Yes. Excitement can trigger heart attacks, cardiac arrest, strokes, and other potentially fatal medical emergencies. Your body reacts to excitement in much the same way it reacts to feelings of fear or stress—by releasing the hormones adrenaline and noradrenaline. These stress hormones trigger what’s known as the fight-or-flight response, which primes people (and animals) to face dangerous situations. However, too much adrenaline and noradrenaline can be dangerous to the heart, brain, and other organs. An enormous shock, whether positive or negative, can cause your heart to speed up, beat irregularly, or stop. In patients with pre-existing heart disease, the fight-or-flight response can also dislodge arterial plaques, sending blood clots to the heart, causing a heart attack, or to the brain, causing a stroke.