TY - JOUR
T1 - Redistribution of cardiac output during exercise by functional mitral regurgitation in heart failure
T2 - compensatory O2 peripheral uptake to delivery failure
AU - Guazzi, Marco
AU - Generati, Greta
AU - Borlaug, Barry
AU - Alfonzetti, Eleonora
AU - Sugimoto, Tadafumi
AU - Castelvecchio, Serenella
AU - Menicanti, Lorenzo
AU - Bandera, Francesco
PY - 2020/7/1
Y1 - 2020/7/1
N2 - Functional mitral regurgitation (MR) is prognostic in heart failure (HF). MR favors an nonphysiological exercise central cardiac output (CO) redistribution which adds to oxygen (O2) delivery failure. The consequences of this redistribution in O2 supply have not been explored previously. We aimed at evaluating the putative role of cardiac output (CO) and O2 arteriovenous [C(a-v)O2] difference in the attained peak V̇o2 in advanced HF with reduced ejection fraction (HFrEF) and MR. 134 HFrEF patients and 80 controls with no HF underwent exercise gas exchange combined with CO and C(a-v)O2 estimated by echo-Doppler technique. The HF population was divided into two groups: HF with severe rest MR (MR+ group; n = 36) and no to mild MR (MR- group; n = 98). HF groups did not differ in rest CO (MR+ vs. MR- 3.4 ± 1.8 vs. 3.8 ± 1.0 L/min; P = 0.32) and showed a trend for a higher C(a-v)O2 at rest (9.0 ± 4.0 vs. 8.0 ± 2.0 mL O2/100 mL; P = 0.14). In HF, CO and C(a-v)O2 at rest were significantly lower and higher compared with controls. At peak exercise, MR+ compared with MR- exhibited a significant reduction in peak V̇o2 11.6 ± 3.0 vs. 13.7 ± 3.6 ml O2·kg-1·min-1; P < 0.01) with a lower O2 delivery (CO: 5.2 ± 3.3 vs. 7.0 ± 2.0 L/min; P < 0.01), which was partially compensated by a significantly greater O2 extraction [C(a-v)O2, 18 ± 5 vs. 15 ± 4 mL O2/100 mL; P < 0.01]. In HFrEF, severe MR is associated with impaired O2 delivery due to CO redistribution to the pulmonary circulation. C(a-v)O2 is maximalized to compensate for the reduced O2 delivery. This novel information is relevant to phenotyping and targeting mediators of functional response in HF. Specifically, findings provide directions in the understanding at which extent mitral valve repair would restore an efficient cardiac reserve by enhancing O2 delivery during exercise, likely contributing to symptom relief and hopefully impacting the clinical trajectory of HF syndrome with secondary MR.NEW & NOTEWORTHY This is an analysis involving 134 heart failure patients with reduced ejection fraction versus 80 controls investigated during functional evaluation with gas exchange and hemodynamic, addressing the severe MR phenotype and testing the hypothesis that the backward cardiac output redistribution to the lung during exercise impairs delivery and overexpresses peripheral extraction. This information is new and has important implications in the management of heart failure.
AB - Functional mitral regurgitation (MR) is prognostic in heart failure (HF). MR favors an nonphysiological exercise central cardiac output (CO) redistribution which adds to oxygen (O2) delivery failure. The consequences of this redistribution in O2 supply have not been explored previously. We aimed at evaluating the putative role of cardiac output (CO) and O2 arteriovenous [C(a-v)O2] difference in the attained peak V̇o2 in advanced HF with reduced ejection fraction (HFrEF) and MR. 134 HFrEF patients and 80 controls with no HF underwent exercise gas exchange combined with CO and C(a-v)O2 estimated by echo-Doppler technique. The HF population was divided into two groups: HF with severe rest MR (MR+ group; n = 36) and no to mild MR (MR- group; n = 98). HF groups did not differ in rest CO (MR+ vs. MR- 3.4 ± 1.8 vs. 3.8 ± 1.0 L/min; P = 0.32) and showed a trend for a higher C(a-v)O2 at rest (9.0 ± 4.0 vs. 8.0 ± 2.0 mL O2/100 mL; P = 0.14). In HF, CO and C(a-v)O2 at rest were significantly lower and higher compared with controls. At peak exercise, MR+ compared with MR- exhibited a significant reduction in peak V̇o2 11.6 ± 3.0 vs. 13.7 ± 3.6 ml O2·kg-1·min-1; P < 0.01) with a lower O2 delivery (CO: 5.2 ± 3.3 vs. 7.0 ± 2.0 L/min; P < 0.01), which was partially compensated by a significantly greater O2 extraction [C(a-v)O2, 18 ± 5 vs. 15 ± 4 mL O2/100 mL; P < 0.01]. In HFrEF, severe MR is associated with impaired O2 delivery due to CO redistribution to the pulmonary circulation. C(a-v)O2 is maximalized to compensate for the reduced O2 delivery. This novel information is relevant to phenotyping and targeting mediators of functional response in HF. Specifically, findings provide directions in the understanding at which extent mitral valve repair would restore an efficient cardiac reserve by enhancing O2 delivery during exercise, likely contributing to symptom relief and hopefully impacting the clinical trajectory of HF syndrome with secondary MR.NEW & NOTEWORTHY This is an analysis involving 134 heart failure patients with reduced ejection fraction versus 80 controls investigated during functional evaluation with gas exchange and hemodynamic, addressing the severe MR phenotype and testing the hypothesis that the backward cardiac output redistribution to the lung during exercise impairs delivery and overexpresses peripheral extraction. This information is new and has important implications in the management of heart failure.
KW - Adaptation, Physiological
KW - Aged
KW - Cardiac Output
KW - Exercise
KW - Female
KW - Heart Failure/physiopathology
KW - Humans
KW - Male
KW - Middle Aged
KW - Mitral Valve Insufficiency/physiopathology
KW - Oxygen Consumption
KW - Pulmonary Circulation
KW - Pulmonary Gas Exchange
U2 - 10.1152/ajpheart.00125.2020
DO - 10.1152/ajpheart.00125.2020
M3 - Article
C2 - 32442022
VL - 319
SP - H100-H108
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
SN - 0363-6135
IS - 1
ER -