Biomedical subjects

Fredrik Gadler

Publications and source records attributed to Fredrik Gadler.

6 recordsLinked to original sources

PubMed2004

Acute comparative effect of right and left ventricular pacing in patients with permanent atrial fibrillation.

We tested the hypothesis that left ventricular (LV) pacing is superior to right ventricular (RV) apical pacing in patients undergoing atrioventricular (AV) junction ablation and pacing for permanent atrial fibrillation. The potential benefit of LV over RV pacing needs to be evaluated without the confounding effect of other variables that can influence cardiac performance. An acute intrapatient comparison of the QRS width and echocardiographic parameters between RV versus LV pacing was performed within 24 h after ablation in 44 patients. Both modes of pacing were also compared with pre-implantation values. Compared with RV pacing, LV pacing caused a 5.7% increase in the ejection fraction (EF) and a 16.7% decrease in the mitral regurgitation (MR) score; the QRS width was 4.8% shorter with LV pacing. Similar results were observed in patients with or without systolic dysfunction and/or native left bundle branch block, except for a greater improvement in MR in the latter group. Compared with pre-ablation measures, the EF increased by 11.2% and 17.6% with RV and LV pacing, respectively; the MR score decreased by 0% and 16.7%; and the diastolic filling time increased by 12.7% and 15.6%.Rhythm regularization achieved with AV junction ablation improved EF with both RV and LV pacing; LV pacing provided an additional modest but favorable hemodynamic effect, as reflected by a further increase of EF and reduction of MR. The effect seems to be equal in patients with both depressed and preserved systolic functions and in those with and without native left bundle branch block.

Aged↗

PubMed2004

Optimization of cardiac resynchronization therapy by continuous hemodynamic monitoring:.

We report the case of a 55-year-old male patient with severe congestive heart failure in whom both a hemodynamic monitor and a biventricular pacemaker were implanted. The potential usefulness of the monitor to optimize AV delay and heart rate was prospectively evaluated. The AV delay associated with the lowest filling pressures recorded by the monitor was similar to the optimal AV delay as determined by standard echocardiography. Heart rates >70 beats/min acutely improved hemodynamics but were not tolerated when programmed chronically. This case illustrates that continuous hemodynamic monitoring may offer a useful tool for device tuning and treatment monitoring in cardiac resynchronization therapy.

Blood Pressure Determination↗

PubMed2003

Long-term improvements in quality of life by biventricular pacing in patients with chronic heart failure: results from the Multisite Stimulation in Cardiomyopathy study (MUSTIC).

To assess the impact of biventricular pacing on quality of life over 12 months of follow-up, 76 patients in the MUSTIC trial were evaluated by 2 instruments: The Minnesota Living with Heart Failure Questionnaire and the Karolinska Quality of Life Questionnaire. MUSTIC is a randomized, controlled study to evaluate the effects of biventricular pacing in patients in New York Heart Association class III heart failure with intraventricular conduction delay. Following a single, blind, crossover comparison of 3 months of biventricular pacing to inactive pacing (sinus rhythm group) or ventricular-inhibited pacing (atrial fibrillation group), 85% of patients preferred and were programmed to biventricular pacing and were followed for 12 months. In parallel with clinical improvements, substantial benefits in quality of life for most broad domains of quality of life and cardiovascular symptoms were found during biventricular pacing already within the crossover phase with a maintained benefit over the 12-month follow-up. Biventricular pacing improved quality of life in patients with heart failure and intraventricular conduction delays. The benefits were sustained over 12 months of follow-up.

Aged↗

PubMed2003

Clinical experience with an automatic threshold tracking algorithm study.

