<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by progressive familial heart block ? [/INST] The prevalence of progressive familial heart block is unknown. In the United States, about 1 in 5,000 individuals have complete heart block from any cause; worldwide, about 1 in 2,500 individuals have complete heart block. </s>