Tairo Kurita

Impact of Frequency-Domain Optical Coherence Tomography Guidance for Optimal Coronary Stent Implantation in Comparison With Intravascular Ultrasound Guidance

Background— Frequency-domain optical coherence tomography (FD-OCT) is a novel, high resolution intravascular imaging modality. Intravascular ultrasound (IVUS) is a widely used conventional imaging modality for achieving optimal stent deployment. The aim of this study was to evaluate the impact of FD-OCT guidance for coronary stent implantation compared with IVUS guidance. Methods and Results— A total of 70 patients with de novo coronary artery lesions and either unstable or stable angina pectoris were enrolled in this randomized study (optical coherence tomography [OCT] group: n=35, IVUS group: n=35). In the OCT group, stent implantation was performed under FD-OCT guidance alone and final stent expansion was evaluated by IVUS. In the IVUS group, conventional IVUS guidance was used and final stent apposition was evaluated by FD-OCT. There were no significant differences regarding the procedural, fluoroscopy time, and contrast volume. Although device and clinical success rates also were similar, the visibility of vessel border was significantly lower in the OCT group (P<0.05). Minimum and mean stent area and focal and diffuse stent expansion were smaller (6.1±2.2 mm versus 7.1±2.1 mm, 7.5±2.5 versus 8.7±2.4 mm, 64.7±13.7% versus 80.3±13.4%, 84.2±15.8% versus 98.8±16.5%, P<0.05, respectively), and the frequency of significant residual reference segment stenosis at the proximal edge was higher in the OCT group (P<0.05). Incomplete apposed struts in both groups were similar (P=0.34). Conclusions— FD-OCT guidance for stent implantation was associated with smaller stent expansion and more frequent significant residual reference segment stenosis compared with conventional IVUS guidance.

Morphological differences of tissue characteristics between early, late, and very late restenosis lesions after first generation drug-eluting stent implantation: an optical coherence tomography study

AIMS Restenosis of drug-eluting stents (DESs) might be different from that of bare metal stent restenosis in diverse ways including mechanisms and time course; however, these have not been fully examined. To gain insight into the mechanisms and time course of DES restenosis, we evaluated the characteristics of restenotic lesions of first generation DES using optical coherence tomography (OCT). METHODS AND RESULTS We compared the morphological characteristics of early in-stent restenosis (<1 year: E-ISR, n = 43), late ISR (1-3 years: L-ISR, n = 22), and very late ISR (>3 years: VL-ISR, n = 21). OCT qualitative restenotic tissue analysis included the assessment of tissue structure [homogeneous or four types of heterogeneous intima (thin-cap fibroatheroma (TCFA)-like, layered, patchy or speckled pattern)], the presence of the peri-strut low intensity area (PLIA), microvessels, disruption with cavity, and intraluminal material and was performed at every 1 mm slice of the entire stent length. In addition to a greater trend for heterogeneous intima at the later phase, TCFA-like pattern image, intra-intima microvessels were increased from the early to the very late phase. On the other hand, the speckled pattern image was decreased from the early to the very late phase. CONCLUSION The OCT morphological characteristics of DES restenotic tissue varied at different time-points. OCT images in early DES ISR might be associated with delayed arterial healing, and neoatherosclerosis might contribute to late catch-up phenomenon (L-ISR and VL-ISR) after DES implantation.

Difference of Tissue Characteristics Between Early and Very Late Restenosis Lesions After Bare-Metal Stent Implantation An Optical Coherence Tomography Study

