Advanced Cardiac Imaging
Cardiac MRI — CMR Scanning
The gold standard for cardiac structure, function, and tissue characterisation. Stress perfusion CMR detects ischaemia with exceptional precision; late gadolinium enhancement identifies myocardial scar and guides decisions about revascularisation — all without radiation.
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The Gold Standard
What Is Cardiac MRI?
Cardiovascular magnetic resonance imaging (CMR) uses powerful magnetic fields and radiofrequency pulses — not ionising radiation — to produce exquisitely detailed images of the heart. It is considered the gold standard for measuring cardiac volumes and ejection fraction with accuracy superior to echocardiography, and is the only widely available technique capable of distinguishing different types of myocardial tissue — normal muscle, oedema, fibrosis, scar, fat infiltration, and inflammation.
CMR is not a single test — it is a highly versatile protocol that can be tailored to answer specific clinical questions. In a single 45–75 minute examination, it can simultaneously assess cardiac structure and function, detect and localise ischaemia under stress, quantify myocardial scar, characterise tissue composition, and map the distribution of fibrosis. No other cardiac imaging modality combines this breadth of information in one session.
CMR has no ionising radiation, making it particularly suitable for patients requiring serial monitoring, younger patients, and those in whom repeated radiation exposure from CT would be a concern.
What CMR Can Do
Three Core CMR Capabilities
Depending on your clinical question, Dr Nijjer will request a protocol that combines one or more of the following techniques. Each targets a different aspect of cardiac pathology and together they make CMR the most comprehensive cardiac investigation available.
Core Protocol
Cardiac Function & Structure
Cine CMR — real-time moving images of the beating heart
Cine CMR uses a rapid acquisition technique gated to your ECG to produce crystal-clear moving images of the heart throughout the entire cardiac cycle. Volumes are measured with sub-millilitre precision, making it the reference standard against which echocardiography is calibrated in research settings.
Ejection fraction, stroke volume, cardiac output, atrial dimensions, ventricular wall thickness, and ventricular mass are all measured volumetrically in three dimensions — far more accurate than the geometric assumptions required by ultrasound.
- Accurate LVEF measurement — cardiomyopathy, heart failure monitoring
- Right ventricular function assessment (ARVC, pulmonary hypertension)
- Congenital heart disease anatomy and haemodynamics
- Phase-contrast flow quantification for valve regurgitation
- Ventricular mass in hypertrophic cardiomyopathy (HCM)
Ischaemia Detection
Stress Perfusion CMR
Adenosine or regadenoson vasodilator stress with first-pass gadolinium
Stress perfusion CMR detects coronary ischaemia by imaging the passage of gadolinium contrast through the myocardium at rest and under pharmacological stress. A vasodilator agent (adenosine or regadenoson) is infused to maximally dilate the coronary vasculature. In territories supplied by a significantly narrowed artery, perfusion is reduced relative to normal myocardium — appearing as a dark region on first-pass imaging.
The spatial resolution of stress perfusion CMR is superior to nuclear perfusion imaging (SPECT), and its accuracy for detecting obstructive coronary artery disease is outstanding. It can localise ischaemia to specific coronary territories and estimate the proportion of myocardium at risk — directly informing decisions about angioplasty.
- Diagnosis of ischaemia when CTCA is equivocal
- Unable to exercise adequately for treadmill or stress echo
- Assessment of ischaemia extent before revascularisation planning
- Post-stenting assessment of residual ischaemia
- Microvascular disease — normal epicardial arteries but ischaemic perfusion pattern
Scar & Viability
Late Gadolinium Enhancement
LGE — myocardial fibrosis, infarct, and inflammation mapping
Ten to fifteen minutes after gadolinium contrast injection, the normal myocardium has washed out the contrast agent, while damaged, scarred, or fibrotic tissue retains it. These abnormal regions appear bright white — a finding called late gadolinium enhancement (LGE). The pattern of LGE is pathognomonic: its distribution and transmurality tell the clinician not just that damage is present, but what caused it.
In ischaemic disease, LGE begins at the subendocardium (innermost layer, the most vulnerable to ischaemia) and spreads outward. The transmurality of LGE directly predicts viability: segments with less than 25% transmural scar are likely to recover function after revascularisation; those with more than 75% transmural scar will not — a critical guide to whether bypass surgery or angioplasty is worth undertaking.
