Fat-suppressed breath-hold magnetic resonance coronary angiography

Fat-free noncontrast whole-heart cardiovascular magnetic resonance imaging with fast and power-optimized off-resonant water-excitation pulses

BACKGROUND

Cardiovascular magnetic resonance imaging (CMR) faces challenges due to the interference of bright fat signals in visualizing structures, such as coronary arteries. Effective fat suppression is crucial, especially when using whole-heart CMR techniques. Conventional methods often fall short due to rapid fat signal recovery, leading to residual fat content hindering visualization. Water-selective off-resonant radiofrequency (RF) pulses have been proposed but come with tradeoffs between pulse duration, which increases scan time, and increased RF energy deposit, which limits their applicability due to specific absorption rate (SAR) constraints. The study introduces a lipid-insensitive binomial off-resonant (LIBOR) RF pulse, which addresses concerns about SAR and scan time, and aims to provide a comprehensive quantitative comparison with published off-resonant RF pulses for CMR at 3T.

METHODS

A short (1 ms) LIBOR pulse, with reduced RF power requirements, was developed and implemented in a free-breathing respiratory-self-navigated three-dimensional radial whole-heart CMR sequence at 3T. A binomial off-resonant rectangular (BORR) pulse with matched duration, as well as previously published lipid-insensitive binomial off-resonant excitation (LIBRE) pulses (1 and 2.2 ms), were implemented and optimized for fat suppression in numerical simulations and validated in volunteers (n = 3). Whole-heart CMR was performed in volunteers (n = 10) with all four pulses. The signal-to-noise ratio (SNR) of ventricular blood, skeletal muscle, myocardium, and subcutaneous fat and the coronary vessel detection rates and sharpness were compared.

RESULTS

Experimental results validated numerical findings and near-homogeneous fat suppression was achieved with all four pulses. Comparing the short RF pulses (1 ms), LIBOR reduced the RF power nearly two-fold compared with LIBRE, and three-fold compared with BORR, and LIBOR significantly decreased overall fat SNR from cardiac scans, compared to LIBRE and BORR. The reduction in RF pulse duration (from 2.2 to 1 ms) shortened the whole-heart acquisition from 8.5 to 7 min. No significant differences in coronary arteries detection and sharpness were found when comparing all four pulses.

CONCLUSION

LIBOR pulses enabled whole-heart CMR under 7 min at 3T, with large volume fat signal suppression, while reducing RF power compared with LIBRE and BORR pulses. LIBOR is an excellent candidate to address SAR problems encountered in CMR sequences where fat suppression remains challenging and short RF pulses are required.

A robust broadband fat-suppressing phaser T2 -preparation module for cardiac magnetic resonance imaging at 3T

PURPOSE

Designing a new T₂ -preparation (T₂ -Prep) module to simultaneously provide robust fat suppression and efficient T₂ preparation without requiring an additional fat-suppression module for T₂ -weighted imaging at 3T.

METHODS

The tip-down radiofrequency (RF) pulse of an adiabatic T₂ -Prep module was replaced by a custom-designed RF-excitation pulse that induces a phase difference between water and fat, resulting in a simultaneous T₂ preparation of water signals and the suppression of fat signals at the end of the module (a phaser adiabatic T₂ -Prep). Numerical simulations and in vitro and in vivo electrocardiogram (ECG)-triggered navigator-gated acquisitions of the human heart were performed. Blood, myocardium, and fat signal-to-noise ratios and right coronary artery vessel sharpness were compared against previously published adiabatic T₂ -Prep approaches.

RESULTS

Numerical simulations predicted an increased fat-suppression bandwidth and decreased sensitivity to transmit magnetic field inhomogeneities using the proposed approach while preserving the water T₂ -Prep capabilities. This was confirmed by the tissue signals acquired in the phantom and the in vivo images, which show similar blood and myocardium signal-to-noise ratio, contrast-to-noise ratio, and significantly reduced fat signal-to-noise ratio compared with the other methods. As a result, the right coronary artery conspicuity was significantly increased.

CONCLUSION

A novel fat-suppressing T₂ -Prep method was developed and implemented that showed robust fat suppression and increased vessel sharpness compared with conventional techniques while preserving its T₂ -Prep capabilities.

Myocardial T1 and T2 quantification and water-fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

PURPOSE

This work aims to develop an approach for simultaneous water-fat separation and myocardial T₁ and T₂ quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

METHODS

Two 15-heartbeat cMRF sequences with different rosette trajectories designed for water-fat separation at 3T and 1.5T were implemented. Water T₁ and T₂ maps, water image, and fat image were generated with B₀ inhomogeneity correction using a B₀ map derived from the cMRF data themselves. The proposed water-fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.

RESULTS

Water T₁ and T₂ values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T₁ but 2~3 ms higher T₂ values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

CONCLUSION

Rosette cMRF provides fat images along with myocardial T₁ and T₂ maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.

Noncontrast free-breathing respiratory self-navigated coronary artery cardiovascular magnetic resonance angiography at 3 T using lipid insensitive binomial off-resonant excitation (LIBRE)

BACKGROUND

Robust and homogeneous lipid suppression is mandatory for coronary artery cardiovascular magnetic resonance (CMR) imaging since the coronary arteries are commonly embedded in epicardial fat. However, effective large volume lipid suppression becomes more challenging when performing radial whole-heart coronary artery CMR for respiratory self-navigation and the problem may even be exacerbated at increasing magnetic field strengths. Incomplete fat suppression not only hinders a correct visualization of the coronary vessels and generates image artifacts, but may also affect advanced motion correction methods. The aim of this study was to evaluate a recently reported lipid insensitive CMR method when applied to a noncontrast self-navigated coronary artery CMR acquisitions at 3 T, and to compare it to more conventional fat suppression techniques.

METHODS

Lipid insensitive binomial off resonant excitation (LIBRE) radiofrequency excitation pulses were included into a self-navigated 3D radial GRE coronary artery CMR sequence at 3 T. LIBRE was compared against a conventional CHESS fat saturation (FS) and a binomial 1-180°-1 water excitation (WE) pulse. First, fat suppression of all techniques was numerically characterized using Matlab and experimentally validated in phantoms and in legs of human volunteers. Subsequently, free-breathing self-navigated coronary artery CMR was performed using the LIBRE pulse as well as FS and WE in ten healthy subjects. Myocardial, arterial and chest fat signal-to-noise ratios (SNR), as well as coronary vessel conspicuity were quantitatively compared among those scans.

RESULTS

The results obtained in the simulations were confirmed by the experimental validations as LIBRE enabled near complete fat suppression for 3D radial imaging in vitro and in vivo. For self-navigated whole-heart coronary artery CMR at 3 T, fat SNR was significantly attenuated using LIBRE compared with conventional FS. LIBRE increased the right coronary artery (RCA) vessel sharpness significantly (37 ± 9% (LIBRE) vs. 29 ± 8% (FS) and 30 ± 8% (WE), both p < 0.05) and led to a significant increase in the measured RCA vessel length to (83 ± 31 mm (LIBRE) vs. 56 ± 12 mm (FS) and 59 ± 27 (WE) p < 0.05).

