Evidence for a negative inotropic effect of obesity in human myocardium?
OBJECTIVE
The present study was performed as an attempt to analyze the relationship between body weight and human myocardial performance. As overweight is frequently associated with hypertension, stenosis of epimyocardial coronary arteries and other factors that influence myocardial performance, the experimental model of isolated human atrial myocardium was selected. Atrial contractile performance does neither depend on the extent of stenosis of epicardial coronary arteries nor on the degree of hypertension and its secondary pathology.


METHODS
Right atrial muscle preparations (0.5 x 6 mm) of 183 patients undergoing coronary artery bypass surgery were electrically stimulated at optimal length. Active tension (stimulation) and passive resting tension (relaxation) were measured (measurement conditions: 37 degrees C, Krebs-Henseleit solution, optimal length and supramaximal electrical stimulation). The relationship of body weight with the measured parameters was analyzed statistically by using linear regression model and Student's t-test.


RESULTS
Active tension (mN/mm2) and passive resting tension (mN/mm(2)) declined significantly with increasing body weight (p < 0.0001). The ratio passive resting tension/active tension correlated significantly with body weight (p < 0.0001). The negative association between body weight and active tension amplitude was more pronounced in women (p < 0.05). The following linear regression was calculated: for men: force = -0.04 x body weight + 8.74 (R = 0.505, p < 0.0001, n = 106); for women: force = -0.08 x body weight + 12.03 (R = 0.717, p < 0.0001, n = 77).


CONCLUSIONS
The experimental data are in accordance with the hypothesis, that obese tissue may exert a direct cardio-depressant effect on electromechanical coupling.
Denk
Katja
K
Department of Cardiothoracic and Vascular Surgery, University of Mainz, Mainz, Germany. katja.denk@gmx.net
Albers
Jörg
J
Kayhan
Nalan
N
Ister
Dilek
D
Bonz
Andreas
A
Werner
Christian
C
Münzel
Thomas
T
Vahl
Christian-Friedrich
CF