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Aims: Intracardiac electrograms (IEGMs) recorded by implantable cardioverter-defibrillators (ICDs) are essential for arrhythmia diagnosis and ICD therapy assessment. Short IEGM snapshots showing 3-10 s before arrhythmia detection were added to the Biotronik Home Monitoring system in 2005 as the first-generation IEGM Online. The RIONI study tested the primary hypothesis that experts' ratings regarding the appropriateness of ICD therapy based on IEGM Online and on standard 30 s IEGM differ in <10% of arrhythmia events., Methods and Results: A total of 619 ICD patients were enrolled and followed for 1 year. According to a predefined procedure, 210 events recorded by the ICDs were selected for evaluation. Three expert board members rated the appropriateness of ICD therapy and classified the underlying arrhythmia using coded IEGM Online and standard IEGM to avoid bias. The average duration of IEGM Online was 4.4±1.5 s. According to standard IEGM, the underlying arrhythmia was ventricular in 135 episodes (64.3%), supraventricular in 53 episodes (25.2%), oversensing in 17 episodes (8.1%), and uncertain in 5 episodes (2.4%). The expert board's rating diverged between determinable IEGM Online tracings and standard IEGM in 4.6% of episodes regarding the appropriateness of ICD therapy (95% CI up to 8.0%) and in 6.6% of episodes regarding arrhythmia classification (95% CI up to 10.5%)., Conclusion: By enabling accurate evaluation of the appropriateness of ICD therapy and the underlying arrhythmia, the first-generation IEGM Online provided a clinically effective basis for timely interventions and for optimized patient management schemes, which was comparable with current IEGM recordings.

Wide QRS complex and asynchronous myocardial contraction in heart failure are associated with poor prognosis. Resynchronization can be achieved by biventricular pacing (BVP), which leads to hemodynamic and clinical improvement and reverse remodeling, and may improve survival. However, there is a substantial subset of patients with wide QRS complexes in the electrocardiogram who does not improve despite BVP, and there are findings which suggest that resynchronization therapy may be also beneficial for heart failure patients with normal QRS duration. QRS width predicts the benefit of BVP only with limitation and only correlates weakly with echocardiographically determined myocardial asynchrony. Determination of asynchrony by tissue Doppler echocardiography seems to be the best predictor for improvement after BVP, although no consensus on the optimal method to assess asynchrony has yet been achieved. To date, most studies evaluating tissue Doppler echo in BVP were performed retrospectively and only one prospective study with patient selection for BVP according to echocardiography and electrocardiography criteria of asynchrony has been published. These new echocardiographic tools will help to prospectively select patients for BVP, help to guide implantation and to optimize device programming.

Aims: We prospectively evaluated results from cardiopulmonary exercise testing for chronotropic incompetence (CI) in a cohort of 292 pacemaker patients. In addition, we evaluated comorbidity and antiarrhythmic patient data as indicators of CI., Methods and Results: On the basis of exercise stress testing and application of the definition of CI by Wilkoff, 51% of our cohort was categorized as having CI. Indications for pacemaker implant for this patient group were 42% atrioventricular block, 56% sinus node disease, and 59% atrial fibrillation. Maximum oxygen uptake (VO(2) max) and exercise duration were significantly reduced among CI pacemaker patients, whereas oxygen uptake at the anaerobic threshold remained unchanged. The following clinical characteristics were significant predictors of CI: existence of coronary artery disease (P = 0.038), presence of an acquired valvular heart disease (P = 0.037), and former cardiac surgery (P = 0.041). Age, gender, arterial hypertension, cardiomyopathy, congenital heart disease, left ventricular ejection fraction, and time period between stress-exercise examination and pacemaker implantation were not significant predictors of CI. Chronic antiarrhythmic therapy with digitalis (P = 0.013), beta blockers (P = 0.036), and amiodarone (P = 0.045) were significant predictors of CI. In contrast, medication with class I and IV antiarrhythmics had no significant correlation with CI., Conclusion: We found the following characteristics predictive of CI in this pacemaker patient population: VO(2) max, existence of coronary artery disease or acquired valvular heart disease, previous cardiac surgery, as well as medication with digitalis, beta blockers, and amiodarone.

