with an EF of 20-30, is it safe to take a pharmacological stress test or heart catherization or neit

In 2002 I had a heart bypass and mytral valve repair. At the time I had an Ejection Fraction [EF]of 29. The surgeries were successful. My EF jumped to 55. Recently after an Echocardiogram I was told my EF was 20-30%. I was scheduled for a pharmacological stress test but have felt very uneasy about it. Now they want me to have a heart catherization, but I AM VERY, VERY APPREHENSIVE ABOUT THAT ALSO. [I've had 3 caths before but my EF was much higher than now]. Should I be this apprehensive and frankly "scared" to have these procedures done with such a low EF? With my last catherization I went into heart failure just before they began the procedure. That was because they failed to give me my Lasix that morning. I had it done the next day and it turned out fine.