CONCLUSIONS

Applied to a respiratory self-navigated noncontrast 3D radial whole-heart sequence, LIBRE enables robust large volume fat suppression and significantly improves coronary artery image quality at 3 T compared to the use of conventional FS and WE.

Heart Failure and Stroke

PURPOSE

Ischemic stroke significantly contributes to morbidity and mortality in heart failure (HF). The risk of stroke increases significantly, with coexisting atrial fibrillation (AF). An aggravating factor could be asymptomatic paroxysms of AF (so-called silent AF), and therefore, the risk stratification in these patients remains difficult. This review provides an overview of stroke risk in HF, its risk stratification, and stroke prevention in these patients.

RECENT FINDINGS

Stroke risk stratification in HF patients remains an important issue. Recently, the CHA₂DS₂-VASc score, originally developed to predict stroke risk in AF patients, had been reported to be a predictive for strokes in HF patients regardless of AF being present. Furthermore, there are several independent risk factors (e.g., hypertension, diabetes mellitus, prior stroke) described. Based on the current evidence, HF should be considered as an independent risk factor for stroke. The CHA₂DS₂-VASc score might be useful to predict stroke risk in HF patients with or without AF in clinical routine. However, there is only a recommendation for the oral anticoagulation use in patients with concomitant HF and AF, while in patients with HF and no AF, individualized risk stratification is preferred. Current guidelines recommend to prefer non-vitamin Kantagonist anticoagulants over warfarin.

Automated Curved and Multiplanar Reformation for Screening of the Proximal Coronary Arteries in MR Angiography

Congenital anomalies of the coronary ostia can lead to sudden death. A screening solution would be useful to prevent adverse outcomes for the affected individuals. To be considered for integration into clinical routine, such a procedure must meet strict constraints in terms of invasiveness, time and user interaction. Imaging must be fast and seamlessly integrable into the clinical process. Non-contrast enhanced coronary magnetic resonance angiography (MRA) is well suited for this. Furthermore, planar reformations proved effective to reduce the acquired volumetric datasets to 2D images. These usually require time consuming user interaction, though. To fulfill the aforementioned challenges, we present a fully automated solution for imaging and reformatting of the proximal coronary arteries which enables rapid screening of these. The proposed pipeline consists of: (I) highly accelerated single breath-hold MRA data acquisition, (II) coronary ostia detection and vessel centerline extraction, and (III) curved planar reformation of the proximal coronary arteries, as well as multiplanar reformation of the coronary ostia. The procedure proved robust and effective in ten volunteer data sets. Imaging of the proximal coronary arteries took 24 ± 5 s and was successful within one breath-hold for all patients. The extracted centerlines achieve an overlap of 0.76 ± 0.18 compared to the reference standard and the average distance of the centerline points from the spherical surface for reformation was 1.1 ± 0.51 mm. The promising results encourage further experiments on patient data, particularly in coronary ostia anomaly screening.

Left ventricular wall motion abnormalities are associated with stroke recurrence

Objective:

To investigate the role of left ventricular wall motion abnormalities (LVWMA), unrelated to high-risk cardioembolic conditions, in stroke recurrence.

Methods:

This study included consecutive acute ischemic stroke patients. Transthoracic echocardiography was performed as a routine evaluation for stroke patients. The outcomes were the time to recurrent any stroke and ischemic stroke.

Results:

Among 4,316 acute ischemic stroke patients, 430 had LVWMA without high-risk cardioembolic sources. The median observation periods of patients at risk of any stroke and ischemic stroke were 24.5 and 24.7 months. During the follow-up, any stroke and ischemic stroke recurrence were observed in 310 (7.2%) and 250 (5.8%) patients. LVWMA were associated with outcomes after adjustment for traditional cardiovascular risk factors, laboratory and imaging variables, and therapeutic interventions (hazard ratio [HR] 1.707, 95% confidence interval [CI] 1.262–2.310 for any stroke; HR 1.709, 95% CI 1.222–2.390 for ischemic stroke). Moreover, LVWMA could still be considered as independent risk factors after correction for covariates that were significantly associated with outcomes in univariable regression (HR 1.747, 95% CI 1.292–2.364 for any stroke; HR 1.704, 95% CI 1.219–2.382 for ischemic stroke). There were no significant interactions between LVWMA and outcomes between the subgroups except for the statin treatment subgroup.

Conclusions:

This study suggests that LVWMA, even when unassociated with high-risk cardioembolic sources, could be an independent predictor for stroke recurrence in patients with ischemic stroke.

Pharmacologic Management of Chronic Heart Failure: A Review

Standard drug therapy of systolic heart failure has been evaluated in large-scale randomized clinical trials and includes angiotensin-converting enzyme (ACE) inhibi tors, which should be used as first-line therapy, diuret ics for the management of extracellular fluid volume excess, and digoxin. In combination with ACE inhibitors and diuretics, with or without digoxin, some β-adrener gic receptor blockers attenuate disease progression and improve outcome in mild-to-moderate systolic heart failure. The pharmacologic management of chronic dia stolic heart failure is largely empirical and directed at reducing symptoms. Symptoms caused by increased ventricular filling pressures may be diminished by diuret ics and nitrovasodilators. Some calcium channel antago nists and most β-blockers prolong diastolic filling time by slowing heart rate, thereby improving the symptoms of diastolic heart failure.

Noninvasive imaging modalities to visualize atherosclerotic plaques

Atherosclerotic cardiovascular disease is becoming a major cause of death in the world due to global epidemic of diabetes and obesity. For the prevention of atherosclerotic cardiovascular disease, it is necessary to detect high-risk atherosclerotic plaques prior to events. Recent technological advances enable to visualize atherosclerotic plaques noninvasively. This ability of noninvasive imaging helps to refine cardiovascular risk assessment in various individuals, select optimal therapeutic strategy and evaluate the efficacy of medical therapies. In this review, we discuss the role of the currently available imaging modalities including computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography. Advantages and disadvantages of each noninvasive imaging modality will be also summarized.

Golden angle dual-inversion recovery acquisition coupled with a flexible time-resolved sparse reconstruction facilitates sequence timing in high-resolution coronary vessel wall MRI at 3 T

PURPOSE

The need for performing dual-inversion recovery (DIR) coronary vessel wall MRI in correspondence to minimal cardiac motion and optimal blood signal nulling is a major challenge. We propose to address this hurdle by combining DIR with a prolonged acquisition window in conjunction with a golden angle radial trajectory and k-t sparse sensitivity encoding (SENSE) reconstruction to enable a flexible a-posteriori selection of optimized imaging parameters.

METHODS

Coronary vessel wall data acquisition was performed with DIR golden angle radial imaging in n=15 healthy subjects. Images reconstructed using k-t sparse SENSE and different reconstruction window settings were quantitatively (vessel wall conspicuity, thickness, acquisition, and reconstruction window settings) compared with those obtained with more conventional radial DIR imaging.

