitude of 7.2 +/- 1.5 mV (mean +/- SD, n = 12) was measured. After induction of Afib/AFl, the single amplitude decreased to 3.6 +/- 1.5 mV (n = 8) during AFib and 3.4 +/- 1.7 mV (n = 9) during AFl. Amplitudes dropped between 53% and 75% when the AR lost atrial wall contact. The atrial pacing threshold was 1.0 +/- 0.4 V (n = 16) when the AR was in contact with the atrial wall., Conclusions: In future dual chamber ICDs the signals from a passive fixation single pass lead could be used for atrial sensing and pacing as long as the sensing electrode for the right atrium remains in contact with the atrial wall. This system might lead to a simpler, less invasive implantation of dual chamber ICD systems.

Several lines of evidence have shown that viral infections are capable of causing coronary spasm and precipitating or mimicking clinical myocardial infarction. Here we report the case of a 41-year-old woman with recurrent angina who was admitted to our hospital because of ventricular tachycardia. Laboratory examination revealed positive IgM titers against Coxsackie B virus. Coronary angiography showed normal coronary arteries, but following a cold pressure test severe spasm of all coronaries with thrombotic occlusion of the second marginal branch of the circumflex artery occurred. We conclude that coronary spasm should be clinically suspected in patients with chest pain and ventricular arrhythmia in combination with IgM antibodies against Coxsackie B virus. In these patients, a cold pressure test should be avoided, and antithrombotic and antispastic therapy is recommended.

The aim of the present study was to assess the long-term reproducibility of the defibrillation efficacy of energies set at the intraoperatively measured defibrillation threshold using a modified testing protocol. Between December 1993 and January 1996, 83 patients receiving an implantable cardioverter-defibrillator (ICD) in combination with a non-thoracotomy lead system and having an intraoperatively measured defibrillation threshold (DFT) < or = 15 J were enrolled in a substudy of a prospective, randomized multicenter trial ("Low Energy Endotak Trial" (LEET)). Step-down DFT testing was performed intraoperatively (15, 10, 8, 5 J). It was mandatory to reproduce a successful conversion of ventricular fibrillation at the DFT energy during implantation (DFT+). At the end of implantation, at predischarge, and after one year, assessment of the defibrillation efficacy of DFT+ energy was repeated (first shock: DFT+, second shock: 2 x DFT+). Mean DFT+ at implant was 9.6 + 3.3 J. Immediately after implantation, successful conversion of induced ventricular fibrillation was achieved in 70/79 (89%) patients using DFT+ energies. In 7/8 (89%) patients only the second shock set at 2 x DFT+ and in one patient only the third shock set at maximum energy (34 J) was successful. At predischarge, defibrillation efficacy of DFT+ was reproducible in 61/77 (79%) patients. The remaining 16 patients were successfully converted using a second shock set at 2 x DFT+. One year after implantation, conversion of ventricular fibrillation was achieved at energies set at DFT+ in 52/62 (84%) patients and in the remaining 10 patients at energies set at 2 x DFT+. A total of 183/218 (84%) episodes of induced ventricular fibrillation were terminated successfully using DFT+ energies. There was no correlation between the intraoperatively determined DFT+ or the underlying cardiac disease and the defibrillation efficacy. These results demonstrate that the defibrillation efficacy for termination of induced ventricular fibrillation using DFT+ energies is reproducible at implantation, at predischarge, and one year after ICD insertion. Energies set at twice DFT+ seems to allow for reliable defibrillation within the first year after ICD implantation.

