JACC: Cardiovascular Imaging

Quantification of Functional Mitral Regurgitation by Real-Time 3D Echocardiography: Comparison With 3D Velocity-Encoded Cardiac Magnetic Resonance

2009-11-01

Objectives: The aim of this study was to evaluate feasibility and accuracy of real-time 3-dimensional (3D) echocardiography for quantification of mitral regurgitation (MR), in a head-to-head comparison with velocity-encoded cardiac magnetic resonance (VE-CMR).Background: Accurate grading of MR severity is crucial for appropriate patient management but remains challenging. VE-CMR with 3D three-directional acquisition has been recently proposed as the reference method.Methods: A total of 64 patients with functional MR were included. A VE-CMR acquisition was applied to quantify mitral regurgitant volume (Rvol). Color Doppler 3D echocardiography was applied for direct measurement, in “en face” view, of mitral effective regurgitant orifice area (EROA); Rvol was subsequently calculated as EROA multiplied by the velocity-time integral of the regurgitant jet on the continuous-wave Doppler. To assess the relative potential error of the conventional approach, color Doppler 2-dimensional (2D) echocardiography was performed: vena contracta width was measured in the 4-chamber view and EROA calculated as circular (EROA-4CH); EROA was also calculated as elliptical (EROA-elliptical), measuring vena contracta also in the 2-chamber view. From these 2D measurements of EROA, the Rvols were also calculated.Results: The EROA measured by 3D echocardiography was significantly higher than EROA-4CH (p < 0.001) and EROA-elliptical (p < 0.001), with a significant bias between these measurements (0.10 cm2 and 0.06 cm2, respectively). Rvol measured by 3D echocardiography showed excellent correlation with Rvol measured by CMR (r = 0.94), without a significant difference between these techniques (mean difference = −0.08 ml/beat). Conversely, 2D echocardiographic approach from the 4-chamber view significantly underestimated Rvol (p = 0.006) as compared with CMR (mean difference = 2.9 ml/beat). The 2D elliptical approach demonstrated a better agreement with CMR (mean difference = −1.6 ml/beat, p = 0.04).Conclusions: Quantification of EROA and Rvol of functional MR with 3D echocardiography is feasible and accurate as compared with VE-CMR; the currently recommended 2D echocardiographic approach significantly underestimates both EROA and Rvol.

Assessment of Myocardial Ischemic Memory Using Persistence of Post-Systolic Thickening After Recovery From Ischemia

2009-11-01

Objectives: We sought to investigate the time course of post-systolic thickening (PST) and systolic abnormality after recovery from brief myocardial ischemia.Background: Myocardial ischemic memory imaging, denoting the visualization of abnormalities provoked by ischemia and sustained even after restoration of perfusion, is desirable and allows after-the-fact recognition of ischemic insult. PST offers a sensitive marker of myocardial ischemia, but whether this abnormal thickening remains after relief from brief ischemia is unclear.Methods: Tissue strain echocardiographic data were acquired from 27 dogs under 2 different conditions of myocardial ischemia induced by either brief coronary occlusion (15 or 5 min) followed by reperfusion (Protocol 1) or by dobutamine stress during nonflow-limiting stenosis (Protocol 2). Peak systolic strain and post-systolic strain index (PSI), a parameter of PST, were analyzed.Results: In Protocol 1, peak systolic strain was significantly decreased in the risk area during occlusion. This decrease in peak systolic strain in the 15-min group did not completely recover to baseline levels even 120 min after reperfusion, whereas the decrease in the 5-min group recovered immediately after reperfusion. We found that PSI was significantly increased during occlusion, but increased PSI in the 5-min group remained until 30 min after reperfusion (−0.19 ± 0.18 [baseline] vs. 0.19 ± 0.14 [30 min], p < 0.05) despite the rapid recovery of peak systolic strain. In Protocol 2, increased PSI was sustained until 20 min after the end of dobutamine infusion (−0.26 ± 0.11 [baseline] vs. −0.16 ± 0.10 [20 min], p < 0.05), although peak systolic strain recovered by 5 min after the end of dobutamine infusion.Conclusions: PST remained longer than abnormal peak systolic strain after recovery from ischemia. Assessment of PST may be valuable for detecting myocardial ischemic memory.

