Mark Bowers

Left atrial volume measurement with automated border detection by 3-dimensional echocardiography: comparison with magnetic resonance imaging

ObjectiveLeft atrial size is an important marker for adverse cardiovascular events. There is general consensus that left atrial volume index (LAVI) is the best measurement of size. The current LAVI measurement techniques are laborious. Semi-automated measurement with a 3-dimensional echocardiography (3DE) system may be a practical clinical alternative to measure LAVI, but it has not been adequately evaluated against Magnetic Resonance Imaging (MRI) gold standard. The aim of this study was to compare the accuracy of a commercially available 3D algorithm for measurement of LAVI against LAVI obtained from MRI and Area Length Method (ALM).DesignIn 27 consecutive subjects referred for cardiac MRI (age 54 ± 13 years, 63% male), LAVI was measured using 3 imaging modalities: 3DE, ALM, MRI and the results were correlated. ALM was measured using standard American Society of Echocardiography guidelines. The time required to measure LAVI by 3DE and ALM were compared.ResultsThere was a significant correlation in systolic and diastolic LA volumes and left atrial ejection fraction between 3DE and MRI (r = 0.86 for systole, r = 0.76 for diastole, r = 0.88 for ejection fraction, P < 0.0001 for all). There was also significant correlation of diastolic volumes between 3DE and ALM (r = 0.77, P < 0.0001). The time to obtain LAVI was shorter using 3DE versus ALM (56 ± 8 vs 135 ± 55 seconds, P < 0.0001).ConclusionThree-dimensional echocardiography with semiautomatic border detection is a practical alternative for obtaining the left atrial volume in a time-efficient manner compared to the current standard.

Carotid plaque regression following 6-month statin therapy assessed by 3T cardiovascular magnetic resonance: comparison with ultrasound intima media thickness

BackgroundCardiovascular magnetic resonance (CMR) allows volumetric carotid plaque measurement that has advantage over 2-dimensional ultrasound (US) intima-media thickness (IMT) in evaluating treatment response. We tested the hypothesis that 6-month statin treatment in patients with carotid plaque will lead to plaque regression when measured by 3 Tesla CMR but not by IMT.MethodsTwenty-six subjects (67 ± 2 years, 7 females) with known carotid plaque (> 1.1 mm) and coronary or cerebrovascular atherosclerotic disease underwent 3T CMR (T1, T2, proton density and time of flight sequences) and US at baseline and following 6 months of statin therapy (6 had initiation, 7 had increase and 13 had maintenance of statin dosing). CMR plaque volume (PV) was measured in the region 12 mm below and up to 12 mm above carotid flow divider using software. Mean posterior IMT in the same region was measured. Baseline and 6-month CMR PV and US IMT were compared. Change in lipid rich/necrotic core (LR/NC) and calcification plaque components from CMR were related to change in PV.ResultsLow-density lipoprotein cholesterol decreased (86 ± 6 to 74 ± 4 mg/dL, p = 0.046). CMR PV decreased 5.8 ± 2% (1036 ± 59 to 976 ± 65 mm3, p = 0.018). Mean IMT was unchanged (1.12 ± 0.06 vs. 1.14 ± 0.06 mm, p = NS). Patients with initiation or increase of statins had -8.8 ± 2.8% PV change (p = 0.001) while patients with maintenance of statin dosing had -2.7 ± 3% change in PV (p = NS). There was circumferential heterogeneity in CMR plaque thickness with greatest thickness in the posterior carotid artery, in the region opposite the flow divider. Similarly there was circumferential regional difference in change of plaque thickness with significant plaque regression in the anterior carotid region in region of the flow divider. Change in LR/NC (R = 0.62, p = 0.006) and calcification (R = 0.45, p = 0.03) correlated with PV change.ConclusionsSix month statin therapy in patients with carotid plaque led to reduced plaque volume by 3T CMR, but ultrasound posterior IMT did not show any change. The heterogeneous spatial distribution of plaque and regional differences in magnitude of plaque regression may explain the difference in findings and support volumetric measurement of plaque. 3T CMR has potential advantage over ultrasound IMT to assess treatment response in individuals and may allow reduced sample size, duration and cost of clinical trials of plaque regression.

Left Ventricular Ejection Time on Echocardiography Predicts Long-Term Mortality in Light Chain Amyloidosis

OBJECTIVE Light chain amyloidosis (AL) is associated with high mortality. The aim was to identify echocardiographic parameters that predict AL long-term mortality. METHODS Forty-two subjects with biopsy-proven AL (43% were female; aged 61 +/- 12 years) underwent echocardiography and were followed 29 +/- 16 months (median 29.4 months). Standard echocardiographic and clinical parameters and heart failure (HF) class were tested using univariate/multivariable Cox proportional hazard regression analyses to identify markers of mortality. RESULTS Twenty-three subjects died, with a 1-year mortality of 44%. Univariate predictors of mortality were HF class (P < .001), left ventricular systolic ejection time (ET) (P = .002), alkaline phosphatase (P < .001), and aspartate and alanine aminotransferase (P = .003 each). On multivariable analysis, only HF class (hazard ratio [HR] 4.86; 95% confidence interval [CI], 1.58-14.9; P = .006), ET (10 ms increase; HR 0.87; CI, 0.78-0.97; P = .01), and alkaline phosphatase (10 U/L increase; HR 1.04; CI, 1.01-1.06; P = .01) were prognostic. ET <or= 240 ms had a sensitivity of 61% and a specificity of 90% in predicting 1-year mortality and a sensitivity of 73% and a specificity of 90% in predicting 1-year cardiac mortality. CONCLUSION AL amyloidosis was associated with high long-term mortality. Among echocardiographic and clinical parameters, only ET and alkaline phosphatase had incremental value to HF class in predicting mortality. This may be useful to identify high-risk patients.