A new, thinner (10 Fr) and more flexible, single-pass transvenous endocardial ICD lead, Endotak DSP, was compared with a conventional lead, Endotak C, as a control in a prospective randomized multicenter study in combination with a nonactive can ICD. A total of 123 patients were enrolled, 55 of whom received a down-sized DSP lead. Lead-alone configuration was successfully implanted in 95% of the DSP patients vs 88% in the control group. The mean defibrillation threshold (DFT) was determined by means of a step-down protocol, and was identical in the two groups, 10.5 +/- 4.8 J in the DSP group versus 10.5 +/- 4.8 J in the control group. At implantation, the DSP mean pacing threshold was lower, 0.51 +/- 0.18 V versus 0.62 +/- 0.35 V (p < 0.05) in the control group, and the mean pacing impedance higher, 594 +/- 110 omega vs 523 +/- 135 omega (p < 0.05). During the follow-up period, the statistically significant difference in thresholds disappeared, while the difference in impedance remained. Tachyarrhythmia treatment by shock or antitachycardia pacing (ATP) was delivered in 53% and 41%, respectively, of the patients with a 100% success rate. In the DSP group, all 28 episodes of polymorphic ventricular tachycardia or ventricular fibrillation were converted by the first shock as compared to 57 of 69 episodes (83%) in the control group (p < 0.05). Monomorphic ventricular tachycardias were terminated by ATP alone in 96% versus 94%. Lead related problems were minor and observed in 5% and 7%, respectively. In summary, both leads were safe and efficacious in the detection and treatment of ventricular tachyarrhythmias. There were no differences between the DSP and control groups regarding short- or long-term lead related complications.

In 9 patients with a history of paroxysmal atrial fibrillation (AF), basket catheters with 64 electrodes were used to determine electrophysiologic aspects of onset and early minutes of AF in the right atrium. Mapping was performed using 32 bipolar recordings after induction of AF by programmed atrial stimulation. In 7 patients, registrations were obtained that allowed the onset of AF to be analyzed after the induction. The most common mode of induction was a conduction block and local fragmentation of electrical activation in the area anterior to the tricuspid valve; this was observed in 5 patients. Local cycle lengths (5 min) and correlation dimension of repolarization Dpw&#95;De (2 min) was calculated in 7 patients. The recording sites of the basket catheter were fluoroscopically projected to the anatomic sites of the right atrium. The highest Dpw&#95;Re dimensions as an expression of pronounced chaotic activity were found in the area anterior to the tricuspid valve.

Unlabelled: The aim of this study is the analysis of electrical failures in transvenous cardioverter/defibrillator (ICD) lead systems with regard to the importance of device implemented diagnostic and measurement functions and the potential role of an automated device-control in the detection of lead failures., Methods: All consecutive ICD patients at our institution were enrolled in this retrospective investigation. The routine follow-up controls consisted in a complete evaluation of all diagnostic and measurement ICD features and additional controls in case of spontaneous arrhythmia episodes., Results: Two hundred thirty patients, 193 male and 37 female, were enrolled in this study (mean age: 61.5 +/- 10.2 years; mean LVEF 32 +/- 9%). During a mean follow-up period of 29.5 +/- 18.4 (6-76) months, lead failure occurred in 19 patients (8%), 16 patients were implanted with an ICD, capable of diagnostic and measurement functions. All nonadequate device discharges could be classified as sensing-failure by stored electrograms. Device implemented measurement features revealed clinical important information in 13/16 patients (81%). In 14/16 patients, the lead defect could not be detected during routine follow-up. At the time of documented lead failure the safety of the implanted devices was already lost in 6/16 patients (38%)., Conclusions: Device implemented diagnostic and measurement options are of great importance in the early detection of ICD lead failures. The implementation of automated measurements of lead related parameters in connection with a patient alert function may contribute to a further increase in the safety of ICD therapy.

