Angioplasty is commonly performed to open a narrowed or blocked heart artery and restore blood flow. Before and during the procedure, doctors usually rely on coronary angiography to locate blockages. However, angiography may not always show the complete picture of what is happening inside the artery. This is where newer tests can give additional information and help doctors make more precise treatment decisions. Dr Vivudh Pratap Singh, Additional Director, Cardiology, Fortis Hospital Okhla, shares other tests that can help cardiologists.

Dr Singh explains that angiography mainly shows the silhouette of the artery, while tests such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT) allow doctors to see the artery from the inside. Other tests, including fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR), can also help determine whether a narrowing is actually reducing blood flow. Together, these tests can help doctors decide whether a stent is needed, which stent should be used and more.

Why Angiography May Not Tell The Full Story

Coronary angiography uses X-rays and contrast dye to show where an artery is narrowed. While it is an important part of angioplasty, it mainly provides a two-dimensional view of the artery's outline. "It shows us where the blockage is," says Dr Singh, "but intravascular imaging helps us understand what is happening inside the artery - and how best to treat it."

Plaque, calcium, the actual size of the blood vessel and the length of a lesion may not always be clearly visible on angiography. This can become particularly important when blockages are complex.

Doctors See The Artery From Within Using IVUS

Intravascular ultrasound, or IVUS, uses sound waves to create images from inside the artery. A small ultrasound probe is passed through the blood vessel during the procedure. IVUS can help doctors assess:

  • Vessel size: It gives a better estimate of the artery's actual diameter, helping doctors select an appropriate stent
  • Plaque burden: It can show how much plaque is present within the artery
  • Calcium: It can help identify heavily calcified areas that may make stent placement more difficult
  • Stent expansion: After a stent is placed, IVUS can check whether it has opened adequately

This information can be useful when the artery is large, the blockage is long or the anatomy is difficult to assess through angiography alone.

OCT Gives Higher-Resolution Images

Optical coherence tomography, or OCT, is another form of intravascular imaging. Instead of ultrasound, it uses light to produce very detailed images of the inside of the artery. OCT can provide high-resolution views of plaque and stent-related details. It can help doctors identify problems such as tissue protruding through the stent, a small tear at the edge of the treated area or incomplete contact between the stent and artery wall.

The choice between IVUS and OCT depends on the patient's anatomy and the clinical situation. Both can provide information that angiography may not.

These Tests Can Improve Stent Selection

Choosing the correct stent is an important part of angioplasty. A stent that is too short may not cover the entire diseased segment, while an incorrectly sized stent may not adequately support the artery. Intravascular imaging can help doctors measure the vessel more accurately and determine the appropriate stent diameter and length. This can reduce the risk of "geographic miss", where part of the diseased area is left untreated.

Imaging Can Check Whether The Stent Is Properly Placed

Placing a stent is not necessarily the final step. Doctors also need to make sure it has expanded properly and is sitting closely against the artery wall. Imaging can detect under-expansion, where the stent has not opened fully, and malapposition, where parts of the stent do not properly touch the artery wall. It can also identify edge problems, tissue prolapse and thrombus that may be difficult to spot on angiography.

When Is Intravascular Imaging Especially Useful?

According to Dr Singh, IVUS and OCT can be beneficial during complex angioplasty, including procedures involving:

  • Left-main coronary artery disease
  • Bifurcation lesions, where one artery divides into two
  • Long lesions
  • Heavily calcified blockages
  • Complex or difficult-to-assess coronary anatomy

International guidelines support the use of intravascular imaging in such cases. The 2024 ESC Guidelines give IVUS/OCT a Class I, Level A recommendation for PCI in anatomically complex lesions, particularly left-main disease, true bifurcations and long lesions. The 2025 ACC/AHA/SCAI guideline also gives a Class I, Level A recommendation for IVUS/OCT-guided PCI in patients with acute coronary syndrome undergoing left-main or complex-lesion stenting.

FFR Checks If A Blockage Is Actually Affecting Blood Flow

Not every narrowing seen on an angiogram necessarily needs a stent. This is where fractional flow reserve, or FFR, can provide important information.

FFR measures how much a narrowing affects blood flow to the heart muscle. In simple terms, angiography shows the narrowing, while FFR helps determine whether that narrowing is actually causing reduced blood flow, or ischaemia. This can help doctors decide whether a blockage needs treatment or whether it can be safely managed without placing a stent.

iFR And RFR Can Assess Blood Flow Without Adenosine

Instantaneous wave-free ratio (iFR) and resting full-cycle ratio (RFR) are other physiological tests used to assess coronary blockages. Unlike traditional FFR, these methods do not require adenosine to measure the pressure difference across a narrowing. This can make physiological assessment quicker and more comfortable for patients. These tests can be particularly useful when several arteries have blockages. International guidelines support FFR or iFR to guide treatment decisions for intermediate coronary lesions when there is no clear evidence of ischaemia.

Angiography remains a crucial tool during angioplasty, but IVUS and OCT can reveal the structure of the artery in much greater detail, while FFR and iFR can show whether a narrowing is actually affecting blood flow.

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