Author + information
- Ilya V. Ryaboy, MD∗ ( and )
- Mark E. Peele, MD
- Department of Cardiology, Brooke Army Medical Center, San Antonio, Texas, Uniformed Health Services Consortium, San Antonio, Texas
- ↵∗Address for correspondence:
Dr. Ilya V. Ryaboy, 3551 Roger Brooke Drive, Fort Sam Houston, Texas 78234.
An 88-year-old female presented with inappropriate implantable cardioverter-defibrillator shocks. Interrogation revealed lead noise sensed as ventricular fibrillation, leading to 11 shocks in 1 day. A defibrillation at the period of maximal vulnerability caused true ventricular fibrillation/ventricular tachycardia and additional shocks, which failed to terminate device-initiated tachyarrhythmia. The patient recovered spontaneously. The device was reprogrammed. (Level of Difficulty: Intermediate.)
An 88-year-old female with a cardiac resynchronization therapy defibrillator (CRT-D) was brought to the emergency department after collapsing at her assisted living facility. No resuscitation was undertaken; the patient recovered consciousness spontaneously. She complained of having been “punched in the chest” several times that morning. Prior to this presentation, she was in her usual state of health. Review of systems was negative. She had neither been shocked in the past nor had tachyarrhythmia. Physical examination revealed an anxious elderly African-American female who was otherwise normal.
• To identify inappropriate implantable cardioverter-defibrillator (ICD) defibrillations and to deactivate the device accordingly;
• Recognize the double-edged nature of ICD therapies and possible complications, including lead migration, lead fracture, inappropriate shocks, and device-initiated tachyarrhythmia episodes.
Medical history included heart failure with reduced ejection fraction (HFrEF), complete heart block (CHB), venous insufficiency, hypertension, breast cancer, modified right radical mastectomy, idiopathic lead migration (ILM), and numerous intracardiac device procedures. A dual-chamber permanent pacemaker was initially implanted in 2002 for CHB. She developed HFrEF due to high right-ventricle (RV) pacing burden and was upgraded to a CRT-D in 2011. Three subsequent device revisions for lead fracture and dislodgment due to ILM were eventually required (Figure 1). Her last device revision for lead failure in 2012 revealed complex occlusive venous anatomy requiring lead extraction, lead replacement, and venous angioplasty. The patient was ultimately left with leads in the RV apex and coronary sinus; there was no atrial lead.
Ventricular tachycardia (VT), ventricular fibrillation (VF), ischemia, device malfunction, and metabolic disturbance.
Results of a chest radiograph obtained on admission were normal, without lead dislodgement (Figure 2). Device interrogation revealed significant electrical artifact on the RV-sensing lead, determined by the device to be VF, resulting in 11 delivered shocks. One episode of actual VF did occur, persisted despite 6 defibrillations, and lasted longer than 2 minutes before spontaneously terminating. This VF occurred after an inappropriate shock during the maximal vulnerability period, the “R-on-T” phenomenon. The CRT-D then delivered 5 more shocks, none of which successfully cardioverted the patient. The patient spontaneously converted out of polymorphic VT/VF into an intrinsic slow ventricular escape rhythm and resumed pacing (Figures 3 to 7).
Antitachycardia therapies were deactivated after the device was interrogated. Before this was accomplished, the patient’s device delivered 2 additional shocks in the emergency department with no preceding tachyarrhythmia noted on telemetry. Because the patient was pacer-dependent and retained normal pacing function, she was reprogrammed to asynchronous ventricular pacing (VOO). Due to a prior modified radical mastectomy and complex venous anatomy, there were no transvenous options for device implantation. Replacing a defibrillator would have required a subcutaneous or epicardial approach. The patient declined any procedure and was discharged in VOO-R mode with antitachycardia therapies deactivated. This was felt to be reasonable as she had a normal ejection fraction, no prior myocardial infarction, and prior to her single episode of VT/VF that was itself initiated by the malfunctioning device, had never required defibrillation.
