INTRODUCTION

The bioelectrical impedance analysis (BIA) has been described since the 1970s as a body composition assessment method based on the opposition of the biological environment to the alternating electric current, determined by the resistance (R) and reactance (Xc) components^[1,2]. It has been used both in healthy individuals and in some clinical situations, such as malnutrition, trauma, pre- and post-surgical period, liver disease, kidney failure, and heart disease^[3-5]. It stands out by its applicability at bedside due to the practicality of the method, compared to other body composition techniques^[6].

Cardiac implantable electronic devices (CIEDs) have been used in clinical practice for about five decades. Pacemaker (PM) is used to treat clinically significant bradyarrhythmia. Implantable cardioverter defibrillator (ICD) is used in primary and secondary prevention of sudden cardiac death. In patients with heart failure (HF), ICD and cardiac resynchronization therapy (CRT) can be used, individually or combined (CRT defibrillator [CRT-D)]^[7-10].

The body composition analysis through BIA assessment is not recommended for CIEDs carriers because it can cause an interference on the devices due to the applied electric current^[11]. However, the small magnitude of the current sent to the body is way inferior to the susceptibility limits of the devices, such as PM and ICD. Still, there is an absence of information on the devices’ manuals about the use of BIA in CIEDs carriers.

In addition, the protocols for BIA assessment demand attention to the presence of metallic objects in order to avoid conduction of the electric current and erroneous results^[11], which could be relevant to CIEDs carriers. Considering the limited amount of thorough detailed safety analyses, it is recommended to avoid applying body impedance methods in these cases^[12]. This limitation may influence not only the benefits that BIA could provide for these patients, such as prognosis and body composition, but also the exclusion of this potentially critical population from analyses of body composition and mortality. This study investigated the dual interference between CIEDs and BIA.

METHODS

RESULTS

The sample consisted of 43 individuals, most were male and Caucasian, mean age was 66 ± 10 years, and 39% of them presented HF (Table 1).

Table 1 - Characteristics of the study population (n=43).

Twenty-two patients had PM implanted, 15 had an ICD, and six had CRT-D. Implanted CIEDs were manufactured by Medtronic (n=27) and Biotronik (n=16) (Table 2).

Table 2 - Characteristics of the devices implanted in the study sample.

Regarding variations in anthropometric and BIA measurements, weight, BMI, PA, BCM, and ICW showed no difference between the first assessment, without the implanted device, and the second, with the implanted device. However, there were significant reductions (before and after CIEDs implantations) in direct BIA measurements (R, R/H, Xc, Xc/H), reflecting an increase (+ 1 kg) in results of TBW (L) and ECW (L) and, consequently, increases in FFM (kg) and ECM (kg). Because of changes in the hydration status and FFM values, without changes in weight, FM was significantly lower (Table 3). All of these variants were approximately 1.36% of the patients' weight, being within the possible margin of error, referring to the protocol to make the examination, especially if they were changes in hydration status.

Table 3 - Comparison of the anthropometric variables and the derived variables from BIA before and after CIEDs implantation.

The impact of BIA assessment on CIEDs showed no electrical interference on intracardiac electrogram of any lead (atrial, right ventricular, left ventricular), in any patient. There was no inappropriate sensing or tachycardia detection in any device. Full interrogation of CIEDs after BIA showed no significant differences in lead parameters or device function (Table 4). No patient presented symptoms during BIA.

Table 4 - Comparison between the CIEDs parameters before and after the examination using BIA.

DISCUSSION

In our study, BIA with Biodynamics 450 (Biodynamics Corp. Seattle, Washington, USA) in patients with CIEDs was safe and not associated with any device malfunction. We did not find presence of electrical interference on intracardiac electrogram of any lead (atrial, right ventricular, left ventricular) in any patient. With respect to BIA measurements, the significant variations were related to body water and were within the margin of error of the examination.

Since this is a fast, safe, and non-invasive method, with a relatively low cost, the BIA assessment has been used to estimate the body composition and the nutritional status of healthy individuals and patients^[1,16]. Nowadays, its prognostic use has been studied through PA, and a possible correlation between low PA values and mortality has been observed in patients with heart disease^[4,17].

Concerning the interference of BIA on CIEDs, the same findings were observed by Buch et al.^[18], while performing BIA at the frequencies of 5, 50, and 500 kHz in 20 individuals with HF. No evidence of interference with ICD function was seen in any patient, including no telemetry disruption, no oversensing on any lead, and no patient symptoms. In another larger study (n=63), which also found no electromagnetic interferences in ICDs, the authors conclude on the safety of this procedure and recommend that the current guidelines should be updated^[19]. Recently, a study of the findings corroborated the results, in an analysis of 200 individuals, indicating that the use of BIA is safe in patients with cardiac devices^[20].

Despite no interferences being observed on the devices in these previous studies^[18,19], they did not assess the BIA parameters, which can also suffer interferences, since they are wrapped by a metallic housing. The instructions regarding the use of BIA include the removal of metallic objects, attention so that the patient is not in contact with metallic structures and, if there is presence of any sort of prosthesis, BIA examination must be on the opposite side in order to avoid conduction of the electric current^[11].

In BIA measurements, an increment in TBW was observed, which may have occurred by an increase in the hydric volume due to the conditions in the hospital stay, such as saline solution administration after the procedure, and other external factors. This increase in TBW value seems to have been due to the increase in ECW (P<0.001) and for this reason there was no change in FFM (which contains large amounts of ICW ~73%). Another measure of BIA affected by hydration was the ECM, that reflects all the metabolically inactive (non-living) parts of the body, including water contained outside living cells. Still, since resistance values (R and R/H) correlate highly with fluid balance, by facilitating the passage of the electric current, the increase of TBW can impact in the reduction of R and R/H^[21]. Similar results were found by Pinto et al.^[22] in 62 patients with an indication for PM or defibrillator implantation, and they concluded that decrease in resistance and related parameters were associated to hydration status^[2]. This limitation may influence not only the benefits that BIA could provide for these patients, such as prognosis and body composition, but also the exclusion of this potentially critical population from analyses of body composition and mortality. This study analyzed the dual interference between CIEDs and BIA^[22].

A reduction in reactance values (Xc and Xc/H), reflecting tissue (not water) changes or the absorption of electrical current in tissues, was also demonstrated in our study, and this reflected in the reduction of the calculated measurement in BIA of FM.

Our study has some possible limitations that need to be considered. Our sample was relatively small, and we studied only a single BIA system in patients with CIEDs of two manufacturers. Considering these, our results cannot be applied to all patients with CIEDs or to different BIA systems. Another limitation is the variability of the evaluation time between the first and second BIA. This interval might have influenced the body composition of the individuals, as it was observed in the FM and TBW outcomes, in which case CIEDs might not have influenced this finding.

CONCLUSION

In our study, BIA assessment in patients with CIEDs was safe and not associated with any device malfunction. The differences in BIA measurements might have occurred because of modifications on the patients’ body composition, caused by their hydration status, and not by the CIEDs’ presence. Further larger studies are required to confirm these findings and to determine a change in guidelines and manufacturer’s recommendations.