Notes: SCHUCHERT, A., et al.: Adjustment of the Evoked Response Sensitivity After Hospital Discharge in Pacemaker Patients with Automatic Ventricular Threshold Tracking Activated. Automatic threshold tracking in cardiac pacemakers allows ventricular capture verification and self-adaptive pacing output regulation. The Autocapture algorithm detects the evoked response (ER) signal immediately after the pacing pulse to verify the efficacy of ventricular pacing. Before hospital delivery, the ER sensitivity must be programmed individually so that the pacemaker detects the ER signal adequately without sensing lead polarization. The aims of the study were to assess the frequency of patients in whom Autocapture could be activated and whether the ER sensitivity had to be adjusted after hospital discharge. The study included 44 patients who received the VVIR pacemaker Regency SR+ (St. Jude Medical) connected to the model 1450 T pacing lead. ER signal, lead polarization, and ER sensitivity were evaluated before hospital discharge and 1, 3, and 6 months after implantation. The system recommended activating Autocapture in 42 of 44 patients. The mean ER signal was 8.4 ± 1.2 mV at discharge, 9.0 ± 3.9 mV at month 1, 8.9 ± 4.9 mV at month 3, and 9.3 ± 4.5 mV at month 6. Polarization was 1.0 ± 0.1 mV at discharge, 1.1 ± 0.5 mV at month 1, 1.1 ± 0.2 mV at month 3, and 1.1 ± 0.5 mV at month 6. Mean ER sensitivity was 3.7 ± 1.8 mV at discharge, 4.0 ± 1.8 mV after 1, 4.1 ± 2.2 mV after 3, and 4.1 ± 1.8 mV after 6 months. ER sensitivity could remain unadjusted in 14 patients. Programming to a less sensitive ER setting from 2.9 ± 1.2 mV to 4.3 ± 1.5 mV was possible in 21 patients. Programming to a more sensitive ER setting from 4.1 ± 1.1 mV to 2.5 ± 0.9 mV was required in nine patients because of the decrease of the ER signal. The automatic threshold tracking algorithm Autocapture could be activated in 95% of patients. Programming to more sensitive ER settings was recommended in 21% of the patients after hospital discharge. Therefore, ER signal and polarization must be checked at each follow-up, as a decrease in ER signal amplitude can make reprogramming of the ER sensitivity necessary. There is no risk for the patient if the ER is not sensed, as high voltage backup stimulation is present.

Notes: NIEHAUS, M., et al.: Multicenter Experiences with a Single Lead Electrode for Dual Chamber ICD Systems. Monitoring of atrial signals improves the accuracy in identifying supraventricular tachyarrhythmias to prevent inappropriate therapies in patients with implantable ICDs. Since difficulties due to the additional atrial lead were found in dual chamber ICD systems with two leads, the authors designed a single pass VDD lead for use with dual chamber ICDs. After a successful animal study, the prototype VDD lead (single coil defibrillation lead with two additional fractally coated rings for bipolar sensing in the atrium) was temporarily used in 30 patients during a German multicenter study. Atrial and ventricular signals were recorded during sinus rhythm (SR), atrial flutter, AF, and VT or VF. The implantation of the lead was successful in 27 of 30 patients. Mean atrial pacing threshold was 2.5 ± 0.9 V/0.5 ms, mean atrial impedance was 213 ± 31Ω. Atrial amplitudes were greater during SR (2.7 ± 1.6 mV) than during atrial flutter (1.46 ± 0.3 mV, P 〈 0.05) or AF (0.93 ± 0.37 mV, P 〈 0.01). During VF atrial “sinus” signals had significantly (P 〈 0.01) lower amplitudes (1.4 ± 0.52 mV) than during SR. The mean ventricular sensing was 13.3 ± 7.9 mV and mean ventricular impedance was 577 ± 64Ω. Defibrillation was successful with a 20-J shock in all patients. In addition, 99.6% of P waves could be detected in SR and 84.4% of flutter waves during atrial flutter. During AF, 56.6% of atrial signals could be detected without modification of the signal amplifier. In conclusion, a new designed VDD dual chamber lead provides stable detection of atrial and ventricular signals during SR and atrial flutter. Reliable detection of atrial signals is possible without modification of the ICD amplifier.

