How far can an ECG test go towards diagnosing a heart condition?!

How far can an ECG test go towards diagnosing a heart condition?

what are the limitations of an ecg, can they show signs for the majority of heart conditions? I have been experiencing rapid heart rates at random times with intermittent chest pain on occasions. I have a slight tightness in my chest too. I had an episode when i was walking through town where i felt light headed and my lips went blue apparently, my heart started to race, it calmed down after 2 minutes or so. I went to the hospital where i was given an ecg and told i was ok and to go home. I have spoken to my doctor about this before but am always met with reluctance to refer me on for other tests, they just say its anxiety, but they never give me any answers. My ECG's are all fine but i am not convinced.

2 weeks ago
I have had 3 ecg's and they have all come back ok

I agree, with you that there is lot of misinterpretations on acute myocardial infarction or on ACS protocol.There are many others too. This research article will help you out:

The objective of the study was to determine the concordance of emergency physicians' and cardiologists' interpretations of emergency department (ED) electrocardiograms (ECG), to evaluate the impact of ECG misinterpretation on patient management, and to determine error rates as a function of the level of physician training and the specific ECG diagnoses. ECG interpretations were registered prospectively using a programmed-response data sheet. A second blinded interpretation by a staff cardiologist was assumed to be correct. Only ECG discrepancies with potential or probable clinical importance were considered as errors. The ED management of patients with ECG misinterpretations was reviewed by the investigators. The study was performed at an urban university hospital using 300 consecutive ED ECGs. The analysis found 154 errors of interpretation of which nine had probable clinical significance, and 56 had indeterminant significance. The concordance was weak at 0.69 (Kappa = 0.32, weighted Kappa = 0.30) with a significant discordance (McNemar Chi 2:P < 0.05). Error rates did not differ significantly between the diverse categories of physicians. In two cases, interpretation errors impacted patient management decisions but not patient outcomes. The most frequent errors involved repolarization abnormalities, ventricular hypertrophy and hemi-blocks. While discordance was significant, errors in ECG interpretation rarely impacted patient management. Prospective evaluation of ECG interpretation may be a useful means of gauging physician skills. It can also serve to focus educational activities on problem areas in electrocardiography.
In my opinion you better report to a cardiology ER. They will sort out your problem.