- Myocardial infarction — extent, transmurality, microvascular obstruction
- Viability assessment before revascularisation
- Myocarditis — non-ischaemic midwall or epicardial pattern
- HCM fibrosis — extent predicts arrhythmic risk and ICD need
- Cardiac sarcoidosis, amyloidosis, ARVC fat infiltration
Ischaemia Testing
Stress Perfusion CMR — Detecting Ischaemia
How the Test Works
An adenosine infusion dilates the coronary vasculature maximally, dramatically increasing blood flow in normal coronary territories. In a stenosed artery, the vessel is already near-maximally dilated at rest to compensate — it cannot respond to adenosine, so the downstream myocardium receives relatively less blood compared with normal regions.
As gadolinium contrast is injected, it passes first into well-perfused regions and appears bright. Ischaemic territories receive less contrast and appear dark — a perfusion defect. By comparing stress and rest images side by side, even subtle subendocardial ischaemia invisible on ECG or wall motion assessment can be detected. The test is typically 45–60 minutes in total.
Side effects of adenosine (mild chest tightness, flushing, breathlessness) are common but transient — adenosine has a half-life of less than 10 seconds and symptoms resolve within moments of stopping the infusion. Regadenoson requires a single injection rather than a continuous infusion and is used when adenosine is poorly tolerated.
- CE-MARC trial (NEJM 2012): CMR sensitivity 87% vs SPECT 74% for detecting ≥70% stenosis in 752 patients. CMR specificity 83% vs 61%.
- CE-MARC 2 (JAMA 2016): Stress perfusion CMR-guided strategy led to fewer unnecessary angiograms than NICE-guideline-guided care (perfusion CMR 7.5% vs 28.8% unnecessary angiograms).
- MR-INFORM (NEJM 2018): CMR-guided PCI had equivalent 1-year outcomes to iFR-guided PCI, validating CMR as a physiologically valid decision-making tool for revascularisation.
Performance Statistics
87%
Sensitivity for detecting obstructive coronary disease (CE-MARC)
83%
Specificity — superior to SPECT nuclear imaging
<1%
Annual event rate with a normal stress perfusion CMR result
0 mSv
Ionising radiation — no cumulative radiation dose
Stress perfusion CMR is recommended by both the ESC (2019 Chronic Coronary Syndrome guidelines) and NICE (CG95) as an appropriate non-invasive test for investigating stable chest pain with suspected ischaemic aetiology. It is particularly valuable when CTCA is non-diagnostic due to heavy calcification or prior stenting.
Myocardial Scar & Recovery
Viability Assessment with Late Gadolinium Enhancement
What Is Myocardial Viability?
After a heart attack — or in patients with severely diseased coronary arteries — segments of the heart muscle may contract poorly or not at all. This dysfunction is not always permanent. Some segments are ischaemic but still alive (stunned or hibernating myocardium), and will recover normal contraction if blood supply is restored by coronary angioplasty or bypass surgery.
Other segments contain full-thickness scar — dead tissue that cannot recover regardless of what is done. The clinical question — "Is there viable myocardium to justify the risks of revascularisation?" — is one of the most important in cardiology, and LGE-CMR is the most accurate tool available to answer it.
- LGE <25% transmurality: viable, very likely to recover after revascularisation
- LGE 25–50% transmurality: intermediate — recovery possible but uncertain
- LGE 51–75% transmurality: unlikely to recover but may still benefit from revascularisation
- LGE >75% transmurality: full-thickness scar — will not recover; revascularisation not indicated for that territory
LGE Patterns and Their Meaning
The distribution of LGE is as important as its extent. Different patterns are associated with different underlying conditions:
- Subendocardial or transmural, following a coronary distribution: ischaemic scar from previous myocardial infarction. The territory corresponds to a specific coronary artery.
- Mid-wall (intramural), non-coronary distribution: non-ischaemic cardiomyopathy. Found in dilated cardiomyopathy, myocarditis, and sarcoidosis. Does not follow a vascular territory.
- Patchy subepicardial and midwall, lateral wall: classic for myocarditis. Combined with T2 oedema imaging forms the basis of the Lake Louise diagnostic criteria.
- Diffuse global subendocardial enhancement: amyloidosis — a characteristic washing-out pattern helps confirm the diagnosis.
- Right ventricular insertion points (hinge points): small focal LGE here is common in hypertrophic cardiomyopathy and is distinct from infarct-related scar.
Beyond Structure and Function
Tissue Characterisation — What Makes CMR Unique
T1 Mapping
Native T1 & ECV
Measures the relaxation time of myocardial tissue. Elevated native T1 indicates oedema or fibrosis; elevated extracellular volume fraction (ECV) quantifies diffuse interstitial fibrosis — important in hypertension, aortic stenosis, and amyloidosis, where standard LGE may be normal but diffuse fibrosis is present.
