Assessment of Left Ventricular Regional Wall Motion and Ejection Fraction With Low-Radiation Dose Helical Dual-Source CT: Comparison to Two-Dimensional Echocardiography

OBJECTIVES: 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. 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.

PMID: 21367686

Diagnostic Accuracy of Echocardiography for Pulmonary Hypertension: A Systematic Review and Meta-Analysis

OBJECTIVES: Right heart catheterization is the gold standard for the diagnosis of pulmonary hypertension. However, echocardiography is frequently used to screen for this disease and monitor progression over time because it is noninvasive, widely available, and relatively inexpensive. The objective of our study was to perform a systematic review and quantitative meta-analysis to determine the correlation of pulmonary pressures obtained via echocardiography versus right heart catheterization and to determine the diagnostic accuracy of echocardiography for pulmonary hypertension.

METHODS: MEDLINE, EMBASE, PapersFirst, and the Cochrane collaboration and the Cochrane Register of controlled trials were searched and were inclusive as of February 2010. Studies were only included if a correlation coefficient or the absolute number of true-positive, false-negative, true-negative, and false-positive observations were available, and the “reference standards” were described clearly. Quality was assessed with the Quality Assessment for Diagnostic Accuracy Studies (QUADAS). A random effects model was used to obtain a summary correlation coefficient and the bivariate model for diagnostic meta-analysis was used to obtain summary sensitivity and specificity values.

RESULTS: Twenty-nine studies were included in the meta-analysis. The summary correlation coefficient between systolic pulmonary arterial pressure estimated from echocardiography versus measured by right heart catheterization was 0.70 (95% CI: 0.67-0.73) (n=27). The summary sensitivity and specificity for echocardiography for diagnosing pulmonary hypertension was 83% (95% CI: 73-90) and 72% (95% CI: 53-85) (n=12), respectively. The summary diagnostic odds ratio was 13 (95% CI: 5-31).

CONCLUSIONS: Echocardiography is a useful and noninvasive modality for measuring pulmonary pressures and for screening/diagnosing pulmonary hypertension.

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A New Method for Quantification of Left Ventricular Systolic Function Using a Corrected Ejection Fraction

OBJECTIVES: Left ventricular ejection fraction (EF) is a suboptimal measure of ventricular function. Recent mathematical modelling of left ventricular contraction has shown that the EF is determined by both myocardial shortening (strain) and by end-diastolic wall thickness. Increasing end-diastolic wall thickness resulted in augmented radial wall thickening. This may result in a significant ‘overestimation’ of ventricular systolic function as assessed by the EF. This study proposes a new measure of ventricular systolic function, the corrected EF (EF(c)) to allow for the presence of concentric left ventricular hypertrophy (LVH).

METHODS: The study uses a new two-layer, three-dimensional mathematical model of ventricular contraction. Changes in end-diastolic wall thickness in addition to long-axis and mid-wall circumferential strain were modelled.

RESULTS: Iso-strain lines were obtained where myocardial shortening (strain) is constant; EF increases with increasing end-diastolic wall thickness. The corrected EF is determined by following the iso-strain lines to the equivalent EF in the absence of hypertrophy (e.g. 9 mm thickness). For example, an individual with a mean end-diastolic wall thickness of 20 mm and measured EF of 60% has a corrected EF (EF(c)) of 37%.

CONCLUSIONS: The study shows that the EF is determined by absolute wall thickening and provides a nomogram for comparing EF when LVH is present. The EF(c) is a potential new measure of left ventricular systolic function. Its possible role will need validating in mortality trials.

PMID: 21216767

Transcatheter Approaches to Non-Valvar Structural Heart Disease

With advancement in transcatheter technology, numerous non-congenital structural heart lesions previously untreated, or treated with surgery are now amenable to transcatheter therapy. These therapies have centered on transcatheter valve replacement, however, other lesions are increasingly treated via the percutaneous approach. These procedures include patent foramen ovale closure, left atrial appendage occlusion, closure of post-infarct ventricular septal defects, occlusion of ruptured sinus of Valsalva aneurysm and treatment of paravalvar leaks. This review will outline indications for and approach to each of these procedures in the context of the current literature base with emphasis on pre- and intra-procedural imaging modalities.

