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Device Lab Set-Up
Published in Andrea Natale, Oussama M. Wazni, Kalyanam Shivkumar, Francis E. Marchlinski, Handbook of Cardiac Electrophysiology, 2020
Every lab should be equipped with emergency equipment. A combination defibrillator/external pacemaker is essential. The most frequent use of the defibrillator is for cardioversion and as a back-up to an internal cardiac defibrillator in defibrillation threshold testing. There should also be a cart stocked with emergency medications used for cardiopulmonary arrests (code cart), pericardiocentesis kit, and in centers performing high risk procedures, an open chest kit can be stocked. A pericardiocentesis kit should be available in the event of a lead perforation.
Implantable cardioverter defibrillators
Published in Ever D. Grech, Practical Interventional Cardiology, 2017
Dominic Rogers, Abdallah Al-Mohammad
The implantation of an ICD was previously not considered complete until a threshold for defibrillation (the lowest amount of energy required to terminate VF) was determined. Thus, defibrillation threshold testing (DFT) was a routine part of an implant procedure. To avoid repeated inductions, it became more common to perform one or two VF inductions with attempted defibrillation at a specified energy (10 J or 15 J) below the maximum output of the implanted device; successful defibrillation demonstrated at these outputs suggested an adequate safety margin of defibrillation energy. Thus, rather than defining a defibrillation threshold, this is an assessment of the efficacy of defibrillation, termed defibrillation testing (DT). With a reduction in the amount of energy required to defibrillate, and the increased energy available from contemporary devices, it has been questioned how necessary the DT is as part of a procedure, particularly as the circumstances of a planned defibrillation in the cath lab (a supine, unmoving, often sedated patient with an electrically induced ventricular arrhythmia) differ so much from a ‘real-life’ spontaneous VF in the context of ischaemia, hypoperfusion and acidosis.
Resuscitation
Published in Karim Ratib, Gurbir Bhatia, Neal Uren, James Nolan, Emergency Cardiology, 2010
Karim Ratib, Gurbir Bhatia, Neal Uren, James Nolan
Shocks are initially started at between 150 J and 360 J with a biphasic device. Biphasic shocks involve the polarity of the current being reversed part way through the delivery of a shock, as a result the defibrillation threshold is lowered and the shock energy required for successful defibrillation is reduced. Monophasic defibrillators are being phased out as they are less efficient at terminating VF/VT. If they are used they should be set to 360 J from the outset. The paddles should be applied firmly to the chest wall with water-based gel pads between them and the skin. The pressure applied should be approximately 8 kg of force and the correct positions are shown in Figure 2.2a. The use of hands-free self-adhesive pads allows for safer operation by allowing the operator to discharge the device without leaning over the patient. They also allow for quick identification of rhythm and therefore quicker defibrillation than using standard electrodes. If defibrillation is unsuccessful in the anterolateral position, then further attempts in the anteroposterior position (Figure 2.2b) and/or a different defibrillator are worth trying. The positions of the positive and negative paddles do not matter when defibrillating.
How to minimize peri-procedural complications during subcutaneous defibrillator implant?
Published in Expert Review of Cardiovascular Therapy, 2020
Muhammad R. Afzal, Toshimasa Okabe, Kevin Hsu, Schuyler Cook, Tanner Koppert, Raul Weiss
CT is recommended at the time of initial S-ICD implantation, and it is a routine practice to perform DT unless contraindicated [37]. Despite the class I recommendation, recent National (NCDR) registry showed approximately 25% of the S-ICD recipients did not undergo CT between 2012 and 2015 [38]. There is a growing body of evidence to suggest forgoing CT after S-ICD implantation may be appropriate [39,40]. Larger prospective studies are needed to confirm the safety of forgoing CT in S-ICD. The PRAETORIAN-DFT is a currently ongoing randomized study to evaluate the value of CT based on the post-implant chest X-ray parameters [41]. PRAETORIAN score incorporates sub-coil fat, sub generator fat, and anterior positioning of the subcutaneous generator. Development of this score was based on clinical and computer modeling knowledge of determinants affecting the defibrillation threshold including sub-coil fat, sub generator fat, and anterior positioning of the subcutaneous generator [41–43]. This score allowed the identification of patients with high defibrillation threshold by using the routine chest x-ray. The efficacy of this scoring system is being investigated in a prospective randomized study.
Current pharmacotherapeutic strategies for cardiac arrhythmias in heart failure
Published in Expert Opinion on Pharmacotherapy, 2020
Ashish Correa, Yogita Rochlani, Wilbert S. Aronow
Anti-arrhythmic drugs and/or catheter ablation may be used to supplement ICD implantation, and only in very rare circumstances (for example, when a patient declines implantation of an ICD) are they used as the first-line therapies for the secondary prevention of SCD. The main indication for the use of drug therapy is the prevention of ICD shocks, which can adversely affect the quality of life of patients. In HF patients, drug therapy is usually limited to amiodarone, sotalol, and mexiletine. Sotalol has been shown to be a safe and effective option for reducing ICD shocks, regardless of the presence or absence of HFrEF [84]. The Optimal Pharmacological Therapy in Implantable Cardioverter Defibrillator Patients (OPTIC) trial showed that amiodarone (with a beta-blocker) was effective in reducing ICD shocks and was better than sotalol [85]. However, the trial also showed that amiodarone was less well tolerated and was associated with a number of adverse reactions, which is why sotalol is often tried before amiodarone. Sotalol has both class III anti-arrhythmic effects and beta-blocker effects. Amiodarone is usually combined with beta-blockers, as it primarily has class III anti-arrhythmic effects and weaker negative chronotropy. It should also be remembered that amiodarone can raise the defibrillation threshold of ICDs, and this can affect its efficacy. Mexiletine has also been used alone or usually in combination with a class III agent [86]. (Refer to Table 2.)
Sedation in cardiac arrhythmias management
Published in Expert Review of Cardiovascular Therapy, 2018
Federico Guerra, Giulia Stronati, Alessandro Capucci
As many anesthetics and sedatives have a direct effect on cardiac ion channels, concerns have been raised about a potential interference with DFT reliability. First, lidocaine and other local anesthetics with class IB antiarrhythmic properties have traditionally been associated with an increased defibrillation threshold in a dose-dependent fashion [26]. Fortunately, subsequent reports reassured the electrophysiologist, as lidocaine’s effect on the defibrillation threshold was not significant neither for biphasic waveforms [27] nor for endocardial shocks [28]. On the other hand, inotropes and vasopressors administered to counterbalance the vasodilatative and hypotensive effects of many anesthetics increase the defibrillation threshold in animal models [29]. Lastly, mechanical ventilation and positive-pressure ventilation have been shown to change transthoracic impedance, thus potentially changing the arrhythmic substrate by their own [30].