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The effects of exercise induced tachycardia on the maternal electrocardiogram
U A Asher1, I Ben-Shlomo, M Said
1Department of Obstetrics and Gynaecology, Rebecca Sieff Hospital, Safed, Israel.
Objective:
To determine whether pregnancy has an effect on the maternal electrocardiographic response to stress.
Design:
Eight maternal ECG parameters were screened before, during and after exercise induced tachycardia at 29 and 37 weeks gestation and at 6 weeks post partum for each participant.
Setting:
General Hospital in Safed, Israel.
Subjects:
Fifteen healthy, pregnant women aged 22 to 34 years with singleton pregnancies volunteered from the peripheral antenatal clinics.
Intervention:
Exercise stress tests were performed on a Quinton 3000 treadmill stress test system according to a Modified Bruce Protocol, producing a heart rate of 85% of age predicted maximum.
Main Outcome Measures:
The ST-segment, T-wave, QRS complex, axis, rhythm, disorders of impulse conduction, the P-Q and Q-T intervals were screened before, during and after the exercise test.
Results:
The study results suggest an increase in the ST-segment changes induced by stress at 37 weeks of pregnancy compared to 29 weeks (ST-depression in 6 women out of 15 versus 2, P = 0.125, McNemar's Test for Correlated Proportions-Exact Test, two tailed; 95% CI, 0.042-0.492, 0.01 < P < 0.05) and to the post partum test (ST-depression in 6 women out of 15 versus 1, P = 0.125; 0.029-0.637, 0.01 < P < 0.05). No significant alteration of the other ECG parameters. No significant correlation between blood haemoglobin level, serum levels of sodium, potassium, calcium, glucose and 17 beta-oestradiol with the appearance of the ECG change.
Conclusions:
The increase in the exercise induced ST-segment abnormalities at 37 weeks of pregnancy may be another physiological effect of late pregnancy which has not been demonstrated previously.