Assessment of Coronary Plaque Progression in Coronary Computed Tomography Angiography Using a Semiquantitative Score

2009-11-01

Objectives: We sought to describe the progression of coronary atherosclerotic plaque over time by computed tomography (CT) angiography stratified by plaque composition and its association with cardiovascular risk profiles.Background: Data on the progression of atherosclerosis stratified by plaque composition with the use of noninvasive assessment by CT are limited and hampered by high measurement variability.Methods: This analysis included patients who presented with acute chest pain to the emergency department but initially showed no evidence of acute coronary syndromes. All patients underwent contrast-enhanced 64-slice CT at baseline and after 2 years with the use of a similar protocol. CT datasets were coregistered and assessed for the presence of calcified and noncalcified plaque at 1 mm cross sections of the proximal 40 mm of each major coronary artery. Plaque progression over time and its association with risk factors were determined. Measurement reproducibility and correlation to plaque volume was performed in a subset of patients.Results: We included 69 patients (mean age 55 ± 12 years, 59% male patients) and compared 8,311 coregistered cross sections at baseline and follow-up. At baseline, any plaque, calcified plaque, and noncalcified were detected in 12.5%, 10.1%, and 2.4% of cross sections per patient, respectively. There was significant progression in the mean number of cross sections containing any plaque (16.5 ± 25.3 vs. 18.6 ± 25.5, p = 0.01) and noncalcified plaque (3.1 ± 5.8 vs. 4.4 ± 7.0, p = 0.04) but not calcified plaque (13.3 ± 23.1 vs. 14.2 ± 22.0, p = 0.2). In longitudinal regression analysis, the presence of baseline plaque, number of cardiovascular risk factors, and smoking were independently associated with plaque progression after adjustment for age, sex, and follow-up time interval. The semiquantitative score based on cross sections correlated closely with plaque volume progression (r = 0.75, p < 0.0001) and demonstrated an excellent intraobserver and interobserver agreement (κ = 0.95 and κ = 0.93, respectively).Conclusions: Coronary plaque burden of patients with acute chest pain significantly increases during the course of 2 years. Progression over time is dependent on plaque composition and cardiovascular risk profile. Larger studies are needed to confirm these results and to determine the effect of medical treatment on progression.

Integrated Assessment of Diastolic and Systolic Ventricular Function Using Diagnostic Cardiac Magnetic Resonance Catheterization: Validation in Pigs and Application in a Clinical Pilot Study

2009-11-01

Objectives: This study sought to develop and validate a method for the integrated analysis of systolic and diastolic ventricular function.Background: An integrated approach to assess ventricular pump function, myocontractility (end-systolic pressure–volume relationship [ESPVR]), and diastolic compliance (end-diastolic pressure–volume relation [EDPVR]) is of high clinical value. Cardiac magnetic resonance (CMR) is well established for measuring global pump function, and catheterization-combined CMR was previously shown to accurately measure ESPVR, but not yet the EDPVR.Methods: In 8 pigs, the CMR technique was compared with conductance catheter methods (gold standard) for measuring the EDPVR in the left and right ventricle. Measurements were performed at rest and during dobutamine administration. For CMR, the ESPVR was estimated with a single-beat approach by synchronizing invasive ventricular pressures with cine CMR–derived ventricular volumes. The EDPVR was determined during pre-load reduction from additional volume data that were obtained from real-time velocity-encoded CMR pulmonary/aortic blood flow measurements. Pre-load reduction was achieved by transient balloon occlusion of the inferior vena cava. The stiffness coefficient β was calculated by an exponential fit from the EDPVR. After validation in the animal experiments, the EDPVR was assessed in a pilot study of 3 patients with a single ventricle using identical CMR and conductance catheter techniques.Results: Bland-Altman tests showed good agreement between conductance catheter–derived and CMR-derived EDPVR. In both ventricles of the pigs, dobutamine enhanced myocontractility (p < 0.01), increased stroke volume (p < 0.01), and improved diastolic function. The latter was evidenced by shorter early relaxation (p < 0.05), a downward shift of the EDPVR, and a decreased stiffness coefficient β (p < 0.05). In contrast, in the patients, early relaxation was inconspicuous but the EDPVR shifted left-upward and the stiffness constant remained unchanged. The observed changes in diastolic function were not significantly different when measured with conductance catheter and CMR.Conclusions: This novel CMR method provides differential information about diastolic function in conjunction with parameters of systolic contractility and global pump function.

