Albert de Roos

Pulmonary flow profile and distensibility following acute pulmonary embolism.

ObjectiveProof of concept study evaluating CMR as screening tool for chronic thromboembolic pulmonary hypertension (CTEPH) in patients treated for acute pulmonary embolism (PE).Materials and methodsRight and left ventricular function of 15 consecutive patients treated for PE and 10 consecutive patients in whom PE was excluded was estimated at baseline by cardiac CT and at 6 months follow-up by CMR. Additionally, during the follow-up visit, pulmonary artery (PA) hemodynamics were studied by CMR and the presence of pulmonary hypertension by echocardiography.ResultsCT measured right ventricular ejection fraction (RVEF) was lower in patients with PE compared to patients without PE at time of diagnosis (median 47%, interquartile range 39-53 vs. 55%, 52-58; p = 0.014). After 6 months follow up, the RVEF between patients treated for PE and patients without PE were not statistically significant different (55%, 52-60 versus 54%, 51-57; p = 0.57), as were distensibility index (0.18 ± 0.18 versus 0.25 ± 0.18, p = 0.20), mean velocity (14.1 ± 3.9 cm/s versus 14.0 ± 2.5 cm/s, p = 0.81), peak velocity (86.5 ± 22 cm/s versus 89.6 ± 13 cm/s, p = 0.43) and time to peak PA blood flow velocity (142 ± 49 ms versus 161 ± 29 ms, p = 0.14). One patient was diagnosed with CTEPH and CMR revealed poor right systolic function, decreased PA distensibility and flow velocity, and a systolic notch in the PA flow profile consistent with persistent PA obstruction.ConclusionIn this small series, right ventricular performance and PA flow profiles of patients treated for 6 months after PE are equivalent to those parameters in normal patients.

In vivo human coronary magnetic resonance angiography at 7 Tesla

Introduction. Cardiac MRI at high fields faces many challenges including the lack of commercially available body RF coils, increased sample-induced B1 inhomogeneity, increased magnetic susceptibility effects which make imaging with balanced sequences difficult, and SAR limitations. However, if these can be at least partially overcome, then the higher signal-to-noise is advantageous both for imaging and localized spectroscopy. Here we investigate the feasibility of acquiring coronary magnetic resonance angiography (CMRA) scans, a promising technique for the non-invasive visualization of the coronary anatomy (1), in volunteers at 7 tesla (T) on a time-scale acceptable for clinical studies.

Characterization and quantification of dynamic left atrioventricular valve regurgitation after atrioventricular septal defect correction with 4D Flow MRI and retrospective valve tracking

Background Regurgitation of the left atrio-ventricular valve (LAVV) is common after atrioventricular septal defect (AVSD) correction and up to 15% of the patients require surgery of the LAVV during follow-up. Reliable quantification of LAVV regurgitation after AVSD correction is essential for indicating surgical correction, but has shown to be difficult using echocardiography. 4DFlow MRI with retrospective valve tracking allows visualization and quantification of trans-valvular blood flow. The aim of cuurent study was to describe dynamic behaviour of regurgitant jets of the LAVV after AVSD correction and to quantify severity of regurgitation using 4DFlow MRI with retrospective valve tracking. Methods

Evaluation of reducing temporal resolution on the accuracy of aortic pulse wave velocity assessment from velocity encoded MRI

Background Aortic pulse wave velocity (PWV), the propagation speed of blood flow velocity waves through the aorta, is a marker of aortic stiffness with prognostic value in various diseases with vascular expression. One-directional throughplane velocity-encoded (VE) MRI, planned perpendicular to the ascending aorta and additionally transecting the proximal descending aorta (Figure 1), is a validated method for assessing PWV over the aortic arch. However, the effect of the temporal resolution (Tres) of VE MRI on the accuracy of PWV assessment has not yet been established. Therefore, the aim of this study was to evaluate the effect of reducing Tres on the accuracy of aortic PWV and how this relates to physiological variation. Methods Five patients referred for cardiac MRI and ten healthy volunteers within similar age range (mean age 32 ± 14 years) were prospectively included. PWV was assessed from velocity mapping using VE MRI on 3T MRI (Ingenia, Philips) with velocity sensitivity of 150 cm/s. Reference PWV (PWVref) was achieved from VE MRI with maximal number of reconstructed phases (Tres = 5 ms). The effect of temporal Tres on PWV was evaluated by temporal downsampling (50% [Tres = 10 ms], 67% [Tres = 15 ms], 75% [Tres = 20 ms], and 80% [Tres = 25 ms]), first by reducing phases during repeated reconstruction of the original acquired high-temporal data. Next, downsampling was performed by data removal as well as by data

