Value of semiquantitative assessment of high-risk plaque features on coronary CT angiography over stenosis in selection of studies for FFRct.

INTRODUCTION: The degree of stenosis on coronary CT angiography (CCTA) guides referral for CT-derived flow reserve (FFRct). We sought to assess whether semiquantitative assessment of high-risk plaque (HRP) features on CCTA improves selection of studies for FFRct over stenosis assessment alone. METHODS: Per-vessel FFRct was computed in 1,395 vessels of 836 patients undergoing CCTA with 25-99% maximal stenosis. By consensus analysis, stenosis severity was graded as 25-49%, 50-69%, 70-89%, and 90-99%. HRPs including low attenuation plaque (LAP), positive remodeling (PR), and spotty calcification (SC) were assessed in lesions with maximal stenosis. Lesion FFRct was measured distal to the lesion with maximal stenosis, and FFRct<0.80 was defined as abnormal. Association of HRP and abnormal lesion FFRct was evaluated by univariable and multivariable logistic regression models. RESULTS: The frequency of abnormal lesion FFRct increased with increase of stenosis severity across each stenosis category (25-49%:6%; 50-69%:30%; 70-89%:54%; 90-99%:91%, p â€‹< â€‹0.001). Univariable analysis demonstrated that stenosis severity, LAP, and PR were predictive of abnormal lesion FFRct, while SC was not. In multivariable analyses considering stenosis severity, presence of PR, LAP, and PR and/or LAP were independently associated with abnormal FFRct: Odds ratio 1.58, 1.68, and 1.53, respectively (p â€‹< â€‹0.02 for all). The presence of PR and/or LAP increased the frequency of abnormal FFRct with mild stenosis (p â€‹< â€‹0.05) with a similar trend with 70-89% stenosis. The combination of 2 HRP (LAP and PR) identified more lesions with FFR < 0.80 than only 1 HRP. CONCLUSIONS: Semiquantitative visual assessment of high-risk plaque features may improve the selection of studies for FFRct.

Synergistic Assessment of Mortality Risk According to Body Mass Index and Exercise Ability and Capacity in Patients Referred for Radionuclide Stress Testing.

OBJECTIVE: To determine the interrelationship between body mass index (BMI), mode of stress testing (exercise or pharmacological), exercise capacity, and all-cause mortality in patients referred for stress-rest single photon emission computed tomography myocardial perfusion imaging. PATIENTS AND METHODS: We evaluated all-cause mortality in 21,638 patients undergoing stress-rest single photon emission computed tomography myocardial perfusion imaging between January 2, 1991, and December 31, 2012. Patients were divided into exercise and pharmacologically tested groups and 9 BMI categories. The median follow-up was 12.8 years (range, 5.0-26.8 years). RESULTS: In exercise patients, mortality was increased with both low and high BMI vs patients with a normal referent BMI of 22.5 to 24.9 kg/m2. In pharmacologically tested patients, only low BMI, but not high BMI, was associated with increased mortality vs normal BMI. When exercise and pharmacologically tested groups were compared directly, pharmacologically tested patients manifested a marked increase in mortality risk vs exercise patients within each BMI category, ranging from an approximately 4-fold increase in mortality in those with normal or high BMI to a 12.3-fold increase in those with low BMI values. Similar findings were observed in a cohort of 4804 exercise and 4804 pharmacologically tested patients matched to have similar age and coronary artery disease risk factor profiles. In exercise patients, further risk stratification was achieved when considering both BMI and metabolic equivalent tasks of achieved exercise. CONCLUSION: The combined assessment of BMI and exercise ability and capacity provides synergistic and marked risk stratification of future mortality risk in patients referred for radionuclide stress testing, providing considerable insights into the "obesity paradox" that is observed in populations referred for stress testing.

Tricuspid Regurgitation, the Forgotten Valvular Lesion-A Contemporary Review of Etiology, Prevalence, and Management Options.

Tricuspid regurgitation (TR) is a common finding. Pathologic TR is an independent risk factor for mortality. TR can be classified by etiology into functional versus organic. Organic TR is caused by structural damage to the tricuspid valve (TV) by a spectrum of etiologies, including pacemaker leads and right heart biopsies, whereas functional TR is predominantly due to elevated pulmonary pressures. Atrial fibrillation and chamber enlargement, among other risk factors, are strong predictors of functional TR. Correction of elevated pulmonary pressures improves TR, and concurrent repair of severe TR at the time of left heart valve surgery improves postoperative heart failure symptoms but does not improve survival. TR repair is associated with less operative and long-term mortality than TV replacement, and demonstrates similar improvements in heart failure symptoms. Substantial residual TR remains after repair, and reoperative mortality for residual TR is considerable. Percutaneous TV replacement may offer a rescue strategy.

