Hyung-Bok Park

Noninvasive Fractional Flow Reserve Derived From Computed Tomography Angiography for Coronary Lesions of Intermediate Stenosis Severity Results From the DeFACTO Study

Background—Fractional flow reserve derived from computed tomography angiography (FFRCT) is a noninvasive method for diagnosis of ischemic coronary lesions. To date, the diagnostic performance of FFRCT for lesions of intermediate stenosis severity remains unexamined. Methods and Results—Among 407 vessels from 252 patients at 17 centers who underwent CT, FFRCT, invasive coronary angiography, and invasive FFR, we identified 150 vessels of intermediate stenosis by CT, defined as 30% to 69% stenosis. FFRCT, FFR, and CT were interpreted in blinded fashion by independent core laboratories. FFRCT and FFR ⩽0.80 were considered hemodynamically significant, whereas CT stenosis ≥50% was considered obstructive. Diagnostic performance of FFRCT versus CT was assessed for accuracy, sensitivity, specificity, positive predictive values, and negative predictive values. Area under the receiver operating characteristic curve and net reclassification improvement were evaluated. For lesions of intermediate stenosis severity, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of FFRCT were 71%, 74%, 67%, 41%, and 90%, whereas accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT stenosis were 63%, 34%, 72%, 27%, and 78%. FFRCT demonstrated superior discrimination compared with CT stenosis on per-patient (area under the receiver operating characteristic curve, 0.81 versus 0.50; P=0.0001) and per-vessel basis (area under the receiver operating characteristic curve, 0.79 versus 0.53; P<0.0001). FFRCT demonstrated significant reclassification of CT stenosis for lesion-specific ischemia (net reclassification improvement, 0.45; 95% confidence interval, 0.25–0.65; P=0.01). Conclusions—FFRCT possesses high diagnostic performance for diagnosis of ischemic for lesions of intermediate stenosis severity. Notably, the high sensitivity and negative predictive value suggest the ability of FFRCT to effectively rule out intermediate lesions that cause ischemia.

Non-invasive Fractional Flow Reserve Derived from CT Angiography (FFRCT) for Coronary Lesions of Intermediate Stenosis Severity: Results from the DeFACTO study

Background—Fractional flow reserve derived from computed tomography angiography (FFRCT) is a noninvasive method for diagnosis of ischemic coronary lesions. To date, the diagnostic performance of FFRCT for lesions of intermediate stenosis severity remains unexamined. Methods and Results—Among 407 vessels from 252 patients at 17 centers who underwent CT, FFRCT, invasive coronary angiography, and invasive FFR, we identified 150 vessels of intermediate stenosis by CT, defined as 30% to 69% stenosis. FFRCT, FFR, and CT were interpreted in blinded fashion by independent core laboratories. FFRCT and FFR ⩽0.80 were considered hemodynamically significant, whereas CT stenosis ≥50% was considered obstructive. Diagnostic performance of FFRCT versus CT was assessed for accuracy, sensitivity, specificity, positive predictive values, and negative predictive values. Area under the receiver operating characteristic curve and net reclassification improvement were evaluated. For lesions of intermediate stenosis severity, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of FFRCT were 71%, 74%, 67%, 41%, and 90%, whereas accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT stenosis were 63%, 34%, 72%, 27%, and 78%. FFRCT demonstrated superior discrimination compared with CT stenosis on per-patient (area under the receiver operating characteristic curve, 0.81 versus 0.50; P=0.0001) and per-vessel basis (area under the receiver operating characteristic curve, 0.79 versus 0.53; P<0.0001). FFRCT demonstrated significant reclassification of CT stenosis for lesion-specific ischemia (net reclassification improvement, 0.45; 95% confidence interval, 0.25–0.65; P=0.01). Conclusions—FFRCT possesses high diagnostic performance for diagnosis of ischemic for lesions of intermediate stenosis severity. Notably, the high sensitivity and negative predictive value suggest the ability of FFRCT to effectively rule out intermediate lesions that cause ischemia.