Chronotropic incompetence (CI), which has not been systematically examined in the ICD patient population, may have implications for device programming. A total of 123 ICD patients were classified into three groups: single-chamber ICD with sinus rhythm, dual-chamber ICD with sinus rhythm, and single-chamber ICD with permanent atrial fibrillation. Heart rate response, maximum oxygen uptake, and oxygen uptake at the anaerobic threshold were measured during treadmill exercise testing. In addition, clinical variables such as antiarrhythmic drug therapy, underlying heart disease, and left-ventricular (LV) ejection fraction were recorded. Of the patients studied, 38% were chronotropically incompetent (47/123). Significant predictors of CI were as follows: presence of a coronary disease (P = 0.036), prior cardiac surgery (P = 0.037), chronic drug therapy with beta-blockers (P = 0.032), administration of amiodarone (P = 0.025), and a combination of these two forms of treatment (P = 0.01). Spiroergometry revealed reduced exercise capacity (P = 0.041) and lessened VO2max (P = 0.034) among chronotropically incompetent patients. A large percentage of ICD patients demonstrates CI with subsequently reduced physical stress tolerance. In light of the DAVID study, we believe that a closer examination of rate-adaptive modes for ICD patients is warranted under enhanced conditions: (1) optimized AV interval programming; (2) utilization of new algorithms to reduce ventricular pacing in combination with rate-adaptive atrial pacing, with the goal of addressing CI while minimizing ventricular pacing; and (3) an optimized upper heart-rate limit.

Background: Dual chamber pacing typically results in a high percentage of ventricular pacing. A number of studies have been conducted suggesting detrimental effects of ventricular desynchronization produced by long-term RV pacing. Pacemaker algorithms that extend the AV interval to uncover intrinsic AV conduction have been utilized to reduce ventricular pacing. These algorithms are often limited to AV intervals below 250 ms limiting the ventricular pacing reduction. We hypothesized that by allowing AV intervals to extend beyond 300 ms, a marked reduction in RV pacing can be achieved., Methods: A total of 30 patients (17 men, mean age 71 +/- 9) with standard Brady indications, and implanted with a Medtronic Kappa 700 pacemaker, were randomized to 2-week treatments with default Search AV (KSAV) parameters or Enhanced Search AV (ESAV) parameters. The Enhanced Search AV algorithm included the capability for continuous adjustment of AV delays and the ability to auto disable in patients with persistent AV block., Results: Among patients with intact AV conduction, percent VP was greater in KSAV versus ESAV (70 +/- 40% vs 19 +/- 28%, P < 0.001). In patients with persistent AV block, the algorithm suspended appropriately and there was no significant change in the percent VP between both arms of the study. In 18/22 patients, percent VP was reduced below 40%., Conclusions: Substantial reduction in ventricular pacing can be achieved by allowing the AV interval parameters to extend beyond 300 ms using the ESAV algorithm. In patients with AV block, ESAV suspended and patients were paced at their nominal settings.

Asynchronous myocardial contraction in heart failure is associated with poor prognosis. Resynchronization can be achieved by biventricular pacing (BVP), which leads to clinical improvement and reverse remodeling. However, there is a substantial subset of patients with wide QRS complexes in the electrocardiogram that does not improve despite BVP. QRS width does not predict benefit of BVP and only correlates weakly with echocardiographically determined myocardial asynchrony. Determination of asynchrony by Tissue Doppler echocardiography seems to be the best predictor for improvement after BVP, although no consensus on the optimal method to assess asynchrony has been achieved yet. Our own preliminary results show the usefulness of Tissue Doppler Imaging and Tissue Synchronization Imaging to document acute and sustained improvement after BVP. To date, all studies evaluating Tissue Doppler in BVP were performed retrospectively and no prospective studies with patient selection for BVP according to echocardiographic criteria of asynchrony were published yet. We believe that these new echocardiographic tools will help to prospectively select patients for BVP, help to guide implantation and to optimize device programming.

