Biomedical subjects

Roger Willems

Publications and source records attributed to Roger Willems.

4 recordsLinked to original sources

PubMed2006

Acute performance evaluation of a new ventricular automatic capture algorithm.

AIMS: This study evaluated the acute clinical performance of a new ventricular automatic capture algorithm developed to work with all lead types and pacing vectors. METHODS AND RESULTS: During regular pacemaker implant or replacement, AutoThreshold and manual threshold tests were performed in ventricular unipolar (UP) and bipolar (BP, if applicable) pacing using a customized external prototype INSIGNIA pacemaker. The success rate and accuracy of two different modes (commanded and ambulatory) of the automatic capture algorithm were used to evaluate the performance. Loss-of-capture events (two consecutive non-captured beats without backup pacing) were used to assess safety. Data of 53 patients (33 DDD/20 VVI) from four medical centres were analysed. Tested leads included 43 BP and 10 UP from nine manufacturers, and seven had electrodes with low polarization. The rate of successful commanded and ambulatory AutoThreshold tests was 96 and 94%, respectively, with an average absolute threshold difference compared with manual threshold of < 0.1 V at 0.4 ms (commanded 0.07 +/- 0.07 V and ambulatory 0.08 +/- 0.07 V). There was no significant difference in performance between UP/BP pacing, polarization, and lead type. No loss-of-capture event was observed. CONCLUSION: When successful, the ventricular automatic capture algorithm accurately determined pacing thresholds in either a UP or BP pacing configuration among all leads tested.

Adult↗

PubMed2006

Feasibility of automated detection of advanced sleep disordered breathing utilizing an implantable pacemaker ventilation sensor.

OBJECTIVES: This study tested the feasibility of automatically detecting advanced sleep disordered breathing (SDB) from a pacemaker trans-thoracic impedance sensor. BACKGROUND: SDB is prevalent yet under-diagnosed in patients with cardiovascular disease. The potential for automated detection of SDB in patients receiving pacemakers with respiration sensors has not been fully explored. We hypothesized that the trans-thoracic impedance sensor could be utilized for automatic detection of advanced SDB. METHODS: Patients underwent overnight polysomnography (PSG). The pacemaker trans-thoracic impedance signal was simultaneously recorded and time synchronized with the polysomnograph. Cardiovascular health variables were abstracted from medical records. Apnea was defined as cessation of inspiratory airflow lasting 10 seconds or longer. Hypopnea was defined as a reduction of tidal volume of at least 30% from baseline tidal volume, lasting 10 seconds or more. A computer algorithm (PM-A) was developed to automatically detect SDB from the pacemaker impedance sensor data. The performance of automated SDB detection was compared against PSG. RESULTS: Sixty patients (aged 69 +/- 12 years, 45 males) were studied. Advanced SDB (moderate or severe) was diagnosed in 40 patients. Severe SDB (apnea-hypopnea index [AHI]> or = 30) was diagnosed in 32 patients (53%), but only 5 patients had prior diagnosis of the disease. Moderate SDB (30 > AHI > 15) was diagnosed in 8 patients of whom only two were previously diagnosed. Cardiovascular health variables did not predict the presence of advanced SDB. PM-A derived AHI correlated with that of the PSG (r = 0.80, P < 0.01). The algorithm identified patients with advanced SDB with 82% sensitivity and 88% specificity. CONCLUSIONS: It is feasible to automatically measure SDB severity using a pacemaker trans-thoracic impedance sensor. Advanced SDB was frequently undiagnosed in this cohort of pacemaker patients.

Aged↗

PubMed2003

Multisite atrial pacing for atrial fibrillation prevention: where to go from here?

Atrial fibrillation (AF) is a common arrhythmia associated with stroke, increased mortality and with a negative impact on quality of life. Pharmacologic treatments for AF have not provided long-term relief from arrhythmia recurrence. Multi-site atrial pacing was introduced by Daubert and colleagues about 10 years ago for the treatment of severe atrial conduction delays in patients with sick sinus syndrome. They found that this type of atrial stimulation reduced or prevented AF. Multi-site atrial pacing results in reduction of intra-atrial and interatrial conduction differences and diminishes heterogeneity of refractoriness, i.e. atrial resynchronization. Acute electrophysiological studies have shown that biatrial stimulation reduced AF inducibility. The Dutch Dual-site Right Atrial Pacing for Prevention of Atrial Fibrillation study was a prospective randomized crossover trial comparing the recurrences of AF in dual-site right atrial and single-site high right atrial pacing in patients with symptomatic medically refractory AF, without or with minimal structural heart disease. Patients were randomized to initial dual-site pacing (Group I n = 18) or initial single-site (Group II n = 22) pacing. After 6 months or after a study endpoint was reached patients were crossed over to the other pacing modality.Although, the arrhythmia free intervals were longer for dual-site pacing during both treatments periods (Group I 162 +/- 12 and Group II 114 +/- 15 days) compared to single-site pacing (Group I 143 +/- 16 and Group II 97 +/- 10 days) the difference was not statistically significant (p = 0.061). However, the sequence of the randomized treatment periods had a significant effect on outcome (p < 0.02). Event free intervals (AF > 48 hours requiring electrical cardioversion) were longer during dual-site pacing in both groups compared to single-site stimulation but the difference was statistically not significant (p = 0.055) because of treatment interaction (P < 0.05). To establish the clinical benefits of multi-site pacing for the treatment of patients with medically refractory symptomatic AF, additional prospective randomized studies are needed. Trials with a parallel design are necessary to avoid carry-over effects of different stimulation protocols.

Atrial Fibrillation↗

PubMed2003

Comparison of impedance minute ventilation and direct measured minute ventilation in a rate adaptive pacemaker.

Respiration rate (RR) and minute ventilation (MV) provide important clinical information on the state of the patient. This study evaluated the accuracy of determining these using a pacemaker impedance sensor. In 20 patients who were previously implanted with a Guidant PULSAR MAX group of pacemakers, the telemetered impedance sensor waveform was recorded simultaneously with direct volume respiration waveforms as measured by a pneumatometer. Patients underwent 30 minutes of breathing tests while supine and standing, and a 10-minute ergonometer bicycle exercise test at a workload of 50 W. Breathing tests included regular and rapid-shallow breathing sequences. RR was determined by a computerized algorithm, from impedance and respiration signals. The mean RR by impedance was 21.3 +/- 7.7 breaths/min, by direct volume was 21.1 +/- 7.6 breaths/min, range 7-66, the mean difference of RR measured by the impedance sensor, as compared with the true measurement, being 0.2 +/- 2.1 breaths/min. During the entire exercise, the mean correlation coefficient between impedance (iMV) and direct measured MV was 0.96 +/- 0.03, slope 0.13 +/- 0.05 L/Omega and range 0.07-0.26 L/Omega. Bland-Altman limits of agreement were +/- 4.6 L/min for MV versus iMV with each patient calibrated separately. The correlation coefficient for iMV versus MV over the entire 10 minutes of exercise, including the initial 4 minutes of exercise, was 0.99. The transthoracic impedance sensor of an implanted pacemaker can accurately detect respiration parameters. There was a large variation between subjects in the iMV versus MV slope during a bicycle exercise test, whereas for each subject, the slope was stable during submaximal bicycle exercise.

Adult↗