Unlabelled: The influence of blood flow cooling down the energy delivering electrode during temperature controlled radiofrequency energy application is an important factor for ablation success. In this experimental in-vitro study, using tempered saline as blood equivalent, we observed a highly significant increase in tissue temperature, lesion depth and required energy amount with increasing flow velocity. Second, we found significant deeper lesions with use of pulsed radiofrequency energy application compared to continuous application. We conclude that, even with lower electrode temperatures, success can be achieved dependent on the local blood flow velocity, and deeper lesions can be created with the use of pulsed radiofrequency energy application., Background: Success in temperature-controlled radiofrequency (RF) catheter ablation of arrhythmogenic areas in human hearts depend largely (among others) on the size of the electrode, developed pressure of electrode against tissue, as well as on the localization of the thermistor sensor within the electrode. In addition, the blood flow velocity at various sites of ablation is an important factor for the calculation of heat transport from the electrode, which obviously has not been given much consideration of in the past. The aim of the present in-vitro study, therefore, was to evaluate this important factor's influence on the temperature developed at the electrode and within the myocardial tissue., Methods and Results: All experiments were carried out in a bath containing NaCl solution at 37 degrees C. Four different flow velocities were applied (0, 110, 180, 320 ml/cm2 *min). During and after temperature-controlled unipolar radiofrequency energy delivery (60 degrees C, 40 sec) the electrode temperature, the tissue temperature 5 mm in depth, and the total energy delivered were measured, as well as the actual depth of the lesion. The amount of energy applied to the electrode was regulated by the thermosensor in the electrode to obtain a maximum temperature of 60 degrees C. Two different kinds of radiofrequency energy delivery have been used: (1) continuous radiofrequency energy delivery as usual regarding clinical use, (2) pulsed radiofrequency energy delivery with a duty cycle length of 10 ms and a pause of at least the same duration during two consecutive duty cycles. At pulsed radiofrequency energy application, the energy for each duty cycle was held constant during delivery. The amount of pulses delivered to the electrode was regulated by the electrode's thermosensor. With both modes of radiofrequency energy delivery a uniform observation could be made. The more the flow velocity applied accelerated, the more the tissue temperature rose (R = 0.85; p < 0.00000001), and the lesion depth increased in spite of electrode temperature being held constant. The amount of the total energy delivered rose in proportion to the cooling down of the electrode dependent on the flow velocity (R = 0.69, p < 0.0000004). Steady-state temperatures had not been accomplished after 40 sec time. When energy was delivered at the pulsed mode, intramyocardial temperatures proved higher compared to the continuous mode with significant differences (p < 0.05) at comparable flow velocities applied between 180 and 320 ml/cm2*min and at same electrode temperatures. This resulted in significantly (p < 0.05) larger lesion depths in pulsed radiofrequency energy delivery. We suppose that this significant difference can be explained by a higher amount of total energy delivered at comparable electrode temperature in the pulsed mode as compared to the continuous mode.

The aim of this retrospective study was to evaluate the necessity of the replacement of an implantable cardioverter/defibrillator (ICD) in patients with pulse generator battery depletion without an adequate, spontaneous arrhythmia episode during the life-time of the first implanted device. In this study 213 patients with implanted ICDs were enrolled. In 62 patients an elective generator replacement due to battery depletion was performed. Both patient groups (Group A: patients with generator replacement n = 62 and Group B: patients without replacement n = 151) were not different with regard to main clinical characteristics, such as underlying heart disease and left ventricular function. In both groups there was a predominance of male patients (Group A: 89%; Group B: 83%). The mean age was 58 +/- 11 years and 59 +/- 11 years in Group A and Group B, respectively. Coronary artery disease was present in 66% and 68% of the patients. There was a comparable left ventricular ejection fraction: Group A: 30.5 +/- 9% vs Group B: 31.9 +/- 9%. The follow-up time was much longer in Group A patients compared to Group B patients (50.5 +/- 14 vs. 16.5 +/- 11 months). For the total patient group there was a 5 year event-free probability of 23%, no differences were found between both groups. The subanalysis in Group A patients revealed no difference in the probability of ICD-shock occurrence prior to or after the replacement of the pulse generator. In 48/62 (77%) of Group A patients adequate ICD discharges were documented. In 15/62 (24%) patients shock occurred before and after generator replacement. In 6/62 (10%) of Group A patients, the first adequate ICD-therapy was documented after generator replacement. The results of this study indicate the necessity of an ICD-pulse generator replacement even in patients without an adequate device discharge during the life-time of the first implanted device.

