Desfibrilador Implantável ( CDI ) Profile of Chagasic Patients with Implantable Cardioverter Defibrillators ( ICD )

Fundamentos: A morte súbita é responsável por 55-65% dos óbitos na doença de Chagas, e o cardioversordesfibrilador implantável (CDI) é a terapêutica mais efetiva para evitar morte súbita em pacientes com taquiarritmias ventriculares. Objetivo: Descrever o perfil clínico dos pacientes portadores de cardiopatia chagásica crônica com CDI internados em hospital de referência. Métodos: Foram avaliados 75 pacientes chagásicos, portadores de CDI, internados na Santa Casa de Misericórdia de Goiânia no período de janeiro de 2011 a dezembro de 2013, mediante revisão de prontuários. Resultados: A amostra (n=75) se constituiu de 57 (76,0%) pacientes do sexo masculino e 18 (24,0%) do sexo feminino. As internações clínicas representaram 60,0% da amostra e as de causas cirúrgicas 40,0%. Das causas clínicas, 40 (89,0%) foram de origem cardíaca: insuficiência cardíaca (IC) com 13 (32,0%) pacientes e a tempestade elétrica (TE) com 12 (30,0%) pacientes. Das 30 causas cirúrgicas, 17 (56,66%) se deveram a desgaste da bateria. Conclusão: O perfil clínico encontrado em pacientes portadores de cardiopatia chagásica crônica com CDI apresenta as seguintes características: sexo masculino, faixa etária entre 51-60 anos, presença de dispositivos de dupla-câmara, uso adequado de antiarrítmico e betabloqueador, presença de hipertensão arterial sistêmica (HAS), fração de ejeção do ventrículo esquerdo (FEVE) entre 35-45%, internações clínicas por causas cardíacas (em especial IC e TE), e número de internações pós-implante entre zero e três.


Introduction
Heart involvement is the most important and severe manifestation in the chronic phase of Chagas disease (ChD).This complication occurs in all endemic areas in proportions ranging from 10-40% of HIV-positive individuals, and manifests itself from five to 30 years after primary infection 1,2 .Tissue changes caused by the infectious and inflammatory process confirm clinical manifestations of chronic Chagas cardiopathy (CCC).Progressive destruction of the heart tissue leads to changes in the electrical bundles of the heart and consequent cardiac conduction disorders, clinically manifesting itself as potentially life-threatening cardiac arrhythmias 3 .Sudden death is one of the most significant phenomena of the natural history of Chagas disease, accounting for 55-65% of deaths; the often found mechanism is the sustained ventricular tachycardia (SVT), degenerating into ventricular fibrillation (VF).
The therapeutic armoury in the fight against sudden death includes antiarrhythmic drugs, endocardial catheter ablation and the implantation of electronic Profile of Chagasic Patients with ICD Int J Cardiovasc Sci.2015;28 (1): 35-41  Original Manuscript
Despite the progress in preventing sudden death by means of the ICD, device-related complications and those related to the evolution of the underlying heart disease are still a concern for researchers, primary care physicians and patients.Adverse events can occur from the very moment the device is implanted to months/years following its installation, ranging from mechanical and/or electrical complications to serious emotional disorders such as the post-traumatic stress disorder (PTSD) and the ES.
International studies [7][8][9] reveal a high readmission rate for individuals with ICD and the extent to which this phenomenon adversely impacts on the patients' quality of life.It is necessary to better understand both variables involved and determining factors for hospitalization so that strategies can be planned in order to prevent/ reduce them, reduce morbidity and mortality and improve the quality of life of post-implanted patients.
The scarce production in this line of research is also noticeable in regional and national hospitals, which elicits the need for this study to be developed.This study aims to describe the clinical characteristics of chagasic patients with ICD, who are hospitalized for clinical and/or surgical treatment of possible complications.
As for hospitalizations, 75 (86.66%)patients had zero to three hospitalizations before the latest admission; 9 (12.0%)patients had three to six hospitalizations, and only 1 (1.33%) had more than six hospitalizations before the latest admission (Table 1).The reasons for the current admission were: 45 (60.0%) patients were admitted due to clinical reasons, and 30 (40.0%) due to surgical reasons.
In  17 (56.66%)hospital admissions out of those for surgical reasons (n=30) were due to battery depletion.The remaining ones were due to device settings and/or repair: 3 (10.0%)were due to increase in the shock electrode threshold; 2 (6.66%) due to electrode breaking; 2 (6.66%) due to electrode displacement; 2 (6.66%) due to implantation of the third electrode in the left ventricle; 2 (6.66%) due to increase in the shock electrode impedance (Figure 2).

