Hi Thank you for your query with HCM, it would have better if you had mentioned when did you fell dizziness after the surgery or one day after surgery coz if it is after surgery, then it could be of less bloc supply to brain due to chair position for a long time which called as syncope which will come back within mins nothing to worry about it. if it is after one day of surgery, you are on drug called codeine which has mild to moderate sedative effect which could be the reason for your dizziness whatsoever be cautious when you are on these drugs while driving and doing your regular work. These drugs are no way harmful to anyone if used under medical supervision.if problems persists then visit your doctor. Hope my answer would be helpful to your query.