Combined Quantitative Assessment of Myocardial Perfusion and Coronary Artery Calcium Score by Hybrid 82Rb PET/CT Improves Detection of Coronary Artery Disease.

UNLABELLED: Hybrid PET myocardial perfusion imaging (MPI) with CT allows the incorporation of coronary artery calcium (CAC) into the clinical protocol. We aimed to determine whether the combined analysis of MPI and CAC could improve the diagnostic accuracy of PET MPI in detection of obstructive coronary artery disease (CAD). METHODS: Consecutive patients (n = 152; mean age ± SD, 69 ± 12 y) without prior CAD, referred to (82)Rb PET MPI followed by invasive coronary angiography performed within 14 days, were studied. Myocardial perfusion was quantified automatically for left anterior descending, left circumflex, and right coronary artery territories as an ischemic total perfusion deficit (ITPD) for 456 vessels. Global and per-vessel CAC Agatston scores were calculated. Obstructive CAD was defined as 50% or greater stenosis of the left main and 70% or greater stenosis in the left anterior descending, left circumflex, and right coronary arteries. Logistic regression and 10-fold cross validation were used to derive and validate the combined ITPD/logCAC (logarithm of coronary calcium) scores. RESULTS: In the prediction of per-vessel obstructive CAD, the receiver-operating-characteristic area under the curve for combined per-vessel ITPD/logCAC score was higher, 0.85 (95% confidence interval [CI], 0.81-0.89), than standalone ITPD area under the curve, 0.81 (95% CI: 0.76-0.85), and logCAC score, 0.73 (95% CI, 0.68-0.78; P < 0.05). The integrated discrimination improvement of combined per-vessel ITPD/logCAC analysis was 0.07 (95% CI, 0.04-0.09; P < 0.0001), as compared with ITPD alone. CONCLUSION: Combined automatically derived per-vessel ITPD and logCAC score improves accuracy of (82)Rb PET MPI for detection of obstructive CAD.

Long-term mortality following normal exercise myocardial perfusion SPECT according to coronary disease risk factors.

BACKGROUND: While normal exercise myocardial perfusion imaging (SPECT-MPI) is a robust predictor of low short-term clinical risk, there is increasing interest in ascertaining how clinical factors influence long-term risk following SPECT-MPI. METHODS: We evaluated the predictors of outcome from clinical data obtained at the time of testing in 12,232 patients with normal exercise SPECT-MPI studies. All-cause mortality (ACM) was assessed at a mean of 11.2 ± 4.5 years using the Social Security Death Index. RESULTS: The ACM rate was 0.8%/year, but varied markedly according to the presence of CAD risk factors. Hypertension, smoking, diabetes, exercise capacity, dyspnea, obesity, higher resting heart rate, an abnormal ECG, LVH, atrial fibrillation, and LVEF < 45% were all predictors of increased mortality. Risk factors were synergistic in predicting mortality: annualized age and gender-adjusted ACM rates ranged from only 0.2%/year among patients exercising for >9 minutes having none of three significant risk factors (among hypertension, diabetes, and smoking) to 1.6%/year among patients exercising <6 minutes and having ≥ 2 of these three risk factors. The age and gender-adjusted hazard ratio for mortality was increased by 7.3 (95% confidence interval 5.5-9.7) in the latter patients compared to those patients who exercised >9 minutes and had no significant risk factors (P < .001). CONCLUSIONS: Long-term mortality risk varies markedly in accordance with baseline CAD risk factors and functional capacity among patients with normal exercise SPECT-MPI studies. Further study is indicated to determine whether the prospective characterization of both short-term and long-term risks following the performance of stress SPECT-MPI leads to improved clinical management.

Cardiac magnetic resonance imaging myocardial perfusion reserve index assessment in women with microvascular coronary dysfunction and reference controls.