Aggregate Plaque Volume by Coronary Computed Tomography Angiography Is Superior and Incremental to Luminal Narrowing for Diagnosis of Ischemic Lesions of Intermediate Stenosis Severity

OBJECTIVES This study examined the performance of percent aggregate plaque volume (%APV), which represents cumulative plaque volume as a function of total vessel volume, by coronary computed tomography angiography (CTA) for identification of ischemic lesions of intermediate stenosis severity. BACKGROUND Coronary lesions of intermediate stenosis demonstrate significant rates of ischemia. Coronary CTA enables quantification of luminal narrowing and %APV. METHODS We identified 58 patients with intermediate lesions (30% to 69% diameter stenosis) who underwent invasive angiography and fractional flow reserve. Coronary CTA measures included diameter stenosis, area stenosis, minimal lumen diameter (MLD), minimal lumen area (MLA) and %APV. %APV was defined as the sum of plaque volume divided by the sum of vessel volume from the ostium to the distal portion of the lesion. Fractional flow reserve ≤ 0.80 was considered diagnostic of lesion-specific ischemia. Area under the receiver operating characteristic curve and net reclassification improvement (NRI) were also evaluated. RESULTS Twenty-two of 58 lesions (38%) caused ischemia. Compared with nonischemic lesions, ischemic lesions had smaller MLD (1.3 vs. 1.7 mm, p = 0.01), smaller MLA (2.5 vs. 3.8 mm(2), p = 0.01), and greater %APV (48.9% vs. 39.3%, p < 0.0001). Area under the receiver operating characteristic curve was highest for %APV (0.85) compared with diameter stenosis (0.68), area stenosis (0.66), MLD (0.75), or MLA (0.78). Addition of %APV to other measures showed significant reclassification over diameter stenosis (NRI 0.77, p < 0.001), area stenosis (NRI 0.63, p = 0.002), MLD (NRI 0.62, p = 0.001), and MLA (NRI 0.43, p = 0.01). CONCLUSIONS Compared with diameter stenosis, area stenosis, MLD, and MLA, %APV by coronary CTA improves identification, discrimination, and reclassification of ischemic lesions of intermediate stenosis severity.

CT Angiography (CTA) and Diagnostic Performance of Noninvasive Fractional Flow Reserve: Results From the Determination of Fractional Flow Reserve by Anatomic CTA (DeFACTO) Study

OBJECTIVE Fractional flow reserve (FFR) computed from standard coronary CT scans (FFRCT) is a novel noninvasive method for determining the functional significance of coronary artery lesions. Compared with CT alone, FFRCT significantly improves diagnostic accuracy and discrimination for patients with and without hemodynamically significant coronary artery stenoses. To date, the impact of CT image quality on diagnostic performance of FFRCT is unknown. We evaluated the impact of patient preparation, CT scan protocol, and factors related to image quality on the diagnostic accuracy of FFRCT. SUBJECTS AND METHODS We studied stable patients with suspected coronary artery disease (CAD), enrolled from 17 centers, who underwent CT, invasive coronary angiography, FFR, and FFRCT. The accuracy of CT and FFRCT for diagnosis of ischemia was compared against an invasive FFR reference standard. Anatomically obstructive CAD was defined by a stenosis value of at least 50 by CT or invasive coronary angiography, whereas ischemia was defined by an FFR or FFRCT of up to 0.80. Ischemia was assessed at the per-patient and per-vessel levels. Diagnostic performance of FFRCT was then evaluated in relation to patient preparation, including administration before CT of a β-blocker or nitroglycerin, as well as in relation to imaging characteristics, including misalignment, noise, motion, and coronary artery calcium. RESULTS Among 252 study participants, 137 (54.0%) had an abnormal FFR. Administration of a β-blocker increased FFRCT specificity (51.0% vs 66.0%; p = 0.03) with lower bias (-0.084 vs -0.048; p = 0.008), whereas nitroglycerin pretreatment within 30 minutes of CT was associated with improved specificity (54.0% vs 75.0%; p = 0.013). Misalignment artifacts resulted in impaired sensitivity (43.0% vs 86.0%; p = 0.001) with resultant reductions in overall accuracy (56.0% vs 71.0%; p = 0.03). No differences in diagnostic performance of FFRCT were noted in the presence of coronary motion or increasing coronary artery calcium score. CONCLUSION Use of β-blockade and nitroglycerin administration before CT improve diagnostic performance of FFRCT. Diagnostic accuracy of FFRCT is significantly reduced in the setting of misalignment artifacts.

Clinical Feasibility of 3D Automated Coronary Atherosclerotic Plaque Quantification Algorithm on Coronary Computed Tomography Angiography: Comparison with Intravascular Ultrasound.

