Heart Rate Variability in Individuals With Duchenne Muscular Dystrophy
Condition: Duchenne Muscular Dystrophy
MeSH terms: Muscular Dystrophies; Muscular Dystrophy, Duchenne
Study type: Observational

Summary: 
      A cross-sectional study was carried out, in which 40 boys, aged 11 to 18 years, were
      evaluated. The recruitment of groups was carried out at the neuromuscular disease outpatient
      clinic of the Federal University of São Paulo (UNIFESP). The recruited individuals were
      divided into 4 groups, namely: DMD that used deflazacort (DMD-D); DMD that used
      Prednisone/Prednisolone (DMD-P); DMD Control with no corticoid use (DMD-C) and Controls with
      typical development (CTD). The protocol was applied during the evaluation that was carried
      out at outpatient follow-up visits.

      To assess the functionality of each patient, the Vignos scales were used to characterize the
      sample and the Motor Function Measure (MFM) for association with HRV indices.

      All heart rate records were performed using a cardiofrequencymeter (V800, Polar). After
      placing the brace and monitor, the individuals were placed in the supine position and
      remained at rest spontaneously breathing for 25 minutes. For HRV analysis, indexes obtained
      by linear methods, in the domain of time and frequency, and non-linear methods were used.
    

Detailed description: 
      A cross-sectional study was carried out, in which 40 boys, aged 11 to 18 years, were
      evaluated. The recruitment of groups was carried out at the neuromuscular disease outpatient
      clinic of the Federal University of São Paulo (UNIFESP). The recruited individuals were
      divided into 4 groups, namely: DMD that used deflazacort (DMD-D) with n=11; DMD that used
      Prednisone/Prednisolone (DMD-P), with n=9; DMD Control with no corticoid use (DMD-C), and
      n=10 and Controls with typical development (CTD) with n=10. The protocol was applied during
      the evaluation that was carried out at outpatient follow-up visits. Anthropometry was
      analyzed in 4 groups and functionality was assessed in 3 groups with DMD. To assess the
      functionality of each patient, the Vignos scales were used to characterize the sample and the
      Motor Function Measure (MFM) for association with HRV indices.

      Initially, the resting ECG was analyzed to verify the existence of sinus rhythm and to
      exclude individuals with arrhythmias and blocks. The measurements at rest were performed
      immediately before and after the HRV assessment, including systolic (SBP) and diastolic
      (DBP), heart rate (HR), Respiratory Rate (RF - blood pressure) to ensure that at the
      beginning and at the end of the collection FR remains between 9 - 24rpm, in the range of 0.15
      - 0.40Hz) and partial oxygen saturation (SO2). Heart rate was recorded by the cardiofrequency
      meter (RS800CX, Polar). And the partial oxygen saturation by means of a digital oximeter
      (DX2010, Dixtal) connected to the participant's index finger or hallux, through a sensor of
      age-appropriate size, in room air. Hemoglobin saturation by oxygen was recorded after the
      first minute of stabilization, as the value that remains most constant during the second
      minute.

      All heart rate records were performed using a cardiofrequencymeter (V800, Polar). After
      placing the brace and monitor, the individuals were placed in the supine position and
      remained at rest spontaneously breathing for 25 minutes. For HRV analysis, indexes obtained
      by linear methods, in the domain of time and frequency, and non-linear methods were used.

      In the time domain, for linear analyses, each normal RR interval (sinus beats) was verified
      during a certain time interval and, using statistical and non-linear methods, the translating
      indexes of fluctuations in the duration of the cardiac cycles were calculated. With this, the
      indices expressed in ms were obtained: SDNN (Standard deviation of the normal RR intervals
      recorded in a time interval); rMSSD (square root of the mean of the square of the differences
      between adjacent normal RR intervals in a time interval).

      In the frequency domain, the spectral power density is more used, mainly when treating
      individuals in resting conditions. This analysis divides HRV into fundamental oscillatory
      components, which were used the main: High Frequency normalized unite (HFnu) component and
      Low Frequency normalized unite (LFnu) component. O algoritmo utilizado para a análise
      espectral foi a transformada rápida de Fourier - FFT (janela de 256 s com 50% de overlap).

      Among the nonlinear methods used for HRV analysis, we can mention the Detrended Fluctuations
      Analysis (DFA), Visual Recurrence Analysis (VRA) and symbolic analysis (SA), the three of
      which were verified in this study.

      DFA is used to quantify the fractal property of RR interval time series, being used to detect
      possible abnormalities present in a subject, based on α coefficients. For this, short memory
      parameters α1, which corresponds to a period of 4 to 11 beats, and long memory α2, which
      corresponds to the period from 64 to 1024 beats, were used.

      The VRA is used to study the time dependence of a series, that is, in the study of
      stationarity35. The recurrence graph makes it possible to visualize the behavior of
      trajectories in the phase space and, in addition, to show the times in which a state of a
      dynamic system is repeated, besides these factors can be confirmed regarding the quantitative
      analysis of this, wich presents such indices: Mean, SD, PerRec, PerDet, PerLam, TrapTim,
      Ratio.

      The evaluation of the symbolic analysis is based on the quantification of the information
      carried in a time series, in the transformation of the previously selected iRRs into integers
      from zero to six, from which sequences of 3 symbols (symbolic patterns) are constructed. For
      this, all possible patterns will be grouped according to the number and type of variations
      between the symbols, shown subsequently. The patterns were (1) patterns, without variation
      (0V), three identical symbols; (2) patterns with a variation (1V), that is, two subsequent
      symbols that are the same and a different one; (3) patterns with two similar variations (2LV)
      that is, the three symbols form a ramp; (4) patterns with two different variations (2ULV),
      that is, the three symbols form a peak or a valley.
    

Intervention name(s): Duchenne Muscular Dystrophy group with Deflazacort; Duchenne Muscular Dystrophy group with Prednisone/Predisolone; Duchenne Muscular Dystrophy group without Corticosteroids therapy; Control Group Typically Developing
Intervention type(s): Behavioral; Behavioral; Behavioral; Behavioral
Intervention description(s): Subjects with duchenne muscular dystrophy undergoing drug therapy with Deflazacort; Subjects with duchenne muscular dystrophy undergoing drug therapy with Prednisona/Predinisolone; Control group with duchenne muscular dystrophy without the use of corticosteroid drug therapy.; Control group with tipical development.
Intervention MeSH terms: Prednisone; Deflazacort
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        30 boys with Duchenne Muscular Dystrophy and 10 typically developing boys aged 11 to 18
        years.
      
Keywords: Muscular Dystrophy, Duchenne; Prednisone; Deflazacort