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A fortuitous syncope. The pitfalls of integrated bipolar defibrillator leads.

Salukhe TV, Wright I, Wright M, Kanagaratnam P, O'Neill MD - Indian Pacing Electrophysiol J (2008)

Bottom Line: Current literature is dominated by reports of diaphragmatic muscle as the source of such far-field oversensing.Those reporting pectoral muscle sources were invariably due to unipolar sensing circuits, incorrect DF-1 connections or inappropriate programming.We report an interesting case of pectoral muscle myopotential oversensing causing inhibition of bradycardia pacing leading to presyncope and syncope.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiac Electrophysiology, St Mary's Hospital and Imperial College, London, UK. salukhe@aol.com

ABSTRACT
Myopotential oversensing in implantable defibrillators causing inhibition of pacing and inappropriate therapies is well described. Current literature is dominated by reports of diaphragmatic muscle as the source of such far-field oversensing. Those reporting pectoral muscle sources were invariably due to unipolar sensing circuits, incorrect DF-1 connections or inappropriate programming. We report an interesting case of pectoral muscle myopotential oversensing causing inhibition of bradycardia pacing leading to presyncope and syncope.

No MeSH data available.


Related in: MedlinePlus

Automatic gain control (red line). See text for explanation. Blanking period (BP), ventricular sensed event (VS), ventricular paced event (VP), ventricular fibrillation detection (VF)
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Figure 2: Automatic gain control (red line). See text for explanation. Blanking period (BP), ventricular sensed event (VS), ventricular paced event (VP), ventricular fibrillation detection (VF)

Mentions: This patient only became symptomatic when rendered pacing dependant after AV node ablation when upper body muscular movement caused pacing inhibition through myopotential oversensing. Fortunately, this consistently caused dizziness or syncope which stopped physical activity thus terminating myopotential oversensing. As a result, therapies were always diverted and pacing resumed. It is therefore curious that no inappropriate therapies were delivered prior to AV node ablation. This may simply be explained by a dynamic ventricular sensing threshold facility available in most defibrillators, in this case, automatic gain control (see Figure 2). Following a sensed ventricular event, there is a blanking period before the initial sensitivity is set to 75% of the sensed R wave amplitude. Thereafter, the sensitivity gradually increases to a set maximum (typically ~ 0.18 mV). After a paced ventricular event, the initial sensitivity is set higher (nominally ~ 3.5 mV). The subsequent rate of sensitivity increase is faster and reaches a maximum earlier. Thus, the mechanism of more frequent myopotential oversensing after becoming pacing dependant becomes clear. This phenomenon is more easily appreciated in a different patient with an implanted defibrillator in Figure 3.


A fortuitous syncope. The pitfalls of integrated bipolar defibrillator leads.

Salukhe TV, Wright I, Wright M, Kanagaratnam P, O'Neill MD - Indian Pacing Electrophysiol J (2008)

Automatic gain control (red line). See text for explanation. Blanking period (BP), ventricular sensed event (VS), ventricular paced event (VP), ventricular fibrillation detection (VF)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2572022&req=5

Figure 2: Automatic gain control (red line). See text for explanation. Blanking period (BP), ventricular sensed event (VS), ventricular paced event (VP), ventricular fibrillation detection (VF)
Mentions: This patient only became symptomatic when rendered pacing dependant after AV node ablation when upper body muscular movement caused pacing inhibition through myopotential oversensing. Fortunately, this consistently caused dizziness or syncope which stopped physical activity thus terminating myopotential oversensing. As a result, therapies were always diverted and pacing resumed. It is therefore curious that no inappropriate therapies were delivered prior to AV node ablation. This may simply be explained by a dynamic ventricular sensing threshold facility available in most defibrillators, in this case, automatic gain control (see Figure 2). Following a sensed ventricular event, there is a blanking period before the initial sensitivity is set to 75% of the sensed R wave amplitude. Thereafter, the sensitivity gradually increases to a set maximum (typically ~ 0.18 mV). After a paced ventricular event, the initial sensitivity is set higher (nominally ~ 3.5 mV). The subsequent rate of sensitivity increase is faster and reaches a maximum earlier. Thus, the mechanism of more frequent myopotential oversensing after becoming pacing dependant becomes clear. This phenomenon is more easily appreciated in a different patient with an implanted defibrillator in Figure 3.

Bottom Line: Current literature is dominated by reports of diaphragmatic muscle as the source of such far-field oversensing.Those reporting pectoral muscle sources were invariably due to unipolar sensing circuits, incorrect DF-1 connections or inappropriate programming.We report an interesting case of pectoral muscle myopotential oversensing causing inhibition of bradycardia pacing leading to presyncope and syncope.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiac Electrophysiology, St Mary's Hospital and Imperial College, London, UK. salukhe@aol.com

ABSTRACT
Myopotential oversensing in implantable defibrillators causing inhibition of pacing and inappropriate therapies is well described. Current literature is dominated by reports of diaphragmatic muscle as the source of such far-field oversensing. Those reporting pectoral muscle sources were invariably due to unipolar sensing circuits, incorrect DF-1 connections or inappropriate programming. We report an interesting case of pectoral muscle myopotential oversensing causing inhibition of bradycardia pacing leading to presyncope and syncope.

No MeSH data available.


Related in: MedlinePlus