Notes: BORIANI, G., et al.: Evaluation of a Dual Chamber Implantable Cardioverter Defibrillator for the Treatment of Atrial and Ventricular Arrhythmias. Eighty-nine patients with a documented history of atrial tachyarrhythmias or fibrillation (AF) received a cardioverter defibrillator designed to selectively differentiate and treat atrial and ventricular arrhythmias. Twenty-two patients received a coronary sinus lead and, therefore, could use a separate shock vector for selective treatment of atrial tachyarrhythmias/AF. The device is designed to treat tachyarrhythmias with antitachycardia pacing (ATP) and/or shock therapy using an atrial and/or a ventricular shock vector. Patients underwent induction and shock termination of atrial or dual tachyarrhythmias (AF/VF) to verify proper device function and to measure the arrhythmia detection time with enhancements and preventive algorithms programmed On and Off, respectively. Detection time for 329 VF inductions was 2.41 ± 0.64  seconds with enhancements On and 2.29 ± 0.47 with enhancements Off (NS). At implant or predischarge, 283 AF and/or AF/VF (121 atrial and 162 atrial/ventricular fibrillation) were induced. Shock conversion efficacy was 89.8% with AF conversion energies ranging from 0.9 to 27 J. Thirteen of the 23 patients had atrial shock conversions using the separate shock vector with an average conversion energy of 1.9 ± 1.4  J . (range 0.5–5 J). During follow-up the efficacy of ATP on atrial tachyarrhythmias was 59% and the efficacy of delivered shocks on AF was 85%. This new dual chamber cardioverter defibrillator appropriately detected and classified atrial arrhythmias, and shock therapy for AF was highly effective. The detection algorithm differentiated atrial tachyarrhythmia/AF and did not delay VF detection. The separate shock vector converted induced AF with energies ranging from 0.6 to 5 J. (PACE 2003; 26[Pt. II]:461–465)

Notes: SCHUCHERT, A., et al.: A Randomized Study on the Effects of Pacemaker Programming to a Lower Output on Projected Pulse Generator Longevity. The programmability of cardiac pacemakers enables the physician at follow-up to adjust the pacing pulse under consideration of the 100% safety margin with respect to the individual pacing threshold. The purpose of reducing the output is to prolong pacemaker longevity. The aims of this prospective, randomized trial were to compare the effects of nominal output versus a lower output on projected pacemaker longevity in single and dual chamber pacemakers. The secondary aim was to assess how many patients can be programmed to 2.5 V/0.4 ms instead of the nominal 3.5-V setting with ≥ 100% safety margin. The patients received the same types of VVI or DDD pacemakers that were connected in the ventricle to the steroid-eluting, high impedance pacing lead. At the 3-month follow-up, patients with ventricular pacing thresholds ≤ 0.15 ms at 2.5-V pulse amplitude were randomized to 3.5 V or 2.5 V amplitude at 0.4-ms pulse duration. Lead function and projected device longevity were assessed with the pacemaker's telemetry 6 and 12 months after implantation. Of patients implanted with a VVI pacemaker, at the 3-month follow-up, 3 patients had pacing thresholds 〉 0.15 ms at 2.5 V and 139 patients could be randomized. A reprogramming to a higher output was necessary in one patient. The mean percentage of ventricular pacing was about 40% throughout the study time. The programming to 2.5-V output resulted in an insignificant increase of device longevity from 117.9 ± 18.7 months in the nominal group to 123.7 ± 11.9 months at the 12-month follow-up (P = 0.16). Of patients implanted with a DDD pacemaker, 166 patients underwent randomization. The mean percentage of ventricular pacing was 85% in the ventricle and 35% in the atrium. The 2.5-V setting significantly prolonged pacemaker longevity from 98.1 ± 21.3 to 112.0 ± 13.6 months (P 〈 0.0001). In three (1%) patients a late increase of the pacing threshold was observed. Due to the low ventricular pacing thresholds, the 2.5-V/0.4-ms setting provided, 3 months after implantation, a ≥ 100% safety margin in 99% of the patients. Programming to a lower output slightly increased projected pacemaker longevity compared to the nominal 3.5-V setting. Longevity increased for 5% in patients with single and for 14% in dual chamber pulse generators.

