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Looks like VT But Isn't--successful ablation of a left free wall accessory pathway with Mahaim-like properties.

Osman F, Stafford PJ, Ng GA - Indian Pacing Electrophysiol J (2009)

Bottom Line: The pathway was shown to have long conduction times with no retrograde conduction, had an effective refractory period longer than the AV node and its conduction was only evident during antidromic AVRT.It also had a decremental antegrade property and was responsive to intravenous adenosine.These 'Mahaim-like' features are very unusual and rarely reported on the left side.

View Article: PubMed Central - PubMed

Affiliation: University Hospital Coventry, Department of Cardiology, Clifford Bridge Rd, Coventry CV22DX. faizel.osman@btinternet.com

ABSTRACT
It was long believed that Mahaim pathways represented nodo-fascicular or nodo-ventricular connections. However, this misconception was challenged when patients underwent surgical or catheter ablation of the AV node but remained pre-excited. Electrophysiology (EP) studies showed these pathways to be right sided decrementally conducting atrio-fascicular accessory pathways with the atrium forming a part of the antidromic tachycardia circuit. Mahaim pathways are usually reported to occur on the right side. We report a patient who presented with a broad complex tachycardia thought to be ventricular tachycardia; however during EP study this was shown to be an antidromic atrioventricular tachycardia utilising a left free wall pathway that demonstrated 'Mahaim-like' properties and was successfully ablated. The pathway was shown to have long conduction times with no retrograde conduction, had an effective refractory period longer than the AV node and its conduction was only evident during antidromic AVRT. It also had a decremental antegrade property and was responsive to intravenous adenosine. These 'Mahaim-like' features are very unusual and rarely reported on the left side.

No MeSH data available.


Related in: MedlinePlus

A late atrial premature stimulus delivered from CS 7-8 resets ventricular activation without fusion during tachycardia supporting the diagnosis of an antidromic AVRT
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F3a: A late atrial premature stimulus delivered from CS 7-8 resets ventricular activation without fusion during tachycardia supporting the diagnosis of an antidromic AVRT

Mentions: The patient was referred for electrophysiological assessment and treatment. Following counselling and informed consent, she was admitted for electrophysiology study which was carried out under local anaesthesia and intravenous sedation. Catheters were inserted via femoral venous access with a decapolar catheter (Irvine Biomedical Inc, California, USA) placed in the coronary sinus (CS) and quadripolar catheters (Bard Electrophysiology, MA, USA) placed at the right ventricular apex and His bundle position. Programmed stimulation demonstrated concentric, decremental retrograde and antegrade conduction. A spontaneous tachycardia was observed during the study with the same morphology as the clinical tachycardia (Figure 2a). The tachycardia cycle length was 447 ms and V:A time was 246 ms with earliest atrial activation at His bundle / proximal CS position (Figure 2b); there was no His bundle signal preceding ventricular signal during tachycardia. Earliest local ventricular activation during tachycardia was at the distal CS suggesting either a ventricular tachycardia with 1:1 retrograde atrial activation or an antidromic atrioventricular re-entry tachycardia involving a left free wall accessory pathway. A late atrial premature stimulus delivered from CS 7-8 reset ventricular activation without fusion during tachycardia (Figure 3a) supporting the diagnosis of an antidromic AVRT. Intravenous adenosine (6 mg) terminated the tachycardia with last activation in the atrium (Figure 3b) suggesting adenosine-sensitive property in the antegrade limb of the tachycardia (i.e. the accessory pathway). A trans-septal approach was taken to map the location of the accessory pathway during antidromic tachycardia with an irrigated tip deflectable ablation catheter (D curve Thermocool, Biosense-Webster, USA). The mitral annulus was mapped during tachycardia with earliest ventricular activation identified at the left free wall. Ablation caused termination of tachycardia which was still inducible after ablation cessation. A retrograde approach was then used with successful ablation achieved at a location with good unipolar signal (Figure 4a and4b). There was no recurrence of tachycardia following ablation and tested with programmed stimulation with intravenous isoproterenol infusion. The accessory pathway demonstrated unusual characteristics: it had no retrograde conduction, was slowly conducting with conduction only apparent in the antegrade direction in tachycardia, and had an effective refractory period longer than the AV node. These features are consistent with 'Mahaim-like' properties and have rarely been reported for left sided pathways.


