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Raymond J Kim

Publications and source records attributed to Raymond J Kim.

At least 37 records · Page 2Linked to original sources
PubMed2005

Technology insight: assessment of myocardial viability by delayed-enhancement magnetic resonance imaging.

Myocardial viability is of established importance to the management of cardiac patients being considered for revascularization. Existing noninvasive imaging tests to examine myocardial viability, such as stress echocardiography and nuclear scintigraphy, are of recognized utility but are subject to intrinsic limitations. Over the past few years delayed-enhancement MRI (DE-MRI) has emerged as an alternative to traditional tests and for the first time allows direct visualization of the transmural extent of myocardial viability. In this paper we review the scientific data that underlie the use of DE-MRI in patients with ischemic heart disease. Progress in this area is largely the result of the development of a new MRI pulse sequence in the late 1990s, which improved the detection of necrotic and scarred myocardial tissue. Following this technical development, a series of detailed histologic comparisons in large animal models revealed that both acute and healed myocardial infarcts appeared as brighter (hyperenhanced) areas than viable regions, and that the effect is independent of contractile function. The resulting 'bright is dead' hypothesis has thus far proven of significant use in patients with ischemic heart disease. Data are now emerging which suggest that the DE-MRI technique also has important implications for patients with nonischemic forms of cardiomyopathy.

Contrast Media↗
PubMed2005

Technology insight: MRI of the myocardium.

MRI is emerging as the method of choice for the evaluation of a wide variety of cardiovascular disorders. A major advantage of this technique over the other cardiac imaging modalities is the fact that it allows the operator--via special software programs called pulse sequences--to probe a vast array of biological properties while using the same machine. In this review, we provide the reader with a brief overview of the pulse sequence concept and how it enables MRI practitioners to pursue a multifaceted approach to evaluating the myocardium. We discuss how MRI technology makes this imaging method ideally suited to the assessment of cardiac morphology, contractile function, myocardial perfusion and infarction. In addition, we present clinical scenarios in which the performance of multifaceted imaging by MRI can alter clinical decision making.

Coronary Disease↗
PubMed2005

The case of the disappearing myxoma.

We present a case demonstrating the utility of cardiovascular magnetic resonance (CMR) in the diagnosis of a cardiac mass. A 70-year-old female who presented with chest pressure and left sided jaw pain was found to have a cardiac mass on transthoracic and transesophageal echocardiography that was diagnosed as an atrial myxoma. A cardiac magnetic resonance test determined the mass to be more consistent with a thrombus than a myxoma through a stepwise approach using multiple pulse sequences. Thus, unwarranted and potentially risky thoracic surgery was avoided by the incorporation of a systematic evaluation by cardiac MRI.

Aged↗
PubMed2005

Late gadolinium cardiovascular magnetic resonance in the assessment of myocardial viability.

Delayed-enhancement magnetic resonance imaging is a viability imaging technique that has been demonstrated in both animal and patient studies to accurately identify and characterize the presence and transmural extent of myocardial scarring. The precise information regarding the presence, location and extent of myocardial scarring has been shown to be useful in predicting the likelihood of functional recovery of dysfunctional myocardium after revascularization. Perhaps, more importantly, the ability to visualize the extent of viable and nonviable myocardium across the ventricular wall allows one to approach viability as a continuum rather than in a binary manner, providing a better reflection of the underlying physiology.

Cardiomyopathies↗
PubMed2004

Infarct resorption, compensatory hypertrophy, and differing patterns of ventricular remodeling following myocardial infarctions of varying size.

