What are the causes of rapid chf?

Many: Not sure i understand the question, but if you mean rapid worsening of chf, there are many including: ischemia (heart attack), dietary indiscretion, viruses/infection, blood pressure problems, and arrhythmias...To name a few.

CAD/BP/arrhythmia: Sudden CHF (flash pulmonary edema) is typically caused by sudden ischemia due to coronary disease, sudden valvular dysfunction (ex sudden chordal tear in mv disease, ischemic mitral regurg, endocarditis), persistent high elevations in BP (ex-renal artery stenosis), or sudden arrhythmia (example sudden rapid afib, partic if associated w valvular disease or lv dysfunction).