The automatic threshold tracking pacing system algorithm developed by St. Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response (ER) following each pacemaker stimulus. The present automatic threshold tracking function requires a bipolar ventricular lead with low polarization. The aim of this study was to evaluate a new algorithm developed to use with unipolar leads with different levels of polarization. An external pacemaker with the ability to sense intrinsic R waves and measure ER signals, as well as deliver stimulus, was used. An algorithm for detecting the true ER in a unipolar sensing configuration (tip-case) was developed. Based on the assumption that the true evoked R wave amplitude is independent of the stimulation amplitude, the algorithm calculates and subtracts the polarization present at any pacing stimulus from the measured ER. The resulting signal is analyzed to verify capture. This study comprises 35 patients of which 26 were new implants and 9 had chronic leads. The automatic threshold-tracking algorithm was calibrated for each patient and pacing was performed at different pulse amplitudes and pulse duration. Capture was verified for each paced beat. The recordings were stored for later comparison with the tape-recorded intracardiac heart signals. The new algorithm correctly verified capture or loss of capture for every single analyzed beat at the different pacing outputs in every individual patient. The results from this initial study suggests that the new ER detection principle will allow automatic threshold tracking to be used not only with low polarization bipolar leads but with most leads.

Aged↗

PubMed2002

Transient proarrhythmic state following atrioventricular junction radiofrequency ablation: pathophysiologic mechanisms and recommendations for management.

The induction of complete heart block by radiofrequency ablation of the atrioventricular junction combined with pacemaker implantation has become an established therapy for rate control in patients with atrial fibrillation who are unresponsive to drugs. Reports of ventricular arrhythmias and sudden death after ablation have, however, raised concerns about safety. Ventricular arrhythmias are usually polymorphic and related to a phase of electrical instability due to an initial prolongation and then slow adaptation of repolarization caused by the change in heart rate and activation sequence. Structural heart disease, and other factors that predispose for the acquired long QT syndrome, seem to add to the risk. Ventricular activation and repolarization stabilize during the first week after the procedure. Routine pacing at 80 beats per minute during this phase is recommended, as well as in hospital monitoring for at least 48 hours. Patients with high-risk features for arrhythmias, such as congestive heart failure or impaired left ventricular function, may require pacing at higher rates. Adjustment of the pacing rate-although rarely below 70 beats per minute-is usually undertaken after a week in most patients, preferably after an electrocardiographic evaluation for repolarization abnormalities at the lower rate.

Atrioventricular Node↗

PubMed2002

Transient proarrhythmic state following atrioventricular junctional radiofrequency ablation.

This study was designed to prospectively assess ventricular de- and repolarization by the QRS, QT, and JT intervals, and their dispersion in the 12-lead ECG during right ventricular pacing at 60, 70, and 80 beats/min during the first month after AV junctional RF ablation. Previous reports have found early polymorphic ventricular arrhythmia after RF AV junctional ablation. Our hypothesis was that there is a proarrhythmic state following this procedure, which depends on the paced rate and time after ablation. The analysis of the immediate changes was based on 17 patients (10 men) with a mean age of 64 years (SD 14) (range 38-82 years). A 12-lead ECG was recorded during right ventricular pacing at 60, 70, and 80 beats/min within 24 hours (day 1), between 24 and 48 hours (day 2), and 1 week after ablation (day 7). For analysis of changes beyond 1 week, 13 additional patients with a mean age of 73 years (SD 8) (range 62-90 years) were analyzed on days 1, 7, and 30. All intervals were measured with a digitizing table. The mean QRS duration shortened by 2.4% at 60 beats/min (P <0.01), and the mean QT and JT intervals shortened by 5-7% between days 1 and 7 (P < 0.001). The mean QT was 9% shorter and the mean JT interval was 13% shorter at 80 compared to 60 beats/min on day 1 (P < 0.001). QT dispersion was reduced by 13% when the stimulation rate was increasedfrom 60 to 80 beats/min on day 1 (P < 0.05). There were no significant changes beyond the first week. The study results point to the induction of a proarrhythmic state immediately after AV junctional RF ablation resolving during the first week. Repolarization shortened gradually between 80 and 60 beats/min to an extent that is suggestive of a clinically important antiarrhythmic effect at the higher rate, which was supported also by clinical experience.

Action Potentials↗