Chapter 16: Magnetic Resonance Imaging of the Heart
Tissue characterization with mapping or weighted imaging using assessments of T1, T2, or T2* relaxation is increasingly used in cardiovascular magnetic resonance (CMR).1,2 Which of the following conditions cannot be identified by T2 or T2*-weighted imaging?
A. Myocardial edema in the setting of acute myocardial infarction (MI)
B. Myocardial edema in the setting of myocarditis
D. Iron-overload cardiomyopathy
The answer is E. (Hurst’s The Heart, 14th Edition, Chap. 16) High signal on T2-weighted imaging can demonstrate myocardial edema, such as in the setting of acute MI or myocarditis. T2*-weighted imaging is sensitive to iron in the heart and can identify iron overload cardiomyopathy and myocardial hemorrhage in the setting of acute MI.
Although a relatively safe imaging modality, CMR does have the potential for serious and even lethal events. Which of the following statements regarding the safety of common metallic implants and electronic devices commonly found in cardiac patients is false?
A. Current coronary stents are safe and can be imaged immediately after implantation
B. Current prosthetic valves are safe and can be imaged immediately after implantation
C. Weakly ferromagnetic implants are safe and can be imaged immediately after implantation
D. Swan-Ganz catheters contain metal and are considered unsafe
E. Transdermal patches may need to be removed before the procedure
The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 16) All current coronary stents and prosthetic valves are safe and can be imaged immediately after implantation. Many other cardiac or vascular implants are nonferromagnetic and can also be scanned at any time, or they are weakly ferromagnetic and a delay of 6 weeks before MRI is recommended to allow for endothelialization. Swan-Ganz catheters contain metal and are considered unsafe. Similarly, some medication patches (including transdermal patches) contain metallic foil and may need to be removed before the procedure.
CMR is unique in that, with a single imaging modality, one can identify abnormalities of myocardial perfusion or wall motion with a relatively high spatial resolution and without ionizing radiation. Based on multimodality appropriate use criteria, in which of the following patients is stress CMR considered appropriate?
A. Patients presenting with chest pain at a high pretest probability of coronary artery disease (CAD)