The added value of streamline visualization in the evaluation of left atrioventricular valve flow and left ventricular diastolic function with 4DFlow MRI

Background 4DFlow MRI with retrospective valve tracking allows trans-valvular blood flow quantification. Valve tracking usually follows the anatomical annulus but does not take into account the inflow direction through the valve, which might lead to substantial errors when opening of the valve leaflets is restricted after surgery. We aimed to evaluate the added value of streamline visualization in the characterization and quantification of trans-left atrioventricular valve (LAVV) blood flow and assessment of left ventricular (LV) diastolic function in 4DFlow MRI. Methods

Myocardial Perfusion Imaging: The Role of SPECT, PET and CMR

Current cardiology practice is hard to imagine without noninvasive cardiovascular imaging, as myocardial perfusion imaging is an important part of the diagnostic strategy in clinical guidelines. Single-photon emission computed tomography (SPECT), cardiac magnetic resonance (CMR) and positron emission tomography (PET) perfusion imaging are increasingly applied for the detection for the detection of ischemia. Early detection of ischemia is may contribute to lowering the morbidity and mortality in patients with ischemic heart disease. However, SPECT, PET and CMR each have their own merits and technical limitations. Yet, the achievements in the field of myocardial perfusion imaging are considerable and new technical developments are still ongoing.

Leveling of arterial wall stiffness between aortic arch and left carotid artery due to aging is associated with reduced volume flow towards the brain: pulse wave velocity evaluation with high-field velocity-encoded MRI

Background A discrete transition of wall stiffness at the interface of a compliant aorta and stiffer carotid arteries creates a reflection site for the aortic pulse wave and consequently limits excessive pulsatile energy transmission towards the brain. Arterial wall stiffness can be expressed by the pulse wave velocity (PWV) and dualslice one-directional through-plane velocity-encoded (VE) MRI is well-validated for accurate PWV-assessment. The hypothesis is that with aging, leveling of PWV across the aortic arch and carotid artery will occur with negative effect on the flow towards the brain. The purpose of this study was to evaluate PWV and volume flow in aorta and carotid artery in younger and older volunteers using 3T VE MRI.

Coronary magnetic resonance angiography at 7 Tesla: a quantitative comparison with results at 3 Tesla

Methods Eight healthy adult subjects (mean age 23 ± 3 years, 5 men) underwent vector ECG-triggered, navigator gated and corrected free-breathing 3D MRA of the RCA at 7 T and 3 T. At 7 T a quadrature loop-pair (two 15 cm elements) was constructed, and the 2D selective respiratory navigator was localized at the lung-heart interface. At 3 T, a commercial 6-element cardiac receive array was used with body-coil transmit. A 3D segmented k-space gradient echo technique was combined with spectrally selective adiabatic inversion-recovery magnetization fat saturation. At 3 T, coronary MRA were obtained with the navigator localized at the lung-heart interface and at the lung-liver interface, respectively. The scan parameters at both field strengths were as similar as possible (Table 1). The S/N in the bloodpool of the aortic root near the RCA offspring, coronary vessel length, vessel sharpness, acquisition time and navigator efficiency were compared using Wilcoxon matched-pairs test. For visualization, reformatting with the Soapbubble-tool was utilized.

Ascending aortic wall shear stress and distensibility are different in patients with corrected atrioventricular septal defect compared to healthy controls: a comprehensive CMR and 4D flow MRI evaluation

Background In patients with an atrioventricular septal defect (AVSD), the left ventricular outflow tract (LVOT) and the ascending aorta (AAo) are located more anteriorly due to the position of the common AV valve. This may alter proximal aortic flow, and we hypothesize that this can result in impaired LV systolic function and AAo wall degeneration. We aimed to quantify differences in AAo wall shear stress (WSS), distensibility (Dist), aortic arch pulse wave velocity (PWV) and LV ejection fraction (EF) in these patients versus healthy controls using cardiovascular magnetic resonance (CMR) and four dimensional (4D) flow MRI.

The pathway of left ventricular blood flow in healthy subjects and patients with corrected atrio-ventricular septum defect: an observational study using 4DFlow MRI and particle tracing

Background Blood entering the left ventricle (LV) through the left atrio-ventricular valve (LAVV) and exiting through the aorta is assumed to follow the most energy efficient pathway. In patients with a corrected atrio-ventricular septal defect (AVSD), this intra-cardiac blood flow pathway may be altered, due to the restricted opening of the LAVV. This might affect optimal LV function. Particle tracing in 4DFlow MRI data enables quantitative evaluation of the temporal distribution of blood particles in the LV. We aimed to compare the LV intra-cardiac blood flow pathway in corrected AVSD patients with that of healthy subjects, using 4DFlow MRI and particle tracing in the standard 16 segment model of the American Heart Association (AHA).