For effective management of drug-refractory atrial fibrillation as the most common arrhythmia new methods are needed. In case of existing interatrial conduction disturbance the use of biatrial pacemaker with standard right atrial lead and additive coronary sinus lead for left atrial pacing shows an antiarryhthmic effect due to atrial resynchronisation. In order to demonstrate the antiarrhythmic effect of biatrial pacing, 74 pts. (26 f/48 m, mean age 63 +/- 9.4 y, follow-up 482 +/- 183 days) received a biatrial pacemaker (AAD-mode, AV-delay 0 msec, LOGOS, Fa. Biotronik) from 11/97 to 03/99. All patients had a prolongation of P-wave duration more than 100 msec (mean 122.3 +/- 23.1 msec). Preoperatively 9/74 (12%) pts. had monthly, 49/74 pts. (66%) had weekly, and 11/74 pts. (15%) had daily episodes of atrial fibrillation. Permanent atrial fibrillation > 6 month was seen in 5/74 pts. (7%, preoperative cardioversion). The intraoperative right atrial pacing threshold was 0.89 +/- 0.64 V (0.5 msec pulse width), the atrial signal amplitude 2.31 +/- 1.03 mV, the impedance signal 616 +/- 157 omega. Voltage recording in the coronary sinus showed a pacing threshold of 1.4 +/- 0.68 V (0.5 msec pulse width) and a potential of 3.47 +/- 1.44 mV. The impedance signal was 559 +/- 137 omega. The obtained P-wave duration was reduced for 33.9 +/- 20.1 msec. In 7/74 pts. (9.4%) we found a dislocation and in 4/74 pts. (5.4%) an excessive high pacing threshold of coronary sinus lead > 4 V/0.5 msec. All pts. with dislocated lead were reoperated. There were no perforations and thromboses of coronary sinus. The intervention led to a significant inhibition of atrial fibrillation in 11/74 pts. (14.9%) without and in 17/74 pts. (24.3%) with antiarrhythmic drugs. 17/74 pts. (24.3%) had a reduction of episodes without and 16/74 pts. (21.6%) with concomitant medication. The treatment did not have any influence on the prevalence of atrial fibrillation in 9/74 pts. (27%). In conclusion, the implantation of biatrial pacemaker leads to a significant reduction of atrial fibrillation episodes and has proven to be practicable and safe for clinical use.

Electrogram signals recorded from typical pacemaker implantation sites may be useful for a variety of pacemaker system functions including pacemaker follow-up, atrial and ventricular sensing (event detection), and triggered electrogram storage. We quantified the electrical characteristics of pacemaker pocket electrograms using a subcutaneous electrode array (SEA) in a population of 48 patients undergoing initial or replacement pacemaker implantation. SEA recorded intrinsic R wave amplitudes measured peak to peak averaged 118 microV and 65 microV for the two recorded SEA electrograms and were significantly different (P < 0.001); paced R wave amplitudes averaged 180 microV and 110 microV. P wave amplitudes averaged 39 microV and 26 microV. No statistically significant difference in amplitudes were observed between acute versus chronic pacemaker pocket or indication for pacing (AV block, sick sinus syndrome). Signal to noise ratios, using R wave amplitude as signal, were lower in the SEA electrogram on average (11 dB) compared to the intracardiac electrogram (27 dB), but sufficient for diagnostic assessment. R wave/P wave ratios for SEA signals were lower than surface and intracardiac values 3.1 and 2.7 compared to a range of 6.2-9.8, indicating a relative enhancement of P waves to R waves in SEA signals. In summary, SEA electrograms are of sufficient amplitude and signal quality (signal to noise ratio) to hold promise for future implantable device features such as electrogram telemetry, enhanced sensing, and diagnostic data storage.