Biomedical subjects
Hiroki Sugihara
Publications and source records attributed to Hiroki Sugihara.
Images in cardiovascular medicine. Rapid progression of left ventricular hypertrophy.
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Adaptive filtering enhances information transmission in visual cortex.
Sensory neuroscience seeks to understand how the brain encodes natural environments. However, neural coding has largely been studied using simplified stimuli. In order to assess whether the brain's coding strategy depends on the stimulus ensemble, we apply a new information-theoretic method that allows unbiased calculation of neural filters (receptive fields) from responses to natural scenes or other complex signals with strong multipoint correlations. In the cat primary visual cortex we compare responses to natural inputs with those to noise inputs matched for luminance and contrast. We find that neural filters adaptively change with the input ensemble so as to increase the information carried by the neural response about the filtered stimulus. Adaptation affects the spatial frequency composition of the filter, enhancing sensitivity to under-represented frequencies in agreement with optimal encoding arguments. Adaptation occurs over 40 s to many minutes, longer than most previously reported forms of adaptation.
Resting ST-segment depression predicts exercise-induced subendocardial ischemia in patients with hypertrophic cardiomyopathy.
BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) sometimes display characteristic electrocardiographic (ECG) findings at rest and develop subendocardial ischemia during exercise in the absence of coronary lesions. However, their relationship has not yet been fully clarified. METHODS: Exercise Tc-99m-tetrofosmin myocardial scintigraphy was performed in 48 patients with non-obstructive HCM. We quantified transient left ventricular cavity dilation (LVCD) on exercise scintigrams, a parameter of subendocardial ischemia, and correlated the results with the ECG findings at rest and during exercise. RESULTS: Transient LVCD occurred during exercise in 17 (35%) patients with HCM. Hemodynamic parameters during exercise did not differ between HCM patients with and without transient LVCD. Multiple logistic regression analysis showed that transient LVCD was significantly associated with ST-segment depression at rest (chi2=5.00, odds ratio=5.70, 95% confidence intervals 1.24-26.18, P=0.025) and a greater total number of leads with resting ST-segment depression (chi2=6.38, odds ratio=1.60, 95% confidence intervals 1.12-2.42, P=0.012). The degree of LVCD was correlated with the total number of leads with ST-segment depression at rest (P=0.002); the optimal cutoff for the diagnosis of transient LVCD was 3 with a sensitivity of 65%, a specificity of 90%, and an accuracy of 81%. CONCLUSIONS: In patients with HCM, ST-segment depression at rest was accompanied by exercise-induced subendocardial perfusion abnormality as detected by myocardial scintigraphy. ST-segment depression at rest suggests that the subendocardium is predisposed to exertional ischemia.
Systolic outward motion of the left ventricular apical wall as detected by magnetic resonance tagging in patients with apical hypertrophic cardiomyopathy.
Patients with apical hypertrophic cardiomyopathy (APH) associated with paradoxic jet flow (ie, diastolic flow away from the apex) may gradually develop an apical aneurysm, which often leads to arrhythmia and mural thrombus formation. We observed systolic outward motion of the left ventricular apical myocardium in patients with APH using a magnetic resonance tagging procedure and examined the relationship of the outward motion to echocardiographic and scintigraphic findings and to cardiac events. Systolic displacement of the myocardial tags of the apical region perpendicular to the long axis in the 4-chamber view was recorded in 31 patients with APH. Of these patients, 14 showed no outward movement of tags (group A), and 17 showed outward movement (group B). In group B, apical hypertrophy was more severe (35 +/- 7 mm vs. 29 +/- 6 mm, p < 0.05), paradoxic jet flow was more frequent (64% vs. 14%, p < 0.05) and the defect score in I-123-beta-methyliodophenylpentadecanoic acid scintigraphy was higher (2.1 +/- 0.7 vs. 1.3 +/- 0.7, p < 0.01). During a mean follow-up period of 55 months, only 1 patient experienced paroxysmal atrial fibrillation in group A. In group B, 1 patient died suddenly, 1 was admitted to hospital because of congestive heart failure, 2 developed angina pectoris, 2 exhibited non-sustained ventricular tachycardia, and 1 showed multifocal premature ventricular contraction; in these 7 patients the outward movement was greater than in the 10 patients in Group B who had no cardiac events (1.00 +/- 0.59 vs. 0.52 +/- 0.40, p < 0.05). Hence, our results show that outward tag displacement is frequently associated with severe apical hypertrophy, paradoxic jet flow, apical ischemia, and cardiac events. The tagging method may be useful in assessing the severity of APH and predicting the occurrence of cardiac events at an early stage.
