Case 7 A Patient with Congenital Heart Disease and Therapies for a Short Arrhythmia

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Patient: 29-year-old male with surgically corrected complex congenital heart disease (double outlet right ventricle; malposition of the great arteries, VSD, and coarctation), left ventricular dysfunction, and superior vena cava syndrome, uses salbutamol inhalatorbecause he is asthmatic. QRS width 170 ms.

Index arrhythmia: sustained monomorphic ventricular tachycardia, cycle length 490 ms.

Complaint: recurrent palpitations, syncopal, wants to drive. Electrogram (Three continuous strips).

ICD pulse generator: Maximo VR 7232 (Medtronic Inc, Minneapolis, MN, USA). Epicardiac sensing electrodes and 6721 defibrillator patch.

Tachycardia settings

Detection: VF = 280 ms; fast VT = 240 ms; VT = 400 ms. Discrimination: stability = 30 ms; onset = 84%.

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

Bradycardia settings

Mode: VVI 40bpm; all fancy features off.

Electrogram interpretation (See Figure 6.7a)

1. Presence of tachycardia: yes.

2. Description of the onset: described by the device in the first strip as "gradual", which is not correct, when the intervals are considered.

3. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the FF and NF ventricular activity is similar and as wide as the complexes after spontaneous slowing. Only a little notch in the last part of the QRS in the NF electrogram suggests a different activation, which can be as easily explained as aberrancy.

4. Additional criteria and effect of therapy: the tachycardia CL varies between 230 and 240 ms in the first strip, before the slowing and the criteria for VF are met, triggering a shock. This does not affect the rhythm, varying between 370 and 390 ms in the second tracing, triggering ATP, once more not altering the QRS pattern.

Initiation Strip
Figure 6.7a. First strip: Markers: CD = charge delivered; CE = charge end; FD = fibrillation detected; FS = fibrillation sensing; TF = sense in fast VT window; VS = ventricular sense. Second and third strip: From top to bottom: near field, wide-band ventricular electrogram and markers.

Diagnosis: uncertain - supraventricular tachycardia with wide QRS complexes remains possible (see figure 6.7b). Former electrograms showed a more distinctive tachycardia pattern. The tachogram (not shown, but very gradual) and the salbutamol use suggest atrial tachycardia.

Rvot Ectopy
Figure 6.7b.

Actions: Increase the number of intervals before detection or confirmation.

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