Muscle metaboreflex attenuates spontaneous heart rate baroreflex sensitivity during dynamic exercise

Sala‐Mercado, Javier A.; Ichinose, Masashi; Hammond, Robert L.; Ichinose, Tomoko; Pallante, Marco; Stephenson, Larry W.; O’Leary, Donal S.; Iellamo, Ferdinando

doi:10.1152/ajpheart.00043.2007

Cited by 29 publications

(54 citation statements)

References 62 publications

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“…During exercise, the baroreflex is reset to operate around the higher-prevailing blood pressure and HR (7,13,26,28). In addition to resetting during exercise, arterial baroreflex sensitivity in the control of HR during rapid spontaneous changes in blood pressure decreases during exercise as workload rises (3,14,23,31). The reduction of baroreflex HR sensitivity during exercise is thought to be associated with vagal withdrawal, inasmuch as these rapid baroreflex changes in HR are mediated by changes in parasympathetic tone (23).…”

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“…The reduction of baroreflex HR sensitivity during exercise is thought to be associated with vagal withdrawal, inasmuch as these rapid baroreflex changes in HR are mediated by changes in parasympathetic tone (23). Recently, it has been demonstrated (31) in dogs that imposed muscle metaboreflex activation during dynamic exercise also reduces spontaneous baroreflex HR sensitivity, which is even further suppressed in these settings in subjects with congestive heart failure (HF) (16).…”

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Spontaneous baroreflex control of cardiac output during dynamic exercise, muscle metaboreflex activation, and heart failure

Ichinose¹,

Sala‐Mercado²,

O’Leary³

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

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Ichinose M, Sala-Mercado JA, O'Leary DS, Hammond RL, Coutsos M, Ichinose T, Pallante M, Iellamo F. Spontaneous baroreflex control of cardiac output during dynamic exercise, muscle metaboreflex activation, and heart failure. Am J Physiol Heart Circ Physiol 294: H1310-H1316, 2008. First published January 11, 2008 doi:10.1152/ajpheart.01187.2007We have previously shown that spontaneous baroreflex-induced changes in heart rate (HR) do not always translate into changes in cardiac output (CO) at rest. We have also shown that heart failure (HF) decreases this linkage between changes in HR and CO. Whether dynamic exercise and muscle metaboreflex activation (via imposed reductions in hindlimb blood flow) further alter this translation in normal and HF conditions is unknown. We examined these questions using conscious, chronically instrumented dogs before and after pacing-induced HF during mild and moderate dynamic exercise with and without muscle metaboreflex activation. We measured left ventricular systolic pressure (LVSP), CO, and HR and analyzed the spontaneous HR-LVSP and CO-LVSP relationships. In normal animals, mild exercise significantly decreased HR-LVSP (Ϫ3.08 Ϯ 0.5 vs. Ϫ5.14 Ϯ 0.6 beats ⅐ min Ϫ1 ⅐ mmHg Ϫ1 ; P Ͻ 0.05) and CO-LVSP (Ϫ134.74 Ϯ 24.5 vs. Ϫ208.6 Ϯ 22.2 ml ⅐ min Ϫ1 ⅐ mmHg Ϫ1 ; P Ͻ 0.05). Moderate exercise further decreased both and, in addition, significantly reduced HR-CO translation (25.9 Ϯ 2.8% vs. 52.3 Ϯ 4.2%; P Ͻ 0.05). Muscle metaboreflex activation at both workloads decreased HR-LVSP, whereas it had no significant effect on CO-LVSP and the HR-CO translation. HF significantly decreased HR-LVSP, CO-LVSP, and the HR-CO translation in all situations. We conclude that spontaneous baroreflex HR responses do not always cause changes in CO during exercise. Moreover, muscle metaboreflex activation during mild and moderate dynamic exercise reduces this coupling. In addition, in HF the HR-CO translation also significantly decreases during both workloads and decreases even further with muscle metaboreflex activation.arterial baroreflex sensitivity; exercise reflexes; pressor response; impaired cardiac performance THE ARTERIAL BAROREFLEX is considered the main mechanism of arterial blood pressure regulation in the short-term control of the cardiovascular system (30). Changes in arterial pressure result in baroreflex-mediated reciprocal changes in heart rate (HR) and sympathetic activity. During exercise, the baroreflex is reset to operate around the higher-prevailing blood pressure and HR (7,13,26,28). In addition to resetting during exercise, arterial baroreflex sensitivity in the control of HR during rapid spontaneous changes in blood pressure decreases during exercise as workload rises (3,14,23,31). The reduction of baroreflex HR sensitivity during exercise is thought to be associated with vagal withdrawal, inasmuch as these rapid baroreflex changes in HR are mediated by changes in parasympathetic tone (23). Recently, it has been demonstrated (31) in dogs that imposed muscle metaboreflex activation durin...

