Utility of Cardiovascular Magnetic Resonance in Identifying Substrate for Malignant Ventricular Arrhythmias

OBJECTIVES: Sudden cardiac death (SCD) and sustained monomorphic ventricular tachycardia (SMVT) are frequently associated with prior or acute myocardial injury. Cardiovascular magnetic resonance (CMR) provides morphological, functional, and tissue characterization in a single setting. We sought to evaluate the diagnostic yield of CMR-based imaging versus non-CMR-based imaging in patients with resuscitated SCD or SMVT.

METHODS: Eighty-two patients with resuscitated SCD or SMVT underwent routine non-CMR imaging, followed by a CMR protocol with comprehensive tissue characterization. Clinical reports of non-CMR imaging studies were blindly adjudicated and used to assign each patient to 1 of 7 diagnostic categories. CMR imaging was blindly interpreted using a standardized algorithm used to assign a patient diagnosis category in a similar fashion. The diagnostic yield of CMR-based and non-CMR-based imaging, as well as the impact of the former on diagnosis reclassification, was established.

RESULTS: Relevant myocardial disease was identified in 51% of patients using non-CMR-based imaging and in 74% using CMR-based imaging (P=0.002). Forty-one patients (50%) were reassigned to a new or alternate diagnosis using CMR-based imaging, including 15 (18%) with unsuspected acute myocardial injury. Twenty patients (24%) had no abnormality by non-CMR imaging but showed clinically relevant myocardial disease by CMR imaging.

CONCLUSIONS: CMR-based imaging provides a robust diagnostic yield in patients presenting with resuscitated SCD or SMVT and incrementally identifies clinically unsuspected acute myocardial injury. When compared with non-CMR-based imaging, a new or alternate myocardial disease process may be identified in half of these patients.

PMID: 22038987

Patient Management After Noninvasive Cardiac Imaging – Results From SPARC (Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles in Coronary Artery Disease)

OBJECTIVES: This study examined short-term cardiac catheterization rates and medication changes after cardiac imaging. Noninvasive cardiac imaging is widely used in coronary artery disease, but its effects on subsequent patient management are unclear.

METHODS: We assessed the 90-day post-test rates of catheterization and medication changes in a prospective registry of 1,703 patients without a documented history of coronary artery disease and an intermediate to high likelihood of coronary artery disease undergoing cardiac single-photon emission computed tomography, positron emission tomography, or 64-slice coronary computed tomography angiography.

RESULTS: Baseline medication use was relatively infrequent. At 90 days, 9.6% of patients underwent catheterization. The rates of catheterization and medication changes increased in proportion to test abnormality findings. Among patients with the most severe test result findings, 38% to 61% were not referred to catheterization, 20% to 30% were not receiving aspirin, 35% to 44% were not receiving a beta-blocker, and 20% to 25% were not receiving a lipid-lowering agent at 90 days after the index test. Risk-adjusted analyses revealed that compared with stress single-photon emission computed tomography or positron emission tomography, changes in aspirin and lipid-lowering agent use was greater after computed tomography angiography, as was the 90-day catheterization referral rate in the setting of normal/nonobstructive and mildly abnormal test results.

CONCLUSIONS: Overall, noninvasive testing had only a modest impact on clinical management of patients referred for clinical testing. Although post-imaging use of cardiac catheterization and medical therapy increased in proportion to the degree of abnormality findings, the frequency of catheterization and medication change suggests possible undertreatment of higher risk patients. Patients were more likely to undergo cardiac catheterization after computed tomography angiography than after single-photon emission computed tomography or positron emission tomography after normal/nonobstructive and mildly abnormal study findings.

PMID:

Reference Values for Normal Pulmonary Artery Dimensions by Noncontrast Cardiac Computed Tomography: The Framingham Heart Study

OBJECTIVES: Main pulmonary artery diameter (mPA) and ratio of mPA to ascending aorta diameter (ratio PA) derived from chest CT are commonly reported in clinical practice. We determined the age- and sex-specific distribution and normal reference values for mPA and ratio PA by CT in an asymptomatic community-based population.

