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Biomedical subjects

Yukio Ozawa

Publications and source records attributed to Yukio Ozawa.

18 recordsLinked to original sources
PubMed2003

Effect of 60 minutes of rapid atrial pacing on atrial action potential duration in the in-situ canine heart.

Right atrial monophasic action potentials were recorded before and after 60 minutes of rapid atrial pacing (pacing cycle length (CL); 127 +/- 10 ms) in 12 closed-chest dogs. The right atrial (RA) monophasic action potential (MAP) duration at 90% repolarization (RAMAPD) was measured at CLs of 400 ms and 250 ms. CL-dependent changes in RAMAPD (CL 400 ms - 250 ms) before and after rapid atrial pacing were 24 +/- 1 ms and 16 +/- 5 ms, respectively (p < 0.02). RAMAP was recorded at each atrial pacing CL starting at 240 ms decreasing by 10-ms increments. RAMAPD alternans was observed in 10 of 12 dogs at a CL of 163 +/- 17 ms before and in 10 of 12 dogs at s CL of 198 +/- 29 ms (p < 0.01) after rapid atrial pacing. Sustained atrial fibrillation (AF) (>5 minutes) was induced in 1 of 12 dogs at a pacing CL of 130 ms before rapid atrial pacing and in 4 of 12 dogs at a pacing CL of 135 +/- 17 ms after rapid atrial pacing. Onset of AF was always preceded by the RAMAPD alternans. Sixty minutes of rapid atrial pacing leads to diminution of rate adaptation of atrial action potential duration (APD) and appearance of APD alternans of greater magnitude at longer CL, both of which may contribute to the initiation and perpetuation of AF during its early phase.

Action Potentials↗
PubMed2003

Intravenous administration of class I antiarrhythmic drug induced T wave alternans in an asymptomatic Brugada syndrome patient.

A 53-year-old man with an abnormal ECG was referred to the Nihon University School of Medicine. The 12-lead ECG showed right bundle branch block and saddleback-type ST elevation in leads V1-V3 (Brugada-type ECG). Signal-averaged ECG showed positive late potentials. Double ventricular extrastimuli (S1: 500 ms, S2: 250 ms, S3: 210 ms) induced VF. Amiodarone (200 mg/day) was administered for 6 months and programmed ventricular stimulation was repeated. VF was induced again by double ventricular stimuli (S1: 600 ms, S2: 240 ms, S3: 170 ms). Intravenous administration of class Ic antiarrhythmic drug, pilsicainide (1 mg/kg), augmented ST-T elevation in leads V1-V3, and visible ST-T alternans that was enhanced by atrial pacing was observed in leads V2 and V3. Visible ST-T wave alternans disappeared in 15 minutes. However, microvolt T wave alternans was present during atrial pacing at a rate of 70/min without visible ST-T alternans.

Amiodarone↗
PubMed2003

Haplotype analysis of the human renin gene and essential hypertension.

The human renin gene is an attractive candidate for involvement in the underlying cause of essential hypertension (EH). Despite extensive examination, the relation between the renin gene and hypertension remains unclear. The aims of the present study were to discover new genetic markers of EH and to investigate the relations between polymorphisms of the renin gene and EH in the Japanese. Using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method, we isolated 3 novel variants of the renin gene; a single nucleotide polymorphism (SNP) in intron 4 (T+17int4G), a variable number of tandem repeats (VNTR) polymorphism in intron 7, and a missense mutation in exon 9 (G1051A). We performed an association study with these polymorphisms in 212 patients with EH and 209 age-matched normotensive (NT) subjects. The frequency of genotypes VNTR and T+17int4G did not differ significantly between the 2 groups, whereas the overall distribution of G1051A was significantly different between EH and NT. Haplotype analysis revealed that the overall distribution of haplotypes differed significantly between the EH and NT groups. PRA levels in patients with EH with the G/G genotype were significantly higher than in subjects with EH with G/A and A/A genotypes. These data suggest that the missense mutation in exon 9 may affect the enzymatic function of renin and consequently may be involved in the etiology of hypertension.