ObjectiveTo evaluate the diagnostic performance of automated coronary atherosclerotic plaque quantification (QCT) by different users (expert/non-expert/automatic).MethodsOne hundred fifty coronary artery segments from 142 patients who underwent coronary computed tomography angiography (CCTA) and intravascular ultrasound (IVUS) were analyzed. Minimal lumen area (MLA), maximal lumen area stenosis percentage (%AS), mean plaque burden percentage (%PB), and plaque volume were measured semi-automatically by expert, non-expert, and fully automatic QCT analyses, and then compared to IVUS.ResultsBetween IVUS and expert QCT analysis, the correlation coefficients (r) for the MLA, %AS, %PB, and plaque volume were excellent: 0.89 (p < 0.001), 0.84 (p < 0.001), 0.91 (p < 0.001), and 0.94 (p < 0.001), respectively. There were no significant differences in the mean parameters (all p values >0.05) except %AS (p = 0.01). The automatic QCT analysis showed comparable performance to non-expert QCT analysis, showing correlation coefficients (r) of the MLA (0.80 vs. 0.82), %AS (0.82 vs. 0.80), %PB (0.84 vs. 0.73), and plaque volume (0.84 vs. 0.79) when they were compared to IVUS, respectively.ConclusionFully automatic QCT analysis showed clinical utility compared with IVUS, as well as a compelling performance when compared with semiautomatic analyses.Key Points• Coronary CTA enables the assessment of coronary atherosclerotic plaque.• High-risk plaque characteristics and overall plaque burden can predict future cardiac events.• Coronary atherosclerotic plaque quantification is currently unfeasible in practice.• Quantitative computed tomography coronary plaque analysis software (QCT) enables feasible plaque quantification.• Fully automatic QCT analysis shows excellent performance.

Aortic calcification is associated with arterial stiffening, left ventricular hypertrophy, and diastolic dysfunction in elderly male patients with hypertension.

Background: Stiffening of large arteries can result in changes of cardiac structure and function by increasing afterload to the left ventricle. Calcification has been proposed as a mechanism underlying progression of arterial stiffening. The aim of the current study was to investigate the relationship between aortic calcification, arterial stiffening, left ventricular hypertrophy, and diastolic dysfunction. Methods: One hundred and sixty-four hypertensive elderly (≥65 years old) male patients with normal left ventricular systolic function (left ventricular ejection fraction ≥55%) underwent transthoracic echocardiography, brachial-ankle pulse wave velocity (baPWV), and noncontrast computed tomography. Coronary artery calcium score and aorta calcium score (ACS) were measured on noncontrast computed tomography using the volume method. Left ventricular dimensions, mitral inflow velocities, and early mitral annular (E′) velocity were measured using transthoracic echocardiography. The left ventricular mass index (LVMI) was calculated. Results: The logACS was associated with mean baPWV (r = 0.387, P = 0.001), LVMI (r = 0.241, P < 0.002), E′ velocity (r = −0.293, P < 0.001), and E/E′ (r = 0.194, P = 0.013), suggesting arterial stiffening, increased left ventricular mass, and diastolic dysfunction in patients with raised ACS. On multivariate analysis, the LVMI showed an independent positive association with the logACS, even after adjusting for various clinical variables and the coronary artery calcium score (P = 0.009). Similarly, E′ velocity also demonstrated an independent negative association with the logACS on multivariate analysis (P = 0.003). The mean baPWV, LVMI, and E′ velocity showed similar correlations with both thoracic and abdominal ACS, even when thoracic and abdominal calcium scores were calculated separately. Conclusion: Heavy aortic calcification and resultant arterial stiffening might underlie left ventricular hypertrophy and diastolic dysfunction in elderly male patients with hypertension.