METHODS: In 3171 men and women (mean age, 51±10 years; 51% men) from the Framingham Heart Study, a noncontrast, ECG-gated, 8-slice cardiac multidetector CT was performed. We measured the mPA and transverse axial diameter of the ascending aorta at the level of the bifurcation of the right pulmonary artery and calculated the ratio PA. We defined the healthy referent cohort (n=706) as those without obesity, hypertension, current and past smokers, chronic obstructive pulmonary disease, history of pulmonary embolism, diabetics, cardiovascular disease, and heart valve surgery.

RESULTS: The mean mPA diameter in the overall cohort was 25.1±2.8 mm and mean ratio PA was 0.77±0.09. The sex-specific 90th percentile cutoff value for mPA diameter was 28.9 mm in men and 26.9 mm in women and was associated with increase risk for self-reported dyspnea (adjusted odds ratio, 1.31; P=0.02). The 90th percentile cutoff value for ratio PA of the healthy referent group was 0.91, similar between sexes but decreased with increasing age (range, 0.82-0.94), though not associated with dyspnea.

CONCLUSIONS: For simplicity, we established 29 mm in men and 27 mm in women as sex-specific normative reference values for mPA and 0.9 for ratio PA.

PMID: 22178898

Using Stress Testing to Guide Primary Prevention of Coronary Heart Disease Among Intermediate-Risk Patients A Cost-Effectiveness Analysis

OBJECTIVES: Noninvasive stress testing might guide the use of aspirin and statins for primary prevention of coronary heart disease, but it is unclear if such a strategy would be cost effective.

METHODS: We compared the status quo, in which the current national use of aspirin and statins was simulated, with 3 other strategies: (1) full implementation of Adult Treatment Panel III guidelines, (2) a treat-all strategy in which all intermediate-risk persons received statins (men and women) and aspirin (men only), and (3) a test-and-treat strategy in which all persons with an intermediate risk of coronary heart disease underwent stress testing and those with a positive test were treated with high-intensity statins (men and women) and aspirin (men only). Healthcare costs, coronary heart disease events, and quality-adjusted life years from 2011 to 2040 were projected.

RESULTS: Under a variety of assumptions, the treat-all strategy was the most effective and least expensive strategy. Stress electrocardiography was more effective and less expensive than other test-and-treat strategies, but it was less expensive than treat all only if statin cost exceeded $3.16/pill or if testing increased adherence from75%. However, stress electrocardiography could be cost effective in persons initially nonadherent to the treat-all strategy if it raised their adherence to 5% and cost saving if it raised their adherence to 13%.

CONCLUSIONS: When generic high-potency statins are available, noninvasive cardiac stress testing to target preventive medications is not cost effective unless it substantially improves adherence.

PMID: 22144567

Pulmonary Hypertension: How the Radiologist Can Help

Pulmonary hypertension is defined as an abnormal elevation of pressure in pulmonary circulation, with a mean pulmonary arterial pressure higher than 25 mmHg, regardless of the underlying mechanism. The clinical classification system for pulmonary hypertension was updated at the fourth World Symposium on Pulmonary Hypertension in Dana Point, California, in 2008. In patients with suspected pulmonary hypertension, the diagnostic approach includes four stages: suspicion, detection, classification, and functional evaluation. It is crucial to understand the advantages and disadvantages of the different imaging tools available for the diagnostic work-up and follow-up of patients with pulmonary hypertension. Many conditions that cause pulmonary hypertension have suggestive findings at multidetector computed tomography or magnetic resonance imaging; some causes may be surgically treatable, whereas others may demonstrate adverse reactions to vasodilator therapies used during the course of treatment. Therefore, the radiologist plays an important role in evaluating patients with this disease.

PMID: 22236891

Assessment of Valvular Calcification and Inflammation by Positron Emission Tomography in Patients With Aortic Stenosis

OBJECTIVES: The pathophysiology of aortic stenosis is incompletely understood and the relative contributions of valvular calcification and inflammation to disease progression are unknown.

