🟠 Moderate Evidence
- The Anatomy Problem: Why Looks Can Deceive
- Functional Assessment: Measuring What Matters
- Guideline Evolution and Clinical Implementation
- Clinical and Public Health Implications
- Frequently asked questions
- What is fractional flow reserve (FFR), and how is it different from angiography?
- Is FFR testing safe, and does it require additional procedures?
- If I have intermediate blockages, do I definitely need a functional test?
- Looking Forward: Integration and Accessibility
The approach to diagnosing coronary artery disease (CAD) is undergoing significant reassessment, with functional physiological testing emerging as a central pillar in clinical decision-making. According to a clinical perspective published in the New England Journal of Medicine (Volume 395, Issue 1, July 2, 2026), the field is moving beyond anatomical imaging alone toward integrated assessment of coronary blood flow and vessel function. This shift reflects growing evidence that angiographic lesion severity—the appearance of blockages on imaging—does not always predict whether a patient will benefit from intervention.
Key takeaways
- Functional assessment using techniques like fractional flow reserve (FFR) improves diagnostic accuracy by determining whether coronary lesions actually limit blood flow
- Anatomical imaging alone (angiography, CT coronary angiography) can overestimate clinical significance of lesions, leading to unnecessary interventions
- Integrating physiological testing into CAD evaluation protocols reduces revascularisation procedures while maintaining or improving patient outcomes
- Guidelines from major cardiology societies now recommend functional testing for intermediate-severity lesions (40–90% diameter stenosis)
Diagnostic Accuracy: Anatomy Alone vs. Anatomy Plus Physiology
How functional testing improves prediction of outcomes in intermediate coronary lesions
Illustration of diagnostic accuracy rates (%), comparing anatomical assessment with integrated physiological measures. Representative synthesis from functional cardiology literature as discussed in NEJM (2026). Data for educational purposes. GMJ News
The Anatomy Problem: Why Looks Can Deceive
For decades, cardiologists have relied on coronary angiography—visual inspection of coronary arteries—to determine which patients need intervention. However, a fundamental mismatch exists between the appearance of a lesion and its actual haemodynamic significance. Two patients with visually identical 70% diameter stenosis may have vastly different responses: one vessel may be severely restricting blood flow, while another maintains adequate perfusion due to collateral circulation or physiological compensation. The NEJM clinical perspective highlights that this anatomy-function disconnect has driven unnecessary coronary interventions, exposing patients to procedural risks without corresponding clinical benefit.
Modern computed tomography coronary angiography (CTCA) provides superior spatial resolution compared to invasive angiography, yet it too suffers from limited prognostic value when used as a stand-alone diagnostic tool. A lesion that appears moderate on imaging may be functionally critical, or conversely, a visually severe lesion may be physiologically silent. This diagnostic uncertainty has created a rationale for functional assessment methods that directly measure coronary physiology.
Functional Assessment: Measuring What Matters
Fractional flow reserve (FFR) is the most widely adopted physiological index in clinical practice. Measured during coronary angiography, FFR quantifies the ratio of blood pressure distal to a coronary lesion versus proximal pressure, providing a direct measure of blood flow restriction. According to the NEJM analysis, FFR-guided intervention decisions reduce unnecessary revascularisations by approximately 20–30% compared to anatomy-guided approaches, while maintaining equivalent or superior clinical outcomes in terms of symptom relief and event-free survival.
Beyond FFR, emerging indices offer complementary information. Coronary flow reserve (CFR) reflects the ability of the entire coronary circulation (microvasculature plus epicardial vessels) to increase blood flow during stress—a measure particularly valuable in patients with microvascular disease or diffuse atherosclerosis. Index of microvascular resistance (IMR) isolates resistance in the distal microvasculature, helping identify patients with primary microvascular dysfunction rather than epicardial obstruction. The clinical perspective notes that multi-parameter assessment—combining FFR with CFR or IMR—provides the most granular understanding of coronary pathophysiology and guides targeted therapies, whether epicardial revascularisation or microvascular-directed pharmacotherapy.
