A substitute or substitute good in economics and consumer theory is a product or service that a consumer sees as the same or similar to another product.
Postural orthostatic tachycardia syndrome (POTS) is one of a group of disorders that have orthostatic intolerance (OI) as their primary symptom.OI describes a condition in which an excessively reduced volume of blood returns to the heart after an individual stands up from a lying down position.n POTS, the lightheadedness or fainting is also accompanied by a rapid increase in heartbeat of more than 30 beats per minute, or a heart rate that exceeds 120 beats per minute, within 10 minutes of rising. The faintness or lightheadedness of POTS are relieved by lying down again.
POTS is an unusual condition in which your heart rate speeds up by 30 or more beats per minute with little or no change in blood pressure. Such an increase in heart rate may mean that your cardiovascular system is working as hard as it can to maintain blood pressure and blood flow to your brain. According to the Rare Diseases Clinical Research Network, POTS affects about 500,000 Americans, most of whom are women under age 35.