Clinical Investigation
Right and Left Ventricular Function
Left Ventricular Adaptation to Acute Hypoxia: A Speckle-Tracking Echocardiography Study

https://doi.org/10.1016/j.echo.2013.04.012Get rights and content

Background

Hypoxia depresses myocardial contractility in vitro but does not affect or may even improve indices of myocardial performance in vivo, possibly through associated changes in autonomic nervous system tone. The aim of this study was to explore the effects of hypoxic breathing on speckle-tracking echocardiographic indices of left ventricular function, with and without β1-adrenergic inhibition.

Methods

Speckle-tracking echocardiography was performed in 21 healthy volunteers in normoxia and after 30 min of hypoxic breathing (fraction of inspired oxygen, 0.12). Measurements were also obtained after the administration of atropine in normoxia (n = 21) and after bisoprolol intake in normoxia (n = 6) and in hypoxia (n = 10).

Results

Hypoxia increased heart rate (from 68 ± 11 to 74 ± 9 beats/min, P = .001), without changing mean blood pressure (P = NS), and decreased total peripheral resistance (P = .003). Myocardial deformation magnitude increased (circumferential strain, −19.6 ± 1.9% vs −21.2 ± 2.5%; radial strain, 19.2 ± 3.7% vs 22.6 ± 4.1%, P < .05; longitudinal and circumferential strain rate, −0.88 ± 0.11 vs −0.99 ± 0.15 sec−1 and −1.03 ± 0.16 vs −1.18 ± 0.18 sec−1, respectively, P < .05 for both; peak twist, 8.98 ± 3.2° vs 11.1 ± 2.9°, P < .05). Except for peak twist, these deformation parameters were correlated with total peripheral resistance (P < .05). Atropine increased only longitudinal strain rate magnitude (−0.88 ± 0.11 vs −0.97 ± 0.14 sec−1, P < .05). The increased magnitude of myocardial deformation persisted in hypoxia under bisoprolol (P < .05). In normoxia, bisoprolol decreased heart rate (73 ± 10 vs 54 ± 7 beats/min, P = .0005), mean blood pressure (88 ± 7 vs 81 ± 4 mm Hg, P = .0027), without altering deformation.

Conclusions

Hypoxic breathing increases left ventricular deformation magnitude in normal subjects, and this effect may not be attributed to hypoxia-induced tachycardia or β1-adrenergic pathway changes but to hypoxia-induced systemic vasodilation.

Section snippets

Study Population

Twenty-one participants (mean age, 27 ± 7 years) were studied in normoxia, in hypoxia, and in normoxia after atropine administration. In a second stage, 10 subjects (five of whom were new participants; mean age, 26 ± 7 years) were studied in normoxia and in hypoxia under β-blockade, and six of these subjects were also studied in normoxia under β-blockade.

Inclusion criteria were as follows: age 20 to 40 years; normal results on physical examination, 12-lead electrocardiography, and standard

Effect of Normobaric Hypoxia

Clinical characteristics of the subjects are shown in Table 1. The mean age of the subjects was of 27 ± 7 years (seven men, 14 women), and the mean body surface area was 1.73 ± 0.16 m2. Compared with normoxia, hypoxic breathing decreased SaO2 (as expected), increased HR, and did not alter BP. There was a small decrease in Pco2.

Discussion

The present results show that hypoxic breathing increases LV performance in healthy subjects and that this effect is explained by hypoxia-induced systemic vasodilation rather than by associated autonomic nervous system changes.

Conclusions

Using STE, we demonstrated an increase in LV function during acute hypoxia. The increases in the magnitudes of myocardial deformation parameters were only marginally explained by hypoxia-induced tachycardia. The increased deformation magnitude persisted in hypoxia under β-blockade, consistent with the role of an intrinsic mechanism unrelated to catecholaminergic activation and suggesting a contribution for hypoxia-induced systemic vasodilation in the observed changes in LV function.

Acknowledgments

We thank G. Deboeck and M. Lamotte for their helpful contributions.

References (49)

  • V. Mor-Avi et al.

    Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography

    J Am Soc Echocardiogr

    (2011)
  • A.T. Burns et al.

    Augmentation of left ventricular torsion with exercise is attenuated with age

    J Am Soc Echocardiogr

    (2008)
  • H. Nakai et al.

    Effect of aging on twist-displacement loop by 2-dimensional speckle tracking imaging

    J Am Soc Echocardiogr

    (2006)
  • O.A. Smiseth et al.

    Strain rate imaging: why do we need it?

    J Am Coll Cardiol

    (2003)
  • R.J. Hajjar et al.

    Direct evidence of changes in myofilament responsiveness to Ca2+ during hypoxia and reoxygenation in myocardium

    Am J Physiol

    (1990)
  • H.S. Silverman et al.

    Myocyte adaptation to chronic hypoxia and development of tolerance to subsequent acute severe hypoxia

    Circ Res

    (1997)
  • C.E. Tucker et al.

    Depressed myocardial function in the goat at high altitude

    J Appl Physiol

    (1976)
  • A. Boussuges et al.

    Operation Everest III (Comex '97): modifications of cardiac function secondary to altitude-induced hypoxia. An echocardiographic and Doppler study

    Am J Respir Crit Care Med

    (2000)
  • J. Kjaergaard et al.

    The effect of 18 h of simulated high altitude on left ventricular function

    Eur J Appl Physiol

    (2006)
  • Y. Allemann et al.

    Impact of acute hypoxic pulmonary hypertension on LV diastolic function in healthy mountaineers at high altitude

    Am J Physiol Heart Circ Physiol

    (2004)
  • W.L. Cunningham et al.

    Catecholamines in plasma and urine at high altitude

    J Appl Physiol

    (1965)
  • R. Hainsworth et al.

    The autonomic nervous system at high altitude

    Clin Auton Res

    (2007)
  • B.S. Mazzeo et al.

    Acclimatization to high altitude increases muscle sympathetic activity both at rest and during exercise

    Am J Physiol Regulat Integrat Comp Physiol

    (1995)
  • R. Tamisier et al.

    Arterial pressure and muscle sympathetic nerve activity are increased after two hours of sustained but not cyclic hypoxia in healthy humans

    J Appl Physiol

    (2005)
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    This work was supported by Fonds Erasme, Université Libre de Bruxelles (Brussels, Belgium) (Dr. Dedobbeleer); Fonds Pour la Chirurgie Cardiaque (Brussels, Belgium) (Drs. Dedobbeleer and Unger); Fonds Docteur et Madame René Tagnon (King Baudouin Foundation, Brussels, Belgium) (Dr. Dedobbeleer); and Fondation M. Horlait-Dapsens King (Brussels, Belgium) (Dr. Dedobbeleer).

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