Yanlin Gao

Determination of Left Ventricular Mass on Cardiac Computed Tomographic Angiography1

RATIONALE AND OBJECTIVES Left ventricular hypertrophy (LVH) is associated with an increased risk of cardiac death. The present study evaluates whether using computed tomographic (CT)-derived criteria for normal myocardial mass can improve detection of LVH on CT angiography (CTA). MATERIALS AND METHODS A total of 2238 subjects (63 +/- 9 years, 27% female) who underwent CTA were studied. To identify normal limits for CT-derived myocardial mass, we studied normal subjects (those without diabetes, hypertension, congestive heart failure, or coronary artery disease). Left ventricular mass (LVM) was measured manually using two different workstations. The CT criteria of LVH was defined as LVM above the 97th percentile per gender and compared to echocardiographic criteria (110 g/m(2) in women; 124 g/m(2) in men), and specificity and sensitivity of both models to detect LVH were calculated. RESULTS The LVM was higher in men than women in normal cohorts (75.5 +/- 14.0 vs. 63.1 +/- 12.8 g/m(2), P = .001 with electron beam CTA and 78.5 +/- 11.9 vs. 65.0 +/- 9.2 g/m(2), P = .001 with 64 multidetector [MD] CT, respectively). The coefficient of variation between electron beam CTA and 64 MDCT for measuring LVM was 3.1%. Comparing the new CTA/64 MDCT criteria of LVH (103.0 g/m(2) in men; 89.0 g/m(2) in women) to the previous echocardiographic criteria of LVH, the specificity in women and men decreased from 100% in both genders by echocardiography to 91.8% and 92.6%, respectively, but the sensitivity increased from 42.0% to 100% and from 41.1% to 100%. CONCLUSION This study suggests that CT-measured LVM has low variability and normal values based on CT criteria will potentially increase the early detection of LVH.

Gender differences in coronary artery diameter are not related to body habitus or left ventricular mass.

Smaller coronary artery diameter portends worse outcomes after coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). The suggestion that women have smaller coronary artery diameters than men has not been validated by a large‐scale study.

Relation of Aortic Valve Calcium to Chronic Kidney Disease (from the Chronic Renal Insufficiency Cohort Study)

Although subjects with chronic kidney disease (CKD) are at markedly increased risk for cardiovascular mortality, the relation between CKD and aortic valve calcification has not been fully elucidated. Also, few data are available on the relation of aortic valve calcification and earlier stages of CKD. We sought to assess the relation of aortic valve calcium (AVC) with estimated glomerular filtration rate (eGFR), traditional and novel cardiovascular risk factors, and markers of bone metabolism in the Chronic Renal Insufficiency Cohort (CRIC) Study. All patients who underwent aortic valve scanning in the CRIC study were included. The relation between AVC and eGFR, traditional and novel cardiovascular risk factors, and markers of calcium metabolism were analyzed using both unadjusted and adjusted regression models. A total of 1,964 CRIC participants underwent computed tomography for AVC quantification. Decreased renal function was independently associated with increased levels of AVC (eGFR 47.11, 44.17, and 39 ml/min/1.73 m2, respectively, p<0.001). This association persisted after adjusting for traditional, but not novel, AVC risk factors. Adjusted regression models identified several traditional and novel risk factors for AVC in patients with CKD. There was a difference in AVC risk factors between black and nonblack patients. In conclusion, our study shows that eGFR is associated in a dose-dependent manner with AVC in patients with CKD, and this association is independent of traditional cardiovascular risk factors.

Noncontrast cardiac computed tomography image-based vertebral bone mineral density: the Multi-Ethnic Study of Atherosclerosis (MESA).

RATIONALE AND OBJECTIVES Cardiac computer tomography (CT) image-based vertebral bone mineral density (BMD) assessment and the influence of cardiovascular disease risk factors on BMD have not been systematically evaluated, especially in a community-based, multiethnic population. METHODS A cross-sectional study design is used to determine if cardiac CT image is a reliable source to assess vertebral BMD, and a total of 2028 CT images were obtained from the Multi-Ethnic Study of Atherosclerosis, a large, diverse US cohort of adults 45 to 84 years of age. RESULTS Cardiac CT image allows the rapid assessment of vertebral BMD and related fractures. The mean BMD was significantly higher in men compared with women for thoracic vertebrae (143.2 ± 41.2 vs 138.7 ± 42.7 mg/cm³, respectively, P = .014), as well as for lumbar vertebrae (125.0 ± 37.9 vs 117.2 ± 39.4 mg/cm³, respectively, P < .0001). Thoracic and lumbar BMDs are closely correlated (correlation coefficient 0.87, P < .001), independent of age and other confounders including sex and race. African American men had the highest thoracic BMD among all race/ethnicity and sex subgroups. Prevalence of fractures in total vertebrae is 4.2%. Lumbar had approximately 2 times higher prevalence of fracture than thoracic, and the prevalence of vertebral fractures is 1.5% and 3.1% for thoracic and lumbar vertebrae, respectively. CONCLUSIONS Using cardiac CT images to garner and assess vertebral BMD is a feasible and reliable method. Cardiac CT has the additional advantages of evaluate vertebral bone health while assessing cardiovascular disease risk with no extra cost or radiation exposure.