RESULTS

A flexible retrospective selection of the reconstruction window width and position improved vessel wall conspicuity with respect to baseline acquisitions (P < 0.01). Vessel wall thickness remained unchanged (P = nonsignificant (NS)). Temporal window widths were similar for both approaches (P = NS), yet their position within the cardiac cycle differed significantly (P < 0.02).

CONCLUSIONS

A flexible DIR coronary vessel wall MRI technique that alleviates constraints associated with sophisticated sequence timing was proposed. When compared with a more conventional approach, the technique significantly improved image quality. Magn Reson Med 77:961-969, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Coronary vasomotor responses to isometric handgrip exercise are primarily mediated by nitric oxide: a noninvasive MRI test of coronary endothelial function

Endothelial cell release of nitric oxide (NO) is a defining characteristic of nondiseased arteries, and abnormal endothelial NO release is both a marker of early atherosclerosis and a predictor of its progression and future events. Healthy coronaries respond to endothelial-dependent stressors with vasodilatation and increased coronary blood flow (CBF), but those with endothelial dysfunction respond with paradoxical vasoconstriction and reduced CBF. Recently, coronary MRI and isometric handgrip exercise (IHE) were reported to noninvasively quantify coronary endothelial function (CEF). However, it is not known whether the coronary response to IHE is actually mediated by NO and/or whether it is reproducible over weeks. To determine the contribution of NO, we studied the coronary response to IHE before and during infusion of N(G)-monomethyl-l-arginine (l-NMMA, 0.3 mg·kg(-1)·min(-1)), a NO-synthase inhibitor, in healthy volunteers. For reproducibility, we performed two MRI-IHE studies ~8 wk apart in healthy subjects and patients with coronary artery disease (CAD). Changes from rest to IHE in coronary cross-sectional area (%CSA) and diastolic CBF (%CBF) were quantified. l-NMMA completely blocked normal coronary vasodilation during IHE [%CSA, 12.9 ± 2.5 (mean ± SE, placebo) vs. -0.3 ± 1.6% (l-NMMA); P < 0.001] and significantly blunted the increase in flow [%CBF, 47.7 ± 6.4 (placebo) vs. 10.6 ± 4.6% (l-NMMA); P < 0.001]. MRI-IHE measures obtained weeks apart strongly correlated for CSA (P < 0.0001) and CBF (P < 0.01). In conclusion, the normal human coronary vasoactive response to IHE is primarily mediated by NO. This noninvasive, reproducible MRI-IHE exam of NO-mediated CEF promises to be useful for studying CAD pathogenesis in low-risk populations and for evaluating translational strategies designed to alter CAD in patients.

Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries

Cardiovascular magnetic resonance (CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA (CMRA) at the moment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneurysms (class I indication) and coronary bypass grafts (class II indication). CMRA utilisation for coronary artery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is located far away from the coil elements, is frequently imaged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type I diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New techniques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMR is the potential of an integrated protocol offering assessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of patients with heart disease.

Self-gated free-breathing 3D coronary CINE imaging with simultaneous water and fat visualization

The aim of this study was to develop a novel technique for acquiring 3-dimensional (3D) coronary CINE magnetic resonance images with both water and fat visualization during free breathing and without external respiratory or cardiac gating. The implemented multi-echo hybrid 3D radial balanced Steady-State Free Precession (SSFP) sequence has an efficient data acquisition and is robust against motion. The k-space center along the slice encoding direction was repeatedly acquired to derive both respiratory and cardiac self-gating signals without an increase in scan time, enabling a free-breathing acquisition. The multi-echo acquisition allowed image reconstruction with water-fat separation, providing improved visualization of the coronary artery lumen. Ten healthy subjects were imaged successfully at 1.5 T, achieving a spatial resolution of 1.0 × 1.0 × 3.0 mm(3) and scan time of about 5 minutes. The proposed imaging technique provided coronary vessel depiction comparable to that obtained with conventional breath-hold imaging and navigator gated free-breathing imaging.

High-resolution 3D whole-heart coronary MRA: a study on the combination of data acquisition in multiple breath-holds and 1D residual respiratory motion compensation

OBJECT

To study a scan protocol for coronary magnetic resonance angiography based on multiple breath-holds featuring 1D motion compensation and to compare the resulting image quality to a navigator-gated free-breathing acquisition. Image reconstruction was performed using L1 regularized iterative SENSE.

MATERIALS AND METHODS

The effects of respiratory motion on the Cartesian sampling scheme were minimized by performing data acquisition in multiple breath-holds. During the scan, repetitive readouts through a k-space center were used to detect and correct the respiratory displacement of the heart by exploiting the self-navigation principle in image reconstruction. In vivo experiments were performed in nine healthy volunteers and the resulting image quality was compared to a navigator-gated reference in terms of vessel length and sharpness.

RESULTS

Acquisition in breath-hold is an effective method to reduce the scan time by more than 30% compared to the navigator-gated reference. Although an equivalent mean image quality with respect to the reference was achieved with the proposed method, the 1D motion compensation did not work equally well in all cases.

CONCLUSION

In general, the image quality scaled with the robustness of the motion compensation. Nevertheless, the featured setup provides a positive basis for future extension with more advanced motion compensation methods.

Antithrombotics in Heart Failure With Reduced Ejection Fraction and Normal Sinus Rhythm

Objective: To review the thromboembolic risk, pathophysiology associated with the risk, and literature investigating the use of antithrombotics in patients with heart failure with reduced ejection fraction and normal sinus rhythm (HFrEF-NSR). Data Sources: An English language literature search was performed with MEDLINE/PubMed and Embase from January 1950 to October 2013 using the search terms heart failure, HFrEF, systolic heart failure, cardiomyopathy, left ventricular dysfunction, sinus rhythm, thromboembolism, deep vein thrombosis, pulmonary embolism, myocardial infarction, acute coronary syndrome, acute coronary events, coronary artery disease, stroke, and cerebrovascular events to identify relevant articles. References in the retrieved articles were also assessed to identify other important articles. Study Selection and Data Abstraction: All pertinent original studies, reviews, consensus documents, and guidelines were evaluated for inclusion. Data Synthesis: Patients with HFrEF-NSR may be predisposed to developing thromboembolic events. Studies that have examined the role of antithrombotics (warfarin and/or antiplatelet therapy) for reducing thromboembolic risk have been inconclusive. The WASH and HELAS pilot trials—the only studies with a no-antithrombotics or placebo comparator group—did not find a benefit with antithrombotic therapy but found an increased risk of bleeding with warfarin and of hospitalizations with aspirin. Although the clinical outcome studies (WATCH and WARCEF) suggested that warfarin may reduce stroke risk compared with antiplatelet therapy, the lack of a placebo group and lower-than-projected enrollment prevents definitive conclusions from being made. Conclusions: Current evidence does not support the routine use of antithrombotics for preventing thromboembolic events in patients with HFrEF-NSR without compelling indications.

