Case 23 Ineffective Antitachycardia Pacing

Patient: 59-year-old male with idiopathic dilated cardiomyopathy, left ventricular ejection fraction of 28%, congestive heart failure, and incomplete left bundle branch block (QRS width 100 ms).

Index arrhythmia: sustained monomorphic ventricular tachycardia, cycle length 200 ms.

Complaint: palpitations.

Electrogram

Figure 6.23a. From top to bottom: atrial electrogram - (A), ventricular electrogram - (V), and marker channel. Markers: AF = atrial fibrillation/flutter; AR = atrial refractory sense; AS = atrial sensing; TD| = tachycardia detected; TP = tachycardia pacing; TS = tachycardia sensing.

ICD pulse generator: InSync 7272 (Medtronic Inc, Minneapolis, MN, USA). Tachycardia settings

Detection: VF = 250 ms; fast VT = 300 ms; VT = 400 ms. Discrimination: stability = 40 ms; PR Logic ON.

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

Bradycardia settings

Mode: DDD 70-120 bpm; mode switch = ON; AV = 110 ms.

Electrogram interpretation

1. Comparison between atrial and ventricular rate: VV interval > AA interval.

2. Description of the atrial rhythm: the atrial activity on the marker channel shows a fast atrial rhythm with an atrial cycle length ~ 180 ms. The atrial activity on the far-field electrogram shows a stable morphology with an alternans in amplitude. The atrial rhythm can be classified as atrial flutter or tachycardia.

3. Assessment of the onset of the tachyarrhythmia triggering device therapy: the marker channel demonstrates a stable ventricular rhythm with a consistent atrioventricular (AV) conduction pattern.

4. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular activity is consistent during tachycardia. The atrioventricular conduction pattern can be assessed from the marker channel. During the tachycardia, the marker channel demonstrates a consistent atrioventricular relationship. The tachycardia has a ventricular cycle length of ~ 360 ms, with a stability of ~ 10 ms.

Figure 6.23b.

5. Effect of therapy: During ATP (TP), the atrial activity is unaffected with respect to rate and morphology.

Diagnosis: atrial flutter with 2:1 atrioventricular conduction.

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