The degree of left ventricular impairment in an acknowledged important prognostic marker of long-term outcome for patients being evaluated for implantation of cardioverter-defibrillators. Just how left ventricular function impacts freedom from all-cause mortality, as well as from sudden death and cardiac death, is a subject of current major debate, and is analyzed hereunder from a large, recent multicenter ICD patient cohort. The multicenter database consists of data from 361 patients receiving implantable cardioverter-defibrillators for standard indications, that is, documented episodes of ventricular fibrillation or sustained ventricular tachycardias with poor hemodynamic toleration. Data were collected from 1988 to 1995 at three centers in Germany. Two-hundred and three patients (56%) had a left ventricular ejection fraction (LVEF) > 0.30 (group I), and 158 patients (44%) had a LVEF < or = 0.30 respectively (group II). The mean follow-up was 23.9 months (range 3-98 months). Overall survival at 5 years for group II patients was lower, as expected, at 74.1% versus 94.2%, respectively (P < 0.0001). Mortality was higher for each different cause of death in group II patients than in Group I: sudden arrhythmic deaths, 5 versus 1 (P < 0.048); nonsudden cardiac deaths, 16 versus 5 (P < 0.002); noncardiac deaths, 7 versus 2 (P < 0.03). Group II patients received a higher rate of at least one presumably appropriate shock at 86 (54.4%) versus 89 (43.8%) in group I (P < 0.05). However (and somewhat surprisingly), neither the time from ICD implantation to death, comparing only the patients who died, nor the event-free probability of appropriate shocks due to very rapid, sustained ventricular arrhythmias (> 230 beats/min), including a presumed risk of sudden arrhythmogenic death, differed between groups I and II. Sudden cardiac death was only marginally affected by LVEF (group I, 1.5% actuarial, 5-year survival 99.5%; group II, 3.1% and 95.8%, respectively). Therefore, the lower overall survival in ICD patients with LVEF < or = 0.30 resulted mainly from causes of death that cannot be directly influenced by cardioverter-defibrillator therapy. However, because group II patients had a far higher incidence of at least one ventricular tachyarrhythmia terminated by ICD shocks than group I patients, they also probably derived benefit from ICD therapy.

A biatrial pacemaker was inserted in a 68-year-old female with paroxysmal atrial fibrillation and atrial flutter refractory to antiarrhythmic drugs based on a sick-sinus-syndrome and concomitant interatrial conduction delay. One electrode positioned in the right atrium and another electrode located in the coronary sinus were connected to a dual-chamber pacemaker. The electrode in the right atrium was connected to the atrial channel, the electrode in the coronary sinus to the ventricular channel. The pacemaker was programmed in DDD-mode with an AV-delay of 30 ms. Under a chronic antiarrhythmic medication with 160 mg sotalol per day there was no evidence for recurrent episodes of atrial tachyarrhythmias in the patient's history, 24-h-Holter-ECG, nor in the memory of the pacemaker during a follow-up of 8 months.

Introduction: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option., Methods and Results: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AF. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 +/- 9 min) and eight patients with chronic AF (6.6 +/- 5 months) were included. The fluoroscopy time for lead placement was 3.5 +/- 4.3 minutes. The atrial defibrillation threshold was 2.0 +/- 1.4 J for patients with acute AF and 9.2 +/- 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 +/- 1.1 mV during AF and 4.0 +/- 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 +/- 3.3 V (0.5-msec pulse width)., Conclusions: Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. This system might lead to a simpler, less invasive approach for internal atrial cardioversion.

The current therapy with implantable cardioverter/defibrillators (ICD) is lacking specificity. The technical concept of arrhythmia detection, as a single channel ventricular rate threshold does not provide a clear differentiation between supraventricular and ventricular rhythms. Nearly 25% of all ICD-therapies are related to a false positive detection of supraventricular arrhythmias.The use of alternative, non rate based detection algorithms is limited due to the reduced long-term stability of the sensors and due to a high battery drain. Based on the current concept of arrhythmia detection, the use of additional timing algorithms as the variability of consecutive RR-cycle length ("Rate-Stability") and the detection of a sudden acceleration in the ventricular rate ("Rate-Onset") provide a clinical relevant increase in specificity in ICD-therapy. A further class of detection algorithms uses the morphologic assessment of intracardiac electrograms. Despite the fact that these morphology based algorithms have shown a high sensitivity and specificity in the discrimination between ventricular and non-ventricular rhythms, only one algorithm was implemented in ICD-generators and the clinical importance in ICD-therapy was very small. In 1995 a new morphology based detection algorithm was introduced in ICD-therapy. The "width criterion" is based on the measurment of the duration of the intracardiac signal. In 1995 and 1996 the first two series of a dual chamber ICD system were introduced in clinical ICD-therapy. These devices provide a two-channel atrio-ventricular arrhythmia detection in connection with a DDD antibradycardia pacing therapy. The use of DDD-ICD systems is expected to be a great step forward to enhance diagnostic specificty. A number of rate and timing detection algorithms and algorithms comparing the assoziation of atrial and ventricular signals may improve the discrimination between supraventricular and ventricular tachyarrhythmias. The future implementation of additional morphology based detection algorithms in DDD-ICD systems may solve the problem of the limited detection specificity in clinical ICD-therapy.

