Medically reviewed by Prof. Dr. Aamer Nadeem Chaudhary, M.B.B.S., D.M.R.D., F.C.P.S. (Diagnostic Radiology), Consultant, Al-Nasar Lab & Diagnostic Centre. Updated September 2026.
Quick answer: CT coronary angiography images the heart arteries using a CT scanner and an injection into an arm vein. No catheter goes into your body. It is best at ruling heart artery disease out, which makes it ideal for chest pain of uncertain cause. The scan itself takes seconds, though the visit takes around an hour.
Book a CT coronary angiogram: call 0300 0341944. Performed at our main Johar Town campus.
How is this different from a conventional angiogram?
This is the distinction that matters most, and patients are often not told it clearly.
A conventional angiogram is an invasive procedure. A catheter is threaded from the wrist or groin into the heart arteries and dye is injected directly. It is the gold standard, it carries a small procedural risk, and critically, if a blockage is found the cardiologist can open it with a stent during the same procedure.
A CT coronary angiogram is a scan. A cannula goes into an arm vein, contrast is injected, and the scanner captures the heart between beats. Nothing is threaded into your heart, there is no hospital stay, and you go home shortly afterwards. But it is purely diagnostic. Nothing can be treated during it.
| CT coronary angiogram | Conventional angiogram | |
|---|---|---|
| Invasive | No, injection into an arm vein | Yes, catheter into the heart arteries |
| Best at | Ruling disease out | Confirming and treating disease |
| Can treat during it | No | Yes, stenting is possible |
| Time | About an hour in total | Half a day or longer |
| Typical use | Chest pain at low to moderate risk | High risk, known disease, or planned intervention |
What is a coronary calcium score?
The calcium score is a separate, very quick scan done without any injection. It measures calcified plaque in the walls of your heart arteries and gives a single number.
- 0: no detectable calcified plaque. A very reassuring result
- 1 to 99: mild plaque
- 100 to 399: moderate plaque, and usually a prompt to treat risk factors seriously
- 400 or above: extensive plaque, with a significantly raised risk of a cardiac event
The score is most useful for someone with no symptoms who wants to know where they genuinely stand. It turns an abstract risk estimate into a measurement, and for many patients it settles the question of whether to start preventive treatment.
One limitation to understand: calcium scoring only sees calcified plaque. Soft plaque, which is more common in younger patients, does not register. A score of zero in a 35 year old with chest pain does not exclude disease, which is why symptoms are investigated with the full CT angiogram rather than the score alone.
Who benefits most from this test?
- Chest pain where the cause is genuinely unclear, and the estimated risk is low to moderate. This is the strongest use
- An inconclusive or borderline stress test (ETT)
- Someone who cannot exercise adequately for a treadmill test
- Strong family history of early heart disease, for a calcium score
- Diabetes, high cholesterol or hypertension, where the decision to start statins is uncertain
- Assessment of coronary artery anomalies, where CT is excellent
- Checking bypass grafts after surgery
It is less suitable when disease is already known and severe, when there are many stents, or when the heart rate is very irregular. Your cardiologist decides, often after an ECG and echocardiography. Our overview of heart related tests explains how these fit together.
Why does your heart rate matter so much?
This is the part that determines whether the scan produces usable images.
The scanner has to freeze a moving heart. The slower and more regular the beat, the sharper the arteries appear. The target is usually below about 65 beats per minute.
If your heart rate is above that, you may be given a beta blocker tablet before the appointment or an injection on the day to slow it. This is routine. You may also be given a nitrate spray under the tongue to widen the arteries just before scanning, which commonly causes a brief headache and flushing. Both are expected and short lived.
Modern multislice scanners, including 640 slice CT, capture the heart in very few beats, which improves image quality and lowers the radiation dose considerably compared with older machines.
How to prepare
- Fast for 4 hours before the scan. Water is allowed
- Avoid caffeine for 12 hours, meaning tea, coffee and energy drinks, since caffeine raises the heart rate and works against the scan
- Avoid smoking on the day, for the same reason
- Take your regular heart and blood pressure medicines unless told otherwise, and bring the list with you
- Tell the team about asthma, since beta blockers may need adjusting, and about erectile dysfunction medicines, which must not be combined with nitrates
- Tell the team about kidney problems, diabetes medicines containing metformin, thyroid disease, or any previous reaction to contrast dye
- A recent kidney function test is usually required before contrast
- Allow about an hour at the centre, even though the scan itself is seconds
CT coronary angiography at Al-Nasar Lab
Al-Nasar Lab & Diagnostic Centre has served Lahore since 1996 and holds ISO 15189:2022 accreditation from the Pakistan National Accreditation Council. CT coronary angiography and calcium scoring are performed at our Johar Town campus on multislice CT, reported by consultant radiologists, with digital reports and images provided for your cardiologist.
Because the preparation affects image quality, our team will call through the instructions before your appointment rather than leaving it to chance.
See our CT coronary angiography service page, the full CT scan in Lahore range, or contact us to book.
Frequently Asked Questions
Is CT coronary angiography painful?
No. The only discomfort is the cannula in your arm. The contrast injection commonly causes a warm flushing sensation and a feeling of needing to pass urine, both of which pass within seconds.
What does a calcium score of zero mean?
No calcified plaque was detected, which is reassuring and indicates a low short term risk. It does not exclude soft plaque, so symptoms still need proper assessment.
Do I need to fast?
Yes, about 4 hours, and avoid caffeine for 12 hours beforehand because it raises your heart rate and degrades the images.
Can a CT angiogram replace a conventional angiogram?
Often it can, particularly when the goal is to rule disease out. If a significant blockage is found, a conventional angiogram is still needed because that is where treatment happens.
How much radiation is involved?
Less than it used to be. Modern multislice scanners with dose reduction protocols have cut the exposure substantially, and your doctor weighs it against the value of the answer.
This article is for general information and is not a substitute for medical advice. Please discuss your results with a qualified doctor.
