Hello and thank you for using HCM.I carefully read your question and I understand your concern. I will try to explain you and give my opinion. You should know that this skipped beat has to do with a rhythm issue. There are some electrical impulses that generates from parts of the heart different from normal sinus rhythm.They cause premature heart contaction that its not a normal one followed by a pause and you might experience a skipped beat, palpitations, difficulty in breathing deeply, anxiety. There are different causes of this rhythm issue like simple stress, coffee or energy drink consumption, patologyes like anemia, hyperthyroidism,electrolyte imbalances, ischemic heart disease ect. You mention that you have already done a holter rhythm monitoring and it doesn t reveal anything abnormal. This is a very good news. But you should know that this palpitation are sporadic episodes and it is difficult to catch them. If I was your treating doctor I would insist to find the cause and I would recommend a cardiac echo to evaluate heart function and valves, a full blood analyze to exclude anemia , hyperthyroidism and a strees test as you say you are suspected for atherosclerosis. It is essential to exclude ischemic heart disease. After all this we can better judge what we are dealling whith and if we should treat medicaly. Hope I was helpfull. Best regards, Dr.Ervina.