Methods
A Multicenter Study of Noninvasive Cardiac Output by Bioreactance During Symptom-limited Exercise

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Abstract

Background

Hemodynamic responses to exercise were assessed in patients with varying degrees of chronic heart failure (CHF) to determine the feasibility of using bioreactance during exercise testing in multicenter studies of CHF.

Methods and Results

A total of 210 symptomatic CHF patients and 22 subjects without heart failure were subjected to symptom-limited exercise testing on a bicycle (105) or treadmill (127) while measuring gas exchange for VO2, cardiac output (CO) noninvasively by a bioreactance technique, heart rate, and blood pressure. Peak CO (pCO) and VO2 (pVO2) during exercise were lower in patients with higher New York Heart Association (NYHA) class, in females and in older patients. Multiple linear regression analysis showed that pCO (L/min) = 19.6 + 4·M – 2.1·NYHA + 1.9·G – 0.09·Age, where M = 1 for treadmill and 0 for bicycle and G = 1 for males and 0 for females. Similarly, pVO2 (mL/kg/min) = 24 + 2.1·M – 2.9·NYHA + 1.26·G – 0.08·Age. VO2 and CO were also highly correlated to each other: pCO (mL/kg/min) = 0.059 + 0.007·pVO2 + 0.036·M – 0.025·G. Similar correlations were determined for other parameters of exercise, including left ventricular power, and the ratio of peak/resting VO2 (cardiovascular reserve), the ratio of peak/resting CO (cardiac reserve), and total peripheral vascular resistance.

Conclusion

Bioreactance-based noninvasive measurements of CO at rest and during exertion identified abnormalities of cardiovascular function consistent with those identified by pVO2 and in prior studies using invasive CO measurements. This technique might therefore be useful for indexing disease severity, prognostication, and for tracking responses to treatment in clinical practice and in clinical trials.

Section snippets

Methods

Basic demographic data and medical history were obtained from 232 subjects referred for stress testing at 4 institutions. The medical history included the primary clinician's assessment of New York Heart Association (NYHA) functional classification. This study was approved by each Institutional Review Board and all subjects gave written informed consent to participate. The only inclusion criterion was that each subject was already referred for a stress test; a small group of patients (n = 22)

Results

Typical NICOM signals obtained at rest, approximately halfway to peak exercise, and at peak exercise from a test performed during treadmill testing are shown in Fig. 1. All tracings, including 3 leads of an electrocardiogram, the NICOM phase signal (Φ(t)), and the first derivative of phase (dΦ(t)/dt)) represent signals that were averaged over a 1-minute period. With increasing amounts of exercise, heart rate increases, the peak-to-peak amplitude of the Φ(t) signal increases (indicating increase

Discussion

The present study, performed in a relatively large number of patients, demonstrates that CO can readily be measured at rest and throughout symptom limited treadmill or bicycle exercise using the bioreactance technique in patients with heart failure spanning a wide range of NYHA classes recruited from multiple centers. The physiologic information obtained about heart failure conforms well with data from several prior studies in which CO was measured invasively and reinforces the concept that

Summary and Conclusions

In summary, using the bioreactance-based noninvasive measurements of CO at rest and at peak exertion, we identified NYHA class-dependent pathophysiologic abnormalities of cardiovascular function consistent with those identified in prior studies using invasive methods of CO measurement.4, 5 These consisted of NYHA class-dependent limitations in ability to increase CO because of both chronotropic incompetence and inability in increase SV during symptom-limited exercise as well as class-dependent

Acknowledgments

The authors are grateful for the superb administrative assistance of Amanda Milgram.

References (43)

  • P. Agostoni et al.

    Noninvasive measurement of cardiac output during exercise by inert gas rebreathing technique: a new tool for heart failure evaluation

    J Am Coll Cardiol

    (2005)
  • J.R. Wilson et al.

    Use of maximal bicycle exercise testing with respiratory gas analysis to assess exercise performance in patients with congestive heart failure secondary to coronary artery disease or to idiopathic dilated cardiomyopathy

    Am J Cardiol

    (1986)
  • M. Botero et al.

    Measurement of cardiac output before and after cardiopulmonary bypass: comparison among aortic transit-time ultrasound, thermodilution, and noninvasive partial CO2 rebreathing

    J Cardiothorac Vasc Anesth

    (2004)
  • J.S. Chan et al.

    Measurement of cardiac output with a non-invasive continuous wave Doppler device versus the pulmonary artery catheter: a comparative study

    Crit Care Resusc

    (2006)
  • J. Myers

    Applications of cardiopulmonary exercise testing in the management of cardiovascular and pulmonary disease

    Int J Sports Med

    (2005)
  • R. Arena et al.

    Ventilatory abnormalities during exercise in heart failure: a mini review

    Current Resp Med Rev

    (2007)
  • D.M. Mancini et al.

    Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure

    Circulation

    (1991)
  • K.T. Weber et al.

    Cardiopulmonary exercise testing for evaluation of chronic cardiac failure

    Am J Cardiol

    (1985)
  • K.T. Weber et al.

    Oxygen utilization and ventilation during exercise in patients with chronic cardiac failure

    Circulation

    (1982)
  • I.L. Pina et al.

    Exercise and heart failure: a statement from the American Heart Association Committee on exercise, rehabilitation, and prevention

    Circulation

    (2003)
  • T.D. Noakes

    Maximal oxygen uptake: “classical” versus “contemporary” viewpoints: a rebuttal

    Med Sci Sports Exerc

    (1998)
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    Supported by a grant from Cheetah Medical. D. Burkhoff and J. Myers are consultants to Cheetah Medical.

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