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confidence: 99%

Spontaneous baroreflex control of cardiac output during dynamic exercise, muscle metaboreflex activation, and heart failure

Ichinose¹,

Sala‐Mercado²,

O’Leary³

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

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“…Our approach that was employed to evaluate arterial baroreflex control of HR and CO (based on spontaneous fluctuations in blood pressure, HR, and CO) has several advantages and disadvantages, as discussed previously (34,35). Briefly, this approach only examines the baroreflex gain over a relatively modest range of pressure, which, therefore, does not allow the calculation of the entire, sigmoidal baroreflex stimulus-response relationship.…”

Section: Discussionmentioning

confidence: 99%

“…As workload increases, the rapid HR responses to spontaneous changes in arterial pressure progressively decrease as workload rises (3,13,23,45). A major mechanism potentially mediating the normal rise in HR and arterial pressure during exercise is the activation of the muscle metaboreflex via stimulation of chemosensitive afferents within the active muscle, which can elicit a marked pressor response (1,7,9,19,31,49) and also reduces this spontaneous baroreflex HR sensitivity (33,35), and this effect of exercise and metaboreflex activation is further exacerbated in heart failure (14). The attenuated baroreflex HR sensitivity in these conditions could have an important impact on dynamic CO regulation, especially in the Lo-F range, where the baroreflex exerts strong control over HR theoretically to protect against further blood pressure fluctuations (25, 28).…”

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Dynamic cardiac output regulation at rest, during exercise, and muscle metaboreflex activation: impact of congestive heart failure

Ichinose

Sala‐Mercado

Coutsos

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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.2012.-We tested whether mild and moderate dynamic exercise and muscle metaboreflex activation (MMA) affect dynamic baroreflex control of heart rate (HR) and cardiac output (CO), and the influence of stroke volume (SV) fluctuations on CO regulation in normal (N) and pacing-induced heart failure (HF) dogs by employing transfer function analyses of the relationships between spontaneous changes in left ventricular systolic pressure (LVSP) and HR, LVSP and CO, HR and CO, and SV and CO at low and high frequencies (Lo-F, 0.04 -0.15 Hz; Hi-F, 0.15-0.6 Hz). In N dogs, both workloads significantly decreased the gains for LVSP-HR and LVSP-CO in Hi-F, whereas only moderate exercise also reduced the LVSP-CO gain in Lo-F. MMA during mild exercise further decreased the gains for LVSP-HR in both frequencies and for LVSP-CO in Lo-F. MMA during moderate exercise further reduced LVSP-HR gain in Lo-F. Coherence for HR-CO in Hi-F was decreased by exercise and MMA, whereas that in Lo-F was sustained at a high level (Ͼ0.8) in all settings. HF significantly decreased dynamic HR and CO regulation in all situations. In HF, the coherence for HR-CO in Lo-F decreased significantly in all settings; the coherence for SV-CO in Lo-F was significantly higher. We conclude that dynamic exercise and MMA reduces dynamic baroreflex control of HR and CO, and these are substantially impaired in HF. In N conditions, HR modulation plays a major role in CO regulation. In HF, influence of HR modulation wanes, and fluctuations of SV dominate in CO variations. arterial baroreflex; exercise reflexes; pressor response; impaired cardiac performance BEAT-TO-BEAT CARDIAC OUTPUT (CO) varies considerably across successive heart beats, whereas the average level remains remarkably constant under basal conditions (21, 50). This likely involves control mechanisms operating at markedly different frequencies. Rapid baroreflex control of heart rate (HR) is thought to play a crucial role in dynamic CO regulation. Previous studies suggest that low-frequency (Lo-F: 0.04 -0.15 Hz) blood pressure fluctuations are buffered by the dynamic baroreflex control of HR (25, 28). However, we and others have observed that changes in HR do not necessarily elicit proportional changes in CO because stroke volume (SV) may also vary with the changes in ventricular filling time (17,34,48). Furthermore, transient increases in CO will lower ventricular filling pressure (and decreases in CO will raise filling pressure), thereby providing a self-limiting response (6,30,40). Furthermore, baroreflex control of HR may not functionally buffer high-frequency (Hi-F: above 0.15 Hz) blood pressure fluctuations (4,38,44). In this case, Hi-F variations of CO could facilitate blood pressure variability via a feedforward mechanism rather than buffer arterial pressure. In addition, it has been shown that in anesthetized rats, the blood pressure response to cardiac pacing induced high-frequency oscillation of CO is smaller than that to low-frequency oscillation of CO (41). To our knowledge, however, the dynam...

