What Causes Severe Headaches While On Blood Pressure Medications?

My wife had a couple ekg s done recently and both came back with negative results. Her Cardiologist gave her meds. to lower her BP, which worked, but yesterday she started having occasional sharp pains in the right upper front portion of her head and had a bad headache all night & all day today. She s scheduled for an angiogram next Thursday, but is concerned the headache might be a sign that something is getting worse. She has taken Tylenol for the headache, but got very little relief.