T2 Mapping
Oedema & inflammation
T2 is sensitive to myocardial water content. Elevated T2 indicates acute oedema — a hallmark of acute myocarditis, Takotsubo cardiomyopathy, or recent infarction. T2 mapping allows precise regional localisation of inflammation, forming part of the Lake Louise criteria for myocarditis diagnosis.
T2* Mapping
Iron overload quantification
T2* (T2 star) relaxometry detects and quantifies iron deposition in the myocardium. Essential for monitoring patients with thalassaemia major, haemochromatosis, or sickle cell disease who are at risk of iron-related cardiomyopathy. Serial T2* measurements guide chelation therapy decisions.
Fat Suppression
Lipomatous infiltration
Fat-suppression sequences identify lipomatous infiltration of the right ventricle in arrhythmogenic right ventricular cardiomyopathy (ARVC), assess intracardiac lipomas, and help characterise pericardial disease. Combined with cine and LGE imaging, this sequence plays an important role in diagnosing ARVC.
Clinical Applications
When Is Cardiac MRI Requested?
Suspected Angina / Ischaemia
Stress perfusion CMR is recommended when exercise testing is non-diagnostic, when CTCA shows equivocal intermediate stenoses, or when there is suspected microvascular or vasospastic angina with normal epicardial arteries.
Cardiomyopathy
The investigation of choice for hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), restrictive cardiomyopathy, and arrhythmogenic cardiomyopathy (ARVC). LGE extent in HCM is a key component of SCD risk stratification for ICD decisions.
Myocarditis
CMR is the non-invasive diagnostic standard for myocarditis. Lake Louise criteria — T2 oedema plus non-ischaemic LGE pattern — have high sensitivity and specificity, often avoiding the need for endomyocardial biopsy in clinical practice.
Viability Before Revascularisation
Before coronary angioplasty or bypass surgery in patients with severely impaired LV function, LGE-CMR determines whether viable myocardium is present in dysfunctional territories — confirming that revascularisation is likely to improve function and prognosis.
Cardiac Sarcoidosis & Infiltrative Disease
The patchy LGE distribution of cardiac sarcoidosis, the global subendocardial enhancement of amyloidosis, and the T1/ECV findings of haemochromatosis are all characterised with high accuracy — guiding diagnosis and immunosuppressive treatment decisions.
Congenital Heart Disease
CMR is the preferred modality for follow-up of adult congenital heart disease — particularly repaired tetralogy of Fallot, pulmonary regurgitation assessment, Fontan circulation, and aortic coarctation. Right ventricular volumes, which are poorly assessed by echo, are accurately measured.
Before Your Scan
How to Prepare
For a Stress Perfusion CMR
- No caffeine for 24 hours before the scan — caffeine blocks adenosine receptors and will completely negate the vasodilator effect, making the stress test non-diagnostic. This includes coffee, tea, energy drinks, and caffeine-containing medications.
- Avoid theophylline (found in some inhalers) for 24 hours before the test.
- Beta-blockers and calcium channel blockers do not need to be stopped for a perfusion CMR — unlike for exercise testing or dobutamine stress echo.
- You may eat a light meal before the scan.
- The scan takes 60–75 minutes. Bring any previous cardiac reports or imaging discs.
General MRI Information
- Pacemakers and ICDs: Most modern devices are MR-conditional and compatible with 1.5 Tesla scanning. Your device details will be checked before booking. Some older devices are contraindicated — Dr Nijjer will advise whether an alternative test is needed.
- Metallic implants: Most orthopaedic implants, heart valves, and stents are MRI-compatible. A detailed implant history is taken before the scan. Ferromagnetic fragments or cochlear implants require individual assessment.
- Gadolinium contrast: Not used in severe renal impairment (eGFR <30). Kidney function is checked beforehand if clinically indicated. Gadolinium-based contrast is safe in the vast majority of patients.
- Pregnancy: CMR without gadolinium is considered safe in all trimesters when clinically necessary. Gadolinium should be avoided unless the benefit clearly outweighs any theoretical risk.
Claustrophobia: The MRI bore is a narrow tunnel and the scan is noisy. If you experience claustrophobia, please mention this when booking. Oral anxiolytic pre-medication can be arranged. Modern wide-bore scanners (70cm bore diameter) significantly reduce discomfort for the majority of patients. Open MRI scanners are also available for patients where standard MRI is not possible, although image quality is lower.
Need the Most Comprehensive
Cardiac Investigation Available?
Cardiac MRI provides answers that no other single test can match. Dr Nijjer will select the appropriate CMR protocol for your clinical question and ensure you understand the results in full.