Dear User, 
Thanks for Asking , I understand how horrible head aches can be some times.
Glad to know that your 
CT scan was normal , After Reading what you have written, I assume the following are your problems 
1) Headache 
2) High BP
3) Palpitations ( Hearing your own heart beat )
3) Slight Irregularity in ECG 
Before I answer you , I need some more information from your end 
1) How long are you having High BP ? and how high is your BP now ( Latest Reading ) 
2) What is the dose of 
Lisinopril you are taking 
3) You said you hear your heart beat ? How long has it been ?
4) since How many days (Duration ) you are having this head ache ?
5) Did the doctor in the ER mention what irregularity you are having in ECG 6)Please mention your age and gender 
- You are Right lisinopril can increase your headache !But that said even High BP can cause head ache. 
- Palpitations can be even due to 
anxiety but also there is a chance of abnormal heart Rythm which can manifest as palpitations...
Please Provide information for the Questions i have asked , I will be happy to help you and guide you.
Regards 
Dr.Samuel