CT scans cannot detect some of CVDs since it mainly cover the vascular vessels part of the CVD not the function of the cardio engine (heart). The test procedure is only recommended if someone has CVD symptoms but not for screening. In most of the countries it will take months to perform the procedures and get the results due the scarcity of the facilities and the severe shortage of the cardiologist to perform the diagnostic with ratio to population of around 1:100,000.

ECG is the only one technique that cover comprehensive CVDs screening and it's purely non-invasive (no injection necessary). If someone has blocked arteries or even genetically malform heart like Hypertrophic Cardiomyopathy (HCM) it will show in the ECG traces, that can be cross checked with other relevant CVD diagnostic techniques. The main problem is that the screening GP and even the cardiologist has trouble performing the correct interpretation. This is where advanced signal processing and analytics, ML, AI, etc can really help, but somehow the heart fraternity like AHA is very much still in denial on this matter.

Please check the short overview article from Prof. Friedman on ECG based CVD detection in my other comment, ironically commemorating on the 100 years of AHA.