Effects of gender, ejection fraction and weight on cardiac force development in patients undergoing cardiac surgery--an experimental examination.
BACKGROUND
It has long been recognized that differences exist between men and women in the impact of risc factors, symptoms, development and outcome of special diseases like the cardiovascular disease. Gender determines the cardiac baseline parameters like the number of cardiac myocyte, size and demand and may suggest differences in myofilament function among genders, which might be pronounced under pathological conditions. Does gender impact and maybe impair the contractile apparatus? Are the differences more prominent when other factors like weight, age, ejection fraction are added?Therefore we performed a study on 36 patients (21 male, 15 female) undergoing aortic valve replacement (AVR) or aortocoronary bypass operation (CABG) to examine the influence of gender, ejection fraction, surgical procedure and body mass index (BMI) on cardiac force development.


METHODS
Tissue was obtained from the right auricle and was stored in a special solution to prevent any stretching of the fibers. We used the skinned muscle fiber model and single muscle stripes, which were mounted on the "muscle machine" and exposed to a gradual increase of calcium concentration calculated by an attached computer program.


RESULTS
1.) In general female fibers show more force than male fibers: 3.9 mN vs. 2.0 mN (p = 0.03) 2.) Female fibers undergoing AVR achieved more force than those undergoing CABG operation: 5.7 mN vs. 2.8 mN (p = 0.02) as well as male fibers with AVR showed more force values compared to those undergoing CABG: 2.0 mN vs. 0.5 mN (p = 0.01). 3.) Male and female fibers of patients with EF > 55% developed significantly more force than from those with less ejection fraction than 30%: p = 0.002 for the male fibers (1.6 vs. 2.8 mN) and p = 0.04 for the female fibers (5.7 vs. 2.8 mN). 4.) Patients with a BMI between 18 till 25 develop significant more force than those with a BMI > 30: Females 5.1 vs. 2.6 mN; p 0.03, Males 3.8 vs. 0.8 mN; p 0.04).


CONCLUSIONS
Our data suggest that female patients undergoing AVR or CABG develop significantly more force than male fibers. Additionally we could image the clinical impression of negative impact of overweight and obesity as well as low ejection fraction on cardiac function on level of the myofilaments and observed a reduced force capacity, which is more prominent in male fibers.
Department of Cardiothoracic and Vascular Surgery, Medical Centre of the Johannes-Gutenberg-University Mainz, Langenbeckstr,1, 55131 Mainz, Germany. constanze.bening@googlemail.com.
Constanze
C
Bening
Helge
H
Weiler
Christian-Friedrich
CF
Vahl
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000601:surgery*; D001835:Body Weight / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D001026:Coronary Artery Bypass; D005260:Female; D006321:Heart / Q000502:physiology*; D006334:Heart Function Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D012737:Sex Factors; D013318:Stroke Volume / Q000502:physiology*
D002118:Calcium