Pacemaker malfunction following transthoracic countershock

Subcutaneous cardioverter-defibrillator implantation in an adult with congenital heart disease and left infra-mammary pacemaker

The approach/type of an implantable cardioverter defibrillator (ICD) is determined by the underlying cardiac anatomy, venous access, and pre-existing cardiac implantable electronic devices. We describe a case of subcutaneous ICD implantation in an adult with congenital heart disease (CHD) with a pre-existing inframammary transvenous pacemaker. This was preferred over adding a defibrillator coil to existing pacing leads, extraction/replacement of pacing system, or a sternotomy/epicardial ICD placement. The procedure was accomplished uneventfully with successful defibrillation threshold testing. Innovative approaches are required to manage arrhythmias in adults with CHD, with shared decision making playing a critical role.

External electrical cardioversion in patients with cardiac implantable electronic devices: Is it safe and is immediate device interrogation necessary?

BACKGROUND

Atrial tachyarrhythmias are common in patients with cardiac implantable electronic devices (CIEDs). Restoration of sinus rhythm by external electrical cardioversion (eECV) is frequently used to alleviate symptoms and to ensure optimal device function.

OBJECTIVES

To evaluate the safety of eECV in patients with contemporary CIEDs and to assess the need for immediate device interrogation after eECV.

METHODS

We conducted a retrospective observational study of 229 patients (27.9% female, age 69 ± 10 years) with a CIED (104 pacemakers, 69 implantable cardioverter defibrillators, and 56 biventricular devices) who underwent eECV between 2008 and 2016 in two centers. Data from device interrogation before eECV, immediately afterwards, and at first follow-up (FU) after eECV were collected. CIED-related complications and adverse events during and after eECV were recorded.

RESULTS

No significant differences between right atrial (RA) and right ventricular (RV) sensing or threshold values before eECV, immediately afterwards, or at FU were observed. A small yet significant decrease was observed in RA and RV impedance immediately after eECV (484 Ω vs 462 Ω, P < 0.001 and 536 Ω vs 514 Ω, P < 0.001, respectively). The RV impedance did not recover to the baseline value (538 Ω vs 527 Ω, P  =  0.02). The impedance changes were without clinical consequences. No changes in left ventricular lead threshold or impedance values were measured. No CIED-related complications or adverse events were documented following eECV.

CONCLUSION

eECV in patients with contemporary CIEDs is safe. There seems to be no need for immediate device interrogation after eECV.

Iatrogenic Cardiovascular Disease Secondary to Diagnostic and Therapeutic Procedures

The number of diagnostic and therapeutic procedures performed in cardiology continues to grow. These pro cedures are generally considered safe or of minimal risk to the patient. However, it is important to remember that significant complications may occur, and in each patient the risk: benefit ratio must be carefully weighed. In this review, the complications documented in the medical literature resulting from the use of cardiologic interventions and procedures are discussed. A thorough knowledge of these complications and their precipitat ing factors can help minimize the risk to the patient.

Pacemakers and implantable cardioverter defibrillators--general and anesthetic considerations

A pacemaking system consists of an impulse generator and lead or leads to carry the electrical impulse to the patient's heart. Pacemaker and implantable cardioverter defibrillator codes were made to describe the type of pacemaker or implantable cardioverter defibrillator implanted. Indications for pacing and implantable cardioverter defibrillator implantation were given by the American College of Cardiologists. Certain pacemakers have magnet-operated reed switches incorporated; however, magnet application can have serious adverse effects; hence, devices should be considered programmable unless known otherwise. When a device patient undergoes any procedure (with or without anesthesia), special precautions have to be observed including a focused history/physical examination, interrogation of pacemaker before and after the procedure, emergency drugs/temporary pacing and defibrillation, reprogramming of pacemaker and disabling certain pacemaker functions if required, monitoring of electrolyte and metabolic disturbance and avoiding certain drugs and equipments that can interfere with pacemaker function. If unanticipated device interactions are found, consider discontinuation of the procedure until the source of interference can be eliminated or managed and all corrective measures should be taken to ensure proper pacemaker function should be done. Post procedure, the cardiac rate and rhythm should be monitored continuously and emergency drugs and equipments should be kept ready and consultation with a cardiologist or a pacemaker-implantable cardioverter defibrillator service may be necessary.

Ventricular pacing threshold after transthoracic external defibrillation with two different waveforms: an experimental study

AIMS

Although an increase in the ventricular pacing threshold (VPT) has been observed after administration of transthoracic shock for ventricular defibrillation, few studies have evaluated the phenomenon with respect to the defibrillation waveform energy. Therefore, this study examined the VPT behaviour after transthoracic shock with a monophasic or biphasic energy waveform.

METHOD AND RESULTS

Domestic Landrace male piglets implanted with a permanent pacemaker stimulation system were divided into three groups: no ventricular fibrillation (VF) induction and transthoracic shock with monophasic or biphasic energy (group I); VF induction, 1 min of observation without intervention, 2 min of external cardiac massage, and transthoracic shock with monophasic or biphasic energy (group II); and VF induction, 2 min of observation without intervention, 4 min of external cardiac massage, and transthoracic shock with monophasic or biphasic energy (group III). After external shock, the VPT was evaluated every minute for 10 min. A total of 143 experiments were performed. At the end of the observation period, groups I and II showed steady VPT values. Group III showed an increase in VPT with monophasic or biphasic external energy, with no difference between the external energy sources. The monophasic but not the biphasic waveform was associated with higher VPT values when the VF was longer.