OBJECTIVE: We sought to comparatively assess cardiac magnetic resonance imaging (CMRI) myocardial perfusion reserve index (MPRI) in women with confirmed microvascular coronary dysfunction (MCD) cases and reference control women. BACKGROUND: Women with signs or symptoms of myocardial ischemia in the absence of obstructive coronary artery disease (CAD) frequently have MCD which carries an adverse prognosis. Diagnosis involves invasive coronary reactivity testing (CRT). Adenosine CMRI is a non-invasive test that may be useful for the detection of MCD. METHODS: Fifty-three women with MCD confirmed by CRT and 12 age- and estrogen-use matched reference controls underwent adenosine CMRI. CMRI was assessed for MPRI, calculated using the ratio of myocardial blood flow at hyperemia/rest for the whole myocardium and separately for the 16 segments as defined by the American Heart Association. Statistical analysis was performed using repeated measures ANOVA models. RESULTS: Compared to reference controls, MCD cases had lower MPRI values globally and in subendocardial and subepicardial regions (1.63±0.39 vs. 1.98±0.38, P=0.007, 1.51±0.35 vs. 1.84±0.34, P=0.0045, 1.68±0.38 vs. 2.04±0.41, P=0.005, respectively). A perfusion gradient across the myocardium with lower MPRI in the subendocardium compared to the subepicardium was observed for both groups. CONCLUSIONS: Women with MCD have lower MPRI measured by perfusion CMRI compared to reference controls. CMRI may be a useful diagnostic modality for MCD. Prospective validation of a diagnostic threshold for MPRI in patients with MCD is needed.

Assessment of left ventricular regional wall motion and ejection fraction with low-radiation dose helical dual-source CT: comparison to two-dimensional echocardiography.

BACKGROUND: Electrocardiographic (ECG)-based tube current modulation during cardiac CT reduces radiation exposure but significantly increases noise in parts of the cardiac cycle where tube current is minimized. OBJECTIVE: We evaluated the effect of maximal ECG-based tube current reduction on left ventricular (LV) regional wall motion assessment and ejection fraction (EF) by comparing low-radiation helical dual-source CT (DSCT) to 2-dimensional transthoracic echocardiography (2D-TTE). METHODS: We studied 83 consecutive patients (15 with prior myocardial infarction) who underwent helically acquired DSCT coronary angiography with maximal ECG-based tube current modulation (low-radiation helical DSCT) and 2D-TTE within a 6-month period (median, 1 day), without any change in clinical status between the studies. In all patients, full tube current was applied only at 70% of the R-R interval, with minimal tube current (4% of maximum) in all other parts of the cardiac cycle. Reduced tube voltage (100 kVp) was combined with the maximal dose modulation in 34 patients. DSCT datasets were evaluated by a blinded, experienced cardiologist. Regional wall motion was assessed with the standard 17-segment model, with each segment scored as normal, hypokinetic, akinetic, and dyskinetic. RESULTS: Mean effective radiation dose for the low-radiation helical DSCT was 5.2 ± 1.7 mSv. Regional wall motion was evaluable in all segments on low-radiation helical DSCT. There was excellent agreement of wall motion scoring by low-radiation helical DSCT and 2D-TTE in 1382 of 1411 segments (98%; Cohen's κ value 0.83; 95% confidence interval, 0.76-0.89; P < 0.0001). Mean LVEF was 67.6% ± 10.3% on low-radiation helical DSCT and 61.8% ± 10.3% on 2D-TTE (P < 0.0001). CONCLUSION: Low-radiation dose helical coronary CT angiography with maximal ECG-based tube current modulation is comparable to 2D-TTE for regional wall motion and EF assessment.

Assessment of the relationship between stenosis severity and distribution of coronary artery stenoses on multislice computed tomographic angiography and myocardial ischemia detected by single photon emission computed tomography.

