Implantable cardioverter-defibrillators (ICDs) are routinely used for primary and secondary prevention of arrhythmia-related sudden deaths in patients with heart failure and reduced left ventricular ejection fraction.¹² Various early and late complications have been well described in the literature in patients with a transvenous ICD implantation.³⁴ This case report describes the implantation of a defibrillator lead to an unusual site and subsequent inappropriate shocks due to an atrial arrhythmia.

A 70-year-old male with ischemic cardiomyopathy underwent ICD (D264VRM Maximo II VR, Medtronic, USA) implantation for primary prevention of sudden cardiac death three years ago. The ICD device had a dual-coil defibrillator lead (Sprint Quattro Secure™, Medtronic, USA). The patient experienced multiple ICD shocks on the same day. The surface 12-lead electrocardiography (ECG) showed sinus rhythm (Figure 1A).

Device interrogation showed multiple recurrent successful and unsuccessful discharges with normal device parameters (pacing impedance of 684 Ω, distal coil defibrillation impedance of 67 Ω, proximal coil defibrillation impedance of >200 Ω (off), measured R-wave amplitude of 3.8 mV, programmed sensitivity of 0.3 mV, ventricular tachycardia detection rate of 182-207 bpm with ATP and shock delivery, ventricular fibrillation detection rate of >207 bpm with ATP before charging and shock delivery, and the wavelet on) and, the stored intracardiac electrograms (EGMs) of the events were analyzed and, the analysis of the sample episode revealed a sudden change to very rapid and irregular myocardial activity with EGM alternans (Figures 2A and 2B), resulting in no match of wavelets if the interval is not too fast (Figure 3) that reach ventricular fibrillation zone (calculated median ventricular cycle length, 180 ms) and, a shock was delivered which was resulted in restored sinus rhythm (Figure 2A). In addition, multiple episodes of aborted events were detected (Figure 2B). Chest X-ray and fluoroscopy showed the active-fixation ICD lead was in the coronary sinus (Figures 4A, 4B and Figure 5A). There was no ventricular but atrial capture with pacing from the ICD lead (Figure 1B). This could only be explained by sensing of atrial signal during an episode of paroxysmal atrial fibrillation (AF), due to inappropriate defibrillator-lead implantation to the main body of the coronary sinus during the first procedure. The patient has been treated with a new single-coil active-fixation ICD lead (Sprint Quattro Secure S™, Medtronic, USA) implantation into the right ventricle and, the old ICD electrode left in place due to refusal of lead extraction by the patient (Figures 4C, 4D, 5B, and C). The patient had no symptoms at 12 months follow-up.

The most common causes of inappropriate ICD therapies are supraventricular tachycardia, especially AF or atrial flutter with rapid ventricular response, T‐wave oversensing, and lead problems (noise and myopotentials).⁵ Dislodgement and migration of cardiac implantable electronic device leads are not uncommon, however lead placement into inappropriate areas is extremely rare.

The coronary sinus has become a clinically important structure especially through its role in providing access for different cardiac procedures.⁶ Accurate knowledge of the coronary venous anatomy is essential for electrophysiologists performing left ventricular pacing procedures or radiofrequency ablation.

In our case, the ICD lead implantation into the coronary sinus in a patient with AF episodes led to inappropriate unsynchronized shocks that returned AF to sinus rhythm. Probably, due to the acceptable R-wave amplitude and pacing threshold testing being performed without an ECG in device controls, it was not noticed that the lead was not at the proper location. Another reason might be incorrect interpretation of postero-anterior chest x-rays without obtaining lateral projections. Also, oblique fluoroscopic projections can help to confirm the optimal implantation site in the right ventricle during the implantation procedure.

In some rare cases, implantation of the lead into the coronary sinus can be needed. Various conditions requiring implantation into the coronary sinus are as follows; anatomical barriers that preclude the passage through the valve such as tricuspid atresia, stenosis, and mechanical prosthesis, failed implantation into the ventricle, presence of persistent left superior vena cava with the absence of right sided vein making the implantation near impossible, presence of abnormal ventricular substrate resulting in abnormal elevation of the capture threshold, and high defibrillation threshold.⁷⁸⁹¹⁰

Perioperative and postoperative ICD care is important to prevent any untoward harm to patients. Routine postoperative interrogation of the ICD should be done by the cardiac electrophysiologist/device specialist and, following the simple and basic rules including ECG and chest X-ray can demonstrate lead misimplantation or displacement.