Magnetic resonance imaging derived cardiac first pass perfusion in cryptogenic ischemic stroke in the young

Funding Acknowledgements Type of funding sources: None. Introduction Up to 50% of ischemic strokes in adults aged between 18 and 50 are cryptogenic by nature. Heart has been a hypothesised source. Purpose: Purpose of the study was to investigate the wash in and wash out of gadolinium based contrast agent in the left atrial appendage, and cardiac chambers in first pass cardiac magnetic resonance imaging. Methods The study comprised 30 patients with first-ever cryptogenic ischemic stroke and 30 age and gender matched stroke-free controls included in the prospective multicenter study Searching for Explanations for Cryptogenic Stroke in the Young: Revealing the Etiology, Triggers and Outcome (SECRETO; NCT01934725). Cardiac magnetic resonance imaging was performed on all participants with a 1.5T magnetic resonance system. Dynamic contrast enhanced T1 weighted first pass perfusion images were acquired in the superior vena cava, the left atrial appendage (Fig. 1), and the left ventricle. The images were analyzed for time-intensity curves (Fig. 2), and results were normalised to individual heart rate. Arrival times, peak times, areas under the curves, relative blood flows (defined as area under the curve/full width at half maximum), and maximum and minimum rates of bolus wash in / wash out were calculated. Results The wash in of the contrast agent bolus was similar in patients and controls. Arrival times and peak timings showed similar characteristics in patients and controls in the left atrial appendage (arrival time: 12.4 [2.3] vs. 13.5 [3.6] cardiac cycles, p = 0.657; peak time: 19.6 [5.1] vs. 19.8 [6.9] cardiac cycles, p = 0.929) and the left atrium (arrival time: 12.2 [2.8] vs. 13.0 [3.6] cardiac cycles, p = 0.535; peak time: 18.7 [5.5] vs. 18.1 [5.2] cardiac cycles, p = 0.790). Areas under under the curves and relative blood flows were similar in patients and controls. A significant difference between patients and controls was found in the wash out rate of gadolinium in the left ventricle (-28 [11] vs. -36 [13] 1/cardiac cycles, p = 0.012), indicating slightly slower wash out in the patients. Conclusions Cryptogenic ischemic stroke in the young is not associated with prolonged blood flow in the left atrial appendage or left atrium. There were no significant differences in the first pass perfusion between subjects and healthy controls. However, there might be a slight tendency for stagnation of blood flow in the left ventricles of cryptogenic stroke patients.

Initial investigation of free-breathing 3D whole-heart stress myocardial perfusion MRI

Objective: Myocardial first-pass perfusion imaging with MRI is well-established clinically. However, it is potentially weakened by limited myocardial coverage compared to nuclear medicine. Clinical evaluations of whole-heart MRI perfusion by 3D methods, while promising, have to date had the limit of breathhold requirements at stress. This work aims to develop a new free-breathing 3D myocardial perfusion method, and to test its performance in a small patient population. Methods: This work required tolerance to respiratory motion for stress investigations, and therefore employed a “stack-of-stars” hybrid Cartesian-radial MRI acquisition method. The MRI sequence was highly optimised for rapid acquisition and combined with a compressed sensing reconstruction. Stress and rest datasets were acquired in four healthy volunteers, and in six patients with coronary artery disease (CAD), which were compared against clinical reference information.Results: This free-breathing method produced datasets that appeared consistent with clinical reference data in detecting moderate-to-strong induced perfusion abnormalities. However, the majority of the mild defects identified clinically were not detected by the method, potentially due to the presence of transient myocardial artefacts present in the images. Discussion: The feasibility of detecting CAD using this 3D first-pass perfusion sequence during free-breathing is demonstrated. Good agreement on typical moderate-to-strong CAD cases is promising, however, questions still remain on the sensitivity of the technique to milder cases.

Adenosine stress native T1 mapping demonstrates impaired myocardial perfusion reserve in non-ischemic dilated cardiomyopathy

Background Impaired myocardial perfusion reserve has been demonstrated in non-ischemic dilated cardiomyopathy (NIDCM) by positron emission tomography (PET) and adenosine-stress first-pass perfusion cardiac magnetic resonance (CMR) imaging. Adenosine stress native T1 mapping is a novel CMR technique able to assess myocardial perfusion without the use of contrast agents. The aim of the present study was to determine the clinical utility of this novel CMR technique in NIDCM. Methods A total of 20 consecutive patients (mean age 61±12 years, 80% males) with diagnosis of NIDCM who consented to be enrolled in the UHSM CMR registry were included in the present study. CMR at 3T including 1. cine imaging for the assessment of LV volumes, mass and global longitudinal strain (GLS) by tissue-tracking imaging; 2. rest and stress (adenosine 140 mcg/kg/min) MOLLI T1 mapping of mid-ventricular slice for the assessment of rest and stress T1 values and T1 reactivity (ΔT1%); 3. first-pass perfusion imaging for the assessment of myocardial perfusion reserve index (MPRI) and 4. late gadolinium enhancement (LGE) imaging for the assessment of myocardial replacement fibrosis, was performed. Twenty control patients without history of known coronary artery disease and evidence of reversible ischemia or previous myocardial infarct on CMR imaging were included for comparison purposes. Results NIDCM patients had significantly higher native T1 value (1263±47 ms vs. 1234±38 ms, p=0.031), significantly lower ΔT1% (3.2±1.5% vs. 5.7±1.7%, p<0.001, Figure A), significantly lower MPRI (1.32±0.18 vs. 1.67±0.13, p<0.001) and significantly impaired GLS (−10±4% vs. −16±2%, p<0.001) as compared to controls. A significant strong relation between ΔT1% and MPRI (β=0.76, p<0.001, Figure B) and significant moderate relation between ΔT1% and GLS (β=−0.54, p<0.001) were observed. Conclusion T1 reactivity, myocardial perfusion reserve and GLS are significantly reduced in NIDCM patients compared to controls. Adenosine stress T1 mapping holds promise for detection of impaired myocardial perfusion reserve in NIDCM without the requirement for contrast agents. Funding Acknowledgement Type of funding source: None