Discussion
Seventy-six percent of the patients studied were male: a result similar to that observed in a research 10 based on 1,609 Danish records of patients with CDI.The authors pointed out the male gender as a risk factor for appropriate shocks and inappropriate therapies, although they did not find any possible explanations for this characteristic.
Antiarrhythmic drugs alter cardioversion and defibrillation thresholds, which may influence shock impacts on the myocardium 10 .In this study, 58 (77.33%) patients were being treated with a combination of antiarrhythmic drugs and beta-blockers.The OPTIC 11 study, in which 412 patients with CDI were randomly sampled for therapies using beta-blockers, combined amiodarone and beta-blocker or sotalol therapy alone, revealed that within a one-year follow-up period, amiodarone and beta-blocker combined was the most effective therapy to reduce ICD shocks.The incidence of shocks in the beta-blocker group was 38.5%; 24.3% in the sotalol group, and 10.3% in the combined amiodarone/beta-blocker group.
LVEF is an important parameter to predict hospital readmission, as well as the functional classification of the New York Heart Association (NYHA).In relation to this parameter, 29 (38.67%)patients, from among 35-45%, had LVEF, followed by 24 (32.0%)patients with rates < 35%, and 22 (29.33%)patients with rates > 45%.These numbers were expected, as decompensated heart failure was the leading clinical cause of hospital admissions, accounting for 32.5% of the clinical readmissions.
This factor was assessed in another study 7 that monitored 133 patients with CDI, from 1999 to 2003.The authors found that the average number of hospitalizations unrelated to arrhythmia was significantly higher in patients suffering from LVEF: <30% (p=0.019).Functional class III patients had a cardiac-related hospitalization rate higher than those in NYHA class I or II (p=0.010 and p=0.038, respectively).The authors found no correlation between time for the first hospitalization and age, LVEF or NYHA functional class.Only LVEF <30% behaved as an independent risk factor for readmissions unrelated to arrhythmia.
In a study 10 conducted in 2013, a correlation was found between LVEF and risk for ICD-delivered therapies and mortality.The authors noticed that patients with LVEF <25% were at increased risk of inappropriate therapy, which is also associated with a higher mortality rate as compared to patients with LVEF ≥25% and patients aged ≥65.
In this study, 17% of patients had a third electrode in the left ventricle for resynchronization.This is in line with data published in a large study 12 13 showed an association between increased mortality after appropriate shocks and clinical conditions: urea>25 mg/dL, absence of beta-blockers, advanced NYHA functional class, presence of AF and DM.
In this study, most hospitalizations (60.0%) were secondary to clinical complications and 40.0% were due to surgical reasons.Regarding clinical hospitalizations, those due to cardiac reasons are the most prevalent, accounting for 88.88% of hospital admissions, being HF the leading cause (32,5%), followed by ES (30.0%); appropriate shocks (17,5%), device failure to deliver therapy (10.0%), and secondary to phantom shocks (10.0%).A similarity is observed between the data obtained in the research and the findings published in the literature, 7,8 which demonstrates that cardiac complications are the leading cause of hospitalization in patients with ICD.
Regarding surgical hospitalizations, the following are the leading causes: battery depletion (57,0%), increase in the shock electrode threshold (10.0%); electrode breaking (7,0%); electrode displacement (7,0%); implantation of the third electrode in the left ventricle (7,0%), and increase in shock electrode impedance (7,0%).It is noteworthy that all patients with electrode breaking had inappropriate shocks as clinical manifestation.It can be seen that the leading cause of surgical readmission was secondary to battery depletion.The research 8 also found similar values in 19.0% of readmissions secondary to battery depletion.About 60.0% of failures of epicardial electrodes are asymptomatic and diagnosed either by failure in defibrillation after spontaneous or induced VT or by the abnormalities shown on radiographs evidencing electrode breaking 12 .
Approximately 85.0% of the patients studied here are patients with dual-chamber ICD.A recent study 10 showed a twofold increase in the risk of shocks and inappropriate therapies associated with dual-chamber ICDs, as compared to single-chamber ICDs.Conversely, the literature 9 mentions a multicentric study in which comparison was made between single-chamber and dual-chamber detection algorithms.In that study, SVT occurred frequently (34.0% of patients) within six months after ICD implantation.Devices with single-chamber discriminators were found to have improperly classified 40.0% of the SVT episodes.On the other hand, dualchamber discriminators showed to have caused a significant reduction in the inappropriate detection rate, by 31.0%, and ICD shocks by half.Another study 8 also points out dual-chamber systems as a potential manner to reduce the incidence of readmission in patients who require chronic stimulation.