METHODS: Patients with aortic sclerosis and mild, moderate and severe stenosis were prospectively compared to age and sex-matched control subjects. Aortic valve severity was determined by echocardiography. Calcification and inflammation in the aortic valve were assessed by sodium 18-fluoride (18F-NaF) and 18-fluorodeoxyglucose (18F-FDG) uptake using positron emission tomography. One hundred and twenty one subjects (20 controls; 20 aortic sclerosis; 25 mild, 33 moderate and 23 severe aortic stenosis) were administered both 18F-NaF and 18F-FDG.

RESULTS: Quantification of tracer uptake within the valve demonstrated excellent inter-observer repeatability with no fixed or proportional biases and limits of agreement of ±0.21 (18F-NaF) and ±0.13 (18F-FDG) for maximum tissue-to-background ratios (TBR). Activity of both tracers was higher in patients with aortic stenosis than control subjects (18F-NaF:2.87±0.82 vs 1.55±0.17; 18F-FDG: 1.58±0.21 vs 1.30±0.13; both P1.97) and 35% increased 18F-FDG (>1.63) uptake. A weak correlation between the activities of these tracers was observed (r(2)= 0.174, P

CONCLUSIONS: Positron emission tomography is a novel, feasible and repeatable approach to thee valuation of valvular calcification and inflammation in patients with aortic stenosis. The frequency and magnitude of increased tracer activity correlates with disease severity, and is strongest for 18F-NaF.

PMID: 22090163

Prognostic Importance of Late Gadolinium Enhancement Cardiovascular Magnetic Resonance in Cardiomyopathy

Cardiovascular magnetic resonance has revolutionised the diagnosis of cardiomyopathy, particularly through the use of late gadolinium enhancement imaging which provides the unique opportunity to assess myocardial fibrosis in vivo. More recently, the prognostic capability of cardiovascular magnetic resonance to predict outcomes has been assessed. Traditional risk markers do not at present adequately predict outcomes in either dilated cardiomyopathy or hypertrophic cardiomyopathy, which are the two most common causes of primary heart muscle disease. Many of these existing markers reflect underlying disease severity. Given the important role fibrosis is thought to play in the pathogenesis and sequelae of these cardiomyopathies, the presence and amount of fibrosis has been proposed as a potential novel risk factor for adverse events. This paper reviews the evidence for late gadolinium enhancement as a prognostic marker in dilated and hypertrophic cardiomyopathy and highlights the challenges ahead.

PMID: 22128204

Improved Detection of Myocardial Involvement in Acute Inflammatory Cardiomyopathies Using T2 Mapping

OBJECTIVES: T2-weighted cardiac magnetic resonance (CMR) is useful in diagnosing acute inflammatory myocardial diseases such as myocarditis and tako-tsubo cardiomyopathy (TTCM). We hypothesized that quantitative T2 mapping could better delineate myocardial involvement in these disorders vs. T2-weighted imaging.

METHODS: Thirty patients with suspected myocarditis or TTCM referred for CMR who met established diagnostic criteria underwent myocardial T2 mapping. T2 values were averaged in involved and remote myocardial segments, both defined by a reviewer blinded to T2 data.

RESULTS: In myocarditis, T2 was 65.2±3.2ms in the involved myocardium vs. 53.5±2.1 in remote myocardium (p0.05 for all). T2 maps provided diagnostic data even in patients with difficulty breath-holding. A T2 cutoff of 59ms identified areas of myocardial involvement with sensitivity and specificity of 94% and 97%, respectively. T2 mapping revealed regions of abnormal T2 beyond those identified by wall motion abnormalities or LGE-positivity. Conventional T2-weighted short tau inversion recovery (T2W-STIR) images were uninterpretable in 7 patients due to artifact and unremarkable in 2 who had elevated T2 values. T2-prepared steady state free precession (T2p-SSFP) images showed areas of signal hyperintensity in only17/30 patients.