CONCLUSION

Defibrillation does not have a significant impact on pacing threshold, but a longer VF period is related to a higher VPT after defibrillation with monophasic waveform.

Mohs Micrographic Surgery in a Patient with a Deep Brain Stimulator: A Review of the Literature on Implantable Electrical Devices

BACKGROUND

Implantable electrical devices are becoming increasingly common in the patient population presenting for Mohs micrographic surgery. In addition to understanding the potential intraoperative complications with implantable cardioverter-defibrillators and pacemakers, the Mohs surgeon needs to be aware of the relatively new treatment of movement disorders using implanted deep brain stimulators.

OBJECTIVE

We present only the second reported case of Mohs surgery in a patient with a deep brain stimulator. In an attempt to help minimize adverse events during a procedure, we review the more commonly encountered electrical devices as well as the newer deep brain stimulators. We provide guidelines for the avoidance of electromagnetic interference during an electrosurgical procedure.

METHODS

This 76-year-old patient with Parkinson's disease and an implanted deep brain stimulator underwent Mohs surgery for excision of a squamous cell carcinoma on the ear. In an attempt to minimize electromagnetic interference with his implanted device, hemostasis was obtained with the aid of a battery-operated heat-generating handheld electrocautery device.

RESULTS

The patient tolerated the procedure well without complications or reports of discomfort.

CONCLUSION

Patients with implanted electrical devices are subject to electromagnetic interference during an electrosurgical procedure. Care must be taken in this expanding patient population during a Mohs surgical procedure.

Electrosurgery and cardiac devices

The increased number of patients with implantable cardiac devices presents a unique challenge to physicians performing office-based electrosurgical procedures. Electrosurgery can be performed safely if the electrosurgical techniques and potential risks from these devices are understood. We present an overview of the most common types of implantable cardiac devices, potential complications associated with them, and recommendations for preoperative evaluation, intraoperative monitoring, and postoperative follow-up.

ICD-antiarrhythmic drug and ICD-pacemaker interactions

Antiarrhythmic drugs and separate bradycardia pacing systems are prescribed commonly in patients with implantable cardioverter defibrillators (ICDs). Adverse effects of antiarrhythmic drugs on ICD function and adverse interactions between ICDs and pacemakers have been documented. The effect of antiarrhythmic drugs on the defibrillation threshold (DFT) in patients has not been well assessed. Most studies have been performed in animal models in which cardiac function was normal and drug doses were supraphysiologic. In addition, most studies have utilized monophasic defibrillation shock waveforms and epicardial lead systems. Despite the lack of clinical data applicable to current defibrillation systems, it appears that chronic amiodarone administration causes a significant DFT increase. In addition, antiarrhythmic drugs can influence antitachycardia pacing and tachycardia sensing. Defibrillation shocks can cause transient failure of pacemaker sensing and pacing, and cause spurious pacemaker reprogramming. Pacemaker function can result in ICD oversensing, leading to inappropriate therapy, or cause ICD undersensing, potentially resulting in failure to deliver therapy during ventricular fibrillation. The susceptibility of an ICD to undersensing appears related to the amplitude of the pacing stimulus artifact recorded by the ICD rate-sensing circuit and to the characteristics of the fibrillation electrogram. Preliminary data suggest that undersensing of ventricular fibrillation by current ICDs is an unlikely event.

Semi-automatic external defibrillation and implanted cardiac pacemakers: understanding the interactions during resuscitation

Many emergency medical service (EMS) systems are currently implementing semi-automatic external defibrillation (AED) by emergency medical technicians. Surprisingly little information is available on the possible interactions between AEDs and implanted cardiac pacemakers. Therefore, at present there are no clear guidelines for the use of AEDs on patients having a cardiac pacemaker. During resuscitation, multiple interactions between pacemakers and AEDs are possible. External defibrillation can cause damage to several functions of the pacemaker. On the other hand, the presence of pacemaker spikes during cardiac arrest might prohibit recognition of the ventricular fibrillation by the AED. We report on two resuscitation attempts in which the interaction between the ventricular fibrillation, an implanted dual chamber pacemaker and the AED was decisive for the defibrillation success. A clear understanding of these possible interactions is necessary for the further refining of diagnostic algorithms and clinical strategies of prehospital defibrillation.

Clinical interactions between pacemakers and automatic implantable cardioverter-defibrillators

Concomitant use of a pacemaker and an automatic implantable cardioverter-defibrillator (AICD) is common. Seventeen percent of patients receiving an AICD at The Johns Hopkins Hospital also had a permanent pacemaker implanted before (16 patients), at the same time as (2 patients) or after (12 patients) AICD implantation. Four types of interactions were noted: 1) transient failure to sense or capture immediately after AICD discharge (seven patients); 2) oversensing of the pacemaker stimulus by the AICD, leading to double counting (one patient); 3) AICD failure to sense ventricular fibrillation resulting from pacemaker stimulus oversensing (three patients, one only at high asynchronous output); and 4) pacemaker reprogramming caused by AICD discharge (three patients). No clinical sequelae of these interactions were noted during follow-up study. Thus, potentially adverse clinical interactions are common and routine screening is recommended. With proper attention to lead placements and programming of the devices, clinical consequences of these interactions can be avoided.