Coronary artery spasm as a cause of droperidol-induced ventricular fibrillation.
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[Brain natriuretic peptide and QRS duration as a predictor for cardiac events in patients with heart failure].
OBJECTIVES: Brain natriuretic peptide (BNP) and QRS duration have been reported as independent predictors for cardiac events in patients with heart failure. The present study investigated the relationships between BNP and QRS duration to assess the prognostic value in patients with heart failure. METHODS: We prospectively examined 93 patients presenting to our emergency department with heart failure between April 2000 and April 2003 (age 69 +/- 13 years, 53 males, 40 females). BNP level and QRS duration were measured after treatment for heart failure. The efficacy end point was the composite incidence of sudden death, death for progressive heart failure, or readmission for worsening heart failure. RESULTS: During the mean follow-up period of 720 +/- 470 days, cardiac events occurred in 35 patients (sudden death in 6, death for progressive heart failure in 9, and readmission for worsening heart failure in 20). BNP level was almost equally higher in the three groups with cardiac events (mean +/- SEM; sudden death: 348 +/- 128 pg/ml, death for progressive heart failure: 390 +/- 97 pg/ml, readmission for worsening heart failure: 354 +/- 79 pg/ml) than in patients without cardiac events (213 +/- 34 pg/ml). In contrast, QRS duration was exclusively prolonged in patients with sudden death(mean +/- SEM, 125 +/- 10 msec) compared with the remaining three groups (death for progressive heart failure: 100 +/- 5 msec, readmission for worsening heart failure: 103 +/- 4 msec, no cardiac events: 108 +/- 3 msec). No relationship was found between BNP level and QRS duration in all patients with heart failure (Spearman r = 0.13, p = 0.22). CONCLUSIONS: Increased BNP level was associated with poor prognosis irrespective of mode of cardiac events, and prolonged QRS duration was related to sudden death in our cohort with heart failure. The combination of BNP level and QRS duration may have adjunctive value in predicting the prognosis in patients with heart failure.
A case of ST-segment elevation provoked by distended stomach conduit.
A case of ST-segment elevation provoked by distended stomach conduit is presented. An 83-year-old woman was admitted to our hospital with worsening chest discomfort. She had a previous history of subtotal esophagectomy, which was reconstructed using a stomach conduit in the posterior mediastinum. Electrocardiogram showed ST-segment elevation in the inferior leads and a prominent negative P wave in lead V1. Echocardiography demonstrated normal left ventricular function without regional wall motion abnormality; however, the left atrium and ventricle compressed by a substantially distended stomach conduit was noted. Subsequent angiocardiography revealed no coronary atherosclerotic stenosis and normal contractility of the left ventricle. Chest symptoms resolved soon after nasogastric suction, leading to resolution of electrocardiographic changes. The stomach conduit diminished on following repeated echocardiography. The patient was discharged without any evidence of myocardial infarction. Esophagus disease of the reconstructed stomach conduit should be recognized as a rare but considerable cause for electrocardiographic changes.
Short-term fluctuations in sinus cycle length after premature ventricular beats in patients with hypertrophic cardiomyopathy and myocardial infarction.
BACKGROUND: Sinus cycle length has been reported to fluctuate after a ventricular premature beat (VPB). The purpose of this study was to assess the short-term fluctuations of sinus cycle length in patients with hypertrophic cardiomyopathy (HCM) and prior myocardial infarction (MI). METHODS: The relative deviation of RR intervals from the mean of the last two RR intervals preceding a VPB were calculated during the 20 subsequent beats following the VPB from Holter recordings in 92 patients with non-obstructive HCM, 57 patients with prior MI and 54 healthy controls. RESULTS: In controls, the deviations of the RR intervals were negative for several beats after a VPB and subsequently changed to positive before returning to the baseline. Similar changes in RR intervals following a VPB were exhibited in HCM patients; however, the late positive deviations of RR intervals were more marked than in controls. By contrast, in patients with prior MI, the early negative deviations of RR intervals were smaller compared with controls, and the deviations returned to the baseline without incidence of the positive changes. CONCLUSIONS: Short-term fluctuations in sinus cycle length after a VPB differed exclusively among HCM patients, prior MI patients, and healthy controls.
