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The symptoms you are describing may be related to vertigo
such as positional vertigo. Given his cardiac history and medical comorbidities, other causes such as a cardiac arrhythmia
or neurologic event would need to be considered.
I would recommend seeking medication attention from his primary care
doctor or local emergency room to delineate the cause more precisely. In the interim, prior to a physician seeing him, you can try using over meclizine
for symptomatic relief of vertigo. In the United States this medication is available over the counter. The use of meclizine should not be a substitute for formal medical evaluation and he would still need to see a physician
Take care and be well