Adult↗
PubMed2003

Combined atriofascicular and fasciculoventricular connections.

A 32-year-old man with a 20-year history of palpitation showed a short PQ interval and delta wave on 12-lead ECG. An electrophysiological study showed that the atrio-His (AH) and His-ventricular intervals were not influenced by rapid right atrial pacing or by bolus injection of adenosine triphosphate (ATP). The AH interval was shortened by coronary sinus ostium (CSos) pacing. Ventricular stimulus to the atrial activation interval was not affected by ATP but shortened by para-Hisian pacing and orthodromic His bundle activation was followed by atrial activation. The tricuspid - inferior vena cava isthmus was blocked by CSos pacing, but Ith conduction existed during low lateral right atrial pacing.

Adenosine Triphosphate↗
PubMed2003

A novel variable number of tandem repeat polymorphism of the renin gene and essential hypertension.

The aims of the present study were to find new genetic markers of essential hypertension (EH) and to investigate relationships between EH and polymorphisms of the renin gene. Using single strand conformation polymorphism, we discovered a new variable number of tandem repeat (VNTR) polymorphism in intron 7 that is 18 bp upstream from the boundary with exon 8. Nucleotide sequencing revealed that this VNTR polymorphism is a tandem repeat of the 4-nucleotide sequence TCTG. There were 6 alleles of this VNTR polymorphism, ranging from 7 repeats to 12 repeats. We analyzed the association between EH and this VNTR polymorphism. There was no significant difference in the overall distribution of this VNTR polymorphism between the EH and normotensive subjects. In summary, we discovered a novel VNTR polymorphism in the renin gene, and this polymorphism was not associated with EH.

Adult↗
PubMed2002

Signal-averaged P-wave analysis of normal controls and patients with paroxysmal atrial fibrillation: a study in gender differences, age dependence, and reproducibility.

BACKGROUND: Atrial fibrillation is often first recognized after a complication such as embolic stroke has occurred. Limited data are available for the prospective identification of patients at risk for developing atrial fibrillation. HYPOTHESIS: Demonstration of areas of slow conduction in the atrium by means of P-wave signal averaging may identify individuals at risk for atrial fibrillation. METHODS: P-wave signal averaging from the surface electrocardiogram was performed in 199 normal controls and 81 patients with paroxysmal atrial fibrillation using an automated, P-triggered, high-resolution signal for analysis. RESULTS: Of the variables measured, the filtered P-wave duration and P-wave integral were significantly different between controls and patients (filtered P-wave duration 120 +/- 9 vs. 145 +/- 21 and P-wave integral 666 +/- 208 vs. 868 +/- 352), whereas the terminal root-mean-square (RMS) voltages (RMS 20, RMS 30, RMS 40) showed no significant differences between the two groups. Regression analysis of the first and second measurement of the filtered P-wave duration obtained during consecutive tests showed excellent reproducibility (r and r2 of 0.96 and 0.92). The duration of the filtered P wave showed no age dependence but was shorter in women. CONCLUSION: Utilizing the 90th percentile value of the filtered P-wave duration of 133 ms in men and 130 ms in women, the sensitivity was 80 and 81%, the specificity 92 and 90%, the positive predictive value 84 and 73%, and the negative predictive value 90 and 93%, respectively.

Adult↗
PubMed2002

Cooled-tip ablation results in increased radiofrequency power delivery and lesion size in the canine heart: importance of catheter-tip temperature monitoring for prevention of popping and impedance rise.