Heart rate variability in adult patients with isolated left ventricular noncompaction.
BACKGROUND: Isolated left venticular noncompaction (IVNC) is a rare congenital heart disease charactrized by a pattern of an excessively prominent trabecular meshwork with deep intertrabecular recesses. Heart rate variability (HRV) has been reported to be impaired in various heart diseases, though little is known regarding HRV in adult patients with IVNC. METHODS: We measured spectral components of HRV using fast Fourier transformation of 24-h Holter recordings in 10 adult patients with IVNC, 40 patients with myocardial infarction (MI), 40 patients with hypertrophic cardiomyopathy (HCM) and 40 healthy controls. RESULTS: The low frequency component and the high frequency component of HRV were lower in IVNC patients tahn those in controls (265 +/- 213 ms(2) vs. 469 +/- 195 ms(2), p < 0.01; 80 +/- 51 ms(2) vs. 185 +/- 126 ms(2), p < 0.01). Furthermore, 3 IVNC patients with a previous history of heart failure exhibited more decreased HRV (low frequency, 75 +/- 56 ms(2); high frequency, 39 +/- 18 ms(2)). Contrary, the ratio of low frequency to high frequency component was higher in patients with IVNC than controls (3.5+/-0.5 vs. 3.2 +/- 0.3, p < 0.05). The degree of impaired HRV was severest in MI patients, intermediate in IVNC patients and mildest in HCM patients compared with controls. CONCLUSIONS: HRV is impaired in adult patients with IVCN, especially in patients with a previous history of heart failure, suggesting vagal withdrawal or sympathetic enhancement. HRV in IVNC adults is less impaired than in MI patients, and more impaired than in HCM patients of our cohort.
Assessment of Takotsubo cardiomyopathy (transient left ventricular apical ballooning) using 99mTc-tetrofosmin, 123I-BMIPP, 123I-MIBG and 99mTc-PYP myocardial SPECT.
UNLABELLED: We compared Takotsubo cardiomyopathy (transient left ventricular apical ballooning) with acute myocardial infarction (AMI) using two-dimensional echocardiography, 99mTc-tetrofosmin, 99mTc-PYP, 123I-BMIPP and 123I-MIBG myocardial SPECT. METHODS: We examined 7 patients with Takotsubo cardiomyopathy and 7 with AMI at the time of emergency admission (acute phase), and 2-14 days (subacute phase), one month (chronic phase), and 3 months (chronic II phase) after the attack. The left ventricle was divided into nine regions on echocardiograms and SPECT images, and the degree of abnormalities in each region was scored according to five grades from normal (0) to severely abnormal (4). RESULTS: Coronary angiography showed the absence of stenotic regions in patients with Takotsubo cardiomyopathy, and severely stenotic and/or occlusive lesions in patients with AMI. The total ST segment elevation on electrocardiograms (mm) was 7.8 +/- 3.7 in those with Takotsubo cardiomyopathy, and 7.3 +/- 3.9 in patients with AMI. Abnormal wall motion scores on echocardiograms were 14.2 +/- 4.6, 4.7 +/- 4.0, 1.7 +/- 2.0 and 0.5 +/- 0.4 during the acute, subacute, chronic and chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 14.0 +/- 4.3, 11.4 +/- 3.9, 8.8 +/- 3.6 and 5.2 +/- 4.8 in those with AMI. Abnormal myocardial perfusion scores on 99mTc-tetrofosmin images were 11.8 +/- 3.5, 3.2 +/- 3.0, 0.5 +/- 1.2 and 0.2 +/- 0.4 during the acute, subacute, chronic and chronic II phases, in patients with Takotsubo cardiomyopathy, and 16.2 +/- 4.3, 13.9 +/- 4.6, 7.9 +/- 4.6 and 5.0 +/- 4.5, respectively, in those with AMI. Abnormal myocardial fatty acid scores on 123I-BMIPP images were 12.6 +/- 3.7, 6.8 +/- 3.2 and 0.4 +/- 0.6 during the subacute, chronic and chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 16.5 +/- 5.1, 14.7 +/- 4.8 and 7.5 +/- 4.5 in those with AMI. Abnormal myocardial sympathetic nerve function scores on 123I-MIBG images were 14.8 +/- 4.0, 8.8 +/- 4.0 and 0.4 +/- 0.6 during the subacute, chronic, chronic II phases, respectively, in patients with Takotsubo cardiomyopathy, and 18.6 +/- 6.5, 16.8 +/- 6.8 and 12.9 +/- 5.2 in those with AMI. Myocardial 99mTc-PYP uptake was abnormal not only in patients with AMI but also in those with Takotsubo cardiomyopathy during the acute phase. CONCLUSIONS: Takotsubo cardiomyopathy might represent a stunned myocardium caused by a disturbance of the coronary microcirculation.