In implantable cardioverter-defibrillator therapy with endocardial lead systems, certain clinical variables are associated with defibrillation energy requirements. Because of the weak correlation coefficients, these variables cannot predict defibrillation thresholds in individual patients.

The first report about successful radio frequency ablation of a right-posterior-septal accessory pathway appeared in 1986. Since then, the technology of both guidable ablation catheters and radio frequency generators has been considerably improved in an initially clinical-experimental phase. At the same time, electrophysiologists were equally able to enlarge their knowledge in the field of signal characteristics of arrhythmogenic substrates. This included the discovery of action potentials of accessory pathways (preexcitation syndromes), the location of fast and slow AV node conduction (AV nodal reentrant tachycardia, AVNRT), the functional importance of the anatomical isthmus between the os of the coronary sinus, the tricuspid valve and the inferior caval vein (atrial flutter). Mapping techniques such as transient and concealed entrainment became, among others, significant tools in finding the best localization for radio frequency catheter ablation. Thus, technical development and the increased knowledge of clinical electrophysiologists resulted in firmly establishing the procedure of catheter ablation as the method of first choice in the curative treatment of supraventricular tachycardias in a potential collective of about 5 per mill of the normal population (without atrial fibrillation). Supraventricular tachycardias with a reentry mechanism in the broadest sense (> 95% of all pts. with SVT) and those with focal automaticity (< 5%) occur as atrial fibrillation or atrial flutter in about 60% of all pts. (4-6 per mill of the normal population). Manifestation of the remaining reentrant tachycardias is mainly in the form of AVNRT (retrograde conduction via the fast pathway > 90% versus uncommon type < 10%). AV reentry via accessory pathways is found in about 15%, with orthodromic conduction via the AV node (> 90%). Atrial reentrant tachycardias are rather rare (with the exception of atrial fibrillation/flutter). The literature suggests medical therapy to be successful in about 60% of these patients. Those patients who are presently proposed to receive radio frequency catheter ablation usually continue to be symptomatic despite pharmacological therapy and/or have a potential risk for sudden cardiac death due to atrial fibrillation in WPW syndrome, or rate-dependent hemodynamic compromise secondary to cardiac disease. Since 1989-1995, our laboratory had a > 93% success rate in treating 466 patients with AV reentrant tachycardia via accessory AV pathways, and in treating 398 patients with AV nodal reentrant tachycardias. Forty patients with atrial flutter and 16 patients with different atrial tachycardias (14 with focal origin, 2 reentries) were free from tachycardia in 80% after ablation. This corresponds to the literature published by other centers. Some abstracts and articles suggest that ablation of atrial fibrillation may be possible. However, there is still a lack of basic experience with view to mapping procedures and, thus, insufficient knowledge of the electrophysiological pathophysiology with regard to different cardiac diseases. As a consequence, this procedure, despite first documentation of both successful treatment and severe complications occurring in catheter ablation of atrial fibrillation, as based on the experience of the MAZE procedure, is applied in humans, at the time being, in a purely experimental setting. The only exception relates to the ablation of the AV node at accurate diagnosis for pacemaker implantation (VVIR; DDDR switch mode) which has become part of routine therapy, although, of course, atrial fibrillation itself or necessary anticoagulation cannot be abolished. Thus, our center shows a success rate of 98% in treating 117 patients by this method. First promising reports are available describing the attempt of AV node modification in the posterior nodal part with the goal of reducing the ventricular rate in atrial fibrillation.