Guideline Evolution and Clinical Implementation
Major cardiology societies—including the European Society of Cardiology and the American College of Cardiology—have progressively integrated functional testing into diagnostic algorithms. For lesions with 40–90% diameter stenosis (the “grey zone” where anatomy alone is diagnostically ambiguous), functional assessment is now recommended as a standard decision-making tool before committing patients to revascularisation. The NEJM editorial framework emphasises that this evidence-based approach has several benefits: it reduces procedure-related morbidity, lowers healthcare costs by avoiding unnecessary interventions, and ensures that revascularisation is reserved for lesions that are functionally significant and symptomatic.
Implementation varies by healthcare setting and technology availability. In centres with catheterisation laboratory infrastructure, invasive FFR during diagnostic angiography remains the gold standard. In primary care and hospital settings without immediate catheterisation access, non-invasive approaches—including FFR derived from CTCA images (FFRCT) and stress echocardiography—provide accessible alternatives. The integration of artificial intelligence and machine learning into FFRCT analysis has improved reproducibility and turnaround time, making physiological assessment feasible in routine clinical workflows across diverse settings.
Functional physiological testing, particularly fractional flow reserve, improves diagnostic accuracy and reduces unnecessary coronary interventions while maintaining clinical efficacy in symptomatic patients with intermediate-severity coronary lesions.
— Clinical perspective, New England Journal of Medicine, Volume 395, Issue 1 (July 2, 2026)
Clinical and Public Health Implications
This diagnostic paradigm shift carries profound implications for healthcare systems. At a population level, integrating functional assessment into CAD diagnostic pathways could reduce the annual burden of unnecessary percutaneous coronary interventions by millions globally, with corresponding reductions in procedural complications (myocardial infarction, bleeding, coronary perforation) and hospitalisation costs. For individual patients, functional testing personalises risk stratification: those with non-significant lesions (FFR >0.80) can avoid intervention and be managed medically, while those with truly haemodynamically significant disease receive timely revascularisation.
The broader implication extends to equity and access. In resource-constrained healthcare systems, prioritising functional assessment ensures that limited interventional cardiology capacity is directed toward patients with the greatest clinical need, maximising population health benefits per unit healthcare resource. For more information on clinical decision-making in coronary disease, see our Clinical Updates section.
What this means
Frequently asked questions
What is fractional flow reserve (FFR), and how is it different from angiography?
Angiography shows the anatomical appearance of coronary arteries—how narrow they look on X-ray. FFR measures the actual physiological effect of that narrowing on blood flow by comparing pressure before and after the lesion. A patient can have a visually impressive blockage that doesn’t meaningfully restrict blood flow (FFR >0.80 = not significant), or a subtle-looking lesion that severely impairs flow (FFR
Is FFR testing safe, and does it require additional procedures?
FFR assessment is performed during standard coronary angiography using a special pressure-measuring guide wire, adding minimal procedural time and risk beyond diagnostic catheterisation. The guide wire is thin, and the pressure measurements are instantaneous. Complication rates are extremely low and equivalent to diagnostic angiography alone. Many patients can proceed directly from diagnostic FFR assessment to intervention in the same procedure if significant lesions are identified.
If I have intermediate blockages, do I definitely need a functional test?
Current guidelines recommend functional testing for lesions with 40–90% diameter stenosis—the “grey zone” where anatomy is ambiguous. If you have symptoms (chest pain, shortness of breath with exertion), a functional test helps confirm whether the blockage is responsible and warrants intervention. If you are asymptomatic or have minimal symptoms, functional assessment guides a more conservative approach, often avoiding unnecessary procedures. Your cardiologist will individualise the decision based on symptoms, risk factors, and imaging findings. See our patient guide section for more personalised information.
Looking Forward: Integration and Accessibility
The trajectory of CAD diagnosis points toward seamless integration of anatomical and physiological assessment in routine clinical care. Advances in non-invasive FFR derived from CT images and artificial intelligence-assisted analysis promise to democratise functional testing beyond tertiary cardiac centres, bringing evidence-based decision-making to district hospitals and primary care settings worldwide. As technology evolves and clinical evidence accumulates, the combination of anatomical precision and physiological insight will continue to refine patient selection for intervention, reduce procedural morbidity, and optimise outcomes across diverse healthcare systems globally.
Source: Physiological Assessment of Coronary Artery Disease — Clinical Perspective, New England Journal of Medicine, Volume 395, Issue 1 (July 2, 2026)
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