Akira Koike

A new echocardiographic method for identifying vortex flow in the left ventricle: numerical validation.

A new mathematical method for estimating velocity vectors from color Doppler datasets is proposed to image blood flow dynamics; this method has been called echodynamography or vector flow mapping (VFM). In this method, the concept of stream function is exploited to expand a 2-D distribution of radial velocities in polar coordinates, observed with color Doppler, to a 2-D distribution of velocity vectors. This study was designed to validate VFM using 3-D numerical flow models. Velocity fields were reconstructed from the virtual color Doppler datasets derived from the models. VFM captured the gross features of flow structures and produced comparable images of the distribution of vorticity, which correlated significantly with the original field (for velocity magnitudes, standard error of estimate = 0.003 to 0.007 m/s; for vorticity, standard error of estimate = 0.35 to 2.01/s). VFM may be sensitive for depicting flow structures derived from color Doppler velocities with reasonable accuracy.

Heart rate and blood pressure response to ramp exercise and exercise capacity in relation to age, gender, and mode of exercise in a healthy population.

BACKGROUNDnThe responses of heart rate (HR) and blood pressure to the ramp exercise test are not known and the current understanding of peak oxygen uptake and anaerobic threshold (AT) values in the normal Japanese population is insufficient.nnnMETHODS AND RESULTSnA total of 749 healthy Japanese subjects aged 20-78 years underwent a cardiopulmonary exercise test using a cycle ergometer or treadmill ergometer with ramp protocols. HR, systolic blood pressure (SBP), and oxygen uptake VO2 at rest, at AT, and at peak exercise were determined. HR and SBP at peak exercise in a cycle ergometer and treadmill ergometer test decreased with age. Work rate at peak exercise in a cycle ergometer increased with body weight and decreased with age. VO2 at AT and at peak exercise were higher in treadmill ergometer testing than in cycle ergometer testing, and were not affected by exercise protocol. Both of these decreased with age.nnnCONCLUSIONSnThe normal responses of HR and SBP to ramp exercise testing are reported for the first time. AT, peak VO2, and VO2 at each stage are shown for a healthy population. Some of these parameters were influenced by weight, gender, and age, as well as mode of exercise and the protocol used. These results provide useful reference values for interpreting the results of cardiopulmonary exercise testing.

A New Scoring System for Evaluating the Risk of Heart Failure Events in Japanese Patients With Atrial Fibrillation

Risk stratification for heart failure (HF) in patients with atrial fibrillation (AF) has not been well established. The aim of this study was to identify the predictors of HF events in patients with AF, consequently developing a new risk-scoring system that stratifies the risk for HF events. In this prospective, single hospital-based cohort, all patients who presented from July 2004 to March 2010 were registered (Shinken Database 2004-2009). Follow-up was maintained by being linked to the medical records or by sending study documents of prognosis. Of the 13,228 patients in the Shinken Database 2004-2009, 1,942 patients with AF were identified. Of the patients with AF, HF events (hospitalization or death from HF) occurred in 147 patients (7.6%) during a mean follow-up period of 776 ± 623 days. After identifying the parameters that were independently associated with the incidence of HF events (coexistence of organic heart diseases, anemia [hemoglobin level <11 g/dl], renal dysfunction [estimated glomerular filtration rate <60 ml/min/m(2)], diabetes mellitus, and the use of diuretics), a new scoring system was developed, the H(2)ARDD score (heart diseases = 2 points, anemia = 1 point, renal dysfunction = 1 point, diabetes = 1 point, and diuretic use = 1 point; range 0 to 6 points). This scoring system discriminated the low- and high-risk populations well (incidence in patients scoring 0 and 6 points of 0.2% and 40.8% per patient-year, respectively) and showed high predictive ability (area under the curve 0.840, 95% confidence interval 0.803 to 0.876). In conclusion, the new H(2)ARDD score may help identify the population of patients with AF at high risk for HF events.

