Management

MDCT Coronary Angiography

Unlike catheter angiography, CT coronary angiography does not require admission in the hospital

"People may be suffering without being aware of it, as many of them may not have any typical clinical symptoms like chest pain or may have atypical symptoms like chest tightness or breathlessness or gaseous discomfort" - Dr Suman Singha Senior Consultant Radiologist Mahajan Imaging Centre Fortis Hospital, New Delhi

Heart disease is the single largest cause of mortality and morbidity amongst all diseases. As India's economy is flourishing, there appears to be a rise in Coronary Artery Diseases (CAD) especially in the affluent class. In fact, India has become the heart disease capital of the world. An increasingly sedentary lifestyle, changing food habits and an ever increasing stressful and competitive work culture have just multiplied the risk factors for coronary artery disease. The need of the hour is a non-invasive, out patient investigation that accurately diagnoses coronary artery disease early. CT Coronary angiography plays this role to perfection.

Multi-Slice CT (MSCT) has gained clinical acceptance for cardiac imaging, owing to improved temporal and spatial resolution with the latest multidetector technology which allows amazingly accurate 3-D imaging from a beating heart. With this advanced machine, every routine CT scan is a 3-D image. It takes only five seconds and one breath hold for the whole heart scan.

What is CT Coronary Angiography

CT coronary angiography is a simple non-invasive method that uses X-rays to visualise blood flow in coronary arteries which supply blood to the heart. The size of the heart and the thickness of the wall of the heart chambers are evaluated and even the surrounding area of the heart, including the lungs are visualised.

The Procedure

• This is a simple, non-invasive OPD test just like a routine CT scan test. There is no need for admission.
• The person is placed on a comfortable CT scanner table.
• Deposits of calcium in the heart are first calculated.
• A CT angiogram is obtained following contrast injection in one of the peripheral veins of the hand with online ECG monitoring.
• All the images are obtained in one single breath hold of just five seconds on the fastest scanners.
• The entire procedure hardly takes 10 to 15 minutes after which the person is ready to continue his/ her routine.

Information Obtained

Firstly, detection and quantification of calcium within the coronary vessels is obtained. Calcification in the vessel wall is an indicator of degree of damage that has occurred to the vessels. A high calcium score is consistent with a moderate to high risk of CAD. A negative calcium score is predictive of a comparatively very low incidence of CAD. The coronary arteries, their lumen, wall and plaques are seen and assessment of luminal obstruction is done. The adjacent lungs are also visualised.

What Else?

The 64-slice in a single rotation, high quality imaging allows triple heart 'rule out' i.e. the three critical causes of serious heart condition namely CAD, pulmonary embolism and aortic dissection are evaluated in one scan.

Working on the Same Day?

Can the patient go back to work on the same day? Yes, since it is a non-invasive OPD procedure, the work can be resumed on the same day after the test.

Eligibility

Who should undergo CT coronary angiography?

• Asymptomatic patient with family history of coronary artery disease.
• Patient with high risk factors.
• Prior to non-coronary surgery in the adult population, e.g. pre-ASD repair, pre-valvular repair and pre-tumour surgery.
• Follow up for post CABG.
• Atypical chest pain with doubtful coronary origin.
• Evaluation of coronary anomalies.
• Assessment of cardiac neoplasm.
• Assessment of stent potency.
• Detection and characterisation of congenital heart disease.
• Diagnosis of pericardial disease.
• Non-conclusive stress tests.
• 64 Slice MDCT is an excellent, fast, non-invasive modality for pre-operative as well post-operative assessment of pulmonary arteries and its associated anomalies and complications in pediatric patients.

Who Does Not Qualify CT Coronary Angiography

Patient with hypersensitivity to iodinated contrast, renal insufficiency with serum Creatinine > 1.5 mg/dl, congestive heart failure, atrial fibrillation and inability to hold breath for five seconds should not be referred for CT coronary angiography.

Who are at Risk?

Patients with strong family history, heavy smokers, diabetics, patients with high blood pressure, obese patients, patients with high cholesterol & triglycerides, people with high stress and high tension jobs, alcoholics, etc.

What are Asymptomatic Patients?

People may be suffering from Coronary Artery Disease without being aware of it, because many of them may not have any typical clinical symptoms like chest pain or may have atypical symptoms like chest tightness or breathlessness or gaseous discomfort. These are cases which can go undetected for a long time. For many of these cases, heart attack may be first sign of Coronary Artery Disease and many of such patients never reach the hospital.

Difference with Catheter Angiography

• Unlike catheter angiography, CT coronary angiography does not require admission in the hospital. In contrast, with the conventional catheter angiogram, where a dye is injected into the lumen of the coronary artery and hence only the inner contour of the artery can be mapped, the 64 slice CT scanner is able to demonstrate not only the lumen but also the wall of the coronary artery as well as the heart itself.
• At times, though there is a large cholesterol plaque deposit on the wall of the artery, the artery remodels its lumen and becomes wider. This is called positive remodeling. These plaques may not be picked up on the catheter angiogram, as there is no reduction in the vessel caliber. However, these plaques may also be vulnerable to acute rupture resulting in heart attacks. The 64-slice CT scanner is able to demonstrate these plaques with ease.
• Abnormal courses of the coronary arteries and congenital anomalies are well demonstrated by the 3D model of the heart on the 64-slice CT. It may be tedious and difficult to demonstrate such abnormal arteries by the conventional catheter angiogram.
• CT coronary angiography is an excellent test for coronary artery bypass grafts.

How Accurate are the Results?

A growing number of studies have suggested that 64 slice coronary CT angiography is highly accurate for the exclusion of significant coronary artery stenosis with negative predictive value of 98-100 per cent. This means that when the study is reported to be normal, it will be normal. More importantly, the heart does not have to be stressed to get this information. In presence of heavy coronary calcifications sometimes the luminal assessment is not accurate due to over estimation of stenosis.

Recent individual studies of 64-slice coronary CTA by Leschka at al, the sensitivity, specificity, negative predictive accuracy, and positive predictive values are (94 per cent, 97 per cent, 87 per cent, and 99 per cent, respectively) when compared with invasive angiography.

Is the Procedure Safe?

The CT scan of the coronary arteries is considered a very safe procedure. It's called a non-invasive procedure because there is no catheter insertion as compared to a cardiac catheterisation, which is considered an invasive produce with a certain level of risk.

How much is the Radiation Dose?

The radiation dose for this scan varies from machine to machine and can be anywhere from 3 mSv till 20 mSv. On our 64 slice VCT machine at Mahajan Imaging, Fortis Flt. Lt. Rajan Dhall Hospital, Vasant Kunj, using prospective cardiac gating gives between 3-5 mSv of radiation dose. A round trip to New York by airplane gives about 2.5 to 3 mSv of radiation. So the radiation dose used is now very low even lower than that of invasive catheter cardiac angiography.

CT Coronary angiogram today is an extremely accurate, reliable, ultra fast, noninvasive, outpatient procedure which is capable of providing detailed information of the heart and coronary vessels, thereby giving the most needed breakthrough in primary evaluation of Coronary Artery Disease. The introduction of 64 slice scanners has greatly improved spatial resolution. It holds the promise of reaping the benefits of diagnosing heart disease without invasive conventional coronary angiography. This tool is likely to develop further as a complementary tool rather than a replacement to conventional angiography, especially in patients where heart disease needs to be ruled out.

drsumansinghal@rediffmail.com