Introduction: The extraction of chronically implanted and infected pacemaker and defibrillator leads is an important issue. This article describes the experience gathered between 1990 and 1994 by seven European centers regarding a locking stylet that is uniformly applicable for a wide variety of internal pacing coil diameters. This interventional locking stylet for lead extraction has an outer diameter of 0.4 mm (0.016 inches). The stylet consists of a hollow shaft in which an inner traction wire is embedded. At the tip of the inner traction wire an anchoring mechanism, which can be opened by retraction, is applied. Removal attempts were made for 150 leads, 110 in ventricular and 40 in atrial positions., Results: Complete removal was possible in 122 cases (81%). Partial removal was possible in 18 cases (12%). Failure to remove the lead with the extraction stylet was experienced in 10 cases (7%). In seven patients, the leads were removed by cardiothoracic surgery; 3 defective leads were left in place. There were no serious complications associated with the procedure. None of the patients died., Conclusion: The experience with this extraction stylet for lead removal has shown good results. Despite a low complication rate thus far, each case for lead removal should be judged on the individual basis of benefit-to-risk ratio.

The aim of this study was to evaluate the incidence of valve lesions after radiofrequency catheter ablation of accessory atrioventricular pathways using the retrograde transaortic approach. Patients who presented no preexisting detectable valve lesion prior to catheter ablation and who underwent a comparable echocardiographic examination prior to and after catheter ablation were included for data analysis. From January 1991 until May 1993, 113 patients underwent radiofrequency catheter ablation of a left-sided accessory atrioventricular pathways at our institution. Fifty-nine patients were included in this study. Five patients (8.4%) developed new valve lesions after radiofrequency catheter ablation. There were two cases (3.3%) of aortic regurgitation and four cases (6.7%) of mitral regurgitation. In the majority of cases only mild valve regurgitation was detected. A hemodynamically significant valve lesion was observed in a single patient (1.6%). We speculate that the new onset of valve lesions is mostly due to catheter manipulations rather than due to tissue injury related to radiofrequency current application. Echocardiographic examinations prior to and after radiofrequency catheter ablation of accessory pathways may contribute to a further reduction in intervention-related complications.

This report describes the distribution of automatically measured values of enhanced arrhythmia detection parameters such as "rate stability" and "rate onset" in various forms of spontaneous arrhythmia episodes in patients treated with a new, third-generation, tiered therapy implantable cardioverter defibrillator (ICD). The study population consisted of 27 patients who received the Ventak PRxII cardioverter defibrillator, which provides extensive diagnostic options such as electrogram storage capabilities, and the ability to store measured values of additional arrhythmia detection parameters such as rate stability and rate onset during spontaneous arrhythmia episodes. During a follow-up period of 11.1 +/- 5.2 months, this device detected 264 arrhythmia episodes. The analysis of stored electrograms revealed 13 episodes of sinus tachycardia, 52 episodes of atrial tachyarrhythmias, and 201 episodes of monomorphic ventricular tachycardias (VTs). The mean measured values of rate stability and rate onset were: 2.2 +/- 0.9 msec, 0% in sinus tachycardias; 41.0 +/- 24.1 msec, 8.5% +/- 9.5% in atrial tachyarrhythmias; and 7.8 +/- 6.0 msec, 30.6% +/- 12.1% in monomorphic VTs. There was a wide zone of overlapping measured values for rate stability and rate onset in ventricular and nonventricular rhythms. No episode of VT showed a measured rate stability criterion > 35 msec. The subanalysis of arrhythmia episodes presenting with a heart rate < 160 beats/min revealed no episode of VT with a rate stability value > 24 msec. The calculated, rate dependent specificities for these programmed rate stability parameters in detecting VTs were 46.2% and 81.8%, respectively. The analysis of the rate onset algorithm revealed no comparable relationship between sensitivity and specificity in the detection of VTs.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 +/- 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF < or = 30% (n = 20), and group B with LVEF > 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 +/- 16 beats/min; group B: 180 +/- 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P < 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P < 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