Estimated glomerular filtration rate and proteinuria are associated with persistent form of atrial fibrillation: Analysis in Japanese patients

BACKGROUNDnSeveral reports have identified that decline in renal function and presence of proteinuria are closely associated with incidence of atrial fibrillation (AF). However, it is still unclear whether these kidney-related markers are associated with the progression of AF from paroxysmal to persistent form.nnnMETHODS AND RESULTSnAmong the new patients who visited the Cardiovascular Institute Hospital between 2004 and 2010 (Shinken Database 2004-2010, n=15,227), both estimated glomerular filtration rate (eGFR) and proteinuria were measured in 1074 AF patients (paroxysmal/persistent 579/495, respectively), who were divided into tertiles of eGFR (the borderlines were 60.07 and 73.67 ml[min(-1)]1.73[m(-2)], respectively), and then further divided into the two categories with/without proteinuria. The average value of eGFR was lower (63.1 ml[min(-1)]1.73[m(-2)] vs. 68.8 ml[min(-1)]1.73[m(-2)], p<0.001) and the detection rate of proteinuria was higher (13.7% vs. 8.5%, p=0.006) in patients with persistent AF than in those with paroxysmal AF, respectively. In the multivariate analysis without parameters of echocardiography [left ventricular ejection fraction (LVEF) and left atrial dimension (LAD)], both eGFR and proteinuria were independently associated with persistent AF, but the association was abolished when the model included LAD and LVEF.nnnCONCLUSIONSnIn the present analysis with cross-sectional design, both eGFR and proteinuria were apparently linked to the persistent form of AF, but their role in the pathogenesis does not seem to exceed the atrial stretch and remodeling, represented by LAD and LVEF.

In vivo evaluation of fibrous cap thickness by optical coherence tomography for positive remodeling and low-attenuation plaques assessed by computed tomography angiography

BACKGROUNDnCoronary plaques with positive remodeling (PR) and low-attenuation plaques (LAP) by computed tomography angiography (CTA) might be associated with plaque vulnerability. The purpose of this study was to assess the relation between coronary plaques with PR and LAP by CTA and fibrous cap thickness measured by optical coherence tomography (OCT).nnnMETHODSnWe used CTA and OCT to assess 102 coronary plaques in patients with coronary artery disease (unstable angina pectoris, n=24; stable angina pectoris, n=78). Plaque characteristics were divided into three groups: 2-feature-positive plaques (PR and LAP; n=32), 1-feature-positive plaques (PR or LAP; n=20), and 2-feature-negative plaques (neither PR nor LAP; n=50). PR was defined as remodeling index (RI) of >1.05 and LAP was defined as CT density value <50HU.nnnRESULTSnThere were significant differences between the three plaque groups with respect to fibrous cap thickness measured by OCT: 76±24μm in 2-feature-positive plaques, 154±51μm in 1-feature-positive plaques, and 192±49μm in 2-feature-negative plaques (P<0.001). The RI (1.21±0.06, 1.14±0.05, P=0.011) and the presence of thin cap fibroatheroma (TCFA) (<70-μm thickness) (75%, 15%, P=0.001) were significantly higher in UAP than in SAP patients with 2-feature-positive plaques, whereas fibrous cap thickness (68.9±24.1, 92.1±21.9μm, P<0.001) was lower in the UAP patients. In UAP patients, the presence of ring-like enhancement showed higher accuracy of 88% for detection of TCFA.nnnCONCLUSIONSnCoronary PR and LAP by CTA were associated with the degree of fibrous cap thickness measured by OCT. CTA can non-invasively provide promising information on plaque vulnerability by identifying coronary plaque with PR and LAP, especially ring-like enhancement.

Prognostic value of end-tidal CO2 pressure during exercise in patients with left ventricular dysfunction

We compared the prognostic power of end-tidal CO2 pressure (PETCO2) during exercise, an index of arterial CO2 pressure, with those of established respiratory gas indexes during exercise testing in patients with left ventricular dysfunction. Seventy-eight consecutive patients with a left ventricular ejection fraction (LVEF) ≤40% were enrolled in the study. All the patients performed a symptom-limited incremental exercise test with respiratory gas measurements. PETCO2 at peak exercise, peak O2 uptake (

Determination of the VE/VCO2 Slope from a Constant Work-Rate Exercise Test in Cardiac Patients

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Mechanisms that modulate peripheral oxygen delivery during exercise in heart failure

O2), the ratio of the increase in ventilation to the increase in CO2 output (