Hays, Allison G

ABSTRACT Purpose Standard spatial‐spectral excitation pulses apply a fly‐back gradient between sub‐pulses, limiting, for example, how thin the slices can be (> 4 mm). Without fly‐back gradients, slices can be as thin as 1.7 mm but require a phase calibration for the sub‐pulses with inverted gradients due to system imperfections. Here we propose and test a fast (< 1 s), localized pre‐scan enabling thin‐slice frequency‐selective excitation. Methods The calibration pre‐scan determines the correction phase between even and odd sub‐pulses by measuring the phase difference of two FIDs excited with either the last or second‐to‐last RF sub‐pulse of the spatial‐spectral pulse. Non‐localized and localized versions of the calibration pre‐scan are tested and validated for water‐only excitation in phantoms and the human heart. As an example, breath‐held coronary MR angiography is performed with a spiral multi‐slice sequence employing the proposed pulses with a slice thickness of 1.7 mm. Results The proposed calibration pre‐scan takes 11.1 ms per slice, whether it is localized or not. Localized calibration phases are validated with an image‐based calibration map. Slice profiles are visualized for pulses with different time‐bandwidth products. Fat is suppressed to below 20% and 25% of the surrounding water signal in both phantoms and the human heart, respectively. High‐quality coronary angiograms are demonstrated in all test subjects. Conclusion Spatial‐spectral pulses without fly‐back gradients can be calibrated quickly (up to 90 slices in 1 s), enabling thinner slices, higher excitation angles, or pulses with sharper slice profiles using waveforms with higher time‐bandwidth products.

Importance Current risk prediction guidelines for hypertrophic cardiomyopathy predict only sudden cardiac death and are imperfect, leading to avoidable deaths and unnecessary implantable cardioverter defibrillators. Objective To combine prospectively collected clinical history, imaging, genetic, and biomarker data to improve risk prediction of adverse events in hypertrophic cardiomyopathy. Design, Setting, and Participants A total of 2750 patients with hypertrophic cardiomyopathy were prospectively enrolled in the registry-based study from 44 sites in North America and Europe with expertise in hypertrophic cardiomyopathy and cardiac magnetic resonance (CMR) imaging. Participants were enrolled from April 1, 2014, to April 7, 2017. Exposures Patients underwent a health history questionnaire, blood sampling for biomarkers and genotyping, and contrast-enhanced CMR. Patients were followed up yearly by telephone and through records review regarding event documentation. Main Outcomes and Measures The predefined composite adjudicated primary end point was time to first event for hypertrophic cardiomyopathy–related deaths; nonfatal sustained ventricular arrhythmias (VAs) requiring cardioversion or defibrillation; and left ventricular (LV) assist device implant or heart transplant. A secondary end point was a composite of sudden cardiac death and nonfatal VA events. The elastic-net method identified the most important predictors. Cox proportional hazards regression assessed associations with time to the first end point. Results Of the 2750 prospectively enrolled patients, 2698 (98%) had analyzable data after 9 were excluded because they had hypertrophic cardiomyopathy phenocopies and 43 withdrew. Of these remaining patients, 1919 (71%) were male, mean age was 50 years (SD, 11 years), and 423 (16%) were from underrepresented racial and minority groups. The mean follow-up was 6.9 years (SD, 2.1 years). The primary event model in 104 patients included LV scar as a percentage of LV mass by late gadolinium enhancement (LGE%; hazard ratio [HR], 1.86; 95% CI, 1.58-2.20; P &amp;lt; .001), LV mass index (HR, 1.09; 95% CI, 1.01-1.17; P = .03), LV end-systolic volume index (HR, 1.28; 95% CI, 1.12-1.46; P &amp;lt; .001 ), all per 10-unit increase, history of heart failure at study entry (HR, 2.89; 95% CI, 1.75-4.77; P &amp;lt; .001), and log N-terminal pro–B-type natriuretic peptide (NT-proBNP; HR, 1.41; 95% CI, 1.17-1.70; P &amp;lt; .001) level per log unit, (C index for all, 0.77). An LGE percentage of the LV mass of 9% or higher substantially increased the primary composite event rate ( P = .001). The secondary sudden cardiac death and VA risk factor model (in 69 patients) included LGE%, LV mass index, LV ejection fraction, and log(NT-proBNP) (C index, 0.76). Conclusions and Relevance These results provide prospective evidence for incorporating cardiac magnetic resonance and NT-proBNP in the evaluation of patients with hypertrophic cardiomyopathy. Trial Registration ClinicalTrials.gov Identifier: NCT01915615

ABSTRACT Purpose To simultaneously measure skeletal muscle energetics and blood flow (BF) before, during, and after dynamic plantar flexion exercise (PFE). Methods Non‐localized pulse‐acquire phosphorus‐31 magnetic resonance spectroscopy ( 31 P MRS) and phase contrast flow magnetic resonance imaging ( 1 H MRI) using golden‐angle rotated spiral readouts were acquired in an interleaved fashion. Data were collected at rest, during PFE to volitional fatigue, and post‐exercise recovery in 10 healthy adults. Interleaved popliteal artery BF was validated against conventional cine phase‐contrast measures at rest and post‐exercise recovery, while calf muscle energetics were validated by comparing to conventional 31 P MRS‐only measures at rest. To minimize motion artifacts during dynamic PFE, flow data were resolved in 3 dimensions (cardiac phase, pedal position, and exercise stage). Results Resting phosphocreatine (PCr) and inorganic phosphate concentrations were similar between both techniques (both p > 0.05). During PFE, PCr declined to 46% ± 10% of rest. PCr recovery time was 43 ± 15 s. Resting BF was 132 ± 43 mL/min and increased up to four‐fold during PFE depending on exercise stage and pedal position. Notably, there was excellent agreement between the interleaved and conventional BF measures ( r 2 = 0.95, slope = 0.977, p < 0.0001) with minimal bias (12.62 mL/min) over a wide range of physiologically relevant BF values (from ∼60 to 600 mL/min). Conclusion The feasibility of simultaneous assessment of skeletal muscle energetics and BF during dynamic exercise by interleaved 31 P MRS/ 1 H flow MRI was demonstrated along with good agreement between interleaved and conventional techniques during rest and recovery. One can now simultaneously quantify critical BF‐metabolism relationships and use this to probe disease‐related adaptations.