Pitfalls of internal cardioverter defibrillator implantation: Part II

On the 12-lead ECG (please refer to Figure 1 in part I, page 237), there is a regular tachycardia at 191 bpm and broad QRS complexes (200 ms) with left bundle branch block morphology. QRS duration and axis suggest ventricular tachycardia. There are deep Q waves in III and aVF. R-S in the precordial leads is >100 msec. However, other typical features of ventricular tachycardias are absent: there is no clear atrioventricular dissociation (although the P waves with 1:1 relation with the tachycardia are possibly seen in lead II after the QRS complex), no fusion beats, and no positive or negative concordance of the QRS complexes in the precordial leads. As such, there is no proof that this tachycardia is of ventricular origin, but considering the medical history and evidence of old myocardial infarction on the 12-lead ECG during sinus rhythm after cardioversion ( Figure 1 ), late onset ventricular tachycardia is the most probable diagnosis. Because persistent ventricular tachycardia was not clearly related to ischaemia, it prompted the decision to implant an internal cardioverter defibrillator (ICD) as the first step. Twelve-lead ECG after cardioversion of broad complex tachycardia. Choosing the best site of implantation of rhythm management devices is often influenced by local anatomy, previous surgery or radiation, or the patient’s preference (e.g. in young and active individuals). It is generally accepted that pectoral placement is the first choice because of ease of implantation and vascular access as well as the achievement of good shock vectors. Whereas for pacemakers there seems to be no obvious advantage left- over right-sided implantation, there is evidence that the preferred region for ICD implantation is left pectoral. There is a slightly lower defibrillation threshold during testing. Long-term assessment of ambulatory effectiveness for spontaneous arrhythmias seems to be comparable. 1 However, in a large series, all-cause mortality has been significantly higher with the right-sided implants (odds ratio 1.93). 1 Choosing a subcutaneous vs. subpectoral pocket has no obvious influence on defibrillation threshold (DFT) although this has never been prospectively tested. This decision should thus be made on anatomical grounds. Placement of epicardial patches used to be a standard approach for defibrillator leads and is still available for implantation. Implantation, however, is technically far more demanding. This approach should thus be reserved for special cases. A controversial issue is the use of single vs. dual-coil shock electrodes. Several randomized trials failed to show a difference in DFT between the two strategies, 2 , 3 whereas others show a slightly lower DFT. 4 In right-sided implantations dual-coil electrodes seem to perform worse than active can devices. 5 Possible ingrow of dual-coil leads in the superior vena cava can be an important obstacle for lead removal as this may become necessary although there is an active search for solutions of this problem with different coil coatings. The standard use of high output ICD devices can be considered to overcome high defibrillation thresholds. These devices could also provide higher longevity that is, however, offset by a slightly larger can size. Numerous case reports have demonstrated the possibility and effectiveness of implantation of ICD leads through a persistent left superior vena cava. Implantation, however, can be technically demanding. ICD leads are significantly more rigid than pacemaker leads and are thus less easy to manipulate. A possible technique is forming a loop in the right atrium and advancement through the tricuspid valve and the use of stylets bent in a way to ease manipulation of the lead. Two weeks after the described case, we came across a patient with a persistent left superior vena cava and placement of the ICD lead was achieved with excellent sensing values and a low stimulation threshold ( Figure 2 ). Defibrillation testing was successful at 20J. There is no data comparing left- and right-sided implantation in these patients. In the light of generally higher defibrillation thresholds on the right side 1 , 5 and possibly higher all-cause mortality, 1 we propose to attempt lead placement in case of this anatomic variant. Chest X rays after internal cardioverter defibrillator implantation in a patient with persistent left vena cava: (a) posteroanterior view; (b) lateral view. With the current high-voltage devices failure of effective defibrillation with sufficient buffer has become a less-encountered problem. However, with the high case-load and increasingly complex anatomies such as adult congenital heart disease, physicians specialized in device implantation will encounter high DFTs and need to be aware of possible solutions. Reversing shock polarity is in the most cases sufficient to lower DFT. 6 A different RV lead position of a single-coil lead will often lead to a lower DFT. 6 The optimal position, however, can be highly variable and is difficult to predict. Placement of the can in a different pocket could also be used to create a different vector. In a right side implantation, the leads could be tunnelled to a left pectoral pocket. The most commonly used technique is placement of a single subcutaneous lead or a subcutaneous lead array. In most cases, this will lead to a reduction in DFT and DFT does not significantly change over time. 7 In a right-sided implantation, however, the subcutaneous lead has to be tunnelled via the sternum to the left side and further in the intercostal space leading to a fairly long distance. A less commonly used strategy is placement of a coil in the azygos vein. This position can substantially reduce DFT. 8 In our patient with a persistent left vena cava placement of an additional coil in the coronary sinus could have been an option but long-term consequences are not known. We have chosen for a subcutaneous lead tunnelled through the sternum ( Figure 3 ). With this additional lead the defibrillation threshold was <21J. Chest X rays in a patients after addition of subcutaneous shock coil: (a) posteroanterior view; (b) lateral view. The patient was discharged 1 day after placement of the subcutaneous lead and quickly resumed his daily activities without any symptoms. Two weeks after discharge, the patient again attended a professional football contest and while climbing the stairs of the grandstand, he felt dizzy and nauseous. This was followed by an ICD shock. The patient presented the next day at the ICD clinic for check-up and interrogation of the device showed fast ventricular tachycardia with a cycle length of 280 ms which was successfully terminated by an ICD shock at 31J. Patient’s medication was optimized and anti-tachycardia pacing was programmed. This case highlights several common problems with ICD implantation. Choice of implantation site can be influenced by numerous variables such as the vascular access, anatomy, and the dominant hand, particularly in young and active patients. Failure to achieve an adequate DFT has become less common with high-voltage output devices but physicians involved in device implantation need to be aware of possible pitfalls and must be aware of options to solve this issue.