A new technique to study chemical changes in beating hearts has documented for the first time how calcium buildup leads to 200,000 sudden deaths a year in the United States, a researcher said in a study released Friday.

Dr. William T. Clusin, a Stanford University associate professor of medicine, said the findings appeared to validate the common use of calcium blockers for people suffering from a prevalent heart condition called ischemia.Even more importantly, Clusin said, the techniques used in the study have important implications for future treatments. An innovative fiberoptic device and a unique dye used in the experiments proved themselves to be potentially valuable tools for developing more effective cardiac medications, he said.