Case 31 Multiple Shocks on the Waiting List for Heart Transplantation

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Patient: 43-year-old male, with coronary artery disease, heart failure NYHA class III, on the waiting list for heart transplantation. ICD at age 41, recent admission with exacerbation of heart failure, treated with diuretics. Discharged from hospital 2 weeks before the event.

Index arrhythmia: non-sustained ventricular tachycardia.

Complaint: six shocks, no palpitations, no chest pain.

Figure 6.31a. Electrocardiogram (lead II): at previous control (left) and at admission (right). No new Q waves, nor ST elevations were seen.

ICD pulse generator: Marquis VR 7230 (Medtronic, Minneapolis). Tachycardia settings

Detection: VF = 330 ms; FVT = 240 ms (via VF); VT = 360 ms. Discrimination: onset = 88%; stability = 40 ms; wavelet ON, threshold 70%. Therapy: VF = shock; FVT = antitachycardia pacing (burst), VT = monitor.

Bradycardia settings Mode: VVI 40 bpm.

Electrocardiogram interpretation

The P wave has an amplitude of 2.5 mV and a width of 160 ms. This is similar compared to former tracings. The ST depression of 2 mm is now very prominent.

140 6. Clinical Case Studies Initial tachogram

Burst Fib Medtronic Plot Egm
Figure 6.31b. The interval plot shows variable V-V intervals, several fall within the VT one and the normal zone; the majority lies within the VF zone. After burst pacing, five shocks are delivered.

In the second tachogram (not shown), the same arrhythmia is present, and three additional shocks are given, resulting in a slower irregular rhythm.

Last tachogram

Figure 6.31c. A burst ATP episode converts the fast arrhythmia to a slower one. The electrogram of this last episode is shown below.

Figure 6.31d. From top to bottom: ventricular bipolar and wide-band electrogram, with marker channels. TF. = ventricular sense, fast ventricular tachycardia window; TP = pacing for tachycardia; TS = tachycardia sensing; VS = ventricular sense.

1. Tachycardia: present, highly irregular (cycle length 240-400 ms; bringing the rhythm in the FVT zone). FVT is confirmed.

2. Assessment of the onset of the tachyarrhythmia: the baseline rhythm is probably sinus rhythm, with atrial extrasystoles and a fast conducted atrial fibrillation.

3. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular activity is similar during tachycardia, and during the complexes after ATP; before onset the complexes are somewhat different.

4. ATP (9 pulses) results in a slower rhythm, probably by making the AV-node refractory.

Diagnosis: atrial fibrillation resulting in multiple shocks. The patient had CK levels increasing to five times the normal value, and high Troponin T levels, making the diagnosis of non-ST segment elevation myocardial infarction likely. His potassium level was 3.5 meq/l.

Actions: reprogramming to single zone (VF, 230 bpm). An alternative would have been to create a VT zone with stability of 30 ms.

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