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Purpose
T\(_{1P}\) dispersion quantification can potentially be used as a cardiac magnetic resonance index for sensitive detection of myocardial fibrosis without the need of contrast agents. However, dispersion quantification is still a major challenge, because T\(_{1P}\) mapping for different spin lock amplitudes is a very time consuming process. This study aims to develop a fast and accurate T\(_{1P}\) mapping sequence, which paves the way to cardiac T1ρ dispersion quantification within the limited measurement time of an in vivo study in small animals.
Methods
A radial spin lock sequence was developed using a Bloch simulation-optimized sampling pattern and a view-sharing method for image reconstruction. For validation, phantom measurements with a conventional sampling pattern and a gold standard sequence were compared to examine T\(_{1P}\) quantification accuracy. The in vivo validation of T\(_{1P}\) mapping was performed in N = 10 mice and in a reproduction study in a single animal, in which ten maps were acquired in direct succession. Finally, the feasibility of myocardial dispersion quantification was tested in one animal.
Results
The Bloch simulation-based sampling shows considerably higher image quality as well as improved T\(_{1P}\) quantification accuracy (+ 56%) and precision (+ 49%) compared to conventional sampling. Compared to the gold standard sequence, a mean deviation of - 0.46 ± 1.84% was observed. The in vivo measurements proved high reproducibility of myocardial T\(_{1P}\) mapping. The mean T\(_{1P}\) in the left ventricle was 39.5 ± 1.2 ms for different animals and the maximum deviation was 2.1% in the successive measurements. The myocardial T\(_{1P}\) dispersion slope, which was measured for the first time in one animal, could be determined to be 4.76 ± 0.23 ms/kHz.
Conclusion
This new and fast T\(_{1P}\) quantification technique enables high-resolution myocardial T\(_{1P}\) mapping and even dispersion quantification within the limited time of an in vivo study and could, therefore, be a reliable tool for improved tissue characterization.
Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures
(2012)
Background: One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating.
Methods: A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip. Results: A maximum temperature rise of 22.4 degrees C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2 degrees C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8 degrees C.
Conclusion: Up to a maximum of 22.4 degrees C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner.
Increased aortic stiffness is known to be associated with atherosclerosis and has a predictive value for cardiovascular events. This study aims to investigate the local distribution of early arterial stiffening due to initial atherosclerotic lesions. Therefore, global and local pulse wave velocity (PWV) were measured in ApoE\(^{-/-}\) and wild type (WT) mice using ultrahigh field MRI. For quantification of global aortic stiffness, a new multi-point transit-time (TT) method was implemented and validated to determine the global PWV in the murine aorta. Local aortic stiffness was measured by assessing the local PWV in the upper abdominal aorta, using the flow/area (QA) method. Significant differences between age matched ApoE\(^{-/-}\) and WT mice were determined for global and local PWV measurements (global PWV: ApoE\(^{-/-}\): 2.7 ±0.2m/s vs WT: 2.1±0.2m/s, P<0.03; local PWV: ApoE\(^{-/-}\): 2.9±0.2m/s vs WT: 2.2±0.2m/s, P<0.03). Within the WT mouse group, the global PWV correlated well with the local PWV in the upper abdominal aorta (R\(^2\) = 0.75, P<0.01), implying a widely uniform arterial elasticity.
In ApoE\(^{-/-}\) animals, however, no significant correlation between individual local and global PWV was present (R\(^2\) = 0.07, P = 0.53), implying a heterogeneous distribution of vascular stiffening in early atherosclerosis. The assessment of global PWV using the new multi-point TT measurement technique was validated against a pressure wire measurement in a vessel
phantom and showed excellent agreement. The experimental results demonstrate that vascular stiffening caused by early atherosclerosis is unequally distributed over the length of large vessels. This finding implies that assessing heterogeneity of arterial stiffness by multiple local measurements of PWV might be more sensitive than global PWV to identify early atherosclerotic lesions.
Background
Surgical procedures in small animal models of heart disease might evoke alterations in cardiac morphology and function. The aim of this study was to reveal and quantify such potential artificial early or long term effects in vivo, which might account for a significant bias in basic cardiovascular research, and, therefore, could potentially question the meaning of respective studies.
