PCF8574T I2C to 8bit Parallel
Unfortunately the PCF8574T does not provide a mechanism for polling the chip to see if an interrupt has been generated. You may want to consider using a chip such as the MCP23017 which does (via the INTFx registers).

Or if, as your new edit shows, you're connecting the interrupt outputs to GPIOs anyways then just use the PCINT capabilities of the MCU to detect the interrupt.