Background— Although in-stent restenosis (ISR) after bare-metal stent (BMS) implantation peaks in the early phase, very late (VL) ISR occasionally is observed beyond a few years after BMS implantation. To date, this mechanism has not been fully clarified. Methods and Results— We compared the morphological characteristics of VL-ISR (>5 years, without restenosis within the first year) (n=43) to those of early (E) ISR (within the first year) (n=39) using optical coherence tomography (OCT). Qualitative restenotic tissue analysis included assessment of tissue structure (homogeneous or heterogeneous), presence of microvessels, disrupted intima with cavity, and intraluminal material and was performed at every 1-mm slice of the entire stent. The proportions of cross-sections with heterogeneous intima in the entire stent was significantly higher in the VL-ISR group compared to the E-ISR group (60.5±28.5% versus 5.8±11.5%, P<0.0001), with heterogeneous intima being more frequently observed at the minimum lumen area site in the VL-ISR group (90.7% versus 17.9%, P<0.0001). Disrupted intima with cavity and intraluminal material also were observed more frequently in the VL-ISR group for the entire stent (18.6% versus 0%, 20.9% versus 2.6%, P<0.03) as well as at the minimum lumen area site (13.9% versus 0%,16.2% versus 0%, P<0.03). Conclusions— The morphological characteristics of restenotic tissue in VL-ISR were different from those in E-ISR and similar to atherosclerotic plaque. In BMS, progression of the atherosclerotic process within neointima after stent implantation may be associated with VL-ISR.

Regional myocardial perfusion reserve determined using myocardial perfusion magnetic resonance imaging showed a direct correlation with coronary flow velocity reserve by Doppler flow wire

AIMS Quantitative analysis of rest-stress myocardial perfusion magnetic resonance imaging (MRI) can provide assessments of regional myocardial perfusion reserve (MPR). The purpose of this study was to compare regional MPR determined by myocardial perfusion MRI with coronary flow reserve (CFR) by intracoronary Doppler flow wire. METHODS AND RESULTS Twenty patients with suspected coronary artery disease (CAD) were studied. Average peak velocity was measured by Doppler flow wire in the resting state and during adenosine triphosphate (ATP) stress in 36 coronary arteries. CFR measurements for each patient were performed in the culprit and one non-culprit non-stenotic artery. First-pass, contrast-enhanced myocardial perfusion MR images were obtained in the resting state and during ATP stress within the week before the Doppler wire procedure. Regional myocardial blood flow (MBF) was quantified in 16 myocardial segments by analysing arterial input and myocardial output using a Patlak plot method. MPR was calculated as stress MBF divided by rest MBF. CFR measured by Doppler flow wire was compared with MPR in the myocardial segments corresponding to vessel territories. The average MPR measured by perfusion MRI was 1.77 +/- 0.62 for the culprit arteries and 3.45 +/- 0.78 for the non-culprit arteries, respectively (P < 0.001). The averaged CFR by Doppler flow wire was 1.72 +/- 0.44 in the culprit arteries and 3.14 +/- 0.74 in the non-culprit arteries, respectively (P < 0.001). For both culprit and non-culprit vessel groups, significant direct correlations were observed between MR assessments of MPR and Doppler assessments of CFR (culprit artery: R = 0.87, Non-culprit artery: R = 0.86) On Bland-Altman analysis, the mean differences between MPR determined by myocardial perfusion MRI and CFR measured by Doppler wire were 0.05 in culprit arteries (95% limit of agreement; -0.65 to 0.56) and 0.36 in non-culprit arteries (95% limit of agreement; -1.24 to 0.44). The sensitivity and specificity of MR measurement of MPR for predicting physiologically significant reduction of Doppler CFR (<2) was 88% (95% CI 61.7-98.5) and 90% (95% CI 68.3-98.8), respectively. CONCLUSION The current results using Doppler flow wire as a reference method demonstrated that quantitative analysis of stress-rest myocardial perfusion MRI can provide a non-invasive assessment of reduced MPR in patients with CAD.

Difference of Tissue Characteristics Between Early and Very Late Restenosis Lesions After Bare-Metal Stent ImplantationClinical Perspective