Dual-standard reference values of left ventricular volumetric parameters by multidetector CT angiography

BACKGROUND The papillary and trabecular muscles constitute a significant percentage of left ventricular mass and volume. The influence of the papillary and trabecular muscles on left ventricular parameters has not been described with multidetector CT angiography. OBJECTIVE The aims of this study are (1) to derive reference values for left ventricular volumetric parameters both including and excluding the papillary and trabecular muscles and (2) to establish the optimal segmentation method for measuring these values. METHODS A total of 179 subjects (mean age, 55.4 ± 9 years; 102 women) without heart disease and at low risk of cardiovascular disease who underwent CT angiography were selected. Left ventricular volumes, myocardial volume, and ejection fraction were measured with epicardial and 2 endocardial trace methods, including and excluding trace for the papillary and trabecular muscles. Values of all parameters obtained by both endocardial trace methods were compared. RESULTS Significant difference between both trace groups for all parameters on both sexes was found (P < .001). Significant differences in precision error of remeasurement were found in the including trace (3.6%) compared with the excluding trace (4.7%; P < .05) and in the epicardial trace (2.2%) compared with both endocardial traces (P < .001). CONCLUSION The left ventricular parameters measured by CT angiography were influenced significantly by the trace method by including or excluding the papillary and trabecular muscles. The dual-standard reference values of left ventricular parameters were established, and the optimal segmentation methods were definite in considering the heart size and image quality studied with retrospective and prospective CT angiography.

Model-based Automatic Segmentation Algorithm Accurately Assesses the Whole Cardiac Volumetric Parameters in Patients with Cardiac CT Angiography: A Validation Study for Evaluating the Accuracy of the Workstation Software and Establishing the Reference Values

RATIONALE AND OBJECTIVES The cardiac chamber volumes and functions can be assessed manually and automatically using the current computed tomography (CT) workstation system. We aimed to evaluate the accuracy and precision and to establish the reference values for both segmentation methods using cardiac CT angiography (CTA). MATERIALS AND METHODS A total of 134 subjects (mean age 55.3 years, 72 women) without heart disease were enrolled in the study. The cardiac four-chamber volumes, left ventricular (LV) mass, and biventricular functions were measured with manual, semiautomatic, and model-based fully automatic approaches. The accuracies of the semiautomated and fully automated approaches were validated by comparing them with manual segmentation as a reference. The precision error was determined and compared for both manual and automatic measurements. RESULTS No significant difference was found between the manual and semiautomatic assessments for the assessment of all functional parameters (P > .05). Using the manual method as a reference, the automatic approach provided a similar value in LV ejection fraction and left atrial volumes in both genders and right ventricular (RV) stroke volume in women (P > .05), with some underestimation of RV volume (P < .001) and overestimation of all remaining parameters (P < .05) in both genders. In addition, a significantly higher precision with a considerable association in intermeasurement (reproducibility) was observed using the automated approach. CONCLUSIONS The model-based fully automatic segmentation algorithm can help with the assessment of the cardiac four-chamber volume and function. This may help in establishing reference values of functional parameters in patients who undergo cardiac CTA.

Sex-specific biatrial volumetric measurements obtained with use of multidetector computed tomography in subjects with and without coronary artery disease.

Atrial volumetric measurement has proven clinical implications. Advances in cardiac imaging, notably the precision enabled by multidetector computed tomography (MDCT), herald the need for new criteria of what constitutes normal volumetric measurements. With use of 64-slice MDCT, we compared the atrial volumes in healthy individuals with those in individuals with coronary artery disease. By means of manual segmentation, we measured biatrial volume in 686 participants who underwent retrospective electrocardiographic-gated MDCT angiographic evaluation. The study population included a control group of 203 persons with no cardiac abnormalities, and a study group of 483 patients with obstructive coronary artery disease. All variables were compared between men and women and between the groups. We found a significant difference in left atrial end-systolic and end-diastolic volumes between men and women in the control group (P <0.05); however, right atrial volumes were similar. In comparison with the entire control group, the coronary artery disease group had significantly higher left atrial volume, significantly lower right atrial stroke volume, and significantly lower biatrial ejection fraction, except for left atrial ejection fraction in men. Right atrial volume and left atrial stroke volume were not significantly different. The results imply that a sex-specific reference value is necessary for left atrial volumetric evaluation, and that left atrial volume and biatrial ejection fraction (excluding left atrial ejection fraction in men) might be useful during diagnosis and prognosis in patients who have coronary artery disease.

