Torsten Schwarz

Reduction of pacing output coupling capacitance for sensing the evoked response.

SPERZEL, J., et al.: Reduction of Pacing Output Coupling Capacitance for Sensing the Evoked Response. 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 μF 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 Ω, 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 μF 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 20–100Hz. 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.

The use of telescoping guide catheters for coronary sinus cannulation and sub-selecting tributaries in left ventricular lead placement

IntroductionFailure to enter the coronary sinus (CS) with a guiding catheter and entering its tributaries remains challenging in left ventricle (LV) pacing lead implants for cardiac resynchronization therapy (CRT). A dual telescoping catheter system (8F outer/6F inner) is designed to provide the ability to adjust the catheter curve size, shape and/or reach to the patients’ anatomy avoiding the need for catheter change.MethodsFive different designs for CS cannulation were randomly tested in 64 patients scheduled for CRT device implant.ResultsIn 33 consecutive patients three adaptable telescoping guiding catheter systems were tested per patient, the adaptable catheters had higher overall cannulation success rates (68, 63 and 62%) compared to the fixed shape catheter (46%) and an greater cannulation success rate when the CS location was not known (70, 53 and 72% vs 33% for the fixed shape). In a second group of 31 CRT patients the two telescoping catheters had similar high levels of success (71–80%), with or without using the inner catheter.ConclusionsThe telescopic system is adaptable to a wide range of anatomical variations in patients and can result in a higher CS cannulation success rate due to its adjustability in the RA in search for the CS ostium. On top of this the inner catheter allows for sub-selecting the CS tributaries.

Prospective Randomized Comparison of Two Defibrillation Safety Margins in Unipolar, Active Pectoral Defibrillator Therapy

CARLSSON, J., et al.: Prospective Randomized Comparison of Two Defibrillation Safety Margins in Unipolar, Active Pectoral Defibrillator Therapy. Various techniques are used to establish defibrillation efficacy and to evaluate defibrillation safety margins in patients with an ICD. In daily practice a safety margin of 10 J is generally accepted. However, this is based on old clinical data and there are no data on safety margins using current ICD technology with unipolar, active pectoral defibrillators. Therefore, a randomized study was performed to test if the likelihood of successful defibrillation at defibrillation energy requirement (DER) +5 J and +10 J is equivalent. Ninety‐six patients (86 men; age 61.0 ± 10.3 years; ejection fraction 0.341 ± 0.132 ; coronary artery disease [n = 65],dilated cardiomyopathy [n = 18], other [n = 13]) underwent implantation of an active pectoral ICD system with unidirectional current pathway and a truncated, fixed tilt biphasic shock waveform. The defibrillation energy requirement (DER) was determined with the use of a step‐down protocol (delivered energy 15, 10, 8, 6, 4, 3, 2 J). The patients were then randomized to three inductions of ventricular fibrillation at implantation and three at predischarge testing with shock strengths programmed to DER + 5 J at implantation and + 10 J at predischarge testing or vice versa. The mean DER in the total study population was7.88 ± 2.96 J. The number of defibrillation attempts was 288 for +5 J and 288 for +10 J. The rate of successful defibrillation was 94.1% (DER + 5 J) and 98.9% (DER + 10 J;P < 0.01for equivalence). Charge times for DER + 5 J were significantly shorter than for DER + 10 J (3.65 ± 1.14vs5.45 ± 1.47 s; P < 0.001). A defibrillation safety margin of DER + 5 J is associated with a defibrillation probability equal to the standard DER + 10 J. In patients in whom short charge times are critical for avoidance of syncope, a safety margin of DER + 5 J seems clinically safe for programming of the first shock energy. (PACE 2003; 26[Pt. I]:613–618)

Effects of electrode polarity on delibrillation thresholds in biphasic endocardial defibrillation

The defibrillation thresholds of both first-phase polarities of a biphasic waveform were tested using an endocardial defibrillation electrode system. Despite differences in defibrillation thresholds in the individual patient, both tested electrode polarities lead to a comparable overall defibrillation efficacy.

Left ventricular leads used in cardiac resynchronization therapy for heart failure patients

ZusammenfassungDie kardiale Resynchronisationstherapie (CRT) wurde für die Behandlung der Herzinsuffizienz in einem selektionierten Patientengut entwickelt, im Wesentlichen Patienten mit symptomatischer Herzinsuffizienz, einer linksventrikulären (LV) Dysfunktion und intraventrikulären Leitungsverzögerungen. Die CRT erfolgt mit Hilfe eines implantierten Impulsgebers und Elektroden im rechten Vorhof sowie im rechten und linken Ventrikel. Zu Beginn der Entwicklung der CRT wurden die linksventrikulären Elektroden epikardial über einen subxiphoidalen, thorakoskopischen oder größeren chirurgischen Zugang fixiert. Inzwischen stehen mehrere, gründlich erprobte, transvenöse LV-Elektroden zur Verfügung, die sicher in den Koronarvenensinus eingeführt und im venösen System platziert werden können. Akzeptable Schwellen für Pacing/Sensing und Komplikationsraten werden berichtet. Angesichts individueller Variationen in der kardialen und venösen Anatomie einschließlich enger Winkel im Venenverlauf, ist die Manövrierfähigkeit ein wichtiges Kriterium bei der Sondenwahl.SummaryCardiac resynchronization therapy (CRT) has been introduced as a treatment for selected heart failure patients, specifically those with symptomatic heart failure, left ventricular (LV) dysfunction, and intraventricular conduction delays. CRT is delivered by use of an implanted device and leads positioned in the right atrium, right ventricle, and left ventricle. In the early stages of CRT development, researchers affixed epicardial electrodes to the left ventricle by means of subxiphoid, thoracoscopic, or major surgical procedure. Currently there are a number of transvenous LV leads available that have undergone substantial evaluation. Reports indicate that such leads can be positioned safely by cannulating the coronary sinus and inserting the lead into the venous system. The leads are reported to have acceptable pacing/sensing thresholds and complication rates. Because of individual variations in the cardiac and venous anatomy, as well as sharp angulations in the venous system, maneuverability is an important consideration in lead selection.

Clinical Evaluation of a Prototype Passive Fixation Dual Chamber Single Pass Lead For Dual Chamber ICD Systems

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.