MR perfusion and delayed enhancement imaging in the heart

The value of stress perfusion cardiovascular magnetic resonance imaging for patients referred from the adult congenital heart disease clinic: 5-year experience at the Toronto General Hospital

BACKGROUND

Vasodilator stress perfusion cardiovascular magnetic resonance imaging is a clinically useful tool for detection of clinically significant myocardial ischaemia in adults. We report our 5-year retrospective experience with perfusion cardiovascular magnetic resonance in a large, quarternary adult congenital heart disease centre.

METHODS

We reviewed all cases of perfusion cardiovascular magnetic resonance in patients referred from the adult congenital heart disease service. Dipyridamole stress perfusion cardiovascular magnetic resonance was undertaken on commercially available 1.5 and 3 T cardiovascular magnetic resonance scanners. Late gadolinium enhancement imaging was performed 8-10 minutes after completion of the rest perfusion sequence. Navigator whole-heart coronary magnetic resonance angiography was also performed where feasible. RESULTS of stress cardiovascular magnetic resonance were correlated with complementary imaging studies, surgery, and clinical outcomes.

RESULTS

Over 5 years, we performed 34 stress perfusion cardiovascular magnetic resonance examinations (11 positive). In all, 84% of patients had further investigations for ischaemia in addition to cardiovascular magnetic resonance. Within a subgroup of 19 patients who had definitive alternative assessment of their coronary arteries, stress perfusion cardiovascular magnetic resonance demonstrated a sensitivity of 82% and specificity of 100%. Of the 34 studies, two were false negatives, in which the aetiology of ischaemia was extrinsic arterial compression rather than intrinsic coronary luminal narrowing. Coronary abnormalities were identified in 71% of cases who had coronary magnetic resonance angiography.

CONCLUSION

Stress perfusion cardiovascular magnetic resonance is a useful and accurate tool for investigation of myocardial ischaemia in an adult congenital heart disease population with suspected non-atherosclerotic coronary abnormalities.

Performance of adenosine "stress-only" perfusion MRI in patients without a history of myocardial infarction: a clinical outcome study

To assess the diagnostic value of adenosine “stress-only” myocardial perfusion MR for ischemia detection as an indicator for coronary angiography in patients without a prior myocardial infarction and a necessity to exclude ischemia. Adenosine perfusion MRI was performed at 1.5 T in 139 patients with a suspicion of ischemia and no prior myocardial infarction. After 3 min of adenosine infusion a perfusion sequence was started. Patients with a perfusion defect were referred to coronary angiography (CAG). Patients with a normal perfusion were enrolled in follow-up. Fourteen out of 139 patients (10.1%) had a perfusion defect indicative of ischemia. These patients underwent a coronary angiogram, which showed complete agreement with the perfusion images. 125 patients with a normal myocardial perfusion entered follow-up (median 672 days, range 333–1287 days). In the first year of follow-up one Major Adverse Coronary Event (MACE) occurred and one patient had new onset chest pain with a confirmed coronary stenosis. Reaching a negative predictive value for MACE of 99.2% and for any coronary event of 98.4%. At 2 year follow-up no additional MACE occurred. Sensitivity of adenosine perfusion MR for MACE is 93.3% and specificity and positive predictive value are 100%. Adenosine myocardial perfusion MR for the detection of myocardial ischemia in a “stress-only” protocol in patients without prior myocardial infarctions, has a high diagnostic accuracy. This fast examination can play an important role in the evaluation of patients without prior myocardial infarctions and a necessity to exclude ischemia.

Inter-observer variability of visual analysis of "stress"-only adenosine first-pass myocardial perfusion imaging in relation to clinical experience and reading criteria

To assess the inter-observer agreement of adenosine “stress”-only visual analysis of perfusion MR images in relation to experience and reading criteria. 106 adenosine perfusion MR examinations out of 350, 46 consecutive positive examinations and 60 randomly selected negative examinations were visually analysed by three individual readers (two residents and a technician) with different levels of experience. Readings (blinded for any information) were compared with the reading of an expert radiologist. After a month the examinations were presented again (randomly) without knowledge regarding the first readings. This time readings were performed with the systematical use of reading criteria. Agreement with the expert reading was good for the most experienced resident (k = 0.88). Kappa was 0.48 for the least experienced, and 0.57 for the technician. After the second systematical reading inter-observer agreement increased to 0.9, 0.68 and 0.77 respectively. Overall kappa increased from 0.59 to 0.71. The use of reading criteria significantly improved the performance of the least experienced reader (P = 0.01). Visual analysis of adenosine “stress”-only first-pass perfusion MR images has moderate to very good agreement. Performance is experience related, but the systematic use of reading criteria significantly increased performance for the least experienced observer.