Notes: Atrial synchronous ventricular pacing seems to be the best pacing mode for patients with advanced AV block and impaired LV function. The long-term follow-up of single lead VDD pacing was studied in 33 patients with impaired LV function and compared to 42 patients with normal LV function. All patients received the same VDD lead and VDDR pacemaker. The lead model with 13-cm AV spacing between the atrial and ventricular electrode was implanted in 89% of the patients. Follow-ups were 1, 3, 6, and 12 months after implantation. The percentage of atrial sensing and the P wave amplitude were determined at each follow-up. Minimal P wave amplitude at implantation was 2.0 ± 1.4 mV in patients with impaired and 1.7 ± 0.9 mV with normal LV function (not significant). At the 12-month follow-up, 33 patients with normal and 23 patients with depressed LV function remained paced in the VDD mode. The remaining patients died in five (impaired LV function) and seven cases (normal LV function) or their pacemakers were programmed to the VVI/VVIR pacing mode in four (impaired LV function) and three cases (normal LV function). P wave amplitude did not differ in the two groups (e.g., at month 12: impaired: 1.17 ± 0.42 mV; normal: 1.09 ± 0.49 mV). The atrial sensitivity was programmed in most patients to sensitive settings with no differences between the two groups (e.g., at month 12: impaired: 0.13 ± 0.06 mV; normal: 0.13 ± 0.05 m V). The diagnostic counters indicated nearly permanent atrial sensing (e.g., at month 12: impaired: 99.3 ± 2.2%; normal: 99.0 ± 1.0 mV). In conclusions, single lead VDD pacing restored AV synchronous ventricular pacing in patients with normal and with impaired LV function indicating that it could be an alternative to DDD pacemakers, but not to dual-chamber pacing.

Notes: SCHUCHERT, A., et al.: Effects of a Thin-Sized Lead Body of a Transvenous Single Coil Defibrillation Lead on ICD Implantation. In the interest of patients receiving implantable cardioverter defibrillators (ICDs), the clinical benefits of newer and thinner transvenous defibrillation leads have to be determined. The aims of this study were to evaluate the ICD procedure duration and the frequency of lead dislocation at the 3-month follow-up of a new defibrillation lead with a thin-sized lead body and its conventionalsized predecessor. The thin-sized single coil defibrillation lead (Kainox RV, Biotronik; lead body 6.7 Fr) was implanted in 61 patients and the conventional-sized defibrillation lead (SPS, Biotronik; lead body 7.8 Fr) in 60 patients. Both leads were connected to a left-sided, prepectorally implanted Phylax ICD (Biotronik) with active housing. The lead implantation time and total procedure duration were determined. Lead implantation time was defined as the time from lead insertion to the end of the pacing measurements. The total procedure duration spanned skin incision to closure. The incidence of lead repositioning during the lead implantation time and during ventricular fibrillation conversion testing was also assessed. The frequency of lead dislocations was recorded at the 3-month follow-up. Mean lead implantation time and total procedure duration of the thin-sized lead (23 ± 22 minutes 76 ± 37 minutes) were not statistically different from the time needed for the conventional-sized lead (22 ± 20 minutes 81 ± 34 minutes). The number of lead repositionings during the lead implantation time was similar (thin-sized lead: 1.4 ± 2.4; conventional-sized lead: 1.1 ± 1.9). An additional lead repositioning was not necessary during ventricular fibrillation conversion testing in 93.4% of the patients with thin-sized and in 94.4% with conventional-sized leads (not significant). At the 3-month follow-up, there were four (6.6%) lead dislocations in the thin-sized and four (6.7%) in the conventional-sized lead group. In conclusion, the downsized lead body of the new defibrillation lead influenced neither ICD procedure duration nor the incidence of lead dislocation during follow-up.

Notes: An ECG recording time of 24 hours has a low yield to detect atrial arrhythmias in patients after an acute ischemic stroke. The present study investigated whether a recording time of 72 instead of 24 hours detects paroxysmal atrial fibrillation in more patients. The study prospectively included 82 consecutive patients 2–3 weeks after an acute ischemic stroke. All patients had sinus rhythm in the resting ECGs and no history of atrial fibrillation or flutter. The frequency of atrial fibrillation was assessed after 24, 48, and 72 hours of ambulatory ECG monitoring. An ECG monitoring time of 72 hours documented paroxysmal atrial fibrillation in five (6%) patients. The episode of paroxysmal atrial fibrillation occurred in only one patient within 24 hours. The other patients had their first episode of atrial fibrillation between 24 and 48 hours (n = 2) and between 48 and 72 hours (n = 2). These five patients were older (age = 70 ± 5 years), whereas the mean age of the remaining patients was 59 ± 13 years. All five patients had cardiovascular disease in comparison to 36 of 77 patients and reported palpitations in comparison to 6 of 77 of the remaining patients. In conclusion, ambulatory ECG monitoring over 72 hours detected after the first recording day four of five patients in whom paroxysmal atrial fibrillation could be documented for the first time. The 72-hour recording time improved, compared to the 24-hour period, the detection of paroxysmal atrial fibrillation in patients after an ischemic stroke. It seems to be more efficient to perform prolonged ECG recording mainly in older patients with a cardiovascular disease and/or a history of palpitations.