Non-invasive detection of coronary endothelial response to sequential handgrip exercise in coronary artery disease patients and healthy adults

OBJECTIVES

Our objective is to test the hypothesis that coronary endothelial function (CorEndoFx) does not change with repeated isometric handgrip (IHG) stress in CAD patients or healthy subjects.

BACKGROUND

Coronary responses to endothelial-dependent stressors are important measures of vascular risk that can change in response to environmental stimuli or pharmacologic interventions. The evaluation of the effect of an acute intervention on endothelial response is only valid if the measurement does not change significantly in the short term under normal conditions. Using 3.0 Tesla (T) MRI, we non-invasively compared two coronary artery endothelial function measurements separated by a ten minute interval in healthy subjects and patients with coronary artery disease (CAD).

METHODS

Twenty healthy adult subjects and 12 CAD patients were studied on a commercial 3.0 T whole-body MR imaging system. Coronary cross-sectional area (CSA), peak diastolic coronary flow velocity (PDFV) and blood-flow were quantified before and during continuous IHG stress, an endothelial-dependent stressor. The IHG exercise with imaging was repeated after a 10 minute recovery period.

RESULTS

In healthy adults, coronary artery CSA changes and blood-flow increases did not differ between the first and second stresses (mean % change ±SEM, first vs. second stress CSA: 14.8%±3.3% vs. 17.8%±3.6%, p = 0.24; PDFV: 27.5%±4.9% vs. 24.2%±4.5%, p = 0.54; blood-flow: 44.3%±8.3 vs. 44.8%±8.1, p = 0.84). The coronary vasoreactive responses in the CAD patients also did not differ between the first and second stresses (mean % change ±SEM, first stress vs. second stress: CSA: -6.4%±2.0% vs. -5.0%±2.4%, p = 0.22; PDFV: -4.0%±4.6% vs. -4.2%±5.3%, p = 0.83; blood-flow: -9.7%±5.1% vs. -8.7%±6.3%, p = 0.38).

CONCLUSION

MRI measures of CorEndoFx are unchanged during repeated isometric handgrip exercise tests in CAD patients and healthy adults. These findings demonstrate the repeatability of noninvasive 3T MRI assessment of CorEndoFx and support its use in future studies designed to determine the effects of acute interventions on coronary vasoreactivity.

Clinically significant thrombosis in pediatric heart transplant recipients during their waiting period

Thrombosis is a serious complication of heart failure for which available data on pediatric patients are scarce. This report describes the frequency and risk factors of clinically significant thrombosis (CST) for children awaiting transplantation. A retrospective study analyzed a cohort of heart recipients with CST, defined by the presence of intracardiac thrombus by imaging, explant pathology, or symptomatic clinical event. Among the 123 patients in the study, 56 % were male and 44 % had congenital heart disease. The median age at transplantation was 6.6 years (range 0-30 years). The prevalence of CST was 12.2 % (15/123), and its incidence was 32.7 events per 100 patient-years. The thromboembolic event frequencies were 2.4 % and 6.5 events per 100 patient-years. The median interval from listing to CST was eight days (range 0-113 days). The median wait-list duration was 31 days (range 8-169 days) in the CST group versus 51 days (range 0-1,743 days) in the non-CST group. Inpatient status was statistically associated with CST (14 of 15 subjects were inpatients, p = 0.03). Inotropic support (p = 0.068) and United Network for Organ Sharing (UNOS) status 1 (p = 0.061) approached significance. Clinically significant thrombosis was common in this end-stage heart failure population. Until randomized clinical trial data are available, it may be reasonable to consider anticoagulation for children admitted with decompensated heart failure and listed as UNOS status 1.

Magnetic resonance coronary angiography: where are we today?

Although cardiovascular magnetic resonance allows the non-invasive and radiation free visualization of both the coronary arteries and veins, coronary vessel wall imaging is still undergoing technical development to improve diagnostic quality. Assessment of the coronary vessels is a valuable addition to the analysis of cardiac function, cardiac anatomy, viability and perfusion which magnetic resonance imaging reliably allows. However, cardiac and respiratory motion and the small size of the coronary vessels present a challenge and require several technical solutions for image optimization. Furthermore, the acquisition protocols need to be adapted to the specific clinical question. This review provides an update on the current clinical applications of cardiovascular magnetic resonance coronary angiography, recent technical advances and describes the acquisition protocols in use.

Warfarin and aspirin in patients with heart failure and sinus rhythm

BACKGROUND

It is unknown whether warfarin or aspirin therapy is superior for patients with heart failure who are in sinus rhythm.

METHODS

We designed this trial to determine whether warfarin (with a target international normalized ratio of 2.0 to 3.5) or aspirin (at a dose of 325 mg per day) is a better treatment for patients in sinus rhythm who have a reduced left ventricular ejection fraction (LVEF). We followed 2305 patients for up to 6 years (mean [±SD], 3.5±1.8). The primary outcome was the time to the first event in a composite end point of ischemic stroke, intracerebral hemorrhage, or death from any cause.

RESULTS

The rates of the primary outcome were 7.47 events per 100 patient-years in the warfarin group and 7.93 in the aspirin group (hazard ratio with warfarin, 0.93; 95% confidence interval [CI], 0.79 to 1.10; P=0.40). Thus, there was no significant overall difference between the two treatments. In a time-varying analysis, the hazard ratio changed over time, slightly favoring warfarin over aspirin by the fourth year of follow-up, but this finding was only marginally significant (P=0.046). Warfarin, as compared with aspirin, was associated with a significant reduction in the rate of ischemic stroke throughout the follow-up period (0.72 events per 100 patient-years vs. 1.36 per 100 patient-years; hazard ratio, 0.52; 95% CI, 0.33 to 0.82; P=0.005). The rate of major hemorrhage was 1.78 events per 100 patient-years in the warfarin group as compared with 0.87 in the aspirin group (P<0.001). The rates of intracerebral and intracranial hemorrhage did not differ significantly between the two treatment groups (0.27 events per 100 patient-years with warfarin and 0.22 with aspirin, P=0.82).

CONCLUSIONS

Among patients with reduced LVEF who were in sinus rhythm, there was no significant overall difference in the primary outcome between treatment with warfarin and treatment with aspirin. A reduced risk of ischemic stroke with warfarin was offset by an increased risk of major hemorrhage. The choice between warfarin and aspirin should be individualized. (Funded by the National Institute of Neurological Disorders and Stroke; WARCEF ClinicalTrials.gov number, NCT00041938.).

Potential quantitative magnetic resonance imaging biomarkers of coronary remodeling in older hypertensive patients

OBJECTIVE

To detect differences in potential magnetic resonance imaging biomarkers of coronary remodeling between older hypertensive patients and healthy controls.

METHODS AND RESULTS

Two-dimensional black-blood coronary wall magnetic resonance imaging and 3-dimensional whole-heart coronary magnetic resonance angiography were performed on 130 participants (65-84 years), including 65 hypertensive patients and 65 healthy controls. Coronary segments derived from hypertensive participants had a higher mean coronary wall thickness, a smaller vessel area, a smaller coronary wall area, a smaller lumen area, a lower coronary distensibility index, and a higher percent of the coronary wall occupying the vessel area (PWOV) than those from healthy controls. When the average PWOV was set as an ad hoc cutoff point, coronary segments with a high PWOV had a significantly higher mean wall thickness, a higher maximum wall thickness, a smaller vessel area, a smaller lumen area, a lower coronary distensibility index, and a higher coronary plaque index compared with coronary segments with a low PWOV.