The vast majority of cardioverter/defibrillator implantations is performed with non-thoracotomy lead systems. The temporal stability of defibrillation energy requirements is well established for epicardial defibrillation lead systems, but not for non-thoracotomy lead systems. The defibrillation energy requirements were reevaluated in 30 patients, 13 months after implantation of a cardioverter/defibrillator with a non-thoracotomy lead system. The study patients group consisted of 4 females and 26 males; mean age 60.1 +/- 10.5 years; mean left ventricular ejection fraction was 32.2 +/- 6.2%. Coronary artery disease was the underlying heart disease in 12 patients, dilated cardiomyopathy in 15 patients, and artificial valve replacement in 3 patients. There was no clinical progression in the underlying heart disease between defibrillator implantation and control measurements; left ventricular ejection fraction was unchanged (32.2 +/- 6.2 vs. 32.3 +/- 6.4%); no changes occurred regarding patients' clinical status. In 27/30 patients the defibrillation threshold at defibrillator implantation could be reconfirmed at control measurements. The mean defibrillation energy/requirements at implantation (14.4 +/- 4.8 Joules) were unchanged compared to control measurements (14.8 +/- 4.6 Joules). A temporal stability of defibrillation energy requirements could be established for the monophasic (n = 15; 18.0 +/- 4 vs. 18.1 +/- 3.4 Joules) as well as for the biphasic waveform (n = 15; 11.1 +/- 3.4 vs. 11.5 +/- 2.9 Joules). The results of intraoperative defibrillation thresholds measurements are predictive for chronic defibrillation energy requirements in patients with non-thoracotomy lead systems.

Three months after orthotopic cardiac transplantation, a 46-year-old man developed paroxysmal supraventricular tachycardia. Electrophysiological investigation of the arrhythmia led to the diagnosis of an atrioventricular reentrant tachycardia involving a left lateral concealed accessory pathway. When antiarrhythmic drugs failed to suppress the arrhythmia, radiofrequency catheter ablation of the accessory pathway was performed without complication.

Despite all advances in the diagnostic and therapy of cardiovascular diseases the mortality from malignant ventricular tachyarrhythmias is still a major health problem. In addition to established therapeutic strategies in the prevention of sudden cardiac death such as antiarrhythmic drug treatment, catheter ablation or antiarrhythmic surgery the implantable cardioverter/defibrillator was introduced to clinical practice in 1980. The number of 50,000 overall implants reflects the current clinical status of the therapy with implantable cardioverters/defibrillators. Significant technical improvements in the defibrillator therapy may contribute to an increase in therapy acceptance. These advances include the introduction of nonthoracotomy lead systems, enhanced defibrillation efficacy, full programmable devices providing tiered electrical therapy, improved diagnostic Holter functions and enhanced arrhythmia detection algorithms. The major present goals of defibrillator therapy are, detection and termination of malignant ventricular tachyarrhythmias, reduction of sudden cardiac death, reduction in patient's mortality and improvement in quality of life. The efficacy and safety of defibrillator therapy to prevent sudden arrhythmic death has been proven in several large clinical investigations. The annual sudden cardiac death mortality is < 2% even in high-risk patient populations. Compared to sudden cardiac death rate there is a much higher rate of overall cardiac mortality because a defibrillator is not able to prevent nonarrhythmic cardiovascular deaths. There is a clinical impression that cardiovascular mortality is lower in patients treated with an implantable cardioverter/defibrillator compared to patients treated with other therapies. However there are no results from controlled studies providing scientific evidence that defribillator therapy can reduce overall cardiovascular mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

A knowledge of electrophysiological parameters of accessory atrioventricular conduction pathways, such as effective refractory time and high conduction capacity in atrial fibrillation, make it possible to detect those patients who are at risk of life-threatening ventricular tachyarrhythmias. One criterion to identify these electrophysiological parameters is persistent pre-excitation after intravenous administration of ajmaline in Wolff-Parkinson-White (WPW) syndrome. Sensitivity and specificity of the ajmaline test in detecting patients at risk of life-threatening ventricular tachyarrhythmias were evaluated in 58 consecutive patients (22 females, 36 males; mean age 40.2 +/- 13 years) with the WPW syndrome. Pre-excitation was blocked after ajmaline in 43 patients (74%), pre-excitation persisting in 15 (26%). In 26 of the 43 patients with blocked pre-excitation the ajmaline test indicated short effective refractory time (< 270 ms) of the accessory pathway, and a high conduction capacity in 19 (minimal pre-excitation R-R interval during atrial fibrillation of < 250 ms). Sensitivity of the ajmaline test in the detection of a short refractory time was 33.3%, specificity 89.4%, while the corresponding values were 40.6% and 92.3% for the detection of accessory pathways with high conduction capacity in atrial fibrillation. These data show that the ajmaline test is not useful for estimating the electrophysiological characteristics of the accessory pathways. It is thus of only subordinate diagnostic value in predicting how much patients with the WPW syndrome are at risk of serious ventricular tachyarrhythmias.