Implantable cardioverter-defibrillators (ICDs) are used for primary prevention of sudden cardiac death in patients at high risk for ventricular arrhythmia, particularly those with HFrEF and conduction delay (1–4). Complications of ICD implantation range between <1% and 3%, with the most common being device infection, hematoma, and lead dislodgement (5,6). Inappropriate defibrillation, associated with significant health care costs and patient distress (7), may also occur. The most frequent causes of inappropriate shocks are supraventricular tachycardia and T-wave oversensing. An important, although rare, cause of inappropriate defibrillation is lead fracture.
A critical point in this case is that the patient experienced 2 defibrillations in the emergency department with no preceding tachyarrhythmia on telemetry. Even in the absence of electrogram review, this should prompt concern for inappropriate therapy and deactivation of antitachyarrhythmia therapies with a magnet. This would stop painful, unnecessary, defibrillations, and prevent R-on-T phenomena such as that which the patient experienced. In retrospect, the patient would have been better managed had her device been deactivated with a magnet as soon as the first shock occurred, rather than through device interrogation.
Distinguishing electrical noise from VF is crucial to understanding this patient’s presentation. The manufacturer provides unipolar (i.e., far-field), bipolar “sensing” (i.e., near-field), discriminatory (i.e., “leadless ECG” [electrocardiogram]), and marker channels. Importantly, the device uses only the bipolar “sensing” channel for rhythm analysis by the measurement of heart rate. The high-frequency, nonphysiological signals seen on the bipolar channel (Figures 3 and 7) represent lead microfractures connecting and disconnecting, generating short, high-frequency impulses known as “make-breaks.” This noise is not visible on other channels; were this VF, all channels would look similar. These make-breaks were counted by the device as intrinsic electrical activity occurring within the rate zone set as VF.
The patient met a class IIa recommendation for a defibrillator at the time of her initial CRT-D placement as she was undergoing an elective battery replacement and had an EF of <35% and an anticipated pacing burden of >40% (4). The relative risks and benefits of such an intervention should be frankly discussed with patients. Although device-initiated tachyarrhythmia, as occurred in this case, is rare, inappropriate shocks are not. According to the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) population (2), inappropriate shocks were more than twice as common as appropriate therapies within the first year of implantation (3). A recent review found that 22% of delivered shocks are inappropriate (6). Patients with ILM are at higher risk of inappropriate therapies, lack of therapies, lead dislodgement/fracture, and so forth. Lead migrations have numerous historic names, including “Twiddler’s Syndrome,” “reel,” versus “ratchet” mechanisms, and others (7). A recent review of 87 cases of ILM found that no conventional risk factors (e.g., manual device manipulation, elderly age, and so forth) were associated with lead migration (8). The patient in the current case had a history of ILM but no evidence of macro dislodgement during the recent admission.
After discharge, the patient was noted to have increasing RV lead impedance, consistent with lead fracture. The authors hypothesize that this is why 5 additional defibrillations, each of 40 joules, failed to defibrillate the patient after her R-on-T phenomenon: energy reaching the myocardium from a failing shocking coil was insufficient to defibrillate the patient but sufficient to organize the rhythm into 1 that then spontaneously converted. Impedance graphs of the RV lead over time confirm shocking coil fracture (Figure 8). The patient is currently doing well with bipolar LV pacing in VOO-R mode.
This case highlights the double-edged nature of defibrillators and the importance of recognizing and treating inappropriate defibrillations. Although this device was placed with the best intentions, to prevent sudden cardiac death, it was never used. When it was used, it was to correct a problem the device itself had caused that could have killed the patient had she not been fortunate enough to spontaneously convert out of VT. Patients complaining of ICD discharge should initially be evaluated with a history, physical examination, and device interrogation. Clinicians should be comfortable reviewing electrogram tracings and determining the cause of delivered therapies. Defibrillation without tachyarrhythmia noted on telemetry should instantly prompt consideration of deactivating antitachycardia therapies.
Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- complete heart block
- cardiac resynchronization therapy defibrillator
- heart failure with reduced ejection fraction
- implantable cardioverter-defibrillator
- idiopathic lead migration
- left ventricle
- right ventricle
- ventricular fibrillation
- ventricular tachycardia
- Received September 16, 2019.
- Revision received October 22, 2019.
- Accepted November 6, 2019.
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