Association between plasma lipoprotein(a) concentration and restenosis after stent implantation.
BACKGROUND: The plasma concentration of lipoprotein (a) [Lp(a)] is associated with atherosclerotic and thrombotic vascular diseases. The aim of the present study was to evaluate the association between plasma Lp(a) concentration and in-stent restenosis. METHODS AND RESULTS: One hundred and 9 patients with successful elective coronary stent implantation underwent follow-up angiography at 24+/-6 weeks. Restenosis after stent implantation occurred in 38 patients. Univariate analysis showed that the reference diameter of the lesion was smaller in the restenosis group (2.93+/-0.29 mm) than in the no-restenosis group (3.21+/-0.43 mm) (p < 0.05). The lesion was longer in the restenosis group (14.2+/-5.3 mm) than in the no-restenosis group (11.6+/-4.9 mm) (p < 0.05). Plasma Lp(a) concentrations in the restenosis group (30.5+/-23.9 mg/dl) were higher than in the no-restenosis group (16.9+/-11.1 mg/dl) (p < 0.01). Other lipid concentrations were similar in both groups. Among the plasma Lp(a) concentrations, the rate of restenosis (71.4%) in the high Lp(a) group (> 40 mg/dl) (n = 14) was greater compared with the other groups: 33.3% in the intermediate Lp(a) group (10-40 mg/dl) (n = 54), and 24.4% in the low Lp(a) group (< 10 mg/dl) (n = 41) (p < 0.01). The late loss (0.57+/-0.53 mm) in the low Lp(a) group was significantly less than the other groups: 0.88+/-0.47 mm in the intermediate Lp(a) group, and 1.08+/-0.56 mm in the high Lp(a) group (p < 0.05). In a multivariate regression model, plasma Lp(a) concentration remained significant as an independent predictor of restenosis in patients undergoing stent implantation (p = 0.020 odds ratio (OR) 1.37 95%conficence interval (CI) 1.050-1.793), although the reference diameter (p = 0.025 OR 0.23 95%CI 0.061-0.830) and lesion length (p = 0.021 OR 1.12 95%CI 1.017-1.232) were related to stent restenosis. CONCLUSIONS: Plasma Lp(a) concentration is an independent predictor of stent restenosis.
The association between cholesterol and mortality in heart failure. Comparison between patients with and without coronary artery disease.
Hypercholesterolemia is a risk factor for development of coronary artery disease (CAD), however, several reports have suggested that low serum cholesterol is associated with a worse prognosis in patients with congestive heart failure (CHF). The objective of this study was to determine the prognostic value of cholesterol for CHF. The study subjects consisted of 133 consecutive patients hospitalized in our institution for progressive heart failure from April 2000 to March 2003. Thirty-two percent of the patients had CAD. After improvement of congestive heart failure and discharge from the hospital, lipid profiles, including serum total cholesterol (TC), triglycerides, and high and low density lipoprotein cholesterol (HDL, LDL, respectively), were obtained. During the follow-up period (2.3 +/- 0.9 years), 21 patients died. There was a significant difference between survivors and nonsurvivors in HDL (53 +/- 15, 43 +/- 15 mg/dL, P = 0.01), but no differences were observed in other variables. In patients with CAD, survivors had significantly lower TC concentrations (179 +/- 30 versus 246 +/- 55 mg/dL, P = 0.004), although in patients without CAD, survivors had significantly higher TC concentrations (203 +/- 37 versus 170 +/- 40 mg/dL, P = 0.02). Multivariate analysis showed high TC predicted a worse outcome in patients with CAD (odds ratio (OR) = 1.052, 95% confidence interval (CI) 1.002-1.104, P = 0.04), but a better outcome in patients without CAD (OR = 0.972, 95% CI 0.948-0.997, P = 0.03), independent of age, gender, medication, and complications. Thus, low serum cholesterol is associated with an improved outcome in patients with CAD, while it predicts a worse outcome in patients without CAD.
Reduced left ventricular ejection fraction in an 82-year-old woman with aortic stenosis.
