Invasive Cardiac Diagnostics

While non-invasive tests such as echocardiography and CT scanning provide valuable information, some cardiac conditions require direct assessment using catheter-based techniques. Invasive cardiac diagnostics allow us to obtain precise measurements of blood flow, pressures, and anatomy that guide treatment decisions.

These procedures are performed in the cardiac catheterisation laboratory, typically under local anaesthesia with sedation. Most patients can go home the same day.

Diagnostic Coronary Angiography

Coronary angiography remains the gold standard for visualising the coronary arteries – the blood vessels that supply the heart muscle. A thin catheter is inserted through an artery in your wrist (or sometimes the groin) and guided to the heart. Contrast dye is injected, and X-ray images reveal the location and severity of any narrowings or blockages.

The results of coronary angiography help determine whether treatment is needed and, if so, which approach is most appropriate – medical therapy, percutaneous coronary intervention (angioplasty/stenting), or coronary artery bypass surgery.

Coronary Physiology Assessment (FFR/iFR)

Not all coronary narrowings seen on angiography require treatment. Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are techniques that measure whether a narrowing is actually restricting blood flow to the heart muscle.

A pressure-sensing guidewire is passed across the narrowing to measure the pressure difference. This provides objective evidence of whether the blockage is physiologically significant – information that helps us avoid unnecessary stenting while ensuring that important blockages are treated. Multiple clinical trials have shown that physiology-guided decision-making leads to better patient outcomes.

Intravascular Imaging (IVUS)

Intravascular ultrasound (IVUS) uses a miniature ultrasound probe on the tip of a catheter to create detailed cross-sectional images of the coronary artery from the inside. While angiography shows the silhouette of the vessel lumen, IVUS reveals the vessel wall itself – including the extent and composition of plaque.

IVUS is particularly valuable for assessing ambiguous lesions, guiding complex interventions, and ensuring optimal stent deployment. Studies have demonstrated that IVUS-guided stenting is associated with improved outcomes compared to angiography guidance alone.

Coronary Vasospasm Testing

Some patients experience chest pain caused by coronary artery spasm rather than fixed blockages. In vasospastic angina, the coronary arteries temporarily constrict, reducing blood flow. This can be difficult to diagnose because the arteries may appear normal on standard angiography.

Provocative testing using acetylcholine can be performed during angiography to unmask coronary spasm. Identifying vasospastic angina is important because it requires different treatment (calcium channel blockers and nitrates) compared to atherosclerotic coronary disease.

Right Heart Catheterisation

Right heart catheterisation measures pressures in the right side of the heart and pulmonary arteries, as well as cardiac output. A catheter is passed through a vein, usually in the neck or groin, and advanced through the right heart chambers into the pulmonary artery.

This procedure is essential for diagnosing and classifying pulmonary hypertension, assessing the severity of heart failure, and evaluating patients before heart transplantation or mechanical circulatory support.

The Growing Role in HFpEF

Heart failure with preserved ejection fraction (HFpEF) is an increasingly common condition that can be challenging to diagnose. In many patients, resting measurements are normal, but the heart’s filling pressures rise abnormally during exertion. Exercise right heart catheterisation – measuring pressures while the patient pedals a supine bicycle – can unmask this abnormality and confirm the diagnosis when non-invasive testing is inconclusive.

Haemodynamic Assessment

Valvular Heart Disease

While echocardiography is the primary tool for assessing heart valve disease, invasive haemodynamic assessment is sometimes needed when non-invasive findings are discordant or inconclusive. Direct measurement of pressures across heart valves provides definitive assessment of stenosis severity and helps guide decisions about intervention.

Constrictive vs Restrictive Physiology

Constrictive pericarditis and restrictive cardiomyopathy can present with similar symptoms and imaging findings, yet they require very different treatments. Invasive haemodynamic assessment with simultaneous right and left heart catheterisation can distinguish between these conditions by analysing the characteristic pressure patterns – information that is critical for guiding management.

Endomyocardial Biopsy

Endomyocardial biopsy involves obtaining small samples of heart muscle tissue for microscopic examination. A specialised catheter with a small grasping device (bioptome) is passed through a vein in the neck or groin and guided to the right ventricle, where tiny tissue samples are taken from the inner surface of the heart.