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“…Our approach employed to evaluate arterial baroreflex control of HR and CO (based on spontaneous fluctuations in blood pressure, HR, and CO) has several advantages and disadvantages, which have been previously described in detail (12,14,27). Briefly, on one hand, the spontaneous baroreflex technique enables a qualitative and quantitative estimate of the integrated baroreceptor-cardiac response relationships during the spontaneous blood pressure fluctuations without the necessity of any pharmacological or mechanical interventions.…”

Section: Cardiac Baroreflex Responses In Hfmentioning

confidence: 99%

Spontaneous baroreflex control of heart rate versus cardiac output: altered coupling in heart failure

Sala‐Mercado

Ichinose

Hammond

et al. 2008

American Journal of Physiology-Heart and Circulatory Physiology

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Sala-Mercado JA, Ichinose M, Hammond RL, Coutsos M, Ichinose T, Pallante M, Iellamo F, O'Leary DS. Spontaneous baroreflex control of heart rate versus cardiac output: altered coupling in heart failure. Am J Physiol Heart Circ Physiol 294: H1304-H1309, 2008. First published January 11, 2008 doi:10.1152/ajpheart.01186.2007.-Dynamic cardiac baroreflex responses are frequently investigated by analyzing the spontaneous reciprocal changes in arterial pressure and heart rate (HR). However, whether the spontaneous baroreflex-induced changes in HR translate into changes in cardiac output (CO) is unknown. In addition, this linkage between changes in HR and changes in CO may be different in subjects with heart failure (HF). We examined these questions using conscious dogs before and after pacing-induced HF. Spontaneous baroreflex sensitivity in the control of HR and CO was evaluated as the slopes of the linear relationships between HR or CO and left ventricular systolic pressure (LVSP) during spontaneous sequences of greater or equal to three consecutive beats when HR or CO changed inversely versus pressure. Furthermore, the translation of baroreflex HR responses into CO responses (HR-CO translation) was examined by computing the overlap between HR and CO sequences. In normal resting conditions, 44.0 Ϯ 4.4% of HR sequences overlapped with CO sequences, suggesting that only around half of the baroreflex HR responses cause CO responses. In HF, HR-LVSP, CO-LVSP, and the HR-CO translation significantly decreased compared with the normal condition (Ϫ2.29 Ϯ 0.5 vs. Ϫ5.78 Ϯ 0.7 beats ⅐ min Ϫ1 ⅐ mmHg Ϫ1 ; Ϫ70.95 Ϯ 11.8 vs. Ϫ229.89 Ϯ 29.6 ml ⅐ min Ϫ1 ⅐ mmHg Ϫ1 ; and 19.66 Ϯ 4.9 vs. 44.0 Ϯ 4.4%, respectively). We conclude that spontaneous baroreflex HR responses do not always cause changes in CO. In addition, HF significantly decreases HR-LVSP, CO-LVSP, and HR-CO translation.arterial baroreflex sensitivity; parasympathetic activity; stroke volume THE ARTERIAL BAROREFLEX is the primary short-term regulator of systemic blood pressure via modulation of parasympathetic and sympathetic nerve activity (26). Changes in arterial blood pressure result in arterial baroreflex-mediated reciprocal changes in heart rate (HR) and total peripheral resistance. Arterial baroreflex sensitivity (cardiac component) has often been assessed via techniques that analyze normally occurring spontaneous changes in blood pressure and the reciprocal changes in HR (3,12,21,32). This technique has been used as an index of cardiac baroreflex function in a number of species, including humans, and in many experimental and pathological conditions (1,3,11,13,18,21,25,32). Sinoaortic baroreflex denervation virtually abolishes baroreflex sensitivity assessed via this method, indicating that the spontaneous reciprocal changes in HR that occur as a result of changes in arterial pressure are indeed mediated by the baroreflex (1, 19). However, changes in HR do not necessarily dictate changes in cardiac output (CO) because stroke volume (SV) may also vary, for example, with ...

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Muscle metaboreflex attenuates spontaneous heart rate baroreflex sensitivity during dynamic exercise

Cited by 29 publications

References 62 publications

Spontaneous baroreflex control of cardiac output during dynamic exercise, muscle metaboreflex activation, and heart failure

Spontaneous baroreflex control of cardiac output during dynamic exercise, muscle metaboreflex activation, and heart failure

Dynamic cardiac output regulation at rest, during exercise, and muscle metaboreflex activation: impact of congestive heart failure

Spontaneous baroreflex control of heart rate versus cardiac output: altered coupling in heart failure

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