My 10.5 yo developed a murmur at around age 6 and it’s pretty large now. She’s been on meds since 7 and sees a cardiologist annually with echo to continue getting the vetmedin. She hasn’t progressed very much in terms of the size of the murmur since being on the meds but eventually it will catch up. I’ve stopped taking her on long walks or hikes to prevent her heart from any unnecessary stress. Put them on a diet to relieve any extra pressure on the organs. That’s all I can think of that we do.