You should be careful! Arrhythmia, such as tachycardia, alters the heart's output(the volume of blood pumped out of the heart to provide oxygen to tissues).
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2001-7-9{246}(#125768@0)
This can lead a wide range of comlications, such as dizziness, fainting, blood clots, cardiac arrest, some of them are fatal!
If your father has one of the complications,he should see a doctor to rule out those life-threatening complications.