Background— Although in-stent restenosis (ISR) after bare-metal stent (BMS) implantation peaks in the early phase, very late (VL) ISR occasionally is observed beyond a few years after BMS implantation. To date, this mechanism has not been fully clarified. Methods and Results— We compared the morphological characteristics of VL-ISR (>5 years, without restenosis within the first year) (n=43) to those of early (E) ISR (within the first year) (n=39) using optical coherence tomography (OCT). Qualitative restenotic tissue analysis included assessment of tissue structure (homogeneous or heterogeneous), presence of microvessels, disrupted intima with cavity, and intraluminal material and was performed at every 1-mm slice of the entire stent. The proportions of cross-sections with heterogeneous intima in the entire stent was significantly higher in the VL-ISR group compared to the E-ISR group (60.5±28.5% versus 5.8±11.5%, P<0.0001), with heterogeneous intima being more frequently observed at the minimum lumen area site in the VL-ISR group (90.7% versus 17.9%, P<0.0001). Disrupted intima with cavity and intraluminal material also were observed more frequently in the VL-ISR group for the entire stent (18.6% versus 0%, 20.9% versus 2.6%, P<0.03) as well as at the minimum lumen area site (13.9% versus 0%,16.2% versus 0%, P<0.03). Conclusions— The morphological characteristics of restenotic tissue in VL-ISR were different from those in E-ISR and similar to atherosclerotic plaque. In BMS, progression of the atherosclerotic process within neointima after stent implantation may be associated with VL-ISR.

Prognostic value of coronary magnetic resonance angiography for prediction of cardiac events in patients with suspected coronary artery disease.

OBJECTIVES This study sought to determine whether whole-heart coronary magnetic resonance angiography (CMRA) can predict cardiac events in patients with suspected coronary artery disease. BACKGROUND Recent studies demonstrated that the presence of stenosis on coronary computed tomography angiography has a significant prognostic impact on the prediction of cardiac events. However, the prognostic value of whole-heart CMRA is unknown. METHODS We studied 207 patients with suspected coronary artery disease who underwent non-contrast-enhanced free-breathing whole-heart CMRA acquired with a 1.5-T MR system and 32-channel cardiac coils. The presence of significant coronary stenosis (≥50% diameter reduction) was visually determined on sliding thin- maximum intensity projection images. Follow-up information was obtained for occurrence of severe cardiac events (cardiac death, myocardial infarction, and unstable angina) and all cardiac events (additionally including revascularization>90 days after CMRA). RESULTS During a median follow-up of 25 months, 10 cardiac events, of which 5 were severe, were observed in 84 patients with significant stenosis. Whereas, in 123 patients without significant stenosis, only 1 cardiac event with no severe event was observed. Kaplan-Meier curves demonstrated a significant difference in event-free survival between the 2 groups for severe events (annual event rate, 3.9% and 0%, respectively; log-rank test, p = 0.003), as well as for all cardiac events (6.3% and 0.3%; p < 0.001). Cox regression analysis showed that presence of significant stenosis on CMRA was associated with a >20-fold hazard increase for all cardiac events (hazard ratio: 20.78; 95% confidence interval: 2.65 to 162.70; p = 0.001). CONCLUSIONS Whole-heart CMRA is useful for predicting the future risk for cardiac events in patients with suspected coronary artery disease.

Patients with a Hypertensive Response to Exercise Have Impaired Left Ventricular Diastolic Function

An exaggerated increase in systolic blood pressure prolongs myocardial relaxation and increases left ventricular (LV) chamber stiffness, resulting in an increase in LV filling pressure. We hypothesize that patients with a marked hypertensive response to exercise (HRE) have LV diastolic dysfunction leading to exercise intolerance, even in the absence of resting hypertension. We recruited 129 subjects (age 63±9 years, 64% male) with a preserved ejection fraction and a negative stress test. HRE was evaluated at the end of a 6-min exercise test using the modified Bruce protocol. Patients were categorized into three groups: a group without HRE and without resting hypertension (control group; n=30), a group with HRE but without resting hypertension (HRE group; n=25), and a group with both HRE and resting hypertension (HTN group; n=74). Conventional Doppler and tissue Doppler imaging were performed at rest. After 6-min exercise tests, systolic blood pressure increased in the HRE and HTN groups, compared with the control group (226±17 mmHg, 226±17 mmHg, and 180±15 mmHg, respectively, p<0.001). There were no significant differences in LV ejection fraction, LV end-diastolic diameter, and early mitral inflow velocity among the three groups. However, early diastolic mitral annular velocity (E′) was significantly lower and the ratio of early diastolic mitral inflow velocity (E) to E′ (E/E′) was significantly higher in patients of the HRE and HTN groups compared to controls (E′: 5.9±1.6 cm/s, 5.9±1.7 cm/s, 8.0±1.9 cm/s, respectively, p<0.05). In conclusion, irrespective of the presence of resting hypertension, patients with hypertensive response to exercise had impaired LV longitudinal diastolic function and exercise intolerance.