PMID: 21331612

Comparison of the Structure of the Aortic Valve and Ascending Aorta in Adults Having Aortic Valve Replacement for Aortic Stenosis Versus for Pure Aortic Regurgitation and Resection of the Ascending Aorta for Aneurysm

OBJECTIVES: There is debate concerning whether an aneurysmal ascending aorta should be replaced when associated with a dysfunctioning aortic valve that is to be replaced.

METHODS: To examine this issue, we divided the patients by type of aortic valve dysfunction—either aortic stenosis (AS) or pure aortic regurgitation (AR)—something not previously undertaken.

RESULTS: Of 122 patients with ascending aortic aneurysm (unassociated with aortitis or acute dissection), the aortic valve was congenitally malformed (unicuspid or bicuspid) in 58 (98%) of the 59 AS patients, and in 38 (60%) of the 63 pure AR patients. Ascending aortic medial elastic fiber loss (EFL) (graded 0 to 4+) was zero or 1+ in 53 (90%) of the AS patients, in 20 (53%) of the 38 AR patients with bicuspid valves, and in all 12 AR patients with tricuspid valves unassociated with the Marfan syndrome. An unadjusted analysis showed that, among the 96 patients with congenitally malformed valves, the 38 AR patients had a significantly higher likelihood of 2+ to 4+ EFL than the 58 AS patients (crude odds ratio: 8.78; 95% confidence interval: 2.95, 28.13).

CONCLUSONS: These data strongly suggest that the type of aortic valve dysfunction—AS versus pure AR—is very helpful in predicting loss of aortic medial elastic fibers in patients with ascending aortic aneurysms and aortic valve disease.

PMID: 21321157

Paradoxical Low Flow And/Or Low Gradient Severe Aortic Stenosis Despite Preserved Left Ventricular Ejection Fraction: Implications for Diagnosis and Treatment

Paradoxical low flow, low gradient, severe aortic stenosis (AS) despite preserved ejection fraction is a recently described clinical entity whereby patients with severe AS on the basis of aortic valve area have a lower than expected gradient in relation to generally accepted values. This mode of presentation of severe AS is relatively frequent (up to 35% of cases) and such patients have a cluster of findings, indicating that they are at a more advanced stage of their disease and have a poorer prognosis if treated medically rather than surgically. Yet, a majority of these patients do not undergo surgery likely due to the fact that the reduced gradient is conducive to an underestimation of the severity of the disease and/or of symptoms. The purpose of this article is to review and further analyse the distinguishing characteristics of this entity and to present its implications with regards to currently accepted guidelines for AS severity.

PMID: 19737801

Transcatheter Aortic Valve Implantation in Aortic Stenosis: The Role of Echocardiography

Aortic stenosis is becoming an increasing health care problem as the population ages. Surgical aortic valve replacement remains the gold standard but is associated with high mortality and morbidity rates in elderly patients and those with multiple comorbidities. The authors explore transcatheter aortic valve implantation as an attractive alternative therapy in this high-risk population and outline its limitations and future directions, with a special emphasis on the role of echocardiography.

PMID: 21126855

Occurrence of Atrial Fibrillation During Dobutamine Stress Echocardiography: Incidence, Risk Factors, and Outcomes

OBJECTIVES: The reported incidence of atrial fibrillation (AF) occurring during dobutamine stress echocardiography (DSE) ranges from 0.5% to 4%. The aim of this study was to characterize the incidence, risk factors, and outcomes of AF precipitated during DSE.

METHODS: The clinical and echocardiographic data of consecutive patients over a 50-month period who were in sinus rhythm and underwent DSE were retrospectively reviewed.

