When is an MRI of the chest indicated, particularly in patients with suspected cardiovascular or respiratory conditions, such as coronary artery disease (CAD), cardiac tumors, pulmonary embolism, or congenital heart defects, and what are the considerations for patients with a history of kidney disease or other conditions that may affect the use of contrast agents?

MRI Chest Indications

MRI of the chest is primarily indicated for comprehensive evaluation of congenital heart disease in adults, assessment of cardiac morphology and function when echocardiography is inadequate, evaluation of cardiac masses and great vessel abnormalities, and characterization of myocardial tissue including viability and perfusion—particularly in patients where radiation exposure or iodinated contrast should be avoided. 1

Primary Indications for Cardiac MRI

Congenital Heart Disease (CHD)

• Nearly all adults with known CHD require periodic imaging for disease monitoring, and all adults with suspected CHD require imaging for definitive diagnosis. 1
• MRI is ideally suited for evaluating adults with suspected or known CHD, providing high-spatial-resolution images without limitation of imaging "windows" as experienced with echocardiography. 1
• MRI demonstrates very high sensitivity (93-100%) and specificity (87-100%) for thoracic vascular anatomy, sequential cardiac anatomy, and shunt detection in CHD patients. 1
• Specific lesions where MRI excels include: bicuspid aortic valve, aortic coarctation, atrial septal defect, pulmonary valve stenosis, tetralogy of Fallot, Ebstein anomaly, coronary artery anomalies, and complex single ventricle physiology. 1

Functional and Morphological Assessment

• MRI provides accurate and reproducible measurements of both left and right ventricular size, function, stroke volume, ejection fraction, and wall motion using gradient-echo cine imaging. 1
• Phase-contrast techniques allow quantification of blood flow, calculation of pulmonary-to-systemic flow ratios (Qp/Qs), regurgitant fractions, and pressure gradients across stenotic regions. 1
• MRI is superior to transthoracic echocardiography for assessing right ventricular volumes and function, particularly important in post-operative CHD patients. 1

Vascular Pathology

• MRI excels in evaluating thoracic aortic disease, including aneurysms, coarctation, and vascular rings, without need for invasive angiography. 1, 2
• MRA chest (with or without contrast) is usually appropriate for evaluating aortopathy, connective tissue disorders, and branch pulmonary artery stenosis. 1
• MRI can accurately diagnose pulmonary and systemic venous anomalies with high sensitivity. 1

Coronary Artery Evaluation

• Cardiac-gated 3D SSFP angiography with fat suppression can visualize coronary artery origins and proximal course without contrast, though CT angiography generally provides clearer, more extensive coronary depiction. 1
• MRI with stress perfusion sequences can screen for myocardial ischemia and viability, particularly valuable in post-operative CHD patients with reimplanted coronaries. 1
• MRA chest and MRI heart function are usually appropriate for evaluating suspected congenital or acquired coronary artery abnormalities when echocardiography is inadequate. 1

Tissue Characterization

• Late gadolinium enhancement (LGE) imaging allows detection of myocardial fibrosis, scar, and viability assessment—capabilities unique to MRI. 1
• MRI provides direct tissue characterization beyond anatomic imaging, useful in cardiomyopathies and infiltrative heart disease. 3, 4

Specific Clinical Scenarios

Post-Operative CHD Monitoring

• MRI is useful for evaluating patients after palliative procedures, surgically created conduits, or reconstructed great vessels. 1
• Particularly valuable after tetralogy of Fallot repair, arterial switch operations for transposition, and Fontan procedures. 1
• Can assess systemic-to-pulmonary collateral flow in Fontan patients, which predicts outcomes. 1

When Echocardiography is Inadequate

• MRI should be the next imaging study when transthoracic echocardiography provides incomplete or inadequate assessment of cardiovascular morphology and function. 1
• Image quality is not affected by body habitus, unlike echocardiography. 1
• Can obtain images in any plane for improved 3D presentation of cardiac anatomy. 1

Cardiac Masses and Tumors

• MRI is evolving as the definitive diagnostic technique for paracardiac and intracardiac masses. 3
• Provides excellent soft tissue distinction for characterizing mediastinal masses and hilar lesions. 2

Considerations for Patients with Kidney Disease

Gadolinium Contrast Restrictions

• Gadolinium chelate contrast agents should not be used in patients with severe renal insufficiency due to risk of nephrogenic systemic fibrosis. 1
• For patients with eGFR ≥30 mL/min/1.73m², Group II gadolinium-based contrast agents can be used at the lowest diagnostic dose. 5
• For patients with eGFR <30 mL/min/1.73m², gadolinium should be avoided unless diagnostic information is essential and unavailable with non-contrast MRI or other modalities. 5

Non-Contrast Alternatives

• Many cardiac MRI sequences do not require contrast: cine imaging for function, phase-contrast for flow quantification, and 3D SSFP for vascular anatomy. 1
• Non-contrast MRA techniques using cine gradient echo and navigator respiratory-gated 3D steady-state free precession can evaluate aortic pathology. 1

Contraindications and Limitations

Absolute Contraindications

• Traditional pacemakers are generally considered an exclusion, though MRI-conditional pacemakers now exist and MRI can be performed under rigorously safe conditions. 1
• Severe gadolinium allergy (when contrast is required). 1

Relative Limitations

• Claustrophobia may require sedation in some patients. 1
• Detection of calcification is problematic—patients with homografts or bioprosthetic valved conduits where calcification detection is important may not be optimally imaged. 1
• MRI is probably less accurate than color flow Doppler for visualizing small ventricular and atrial septal defects. 1
• Detection of valvular pathology may be better achieved with transesophageal echocardiography. 1
• Motion and respiratory artifacts may pose problems in some examinations. 1

Algorithmic Approach

Step 1: Initial evaluation with transthoracic echocardiography remains first-line for suspected cardiac pathology. 1

Step 2: If echocardiography is inadequate or incomplete for assessing:

• Complex CHD anatomy → MRI heart function and morphology ± MRA chest 1
• Ventricular function and volumes → MRI heart function and morphology 1
• Great vessel pathology → MRA chest 1
• Coronary anomalies → Consider CTA coronary arteries (superior resolution) or MRA chest 1

Step 3: For patients with renal insufficiency (eGFR <30), prioritize non-contrast MRI sequences or consider alternative imaging (echocardiography, non-contrast CT). 1, 5

Step 4: Cardiac MRI studies require supervision by a physician who understands the clinical question to acquire appropriate and optimal imaging—essential for consistency and reliable data. 1

Common Pitfalls to Avoid

• Do not order MRI without first attempting echocardiography, as echo remains the first-line modality and may provide all necessary information. 1
• Do not assume all pacemakers are MRI-incompatible—verify device specifications as many modern devices are MRI-conditional. 1
• Do not use gadolinium contrast in patients with severe renal insufficiency (eGFR <30) without careful risk-benefit assessment. 1, 5
• Do not rely on MRI alone for small septal defects or detailed valvular pathology—echocardiography may be superior. 1
• Do not forget that CT angiography provides superior coronary artery visualization compared to MRI, though MRI avoids radiation. 1