Chasing the Elusive Pressure–Volume Relationships⁎

Daniel Burkhoff — 2009-11-01

Quantification of ventricular pump function is fundamental to the practice of cardiology and is required for research into most aspects of cardiac physiology, disease, and therapeutics. Drawing an analogy between the heart and a steam engine, Otto Frank () introduced the pressure–volume diagram as a means of characterizing left ventricular properties in the 1890s. Nearly 80 years later, Suga () formalized the idea that the relationship between pressure and volume at end systole was relatively independent of loading conditions and that the slope of the curve, called Emax or Ees, was a sensitive measure of contractility. At nearly the same time, several investigators demonstrated how the relationship between pressure and volume at end diastole similarly provided the framework for quantifying passive properties of the myocardium (). In the decades to follow, there was intensive research into the characteristics of the end-systolic pressure–volume relation (ESPVR) and end-diastolic pressure–volume relation (EDPVR) and these became the gold standards for quantifying pump function in animal research (). Despite recognition of the major theoretical advantages of this approach (), adoption into clinical research was limited, and this approach has not been incorporated into clinical practice.

Noninvasive Assessment of Pulmonary Artery Flow and Resistance by Cardiac Magnetic Resonance in Congenital Heart Diseases With Unrestricted Left-to-Right Shunt

2009-11-01

Objectives: To determine whether noninvasive assessment of pulmonary artery flow (Qp) by cardiac magnetic resonance (CMR) would predict pulmonary vascular resistance (PVR) in patients with congenital heart disease characterized by an unrestricted left-to-right shunt.Background: Patients with an unrestricted left-to-right shunt who are at risk of obstructive pulmonary vascular disease require PVR evaluation preoperatively. CMR cardiac catheter (XMR) combines noninvasive measurement of Qp by phase contrast imaging with invasive pressure measurement to accurately determine the PVR.Methods: Patients referred for clinical assessment of the PVR were included. The XMR was used to determine the PVR. The noninvasive parameters, Qp and left-to-right shunt (Qp/Qs), were compared with the PVR using univariate regression models.Results: The XMR was undertaken in 26 patients (median age 0.87 years)—ventricular septal defect 46.2%, atrioventricular septal defect 42.3%. Mean aortic flow was 2.24 ± 0.59 l/min/m2, and mean Qp was 6.25 ± 2.78 l/min/m2. Mean Qp/Qs was 2.77 ± 1.02. Mean pulmonary artery pressure was 34.8 ± 10.9 mm Hg. Mean/median PVR was 5.5/3.0 Woods Units (WU)/m2 (range 1.7 to 31.4 WU/m2). The PVR was related to both Qp and Qp/Qs in an inverse exponential fashion by the univariate regression equations PVR = exp(2.53 − 0.20[Qp]) and PVR = exp(2.75 − 0.52[Qp/Qs]). Receiver-operator characteristic (ROC) analysis was used to determine cutoff values for Qp and Qp/Qs above which the PVR could be regarded as clinically acceptable. A Qp of ≥6.05 l/min/m2 predicted a PVR of ≤3.5 WU/m2 with sensitivity 72%, specificity 100%, and area under the ROC curve 0.90 (p = 0.002). A Qp/Qs of ≥2.5/1 predicted a PVR of ≤3.5 WU/m2 with sensitivity 83%, specificity 100%, and area under the curve ROC 0.94 (p < 0.001).Conclusions: Measurement of Qp or left-to-right shunt noninvasively by CMR has potential to predict the PVR in patients with an unrestricted left-to-right shunt and could potentially determine operability without having to undertake invasive testing.

