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Linear and nonlinear characteristics of heart rate time series in obesity and during weight-reduction surgery.
Physiol Meas. 2009 Jul; 30(7):541-57.PM

Abstract

Obesity is associated with abnormal cardiac regulation by the autonomic nervous system (ANS), this being reversed by weight loss. Bariatric (weight-reduction) surgery can induce substantial long-term weight reductions. This study compares the acute influence on ANS control of two different types of bariatric surgery involving laparascopic and open procedures. To distinguish between the cardiac influences of surgery and obesity, we perform the same analysis for laparascopic surgery in non-obese patients. Eight morbidly obese and five non-obese patients underwent surgery. Obese patients received either laparoscopic procedures (group A: n = 5, BMI = 44.3 +/- 2.7 kg m(2)) or open procedures (group B: n = 3, BMI = 55.2 +/- 4.5 kg m(2)) and non-obese patients received a laparoscopic procedure (group C: n = 5, BMI = 30.8 +/- 5.8 kg m(-2)). Holter ECG was recorded and heart rate variability (HRV) was quantified together with measures of complexity (sample entropy) and structure (Hurst coefficient, scaling coefficient) of the heart rate data. Multifractal characteristics of heart rate data, not previously reported for obese patients, are also quantified and interpreted. Mixed model ANOVA was used to assess the magnitudes of each quantified variable, with surgical group and perioperative time as main factors. HRV measures were influenced only during anaesthesia (LFn increase: p = 0.009; HFn decrease: p = 0.033) and did not discriminate between patient groups. Multifractality was the only characteristic of heart rate data that discriminated between patient groups, being significantly (p < 0.001) greater in non-obese (group C) compared with obese patients (groups A and B, who had similar multifractal properties). Multifractality was also enhanced during anaesthesia (p = 0.028) but did not differ for other stages. We conclude that obesity per se rather than response to surgery is the cause of reduced multifractality. Reduced multifractality in obesity might reflect a diminished 'scaling' or 'collective response' across the multiple autonomic modulators of heart rate. The multifractal method appears to be a more sensitive measure of integrated cardiac autonomic function than linear methods for these patients.

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Publisher Full Text (DOI)

Authors+Show Affiliations

Alam I
Department of Surgery, Morriston Hospital, Swansea, UK.
Lewis MJ
No affiliation info available
Morgan J
No affiliation info available
Baxter J
No affiliation info available

MeSH

AdultBiliopancreatic DiversionElectrocardiographyFemaleGastric BypassHeart RateHumansMaleMiddle AgedObesityTime FactorsWeight Loss

Pub Type(s)

Journal Article

Language

eng

PubMed ID

19458410

Citation

Alam, I, et al. "Linear and Nonlinear Characteristics of Heart Rate Time Series in Obesity and During Weight-reduction Surgery." Physiological Measurement, vol. 30, no. 7, 2009, pp. 541-57.
Alam I, Lewis MJ, Morgan J, et al. Linear and nonlinear characteristics of heart rate time series in obesity and during weight-reduction surgery. Physiol Meas. 2009;30(7):541-57.
Alam, I., Lewis, M. J., Morgan, J., & Baxter, J. (2009). Linear and nonlinear characteristics of heart rate time series in obesity and during weight-reduction surgery. Physiological Measurement, 30(7), 541-57. https://doi.org/10.1088/0967-3334/30/7/002
Alam I, et al. Linear and Nonlinear Characteristics of Heart Rate Time Series in Obesity and During Weight-reduction Surgery. Physiol Meas. 2009;30(7):541-57. PubMed PMID: 19458410.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Linear and nonlinear characteristics of heart rate time series in obesity and during weight-reduction surgery. AU - Alam,I, AU - Lewis,M J, AU - Morgan,J, AU - Baxter,J, Y1 - 2009/05/21/ PY - 2009/5/22/entrez PY - 2009/5/22/pubmed PY - 2009/9/16/medline SP - 541 EP - 57 JF - Physiological measurement JO - Physiol Meas VL - 30 IS - 7 N2 - Obesity is associated with abnormal cardiac regulation by the autonomic nervous system (ANS), this being reversed by weight loss. Bariatric (weight-reduction) surgery can induce substantial long-term weight reductions. This study compares the acute influence on ANS control of two different types of bariatric surgery involving laparascopic and open procedures. To distinguish between the cardiac influences of surgery and obesity, we perform the same analysis for laparascopic surgery in non-obese patients. Eight morbidly obese and five non-obese patients underwent surgery. Obese patients received either laparoscopic procedures (group A: n = 5, BMI = 44.3 +/- 2.7 kg m(2)) or open procedures (group B: n = 3, BMI = 55.2 +/- 4.5 kg m(2)) and non-obese patients received a laparoscopic procedure (group C: n = 5, BMI = 30.8 +/- 5.8 kg m(-2)). Holter ECG was recorded and heart rate variability (HRV) was quantified together with measures of complexity (sample entropy) and structure (Hurst coefficient, scaling coefficient) of the heart rate data. Multifractal characteristics of heart rate data, not previously reported for obese patients, are also quantified and interpreted. Mixed model ANOVA was used to assess the magnitudes of each quantified variable, with surgical group and perioperative time as main factors. HRV measures were influenced only during anaesthesia (LFn increase: p = 0.009; HFn decrease: p = 0.033) and did not discriminate between patient groups. Multifractality was the only characteristic of heart rate data that discriminated between patient groups, being significantly (p < 0.001) greater in non-obese (group C) compared with obese patients (groups A and B, who had similar multifractal properties). Multifractality was also enhanced during anaesthesia (p = 0.028) but did not differ for other stages. We conclude that obesity per se rather than response to surgery is the cause of reduced multifractality. Reduced multifractality in obesity might reflect a diminished 'scaling' or 'collective response' across the multiple autonomic modulators of heart rate. The multifractal method appears to be a more sensitive measure of integrated cardiac autonomic function than linear methods for these patients. SN - 0967-3334 UR - https://www.unboundmedicine.com/medline/citation/19458410/Linear_and_nonlinear_characteristics_of_heart_rate_time_series_in_obesity_and_during_weight_reduction_surgery_ L2 - https://doi.org/10.1088/0967-3334/30/7/002 DB - PRIME DP - Unbound Medicine ER -