Gender differences in QTc interval in young, trained individuals with lower spinal cord injury

STUDY DESIGN

Cross-sectional comparison.

OBJECTIVE

To examine gender differences in rate-corrected QT interval (QTc), an index of ventricular depolarization/repolarization, in young, trained men and women with lower spinal cord injury (SCI) and able-bodied (AB) controls.

SETTING

University of Illinois at Urbana-Champaign, Exercise and Cardiovascular Research Lab, USA.

METHODS

Subjects consisted of 16 athletes with SCI (eight men and eight women) and 16 age-matched AB active controls (eight men and eight women). QT interval dynamics was derived from ECG recordings and rate corrected using the Bazett formula.

RESULTS

Men with SCI had QTc similar to that of AB men (369.3+/-7.5 versus 357.9+/-3.0 ms, P>0.05). Women with SCI had QTc similar to that of AB women (400.0+/-4.6 versus 385.2+/-6.5 ms, P>0.05). AB women had longer QTc interval than AB men, and SCI women had longer QTc than SCI men (P<0.05).

CONCLUSIONS

Gender differences in ventricular depolarization/repolarization are present in trained individuals with SCI. Thus, similar to their AB gender-matched peers, women with SCI have longer QTc intervals and may be at greater risk for the development of untoward cardiac arrhythmias than men with SCI.

Nitrogen balance of healthy Dutch women before and during pregnancy

BACKGROUND

Experimental studies including longitudinal nitrogen balance studies could provide insight into protein metabolism in pregnancy.

OBJECTIVE

Our aim was to determine the development of nitrogen balance during pregnancy compared with nitrogen balance before pregnancy in women consuming imposed constant diets. We also tracked changes in muscle mass and lean body mass by measuring urinary 3-methylhistidine (3-MeH) and urinary creatinine.

DESIGN

Nitrogen balance was determined over 8 d in 12 healthy Dutch women before pregnancy and at weeks 12, 23, and 34 of gestation. Complete daily diets were supplied during each balance period so that each subject's energy, protein, and macronutrient intakes were similar in amount and composition in all 4 balance periods.

RESULTS

Throughout pregnancy there was no significant change in loss of nitrogen in feces and therefore no change in protein digestibility. The amount of nitrogen excreted in urine in late pregnancy (11.0 +/- 1.4 g/d) was significantly (P < 0.01) less than in early pregnancy (12.6 +/- 1.3 g/d). Nitrogen retention increased toward term, even though energy balance became progressively negative. The difference between the first (-0.4 +/- 1.7 g N/d) and third (1.2 +/- 1.6 g N/d) trimester was significant (P < 0.05). No differences were found in either 3-MeH or creatinine excretion between trimesters.

CONCLUSIONS

These urinary nitrogen excretion and nitrogen retention data show that when the dietary supply remains constant, nitrogen balance increases toward the end of pregnancy, suggesting a more efficient use of dietary protein later in pregnancy. Urinary 3-MeH and creatinine excretion indicated no change in protein metabolism.