BACKGROUND: The relationship between luminal stenosis measured by coronary CT angiography (CCTA) and severity of stress-induced ischemia seen on single photon emission computed tomographic myocardial perfusion imaging (SPECT-MPI) is not clearly defined. We sought to evaluate the relationship between stenosis severity assessed by CCTA and ischemia on SPECT-MPI. METHODS AND RESULTS: ECG-gated CCTA (64 slice dual source CT) and SPECT-MPI were performed within 6 months in 292 patients (ages 26-91, 73% male) with no prior history of coronary artery disease. Maximal coronary luminal narrowing, graded as 0, ≥25%, 50%, 70%, or 90% visual diameter reduction, was consensually assessed by two expert readers. Perfusion defect on SPECT-MPI was assessed by computer-assisted visual interpretation by an expert reader using the standard 17 segment, 5 point-scoring model (stress perfusion defect of ≥5% = abnormal). By SPECT-MPI, abnormal perfusion was seen in 46/292 patients. With increasing stenosis severity, positive predictive value (PPV) increased (42%, 51%, and 74%, P = .01) and negative predictive value was relatively unchanged (97%, 95%, and 91%) in detecting perfusion abnormalities on SPECT-MPI. In a receiver operator curve analysis, stenosis of 50% and 70% were equally effective in differentiating between the presence and absence of ischemia. In a multivariate analysis that included stenosis severity, multivessel disease, plaque composition, and presence of serial stenoses in a coronary artery, the strongest predictors of ischemia were stenosis of 50-89%, odds ratio (OR) 7.31, P = .001, stenosis ≥90%, OR 34.05, P = .0001, and serial stenosis ≥50% OR of 3.55, P = .006. CONCLUSIONS: The PPV of CCTA for ischemia by SPECT-MPI rises as stenosis severity increases. Luminal stenosis ≥90% on CCTA strongly predicts ischemia, while <50% stenosis strongly predicts the absence of ischemia. Serial stenosis of ≥50% in a vessel may offer incremental value in addition to stenosis severity in predicting ischemia.

Reduction in downstream test utilization following introduction of coronary computed tomography in a cardiology practice.

To compare utilization of non-invasive ischemic testing, invasive coronary angiography (ICA), and percutaneous coronary intervention (PCI) procedures before and after introduction of 64-slice multi-detector row coronary computed tomographic angiography (CCTA) in a large urban primary and consultative cardiology practice. We utilized a review of electronic medical records (NotesMD) and the electronic practice management system (Megawest) encompassing a 4-year period from 2004 to 2007 to determine the number of exercise treadmill (TME), supine bicycle exercise echocardiography (SBE), single photon emission computed tomography (SPECT) myocardial perfusion stress imaging (MPI), coronary calcium score (CCS), CCTA, ICA, and PCI procedures performed annually. Test utilization in the 2 years prior to and 2 years following availability of CCTA were compared. Over the 4-year period reviewed, the annual utilization of ICA decreased 45% (2,083 procedures in 2004 vs. 1,150 procedures in 2007, P < 0.01) and the percentage of ICA cases requiring PCI increased (19% in 2004 vs. 28% in 2007, P < 0.001). SPECT MPI decreased 19% (3,223 in 2004 vs. 2,614 in 2007 P < 0.02) and exercise stress treadmill testing decreased 49% (471 in 2004 vs. 241 in 2007 P < 0.02). Over the same period, there were no significant changes in measures of practice volume (office and hospital) or the annual incidence of PCI (405 cases in 2004 vs. 326 cases in 2007) but a higher percentage of patients with significant disease undergoing PCI 19% in 2004 vs. 29% in 2007 P < 0.01. Implementation of CCTA resulted in a significant decrease in ICA and a corresponding significant increase in the percentage of ICA cases requiring PCI, indicating that CCTA resulted in more accurate referral for ICA. The reduction in unnecessary ICA is associated with avoidance of potential morbidity and mortality associated with invasive diagnostic testing, reduction of downstream SPECT MPI and TME as well as substantial savings in health care dollars.

Quantitative assessment of myocardial perfusion abnormality on SPECT myocardial perfusion imaging is more reproducible than expert visual analysis.

BACKGROUND: Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application. METHODS AND RESULTS: We studied 31 patients (age 68 +/- 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 +/- 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns). CONCLUSIONS: In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient.

Aortic size assessment by noncontrast cardiac computed tomography: normal limits by age, gender, and body surface area.

OBJECTIVES: To determine normal limits for ascending and descending thoracic aorta diameters in a large population of asymptomatic, low-risk adult subjects. BACKGROUND: Assessment of aortic size is possible from gated noncontrast computed tomography (CT) scans obtained for coronary calcium measurements. However, normal limits for aortic size by these studies have yet to be defined. METHODS: In 4,039 adult patients undergoing coronary artery calcium (CAC) scanning, systematic measurements of the ascending and descending thoracic aorta diameters were made at the level of the pulmonary artery bifurcation. Multiple linear regression analysis was used to detect risk factors independently associated with ascending and descending thoracic aorta diameter and exclude subjects with these parameters from the final analysis. The final analysis groups for ascending and descending thoracic aorta included 2,952 and 1,931 subjects, respectively. Subjects were then regrouped by gender, age, and body surface area (BSA) for ascending and descending aorta, separately, and for each group, the mean, standard deviation, and upper normal limit were calculated for aortic diameter as well as for the calculated cross-sectional aortic area. Also, linear regression models were used to create BSA versus aortic diameter nomograms by age groups, and a formula for calculating predicted aortic size by age, gender, and BSA was created. RESULTS: Age, BSA, gender, and hypertension were directly associated with thoracic aorta dimensions. Additionally, diabetes was associated with ascending aorta diameter, and smoking was associated with descending aorta diameter. The mean diameters for the final analysis group were 33 +/- 4 mm for the ascending and 24 +/- 3 mm for the descending thoracic aorta, respectively. The corresponding upper limits of normal diameters were 41 and 30 mm, respectively. CONCLUSIONS: Normal limits of ascending and descending aortic dimensions by noncontrast gated cardiac CT have been defined by age, gender, and BSA in a large, low-risk population of subjects undergoing CAC scanning.

