Relação entre a oferta e a utilização muscular periférica de oxigênio na transição do exercício leve para o intenso em pacientes com insuficiência cardíaca / Peripheral muscle oxygen delivery-to-utilization mismatch in the transition from mild to heavy-intensity exercise in patients with CHF

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

24/11/2010

RESUMO

Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O2 pressure and decrease the rate of O2 transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e.g., angiotensin-converting enzyme inhibitors and third generation of â-blockers) may have improved microvascular O2 delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O2 uptake ( O2) kinetics. We included 10 optimally treated sedentary patients (ejection fraction = 29 8%) and 11 age-matched controls. We assessed the rate of change of pulmonary O2 ( O2p), tissue O2 extraction in the vastus lateralis estimated by concentration of deoxy-hemoglobin+myoglobin (~Ä[deoxy-Hb+Mb]) measured by near-infrared spectroscopy (NIRS), and cardiac output ( T) during highintensity exercise performed to the limit of tolerance (Tlim). Sluggish O2p and T kinetics in patients were significantly related to lower Tlim values (P = 0.05). The dynamics of Ä[deoxy-Hb+Mb] were faster in patients than controls (mean response time (MRT) = 15.9 2.0 s vs. 19.0 2.9 s; P = 0.05) with a subsequent response overshoot being found only in patients (7/10). Moreover, t O2p/MRT-Ä[deoxy- Hb+Mb] ratio was greater in patients (4.69 1.42 s vs. 2.25 0.77 s; P = 0.05) and related to T kinetics and Tlim (R = 0.89 and 0.78, respectively; P = 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in central and peripheral circulatory adjustments still play a prominent role in limiting O2p kinetics and tolerance to heavy-intensity exercise in nontrained patients.

ASSUNTO(S)

fluxo sanguíneo insuficiência cardíaca hemodinâmica espectroscopia de raios quasi-infravermelhos cardiologia blood flow chronic heart failure hemodynamics near-infrared spectroscopy oxygen consumption cinética

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