RESULTS: A total of 11,806 consecutive patients underwent DSE and met all inclusion criteria. AF developed during DSE in 122 patients (1%), 71 of whom had histories of AF. The duration of AF was <1 hour in 74 patients (61%) and <24 hours in 117 patients (96%). Of the 47 patients who were still in AF when dismissed from the echocardiography laboratory, 21 had outpatient follow-up within 24 hours, eight were already inpatients, and 18 were triaged to the emergency department or hospital. Spontaneous cardioversion occurred in 114 patients (93%). There were no reported complications. The clinical characteristic most strongly associated with the development of AF during DSE was a history of AF (odds ratio, 18.4 if no history of congestive heart failure; P < .001). The presence or extent of stress-induced myocardial ischemia was not predictive of the development of AF.

CONCLUSIONS: AF is an infrequent complication of DSE. Most patients return to sinus rhythm spontaneously within 1 hour. Patients with persistent AF can be safely dismissed from the echocardiography laboratory to have outpatient follow-up within 24 hours unless they have suboptimal heart rate control, hypotension, significant symptoms, or markedly abnormal findings on DSE.

PMID: 21172598

Systolic and Diastolic Myocardial Mechanics in Patients With Cardiac Disease and Preserved Ejection Fraction: Impact of Left Ventricular Filling Pressure

OBJECTIVES: There are few data on the impact of left ventricular (LV) filling pressure on systolic and diastolic myocardial mechanics in patients with cardiac disease and preserved LV ejection fraction (LVEF) (≥50%).

METHODS: Patients referred for cardiac catheterization underwent comprehensive echocardiography within 20 minutes of catheterization. Strain and strain rate in longitudinal, radial, and circumferential directions and torsion were measured in systole and diastole. LV preatrial contraction pressure (pre-A) was measured and averaged over 10 cardiac cycles.

RESULTS: Sixty patients were studied (mean age, 55.3 ± 8.9 years). The 30 patients with LV pre-A ≥ 15 mm Hg had significantly lower longitudinal systolic strain and radial, circumferential, and torsional systolic strain rates than the 30 patients with LV pre-A < 15 mm Hg (P < .05 for all). Similar findings were seen for diastolic variables. There were significant correlations between several systolic and diastolic variables in multiple directions and LV pre-A. On multivariate analysis, the independent predictors of systolic and diastolic speckle-tracking parameters included LVEF and LV pre-A, depending on the specific parameter analyzed.

CONCLUSIONS: In patients with preserved LVEF and cardiac disease, several systolic and diastolic myocardial mechanical parameters significantly correlate with LV filling pressure. These data highlight the notion that patients with preserved LVEF and elevated LV filling pressures have significant abnormalities in systolic function as detected by speckle imaging, findings that may challenge the concept of “isolated diastolic dysfunction.” The extent of systolic and diastolic abnormalities in these patients may shed light on the mechanics of heart failure with preserved LVEF.

PMID: 20970305

Standardized Endpoint Definitions for Transcatheter Aortic Valve Implantation Clinical Trials: A Consensus Report from the Valve Academic Research Consortium

PMID:

Measurement of Aortic Valve Calcification Using Multislice Computed Tomography: Correlation With Haemodynamic Severity of Aortic Stenosis and Clinical Implication for Patients With Low Ejection Fraction

OBJECTIVES: Measurement of the degree of aortic valve calcification (AVC) using electron beam computed tomography (EBCT) is an accurate and complementary method to transthoracic echocardiography (TTE) for assessment of the severity of aortic stenosis (AS). Whether threshold values of AVC obtained with EBCT could be extrapolated to multislice computed tomography (MSCT) was unclear and AVC diagnostic value in patients with low ejection fraction (EF) has never been specifically evaluated.

METHODS: Patients with mild to severe AS underwent prospectively within 1 week MSCT and TTE. Severe AS was defined as an aortic valve area (AVA) of less than 1 cm(2). In 179 patients with EF greater than 40% (validation set), the relationship between AVC and AVA was evaluated. The best threshold of AVC for the diagnosis of severe AS was then evaluated in a second subset (testing set) of 49 patients with low EF (<40%). In this subgroup, AS severity was defined based on mean gradient, natural history or dobutamine stress echocardiography.