Combined Assessment of Myocardial Perfusion and Late Gadolinium Enhancement in Patients After Percutaneous Coronary Intervention or Bypass Grafts: A Multicenter Study of an Integrated Cardiovascular Magnetic Resonance Protocol

2009-11-01

Objectives: We sought to assess the accuracy of an integrated cardiac magnetic resonance (CMR) protocol for the diagnosis of relevant coronary artery or bypass graft stenosis in patients with suspected coronary artery disease (CAD) or with previously performed percutaneous coronary intervention (PCI) or coronary bypass graft surgery (CABG).Background: CMR is suitable for diagnosing inducible myocardial ischemia in patients with suspected CAD and has been proven to be a helpful diagnostic tool for decision of further treatment. However, little is known about its diagnostic accuracy in patients with known CAD who previously were treated by PCI or CABG.Methods: A total of 477 patients with suspected CAD, 236 with previous PCI, and 110 after CABG referred for coronary X-ray angiography (CXA) underwent an integrated CMR examination before CXA. Myocardial ischemia was assessed using first-pass perfusion after vasodilator stress with adenosine (140 μg/kg/min for 3 min) using gadolinium-based contrast agents (0.1 mmol/kg). Late gadolinium enhancement (LGE) was assessed 10 min after a second contrast bolus.Results: CXA demonstrated a relevant coronary vessel stenosis (≥70% luminal reduction) in 313 (38%) patients using quantitative coronary analysis. The combination of CMR perfusion and LGE assessment for detecting a relevant coronary stenosis in patients with suspected CAD yielded sensitivity and specificity of 0.94 and 0.87, in PCI patients 0.91 and 0.90, and in CABG patients 0.79 and 0.77, respectively.Conclusions: A combined CMR protocol for the assessment of myocardial perfusion and LGE is feasible for the detection of relevant coronary vessel stenosis even in patients who previously were treated by PCI or CAG in a routine clinical setting. However, diagnostic accuracy is reduced in patients with CABG. This could be due to different flow and perfusion kinetic. Further studies are needed to optimize the clinical protocols especially in post-surgical patients.

A Study of the Effects of Ranolazine Using Automated Quantitative Analysis of Serial Myocardial Perfusion Images

2009-11-01

Objectives: This study examined the hypothesis that the improvement in myocardial blood flow (MBF) with ranolazine therapy could be detected by serial automated quantitative myocardial perfusion imaging (MPI) in patients with coronary artery disease (CAD) and myocardial ischemia.Background: Myocardial ischemia enhances late sodium current, which then causes cellular calcium overload leading to mechanical left ventricular dysfunction and arrhythmias. Ranolazine inhibits late sodium current and improves diastolic tension and MBF in the animal model.Methods: In this open-label, nonrandomized pilot study, we recruited 20 patients with known or a high probability of CAD and who had reversible perfusion defects on exercise treadmill gated single-photon emission computed tomography MPI while receiving conventional antianginal therapy. Ranolazine (up to 1,000 mg twice daily) was added to baseline therapy and a repeat treadmill MPI was obtained after 4 weeks. The extent and severity of total and reversible left ventricular perfusion abnormality (based on polar maps and a 17-segment model) were determined quantitatively using automated methods.Results: We screened 100 patients for 27 potential candidates; 5 declined and 2 did not complete the follow-up study. The mean age of the remaining 20 patients was 64 ± 9 years; 30% were women and 50% had diabetes mellitus. The exercise time increased (425 ± 105 s vs. 393 ± 116 s, p = 0.017), and angina improved in 15 (75%) patients after ranolazine treatment. In the entire cohort, summed stress scores (10 ± 7 vs. 13 ± 8, p = 0.04) and summed difference scores (4.7 ± 4 vs. 7.4 ± 5, p = 0.0037) decreased at follow-up. An improvement in perfusion pattern and severity was noted in 14 (70%) patients. In these patients, the polar maps showed a decrease in total abnormality from 26 ± 17% to 19 ± 15% and a decrease in the reversible abnormality from 16 ± 10% to 8 ± 6% (all p values <0.05).Conclusions: In this preliminary hypothesis-driven study, short-term ranolazine therapy was shown to improve myocardial perfusion and decrease the ischemic burden in patients with CAD.