Automatic aortic valve landmark localization in coronary CT angiography using colonial walk

The minimally invasive transcatheter aortic valve implantation (TAVI) is the most prevalent method to treat aortic valve stenosis. For pre-operative surgical planning, contrast-enhanced coronary CT angiography (CCTA) is used as the imaging technique to acquire 3-D measurements of the valve. Accurate localization of the eight aortic valve landmarks in CT images plays a vital role in the TAVI workflow because a small error risks blocking the coronary circulation. In order to examine the valve and mark the landmarks, physicians prefer a view parallel to the hinge plane, instead of using the conventional axial, coronal or sagittal view. However, customizing the view is a difficult and time-consuming task because of unclear aorta pose and different artifacts of CCTA. Therefore, automatic localization of landmarks can serve as a useful guide to the physicians customizing the viewpoint. In this paper, we present an automatic method to localize the aortic valve landmarks using colonial walk, a regression tree-based machine-learning algorithm. For efficient learning from the training set, we propose a two-phase optimized search space learning model in which a representative point inside the valvular area is first learned from the whole CT volume. All eight landmarks are then learned from a smaller area around that point. Experiment with preprocedural CCTA images of TAVI undergoing patients showed that our method is robust under high stenotic variation and notably efficient, as it requires only 12 milliseconds to localize all eight landmarks, as tested on a 3.60 GHz single-core CPU.

IVUS Artifacts and Image Control

Artifacts in IVUS imaging are an infrequently inevitable phenomenon due to the inherent limitations of ultrasound modality itself. Therefore, it should be important to distinguish artifacts from true image findings at each specific clinical scenario and gain image control skills to reduce artifacts as much as possible.

Consistency of quantitative analysis of coronary computed tomography angiography

BACKGROUND The present study aimed to assess the reliability and reproducibility of coronary computed tomography angiography (CCTA) for the serial quantitative assessment of plaque volume. METHODS Patients who underwent repeated CCTA scans within 90 days were retrospectively screened and enrolled. Clinical data and CCTA imaging data were collected. Paired CCTA scans were analyzed using the quantitative method by separate observers blinded to the other paired CCTA scans. Results were compared between the index CCTA and follow-up CCTA. RESULTS Paired CT scans of 95 patients (61 ± 13 years; 56.8% men) with same tube voltages (kVp) at both CCTAs and 24 patients (57 ± 19 years; 48.3% men) with different kVp at two CCTAs were analyzed. In patients with same kVp at both CCTAs, there were no difference in PV and PVs of each components in per-segment analysis and per-lesion analysis (all p > 0.05). In per-lesion analysis of CCTAs from patients who used different kVp between two CCTAs, lesion length, area and diameter stenosis, and PVs were not different between index and follow-up CCTAs (all p > 0.05). Segment length and PV were also showed no difference between two serial CCTAs in per-segment analysis. CONCLUSION We showed the reproducibility and reliability of quantitative analysis of CCTA for assessment of coronary plaques. CCTA can be applied for the serial quantitative assessment of coronary artery disease progression, regardless of differences in the image acquisition protocol.

Quantitative measurement of lipid rich plaque by coronary computed tomography angiography: A correlation of histology in sudden cardiac death

BACKGROUND AND AIMS Recent advancements in coronary computed tomography angiography (CCTA) have allowed for the quantitative measurement of high-risk lipid rich plaque. Determination of the optimal threshold for Hounsfield units (HU) by CCTA for identifying lipid rich plaque remains unknown. We aimed to validate reliable cut-points of HU for quantitative assessment of lipid rich plaque. METHODS 8 post-mortem sudden coronary death hearts were evaluated with CCTA and histologic analysis. Quantitative plaque analysis was performed in histopathology images and lipid rich plaque area was defined as intra-plaque necrotic core area. CCTA images were analyzed for quantitative plaque measurement. Low attenuation plaque (LAP) was defined as any pixel < 30, 45, 60, 75, and 90 HU cut-offs within a coronary plaque. The area of LAP was calculated in each cross-section. RESULTS Among 105 cross-sections, 37 (35.2%) cross-sectional histology images contained lipid rich plaque. Although the highest specificity for identifying lipid rich plaque was shown with <30 HU cut-off (88.2%), sensitivity (e.g. 55.6% for <75 HU, 16.2% for <30 HU) and negative predictive value (e.g. 75.9% for <75 HU, 65.9% for <30 HU) tended to increase with higher HU cut-offs. For quantitative measurement, <75 HU showed the highest correlation coefficient (0.292, p = 0.003) and no significant differences were observed between lipid rich plaque area and LAP area between histology and CT analysis (Histology: 0.34 ± 0.73 mm2, QCT: 0.37 ± 0.71 mm2, p = 0.701). CONCLUSIONS LAP area by CCTA using a <75 HU cut-off value demonstrated high sensitivity and quantitative agreement with lipid rich plaque area by histology analysis.