TY - JOUR
T1 - Mechanisms for increasing stroke volume during static exercise with fixed heart rate in humans
AU - Nóbrega, Antonio C L
AU - Williamson, Jon W.
AU - Garcia, Jorge A.
AU - Mitchell, Jere H.
PY - 1997/9
Y1 - 1997/9
N2 - Ten patients with preserved inotropic function having a dual-chamber (right atrium and right ventricle) pacemaker placed for complete heart block were studied. They performed static one-legged knee extension at 20% of their maximal voluntary contraction for 5 min during three conditions: 1) atrioventricular sensing and pacing mode [normal increase in heart rate (HR; DDD)], 2) HR fixed at the resting value (DOO-Rest; 73 ± 3 beats/min), and 3) HR fixed at peak exercise rate (DOO-Ex; 107 ± 4 beats/min). During control exercise (DDD mode), mean arterial pressure (MAP) increased by 25 mmHg with no change in stroke volume (SV) or systemic vascular resistance. During DOO- Rest and DOO-Ex, MAP increased (+25 and +29 mmHg, respectively) because of a SV-dependent increase in cardiac output (+1.3 and +1.8 l/min, respectively). The increase in SV during DOO-Rest utilized a combination of increased contractility and the Frank-Starling mechanism (end-diastolic volume 118-136 ml). However, during DOOEx, a greater left ventricular contractility (end- systolic volume 55-38 ml) mediated the increase in SV.
AB - Ten patients with preserved inotropic function having a dual-chamber (right atrium and right ventricle) pacemaker placed for complete heart block were studied. They performed static one-legged knee extension at 20% of their maximal voluntary contraction for 5 min during three conditions: 1) atrioventricular sensing and pacing mode [normal increase in heart rate (HR; DDD)], 2) HR fixed at the resting value (DOO-Rest; 73 ± 3 beats/min), and 3) HR fixed at peak exercise rate (DOO-Ex; 107 ± 4 beats/min). During control exercise (DDD mode), mean arterial pressure (MAP) increased by 25 mmHg with no change in stroke volume (SV) or systemic vascular resistance. During DOO- Rest and DOO-Ex, MAP increased (+25 and +29 mmHg, respectively) because of a SV-dependent increase in cardiac output (+1.3 and +1.8 l/min, respectively). The increase in SV during DOO-Rest utilized a combination of increased contractility and the Frank-Starling mechanism (end-diastolic volume 118-136 ml). However, during DOOEx, a greater left ventricular contractility (end- systolic volume 55-38 ml) mediated the increase in SV.
KW - Echocardiography
KW - Frank-Starling mechanism
KW - Left ventricular volume
KW - Myocardial contractility
KW - Pacemaker
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U2 - 10.1152/jappl.1997.83.3.712
DO - 10.1152/jappl.1997.83.3.712
M3 - Article
C2 - 9292454
AN - SCOPUS:0030769889
SN - 8750-7587
VL - 83
SP - 712
EP - 717
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 3
ER -