OBJECTIVES: We sought to identify advantages of contrast-enhanced magnetic resonance imaging (MRI) in studying postinfarction ventricular remodeling. BACKGROUND: Although sequential measurements of ventricular volumes, internal dimensions, and total ventricular mass have provided important insights into postinfarction left ventricular remodeling, it has not been possible to define serial, directionally opposite changes in resorption of infarcted tissue and hypertrophy of viable myocardium and effects of these changes on commonly used indices of remodeling. METHODS: Using gadolinium-enhanced MRI, the time course and geometry of changes in infarcted and noninfarcted regions were assessed serially in dogs subjected to coronary occlusion for 45 min, 90 min, or permanently. RESULTS: Infarct mass decreased progressively between three days and four to eight weeks following coronary occlusion; terminal values averaged 24 +/- 3% of those at three days. Radial infarct thickness also decreased progressively, whereas changes in circumferential and longitudinal extent of infarction were variable. The ability to define the circumferential endocardial and epicardial extents of infarction allowed radial thinning without epicardial expansion to be distinguished from true infarct expansion. The mass of noninfarcted myocardium increased by 15 +/- 2% following 90-min or permanent occlusion. However, the time course of growth of noninfarcted myocardium differed systematically from that of infarct resorption. Measurements of total ventricular mass frequently failed to reflect concurrent changes in infarcted and noninfarcted regions. Reperfusion accelerated infarct resorption. Histologic reductions in nucleus-to-cytoplasm ratios corresponded with increases in noninfarcted ventricular mass. CONCLUSIONS: Concurrent directionally opposite changes in infarcted and noninfarcted myocardium can be defined serially, noninvasively, and with high spatial resolution and full ventricular coverage following myocardial infarction.

Animals↗
PubMed2004

Noninvasive cineangiography by magnetic resonance global coherent free precession.

Cardiovascular disease is primarily diagnosed using invasive X-ray cineangiography. Here we introduce a new concept in magnetic resonance imaging (MRI) that, for the first time, produces similar images noninvasively and without a contrast agent. Protons in moving blood are 'tagged' every few milliseconds as they travel through an arbitrary region in space. Simultaneous with ongoing tagging of new blood, previously tagged blood is maintained in a state of global coherent free precession (GCFP), which allows acquisition of consecutive movie frames as the heart pushes blood through the vascular bed. Body tissue surrounding the moving blood is never excited and therefore remains invisible. In 18 subjects, pulsating blood could be seen flowing through three-dimensional (3D) space for distances of up to 16 cm outside the stationary excitation region. These data underscore that our approach noninvasively characterizes both anatomy and blood flow in a manner directly analogous to invasive procedures.

Cardiac Catheterization↗
PubMed2004

Myonecrosis following stent placement: association between impaired TIMI myocardial perfusion grade and MRI visualization of microinfarction.

Contrast-enhanced cardiac MRI (ceMRI) and TIMI myocardial perfusion grade analysis (TMPG) are proven methods for visualization of microinfarction and assessment of microvascular perfusion, respectively. To determine whether microvascular obstruction accounts for procedure-related myonecrosis, 14 poststent patients, 9 with procedural CK-MB elevation and 5 controls, underwent ceMRI and TMPG. All had TIMI 3 flow pre- and poststent. TMPG was normal in 12/14 pre- and 7/14 poststent. Those with poststent decline in TMPG had higher CK-MB (median, 41.0 vs. 7.4 ng/mL; P = 0.01) and larger infarct mass (median, 3.1 vs. 0.89 g; P = 0.04). More extensive myonecrosis (CK-MB > 3 x normal; infarct mass > 3 g) was observed more frequently if there was a poststent decline in TMPG (3/3, 100%, vs. 2/11, 18.2%; P = 0.03). These data support the theory that distal embolization and microvascular obstruction are associated with myonecrosis following otherwise successful coronary stent placement and provide further insight into its pathophysiology.

Adult↗
PubMed2004

Magnetic resonance imaging for the assessment of myocardial viability.

