Low-flow severe aortic stenosis (AS) has higher mortality than severe AS with normal flow. The conventional definition of low-flow AS is an indexed stroke volume (SVi) by echocardiography less than ...35 mL/m2. Cardiovascular magnetic resonance (CMR) is the reference standard for quantifying left ventricular volumes and function from which SVi by CMR can be derived.
To determine the association of left ventricular SVi by CMR with myocardial remodeling and survival among patients with severe AS after valve replacement.
This multicenter longitudinal cohort study was conducted between January 2003 and May 2015 across 6 UK cardiothoracic centers. Patients with severe AS listed for either surgical aortic valve replacement (SAVR) or transcatheter aortic valve replacement (TAVR) were included. Patients underwent preprocedural echocardiography and CMR. Patients were stratified by echocardiography-derived aortic valve mean and/or peak gradient and SVi by CMR into 4 AS endotypes: low-flow, low-gradient AS; low-flow, high-gradient AS; normal-flow, low-gradient AS; and normal-flow, high-gradient AS. Patients were observed for a median of 3.6 years. Data were analyzed from September to November 2021.
SAVR or TAVR.
All-cause and cardiovascular (CV) mortality after aortic valve intervention.
Of 674 included patients, 425 (63.1%) were male, and the median (IQR) age was 75 (66-80) years. The median (IQR) aortic valve area index was 0.4 (0.3-0.4) cm2/m2. Patients with low-flow AS endotypes (low gradient and high gradient) had lower left ventricular ejection fraction, mass, and wall thickness and increased all-cause and CV mortality than patients with normal-flow AS (all-cause mortality: hazard ratio HR, 2.08; 95% CI, 1.37-3.14; P < .001; CV mortality: HR, 3.06; 95% CI, 1.79-5.25; P < .001). CV mortality was independently associated with lower SVi (HR, 1.64; 95% CI, 1.08-2.50; P = .04), age (HR, 2.54; 95% CI, 1.29-5.01; P = .001), and higher quantity of late gadolinium enhancement (HR, 2.93; 95% CI, 1.68-5.09; P < .001). CV mortality hazard increased more rapidly in those with an SVI less than 45 mL/m2. SVi by CMR was independently associated with age, atrial fibrillation, focal scar (by late gadolinium enhancement), and parameters of cardiac remodeling (left ventricular mass and left atrial volume).
In this cohort study, SVi by CMR was associated with CV mortality after aortic valve replacement, independent of age, focal scar, and ejection fraction. The unique capability of CMR to quantify myocardial scar, combined with other prognostically important imaging biomarkers, such as SVi by CMR, may enable comprehensive stratification of postoperative risk in patients with severe symptomatic AS.
Purpose
To demonstrate the feasibility of an automatic adaptive acquisition sequence. Magnetic resonance perfusion pulse sequences often leave potential acquisition time unused in patients with lower ...heart‐rates (HR) and smaller body size.
Materials and Methods
A perfusion technique was developed that automatically adapts to HR and field‐of‐view by maximizing in‐plane spatial resolution while maintaining temporal resolution every cardiac cycle. Patients (n = 10) and volunteers (n = 10) were scanned with both a standard resolution and adaptive method. Image quality was scored, signal‐to‐noise ratio (SNR) calculated, and width of dark‐rim artifact (DRA) measured.
Results
The acquired spatial resolution of the adaptive sequence (1.92 × 1.92 mm2 ± 0.34) was higher than the standard resolution (2.42 × 2.42 mm2) (P < 0.0001). Mean DRA width was reduced using the adaptive pulse sequence (1.94 ± 0.60 mm vs. 2.82 ± 0.65 mm, P < 0.0001). The signal‐to‐noise ratio (SNR) was higher with the standard pulse sequence (6.7 ± 2.2 vs. 3.8 ± 1.8, P < 0.0001). There was no difference in image quality score between sequences in either volunteers (1.1 ± 0.31 vs. 1.0 ± 0.0, P = 0.34) or patients (1.3 ± 0.48 vs. 1.3 ± 0.48, P = 1.0).
Conclusion
Optimizing the use of available imaging time during first‐pass perfusion with a magnetic resonance imaging pulse sequence that adapts image acquisition duration to HR and patient size is feasible. Acquired in‐plane spatial resolution is improved, the DRA is reduced, and while SNR is reduced with the adaptive sequence consistent with the lower voxel size used, image quality is maintained. J. Magn. Reson. Imaging 2015;42:946–953.
Diffuse myocardial fibrosis may be quantified with magnetic resonance (MR) by calculating extracellular volume (ECV) fraction from native and post-contrast T1 values. The ideal modified look-locker ...inversion recovery (MOLLI) sequence for deriving T1 values has not been determined. This study aims to establish if systematic differences exist between suggested MOLLI schemes.
Twelve phantom gels were studied with inversion recovery spin echo MR at 3.0 tesla to determine reference T1. Gels were then scanned with six MOLLI sequences (3s)3b(3s)5b; 4b(3s)3b(3s)2b; 5b(3s)3b with flip angles of both 35° and 50° at a range of heart rates (HRs). In 10 healthy volunteers MOLLI studies were performed on two separate occasions. Mid ventricular native and post contrast T1 was measured and ECV (%) calculated.
In phantoms, the co-efficient of variability at simulated HR 40-100 with a flip angle of 35° ranged from 6.77 to 9.55, and at 50° from 7.71 to 11.10. T1 was under-estimated by all MOLLI acquisitions. Error was greatest with longer T1, and increased as HR increased. The 10 volunteers had normal MR studies. Native T1 time was similar for all acquisitions but highest with the 5b(3s)3b 35° scheme (1,189.1±33.46 ms). Interstudy reproducibility was similar for all MOLLIs.
The 5b(3s)3b MOLLI scheme agreed best with reference T1, without statistical difference between the six schemes. The shorter breath-hold time of 5b(3s)3b scheme may be preferable in clinical studies and warrants further investigation.
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