Relation of subclinical left and right ventricular dysfunctions measured by computed tomography angiography with the severity of coronary artery disease.

ObjectiveVentricular dysfunction in asymptomatic patients is directly linked to the eventual development of symptomatic congestive heart failure. This study investigates whether subclinical left ventricular (LV) and right ventricular (RV) dysfunctions measured by computed tomography angiography is associated with the severity of coronary artery disease (CAD). Methods and resultsWe studied 1608 consecutive patients with suspected CAD (age 62±10 years, 64% male), who underwent coronary artery calcium (CAC) scanning and computed tomography angiography. RV and LV volumes at end systole and end diastole were measured, and stroke volume and ejection fraction were calculated using the Simpson method and piecewise smooth subdivision surface (PSSS) method. Analysis by Simpson was performed on short axis and apical four-chamber views. Axial images were used to measure RV and LV volumes by the PSSS method. CAD was defined as normal, nonobstructive, and obstructive (0% stenosis, luminal stenosis 1–49 and 50%+, respectively). There was a strong agreement between PSSS and Simpson method RV ejection fraction (RVEF) and LV ejection fraction (LVEF) measurement. RVEF and LVEF decreased proportionally from CAC 0 to CAC 100+, also from normal-to-diseased coronaries (P=0.001). After adjustment for cardiovascular risk factors, the mean LVEF and RVEF decreased 2.8 and 2.4%, respectively in CAC 100+ compared with CAC 0. Similarly, LVEF and RVEF decreased significantly in nonobstructive CAD (−3.5 and −3.1%, respectively) and obstructive CAD (−5.9 and −4.5%, respectively) compared with normal coronaries, respectively (P<0.05). The relative risk of each 5% decrease in LVEF and RVEF was 1.33 and 1.29 for nonobstructive CAD and 1.54 and 1.33 for obstructive CAD, respectively. ConclusionThe presence and severity of coronary atherosclerosis is significantly associated with subclinical RV and LV dysfunctions.

Accuracy in Quantification of Coronary Calcification with CT: A Cork-Dog Heart Phantom Study

RATIONALE AND OBJECTIVES Coronary artery calcium is a sensitive risk predictor of cardiac events. However, measurement of calcium foci is affected by partial-volume effects, which ultimately have an effect on accuracy and reproducibility of calcium scores. In this study, we describe the accuracy of quantification of calcium foci of known size and density using cork-dog heart phantoms. MATERIALS AND METHODS Five study phantoms were constructed from cork chests and dog hearts containing 135 calcium hydroxyapatite (CaHA) foci of known volume, mass, and concentration located in the coronary arteries or the myocardium. Hearts were separated into two groups: (1) three hearts containing large, high-density foci and (2) two hearts containing small, low-density foci. The phantoms were scanned using a standard coronary artery calcium (CAC) protocol and the volume and mean intensity of foci were measured. RESULTS In group 1, the total volume of 87 CaHA foci measured was 4284 and 3779 mm(3) with electron beam computed tomography (EBCT); multidetector computed tomography (MDCT), respectively (P < .001). Both were significantly larger than the true volume (2713.9 mm(3), P < .001). In Group 2, the total volume of 57 CaHA foci measured was 592.6 and 702.9 mm(3) with EBT and MDCT, respectively (P < .001). Both were significantly smaller than the true volume (1733.2 mm(3), P < .001). We found that EBCT values for volume were approximately generally higher than MDCT values, but strongly correlated (r = 0.95, P < .0001). Agatston scores were found to be nearly equivalent between EBCT and MDCT and were similarly strongly correlated (r = 0.97, P < .0001). CONCLUSIONS Computed tomography images overestimate the volume of large, dense CaHA foci while underestimating the volume of smaller (<6.6 mm(3)), less dense foci. This may have significant implications on CAC scoring and volume measurement. EBCT overestimated calcium more than MDCT, most likely from increased image noise.

UPPER LIMIT OF EXPANSION RATES OF THORACIC AORTIC DIAMETER IN ASYMPTOMATIC POPULATION EVALUATED BY A ROUTINE HEART CT SCAN

Accelerating expansion of aortic diameter is a meaningful characteristic of aneurysm formation, however, the normal annual expansion rate of the thoracic aorta has not been well elucidated. We sought to evaluate the annual expansion rate of the thoracic aortic diameter in the asymptomatic population