Looks like VT But Isn't--successful ablation of a left free wall accessory pathway with Mahaim-like properties.

Osman F, Stafford PJ, Ng GA - Indian Pacing Electrophysiol J (2009)

A late atrial premature stimulus delivered from CS 7-8 resets ventricular activation without fusion during tachycardia supporting the diagnosis of an antidromic AVRT
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2655058&req=5

F3a: A late atrial premature stimulus delivered from CS 7-8 resets ventricular activation without fusion during tachycardia supporting the diagnosis of an antidromic AVRT
Mentions: The patient was referred for electrophysiological assessment and treatment. Following counselling and informed consent, she was admitted for electrophysiology study which was carried out under local anaesthesia and intravenous sedation. Catheters were inserted via femoral venous access with a decapolar catheter (Irvine Biomedical Inc, California, USA) placed in the coronary sinus (CS) and quadripolar catheters (Bard Electrophysiology, MA, USA) placed at the right ventricular apex and His bundle position. Programmed stimulation demonstrated concentric, decremental retrograde and antegrade conduction. A spontaneous tachycardia was observed during the study with the same morphology as the clinical tachycardia (Figure 2a). The tachycardia cycle length was 447 ms and V:A time was 246 ms with earliest atrial activation at His bundle / proximal CS position (Figure 2b); there was no His bundle signal preceding ventricular signal during tachycardia. Earliest local ventricular activation during tachycardia was at the distal CS suggesting either a ventricular tachycardia with 1:1 retrograde atrial activation or an antidromic atrioventricular re-entry tachycardia involving a left free wall accessory pathway. A late atrial premature stimulus delivered from CS 7-8 reset ventricular activation without fusion during tachycardia (Figure 3a) supporting the diagnosis of an antidromic AVRT. Intravenous adenosine (6 mg) terminated the tachycardia with last activation in the atrium (Figure 3b) suggesting adenosine-sensitive property in the antegrade limb of the tachycardia (i.e. the accessory pathway). A trans-septal approach was taken to map the location of the accessory pathway during antidromic tachycardia with an irrigated tip deflectable ablation catheter (D curve Thermocool, Biosense-Webster, USA). The mitral annulus was mapped during tachycardia with earliest ventricular activation identified at the left free wall. Ablation caused termination of tachycardia which was still inducible after ablation cessation. A retrograde approach was then used with successful ablation achieved at a location with good unipolar signal (Figure 4a and4b). There was no recurrence of tachycardia following ablation and tested with programmed stimulation with intravenous isoproterenol infusion. The accessory pathway demonstrated unusual characteristics: it had no retrograde conduction, was slowly conducting with conduction only apparent in the antegrade direction in tachycardia, and had an effective refractory period longer than the AV node. These features are consistent with 'Mahaim-like' properties and have rarely been reported for left sided pathways.

Bottom Line: The pathway was shown to have long conduction times with no retrograde conduction, had an effective refractory period longer than the AV node and its conduction was only evident during antidromic AVRT.It also had a decremental antegrade property and was responsive to intravenous adenosine.These 'Mahaim-like' features are very unusual and rarely reported on the left side.

View Article: PubMed Central - PubMed

Affiliation: University Hospital Coventry, Department of Cardiology, Clifford Bridge Rd, Coventry CV22DX. faizel.osman@btinternet.com

ABSTRACT
It was long believed that Mahaim pathways represented nodo-fascicular or nodo-ventricular connections. However, this misconception was challenged when patients underwent surgical or catheter ablation of the AV node but remained pre-excited. Electrophysiology (EP) studies showed these pathways to be right sided decrementally conducting atrio-fascicular accessory pathways with the atrium forming a part of the antidromic tachycardia circuit. Mahaim pathways are usually reported to occur on the right side. We report a patient who presented with a broad complex tachycardia thought to be ventricular tachycardia; however during EP study this was shown to be an antidromic atrioventricular tachycardia utilising a left free wall pathway that demonstrated 'Mahaim-like' properties and was successfully ablated. The pathway was shown to have long conduction times with no retrograde conduction, had an effective refractory period longer than the AV node and its conduction was only evident during antidromic AVRT. It also had a decremental antegrade property and was responsive to intravenous adenosine. These 'Mahaim-like' features are very unusual and rarely reported on the left side.

No MeSH data available.


Related in: MedlinePlus