回归分析求助

The relation of Cum%VP to first HFH and first incidence of AF

was assessed by means of Cox proportional hazards models, with

time to event as the dependent variable and Cum%VP as a time

dependent covariate。谁能帮我解释下后面一句话什么意思。这似乎是first HFH和Cum%VP的回归或相关分析，时间怎么安排？