Notes: During implantable cardioverter defibrillator (ICD) implantation of an active can ICD several defihrillations with 20 J and 34 J as well as 360 J externally were ineffective. The implant criteria were finally met with a second defibrillation lead and reversed polarity. A left-sided pneumothorax due to subclavian vein puncture was detected soon after ICD implantation. It is assumed that especially in the active can alignment the developing pneumothorax made defibrillation current flow more difficult. In case of several unsuccessful defibrillations during active can ICD implantation in which the subclavian vein was punctured, the possibility of a pneumothorax should be considered.

Notes: Background: The routine determination of heart rate variability (HRV) from surface ECGs is based on RR intervals because of the difficulty to precisely locate the P-wave fiducial point on surface ECG recordings. The aim of the study was to assess the changes of RR, PP, and PR intervals at rest and during moderate exercise. The time intervals were determined from atrial and ventricular pacemaker-mediated intracardiac electrograms. Methods: Ten patients in sinus rhythm with intrinsic AV node conduction who had received the dual-chamber pacemaker Logos (Biotronik) were included. High-resolution atrial and ventricular intracardiac electrograms were transmitted at rest in supine position and during walking to a portable external recorder. Recording sequences of 150 successive heart cycles were used for HRV analyses after computer-assisted triggering of P and R events. The HRV-index SDNN and power spectral densities for the low (LF; 0.04–0.15 Hz) as well as high (HF; 0.15–0.40 Hz) frequency bands were determined. Results: SDNN decreased from 26.0 ± 8.1 ms at rest to 18.3 ± 4.2 ms during exercise for the PP intervals (P 〈 0.05) and from 26.8 ± 8.1 to 18.4 ± 4.1 ms for the RR intervals (P 〈 0.05). The LF/HF ratio increased from 2.02 ± 1.3 to 4.5 ± 1.5 in the atrium (P 〈 0.05) and from 2.0 ± 1.2 to 5.2 ± 1.9 in the ventricle P 〈 0.05). Comparing atrial and ventricular HRV at both activity levels, no significant differences were observed for the power of LF and HF spectral components. Regarding the PR intervals SDNN, the total power and the LF/HF ratio did not significantly change during exercise. Conclusions: The described technique enabled to record intracardiac electrograms not only at rest, but also during moderate exercise and to use them for HRV evaluation. The changes of PP and RR, but not of the PR intervals, during exercise indicate that autonomic inputs to the sinus node and AV node are independent from each other. The ventricular HRV seems to derive mainly from variations of the sinus node pulse formation.

Notes: External electrocardiographic loop recording permits extended cardiac rhythm monitoring and ECG storage before and after device activation. The purpose of the study was to assess the diagnostic yield of external loop recorders in patients with more than two syncopal events within the last 6 months and a negative tilt table test. Twenty-four consecutive patients (51 ± 14 years, male n = 9) were enrolled with 3 ± 4 recurrent syncopal events within the last 6 months and no overt structural heart disease. The loop recorder CardioCall continuously records a two-channel ECG via skin electrodes. When activated, up to 4.5 minutes of the ECG preceding activation is stored. The time between tilt table testing and monitoring was 5 ± 4 weeks. The average monitoring period covered 50 ± 22 days. Recording was either unsuccessful or terminated prematurely in 5 patients. The reasons were skin irritation secondary to the electrodes in two patients, cable damage in one patient, and two patients inadvertently erased the stored data when replacing the batteries. Fourteen patients activated the loop recorder at least once. Symptoms leading to device activation were syncope (n = 1), dizziness (n = 11), feeling unwell (n = 7), palpitations (n = 5), headaches (n = 1), and chest pain (n = 1). The loop recorder documented sinus tachycardia during the syncopal event. Sinus tachycardia was also observed in 7 other patients, and atrial flutter in two patients. Eight patients had recurrent syncope with two patients experiencing syncope prior to the monitoring period, one syncope occurred in a patient who inadvertently erased the stored data, one event coincided with sinus tachycardia, and 4 (17%) patients had syncope during 15 ± 10 months after termination of loop monitoring. The external loop recorder was not very useful for arrhythmia detection in patients with syncopal events, no overt heart disease, and a negative tilt table test because the cardiac rhythm was stored in only 1 of 8 (13%) patients with recurrent syncope. Reasons for the low diagnostic yield of external loop recorders were infrequent syncopal events after the baseline evaluation, with rare events during the limited monitoring period in particular, and premature termination or unsuccessful recording in 21% of patients. (PACE 2003; 26:1837–1840)