Previous studies have found a link between that type of rapid heartbeat (called non-sustained ventricular tachycardia) and sudden death in people who had prior heart attacks. But a new report suggests that people without underlying heart disease may have little to fear. Researchers examined data on 2,234 men and women ages 21 to 96 in a multiyear study called the Baltimore Longitudinal Study of Aging. All had done at least one treadmill test that measured the heart's ability to pump. Of them, 3.6 percent developed nonsustained ventricular tachycardia with exercise that lasted, on average, three to six heartbeats at about 175 beats per minute. Death rates were higher in the tachycardia group than the nontachycardia group (29 percent versus 16 percent), were higher among men and increased with age. However, after the researchers adjusted for gender, age and people who already had heart disease risk factors, there was no significant increased risk in the tachycardia group of death from any cause, death from heart disease or having a heart attack. The research was presented last week at the American Heart Association's annual scientific sessions in Orlando, Fla. 