Very bad idea, based on two misunderstandings.
One is that the events you are detecting are "urgent", when in fact they occur thousands - or in this case, many millions - of processor clock cycles apart and accuracy in the microsecond range is neither necessary nor desirable. Depending on the pulse sensor, it may require "de-bouncing" which while it can be performed in interrupts, becomes unnecessarily complicated.
The second misunderstanding, is that interrupts are used to alter the "flow" of the main (loop) program whereas in fact, interrupts are deliberately engineered not to do so. If your main task is to time events, then you "poll" or check for those events in your main loop, alternately with checking for whether a certain time has expired and if necessary, displaying a result.
I posted some suggestions a little time back as to how best to do the pulse measurement.