What does a cardiologists mean when they say" you just have a irritable heart". and what causes developing this and what consequences are there withit?

Implies extra beats: Extra beats come from many sources. Increased adrenalin (hyper-anxiety), abn electrolytes (K+, Mg++). I do not know if you are taking meds that can affect these things. Mg++ and K+ can be supplemented. Anxiety may require medication. If echo is normal, treatment should be easily achieved. Sometimes a low dose long acting Beta Blocker will help.