CONCLUSIONS

Magnetic resonance techniques are able to noninvasively detect significant differences in potential imaging biomarkers of coronary remodeling between older hypertensive patients and healthy controls. The PWOV is a promising remodeling feature for quantitatively evaluating the progression of coronary atherosclerosis.

Coronary imaging with cardiovascular magnetic resonance: current state of the art

Cardiovascular magnetic resonance allows noninvasive and radiation-free visualization of both the coronary arteries and veins, with the advantage of an integrated assessment of cardiac function, viability, perfusion, and anatomy. This combined approach provides valuable integrated information for patients with coronary artery disease and patients undergoing cardiac resynchronization therapy. Moreover, magnetic resonance offers the possibility of coronary vessel wall imaging, therefore assessing the anatomy and pathology of the normal and diseased coronary vessels noninvasively. Coronary magnetic resonance angiography is challenging because of cardiac and respiratory motion and the small size and tortuous path of the coronary vessels. Several technical solutions have been developed to optimize the acquisition protocol to the specific clinical question. The aims of this review are to provide an update on current technical improvements in coronary magnetic resonance angiography, including how to optimize the acquisition protocols, and to give an overview of its current clinical application.

Coronary imaging techniques with emphasis on CT and MRI

Coronary artery imaging in children is challenging, with high demands both on temporal and spatial resolution due to high heart rates and smaller anatomy. Although invasive conventional coronary angiography remains the benchmark technique, over the past 10 years, CT and MRI have emerged in the field of coronary imaging. The choice of hardware is important. For CT, the minimum requirement is a 64-channel scanner. The temporal resolution of the scanner is most important for optimising image quality and minimising radiation dose. Manufacturers have developed several modes of electrocardiographic (ECG) triggering to facilitate dose reduction. Recent technical advances have opened new possibilities in MRI coronary imaging. As a non-ionising radiation technique, MRI is of great interest in paediatric imaging. It is currently recommended in centres with appropriate expertise for the screening of patients with suspected congenital coronary anomalies. However, MRI is still not feasible in infants. This review describes and discusses the technical requirements and the pros and cons of all three techniques.

[Anticoagulant therapy for chronic cardiac diseases. Atrial fibrillation, valvular heart disease, congestive heart failure]

In cardiology, anticoagulant therapy is absolutely indicated after mechanical valve replacement, but is much more often necessary as a prophylactic measure in atrial fibrillation for prevention of embolic stroke. For more than 50 years, there has been no alternative to the oral application of vitamin K antagonists (VKA), which are known to have a very narrow therapeutic window. Despite being highly effective in preventing embolic stroke, many patients are not adequately treated with VKA, and up to 45% of the time the values lie outside the therapeutic range. The reasons for this might be difficult adjustment of VKA dosage, interactions with drugs and food, the necessity of constant monitoring of the blood coagulation, and the fear of severe bleeding complications. More recently, different anticoagulants binding directly to thrombin or factor Xa have been developed, which allows anticoagulant therapy without the need for numerous coagulation checks, representing a major breakthrough in anticoagulant therapy. In this review, the new guidelines for the use of antithrombotic therapy in atrial fibrillation are presented, followed by a discussion of study results with the new thrombin inhibitors and factor Xa inhibitors for prevention of thromboembolic stroke. Moreover, principles of anticoagulant therapy in valvular heart disease and chronic heart failure are described.

Subject-specific estimation of respiratory navigator tracking factor for free-breathing cardiovascular MR

A mean respiratory navigator tracking factor of 0.6 is commonly used to estimate the respiratory motion of the heart from the displacement of the right hemi-diaphragm. A constant tracking factor can generate significant residual error in estimation of the respiratory motion of the heart for the cases where the actual tracking factor highly deviates from 0.6. In this study, we implemented and evaluated a robust method to calculate a subject-specific tracking factor for free-breathing high resolution cardiac MR. The subject-specific tracking factor was calculated from two consecutive navigator signals placed on the right hemi-diaphragm and the basal left ventricle in a training phase. To verify the accuracy of the estimated subject-specific tracking factor, nineteen subjects were recruited for comparing the estimated tracking factor in real-time with an image-based tracking factor, calculated off-line. Subsequently, in seven adult subjects, whole-heart or targeted coronary artery MR images were acquired using the estimated subject-specific tracking factor and visually compared with those acquired using a constant (0.6) tracking factor. It was shown that the proposed method can accurately estimate the subject-specific tracking factor and improve the quality of coronary images when the subject-specific tracking factor differs from 0.6.

[MR imaging of coronary arteries: noncontrast free-breathing whole heart acquisition with ultrafast 3D balanced gradient-echo technique]

The 3D balanced gradient-echo technique is described along with th eimaging protocol for MR imaging of th ecoronary arteries. A 3D volume with spatial resolution of 0.6 x 0.6 x 0.75 mm composed of 140 slices covering the whole heart is acquired over 10 minutes. The main advantage of this whole heart technique is the possibility to image the coronary arteries along their entire course in a single acquisition. Selection of the navigator positions, timing of image acquisition and its duration through the R-R interval are the main factors requiring optimization.

A respiratory self-gating technique with 3D-translation compensation for free-breathing whole-heart coronary MRA

Respiratory motion remains a major challenge for robust coronary MR angiography (MRA). Diaphragmatic navigator (NAV) suffers from indirect measurement of heart position. Respiratory self-gating (RSG) approaches improve motion detection only in the head-feet direction, leaving motion in the other two dimensions unaccounted for. The purpose of this study was to extend conventional RSG (1D RSG) to RSG capable of 3D motion detection (3D RSG) by acquiring additional RSG projections with transverse-motion-encoding gradients. Simulation and volunteer studies were conducted to validate the effectiveness of this new method. Preliminary comparison was performed between coronary artery images reconstructed from the same datasets using different motion correction methods. Our simulation illustrates that a proper motion-encoding gradient and derivation method enable accurate 3D motion detection. Results from whole-heart coronary MRA show that 3D RSG can further reduce motion artifacts as compared to NAV and 1D RSG and enables use of larger gating windows for faster coronary imaging.

Anticoagulation in patients with heart failure and normal sinus rhythm

PURPOSE

The evidence evaluating the risk of thrombosis and the efficacy and risk of anticoagulation in patients with systolic heart failure (HF) and normal sinus rhythm is reviewed.