UNLABELLED: Since myocardial lesion size during radio-frequency (RF) ablation is limited at high power by impedance rise when electrode tip temperature exceed 100 degrees C, controlling tip temperature by continuous intraelectrode saline infusion could permit generation of larger lesion. (1) Two dogs randomly received either standard or cooled tip RF ablation at 4 to 6 separate LV sites. Power output of 30 W was delivered via modified 7 Fr deflectable catheter with 4 mm tip for up to 120 sec or until impedance rise occurred. (2) Six dogs randomly received cooled tip RF ablation at power output of 20, 30, 40 W for 120 sec. (3) Three dogs randomly received cooled tip RF ablation using room temperature saline (21-25 degrees C) or chilled saline (1-4 degrees C) infusion. RESULTS: Overall, peak tip temperature was lower for cooled vs standard RF deliveries (97 +/- 17 degrees C vs. 42 +/- 8 degrees C). Lesion depth and volume were significantly larger for cooled burns. Lesion depth and volume and the incidence of abrupt impedance rise/popping did not differ between room temperature saline and chilled saline infusion. The catheter-tip temperature at the onset of popping and abrupt impedance rise was 54 +/- 5 degrees C (48-60 degrees C) and 59 +/- 10 degrees C (50-75 degrees C). CONCLUSION: Cooled tip RF current delivery at high power is associated with increased myocardial lesion size which may facilitate successful ablation of ventricular tachycardia associated with acquired structural heart disease. Catheter-tip temperature should be maintained below 45 degrees C to prevent popping and abrupt impedance rise during RF energy delivery.

Animals↗
PubMed2002

Relationship between polarity of the flutter wave in the surface ECG and endocardial atrial activation sequence in patients with typical counterclockwise and clockwise atrial flutter.

BACKGROUND: The relation between ECG and activation patterns within atria in typical atrial flutter (AFL) patients (pts) has not been defined due to the lack of simultaneous multisite right and left atrial mapping. METHODS: In 13 pts with AFL, a Halo catheter was positioned along tricuspid annulus and multipolar catheters were placed in right atrial appendage, His bundle region, coronary sinus (CS), proximal portion of right pulmonary artery (Bachmann's bundle region, BB) and esophagus (Eso) to record right and left atrial activation simultaneously. RESULTS: In counterclockwise (CCW) AFL (11 pts), 9 showed negative flutter wave (F) and 2 positive F in the inferior leads. CCW/negative F; CS electrograms (EGs) were proximal to distal, Eso EGs were inferior to superior and BB activation was later than CS and Eso. positive F; BB activation was earlier than CS. Eso EGs were superior to inferior or simultaneous. In clockwise (CW) AFL (7 pts), 5 showed positive F and 2 negative F. CW/positive F; BB activation preceded Eso and CS. Eso EGs were superior to inferior. CS EGs were proximal to distal (1), middle to proximal, distal (3) or proximal, distal to middle (1). negative F; CS EGs were proximal to distal. CS activation was earlier than BB or CS and BB activation were simultaneous. Eso EGs were inferior to superior. CONCLUSION: Impulse conduction to the left atrial free wall through either lower or upper interatrial connection is a major determinant of ECG morphology in AFL.

Adult↗
PubMed2002

Ectopic atrial rhythm with exit block following catheter ablation for focal atrial tachycardias in a patient with prior surgery for atrial septal defect.

The patient was a 40-year-old woman with a history of surgery for atrial septal defect and catheter ablation for typical atrial flutter. An electrophysiological study was performed because she had palpitation and syncope. She had ectopic atrial rhythm originating from low lateral RA. Two focal atrial tachycardias ([1] superior vena cava-RA junction and [2] a lowposteroseptal RA) were successfully ablated. Following catheter ablation for the second atrial tachycardia, she developed junctional rhythm because ectopic atrial rhythm showed exit block. However, atrial activation of junctional rhythm could conduct into the ectopic atrial rhythm focus and reset the rhythm when atrial activation of junctional rhythm reached the blocked line after atrial refractoriness by preceding ectopic atrial rhythm.

Adult↗
PubMed2002

Angiotensin-converting enzyme gene and longevity in the Xin Jiang Uighur autonomous region of China: an association study.

