In some cultures in the Northern Hemisphere, the astronomical March equinox (varying between 19 and 21 March) is taken to mark the first day of spring, and the Northern solstice (around 21 June) is taken as the first day of summer. In other traditions, the equinox is taken as mid-spring.
Circulation problems that cause dizziness. You may feel dizzy, faint or off balance if your heart isn't pumping enough blood to your brain. Causes include: 1  Drop in blood pressure.
Heart attacks increase the risk for sudden cardiac arrest. Most heart attacks do not lead to sudden cardiac arrest. But when sudden cardiac arrest occurs, heart attack is a common cause. Other heart conditions may also disrupt the heartâs rhythm and lead to sudden cardiac arrest. These include a thickened heart muscle (cardiomyopathy), heart failure, arrhythmias, particularly ventricular fibrillation, and long Q-T syndrome.