Ranolazine and the Myocardial Demand–Supply Balance⁎

Francis J. Klocke — 2009-11-01

The emergence of ranolazine as an effective antianginal agent () has prompted recurring interest in identifying mechanisms by which this agent can favorably affect the imbalance between myocardial oxygen demand and supply underlying anginal episodes.

Myocardial Blood Volume Is Associated With Myocardial Oxygen Consumption: An Experimental Study With Cardiac Magnetic Resonance in a Canine Model

2009-11-01

Understanding the oxygen consumption of the left ventricular myocardium provides important insight into the relationship between myocardial oxygen supply and demand. In other territories, cardiac magnetic resonance has been utilized to measure myocardial oxygen consumption with a blood level oxygen dependent (BOLD) technique. The BOLD technology requires repetitive sampling of stationary tissues and is frequently implemented in areas such as the brain. A limitation to utilizing BOLD cardiac magnetic resonance techniques in the heart has been cardiac motion. In this study, we document a methodology for acquiring BOLD images in the heart and demonstrate the utility of the technique for identifying associations between myocardial oxygen consumption and blood flow.

Interventional Cardiovascular Magnetic Resonance Imaging: A New Opportunity for Image-Guided Interventions

Christina E. Saikus, Robert J. Lederman — 2009-11-01

Cardiovascular magnetic resonance (CMR) combines excellent soft-tissue contrast, multiplanar views, and dynamic imaging of cardiac function without ionizing radiation exposure. Interventional cardiovascular magnetic resonance (iCMR) leverages these features to enhance conventional interventional procedures or to enable novel ones. Although still awaiting clinical deployment, this young field has tremendous potential. We survey promising clinical applications for iCMR. Next, we discuss the technologies that allow CMR-guided interventions and, finally, what still needs to be done to bring them to the clinic.

Echocardiography for Percutaneous Heart Pumps

Amit K. Mehrotra, Dipak Shah, Lissa Sugeng, Neeraj Jolly — 2009-11-01

two commercially available percutaneous heart pumps include TandemHeart (CardiacAssist, Inc., Pittsburgh, Pennsylvania) and Impella 2.5 (Abiomed, Danvers, Massachusetts), and they currently are used to support high-risk percutaneous coronary interventions or acutely failing ventricles. TandemHeart () pumps blood out of the left atrium and ejects it into the iliac artery. Impella 2.5 () aspirates blood from the left ventricle and ejects it into the ascending aorta. Echocardiography adds significant value in the safe placement of these devices, as well as understanding the interplay between these heart pumps and cardiac hemodynamics.

3-Dimensional Echocardiographic Assessment of Left Ventricular Dyssynchrony: An Alternative Viewpoint

2009-11-01

The results in the article by Sonne et al. () confirm those previously published by ourselves and others with respect to the dependence of 3-dimensional systolic dyssynchrony index (SDI) on age, left ventricular (LV) function, and QRS duration (). However, the authors have derived conclusions that are in direct conflict to their previous (surprisingly not quoted here) work () and that of many others ().

Reply

Victor Mor-Avi, Roberto M. Lang — 2009-11-01

We are well aware of the previous publications on the various applications of real-time 3D echocardiography (RT3DE), including those published by your group and obviously by ours. We greatly respect your work and your opinions, even when you disagree with us. We also are aware that some of the findings from our recent study might be interpreted as controversial and have anticipated a debate after its publication. In our view, such a healthy debate is a legitimate part of the work of scientists, and it is what differentiates science from nonscientific theories that cannot be disputed, proved, or disproved.

Interventional CMR: Great Promise, but a Long Road Ahead

Christopher M. Kramer, Jagat Narula — 2009-11-01

Performing interventions in a cardiac magnetic resonance (CMR) environment can be viewed as somewhat of a Herculean task. However, the soft tissue contrast afforded by CMR, and the excellent image quality have attracted many into this developing field. There are a number of laboratories actively working on novel cardiovascular procedures; many have been performed in large animals, but some in patients with congenital heart disease as well (). The pediatric interventionalists have selectively focused on interventional cardiac magnetic resonance (iCMR) to avoid radiation risk. These investigators should be applauded as it takes substantial commitment and significant resources. Such an endeavor requires specialized equipment including magnetic resonance (MR)-compatible catheters, which not only complicates but raises the expense of the procedure.