The identification of myocardial viability in the setting of left ventricular (LV) dysfunction is crucial for the prediction of functional recovery following revascularization. Although echocardiography, positron emission tomography (PET), and nuclear imaging have validated roles, recent advances in cardiac magnetic resonance (CMR) technology and availability have led to increased experience in CMR for identification of myocardial viability. CMR has unique advantages in the ability of magnetic resonance spectroscopy (MRS) to measure subcellular components of myocardium, and in the image resolution of magnetic resonance proton imaging. As a result of excellent image resolution and advances in pulse sequences and coil technology, magnetic resonance imaging (MRI) can be used to identify the transmural extent of myocardial infarction (MI) in vivo for the first time. This review of the role of CMR in myocardial viability imaging describes the acute and chronic settings of ventricular dysfunction and concepts regarding the underlying pathophysiology. Recent advances in MRS and MRI are discussed, including the potential for dobutamine MRI to identify viable myocardium and a detailed review of the technique of delayed gadolinium (Gd) contrast hyperenhancement for visualization of viable and nonviable myocardium.

Gadolinium↗
PubMed2004

Improvement in the function of hibernating myocardium in a patient with heart failure due to coronary artery disease receiving high-dose simvastatin.

We report the case of a 70-year-old man with a history of myocardial infarction and coronary artery bypass grafting, presenting with signs and symptoms of heart failure. Cardiac magnetic resonance imaging demonstrated a small amount of scarring in the anteroseptal wall, moderate left ventricular enlargement, and a left ventricular ejection fraction of 26%. Patient was started on simvastatin 20 mg daily, gradually increased to 80 mg daily, which were maintained for another 4 weeks. Twelve weeks after the initial presentation, the patient experienced a marked improvement in his symptoms. Repeat cardiac magnetic resonance imaging showed global improvement in left ventricular contractility, with ejection fraction of 36% and end-diastolic volume decreasing from 230 to 153 ml. We speculate that high-dose statin therapy had a significant role in improving the ventricular function in our patient by improving the endothelial flow. This hypothesis is presently being tested in a larger prospective trial.

Aged↗
PubMed2003

Gadolinium cardiovascular magnetic resonance predicts reversible myocardial dysfunction and remodeling in patients with heart failure undergoing beta-blocker therapy.

BACKGROUND: In some patients with heart failure, beta-blockers can improve left ventricular (LV) function and reduce morbidity and mortality. We hypothesized that gadolinium-enhanced cardiovascular magnetic resonance imaging (CMR) can predict reversible myocardial dysfunction and remodeling in heart failure patients treated with beta-blockers. METHODS AND RESULTS: Forty-five patients with chronic heart failure underwent CMR. Contrast imaging using gadolinium was performed to obtain high-resolution spatial maps of myocardial scarring and viability. Cine imaging was performed to assess LV function and morphology and was repeated in 35 patients after 6 months of beta-blockade. Gadolinium CMR demonstrated scarring in 30 of 45 patients (67%). Scarring was found in 100% of patients with ischemic cardiomyopathy (28 of 28) but in only 12% with nonischemic cardiomyopathy (2 of 17). In the 35 patients who were maintained on beta-blockers and had a second study, there was an inverse relation between the extent of scarring at baseline and the likelihood of contractile improvement 6 months later (P<0.001). For instance, contractility improved in 56% (674 of 1207) of regions with no scarring but in only 3% with >75% scarring (8 of 232). Multivariate analysis showed that the amount of dysfunctional but viable myocardium by CMR was an independent predictor of the change in ejection fraction (P=0.01), mean wall motion score (P=0.0007), LV end-diastolic volume index (P=0.007), and LV end-systolic volume index (P< or =0.0001). CONCLUSIONS: For heart failure patients treated with beta-blockers, gadolinium-enhanced CMR predicts the response in LV function and remodeling.

Adrenergic beta-Antagonists↗
PubMed2003

Relationship of contractile function to transmural extent of infarction in patients with chronic coronary artery disease.

