How does cooling therapy work?

Coronary angioplasty is a common procedure Coronary angioplasty is a common procedure to open however clogged blood vessels in the heart. The doctor guides a long, thin plastic tube (a catheter) to the heart via an artery, then inflates a balloon at the end of the tube to break up the buildup of cholesterol plaques. A fine wire-mesh tube called a stent is left in the coronary artery to keep it open.

Pacemakers can be placed in the chest to help control heart-rhythm disturbances such as tachycardia, which causes fatigue and other problems. They send small electric pulses to the heart, and newer models can also monitor blood pressure and other vital signs. Implantable cardioverter-defibrillators (ICDs) are similar to pacemakers, but can also shock the heart back to normal in case of cardiac arrest.

How many people can be saved by cooling?

Studies examining two types of cardiac arrest (ventricular fibrillation and tachycardia) show that one extra patient will survive without brain damage for every four to six people cooled. If all suitable patients were cooled, that means an additional 2,300 Americans would be able to leave the hospital with little or no brain damage every year, according to a government-funded study from 2008 -- the only published estimate. But some experts say the number could be much higher. Dr. Graham Nichol of the University of Washington puts it at 6,600, while Columbia's Dr. Stephan Mayer's calculations show it could be as many as 20,000.