How bad is mild concentric left ventricular hypertrophy on a heart scan?

This used to be. Called "idiopathic hypertrophic subaortic stenosis" ihss which was a mouthful reduced to ash, assymetric septl hypertrophy.These may be the cause of sudden death in young athletes, perhaps from arrhthmias, but rescussitation may be difficult. If you know you have this. You warrant a cardiologist to advise management, and it may be minor to nothing, but trust an expert not a website for this.
Not bad. Usually the result of untreated high blood pressure. Just make sure your blood pressure is normal and you maintain a reasonable weight.