OBJECTIVES: We sought to determine the relationship of contractile function to the transmural extent of infarction (TEI) in patients with chronic coronary artery disease. BACKGROUND: In the setting of reperfused, chronic myocardial infarction (MI), the relationship of contractile function to the TEI has not been established. METHODS: We studied function by cine magnetic resonance imaging (MRI) and the TEI by contrast-enhanced MRI in 31 patients with single-vessel disease 162 +/- 62 days after reperfused first MI. RESULTS: Of all 516 segments with MI, blinded observers were unable to detect abnormal thickening in 193 (37%), and wall thickening measured quantitatively in these segments was 66 +/- 28%. Of the 193 segments, 163 (84%) were infarcts limited to the subendocardium. The average TEI reached 53% before half of the patients had abnormal contractile function. When patients with small MI (< or =5% of total left ventricular [LV] mass) were excluded, the average TEI reached 43% before half the patients had abnormal function. In subjects with small MI (< or =5% of total LV mass [n = 13]), even segments with TEI >75% had normal function (14 of 14) because they were surrounded by normally moving neighbor segments. CONCLUSIONS: In the setting of reperfused chronic MI, the TEI approaches 50% before contractile dysfunction can be systematically identified. Contractile function cannot be used to rule out chronic MI.

Adult↗
PubMed2003

Contrast-enhanced MRI and routine single photon emission computed tomography (SPECT) perfusion imaging for detection of subendocardial myocardial infarcts: an imaging study.

BACKGROUND: Myocardial infarcts are routinely detected by nuclear imaging techniques such as single photon emission computed tomography (SPECT) myocardial perfusion imaging. A newly developed technique for infarct detection based on contrast-enhanced cardiovascular magnetic resonance (CMR) has higher spatial resolution than SPECT. We postulated that this technique would detect infarcts missed by SPECT. METHODS: We did contrast-enhanced CMR and SPECT examinations in 91 patients with suspected or known coronary artery disease. All CMR and SPECT images were scored, using a 14-segment model, for the presence, location, and spatial extent of infarction. To compare each imaging modality to a gold standard, we also acquired contrast-enhanced CMR and SPECT images in 12 dogs with, and three dogs without, myocardial infarction as defined by histochemical staining. FINDINGS: In animals, contrast-enhanced CMR and SPECT detected all segments with nearly transmural infarction (>75% transmural extent of the left-ventricular wall). CMR also identified 100 of the 109 segments (92%) with subendocardial infarction (<50% transmural extent of the left-ventricular wall), whereas SPECT identified only 31 (28%). SPECT and CMR showed high specificity for the detection of infarction (97% and 98%, respectively). In patients, all segments with nearly transmural infarction, as defined by contrast-enhanced CMR, were detected by SPECT. However, of the 181 segments with subendocardial infarction, 85 (47%) were not detected by SPECT. On a per patient basis, six (13%) individuals with subendocardial infarcts visible by CMR had no evidence of infarction by SPECT. INTERPRETATION: SPECT and CMR detect transmural myocardial infarcts at similar rates. However, CMR systematically detects subendocardial infarcts that are missed by SPECT.

Animals↗
PubMed2003

MR imaging of myocardial perfusion and viability.

CMR is a rapidly developing new modality with applications in clinical cardiology for detection and assessment of myocardial ischemia and viability. CMR perfusion results for the detection of ischemia in comparison with stress echocardiography and scintigraphic techniques are reasonable, but all the studies reported to date have been conduced in selected patients. Larger studies in patient populations reflecting a broader spectrum of disease are necessary before perfusion CMR can be envisaged as a clinically reliable and robust diagnostic tool. Other CMR techniques provide a variety of novel methods of obtaining information on postischemic viability. Signs of viability that can be observed by CMR are the absence of late gadolinium-based contrast enhancement in a myocardial region involved in a recent infarct, any sign of wall thickening at rest (which is detectable with high accuracy by CMR), wall thickening after stimulation by low-dose dobutamine, and preserved wall thickness. Conversely, myocardial necrosis is characterized by signal enhancement of the infarct area after injection of Gd-DTPA, reduced wall thickness in chronic infarcts, and absence of a contractile reserve during dobutamine stimulation. Dobutamine CMR and late enhancement contrast-enhanced CMR predict contractile improvement after revascularization.

Contrast Media↗
PubMed2003

How we perform delayed enhancement imaging.

