Would you re-challenge a patient with refractory multiple myeloma with carfilzomib who responded well but developed grade 3 heart failure and subsequently recovered the EF upon holding carfilzomib?  

I avoid rechallenging and try to find a different regimen if applicable. If Carfilzomib was the only option left for RRMM, then you might consider a dose reduction with close follow up with cardio-oncology to optimize HF medications.