The guitarist was hospitalised in Croatia in August (14) after suffering heart problems during the band's European tour, and he was subsequently flown back to Britain to undergo surgery.
Parfitt, who underwent a quadruple heart bypass in 1997, reveals he was given good news after a recent check-up.
He tells Britain's The Sun newspaper, "I went for a full check-up a few weeks ago and my heart is only five per cent damaged."
The 66-year-old star goes on to insist giving up alcohol and cigarettes has helped him bounce back to health, adding, "I've closed the door, bolted it, and welded it up when it comes to drinking, drugs and smoking. I'm clean now and I feel so much better... I chose to shut the door to it all."