Comparative use of radionuclide stress testing, coronary artery calcium scanning, and noninvasive coronary angiography for diagnostic and prognostic cardiac assessment.

Noninvasive cardiac imaging has undergone a recent resurgence with the development of new approaches for imaging coronary atherosclerosis. Non-contrast computed tomography (CT) for imaging the extent of coronary artery calcification (CAC) and contrast CT for noninvasive coronary angiography (CTA) are developments with a growing evidence base regarding risk assessment and the diagnosis of obstructive coronary disease. This review discusses the role of CAC for risk assessment of asymptomatic individuals and for the use of coronary CTA in symptomatic patients. By comparison, gated myocardial perfusion scintigraphy (MPS) is a well-established noninvasive imaging modality that is a core element in evaluation of patients with stable chest pain syndromes. Stress MPS is the most commonly used stress imaging technique for patients with suspected or known coronary disease. In contrast to the nascent evidence noted with coronary CTA, MPS has a robust evidence base, including the support of numerous clinical guidelines. We highlight the current evidence supporting the diagnostic accuracy and risk stratification data for MPS for symptomatic patients with known or suspected coronary artery disease. It is likely that assessing the extent of atherosclerosis using CAC or coronary CTA will become an increasing part of mainstream cardiovascular imaging practices. In some patients, further ischemia testing with MPS will be required. Similarly, in some patients referred for MPS, anatomic definition of atherosclerosis using CAC by CT may be appropriate. Thus, this review also provides a synopsis of the available literature on imaging that integrates both CT and MPS in combined strategies for the assessment of atherosclerotic and obstructive coronary disease burden. We also propose possible risk-based strategies through which imaging might be used to identifying candidates for more intensive prevention and risk factor modification strategies as well as those who would benefit from referral to coronary angiography and revascularization.

Rapid assessment of left ventricular segmental wall motion, ejection fraction, and volumes with single breath-hold, multi-slice TrueFISP MR imaging.

BACKGROUND AND OBJECTIVE: To reduce imaging time and complexity, we sought to determine whether single breath-hold, multi-slice TrueFISP (SB-MST) magnetic resonance imaging (MRI) method is comparable to standard multi-breath-hold, multi-slice TrueFISP (MB-MST) for assessment of left ventricular (LV) wall motion abnormality (WMA), volumes, and ejection fraction (EF). METHODS AND RESULTS: We studied 62 patients having cardiac MRI at 1.5-Tesla. After acquiring standard MB-MST (one slice per breath-hold), SB-MST was performed, acquiring 3 short- and 2 long-axis views over only 20 heartbeats. Using both techniques, wall motion was scored using a 6-point, 17-segment LV model for all scans (62 patients x 2 techniques/patient = 124 scans) on two separate occasions. Separately, EF and ventricular volumes were evaluated using both MB-MST and SB-MST. For all analyses, MB-MST was considered the standard against which SB-MST was compared. Twenty-six of 62 patients exhibited at least one segmental WMA by MB-MST. Exact agreement for wall motion was found in 965/1054 segments (92%, kappa = 0.74, p < 0.001), and agreement was within 1 score point in 1010/1054 segments (96%). Considering a score >1 abnormal, exact agreement for presence of WMA was found in 131/193 segments (68%) abnormal by MB-MST and for absence of WMA in 838/861 segments (97%) normal by MB-MST. Agreement within 1 score point occurred in 167/193 abnormal (87%) and in 843/861 normal segments (98%). There were no significant differences in agreement between first and second read of the data. Variability of SB-MST on read one versus read two was small (5%, 996/1054 segments read identically, p = ns) and statistically identical to variability of MB-MST on read one versus read two (4%, 1007/1054 segments read identically, p = ns). For end-diastolic volumes, end-systolic volumes, and EF using SB-MST compared to MB-MST, mean differences were 9 +/- 15 ml, 6 +/- 12 ml, and 2 +/- 5%, and correlations were r = 0.97, 0.98 and 0.95, respectively. CONCLUSION: SB-MST accurately assesses wall motion, volumes and EF. This approach may serve as a screening exam for assessment of WMA and, under select circumstances, may substitute for standard multi-breath-hold method in situations requiring rapid accurate assessments of LV function.