Time-efficient patient-specific quantification of regional carotid artery fluid dynamics and spatial correlation with plaque burden.

PURPOSE Low wall shear stress (WSS) and high oscillatory shear index (OSI) influence plaque formation, yet little is known about their role in progression/regression of established plaques because of lack of practical means to calculate them in individual patients. Our aim was to use computational fluid dynamics (CFD) models of patients with carotid plaque undergoing statin treatment to calculate WSS and OSI in a time-efficient manner, and determine their relationship to plaque thickness (PT), plaque composition (PC), and regression. METHODS Eight patients (68 +/- 9 yr, one female) underwent multicontrast 3 T MRI at baseline and six-month post statin treatment. PT and PC were measured in carotid segments (common-CC, bifurcation-B, internal-IC) and circumferentially in nonoverlapping 600 angles and correlated with CFD models created from MRI, ultrasound, and blood pressure. RESULTS PT was highest in B (2.42 +/- 0.98 versus CC: 1.60 +/- 0.47, IC: 1.62 +/- 0.52 mm, p < 0.01). Circumferentially, plaque was greatest opposite the flow divider (p < 0.01), where the lowest WSS and highest OSI were observed. In B and IC, PT was inversely related to WSS (R = -0.28 and -0.37, p < 0.01) and directly related to OSI (R = 0.22 and 0.52, p < 0.05). The total plaque volume changed from 1140 +/- 437 to 974 +/- 587 mm3 at six months (p = 0.1). Baseline WSS, but not OSI, correlated with changes in PT, necrotic tissue, and hemorrhage in B and IC, but not CC. CFD modeling took 49 +/- 18 h per patient. CONCLUSIONS PT and PC correspond to adverse WSS and OSI in B and IC, and WSS is modestly but significantly related to changes in PT after short-term statin treatment. Regional hemodynamics from CFD can feasibly augment routine clinical imaging for comprehensive plaque evaluation.

In vitro Evaluation of Labral Seal after Labrum Reconstruction.

Objectives: The objective of this study was to quantify labral seal in labrum reconstructed joints by measuring the suction force, and compare them to the same joints with intact labrum and torn labrum. Methods: Six cadaveric specimens of hemi-pelvis with proximal femur were obtained for the study from musculoskeletally normal donors (mean age: 54.5 yrs, range 46-61 yrs). Full pelvis specimens were first skeletonized and potted onto a custom mounting jig secured at the iliac wings using bolts and dental cement. The mounting jigs consisted of a metal bracket system which allowed the hemipelvis to rotate anteriorly and posteriorly. A pullout handle with a 6-axis load cell (AMTI, Watertown, MA) on board was fixed in the lateral aspect of the femur, 1-inch below the greater trochanter. Manual pullout was performed along the axis of femoral neck, while suction force induced by the negative pressured measured by the load cell was recorded at a rate of 100 Hz. The width of the intact labrum was measured with a ruler at the 12 o’clock position. Each specimen was tested under three labrum conditions: intact, torn, and reconstructed. The intact specimen was tested first. The labrum was then released directly off of the bony acetabular rim from the 11 o’clock position to the 2 o’clock position using a scalpel. The pull out strength was tested again. Finally, labral reconstruction was performed using five suture anchors evenly spaced within the span of the tear, and secured with a single simple suture per anchor. Pull out test was performed the third time using the same protocols. Prior to each of three pull out tests, light mineral oil (Johnson & Johnson baby oil) was applied to the surfaces of the femoral head and acetabulum to simulate the lubricating effect of synovial fluid. The peak suction forces from the three stages were derived from the load cell measurement based on the handle orientation. Peak suction force from the torn and reconstruction stages were also normalized with respect to the native stage and repeated measure ANOVA was used to test the differences. Results: Large variations in labral morphology were observed among the six specimens. The width of the labrum at 12 o’clock ranged from 3 mm to 15 mm (mean 6.3 mm). Two of the six labrums showed signs of ossification. Correspondingly, the peak suction force measured from the six-axis load cell also exhibited wide inter-specimen ranges. On average, the peak suction force was 45.1±45.5 N in the native stage, 7.4±5.9 N in the torn stage, and 27.2±22.6 N in reconstruction stage. However, after normalization with respect to the intact stage, all specimens demonstrated a consistent trend of significant 74%±26% reduction for the labral torn stage (p<0.01), and a substantial 77%±25% restoration for the labral reconstruction stage compared to its native stage. The difference in peak suction force between the reconstructed stage and the native stage was not statistically significant (p=0.19). Conclusion: We produced a cadaver model to quantify labral seal in its intact, torn, and reconstructed stages. Results from this study demonstrated a consistent trend across various labral morphologic conditions, that is labral tear had significant impact on labral seal, and labral reconstruction can restore 77% of sealing function as the intact.