During analysis of 148 patients with CDI, by using multivariate Cox regression model, a study 14 showed that the only independent predictor of inappropriate shock was the atrial fibrillation history, and significant univariate predictors of mortality were age ≥70 and LVEF <40%.However, a research found that in addition to atrial fibrillation, information such as smoking history, occurrence of an appropriate shock and high diastolic blood pressure at the measurement moment (≥80 mmHg) are predictors of inappropriate shock 15 .
In this study, 17.5% of clinical hospitalizations occurred after appropriate shocks, i.e., patients had VT and ICD delivered the appropriate therapy; 10% of hospitalizations were secondary to shock-free VT, i.e., device failure to deliver the therapy.A similar topic was addressed in another study 7 conducted in 2006, in which authors studied 133 patients with ICD and concluded that sustained ventricular tachyarrhythmia with appropriate therapy accounted for 30.0% of hospital readmissions, whereas ICD failure to deliver therapy accounted for 2%.It is therefore clear that authors found a higher hospitalization rate due to appropriate therapies for this study, and treatment failure rates were slightly higher in this study, accounting for 5.33% of all hospital readmissions.
The importance of a modern and individualized device setting has already been announced by several studies.The use of various antitachycardia pacing (ATP) therapies before shock application has reduced shock and mortality incidence, as compared to conventional setting by using a shock-only ICD therapy.These observations were confirmed by the MADIT-RIT (Multicenter Automatic Defibrillator Implantation Trial Reduce Inappropriate Therapy) study, which observed reduction in both inappropriate shocks (80.0%) and mortality (55.0%) rates caused by the resetting of the device. 10The authors 10 report about the ease of access to ICD implantation for primary prevention of sudden death in Denmark and, since January 2007, the use of ICD for primary prevention is offered to all patients with left ventricular dysfunction and ischemic heart disease.In Brazil, by contrast, CDI implants for primary prevention are not yet authorized nor provided by the Department of Health/Brazilian Unified Healthcare System (SUS), except for by large hospitals.The major challenge faced in Brazil and worldwide is to find more accurate stratification methods associated with cheaper and all the more durable CDI devices, in order to increase the number of people benefited from a reasonable cost-effectiveness ratio 16 .
ES was present in 30.0% of clinical admissions and in 16.0% of all admissions.This syndrome increases the risk of death within the three subsequent months by more than fivefold. 13For patients who either fail to respond to pharmacological control or remain in incessant VT, endocardial catheter ablation becomes an effective therapeutic measure, as demonstrated in a study 11 that evaluated hemodynamically stable patients with only one VT morphology registered; the acute success rate after ablation was 74.0%, and within the two-year average follow-up period, 80.0% of patients were clinically free from VT recurrence.Within a one-year follow-up period, the monthly frequency of shocks, after successful ablation, decreased from 60 by 0.1.In cases of treatment failure after the use of antiarrhythmic drugs and catheter ablation, patients can benefit from resynchronization therapy with either the left ventricular assistance device or heart transplantation.
Patients in whom HF is the leading clinical cause for hospital admissions, associated with shock development, the long-term monitoring should involve close surveillance throughout the following year of signs and symptoms of imminent decompensated HF.During this time period, special monitoring of recurrent AF (particularly in patients who received inappropriate shocks), as well as titration of antiarrhythmic drugs and beta-blockers to determine the correct dosage, should be performed.Poor prognosis after shocks justifies aggressive surveillance of these patients, including a combination of more frequent clinical encounters, adjustment to HF treatment, in addition to periodic inspections of the device.
The descriptive method used limited this study to the extent that it did not allow specific conclusions to be drawn, as hypotheses were impossible to be developed.

Conclusion
The clinical profile of patients with chronic Chagas disease with CDI was the following: male, aged 51-60, presence of dual-chamber devices, adequate use of antiarrhythmic drugs and beta-blockers, presence of systemic hypertension (SH), left ventricular ejection fraction (LVEF) between 35-45%, clinical admissions due to cardiac causes (particularly HF and ES), and zero and three post-implantation admissions.

Figure 1
Figure 1 Cardiac causes for hospitalization (approximate values) ES -electrical storm; CHF -congestive heart failure

Figure 2
Figure 2 Cardiac causes for hospitalization (estimated values)

Figure 3
Figure 3Clinical and surgical procedures (estimated values)

Table 1 Clinical characteristics of patients
SH -systemic hypertension; COPD -chronic obstructive pulmonary disease Profile of Chagasic Patients with ICD Int J Cardiovasc Sci.2015;28(1):35-41 Original Manuscript New, more comprehensive works, involving other ICD implantation referral hospitals, are needed, especially given the highly prevalent Chagas disease in the Midwest Region of Brazil and the predominant cardiac manifestation of the disease in the population of Goiás state.Profile of Chagasic Patients with ICD Int J Cardiovasc Sci.2015;28(1):35-41 Original Manuscript