Impact of heart rate on mechanical dyssynchrony and left ventricular contractility in patients with heart failure and normal QRS duration

The quantification of mechanical dyssynchrony has important diagnostic value and may help to determine optimal therapy in heart failure (HF). We hypothesized that mechanical dyssynchrony may be augmented at increased heart rates in patients with HF and normal QRS duration.

Quantification of myocardial blood flow using model based analysis of first-pass perfusion MRI: extraction fraction of Gd-DTPA varies with myocardial blood flow in human myocardium.

For the absolute quantification of myocardial blood flow (MBF), Patlak plot‐derived K1 need to be converted to MBF by using the relation between the extraction fraction of gadolinium contrast agent and MBF. This study was conducted to determine the relation between extraction fraction of Gd‐DTPA and MBF in human heart at rest and during stress. Thirty‐four patients (19 men, mean age of 66.5 ± 11.0 years) with normal coronary arteries and no myocardial infarction were retrospectively evaluated. First‐pass myocardial perfusion MRI during adenosine triphosphate stress and at rest was performed using a dual bolus approach to correct for saturation of the blood signal. Myocardial K1 was quantified by Patlak plot method. Mean MBF was determined from coronary sinus flow measured by phase contrast cine MRI and left ventricle mass measured by cine MRI. The extraction fraction of Gd‐DTPA was calculated as the K1 divided by the mean MBF. The extraction fraction of Gd‐DTPA was 0.46 ± 0.22 at rest and 0.32 ± 0.13 during stress (P < 0.001). The relationship between extraction fraction (E) and MBF in human myocardium can be approximated as E = 1 − exp(−(0.14 × MBF + 0.56)/MBF). The current results indicate that MBF can be accurately quantified by Patlak plot method of first‐pass myocardial perfusion MRI by performing a correction of extraction fraction. Magn Reson Med, 2011.

Impact of Cholesterol Metabolism on Coronary Plaque Vulnerability of Target Vessels: A Combined Analysis of Virtual Histology Intravascular Ultrasound and Optical Coherence Tomography

OBJECTIVES The aim of this study was to evaluate the relationship between cholesterol metabolism and coronary plaque vulnerability. BACKGROUND Cholesterol homeostasis, defined as the balance between absorption and synthesis, influences the progression of coronary atherosclerosis. METHODS Consecutive stable angina pectoris patients (N = 80) not receiving any lipid-lowering therapy were divided into 2 groups based on the presence of in vivo thin cap fibroatheroma (TCFA) in de novo target vessels assessed by the combined use of virtual histology intravascular ultrasound and optical coherence tomography. RESULTS Patients with in vivo TCFA (n = 42) showed a higher campesterol-to-lathosterol ratio (3.36 [interquartile range, 2.10 to 4.26] vs. 1.50 [1.20 to 2.50], p < 0.0001). The campesterol-to-lathosterol ratio, low-density lipoprotein (LDL) cholesterol, and high-sensitivity C-reactive protein (hsCRP) were positively correlated with the percentage of necrotic core volume (r = 0.520, p < 0.0001; r = 0.520, p < 0.0001; and r = 0.539, p < 0.0001, respectively) and negatively correlated with thinnest fibrous cap thickness (r = -0.566, p < 0.0001; r = -0.530, p < 0.0001; and r = -0.358, p = 0.007, respectively) . The independent predictors of the incidence of TCFA were the campesterol-to-lathosterol ratio (odds ratio: 3.989, 95% confidence interval: 1.688 to 9.428; p = 0.002), LDL cholesterol (odds ratio: 1.425, 95% confidence interval: 1.023 to 1.985; p = 0.03), hsCRP (odds ratio: 1.025, 95% confidence interval: 1.003 to 1.047; p = 0.02), and the percentage of necrotic core volume (odds ratio:1.084, 95% confidence interval: 1.012 to 1.161; p = 0.02). CONCLUSIONS Enhanced absorption and reduced synthesis of cholesterol may be related to coronary plaque vulnerability.