Although it seems like a sarcastic answer, being blind would be difficult, if not impossible for the job. Being a cardiologist means being able to read and interpret graphs, perform minor surgeries (e.g. inserting a stent), and so on. Otherwise, there are no limiting factors for cardiologists. Even being mute is possible to have a cardiology job, because now, hospitals are required to have translators by law (such as sign and foreign languages)