BACKGROUND: Longevity can be regarded as a multifactorial trait that results from an interaction between environmental factors and sets of epistatic alleles that have pleiotropic age-dependent effects. The Hotan district in the Xin Jiang Uighur Autonomous region of China is relatively isolated and is well known for an ethnic group that displays marked longevity. METHODS: We performed a correlation study between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and longevity by comparing distributions of the polymorphism between three different ethnic groups in this region. We obtained data from 424 subjects comprising 227 Uighur individuals, 108 Kazakh individuals, and 89 Han individuals. All subjects in the latter two groups ranged in age from 65 to 70 years, whereas the Uighur subjects actually comprised two different age groups: those ranging in age from 59 to 70 years (Uighur older group in Hotan [UOH]) and those ranging in age from 90 to 113 years (Uighur longevity group in Hotan [ULH]). Genomic DNA was extracted from peripheral white blood cells. Polymerase chain reaction was performed to amplify the I/D polymorphic region of the ACE gene. RESULTS: Frequencies of the insertion (I) and deletion (D) alleles were 0.596 (243/408) and 0.404 (165/408) in the Uighur group, 0.606 (130/216) and 0.394 (85/216) in the Kazakh group, and 0.657 (117/178) and 0.343 (61/178) in the Han group. The overall distributions of alleles in these three groups did not differ significantly (chi(2) = 4.6, p =.33). Within the Uighur group, frequency of the D allele was significantly higher in the ULH group (0.448) than in the UOH group (0.355) (p <.04). CONCLUSIONS: This association reflects a genetic influence on differential survival and may point to pleiotropic age-dependent effects on longevity. Our data may help elucidate the relationship between natural longevity and race difference among individuals in the Xin Jiang Uighur Autonomous region of China.

Aged↗
PubMed2002

Ambulatory blood pressure monitoring in Uygur centenarians.

Cross-sectional surveillance was carried out in long-lived Uygur in China to investigate blood pressure (BP) and pulse rate (PR) variation in centenarians. The study group comprised 33 centenarians (age > or = 100 years), 103 longevous subjects (age 90-99 years) and 100 elderly (age 65-70 years) subjects. Office BP was measured, and 24-h noninvasive ambulatory blood pressure monitoring (ABPM) was performed. The office BP was higher and hypertension occurred more frequently in the centenarians than in either the longevous or elderly subjects. Mean 24-h systolic and diastolic BP was higher in the centenarians than in the other 2 groups. However, mean 24-h PR did not differ between them. Day-night differences in systolic BP decreased, and the non-dipper-type BP pattern was common in the centenarians (79.1% vs 68% and 63.6% in longevous and elderly subjects, respectively). Circadian BP was characterized by 3 peaks in longevous subjects and multiple peaks in centenarians. Morning rising and nocturnal dipping of BP were observed in both longevous and elderly subjects. In conclusion, BP in longevous and elderly Uygur was characterized by circadian rhythmicity, but the nocturnal fall in BP was not seen in centenarians. Differences in day-night BP and circadian rhythmicity may decrease with advancing age, especially in centenarians.

Aged↗
PubMed2002

Rate-dependent changes in atrial action potential duration after short- duration rapid atrial pacing in humans.

The effect of rapid atrial pacing on the rate adaptation of the atrial action potential duration was studied in humans. The right atrial monophasic action potential (RAMAP) of 5 patients was recorded before and after 30 min of rapid atrial pacing. The pacing cycle length (CL) was 146 +/- 9 ms, the shortest duration at which 1:1 capture was possible. The RAMAP duration at 90% repolarization (RMAPD) was measured. CL-dependent changes in RAMAPD (CL 600 ms-CL 300 ms) before and after rapid atrial pacing were 51.8 +/- 10.7 ms and 30.8 +/- 7.6 ms (p < 0.05), respectively.

Action Potentials↗
PubMed2002

A novel missense mutation of exon 3 in the type A human natriuretic peptide receptor gene: possible association with essential hypertension.

