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    • Placement of implantable cardioverter defibrillators ICDs is

    2019-04-29

    Placement of implantable cardioverter–defibrillators (ICDs) is known to be the only and most powerful treatment modality for the prevention of sudden cardiac death in patients with a history of VF and/or aborted sudden cardiac death, i.e., for the so-called secondary prevention of sudden cardiac death [9]. The recurrence rate of VF in patients with Brugada syndrome is significantly higher, at 10% per year, [4] than other types of idiopathic VF [6,10]. On the other hand, the incidence of de novo VF occurring in patients with asymptomatic Brugada syndrome is very low [10–13]. However, the cardiac events caused by this disease are very harmful and lethal. In the light of the final cardiac event in asymptomatic patients with Brugada syndrome, it appears that these patients appear to have a poor prognosis [14]. However, ICDs can be used to completely prevent sudden cardiac death in such patients. Therefore, it is important to define the criteria for identifying high-risk patients among those without severe Brugada-type ECG changes.
    General aspects of the prognosis in patients with Brugada syndrome The prognosis of patients with a Brugada-type ECG naturally depends on the clinical types, on the basis of which the patients can be classified into the following groups: those with documented VF (symptomatic group), a syncope group, and an asymptomatic group. It is very difficult to accurately determine the distribution of these three groups among patients with the Brugada syndrome in the general setting, and according to major studies, it varies from 6.0–21.2% in the symptomatic group [11,15], 18.8–30.7% in the syncope group, [11,16] and 56.9–63.6% in the asymptomatic group [4,15] (Table 1) [4,11,15,16]. The annual cardiac event rate also varies and is 5.0–11.5% in the symptomatic group [4,16], 0.6–5.4% in the syncope group [4,11] and 0.24–3.6% in the asymptomatic group [4,16] (Table 1). A multicenter study on patients with Brugada syndrome [17] included 220 patients (46±12 years) with the type 1 Brugada ECG pattern who underwent ICD placement at14 centers, between 1993 and 2005. During a mean follow-up period of 38±27 months after the ICD implantation, no deaths occurred. Eight patients (3.6%) form this population experienced appropriate shocks. The three groups defined according to the ICD indications differed significantly in the rate of appropriate shocks (aborted sudden cardiac death, 22%; syncope, 10%; asymptomatic, 4%; p<0.025) during the follow-up. During the time to the first appropriate shock depending on the symptoms, two patients had shocks for monomorphic ventricular tachycardia (VT) (cycle length, 350 and 280 ms), and 16 had shocks for polymorphic VT or VF (mean nitric oxide inhibitor length, 199±37ms [range 160–260ms]). Patients with appropriate therapy had 10±15 shocks occurring 26±33 months after the ICD implantation. Seven patients (3.2%) presented with an arrhythmic storm and were treated with quinidine or ablation (4 patients) in the event of quinidine failure [17].
    The indications for ICD placement for the secondary prevention of sudden cardiac death Some patients with underlying heart disease and/or LV dysfunction die from tachyarrhythmias even after ICD placement [18]. However, no arrhythmic deaths occurred during the implantation or during the follow-up period in this young, otherwise healthy population of Brugada syndrome patients [17]. Appropriate shocks were more frequent in symptomatic than in asymptomatic patients (12% vs. 4%; p<0.05) [17]. These data are relevant to and in agreement with other reports on sudden cardiac death risk stratification [4,12,16]. Therefore, there is a world-wide consensus for ICD placement in symptomatic patients. However, there is a 2.5-fold greater frequency of inappropriate (20%) than appropriate shocks (8%), with an overall complication rate of 28% [17] .We should be well aware of all the complications related to ICD placement in order to explain them to candidates undergoing placement of the device for secondary prevention of sudden cardiac death.
    Complications of ICDs Complications occurred in 28% of the patients, including inappropriate shocks in 20% of the cases [17]. Early complications (the first months) included pneumothorax, pericardial effusions, re-intervention for a lead displacement, venous thrombosis, and hematomas. Late complications (more than 1 month after the implantation) consisted of lead failures requiring an extraction and re-implantation, pocket and/or lead infections, pericardial effusions, pocket revisions for deeper implantations of a superficial lead, device failures, and severe psychological difficulties (Table 2). Complications also included inappropriate shocks (4±3 shocks/patient) occurring in 20% of the patients during a period of 21±20 months after the ICD implantation. The reasons for the inappropriate shocks were lead dysfunction, T-wave oversensing, sinus tachycardia, and supraventricular arrhythmias. Patients with shocks due to T-wave oversensing were more likely to have low R-wave amplitude at the implantation. Factors predictive of inappropriate shocks were a history of supraventricular tachycardia (p<0.02), T-wave oversensing (p<0.001), and a low R-wave amplitude (p<0.007). Further, patients with inappropriate shocks tended to be younger [17]. Among the complications of ICDs for primary prevention, [19] inappropriate shocks were noted in 47 asymptomatic Brugada syndrome patients; eight patients with sinus tachycardia; six patients with new-onset atrial arrhythmias; and 5 patients with noise oversensing during a median follow-up period of 47.5 months. In a multivariable Cox-regression analysis, new-onset atrial fibrillation and age less than 50 years were independent predictors of a significantly short inappropriate-shock-free survival (p=0.04 and p=0.036, respectively). In the young and otherwise healthy population of Brugada syndrome patients, the inappropriate shock rate is high [17,19]. However, recent advances in electrophysiological technology have led to the development of an algorithm and/or signal processing tools for successfully reducing the incidence of inappropriate and unnecessary shocks [20,21].