Hello and thank you for using HCM.I carefully read your question and I understand your concern.You shoud not worry. I ll try to explain you something and give you my opinion. This extra sistolic beats 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 a premature heart contaction that its not a normal one followed by a pause and than a normal heart contraction. This extrasistoles might have different causes like stress, coffee or energy drink consumption. Also pathologys like anemia, hyperthyroidism,active infections ,ischemic heart disease might be other causes. Some medication like hormone therapy might have as a side effect palpitation feeling. You might feel them in afternoon for all different causes that I mention before. So , if they happen once a wile you should not worry about. If they start to bother you, if I was your treating doctor I will recommend some examination like an electrocardiogram, a cardiac echo to evaluate heart function and valves, a full blood analyze to exclude anemia, hyperthyroidism or electrolyte imbalance and of course the most important one a holter rhythm monitoring to evaluate your rhythm tendency. Only after this we can better judge how to deal with this and if it is necessary to do anything. Hope I was helpfull. Best regards.