The natriuretic peptide (NP) family is involved in regulation of blood pressure and fluid volume. We recently characterized the exon/intron organization of the human type A NP receptor (hNPRA) gene. The aim of this study was to isolate the genetic markers according to the organization of this gene, and to study the association between this gene and essential hypertension. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we identified a novel missense mutation, M3411, consisting of a methionine (ATG) to isoleucine (ATC) substitution at nucleotide 1023 in exon 3. Computer-aided three-dimensional structural analysis suggested that M341 exists in the loop between two alpha-helices, and that the mutation may influence receptor activities by altering the conformation of the alpha-helices. We performed an association study of the mutation in 210 essential hypertension (EH) patients and 210 normotensive controls. The overall distribution of alleles was not significantly different between the control and EH groups. However, the C/C homozygous genotype was found only in the EH group. The ratio of plasma brain natriuretic peptide (BNP)/mean blood pressure of the C/C genotype was significantly higher than that of the G/G genotype or the G/C genotype. We conclude that the significance of homozygous M3411 mutation in exon 3 is worth investigating for its possible association with EH.

Adult↗
PubMed2002

Structure and polymorphisms of the human natriuretic peptide receptor C gene.

Natriuretic peptides (NPs) regulate cardiovascular homeostasis, including natriuresis, diuresis, vasodilation, regulation of endocrine secretion, and inhibition of cellular growth. Atrial natriuretic peptide receptor C (NPRC) has a short cytoplasmic domain that lacks guanylyl cyclase activity. We used information available for the cDNA of human NPRC to amplify products covering all genomic regions of the gene by long polymerase chain reaction (PCR) and thermal asymmetric interlaced (TAIL)-PCR. PCR products were sequenced directly after extraction and purification. The human NPRC gene spans > 65 kb and contains eight exons and seven introns. All of the exon-intron junction sequences contain the GT/AG consensus junction sequence. We then used the PCR-single-strand conformation polymorphism (PCR-SSCP) to identify polymorphisms of the human NPRC gene. All eight exons and neighboring introns were analyzed by PCR-SSCP for 96 subjects, and migration variants were observed for intron 1, exon 2, and exon 5. Direct sequencing of these variants revealed the following sequence differences: a C to T transition in intron 1, an A to C transition in exon 2, and a C to T transition in exon 5. PCR-restriction fragment length polymorphism analysis (PCR-RFLP) was used to evaluate all three variations. We have determined the structural organization and identified polymorphic sites in the human NPRC gene. The results of this study will facilitate further genetic analyses of the human NPRC gene function.

Base Sequence↗
PubMed2002

Role of signal-averaged electrocardiograms for predicting the inducibility of ventricular fibrillation in the syndrome consisting of right bundle branch block and ST segment elevation in leads V1-V3.

Right bundle branch block and ST segment elevation (RBBB-STE) in the right precordial leads have been reported as a distinct clinical and electrocardiographic syndrome in patients prone to ventricular fibrillation (VF) in the absence of structural heart disease (Brugada syndrome). The purpose of the study was to investigate the role of signal averaged electrocardiogram (SAECG) in identifying patients at high risk among asymptomatic RBBB-STE patients. Thirteen patients with the RBBB-STE ECG were identified. Symptoms were: syncope (n=3, cases 1, 3, and 11), atypical chest pain (n=3, cases 4, 10, and 12) and palpitations (n=2, cases 6, and 7). The other 5 patients were asymptomatic. SAECG and programmed electrical stimulation (PES) were conducted in all patients. Body surface late potentials (LPs) were present in 7 of 13 patients before PES. Vf was induced in 6 of 7 LP positive patients. Vf was induced in 3 of 6 LP negative patients, but LP became positive in 2 of 3 patients in whom Vf was induced. One patient with syncope due to VF (case 1), 1 patient without symptoms who died suddenly during follow up (case 2), and 1 asymptomatic patient (case 9) showed reproducibly positive LP. In a patient (case 9) with positive LP at baseline, LP transiently became negative during follow up. In RBBB-STE patients, reproducibly positive LP is at risk for malignant ventricular arrhythmias and sudden death. Repeated SAECG recording may be useful for screening high-risk patients who should receive electrophysiological study among asymptomatic RBBB-STE patients.

Adult↗