CONCLUSIONS: Quantitative T2 mapping reliably identifies myocardial involvement in patients with myocarditis and TTCM. T2 mapping delineated greater extent of myocardial disease in both conditions compared to that identified by wall motion abnormalities, T2W-STIR, T2p-SSFP or LGE. Quantitative T2 mapping warrants consideration as a robust technique to identify myocardial injury in patients with acute myocarditis or TTCM.

PMID: 22038988

Prevalence and Severity of Coronary Artery Disease and Adverse Events Among Symptomatic Patients With Coronary Artery Calcification Scores of Zero Undergoing Coronary Computed Tomography Angiography: Results From the CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter) Registry

OBJECTIVES: The purpose of this study was to describe the prevalence and severity of coronary artery disease (CAD) in relation to prognosis in symptomatic patients without coronary artery calcification (CAC) undergoing coronary computed tomography angiography (CCTA). The frequency and clinical relevance of CAD in patients without CAC are unclear.

METHODS: We identified 10,037 symptomatic patients without CAD who underwent concomitant CCTA and CAC scoring. CAD was assessed as

RESULTS: Mean age was 57 years, 56% were men, and 51% had a CAC score of 0. Among patients with a CAC score of 0, 84% had no CAD, 13% had nonobstructive stenosis, and 3.5% had ≥50% stenosis (1.4% had ≥70% stenosis) on CCTA. A CAC score >0 had a sensitivity, specificity, and negative and positive predictive values for stenosis ≥50% of 89%, 59%, 96%, and 29%, respectively. During a median of 2.1 years, there was no difference in mortality among patients with a CAC score of 0 irrespective of obstructive CAD. Among 8,907 patients with follow-up for the composite endpoint, 3.9% with a CAC score of 0 and ≥50% stenosis experienced an event (hazard ratio: 5.7; 95% confidence interval: 2.5 to 13.1; p < 0.001) compared with 0.8% of patients with a CAC score of 0 and no obstructive CAD. Receiver-operator characteristic curve analysis demonstrated that the CAC score did not add incremental prognostic information compared with CAD extent on CCTA for the composite endpoint (CCTA area under the curve = 0.825; CAC + CCTA area under the curve = 0.826; p = 0.84).

CONCLUSIONS: In symptomatic patients with a CAC score of 0, obstructive CAD is possible and is associated with increased cardiovascular events. CAC scoring did not add incremental prognostic information to CCTA.

PMID:

Right Ventricular Injury in ST-Elevation Myocardial Infarction: Risk Stratification by Visualization of Wall Motion, Edema and Delayed Enhancement Cardiac Magnetic Resonance

OBJECTIVES: Patients with right ventricular injury (RVI) complicating ST-elevation myocardial infarction (STEMI) suffer from impaired prognosis, but it is unclear which patients are at risk of developing RVI. Cardiac magnetic resonance (CMR) can identify these patients and might add important information on risk stratification, prognosis and treatment. Aims were to determine the predictors and the prognostic significance of RVI assessed by wall motion abnormalities, edema, myocardial-salvage-index (MSI) and delayed enhancement (DE) in acute reperfused STEMI.

METHODS: We studied 450 patients 1-4 days after primary angioplasty in STEMI. T2-weighted and DE CMR was used for visualizing edema and scar to calculate MSI. Cine-imaging was performed to assess wall motion abnormalities, which, in combination with edema, were considered diagnostic for RVI. Patients with RVI were compared to matched patients with isolated left ventricular (LV) infarction. The primary endpoint was the occurrence of a major adverse cardiac event (MACE): a composite of death, reinfarction and congestive heart failure after a median follow-up period of 20.9 months.

RESULTS: RVI was present in 69 patients and 41/69 showed myocardial necrosis. In a multivariable stepwise forward logistic regression analysis a high RV myocardial mass (Odds-Ratio 2.06, 95% Confidence-Interval 1.18-3.58, p=0.012) and a low TIMI-flow pre angioplasty (Odds-Ratio 0.50, 95% CI 0.32-0.76, p=0.011) were associated with RVI. Cox regression analysis revealed RVI as the most statistically significant predictor of time to MACE (Hazard-Ratio 3.36, 95% CI 1.99-5.66, p

CONCLUSIONS: RVI detected by CMR is a strong and independent predictor of clinical outcome after acute reperfused STEMI.