SUMMARY

Although a subject of investigation for over 50 years, use of anticoagulation in patients with HF remains an area of controversy and clinical debate. While early studies reported variable thromboembolism rates in HF (1.9-42.4 events per 100 patient years), the annual rate from larger and more recent trials ranged from 1% to 3%. The trials evaluating the role of oral anticoagulants to reduce thromboembolism and mortality outcomes in patients with a reduced ejection fraction (EF) have provided ambiguous results. Early studies and post hoc analyses of large clinical trials have demonstrated a reduction in thromboembolic events, risk of stroke, and mortality. In contrast, recent underpowered prospective controlled studies found no benefit in the use of warfarin in patients with systolic HF and normal sinus rhythm. The low-to-moderate risk of thromboembolism in patients with HF and the questionable benefit of anticoagulation need to be weighed against the potential for hemorrhagic complications caused by this therapy. The available data collectively suggest that the risk of using warfarin in patients with reduced EF may outweigh any possible benefit, if one exists at all.

CONCLUSION

Anticoagulation therapy in patients with HF and normal sinus rhythm is not supported by the limited evidence. The benefits of anticoagulation in such patients may not compensate for the relatively high risk of major bleeding caused by the treatment.

Coronary anomalies assessed by whole-heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease

PURPOSE

To determine the value of whole-heart three-dimensional magnetic resonance imaging (MRI) for coronary artery imaging in children/adolescents with congenital heart disease (CHD).

MATERIALS AND METHODS

Forty children/adolescents (median age: 14 years, range 2.6-25.8) with CHD underwent free-breathing navigator-gated isotropic three-dimensional steady-state free-precession (3D-SSFP) MRI for cardiac morphology. Two observers independently evaluated visibility of origin, course, vessel lengths, image quality (IQ), and contrast between coronary lumen and myocardium. A subgroup was compared with cardiac catheter.

RESULTS

The total scan time was 6.3 +/- 3.2 minutes (mean +/- SD, at mean heart rate 76 +/- 15/min). The mean vessel length for right coronary artery (RCA) by observer 1 was 97 +/- 43 mm (observer 2: 94 +/- 37 mm), for left main and anterior descending artery (LM/LAD) 91 +/- 40 mm (observer 2: 90 +/- 40 mm), and for left circumflex artery (LCX) 64 +/- 28mm (observer 2: 66 +/- 28 mm). The mean vessel contrast was 0.34 +/- 0.05 (range: 0.23-0.45; maximum = 1, minimum = 0). On a 4-level score (1 = nondiagnostic, 4 = excellent), mean IQ scores ranged between 2.3-2.9 (+/-0.8-1.0). Both observers agreed on the presence/proximal course of RCA in 40/40, LM/LAD in 38/40, and LCX in 36/40 patients. There was complete agreement with invasive coronary angiography available in 12/40 patients (six anomalies).

CONCLUSION

Isotropic whole-heart 3D-MRI for cardiac morphology allows reliable discrimination between normal and abnormal coronary anatomy in children/adolescents with CHD.

Randomized trial of warfarin, aspirin, and clopidogrel in patients with chronic heart failure: the Warfarin and Antiplatelet Therapy in Chronic Heart Failure (WATCH) trial

BACKGROUND

Chronic heart failure remains a major cause of mortality and morbidity. The role of antithrombotic therapy in patients with chronic heart failure has long been debated. The objective of this study was to determine the optimal antithrombotic agent for heart failure patients with reduced ejection fractions who are in sinus rhythm.

METHODS AND RESULTS

This prospective, randomized clinical trial of open-label warfarin (target international normalized ratio of 2.5 to 3.0) and double-blind treatment with either aspirin (162 mg once daily) or clopidogrel (75 mg once daily) had a 30-month enrollment period and a minimum of 12 months of treatment. We enrolled 1587 men and women >/=18 years of age with symptomatic heart failure for at least 3 months who were in sinus rhythm and had left ventricular ejection fraction of

CONCLUSIONS

The primary outcome measure and the mortality data do not support the primary hypotheses that warfarin is superior to aspirin and that clopidogrel is superior to aspirin.

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MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Aspirin/administration & dosage
• Chronic Disease
• Clopidogrel
• Death
• Double-Blind Method
• Female
• Fibrinolytic Agents/administration & dosage
• Heart Failure/complications
• Heart Failure/drug therapy
• Heart Failure/mortality
• Humans
• Male
• Middle Aged
• Myocardial Infarction
• Stroke
• Stroke Volume
• Ticlopidine/administration & dosage
• Ticlopidine/analogs & derivatives
• Warfarin/administration & dosage

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Affiliation(s)

Barry M Massie Department of Veterans Affairs, San Francisco, CA, USA
Joseph F Collins
Susan E Ammon
Paul W Armstrong
John G F Cleland
Michael Ezekowitz
Syed M Jafri
William F Krol
Christopher M O'Connor
Kevin A Schulman
Koon Teo
Stuart R Warren

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A dual-projection respiratory self-gating technique for whole-heart coronary MRA

PURPOSE

To investigate the accuracy of a dual-projection respiratory self-gating (DP-RSG) technique in dynamic heart position measurement and its feasibility for free-breathing whole-heart coronary MR angiography (MRA).

MATERIALS AND METHODS

A DP-RSG method is proposed to enable accurate direct measurement of heart position by acquiring two whole-heart projections. On 14 volunteers we quantitatively evaluated the efficacy of DP-RSG by comparison with diaphragmatic navigator (NAV) and single-projection-based respiratory self-gating (SP-RSG) methods. For DP-RSG we also compared center-of-mass and two profile-matching algorithms in deriving heart motion. Coronary imaging was conducted on eight volunteers based on retrospective gating to preliminarily validate the effectiveness of DP-RSG for whole-heart coronary MRA. Comparison of vessel delineation was performed between images reconstructed using different gating methods.

RESULTS

The quantitative evaluation shows that DP-RSG more accurately tracks heart motion than NAV with all gating window (GW) values and SP-RSG approaches with GW>or=2.5 mm and profile-matching algorithms are more reliable for motion derivation than center-of-mass calculations with GW>or=1.0 mm. Whole-heart coronary MRA studies demonstrate the feasibility of using DP-RSG to improve overall delineation of the coronary arteries.

CONCLUSION

DP-RSG is a promising approach to better resolve respiratory motion for whole-heart coronary MRA compared to conventional NAV and SP-RSG.

The Role for Anticoagulation with Warfarin in Patients with Systolic Heart Failure and Normal Sinus Rhythm

Objective:

To evaluate the role of anticoagulation with warfarin in patients with systolic heart failure (HF) and normal sinus rhythm (NSR).

Data Sources:

Literature was accessed through MEDLINE (1950–December 2007) and the American College of Cardiology Annual Scientific Session (2004) using the terms heart failure, warfarin, and anticoagulation.

Study Selection and Data Extraction:

All articles in English identified via the searches were evaluated. We excluded trials that evaluated the use of anticoagulation in patients with atrial fibrillation (AF) or valvular disorders.