Myocardial perfusion magnetic resonance imaging for detecting coronary function anomalies in asymptomatic paediatric patients with a previous arterial switch operation for the transposition of great arteries

BACKGROUND

The main cause of long-term morbidity and mortality after the arterial switch operation for transposition of great arteries is complication at the coronary arteries. Myocardial perfusion magnetic resonance imaging represents a relatively novel and appealing tool for detecting myocardial ischaemia but with little experience in paediatric patients. The purpose of this paper is to report a single centre experience with myocardial perfusion magnetic resonance imaging for detecting ischaemia after the arterial switch operation for transposition of great arteries.

METHODS

Twenty-eight patients aged 13-16 years with an arterial switch operation for transposition of great arteries were included in the study. Coronary pattern, operative and postoperative complications, and long-term follow-up events were reviewed. Patient functional evaluation included clinical examination, electrocardiogram and echocardiogram. Every patient underwent magnetic resonance imaging perfusion scanning at rest and under adenosine-induced stress.

RESULTS

All patients were symptom free with no ischaemic signs on the electrocardiogram. All magnetic resonance imaging examinations were generally well tolerated with minor adenosine secondary effects in 36% of the patients. Two stress myocardial perfusion magnetic resonance studies were excluded from analysis for technical reasons. No perfusion stress defects were detected at the remaining 26. Myocardial delayed enhancement was performed in all 28 patients. In five subjects, a subendocardial late enhancement consistent with patch tissue for septal defect closure at the time of repair was indentified.

CONCLUSION

Magnetic resonance imaging evaluation of myocardial perfusion and viability is feasible in paediatric patients long after arterial switch operation. No signs of myocardial ischaemia or necrosis were documented in this young asymptomatic population. Further studies including coronary angiography correlation are needed to validate magnetic resonance imaging results.

Cardiac magnetic resonance imaging: diagnostic value and utility in the follow-up of patients with acute myocarditis mimicking myocardial infarction

PURPOSE

The aim of our study was to evaluate the efficacy of magnetic resonance imaging (MRI) in the differential diagnosis between active myocarditis and myocardial infarction in patients with clinical symptoms mimicking acute myocardial infarction.

MATERIALS AND METHODS

Between 1 January 2006 and 30 June 2007, 23 consecutive patients (21 men and 2 women) presenting with electrocardiographic abnormalities mimicking acute myocardial infarction and a clinical suspicion of acute myocarditis (fever, chest pain and elevated troponin levels) underwent contrast-enhanced cardiac MRI within a week of admission. All patients also underwent coronary angiography, which demonstrated the absence of significant coronary artery lesions. The mean follow-up period was 2+/-4 months.

RESULTS

Cardiac MRI with injection of contrast material showed late subepicardial and intramyocardial enhancement in all patients. Subendocardial late enhancement, a typical pattern of myocardial infarction, was never seen. In addition, in agreement with the literature, there was prevalent involvement of the lateral segments of the left ventricular wall.

CONCLUSIONS

Cardiac MRI could be a valuable tool for the early diagnosis of acute myocarditis, as it can demonstrate specific patterns that help rule out acute myocardial infarction.

Cardiac MRI of ischemic heart disease at 3 T: potential and challenges

Cardiac MRI has become a routinely used imaging modality in the diagnosis of cardiovascular disease and is considered the clinically accepted gold standard modality for the assessment of cardiac function and myocardial viability. In recent years, commercially available clinical scanners with a higher magnetic field strength (3.0 T) and dedicated multi-element coils have become available. The superior signal-to-noise ratio (SNR) of these systems has lead to their rapid acceptance in cranial and musculoskeletal MRI while the adoption of 3.0 T for cardiovascular imaging has been somewhat slower. This review article describes the benefits and pitfalls of magnetic resonance imaging of ischemic heart disease at higher field strengths. The fundamental changes in parameters such as SNR, transversal and longitudinal relaxation times, susceptibility artifacts, RF (B1) inhomogeneity, and specific absorption rate are discussed. We also review approaches to avoid compromised image quality such as banding artifacts and inconsistent or suboptimal flip angles. Imaging sequences for the assessment of cardiac function with CINE balanced SSFP imaging and MR tagging, myocardial perfusion, and delayed enhancement and their adjustments for higher field imaging are explained in detail along with several clinical examples. We also explore the use of parallel imaging at 3.0 T to improve cardiac imaging by trading the SNR gain for higher field strengths for acquisition speed with increased coverage or improved spatial and temporal resolution. This approach is particularly useful for dynamic applications that are usually limited to the duration of a single breath-hold.

Ischaemic and non-ischaemic cardiomyopathies—cardiac MRI appearances with delayed enhancement

Over the past few years, cardiovascular magnetic resonance (CMR) imaging has rapidly developed and is now a robust clinical tool capable of providing high-resolution images of the heart in any desired plane. Delayed contrast-enhanced CMR (DE-CMR) can be used for non-invasive tissue characterization, with differing patterns of hyperenhancement displayed by ischaemic and non-ischaemic cardiomyopathies. This review explains the theory behind delayed hyperenhancement, and demonstrates the potential of DE-CMR in the diagnosis of a wide range of different cardiac disease states.