Ripples on the LCD monitor during "heavy" games

Artifacts the video card due to overheating/overclocking.

Overclocking a video card, possibly overheating.
And indeed vidyuhi not really for heavy gaming.

overheating of some part of the video card. try to reduce frequency on it

maybe you should just disassemble and clean, vacuum, lubricate the fan on the video and change the thermal paste. I think it is banal overheating from dust.

Try adjusting the monitor menu of the monitor. My monitor showed a picture so that it seemed that sometimes he squeezes, stretches and sometimes. Helped to modify the settings of Frequency/Phase.

Problems on nutrition clearly and/or interferences to the signal cable
I advise you to try to change the signal cable to a higher quality(borrow to test) if will not help — I advise you to change the PSU to a higher quality.
The power supply is advised to choose with wires "thicker", or at the price — more expensive.
Not necessarily 500vatt, and quality and slightly more expensive 300-350W will fit
Of course the problem would be solved the digital connection, but such as I understand is not on this monitor...