When should someone see a cardiologist?

You need to see a cardiologist in two cases:

1 - Referral from your family medicine GP if you have risk factors such A

Positive family history for ischemic heart disease like many members of your family got heart attacks or angina or stenting,
Heavy smoker,
Hyperlipidemia,
Diabetes for more than 10 years,
Hypertension

Here your GP would like to be shore you don’t have a heart problem, and diagnose early any abnormality.

2 – special symptoms or complains such as:

Chest pain or discomfort which lasts few minutes, radiating to left arm or jaw which looks like angina especially when you get this pain while you doing some activity and relieved by rest.
Shortness of breath on exertion or at night when you lying on your back which point to a heart failure.
Legs swelling especially if it is pitting and associated with abdominal distension and fatigue.
Palpitation and drop beat (missing beats) you feel as your heart racing or as stop and restart again, in another words arrhythmia which is a large field in cardiology.
You got heart attack so you need cardiologist to follow up after the emergency period and recovery. For medication and advise about lifestyle modification, you need rehabilitation also.

At last if you are aware about your risk factors and heart symptoms you might see your cardiologist to protect yourself from catastrophic event, and keep your heart healthy for longtime.