Methods
Female Wistar rats (n = 6 per group) were matched for weight and assorted for sham left coronary artery ligation or control. Cardiac morphology and function was then investigated in vivo by cine magnetic resonance imaging at 7 Tesla 1 and 8 weeks after the surgical procedure. The time course of metabolic and inflammatory blood parameters was determined in addition.
Results
Compared to healthy controls, rats after sham surgery showed a lower body weight both 1 week (267.5±10.6 vs. 317.0±11.3 g, n<0.05) and 8 weeks (317.0±21.1 vs. 358.7±22.4 g, n<0.05) after the intervention. Left and right ventricular morphology and function were not different in absolute measures in both groups 1 week after surgery. However, there was a confined difference in several cardiac parameters normalized to the body weight (bw), such as myocardial mass (2.19±0.30/0.83±0.13 vs. 1.85±0.22/0.70±0.07 mg left/right per g bw, p<0.05), or enddiastolic ventricular volume (1.31±0.36/1.21±0.31 vs. 1.14±0.20/1.07±0.17 µl left/right per g bw, p<0.05). Vice versa, after 8 weeks, cardiac masses, volumes, and output showed a trend for lower values in sham operated rats compared to controls in absolute measures (782.2±57.2/260.2±33.2 vs. 805.9±84.8/310.4±48.5 mg, p<0.05 for left/right ventricular mass), but not normalized to body weight. Matching these findings, blood testing revealed only minor inflammatory but prolonged metabolic changes after surgery not related to cardiac disease.
Conclusion
Cardio-thoracic surgical procedures in experimental myocardial infarction cause distinct alterations upon the global integrity of the organism, which in the long term also induce circumscribed repercussions on cardiac morphology and function. This impact has to be considered when analyzing data from respective animal studies and transferring these findings to conditions in patients.
Background
Fast and accurate T1ρ mapping in myocardium is still a major challenge, particularly in small animal models. The complex sequence design owing to electrocardiogram and respiratory gating leads to quantification errors in in vivo experiments, due to variations of the T\(_{1p}\) relaxation pathway. In this study, we present an improved quantification method for T\(_{1p}\) using a newly derived formalism of a T\(_{1p}\)\(^{*}\) relaxation pathway.
Methods
The new signal equation was derived by solving a recursion problem for spin-lock prepared fast gradient echo readouts. Based on Bloch simulations, we compared quantification errors using the common monoexponential model and our corrected model. The method was validated in phantom experiments and tested in vivo for myocardial T\(_{1p}\) mapping in mice. Here, the impact of the breath dependent spin recovery time T\(_{rec}\) on the quantification results was examined in detail.
Results
Simulations indicate that a correction is necessary, since systematically underestimated values are measured under in vivo conditions. In the phantom study, the mean quantification error could be reduced from − 7.4% to − 0.97%. In vivo, a correlation of uncorrected T\(_{1p}\) with the respiratory cycle was observed. Using the newly derived correction method, this correlation was significantly reduced from r = 0.708 (p < 0.001) to r = 0.204 and the standard deviation of left ventricular T\(_{1p}\) values in different animals was reduced by at least 39%.
Conclusion
The suggested quantification formalism enables fast and precise myocardial T\(_{1p}\) quantification for small animals during free breathing and can improve the comparability of study results. Our new technique offers a reasonable tool for assessing myocardial diseases, since pathologies that cause a change in heart or breathing rates do not lead to systematic misinterpretations. Besides, the derived signal equation can be used for sequence optimization or for subsequent correction of prior study results.
Aims
This study aimed to identify echocardiographic determinants of left ventricular thrombus (LVT) formation after acute anterior myocardial infarction (MI).
