Yes indeed, CT coronary angiogram (CTCA) and cardiac MRI are non-invasive but are not as accurate as a “normal” angiogram though the sensitivity can be as high as 96%.
Current guidelines generally recommend using a CTCA when there are:
- Symptoms (chest pain, palpitations, discomfort or breathlessness on exertion)
- Inconclusive or normal stress tests with ongoing symptoms and a
- Low to intermediate probability of coronary disease (ie narrowing or blockages).
CTCA is very useful to rule out coronary blockages (ie high negative predictive value or NPV) but there is a small risk of false positive test as well.
There is also a small risk of radiation, but the benefit outweighs the risk in appropriate patients and modern CT equipment has very low radiation indeed.
Cardiac MRI on the other hand, does not involve radiation but is still not accurate as CT coronary angiogram in diagnosing coronary blockages and is used more often to diagnose cardiac structural issues such as abnormal thickening of heart muscle, thickened covering of the heart or abnormality in the valves of the heart.
I tend to perform an invasive coronary angiogram or a “normal” angiogram through the wrist (radial approach) as there is a lower rate of complications (the traditional route called femoral route through the groin is seldom used nowadays) and is more comfortable for the patients.
Coronary angiogram is the current “gold standard” and the preferred investigation in high risk individuals (ie severe or ongoing chest pain or other cardiac symptoms, on exertion or even at rest in someone with multiple heart risk factors or in someone with known heart blockages) and especially in an emergency situation in someone suspected of having a heart attack.
However even with coronary angiograms sometimes more information is required and during the procedure I tend to do additional imaging inside the artery as required. This is essentially of two kinds namely, using ultrasound called Intravascular ultrasound or IVUS and the second technique uses light called Optical Coherence Tomography or OCT. This helps to see the artery walls, the fatty plaque, composition of the plaque, and if the plaque is about to rupture and plan stent treatment accordingly. After stent has peen placed these techniques also help to ensure that the stent has been placed correctly and there are no complications as well.
Sometimes I also measure pressure across the narrowing to assess the need for treatment such as angioplasty (heart stents) and this is called FFR (Fractional Flow Reserve).This is especially required if the narrowing is of borderline severity.
We also are able to decide if the narrowing does not need any stents based on the above tests as well and whether medical therapy alone will suffice.