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Biomedical subjects

Frank A Bracke

Publications and source records attributed to Frank A Bracke.

11 recordsLinked to original sources
PubMed2006

Paradoxical atrial undersensing: noise rate reversion or amplifier ringing?

Atrial tachy-arrhythmias may give rise to mode switching or noise rate reversion in dual-chamber pacemakers. In case of high amplitude of the atrial electrogram during tachycardia, a paradoxical behavior of atrial sensitivity programming can be observed. Two patients with implanted dual-chamber pacemakers showed intermittent and complete loss of atrial sensing during atrial tachycardia during device programming to a higher atrial sensitivity setting. This phenomenon is caused by amplifier ringing and can be considered as a state of amplifier saturation, which disables atrial sensing in spite of the high amplitude of the atrial signal. In patients with high amplitude of the atrial electrogram during atrial tachycardia, a paradoxical behavior of sensitivity programming resulting in atrial undersensing can be observed.

Adult↗
PubMed2006

Correlation of echo-Doppler optimization of atrioventricular delay in cardiac resynchronization therapy with invasive hemodynamics in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

This study investigated the optimal echocardiographic indexes to determine the most hemodynamically appropriate atrioventricular (AV) delay in cardiac resynchronization therapy (CRT) for heart failure. Doppler echocardiographic optimization of AV delay in CRT has not been correlated with invasive hemodynamic indexes. In 30 patients who underwent CRT, invasive left ventricular (LV) pressure measurements with a sensor-tipped pressure guidewire and Doppler echocardiographic examination were performed <24 hours after pacemaker implantation. Invasively, the optimal sensed AV delay was determined by LV dP/dt(max). The Doppler echocardiographic methods evaluated were the velocity-time integral (VTI) of the transmitral flow (EA VTI), diastolic filling time (EA duration), the VTI of the LV outflow tract or aorta (LV VTI), and Ritter's formula. Biventricular pacing with optimized interventricular and AV delay increased LV dP/dt(max) from 777 +/- 149 to 1,010 +/- 163 dynes/s (p<0.0001). The optimal AV delay with the EA VTI method was concordant with LV dP/dt(max) in 29 of 30 patients (r = 0.96), with EA duration in 20 of 30 patients (r= 0.83), with LV VTI in 13 patients (r = 0.54), and with Ritter's formula in none of the patients (r = 0.35). In conclusion, to obtain the optimal acute hemodynamic benefit of CRT, Doppler echocardiography is a reliable tool to optimize the AV delay compared with the invasive LV dP/dt(max). The measurement of the maximal VTI of mitral inflow is the most accurate method.

Aged↗
PubMed2006

Preservation of ventricular capture by anodal stimulation after dislodgment of an epicardial electrode.

A 58-year-old man had a bipolar epicardial left ventricular (LV) implanted for cardiac resynchronization therapy after a failed transvenous approach. The system was programmed in an LV tip-right ventricular coil configuration, but during follow-up loss of LV capture with recurrence of symptoms occurred. Changing to an LV tip-LV ring configuration restored LV pacing through anodal capture. Loss of cathodal capture was caused by dislodgment of the cathodal electrode due to a broken fixation suture. Anodal capture was used to reinstall resynchronization therapy, which resulted in clinical improvement. There were no adverse effects from anodal stimulation in a follow-up period of 6 months.

Bundle-Branch Block↗
PubMed2005

The hemodynamic effect of intrinsic conduction during left ventricular pacing as compared to biventricular pacing.

OBJECTIVES: We sought to investigate the effect of intrinsic conduction over the right bundle on the maximum rate of left ventricular pressure rise (LVdP/dt(max)) during left ventricular (LV) pacing compared to biventricular (BiV) pacing. BACKGROUND: Simultaneous BiV pacing and LV pacing both improve LV function in patients with heart failure and LV asynchrony. We studied the hemodynamic effect of intrinsic conduction leading to ventricular fusion during LV pacing. METHODS: In 34 patients with New York Heart Association functional class III or IV, sinus rhythm with normal atrioventricular (AV) conduction, left bundle branch block, QRS >130 ms, and optimal medical therapy, LVdP/dt(max) was measured invasively during LV and simultaneous BiV pacing. The AV interval was varied in four steps starting (AV1) with an AV interval 40 ms shorter than the intrinsic PQ time and decreased with 25% for each step. RESULTS: At AV1, LVdP/dt(max) was 996 +/- 194 mm Hg/s for LV pacing and 960 +/- 200 mm Hg/s for BiV pacing (p = 0.0009), with all patients showing ventricular fusion during LV pacing. At AV2, 21 patients had ventricular fusion with a LVdP/dt(max) of 983 +/- 213 mm Hg/s and 957 +/- 202 mm Hg/s for LV and BiV pacing, respectively. In the remaining 13 patients without fusion these values were 919 +/- 164 mm Hg/s and 957 +/- 174 mm Hg/s, respectively. The difference between LV and BiV at AV2 is significantly higher when fusion is present (p = 0.01). CONCLUSIONS: The LVdP/dt(max) is higher in LV than in BiV pacing provided that LV pacing is associated with ventricular fusion caused by intrinsic activation.

