Rationale and Objective
The objective of this study was to identify the feasibility and pitfalls of cardiothoracic magnetic resonance imaging (MRI) in intensive care unit (ICU) patients.
Materials and Methods
This retrospective study identified adult ICU patients scheduled for cardiothoracic MRIs during a 10-year study period. ICU patients scheduled for brain MRIs served as a comparison group. A chart review was performed to identify factors impacting a patient’s ability to undergo an MRI. Differences between completed and canceled examinations for both cardiothoracic and brain MRIs were evaluated. For the cardiothoracic group, clinical indications and the diagnostic value of the study performed were also identified.
Results
A total of 143 cardiothoracic MRIs and 1011 brain MRIs were requested. Cardiothoracic MRI patients were less frequently completed (52% vs 62%), more frequently men (64% vs 43%), younger (55 vs 63 years), less likely mechanically ventilated (8% vs 29%), more likely to require intravenous contrast (83% vs 23%), and had longer examination times compared to brain MRI patients (64 vs 21 minutes). Successful completion of cardiothoracic MRI was associated with lower serum creatinine, higher glomerular filtration rate, and the absence of mechanical ventilation; significant differences were not seen with regard to gender and use of vasoactive agents. Cardiothoracic MRI results were diagnostic in 69% of examinations, most frequently when performed for myocardial disease (84%) and aortic disease (33%), and less frequently for viability (33%).
Conclusions
In an ICU population, successful completion of cardiothoracic MRI is challenging but feasible in patients with intact renal function and the absence of mechanical ventilation. Examinations were most frequently diagnostic for myocardial and aortic disease indications.
Introduction
Cardiothoracic magnetic resonance imaging (MRI) is being requested with increasing frequency . Anecdotally, at our institution, we have seen an increasing number of requests for cardiothoracic MRIs in intensive care unit (ICU) patients. However, there is no literature that examines the practicality of cardiothoracic MRIs in a critically ill population.
Imaging critically ill patients presents several problems. These patients are often unstable and may be ventilator or pressor dependent, which presents logistical challenges in bringing them to the radiology department, including potential adverse events associated with transport . Although some imaging modalities can be easily brought to the patient in the unit through portable machines, including radiography, sonography, and even computed tomography (CT), portable MRI is not practically feasible for adult patients . Critically ill patients also often have renal impairment, which may preclude the intravenous use of gadolinium-based contrast agents potentially limiting the diagnostic information obtained from a cardiothoracic MRI. Critically ill patients may also not be able to tolerate long examination times and multiple breath-hold sequences, which could potentially limit the ability to get diagnostic quality imaging. Numerous studies have examined the use of other imaging in the ICU, including chest radiography, CT, positron emission tomography-CT, brain MRI, echocardiography, general sonography, cholescintigraphy, and ventilation-perfusion scintigraphy, often finding that critically ill patients can be safely imaged with diagnostic quality information .
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Materials and Methods
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Statistical Methods
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Results
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Table 1
Baseline Patient Characteristics
Characteristic Cardiothoracic MRIs ( n = 143) Brain MRIs ( n = 143)P Value Male 92 (64.3%) 61 (42.7%)0.0004 Age (y) 55 62.50.0001 Serum creatinine 1.64 1.77 0.5627 GFR (mL/min/1.73m 2 ) 61.7 64.4 0.5157 GFR class (1/2/3) 19/48/76 29/43/71 0.2928 Inotropes and vasoactive agents 8 (5.6%) 13 (9.1%) 0.3649 BP support 18 (12.6%) 10 (7.0%) 0.1628 Mechanical ventilation 12 (8.4%) 41 (28.7%)<0.0001 Intravenous contrast 118 (82.5%) 33 (23.0%)<0.0001 Exam time (min) 64 21<0.0001
BP, blood pressure; GFR, glomerular filtration rate; MRI, magnetic resonance imaging.
Bold faced values are statistically significant.
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Table 2
Comparison of Completed vs Cancelled Cardiothoracic MRI Cases
Characteristic Completed ( n = 74) Cancelled ( n = 69)P Value Male 47 (63.5%) 45 (65.2%) 0.8627 Age (y) 52.24 57.38 0.0622 Serum creatinine 1.35 1.950.0247 GFR (mL/min/1.73m 2 ) 65 58 0.1413 GFR class (1/2/3) 5/20/49 (6.8%/27.0%/66.2%) 14/21/34 (20.3%/30.4%/49.3%)0.0336 Inotropes and vasoactive agents 2 (2.7%) 6 (8.7%) 0.1551 BP support 8 (10.8%) 9 (13.0%) 0.7977 Mechanical ventilation 2 (2.7%) 11 (15.9%)0.0076
BP, blood pressure; GFR, glomerular filtration rate; MRI, magnetic resonance imaging.
Bold faced values are statistically significant.
Table 3
Reasons for Cancellation
Reason Cardiothoracic MRIs Brain MRIs # % # % Renal failure 22 31.9 10 14.9 Patient condition 16 23.2 41 61.2 Clinical decision 7 10.1 0 Consent 7 10.1 0 Alternative imaging 7 10.1 1 1.5 Technical 5 7.2 2 3.0 Unknown 3 4.3 4 6.0 Vent or pressor 2 2.9 9 13.4 Total 69 67
MRI, magnetic resonance imaging.
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Table 4
Clinical Indications for Cardiothoracic MRIs with Cancellation and Completion Rates
Indication Canceled Completed # % # % Aorta 16 38.1 26 61.9 Myocardial Disease 24 47.1 27 52.9 Arrhythmia or ARVD 6 37.5 10 62.5 Cardiomyopathy or heart failure 10 58.8 7 41.2 Endocarditis 1 100.0 0 0.0 Myocarditis 2 25.0 6 75.0 Pericardial 3 75.0 1 25.0 Sarcoid 1 25.0 3 75.0 Valve 1 100.0 0 0.0 Other 5 83.3 1 16.7 Viability 24 54.5 20 45.5
ARVD, arrhythmogenic right ventricular dysplasia; MRI, magnetic resonance imaging.
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Table 5
What Proportion of Cardiothoracic MRIs Were Useful by Clinical Indication?
Diagnostic Not Diagnostic # % # % Aorta 17 71 7 29 Viability 4 33 8 67 Other 1 100 0 — Myocardial disease 21 84 4 16 Arrhythmia or ARVD 7 78 2 22 Cardiomyopathy or heart failure 6 100 0 — Myocarditis 5 83 1 17 Pericardial 1 100 0 — Sarcoid 2 67 1 33
ARVD, arrhythmogenic right ventricular dysplasia; MRI, magnetic resonance imaging.
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Discussion
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Conclusions
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