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[Exercise-induced ST-segment depression and myocardial ischemia in patients with hypertrophic cardiomyopathy: myocardial scintigraphic study].
OBJECTIVES: Patients with hypertrophic cardiomyopathy (HCM) sometimes develop myocardial ischemia during exercise in the absence of coronary lesions. The relationship between myocardial ischemia and ST-segment depression was investigated during exercise testing in patients with HCM. METHODS: Regional hypoperfusion and/or transient left ventricular cavity dilation, a parameter of subendocardial hypoperfusion, were assessed on exercise 99mTc-tetrofosmin myocardial scintigraphy in 42 patients with non-obstructive HCM. The scintigraphic results were further correlated with the ST-segment responses to exercise. RESULTS: Regional hypoperfusion or transient left ventricular cavity dilation were observed in 19 (45%) or 16(38%)patients with HCM, respectively. The incidence of ST-segment depression > or = 0.1 mV during exercise testing was similar in HCM patients with regional hypoperfusion, with transient left ventricular cavity dilation, and without hypoperfusion (42%, 38%, 38%, p = 0.95). Furthermore, exercise-induced ST-segment depression > or = 0.1 mV occurred similarly irrespective of symptoms, exercise tolerance, the degree or the site of hypertrophy, or the presence or absence of resting ST-segment depression. CONCLUSIONS: ST-segment depression during exercise testing was common in patients with HCM, but seems to be an unreliable marker of myocardial ischemia as assessed by exercise scintigraphy.
Very low frequency power of heart rate variability is a powerful predictor of clinical prognosis in patients with congestive heart failure.
BACKGROUND: The present study examined whether the very low frequency (VLF) power of heart rate variability (HRV) is predictive of clinical prognosis in patients with congestive heart failure (CHF). METHOD AND RESULTS: The study recruited 54 consecutive CHF patients with emergency admission because of exacerbation of pulmonary congestion. Holter monitoring was performed after improvement of pulmonary congestion. The frequency components of HRV were calculated in the frequency domain (VLF, low frequency (LF), high frequency (HF), total power (TP) and the ratio of LF to HF power). The left ventricular ejection fraction was calculated, and plasma brain natriuretic peptide (BNP) and norepinephrine were also measured at discharge. Within a mean follow-up period of 19.8 +/- 11.7 months, 18 patients experienced cardiovascular events; 7 patients died and 11 patients required rehospitalization because of worsening of CHF. In univariate analysis, diabetes mellitus (DM), BNP and New York Heart Association (NYHA) functional class were significant as risk factors for cardiac events. VLF power, LF power and TP were the strong predictors for cardiac events in HRV. In multivariate analysis, VLF power predicted cardiac events independently of LF power, TP, DM, BNP and NYHA functional class (chi-square=6.24, p=0.01). CONCLUSIONS: VLF power is an independent risk predictor in patients with CHF.
Usefulness of the percentage of plasma lymphocytes as a prognostic marker in patients with congestive heart failure.
This prospective study was designed to evaluate the prognostic value of the percentage of plasma lymphocytes in patients with diastolic dysfunction as well as systolic dysfunction of the left ventricle. The subjects were 70 consecutive patients who were hospitalized in our institution from April 2001 to August 2002. Following the improvement of congestive heart failure, leukocyte differentiation and neurohumoral factors (plasma levels of atrial and brain natriuretic peptide, norepinephrine, epinephrine, and dopamine) were measured. During the follow-up period (17 +/- 9 months), 18 patients experienced a cardiac event. In the univariate analysis, the percentage of plasma lymphocytes in the cardiac event group was significantly less than that in the noncardiac event group (24.7 +/- 8.40 vs 33.3 +/- 7.64%, P = 0.0006), and brain natriuretic peptide was significantly larger in the cardiac event group (402 +/- 168 vs 153 +/- 51 pg/mL, P = 0.04). However, in patients with preserved systolic function, there was a significant difference in the percentage of plasma lymphocytes between the cardiac and noncardiac event groups (21.7 +/- 9.42 vs 34.2 +/- 8.21%, P = 0.037), although no difference was observed in brain natriuretic peptide (133 +/- 43 vs 125 +/- 50 pg/mL, P = 0.87). Multivariate analysis showed the percentage of plasma lymphocytes was an independent predictor of a cardiac event. The percentage of plasma lymphocytes may be useful for predicting the course of patients with congestive heart failure based on diastolic dysfunction as well as systolic dysfunction.