Hi and welcome to the forum! I am glad that I can help you.
You want to know whether it is safe to stop the treatment for a heart condition.
Heart conditions such as palpitations, aortic stenosis and other types of stenosis (of the heart valves) may be accompanied with increased blood pressure in one of the chambers of the heart. In case of aortic stenosis the blood pressure is in the normal range, but the left ventricle experiences a lot of effort because the heart muscle keeps trying to pass the blood through the stenosis. This may lead to palpitations, hypertrophy and later dilatation of the left ventricle. To ease the function of the left ventricle and to prevent it from any type of arrhythmia or infarction, cardiologists prescribe medications such as beta blockers and calcium channel blockers.
Given the data that you described, you would like to lose weight. You may want to consider continuing with the medical treatment for your heart condition with regular control visits to your cardiologist. You may try another way of reducing weight except walking, such as a diet rich in vegetables and fruits. Avoid food rich in fats such as pork meat, animal fat, nuts, sweets, etc.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please contact your doctor for further advice and information about your current condition and weight loss.