RESULTS: Correlation between AVC and AVA was good (r=-0.63, p<0.0001). A threshold of 1651 arbitrary units (AU) provided 82% sensitivity, 80% specificity, 88% negative-predictive value and 70% positive-predictive value. In the testing set (patients with low EF), this threshold correctly differentiated patients with severe AS from non-severe AS in all but three cases. These three patients had an AVC score close to the threshold (1206, 1436 and 1797 AU).

CONCLUSIONS: In this large series of patients with a wide range of AS, AVC was shown to be well correlated to AVA and may be a useful adjunct for the evaluation of AS severity especially in difficult cases such as patients with low EF.

PMID: 20720250

Septal Pouch in the Left Atrium and Risk of Ischemic Stroke

OBJECTIVES: We sought to assess the association between the presence of a septal pouch in the left atrium and ischemic stroke. It has been suggested that the presence of a left septal pouch (LSP) may favor the stasis of blood and possibly result in thromboembolic complications. However, the embolic potential of an LSP is not known.

METHODS: The association between an LSP and risk of stroke was assessed using a population-based case-control study design. The presence of an LSP was assessed by transesophageal echocardiography in 187 patients >50 years of age with a first-ever ischemic stroke (96 men, mean age 70.6 ± 9.0 years) and in 157 control subjects matched to patients by age, sex, and race/ethnicity. The association between an LSP and risk of stroke was assessed after adjustment for other stroke risk factors.

RESULTS: Patients with LSPs were younger than control subjects (67.5 ± 9.1 years vs. 69.6 ± 8.8 years; p = 0.046), with a lower prevalence of hypertension (68.0% vs. 80.3%; p = 0.01). There were no differences in the prevalence of LSPs between stroke patients and control subjects (28.9% vs. 29.3%, respectively; p = 0.93). The subgroup of 69 patients (36.9%) with cryptogenic stroke showed a similar prevalence of LSPs (31.9% vs. 29.3%; p = 0.70). Multivariable analysis showed that the presence of an LSP was not associated with ischemic stroke (odds ratio: 1.09; 95% confidence interval: 0.64 to 1.85) or cryptogenic stroke (odds ratio: 1.41; 95% confidence interval: 0.71 to 2.78).

CONCLUSIONS: This study does not demonstrate evidence of the association of the presence of an LSP with ischemic stroke or cryptogenic stroke. The stroke risk associated with LSPs requires further evaluation in the younger stroke populations. The cofactors that may turn an LSP from an innocent bystander to a causative mechanism for stroke remains to be elucidated.

PMID: 21163457

Urban Particulate Matter Air Pollution is Associated With Subclinical Atherosclerosis: Results from the HNR (Heinz Nixdorf Recall) Study

OBJECTIVES: The aim of this study was to investigate the association of long-term residential exposure to fine particles with carotid intima-media thickness (CIMT). Experimental and epidemiological evidence suggest that long-term exposure to air pollution might have a causal role in atherogenesis, but epidemiological findings are still inconsistent. We investigate whether urban particulate matter (PM) air pollution is associated with CIMT, a marker of subclinical atherosclerosis.

METHODS: We used baseline data (2000 to 2003) from the HNR (Heinz Nixdorf Recall) study, a population-based cohort of 4,814 participants, 45 to 75 years of age. We assessed residential long-term exposure to PM with a chemistry transport model and measured distance to high traffic. Multiple linear regression was used to estimate associations of air pollutants and traffic with CIMT, adjusting for each other, city of residence, age, sex, diabetes, and lifestyle variables.

RESULTS: Median CIMT of the 3,380 analyzed participants was 0.66 mm (interquartile range 0.16 mm). An interdecile range increase in PM(2.5) (4.2 μg/m(3)), PM(10) (6.7 μg/m(3)), and distance to high traffic (1,939 m) was associated with a 4.3% (95% confidence interval [CI]: 1.9% to 6.7%), 1.7% (95% CI: -0.7% to 4.1%), and 1.2% (95% CI: -0.2% to 2.6%) increase in CIMT, respectively.