Data Synthesis:

Patients with systolic HF are considered to be in a prothrombotic state. Studies have demonstrated a decreased incidence of thromboembolic events with anticoagulation therapy in patients with HF and concomitant AF, valvular dysfunction, or hypercoagulable disorders, but there are limited data supporting the role of anticoagulation in patients with HF and NSR. There are 3 prospective clinical trials and 1 ongoing trial designed to assess the efficacy of warfarin in patients with HF and NSR. These trials compare warfarin with antiplatelet therapy or no antithrombotic therapy. Warfarin did not show a benefit in the primary clinical composite outcome of death, myocardial infarction, or stroke, but was associated with more adverse events. However, these trials were underpowered to detect a difference between treatment arms.

Conclusions:

There is no objective evidence to support the need for anticoagulation with warfarin in patients with systolic HF and NSR. Additional large randomized, controlled trials need to be completed to determine the efficacy and safety of anticoagulation with warfarin in such patients.

Fast four-dimensional coronary MR angiography with k-t GRAPPA

PURPOSE

To investigate the effectiveness of k-t GRAPPA for accelerating four-dimensional (4D) coronary MRA in comparison with GRAPPA and the feasibility of combining variable density undersampling with conventional k-t GRAPPA (k-t(2) GRAPPA) to alleviate the overhead of acquiring autocalibration signals.

MATERIALS AND METHODS

The right coronary artery of nine healthy volunteers was scanned at 1.5 Tesla. The 4D k-space datasets were fully acquired and subsequently undersampled to simulate partially parallel acquisitions, namely, GRAPPA, k-t GRAPPA, and k-t(2) GRAPPA. Comparisons were made between the images reconstructed from full k-space datasets and those reconstructed from undersampled k-space datasets.

RESULTS

k-t GRAPPA significantly reduced artifacts compared with GRAPPA and high acceleration factors were achieved with only minimal sacrifices in vessel depiction. k-t(2) GRAPPA could further increase imaging speed without significant losses in image quality.

CONCLUSION

By exploiting high-degree spatiotemporal correlations during the rest period of a cardiac cycle, k-t GRAPPA and k-t(2) GRAPPA can greatly increase data acquisition efficiency and, therefore, are promising solutions for fast 4D coronary MRA.

Risk of Thromboembolism in Heart Failure

Background— In patients with heart failure, rates of clinically apparent stroke range from 1.3% to 3.5% per year. Little is known about the incidence and risk factors in the absence of atrial fibrillation. In the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), 2521 patients with moderate heart failure were randomized to receive amiodarone, implanted cardioverter-defibrillators (ICDs), or placebo.

Methods and Results— We determined the incidence of stroke or peripheral or pulmonary embolism in patients with no history of atrial fibrillation (n=2114), predictors of thromboembolism and the relationship to left ventricular ejection fraction. Median follow-up was 45.5 months. Kaplan-Meier estimates (95% CIs) for the incidence of thromboembolism by 4 years were 4.0% (3.0% to 4.9%), with 2.6% (1.1% to 4.1%) in patients randomized to amiodarone, 3.2% (1.8% to 4.7%) in patients randomized to ICD, and 6.0% (4.0% to 8.0%) in patients randomized to placebo (approximate rates of 0.7%, 0.8%, and 1.5% per year, respectively). By multivariable analysis, hypertension ( P =0.021) and decreasing left ventricular ejection fraction ( P =0.023) were significant predictors of thromboembolism; treatment with amiodarone or ICD treatment was a significant predictor of thromboembolism-free survival ( P =0.014 for treatment effect; hazard ratio [95% CI] versus placebo, 0.57 [0.33 to 0.99] for ICD; 0.44 [0.24 to 0.80] for amiodarone). Inclusion of atrial fibrillation during follow-up in the multivariable model did not affect the significance of treatment assignment as a predictor of thromboembolism.

Conclusions— In the SCD-HeFT patient cohort, which reflects contemporary treatment of patients with moderately symptomatic systolic heart failure, patients experienced thromboembolism events at a rate of 1.7% per year without antiarrhythmic therapy. Those treated with amiodarone or ICDs had lower risk of thromboembolism than those given placebo. Hypertension at baseline and lower ejection fraction were independent predictors of risk.

Coronary Magnetic Resonance Imaging

This article highlights the technical challenges and general imaging strategies for coronary MRI. This is followed by a review of the clinical results for the assessment of anomalous CAD, coronary artery aneurysms, native vessel integrity, and coronary artery bypass graft disease using the more commonly applied MRI methods. It concludes with a brief discussion of the advantages/disadvantages and clinical results comparing coronary MRI with multidetector CT (MDCT) coronary angiography.

Magnetic resonance imaging in the evaluation of non-ischemic cardiomyopathies: current applications and future perspectives

Patients with non-ischemic cardiomyopathy often represent a diagnostic challenge, and correct etiologic diagnosis may influence outcomes. Lately, delayed myocardial enhancement MR imaging has been developed and is currently being used for a growing number of clinical applications. On delayed enhancement MR images, scarring or fibrosis appears as an area of high signal intensity, and the pattern by which this enhancement occurs in the myocardium allows distinction of many different pathologies. In nonischemic cardiomyopathy, the delayed enhancement usually does not occur in a coronary artery distribution and is often midwall rather than subendocardial or transmural. It could also guide myocardial biopsy to an affected area, increasing its yield. Cardiac magnetic resonance imaging has now a definitive role in clinical practice, and its capability to non-invasively provide high resolution images of the heart with good tissue characterization is redefining the understanding of the conditions that can adversely affect the myocardium.

Hemodynamic Modulation of Endocardial Thromboresistance

Background— Patients with heart failure are at increased risk for thromboembolic events, including stroke. Historically attributed to blood stasis, little is known about the adverse effects of elevated chamber filling pressure on endocardial function, which could predispose to intracardiac thrombus formation.

Methods and Results— We investigated changes in the expression of thrombomodulin, a key component of the anticoagulant protein C pathway, in rats subjected to acute atrial pressure overload caused by aortic banding. Acute elevation of left atrial filling pressure, without an associated decline in ventricular systolic function, caused a 70% inhibition of atrial endocardial thrombomodulin expression and resulted in increased local thrombin generation. Targeted restoration of atrial thrombomodulin expression with adenovirus-mediated gene transfer successfully reduced thrombin generation to baseline levels. In vitro co-culture studies revealed that thrombomodulin downregulation is caused by the paracrine release of transforming growth factor-β from cardiac connective tissue in response to mechanical stretch. This was confirmed in vivo by administration of a neutralizing transforming growth factor-β antibody, which effectively prevented thrombomodulin downregulation during acute pressure overload.

Conclusions— These findings suggest that increased hemodynamic load adversely affects endocardial function and is a potentially important contributor to thromboembolus formation in heart failure.

Pharmacological treatment of chronic heart failure

Heart failure (HF) is associated with a high morbidity and mortality in the Western World. Our knowledge of the epidemiology, pathophysiology, and therapy has improved dramatically during the last 20 years. Pharmacological treatment, as it stands today, is a combination of preventive and symptomatic strategies. The mainstay life-saving drugs are angiotensin-converting enzyme inhibitors and beta-blockers. Additional benefits are obtained when angiotensin-receptor blockers or aldosterone antagonists are added. Digitalis and/or diuretics are useful for symptom reduction. In addition, combination therapy with hydralazine and isosorbide dinitrate is recommended in African Americans.