Methods and results
This case–control study comprised 55 acute anterior MI patients with LVT as cases and 55 acute anterior MI patients without LVT as controls, who were selected from a cohort of consecutive patients with ischemic heart failure in our hospital. The cases and controls were matched for age, sex, and left ventricular ejection fraction. LVT was detected by routine/contrast echocardiography or cardiac magnetic resonance imaging during the first 3 months following MI. Formation of apical aneurysm after MI was independently associated with LVT formation [72.0% vs. 43.5%, odds ratio (OR) = 5.06, 95% confidence interval (CI) 1.65–15.48, P = 0.005]. Echocardiographic risk factors associated with LVT formation included reduced mitral annular plane systolic excursion (<7 mm, OR = 4.69, 95% CI 1.84–11.95, P = 0.001), moderate–severe diastolic dysfunction (OR = 2.71, 95% CI 1.11–6.57, P = 0.028), and right ventricular (RV) dysfunction [reduced tricuspid annular plane systolic excursion < 17 mm (OR = 5.48, 95% CI 2.12–14.13, P < 0.001), reduced RV fractional area change < 0.35 (OR = 3.32, 95% CI 1.20–9.18, P = 0.021), and enlarged RV mid diameter (per 5 mm increase OR = 1.62, 95% CI 1.12–2.34, P = 0.010)]. Reduced tricuspid annular plane systolic excursion (<17 mm) significantly associated with increased risk of LVT in anterior MI patients (OR = 3.84, 95% CI 1.37–10.75, P = 0.010), especially in those patients without apical aneurysm (OR = 5.12, 95% CI 1.45–18.08, P = 0.011), independent of body mass index, hypertension, anaemia, mitral annular plane systolic excursion, and moderate–severe diastolic dysfunction.
Conclusions
Right ventricular dysfunction as determined by reduced TAPSE or RV fractional area change is independently associated with LVT formation in acute anterior MI patients, especially in the setting of MI patients without the formation of an apical aneurysm. This study suggests that besides assessment of left ventricular abnormalities, assessment of concomitant RV dysfunction is of importance on risk stratification of LVT formation in patients with acute anterior MI.
Religion and social support along with trait emotional intelligence (EI) help individuals to reduce stress caused by difficult situations. Their implications may vary across cultures in reference to predicting health-related quality of life (HRQoL). A convenience sample of N = 200 chronic heart failure (CHF) patients was recruited at cardiology centers in Germany (n = 100) and Pakistan (n = 100). Results indicated that trait-EI predicted better mental component of HRQoL in Pakistani and German CHF patients. Friends as social support appeared relevant for German patients only. Qualitative data indicate an internal locus of control in German as compared to Pakistani patients. Strengthening the beneficial role of social support in Pakistani patients is one example of how the current findings may inspire culture-specific treatment to empower patients dealing with the detrimental effects of CHF.
Aims
From the various mechanical cardiac assist devices and indications available, the use of the percutaneous intraventricular Impella CP pump is usually restricted to acute ischaemic shock or prophylactic indications in high‐risk interventions. In the present study, we investigated clinical usefulness of the Impella CP device in patients with non‐ischaemic cardiogenic shock as compared with acute ischaemia.
Methods and results
In this retrospective single‐centre analysis, patients who received an Impella CP at the University Hospital Würzburg between 2013 and 2017 due to non‐ischaemic cardiogenic shock were age‐matched 2:1 with patients receiving the device due to ischaemic cardiogenic shock. Inclusion criteria were therapy refractory haemodynamic instability with severe left ventricular systolic dysfunction and serum lactate >2.0 mmol/L at implantation. Basic clinical data, indications for mechanical ventricular support, and outcome were obtained in all patients with non‐ischaemic as well as ischaemic shock and compared between both groups. Continuous variables are expressed as mean ± standard deviation or median (quartiles). Categorical variables are presented as count and per cent. Twenty‐five patients had cardiogenic shock due to non‐ischaemic reasons and were compared with 50 patients with cardiogenic shock due to acute myocardial infarction. Resuscitation rates before implantation of Impella CP were high (32 vs. 42%; P = 0.402). At implantation, patients with non‐ischaemic cardiogenic shock had lower levels of high‐sensitive troponin T (110.65 [57.87–322.1] vs. 1610 [450.8–3861.5] pg/mL; P = 0.001) and lactate dehydrogenase (377 [279–608] vs. 616 [371.3–1109] U/L; P = 0.007), while age (59 ± 16 vs. 61.7 ± 11; P = 0.401), glomerular filtration rate (43.5 [33.2–59.7] vs. 48 [35.75–69] mL/min; P = 0.290), C‐reactive protein (5.17 [3.27–10.26] vs. 10.97 [3.23–17.2] mg/dL; P = 0.195), catecholamine index (30.6 [10.6–116.9] vs. 47.6 [11.7–90] μg/kg/min; P = 0.663), and serum lactate (2.6 [2.2–5.8] vs. 2.9 [1.3–6.6] mmol/L; P = 0.424) were comparable between both groups. There was a trend for longer duration of Impella support in the non‐ischaemic groups (5 [2–7.5] vs. 3 [2–5.25] days, P = 0.211). Rates of haemodialysis (52 vs. 47%; P = 0.680) and transition to extracorporeal membrane oxygenation (13.6 vs. 22.2%; P = 0.521) were comparable. No significant difference was found regarding both 30 day survival (48 vs. 30%; P = 0.126) and in‐hospital mortality (66.7 vs. 74%; P = 0.512), although there was a trend for better survival in the non‐ischaemic group.
