Hello! I understand your concern and would explain that fluttering and heart palpitations could be related to potential arrhythmia episodes, which may be very infrequent and impossible to detect in routine ECG monitoring. In such case, a more prolonged heart rhythm monitoring ( a week Holter) or a loop recorder could be beneficial results in this regard by detecting rate arrhythmic episodes. Another alternative of chest fluttering not related to a cardiac arrhythmia may be diaphragm fluttering or intercostal muscles myoclonia. In case no cardiac arrhythmia is concluded, then you should discuss with your attending doctor on the above mentioned alternatives. Hope to have been helpful to you! Kind regards, Dr. Iliri