CONCLUSIONS: Our study shows a clear association of long-term exposure to PM(2.5) with atherosclerosis. This finding strengthens the hypothesized role of PM(2.5) as a risk factor for atherogenesis.

PMID: 21087707

Longitudinal and Circumferential Strain Rate, Left Ventricular Remodeling, and Prognosis After Myocardial Infarction

OBJECTIVES: We sought to investigate the clinical prognostic value of longitudinal and circumferential strain (S) and strain rate (SR) in patients after high-risk myocardial infarction (MI). Left ventricular (LV) contractile performance after MI is an important predictor of long-term outcome. Tissue deformation imaging might more closely reflect myocardial contractility than traditional measures of systolic functions.

METHODS: The VALIANT (Valsartan in Acute Myocardial Infarction Trial) Echo study enrolled 603 patients with LV dysfunction, heart failure, or both 5 days after MI. We measured global peak longitudinal S and systolic SR (SRs) from apical 4- and 2-chamber views and global circumferential S and SRs from parasternal short-axis view with speckle tracking software (Velocity Vector Imaging, Siemens, Inc., Mountain View, California). We related global S and SRs to LV remodeling at 20-month follow-up and to clinical outcomes.

RESULTS: Both longitudinal (mean: -5.1 ± 1.6 100/ms) and circumferential SRs (mean: -8.0 ± 2.8 100/ms) were predictive of death or hospital stay for heart failure (hazard ratio: 2.4, 95% confidence interval [CI]: 2.0 to 3.1, p < 0.001; hazard ratio: 1.3, 95% CI: 1.2 to 1.4, p < 0.001, respectively) after adjustment for clinical covariates by Cox proportional hazards, and longitudinal SRs further improved in predicting 18-month survivor on a model based on clinical and standard echocardiographic measures (increase in area under the receiver-operator characteristic curve: 0.13, p = 0.009). With multivariable logistic regression, circumferential SRs, but not longitudinal SRs, was strongly predictive of remodeling (odds ratio: 1.3, 95% CI: 1.1 to 1.4, p < 0.001).

CONCLUSIONS: Both longitudinal and circumferential SRs were independent predictors of outcomes after MI, whereas only circumferential SRs was predictive of remodeling, suggesting that preserved circumferential function might serve to restrain ventricular enlargement after MI.

PMID: 21087709

Assessment of the Aortic Root Using Real-Time 3D Transesophageal Echocardiography

OBJECTIVES: Precise evaluation of the aortic root geometry prior to transcatheter aortic valve implantation is important for procedural success in patients with aortic stenosis (AS). To determine the potential for 3-dimensional transesophageal echocardiography (3DTEE), the aims of the present study were: (1) to assess the accuracy of 3DTEE measurements of the aortic root using multidetector computed tomography (MDCT) as a reference, and (2) to examine whether aortic root geometry differs between patients with and without AS.

METHODS: 3DTEE and contrast-enhanced MDCT were performed in 35 patients. Multiplanar reconstruction was used to measure the left ventricular outflow tract (LVOT) and aortic annulus diameter/area, aortic valve area (AVA), and distances between the annulus and coronary artery ostium. The same 3DTEE measurements were performed in patients with (n=71) and without AS (n=80).

RESULTS: Aortic annular and LVOT areas measured by 3DTEE were slightly but significantly smaller compared with values obtained with MDCT. Both methods revealed that the aortic annulus and LVOT have an oval shape. Aortic annular and LVOT area, AVA and the distances between the aortic annulus and the coronary ostia correlated well between the 2 modalities. Only minor differences in aortic root geometry were observed between patients with AS and those without.

CONCLUSIONS: The geometry of the aortic annulus can be reliably evaluated using 3DTEE as an alternative to MDCT for the assessment of aortic root.

PMID: 21084759