Conclusions
These data suggest that temporary use of the Impella CP device might be a useful therapeutic option for bridge to recovery not only in ischaemic but also in non‐ischaemic cardiogenic shock.
Background
T1 mapping sequences such as MOLLI, ShMOLLI and SASHA make use of different technical approaches, bearing strengths and weaknesses. It is well known that obtained T1 relaxation times differ between the sequence techniques as well as between different hardware. Yet, T1 quantification is a promising tool for myocardial tissue characterization, disregarding the absence of established reference values. The purpose of this study was to evaluate the feasibility of native and post-contrast T1 mapping methods as well as ECV maps and its diagnostic benefits in a clinical environment when scanning patients with various cardiac diseases at 3 T.
Methods
Native and post-contrast T1 mapping data acquired on a 3 T full-body scanner using the three pulse sequences 5(3)3 MOLLI, ShMOLLI and SASHA in 19 patients with clinical indication for contrast enhanced MRI were compared. We analyzed global and segmental T1 relaxation times as well as respective extracellular volumes and compared the emerged differences between the used pulse sequences.
Results
T1 times acquired with MOLLI and ShMOLLI exhibited systematic T1 deviation compared to SASHA. Myocardial MOLLI T1 times were 19% lower and ShMOLLI T1 times 25% lower compared to SASHA. Native blood T1 times from MOLLI were 13% lower than SASHA, while post-contrast MOLLI T1-times were only 5% lower. ECV values exhibited comparably biased estimation with MOLLI and ShMOLLI compared to SASHA in good agreement with results reported in literature. Pathology-suspect segments were clearly differentiated from remote myocardium with all three sequences.
Conclusion
Myocardial T1 mapping yields systematically biased pre- and post-contrast T1 times depending on the applied pulse sequence. Additionally calculating ECV attenuates this bias, making MOLLI, ShMOLLI and SASHA better comparable. Therefore, myocardial T1 mapping is a powerful clinical tool for classification of soft tissue abnormalities in spite of the absence of established reference values.
Background
Aortic valve stenosis is a common finding diagnosed with high sensitivity in transthoracic echocardiography, but the examiner often finds himself confronted with uncertain results in patients with moderate pressure gradients and concomitant systolic heart failure. While patients with true-severe low-gradient aortic valve stenosis with either reduced or preserved left ventricular systolic function are primarily candidates for valve replacement, there is a relevant proportion of patients with pseudo-severe aortic valve stenosis anticipated not to benefit but actually rather deteriorate by interventional therapy or surgery.
Case presentation
In this article we present a case report of a male patient with pseudo-severe aortic valve stenosis due to cardiac amyloidosis highlighting the diagnostic schedule. The patient underwent stress echocardiography because of discrepant findings in transthoracic echocardiography and cardiac catheterization regarding the severity of aortic valve stenosis. After evaluation of the results, it became clear that he had a need for optimum heart failure medication and implantation of a cardiac resynchronization therapy defibrillator.
Conclusion
Due to the pitfalls in conventional as well as invasive diagnostics at rest, Stress echocardiography should be considered part of the standard optimum diagnostic spectrum in all unclear or borderline cases in order to confirm the correct diagnosis and constitute optimal therapy.