Case 42 Pacing Induced Atrial Arrhythmia

Patient: 45-year-old female with ischemic heart disease, left ventricular ejection fraction 0.26, congestive heart failure, and left bundle branch block (QRS width 122 ms). History of atrial tachyarrhythmia.

Index arrhythmia: sustained monomorphic ventricular tachycardia, cycle length 420 ms.

Complaint: hospital admission due to recurrent ventricular tachyarrhythmias.

Figure 6.42a.

ICD pulse generator: Jewel AF 7250 (Medtronic Inc, Minneapolis, MN, USA).

Tachycardia settings

Detection: VF = 300 ms; VT = 440 ms. Discrimination: stability = 40 ms; PR Logic ON.

Therapy: VF = shock; VT = antitachycardia pacing and cardioversion; AT = antitachycardia pacing.

Bradycardia settings Mode: DDD 76-120 bpm. Modeswitch = ON. AV = 150 ms.

Electrogram interpretation

Figure 6.42b. From top to bottom: wide-band electrogram and marker channel. Markers: AP = atrial pacing; AR = atrial refractory sense; AS = atrial sensing; FS = fibrillation sensing; TS = tachycardia sensing; VP = ventricular pace; VS = ventricular sense.

1. Presence of tachyarrhythmia?: Yes.

2. Assessment of the onset of the tachyarrhythmia triggering the device: at the left site of the electrogram, the atrial activity on the marker channel shows an atrial rhythm with an atrial cycle length «440 ms. The atrioventricular conduction pattern during this atrial rhythm shows a Wenckbach pattern. An irregularity in the atrial sequence is observed, coinciding with a ventricular premature beat (arrow). This initiates a fast tachyarrhythmia.

3. Comparison between atrial and ventricular rate: rate branch VV < AA.

4. Description of the atrial rhythm: the atrial activity on the marker channel shows an atrial rhythm with an atrial cycle length «440 ms. The atrial activity on the far-field electrogram is by small deflections with a consistent morphology. The atrial rhythm can either be atrial tachycardia or sinus tachycardia. Regularity is resumed after the arrow, offering an argument to believe it was cross-sensing of the VPB.

5. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular activity is consistent in the electrogram. The ventricular rhythm has a cycle length of «270 ms, with a stability of «10 ms. During the stable ventricular rhythm, the marker channel demonstrates absence of a consistent atrioventricular relationship. Additional information is provided by the marker channel after device therapy as no electrogram is available after therapy (see figure 6.42c). The marker channel demonstrates an atrial paced rhythm of 800 ms.

Diagnosis: double tachycardia, the patient has initially an atrial tachycardia with Wenckebach atrioventricular conduction pattern. During this atrial tachycardia, a ventricular premature beat induces a fast ventricular tachycardia. Pacing was atrial synchronous, in the ventricle.

Action: adjustment of antiarrhythmic drug treatment.

174 6. Clinical Case Studies Marker channel after therapy

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