Recently, numerous studies have demonstrated the effectiveness of a segmented inversion recovery fast gradient echo (seg IR-FGE) sequence for differentiating injured from normal myocardium. This technique for delayed enhancement imaging has been shown to be effective in identifying the presence and extent of myocardial infarction, as well as predicting improvement in contractile function after coronary revascularization. In this article we outline the procedure of delayed enhancement imaging performed at our center, describe the seg IR-FGE sequence in more detail, including our process for choosing sequence settings, review our process of image interpretation, and highlight potential pitfalls (and techniques to overcome them) that we have encountered in our experience with performing the technique in over 1500 patients.

Contrast Media↗
PubMed2002

Myocardial scarring in asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy.

OBJECTIVES: We sought to ascertain whether myocardial scarring occurs in living unselected patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: Myocardial scarring is known to occur in select HCM patients, who were highly symptomatic prior to death or who died suddenly. The majority of HCM patients, however, are minimally symptomatic and have not suffered sudden death. METHODS: Cine and gadolinium-enhanced magnetic resonance imaging was performed in 21 HCM patients who were predominantly asymptomatic. Gadolinium hyperenhancement was assumed to represent myocardial scar, and the extent of scar was compared to left ventricular (LV) morphology and function. RESULTS: Scarring was present in 17 patients (81%). Scarring occurred only in hypertrophied regions (> or =10 mm), was patchy with multiple foci, and predominantly involved the middle third of the ventricular wall. All 17 patients had scarring at the junction of the interventricular septum and the right ventricular (RV) free wall. On a regional basis, the extent of scarring correlated positively with wall thickness (r = 0.36, p < 0.0001), and inversely with wall thickening (r = -0.21, p < 0.0001). On a per patient basis, the extent of scarring (mean, 8 +/- 9% of LV mass) was minimally related to maximum wall thickness (r = 0.40, p = 0.07) and LV mass (r = 0.33, p = 0.15), and correlated inversely with ejection fraction (r = -0.46, p = 0.04). CONCLUSIONS: Myocardial scarring is common in asymptomatic or mildly symptomatic HCM patients who have not suffered sudden death. When present, scarring occurs in hypertrophied regions, is consistently localized to the junctions of the septum and RV free wall, and correlates positively with regional hypertrophy and inversely with regional contraction.

Adolescent↗
PubMed2002

Reproducibility of chronic infarct size measurement by contrast-enhanced magnetic resonance imaging.

BACKGROUND: The reproducibility of contrast-enhanced MRI has not been established. We compared MRI reproducibility for infarct size determination with that of (99m)Tc-sestamibi (MIBI) single photon emission computed tomography (SPECT). METHODS AND RESULTS: Patients with chronic myocardial infarction defined by enzymes (peak creatine kinase-MB 173+/-119 U/L) were scanned twice by MRI (MRI I and MRI II, n=20) and twice by SPECT (SPECT I and SPECT II, n=15) on the same day. The MRI contrast agent was injected during MRI I but not MRI II to test the effect of imaging time after contrast. Resting Tc-MIBI SPECT images were acquired and infarct size was determined with commercial software. Infarct size in patients scanned by MRI and SPECT was 14+/-6% of left ventricular mass (%LV) by MRI (range 4%LV to 27%LV) and 14+/-7%LV by SPECT (range 4%LV to 26%LV). MRI I and II scans were performed 10+/-2 and 27+/-3 minutes after contrast, respectively. For MRI, the difference in infarct size between scans I and II (bias) was -0.1%LV, and the coefficient of repeatability was +/-2.4%LV. For SPECT, bias was -1.3%LV, and the coefficient of repeatability was +/-4.0%LV. Within individual patients, no systematic differences in infarct size were detected when the 2 MRI scans were compared, the 2 SPECT scans were compared, or MRI was compared to SPECT. CONCLUSION: The size of healed infarcts measured by contrast-enhanced MRI does not change between 10 and 30 minutes after contrast. The clinical reproducibility of contrast-enhanced MRI for infarct size determination compares favorably with that of routine clinical SPECT.

Chronic Disease↗