Daisuke Ogasawara

Feasibility of combined use of intravascular ultrasound radiofrequency data analysis and optical coherence tomography for detecting thin-cap fibroatheroma

AIMS To evaluate the feasibility of the combined use of virtual histology (VH)-intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for detecting in vivo thin-cap fibroatheroma (TCFA). METHODS AND RESULTS In 56 patients with angina, 126 plaques identified by IVUS findings were analysed using both VH-IVUS and OCT. IVUS-derived TCFA was defined as an abundant necrotic core (>10% of the cross-sectional area) in contact with the lumen (NCCL) and %plaque-volume >40%. OCT-derived TCFA was defined as a fibrous cap thickness of <65 microm overlying a low-intensity area with an unclear border. Plaque meeting both TCFA criteria was defined as definite-TCFA. Sixty-one plaques were diagnosed as IVUS-derived TCFA and 36 plaques as OCT-derived TCFA. Twenty-eight plaques were diagnosed as definite-TCFA; the remaining 33 IVUS-derived TCFA had a non-thin-cap and eight OCT-derived TCFA had a non-NCCL (in discord with NCCL visualized by VH-IVUS, mainly due to misreading caused by dense calcium). Based on IVUS findings, definite-TCFA showed a larger plaque and vessel volume, %plaque-volume, higher vessel remodelling index, and greater angle occupied by the NCCL in the lumen circumference than non-thin-cap IVUS-derived TCFA. Conclusion Neither modality alone is sufficient for detecting TCFA. The combined use of OCT and VH-IVUS might be a feasible approach for evaluating TCFA.

Local Determinants of Thrombus Formation Following Sirolimus-Eluting Stent Implantation Assessed by Optical Coherence Tomography

OBJECTIVES We conducted this study to assess the prevalence and determinants of subclinical thrombus after sirolimus-eluting stent (SES) implantation. BACKGROUND Angioscopic analyses have demonstrated the presence of thrombus is more common than the clinical incidence of SES thrombosis. METHODS Fifty-three patients (53 lesions) underwent 6-month follow-up optical coherence tomography. A stent eccentricity index ([SEI] minimum/maximum stent diameter) was determined in each cross section. To evaluate unevenness of neointimal thickness, a neointimal unevenness score ([NUS] maximum neointimal thickness in the cross section/average neointimal thickness of the same cross section) was calculated for each cross section. Average SEI and NUS were calculated for each stent. Major adverse cardiac events were defined as a composite of death, myocardial infarction, and target vessel revascularization. RESULTS Fourteen cases of thrombus (26%) were detected by optical coherence tomography (thrombus: n = 14 vs. nonthrombus: n = 39). The percentage of thrombus was associated with longer stents (36.4 +/- 20.2 mm vs. 25.1 +/- 9.8 mm; p = 0.008), a larger number of uncovered struts (17 +/- 16 vs. 8 +/- 11; p = 0.03), smaller average SEI (0.89 +/- 0.04 vs. 0.92 +/- 0.03; p = 0.001), and greater average NUS (2.22 +/- 0.24 vs. 2.00 +/- 0.33; p = 0.03). A significant relationship existed between average SEI and average NUS (p < 0.0001, R = 0.68), and between average SEI and the number of uncovered struts (p < 0.0006, R = 0.46). There was no significant difference in major adverse cardiac events during follow-up (median: 485 days, 7.1% vs. 12.8%; p > 0.99). CONCLUSIONS Longer stents and greater asymmetric stent expansion may be important determinants of thrombus formation after SES implantation. In this small cohort, the presence of thrombus did not increase the risk of major adverse cardiac events.

Delayed Neointimalization on Sirolimus-Eluting Stents : 6-Month and 12-Month Follow up by Optical Coherence Tomography

BACKGROUND Sirolimus-eluting stents (SES) have incomplete neointimal coverage at 6-month follow up as determined with optical coherence tomography (OCT). The long-term detailed changes of neointima in SES remains to be clarified. METHODS AND RESULTS Serial changes in neointimal coverage of SES from 6 months to 12 months using OCT were examined. Of 21 SES in 13 patients, OCT was used to visualize 2,321 stent struts at 6 months and 2,285 stent struts at 12 months. The frequency of struts without neointimal coverage decreased from 6 months to 12 months (from 10.4 to 5.7%). The frequency of malapposed struts decreased from 6 months to 12 months (from 1.7 to 0.2%). The average thickness of the neointima increased (from 112 +/-123 to 120 +/-130 microm). The frequency of struts located at the side branch orifice without neointima decreased (from 4 out of 17 (24%) to 0 out of 17 (0%)). Complete coverage with neointima was observed in 14% (3 of 21 SES) at 6 months, and 24% (5 of 21 SES) at 12 months. CONCLUSIONS Additional neointimal coverage was observed between 6 and 12 months, with a small increase in the neointimal thickness. The incidence of complete coverage, however, was still low at 12 months. These findings suggest delayed neointimalization on SES.