Function of ventricular pacemakers during resuscitation

The reciprocal effects of resuscitation and permanent, ventricular-inhibited pacemakers were examined in four, well-documented cases of witnessed out-of-hospital arrest. The resulting observations provide useful insight in the treatment of cardiac arrest in the large number of patients with permanent pacemakers. Transient sensing malfunctions occurred in the two patients in whom direct current countershocks were not required and were probably related to the severely deranged state of the myocardium. In spite of periods of asynchronous pacing in this critically unstable setting, no arrhythmias were precipitated. In the two patients who required defibrillation, transient malfunctions of pacing, capture and sensing occurred in spite of protective electronics in the pacing system, the left-sided location of the generator and, in one patient, the bipolar configuration. The pacemaker appeared to intermittently sense coarse ventricular fibrillatory waves. The malfunctions in the two latter cases were probably the result of the combined effects of the countershock and the abnormal state of the myocardium. All four patients succumbed, three in the emergency room and one on the eighth hospital day. Outcome was predominantly determined by the patient's response to therapeutic interventions. The observed pacemaker malfunctions, although potentially life-threatening, had no obvious, adverse effect on outcome in these four cases, mainly because of the transient nature of the abnormalities. Indeed, in one case, the presence of pacemaker activity was pivotal in identifying the native rhythm, illustrating the diagnostic potential of this analytical approach.

Implanted automatic defibrillators: effects of drugs and pacemakers

The automatic implantable cardioverter defibrillator is an effective device for prevention of sudden cardiac death. Patients who require the implantation of the device often require permanent pacing for symptomatic bradyarrhythmias and may require antiarrhythmic drug therapy. Antiarrhythmic drugs may alter the defibrillation thresholds, arrhythmia cycle length and frequency, pacing thresholds and postshock excitability. Interactions between the defibrillator and the pacemaker may result in sensing problems, leading to multiple counting and inappropriate shocks, or ventricular fibrillation nondetection, sensing or capture failure post defibrillation and pacemaker reprogramming induced by defibrillator discharge. The potential for interactions will increase as the new generation of programmable defibrillators become clinically available, combining features of permanent pacemakers, antitachycardia pacemakers and defibrillators.

Increased pacing threshold after an automatic defibrillator shock in dogs: effects of class I and class II antiarrhythmic drugs

A high energy shock delivered by an automatic defibrillator may interfere with pacemaker function. To provide insight into the changes that occur in the threshold for ventricular pacing after the shock from an automatic defibrillator, we measured the time to capture during asynchronous ventricular pacing in dogs from endocardial or epicardial sites, after a 30 joule shock was delivered via conventional automatic defibrillator (AICD) patch electrodes. After a 30 joule shock, there was a transient loss of ventricular capture. The duration of capture loss was related to current strength. During endocardial pacing at threshold current, the time to capture was 4.9 +/- 1.2 s, whereas at current values twice threshold the time to capture from endocardial pacing was 2.2 +/- 0.9 s. No difference was found between endocardial and epicardial pacing sites in the time to capture. To ascertain the mechanism of capture loss we: (1) examined the effects of converting the pacing catheter to a current sink (transiently shunting to ground); (2) altered excitability by an infusion of flecainide; (3) blocked sympathetic input (propranolol). No change in time to capture was noted by shunting the pacer to ground. After an infusion of flecainide the time to capture from endocardial pacing was significantly prolonged to 14.9 +/- 2.2 s at the threshold value (P less than .01) and 5.6 +/- 2.1 s at twice threshold (P less than .05). Conversely, intravenous propranolol had no effect on the time to capture after shock from endocardial pacing. These data indicate that there is a transient increase in pacing threshold after the shock from an automatic defibrillator.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrosurgery and cardiac pacemakers

There are two basic types of cardiac pacemakers: (1) Fixed-rate pacemakers stimulate the heart at a regular rate independent of the intrinsic heart rate. (2) Demand pacemakers sense the heart's spontaneous rhythm. They are more commonly used because they are noncompetitive with the heart. There are two varieties of demand pacemakers: ventricular-inhibited and ventricular-triggered. Their responses to electrical interference are quite different. Potential pacemaker interference is a consideration with high-frequency electrosurgery. The problems with electrosurgical interference have occurred primarily with early pacemaker models. Recent improvements in electrical shielding and filtering systems have made pacemakers very resistant to outside electrical influence. Simple electrodesiccation of small lesions on relatively healthy pacemaker patients poses negligible risks. Caution is advised for marginal patients undergoing extensive electrosurgical procedures. The potential risks are further minimized by proper attention to patient history, monitoring, proper grounding, the avoidance of cutting current, and the use of proper technic.