If you experience palpitations frequently,you need to be examined clinically by an cardiologist.There are many reasons for the palpitations heart related and others like anemia ,
thyroid disorders , anxiety related.A baseline ECG would show a type of increase in heart rate.A 24 hours holter monitoring may be requested by your cardiologist.A small amount of pericardial effusion may not cause any symptoms.However it may cause breathless , palpitations and fainting, chest pain if effusion amount is significant.