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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/H1310    most recent 01187.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ichinose, M. Articles by Iellamo, F. Search for Related Content PubMed PubMed Citation Articles by Ichinose, M. Articles by Iellamo, F.

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

Departments of ¹Physiology and ²Surgery, Wayne State University School of Medicine, Detroit, Michigan; ³Laboratory for Applied Human Physiology, Faculty of Human Development, Kobe University, Kobe, Japan; ⁴Laboratory for Human Performance Research, Osaka International University, Osaka, Japan; and ⁵Dipartimento Medicina Interna, Universita di Roma Tor Vergata, and ⁶Instituto di Ricovero e Cura a Carattere Scientifico San Raffaele Pisana, Roma, Italy

Submitted 11 October 2007 ; accepted in final form 16 December 2007

We 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 (–3.08 ± 0.5 vs. –5.14 ± 0.6 beats·min^–1·mmHg^–1; P < 0.05) and CO-LVSP (–134.74 ± 24.5 vs. –208.6 ± 22.2 ml·min^–1·mmHg^–1; P < 0.05). Moderate exercise further decreased both and, in addition, significantly reduced HR-CO translation (25.9 ± 2.8% vs. 52.3 ± 4.2%; P < 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