In February 2013, a study by the University of California revealed that the hearts of two people in love can beat in unison, "one of the partners, usually women, adapts his heartbeat to that of the other", said Emilio Ferrer, one of the research leaders. This result followed in a few years the one from the University of Aarhus, in Denmark, which had instead established that watching a friend subjected to stressful situations leads to the modulation of our heartbeat in the same pace of his own. It is peculiar that love, or affection in general, causes the heart function contrary to the medical standards of good health. Our heartbeats should always be regular, restrained, yet when falling in love, when we lay eyes on that wonder, the brain sends a message to the adrenal gland that secretes hormones like adrenaline, epinephrine and norepinephrine which increase the beats of your heart.
It doesn't sound very romantic, but it is indeed the prerequisite for romanticism.