1 The heart's internal pacemaker regulates and times the beating of the heart via electrical signals.  Electrical signals start at the SA node, causing atria contraction, and then move on to AV node, delaying electrical impulses to allow blood from the atrium to fill the ventricles.
With the First Response new Early Response Twist Pregnancy Test, you can test as early as 6 days before your missed menstrual period. This is the only test that allows you to find out this early, as it is sensitive enough to capture the very scant amounts of the pregnancy hormone.
Rated 5 out of 5 by Jennay from First Response Early Result Pregnancy Test First Response pregnancy tests have been known to be the ultimate tests for pregnancy for many years. They are very accurate tests and many women will only purchase this brand of pregnancy test. The First Response Early Result Pregnancy Test is the only brand that can tell you 6 days sooner than your missed period whether you are pregnant or not with over 99% accuracy. The new design has a longer handle, a 50% wider tip, and a easy-read window. It comes with two single use tests.