Several clinical studies have proved increased defibrillation efficacy for implantable cardioverter defibrillators with biphasic pulse waveforms compared to monophasic pulse waveforms. This difference in defibrillation efficacy depends on the type of defibrillation lead system used. The influence of biphasic defibrillation pulse waveforms on the defibrillation efficacy of purely endocardial defibrillation lead systems has not yet been sufficiently examined, we, therefore studied 30 consecutive patients with drug refractory ventricular tachyarrhythmias during the implantation of a cardioverter defibrillator. After implanting an endocardial "integrated" sensing/defibrillation lead we performed a prospective randomized comparison of the defibrillation efficacy of monophasic and biphasic defibrillation waveform pulses. For endocardial defibrillation with the biphasic waveform the mean defibrillation threshold was 12.5 +/- 4.9 joules and for the monophasic waveform 22.2 +/- 5.6 joules (P < 0.0001). There was a decrease in the required defibrillation energy of biphasic defibrillation in 29/30 patients. Thus considering purely endocardial defibrillation a statistically significant and clinically relevant increase in defibrillation efficacy can be demonstrated for biphasic defibrillation waveform pulses.

Twelve patients with severe heart failure (NYHA class III-IV) were investigated by intraindividual comparison for the hemodynamic and neurohumoral effects of dopamine (3 and 6 micrograms/kg/min), enoximone (8 micrograms/kg/min), and the combination of both medications (dopamine 3 micrograms/kg/min+enoximone 8 micrograms/kg/min) using right heart catheterization. The duration of active treatment was 8 h for each substance with a subsequent washout time of 16 h. Dopamine led to a dose-dependent increase in cardiac index of 10-13% and 18-37% under 3 and 6 micrograms/kg/min, respectively (p < 0.001). Enoximone monotherapy produced a comparable increase in cardiac index between 27 and 32% (p < 0.001). Enoximone, but not dopamine, resulted in a significant decrease in mean pulmonary artery pressure (21-26%; p < 0.01), pulmonary capillary wedge pressure (24-30%; p < 0.01), and right atrial mean pressure (26-28%; p < 0.001). The systemic vascular resistance was without significant changes at low-dose dopamine therapy, decreased by 10-19% insignificantly at a dose of 6 micrograms/kg/min, and reached the level of significance with enoximone therapy (-20 to -25%; p < 0.001). There was a highly significant decrease by 49-55% in systemic vascular resistance with enoximone (p < 0.001), in contrast to dopamine. Heart rate and blood pressure remained without significant changes at low-dose dopamine, with the heart rate increasing significantly by 25% at a dose of 6 micrograms/kg/min within the first 2 h (p < 0.01). Enoximone produced a heart rate increase by 8-13% (being significant after 2 h; p < 0.05) with no changes in blood pressure. The combination therapy with dopamine and enoximone led to an additive increase in cardiac index by 35-43% (p < 0.001), a decrease in right atrial mean pressure by 28-36% (p < 0.01), a decrease in systemic vascular resistance by 27-30% (p < 0.01) and in pulmonary vascular resistance by 46-51%. An additive effect on heart rate was not observed. The respective monotherapies with low-dose dopamine and enoximone had no remarkable effect on plasma catecholamines, while dopamine at a dose of 6 micrograms/kg/min and combination therapy led to a significant increase in noradrenaline levels. There was a highly significant decrease in the plasma concentration of the atrial natriuretic factor under enoximone and combination therapy (p < 0.001) as well as a significant decrease in aldosterone (0 < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)