Coronary MR imaging: breath-hold capability and patterns, coronary artery rest periods, and beta-blocker use

PURPOSE

To prospectively evaluate breath-hold capability and patterns, coronary artery rest periods, and beta-blocker use in coronary magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Ethics committee approval and informed consent were obtained. In 210 consecutive patients (mean age, 61.8 years +/- 10.3 [standard deviation]; 146 men, 64 women), breath-hold patterns and maximal capability were assessed at expiration with dynamic navigator MR imaging (temporal resolution, 1 second). Left coronary artery (LCA) and right coronary artery (RCA) rest periods were determined at transverse cine imaging (steady-state free precession, retrospective gating, 40 phases per cycle). Before and after beta-blockade, rest periods were assessed in 25 additional patients (mean age, 61.4 years +/- 7.1; 20 men, five women). Differences were tested within groups with paired Student t test and between groups with unpaired Student t test (continuous variables) and chi(2) test (categoric variables). Pearson correlation was used to test the relationship between rest period and heart rate.

RESULTS

Four distinct breath-hold patterns, characterized by diaphragmatic motion, were identified: pattern 1, steady plateau (55% of patients); 2, initial drift followed by plateau (12%); 3, continuous drift (19%); and 4, irregular, unsteady behavior (14%). Mean breath-hold capability with patterns 1 and 2 was 29 seconds +/- 13 (range, 10-64 seconds). The rest period of LCA was longer than that of RCA (163 msec +/- 75 vs 123 msec +/- 60; P < .01) and began earlier in the cardiac cycle (521 msec +/- 149 vs 540 msec +/- 160; P < .01); In a minority of patients, LCA rest period began later (21%) or was shorter (14%). With no pharmacologic intervention, correlation between rest period duration and heart rate was weak (LCA, r = -0.52; RCA, r = -0.38; P < .01). However, beta-blockade significantly lowered heart rate (61.3 beats/min +/- 7.2 vs 82.6 beats/min +/- 12.5, P < .001) and increased rest duration (LCA, 201.8 msec +/- 83.6 vs 111.8 msec +/- 44.55; RCA, 134.8 msec +/- 57.3 vs 83.1 msec +/- 35.8; P < .001).

CONCLUSION

In 33% of patients (patterns 3 and 4), breath-hold pattern was unsuitable for high-spatial-resolution breath-hold MR imaging. LCA and RCA rest periods showed large variability in starting point and duration, with no correlation to heart rate.

MR-based coronary artery blood velocity measurements in patients without coronary artery disease

To evaluate the feasibility of MR-based coronary blood velocity measurements (MRvenc) in patients without coronary artery disease (CAD). Eighty-three patients with angiographically excluded CAD received MRvenc of the proximal segments of both coronary arteries (CAs). Using a retrospectively ECG-gated breath-hold phase-contrast FLASH sequence with high temporal resolution, flow data were technically acquirable in 137/166 (83%) CAs. Quantification and analysis of blood velocities in systole and diastole of both CAs were performed. Biphasic velocity profiles were found in 83/100 CAs. Median systolic and diastolic velocities differed significantly in LCA (19 cm/s, 24 cm/s; P<0.0001) and RCAs (14 cm/s, 16 cm/s; P<0.01). The diastolic/systolic velocity ratio was calculated in LCAs and RCAs with a median of 1.3 and 1.1, respectively. The velocity profiles of the remaining CAs were monophasic (17 CAs) or revealed severe alterations of the physiologic velocity profile with reduced flow undulations and steady velocities (37 CAs). Optimized clinical MRvenc is feasible to quantify blood velocities in the CAs. Potential indications are (1) non-invasive monitoring of patients after aortic valve reconstruction as well as (2) detection of asymptomatic CAD patients.

Pharmacological prevention of thromboembolism in patients with left ventricular dysfunction

Chronic left ventricular systolic dysfunction is a well recognized problem with an increasingly significant impact on healthcare in the form of congestive heart failure (CHF). Advances in medicine have led to improved survival after myocardial infarction (MI) and as a result, an increased prevalence of left ventricular systolic dysfunction. An increased incidence of thromboembolism, especially stroke, in patients with left ventricular systolic dysfunction is also well recognized. Pharmacological strategies to prevent stroke have been proposed in numerous studies. For example, anticoagulation in patients with atrial fibrillation and heart failure has been shown to reduce mortality rates and the incidence of stroke; however, its role in patients with left ventricular dysfunction and normal sinus rhythm is unclear and utilization of anticoagulation in these patients varies widely. The role of aspirin to prevent thromboembolism in patients with CHF is controversial. The relatively new pharmacological agent ximelagatran, which has an advantage of unmonitored oral administration has the potential to change the anticoagulation strategy in patients with heart failure. Important trials to define optimal therapy for reducing the risk of thromboembolism and death in patients with left ventricular systolic dysfunction and sinus rhythm include the recently reported WATCH (Warfarin and Antiplatelet Therapy in Chronic Heart failure) trial and the WARCEF (Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction) trial, which is currently underway. The WATCH trial failed to outline significant differences between aspirin (acetylsalicylic acid), warfarin, and clopidogrel in the primary composite endpoint of all-cause mortality, nonfatal MI, and nonfatal stroke. Combined data from WATCH and WARCEF may provide sufficient statistical power to clarify outcomes such as stroke and death in patients with reduced cardiac ejection fraction. The pooled data may also help define optimal preventative measures for thromboembolism in patients with left ventricular systolic dysfunction and sinus rhythm.

Rosuvastatin Reduces Platelet Activation in Heart Failure

OBJECTIVES

Endothelial dysfunction and platelet activation are part of the cardiovascular phenotype in congestive heart failure (CHF). We investigated whether 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibition would beneficially modulate vascular NO bioavailability and platelet activation in experimental CHF.

METHODS AND RESULTS

Chronic myocardial infarction was induced by coronary ligation in male Wistar rats. Animals were either treated with placebo or the HMG-CoA reductase inhibitor rosuvastatin. After 10 weeks, hemodynamic assessment was performed and endothelial function was determined in organ bath studies. NO bioavailability was assessed by in vivo platelet vasodilator-stimulated phosphoprotein (VASP) phosphorylation. Markers of platelet degranulation (surface expression of P-selectin and glycoprotein 53) were determined as well as the amount of circulating platelet-leukocyte aggregates. Endothelium-dependent, acetylcholine-induced vasorelaxation was significantly impaired in aortic rings from CHF rats and improved by rosuvastatin. In parallel, in vivo VASP phosphorylation reflecting NO bioavailability was significantly attenuated in platelets from CHF rats and normalized by rosuvastatin. Platelet activation, which was increased in CHF, was reduced by treatment with rosuvastatin.

CONCLUSIONS

HMG-CoA reductase inhibition improved endothelial function, increased systemic NO bioavailability and inhibited exaggerated platelet activation in CHF rats. These mechanisms may contribute to the beneficial effects of statin treatment in CHF.