It all depends on purpose of angiography, If a patient who already has heart problems or have risk factors for heart disease like
Diabetes, hypertension, Smoking should undergo conventional angiography. Person who do not have any risk factor, relatively young, Echo normal, but had some atypical symptoms may advised CT angio. CT angio is correct in ruling out blockages but if some blockages are there, then treatment decisions can not be decided by CT Angio alone. CT Angio is not a good test to do in asymptomatic person (A person who never had symptoms or any abnormal test). It carries lots of radiation almost double contrast dose than conventional Angiography.
Next Steps
Just determine why you want to do it and decide
Health Tips
If Heart problem is there then conventional, If no symptoms then other noninvasive tests, CT Angio only in symptomatic low probability of heart disease persons.