Very late thrombosis of sirolimus-eluting stent due to late malapposition: Serial observations with optical coherence tomography

A 54 years old man underwent directional coronary atherectomy in segment 7 with a partial deep-cut injury. A sirolimus-eluting stent (SES) was implanted at the restenosed post-atherectomy lesion. Six months after SES implantation, intravascular ultrasound (IVUS) examination revealed slight vessel enlargement although there were no malapposed struts. Optical coherence tomography (OCT) revealed partial stent malapposition. Ticlopidine was discontinued 3 months after SES implantation, but aspirin was continued. Twenty-nine months after SES implantation, after discontinuing aspirin for 7 days for colon polypectomy, the patient suffered an acute myocardial infarction at the SES implantation site. IVUS revealed further positive vessel remodeling and slight stent malapposition and OCT revealed extension of the previous stent malapposition and ulcer-like appearance around the stent struts. This case demonstrates that even a small partial SES malapposition that can be detected only by OCT has the potential to enlarge over time and the late malapposition may result in late thrombosis when anti-platelet therapy is discontinued.

Impedance Cardiography for Cardiac Output Estimation

everal studies suggest the importance of cardiac power output calculation, which is derived from cardiac output (CO) and mean blood pressure, to predict the prognosis in heart failure patients not only in hospital but also in the outpatient setting.1–3 CO measured by the thermodilution method with a Swan-Ganz catheter placed in the pulmonary artery has become one of the most widely accepted and used methods of monitor cardiac function, despite its certain limitations. 1,3,4 A noninvasive and low cost method for measuring CO would be relevant for the widespread clinical use of cardiac power output. Some noninvasive techniques of measuring CO have been proposed over the past years. The indirect Fick method of re-breathing carbon dioxide5,6 and Doppler flow measurement of the left ventricular outflow tract have been shown to be accurate;7 however, their applications require expensive equipments and trained operators. Other promising results have been observed with devices based on electrical bioimpedance technology,8 and 2 basic technologies of impedance cardiography (ICG) are currently in use. The first is called whole-body ICG9,10 (ICGWB), which was introduced in 1948,11 in which the electrodes are placed on the distal portion of the limbs. The second one is thoracic ICG (ICGT), which was introduced in 1964, and the electrodes are placed on the root of the neck and on the lower chest. When the CO is measured in subjects with healthy hearts, the results from both these technologies are usually reliable, but the reliability of CO measurements taken by ICGT is compromised in patients with cardiac diseases.12–16 According to the Food and Drug Administration (FDA) standard of bio-equivalence,17 the disparity between 2 techCirc J 2006; 70: 1164–1168

Predictive importance of left ventricular myocardial stiffness for the prognosis of patients with congestive heart failure

OBJECTIVES This study was designed to determine the prognostic importance of left ventricular (LV) myocardial stiffness, a hemodynamic index which is closely related to B-type natriuretic peptide (BNP) concentration in patients with congestive heart failure (CHF). BACKGROUND While elevated BNP, an abnormality of cardiac neurohormones, is known to be an independent marker of death or re-admission, it remains to be clarified whether there is also a strong predictor directly related to cardiac dysfunction. METHODS LV performance variables and stress-strain analyses including diastolic myocardial stiffness constant (K(m)) were obtained from 37 patients with initial CHF by the combined simultaneous measurement of echocardiographic and hemodynamic data. Survivors were monitored for a mean of 23 months, with the main endpoint being combined death or first re-admission for CHF. RESULTS Ten patients (27%) were primary endpoint cases. Both K(m) and plasma BNP levels were higher in the event than in the event-free group. By Cox proportional hazards analysis, K(m)≥4.0 was identified as the only variable with significant and independently incremental predictive power to affect the primary endpoint (adjusted hazard ratio=7.354, 95% confidence interval 1.379-39.232, p=0.02). CONCLUSIONS In patients with CHF, increased myocardial stiffness may have greater prognostic significance compared to other conventional predictors. Increased myocardial stiffness may be considered to be an important prognostic factor independent of the loading conditions.

Effects of human atrial natriuretic peptide on myocardial performance and energetics in heart failure due to previous myocardial infarction.

BACKGROUND Human atrial natriuretic peptide (hANP) and spontaneous nitric oxide (NO) donor share cyclic guanosine monophosphate (cGMP) as a second messenger, but their effect on myocardium may differ. We compared the effect of hANP and sodium nitroprusside (SNP) on left ventricular (LV) mechano-energetics in heart failure (HF). METHODS Ten patients with HF due to previous myocardial infarction (LV ejection fraction: 45±3%) were instrumented with conductance and coronary sinus thermodilution catheters. LV contractility (Ees: slope of end-systolic pressure-volume relation) and the ratio of LV stroke work (SW) to myocardial oxygen consumption (SW/MVO2=mechanical efficiency) were measured in response to intravenous infusion of ANP (0.05 μg/kg/min) or SNP (0.3 μg/kg/min) to lower blood pressure by at least 10 mmHg, and changes in plasma cGMP. RESULTS SNP had no effect on Ees, SW, or MVO2, thus SW/MVO2 remained unchanged (40.54±5.84% to 36.59±5.72%, p=0.25). ANP increased Ees, and decreased MVO2 with preserved SW, resulting in improved SW/MVO2 (40.49±6.35% to 50.30±7.96%, p=0.0073). Infusion of ANP (10.42-34.95 pmol/ml, p=0.0003) increased cGMP levels, whereas infusion of SNP had no effect (10.42-12.23 pmol/ml, p=0.75). CONCLUSIONS Compared to SNP, the ANP-dependent increase in cGMP may ameliorate myocardial inotropy and energetics in HF.