Aged↗
PubMed2005

The effect of anodal stimulation on V-V timing at varying V-V intervals.

We studied the effect of anodal capture at the ring electrode of the right ventricular (RV) lead on interventricular (V-V) timing during biventricular (BiV) pacing, in which left ventricular (LV) pacing was preceding RV pacing. The V-V interval was programmed from 80 to 4 ms (LV first) in the LV unipolar (LV tip--generator can) followed by the LV tip-RV ring pacing configuration. In the LV unipolar configuration, V-V programming leads to a continuous change in morphology of the QRS complex according to a change in collision of both activation fronts. When using the LV tip-RV ring configuration with anodal capture at the RV ring electrode no change in QRS morphology was recorded varying the V-V interval from 80 to 60 and 40 ms. However, at V-V intervals between 20 and 4 ms a change in morphology of the QRS complex was recorded, which was due to additional cathodal stimulation of the RV tip electrode during RV stimulation.

Aged↗
PubMed2004

Effect of optimizing the VV interval on left ventricular contractility in cardiac resynchronization therapy.

Simultaneous biventricular pacing improves left ventricular (LV) function in patients with heart failure and LV asynchrony. Proper timing of the interventricular pacing interval (VV interval) may further optimize LV function. We investigated the acute hemodynamic response of changing the VV interval using maximum LV dP/dt (LV dP/dt(max)) as a parameter for LV function. A biventricular pacemaker was implanted in 53 patients with severely impaired LV function, New York Heart Association class III and IV heart failure, left bundle branch block, LV asynchrony, and a QRS interval >150 ms. Optimization of the atrioventricular and VV intervals was based on measurement of LV dP/dt(max) by a 0.014-in sensor-tipped pressure guidewire. Measurement of LV dP/dt(max) was obtained without complications in all patients. In patients in sinus rhythm with ischemic cardiomyopathy or idiopathic dilated cardiomyopathy, mean improvements by simultaneous biventricular pacing were 17% and 18%, respectively. Patients in atrial fibrillation showed an improvement of 21%. Optimizing the VV interval resulted in further absolute increases of 8%, 7%, and 3%, respectively, in dP/dt(max) in the 3 groups. Maximum dP/dt was achieved with LV pacing first in 44 patients, simultaneous right and left ventricular pacing in 6 patients, and right ventricular pacing first in 3 patients. The mean optimal VV intervals were 37 +/- 32 ms in the atrial fibrillation group, 28 +/- 30 ms in the idiopathic dilated cardiomyopathy group, and 52 +/- 31 ms in the ischemic cardiomyopathy group. Optimization of the VV interval significantly increased LV dP/dt(max) compared with simultaneous biventricular pacing, and such optimization could be easily, accurately, and reliably evaluated by a 0.014-in sensor-tipped pressure guidewire.

Aged↗
PubMed2003

Successful implantation of a coronary sinus lead after stenting of a coronary vein stenosis.

Dislodgment of the coronary sinus lead was observed in a 79-year-old patient 8 months after implantation of a biventricular pacing system. A severe stenosis in the posterolateral branch, in which the lead was previously positioned, prohibited reinsertion of the lead. Because no other branches with adequate anatomy for lead insertion were available in the targeted area, the stenosis was dilated and stented. Subsequently, the left ventricular lead could be reimplanted in the same vessel.

Aged↗
PubMed2003

Implantation of a biventricular pacing system in a patient with a coronary sinus not communicating with the right atrium.

Intubation of the coronary sinus failed during implantation of a biventricular pacing system. An angiogram of the left coronary artery showed in the venous phase a coronary sinus not communicating with the right atrium. The coronary sinus was draining into a persistent left superior vena cava communicating with the left subclavian vein. The coronary sinus lead was successfully implanted through the persistent left superior vena cava, whereas the atrial and ventricular leads were implanted through the right superior vena cava in a conventional way.

Aged↗
PubMed2002

Cardiac stimulation caused by biogalvanic current during pacemaker implantation.

After lead positioning during implantation of a biventricular pacing system intermittent ventricular simulation was observed. There was no pacemaker connected to any of the leads, but ventricular capture could be provoked by an intermittent contact between the lead stylet, which was still partially inserted, and a self-retaining retractor. The same phenomenon was observed from the atrial lead.

Bundle-Branch Block↗