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2011 ACCF/AHA Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy: A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines

Practice guidelines are developed through a rigorous methodological approach  that mandates the review and consideration of the available medical literature.  Practice guidelines define the role of specific diagnostic and therapeutic  modalities, including noninvasive and invasive procedures, in the diagnosis and  management of patients with various cardiovascular diseases. These  evidence-based guidelines are intended to assist physicians in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, or prevention of specific diseases or conditions. They attempt to define practices that meet the needs of most patients in most circumstances by categorizing the recommendations into a classification system. The development of practice guidelines are the domain of the ACCF/AHA Task Force on Practice Guidelines and are published in JACC and Circulation.

PMID: 22068435

Radiography of Cardiac Conduction Devices: A Comprehensive Review

Radiology plays a crucial role in initial assessment and follow-up of cardiac conduction devices (CCDs). At least 1 million patients in the United States have permanent CCDs, which comprise pacemakers and implantable cardioverter-defibrillators. Chest radiography is unique because it is the only imaging modality that allows evaluation of the physical integrity of CCD leads. As a result, a basic knowledge of the normal and abnormal radiographic appearances of these devices and their various components is important. Radiologists should have a working knowledge of CCD anatomy as well as appropriate positioning and appearance of CCD leads and generators. Acute complications of CCD implantation include dysrhythmia, pneumothorax, perforation of the heart muscle or a vein, heart valve damage, lead damage, inadequate seating of the terminal connector pin, and presence of an air pocket. Chronic complications include twiddler syndrome, lead fracture, damage to the lead insulation, and lead displacement. Radiologists play an important role in management of patients with CCDs by providing vital information about the device, starting immediately after implantation and continuing throughout its duration in the patient. To fulfill this role, radiologists must have a firm understanding of CCDs and their evolving technology.

PMID: 21997988

Cardiac Magnetic Resonance Imaging Pericardial Late Gadolinium Enhancement and Elevated Inflammatory Markers Can Predict the Reversibility of Constrictive Pericarditis After Antiinflammatory Medical Therapy

OBJECTIVES: Constrictive pericarditis (CP) is a disabling disease, and usually requires pericardiectomy to relieve heart failure. Reversible CP has been described, but there is no known method to predict the reversibility. Pericardial inflammation may be a marker for reversibility. As a pilot study, we assessed whether cardiac magnetic resonance imaging pericardial late gadolinium enhancement (LGE) and inflammatory biomarkers could predict the reversibility of CP after anti-inflammatory therapy.

METHODS: Twenty-nine CP patients received anti-inflammatory medications after cardiac magnetic resonance imaging. Fourteen patients had resolution of CP, whereas 15 patients had persistent CP after 13 months of follow-up. Baseline LGE pericardial thickness was greater in the group with reversible CP than in the persistent CP group (4±1 versus 2±1 mm, P=0.001). Qualitative intensity of pericardial LGE was moderate or severe in 93% of the group with reversible CP and in 33% of the persistent CP group (P=0.002).

RESULTS: Cardiac magnetic resonance imaging LGE pericardial thickness ≥3 mm had 86% sensitivity and 80% specificity to predict CP reversibility. The group with reversible CP also had higher baseline C-reactive protein and erythrocyte sedimentation rate than the persistent CP group (59±52 versus 12±14 mg/L, P=0.04 and 49±25 versus 15±16 mm/h, P=0.04, respectively). Anti-inflammatory therapy was associated with a reduction in C-reactive protein, erythrocyte sedimentation rate, and pericardial LGE in the group with reversible CP but not in the persistent CP group.

CONCLUSIONS: Reversible CP was associated with pericardial and systemic inflammation. Anti-inflammatory therapy was associated with a reduction in pericardial and systemic inflammation and LGE pericardial thickness, with resolution of CP physiology and symptoms. Further studies in a larger number of patients are needed.

