Skip to textbook content
Doctor’s PassportTextbook
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
← Cardiology indexChapter sections
Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
Full textbook9 sectionsOpen only what you need
Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Cardiac MRI and nuclear imaging

Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull

Purpose and principles

Select CMR, SPECT or PET for ventricular function, tissue characterisation, perfusion, viability and infiltrative disease while managing contrast, device and radiation constraints.

CMR is particularly valuable when echo images are inadequate or when myocarditis, infarction pattern, infiltrative disease, cardiomyopathy, ventricular thrombus or viability is the question. Breath-hold, rhythm and patient tolerance affect quality.

Nuclear imaging trades radiation exposure for sensitive perfusion and molecular information. SPECT is widely available; PET offers higher resolution and quantitative flow but is less available.

Select the modality by the unanswered decision, contraindications and local expertise. A technically limited study should be labelled as such and redirected rather than over-interpreted.

Key points

  • CMR provides accurate biventricular volumes, function and tissue characterisation without ionising radiation.
  • Late gadolinium enhancement pattern helps distinguish ischaemic scar from many non-ischaemic cardiomyopathies but is not a diagnosis in isolation.
  • Stress CMR, SPECT and PET can demonstrate inducible perfusion abnormality; PET can quantify myocardial blood flow in specialist practice.
  • SPECT compares relative tracer uptake, so attenuation artefact and balanced multivessel ischaemia can conceal disease.
  • Check the exact implanted device and leads for MR conditions; 'pacemaker' is not automatically an absolute contraindication.
  • Use the lowest-risk suitable gadolinium agent and screen renal function and pregnancy according to the product and MHRA safety guidance.
  • Justify ionising-radiation studies, optimise dose and avoid duplicate functional tests that will not change management.

Indications, selection and cautions

Ischaemic scar pattern

Subendocardial or transmural late enhancement following a coronary territory supports infarction; transmural extent affects likelihood of functional recovery.

Non-ischaemic injury pattern

Mid-wall, subepicardial or patchy enhancement may suggest myocarditis or cardiomyopathy, but distribution, oedema and clinical context are required.

Reversible perfusion defect

Stress abnormality that normalises at rest supports inducible ischaemia; a fixed defect may be scar or artefact.

Extensive ischaemia or severe dysfunctionRed flag

Large inducible burden, marked biventricular dysfunction or a mechanical complication requires prompt specialist action.

Tracer or contrast reactionRed flag

New airway, breathing or circulatory compromise during injection requires immediate emergency management and documentation.

Method and interpretation

  1. 01
    Cine CMRFirst step
    Why
    Quantify chamber volumes, mass and biventricular ejection fraction.
    Interpretation and limitations
    Highly reproducible when contours and rhythm are adequate; compare serial studies using consistent methods.
  2. 02
    Tissue-characterisation CMR
    Why
    Assess oedema, fibrosis, infiltration, thrombus and infarct pattern using mapping and late enhancement.
    Interpretation and limitations
    Pattern narrows mechanism but must be integrated with timing, biomarkers, coronary anatomy and clinical phenotype.
  3. 03
    Stress perfusion CMR
    Why
    Detect inducible myocardial hypoperfusion without ionising radiation.
    Interpretation and limitations
    Check stress adequacy and distinguish dark-rim artefact from a reproducible coronary or subendocardial defect.
  4. 04
    SPECT myocardial perfusion imaging
    Why
    Assess relative perfusion, scar and gated ventricular function.
    Interpretation and limitations
    Review raw data, attenuation and motion; normal relative perfusion can miss balanced global reduction.
  5. 05
    PET perfusion or metabolic imaging
    Why
    Quantify flow or assess selected inflammatory, infiltrative and viability questions.

Clinical next steps

01Preferred routeSuspected cardiomyopathy or myocarditisFirst stepPreferredUnexplained ventricular dysfunction, arrhythmia or myocardial injury+
  1. 1Obtain ECG, biomarkers and comprehensive echocardiography and address acute instability.
  2. 2Use CMR when tissue characterisation or accurate biventricular assessment will change diagnosis or management.
  3. 3Review device compatibility, renal function, pregnancy possibility and tolerance before scanning.
  4. 4EscalationEscalate high-risk arrhythmia, severe dysfunction or active inflammation findings through specialist pathways.
02AlternativeFunctional ischaemia imagingAlternativeCTCA is uncertain or functional significance is required+

Risks, monitoring and follow-up

  • Verify device model, leads, MR conditions and pre/post-scan device checks where applicable.
  • Assess renal function and pregnancy status when contrast or ionising radiation is planned.
  • During pharmacological stress monitor rhythm, blood pressure, symptoms and oxygen saturation with resuscitation capability.
  • Record administered activity, radiation dose metrics or gadolinium product and dose.
  • Ensure important findings and any reaction are directly communicated and entered in the patient record.

Special situations

Pattern beats presence

Late enhancement is informative because of its distribution, not merely because enhancement exists.

CMR can detect small infarcts

Subendocardial scar may be visible even when global ejection fraction is preserved.

PET flow reserve adds physiology

A global reduction can support diffuse coronary or microvascular dysfunction when focal relative defects are absent.

Fixed SPECT defect is not always scar

Attenuation, motion and subdiaphragmatic activity must be reviewed before calling infarction.

Device labels are conditional

Many systems are MR conditional only when the generator-lead combination, scanner and programming requirements are met.

Common pitfalls

  1. 01

    Treating any non-ischaemic late-enhancement pattern as diagnostic of myocarditis.

  2. 02

    Calling a normal relative SPECT study reassuring without considering balanced ischaemia or poor stress.

  3. 03

    Refusing all CMR solely because a cardiac device is present.

  4. 04

    Giving gadolinium without checking product-specific renal and pregnancy precautions.

  5. 05

    Ordering both SPECT and stress CMR without a distinct unanswered decision.

Practice

Two practice questions

Your practice draft is saved in this browser.

Question 1 of 2
0 correct
CardiologyOriginal SBA

Infarct pattern on CMR

A patient undergoes cardiac MRI to investigate a suspected previous myocardial infarction. Which late-gadolinium-enhancement pattern most strongly supports an ischaemic infarct?

Choose one answer, then submit
← Rapid synopsisBack to overviewAll Cardiology topics →
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE CG95: Recent-onset chest pain
  • NICE NG106: Chronic heart failure in adults
  • MHRA: Gadolinium contrast restrictions and safety
  • ESC/EACVI cardiovascular imaging consensus documents
  • ESC 2024 Guidelines for chronic coronary syndromes

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
Interpretation and limitations
Preparation is indication-specific; failed suppression or tracer protocol can make the study non-diagnostic.
1
Choose stress CMR, SPECT or PET from renal function, device, radiation, rhythm, body habitus and availability.
  • 2Follow the modality-specific stress preparation and document adequate stress.
  • 3Report ischaemic burden, scar, ventricular function and technical limitations.
  • 4Correlate with coronary anatomy before invasive or revascularisation decisions.
    • 03EscalationNon-diagnostic or unsafe studyEscalationDevice conditions cannot be met, renal or pregnancy risk is unacceptable, or images are inadequate+
    1. 1Stop and clarify the exact safety constraint rather than applying a blanket modality ban.
    2. 2AlternativeSelect a non-contrast CMR sequence set or alternative echo, CT, SPECT or PET when it answers the question safely.
    3. 3Use the relevant MHRA and product-specific contrast advice.
    4. 4Document residual uncertainty and the next test or clinical decision owner.