Roles of nuclear cardiology, cardiac computed tomography, and cardiac magnetic resonance: assessment of patients with suspected coronary artery disease.

Noninvasive cardiac imaging is now central to the diagnosis and management of patients with known or suspected chronic coronary artery disease (CAD). Although rest echocardiography has become the most common of the techniques, nuclear cardiology and more recently cardiac computed tomography (CCT) and cardiac magnetic resonance (CMR) play important roles in this regard. This review examines the current applications and interactions of noninvasive cardiac imaging approaches for the assessment of patients with suspected CAD. In addition to considering the strengths and weaknesses of each technique, this review attempts to provide a guide to the selection of a test (or tests) that is based on the question being asked and the ability of each test to answer this question. In patients with suspected CAD, the pretest likelihood of disease, a clinical assessment, becomes the most important determinant of the initial test. If the likelihood is very low, no testing is needed. However, if the likelihood is low, recent data suggest that assessment of early atherosclerosis is likely to be the most useful and cost-effective test. In patients who have an intermediate likelihood of CAD, nuclear cardiology with myocardial perfusion SPECT (MPS) becomes highly valuable; however, coronary CT angiography (CTA), with fast 16-slice or greater scanners, may emerge as the initial test of choice. MPS would then be used if the CTA is inconclusive or if there is a need to assess the functional significance of a stenosis defined by CTA. Coronary CTA, however, is not yet widely available and is limited in patients with dense coronary calcification. In older patients with a high likelihood of CAD, MPS may be the initial test of choice, since a high proportion of these patients have too much coronary calcium to allow accurate assessment of the presence of coronary stenoses. PET/CT or SPECT/CT could emerge as important modalities combining the advantages of each modality. While CMR has great promise as a radiation-free and contrast-free "one-stop" shop, it currently lags behind CTA for noninvasive coronary angiography. Nonetheless, CMR clearly has the potential for this application and has already emerged as a highly effective method for assessing ventricular function, myocardial mass, and myocardial viability, and there is increasing use of this approach for clinical rest and stress perfusion measurements. CMR is particularly valuable in distinguishing ischemic from nonischemic cardiomyopathy. While CT and CMR are likely to grow considerably in diagnostic evaluation over the next several years, MPS and PET will continue to be very valuable techniques for this purpose.

Functional assessment of myoblast transplantation for cardiac repair with magnetic resonance imaging.

BACKGROUND: Contraction of transplanted myoblasts and their effects on function and remodeling after myocardial infarction remain controversial. AIM: We used magnetic resonance imaging (MRI) to study wall thickening and left ventricular (LV) function and geometry after myoblast transplantation. METHODS AND RESULTS: Three weeks after cryo-infarction rabbits were randomized to receive an injection of approximately 2 x 10(8) myoblasts (n=8) or medium (n=9) into the scar. Cine MRI and contrast enhanced (ce) MRI images were acquired before injection (baseline) and 4 weeks later (endpoint). Regional wall thickening was measured at the site of transmural hyperenhancement. In the control group, regional wall thickening decreased to -15.3+/-8.6% at baseline, which further decreased to -18.3+/-5.7% at endpoint. Further, end-diastolic volume increased from 3.96+/-0.27 to 5.00+/-0.46 ml and end-systolic volume from 2.23+/-0.19 to 2.96+/-0.30 ml (both P<0.05 vs. baseline), which was accompanied by increased LV wall volumes (P<0.05 vs. baseline). In contrast, myoblast transplantation increased regional wall thickening from -11.9+/-15.9% at baseline to 26.9+/-17.0% (P<0.05 vs. control), which resulted in significantly improved two-dimensional ejection fractions at the infarct level and prevented the increase in end-diastolic and end-systolic volumes and wall volume. CONCLUSION: Intracardiac myoblast transplantation after myocardial infarction improves regional wall thickening and prevents progressive left ventricular remodeling.

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.