PMID: 21969014

Diagnosis of Ischemia-Causing Coronary Stenoses by Noninvasive Fractional Flow Reserve Computed From Coronary Computed Tomographic Angiograms

OBJECTIVES: The aim of this study was to determine the diagnostic performance of a new method for quantifying fractional flow reserve (FFR) with computational fluid dynamics (CFD) applied to coronary computed tomography angiography (CCTA) data in patients with suspected or known coronary artery disease (CAD). Measurement of FFR during invasive coronary angiography is the gold standard for identifying coronary artery lesions that cause ischemia and improves clinical decision-making for revascularization. Computation of FFR from CCTA data (FFRCT) provides a noninvasive method for identifying ischemia-causing stenosis; however, the diagnostic performance of this new method is unknown.

METHODS: Computation of FFR from CCTA data was performed on 159 vessels in 103 patients undergoing CCTA, invasive coronary angiography, and FFR. Independent core laboratories determined FFRCT and CAD stenosis severity by CCTA. Ischemia was defined by an FFRCT and FFR 0.80, and anatomically obstructive CAD was defined as a CCTA with stenosis 50%. Diagnostic performance of FFRCT and CCTA stenosis was assessed with invasive FFR as the reference standard.

RESULTS: Fifty-six percent of patients had 1 vessel with FFR 0.80. On a per-vessel basis, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 84.3%, 87.9%, 82.2%, 73.9%, 92.2%, respectively, for FFRCT and were 58.5%, 91.4%, 39.6%, 46.5%, 88.9%, respectively, for CCTA stenosis. The area under the receiver-operator characteristics curve was 0.90 for FFRCT and 0.75 for CCTA (p = 0.001). The FFRCT and FFR were well correlated (r = 0.717, p < 0.001) with a slight underestimation by FFRCT (0.022 ± 0.116, p = 0.016).

CONCLUSIONS: Noninvasive FFR derived from CCTA is a novel method with high diagnostic performance for the detection and exclusion of coronary lesions that cause ischemia.

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Timing of Cardiovascular MR Imaging After Acute Myocardial Infarction: Effect on Estimates of Infarct Characteristics and Prediction of Late Ventricular Remodeling

OBJECTIVES: To define the evolution of infarct characteristics with cardiovascular magnetic resonance (MR) imaging and to assess which of the cardiovascular MR data acquired at day 2 or at 1 week after acute myocardial infarction (AMI), is the stronger predictor of infarct size and left ventricular (LV) function measured at 3 months.

METHODS: The study protocol was reviewed and approved by the local research ethics committee, and written informed consent was obtained. Forty-eight patients with reperfused AMI underwent cine, T2-weighted, and late gadolinium enhancement cardiovascular MR imaging at days 2, 7, 30, and 90 after index presentation. Continuous data between times were compared by using paired t tests or one-way analysis of variance. Multiple linear regression analyses were used to predict linear end points.

RESULTS: Infarct size and extent of myocardial edema decreased significantly between day 2 and 1 week: Mean scar as a percentage of LV mass and standard deviation (SD), respectively, were 27.2 and 13.9 versus 21.6 and 14.1 (P < .001), and myocardial edema as a percentage of LV mass and SD, respectively, were 37.9 and 15.2 versus 32.3 and 14.3 (P = .003). These changes were accompanied by a significant improvement in LV ejection fraction (LVEF): Mean percentage of LVEF and SD, respectively, were 41.7 and 9.6 versus 44.6 and 10.1 (P < .001). When comparing data acquired at day 2 and 1 week, only cardiovascular MR data acquired at 1 week were independent predictors of LVEF and infarct size at 3 months.

CONCLUSIONS: LVEF, infarct size, and extent of myocardial edema changed significantly during the 1st week after AMI. Overall, cardiovascular MR measurements acquired after 1 week have greater predictive value for infarct size and LV function at 3 months than data acquired at day 2.

PMID: 21828188