Hi.. If you speak of being safe, then you may consider checking with the cardiologist first... And if the cardiologist still feel that the echocardiogram (ultrasound) is needed then you may get it.. I feel it could just be due to the stress, anxiety that you have been through due to your dad's condition and added with the caffeine consumption.. Alternatively you can consider taking an opinion from one of the cardiologist available on the specialist opinion list of doctors in this website..
The link would be http://www.healthcaremagic.com/specialists/Cardiologist/Dr-Gopi-A/2