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Biomedical subjects

T Kawara

Publications and source records attributed to T Kawara.

At least 55 records · Page 3Linked to original sources
PubMed1998

Coronary sinus pacing initiates counterclockwise atrial flutter while pacing from the low lateral right atrium initiates clockwise atrial flutter. Analysis of episodes of direct initiation of atrial flutter.

INTRODUCTION: Rapid atrial pacing in sinus rhythm may directly induce atrial flutter without provoking intervening atrial fibrillation, or initiate atrial flutter indirectly, by a conversion from an episode of transient atrial fibrillation provoked by rapid atrial pacing. The present study was performed to examine whether or not the direct induction of clockwise or counterclockwise atrial flutter was pacing-site (right or left atrium) dependent. METHODS AND RESULTS: We analyzed the mode of direct induction of atrial flutter by rapid atrial pacing. In 46 patients with a history of atrial flutter, rapid atrial pacing with 3 to 20 stimuli (cycle length = 500 - 170 ms) was performed in sinus rhythm to induce atrial flutter from 3 atrial sites, including the high right atrium, the low lateral right atrium, and the proximal coronary sinus, while recording multiple intracardiac electrograms of the atria. Direct induction of atrial flutter by rapid atrial pacing was a rare phenomenon and was documented only 22 times in 15 patients: 3, 11, and 8 times during stimulation, respectively, from the high right atrium, low lateral right atrium, and the proximal coronary sinus. Counterclockwise atrial flutter (12 times) was more frequently induced with stimulation from the proximal coronary sinus than from the low lateral right atrium (8 vs 1, P = .0001); clockwise atrial flutter (10 times) was induced exclusively from the low lateral right atrium (P = .0001 for low lateral right atrium vs proximal coronary sinus, P = .011 for low lateral right atrium vs high right atrium). CONCLUSIONS: Direct induction of either counterclockwise or clockwise atrial flutter was definitively pacing-site dependent; low lateral right atrial pacing induced clockwise, while proximal coronary sinus pacing induced counterclockwise atrial flutter. Anatomic correlation between the flutter circuit and the atrial pacing site may play an important role in the inducibility of counterclockwise or clockwise atrial flutter.

Adult↗
PubMed1998

Atypical form of the fourth criterion for transient entrainment.

The typical fourth criterion for transient entrainment is defined when both a sudden shortening in conduction interval to and a distinct change in electrogram morphology at a bipolar recording site are demonstrated while performing overdrive pacing of a reentrant tachycardia from a single pacing site at two different constant rates. The purpose of this article was to test the hypothesis that if an intracardiac recording site showing both orthodromic and antidromic capture with entrainment pacing is located suitably distant from the circuit, sudden shortening in conduction interval to that site may occur without any significant change in the bipolar electrogram morphology (i.e., atypical form of the fourth criterion). Atrial overdrive pacing of orthodromic tachycardia was performed in 20 patients with either left anterior (12 patients) or left posterior (8 patients) accessory pathways. We investigated the effects of overdrive pacing from the proximal or distal coronary sinus, specifically effects on the electrogram interval and the electrogram morphology at the right atrial appendage. Overdrive pacing of orthodromic tachycardia from the proximal coronary sinus was performed in 10 of the 12 patients with left anterior accessory pathways; those 10 patients demonstrated the first entrainment criterion at the right atrial appendage site. Overdrive pacing of orthodromic tachycardia at still shorter cycle lengths demonstrated a sudden shortening in conduction interval to the right atrial appendage site. Despite shortening in conduction interval the morphology of the right atrial appendage electrogram was completely or almost identical to that during orthodromic tachycardia, indicating an atypical form of the fourth criterion. This criterion was not demonstrated in patients with left posterior accessory pathways. Thus, atypical fourth entrainment criterion was demonstrated during overdrive pacing of orthodromic tachycardia from the proximal coronary sinus only in patients with left anterior accessory pathways. Demonstration of atypical fourth criterion seems largely dependent on the location of the accessory pathway, the pacing, and the recording sites.

Adolescent↗
PubMed1998

Shortening of the intraventricular conduction time in premature ventricular beats during ventricular extrastimulation: possible role of dimensional shortening of the conducting distance during ventricular systole.

INTRODUCTION: Conduction time (CT) is given by the formula: conducting distance divided by conduction velocity. Based on this formula, we hypothesized that CT shortening (i.e., supernormal conduction) may result from dimensional shortening of the distance of impulse propagation, which naturally occurs during ventricular systole. METHODS AND RESULTS: To test the above, two separate groups of patients were studied, group A (14 patients) for electrophysiologic study and group B (12 patients) for echocardiographic study. In group A patients, CT from the stimulus artifact to the basal lateral wall of the left ventricle (LV) (S-LV interval) was measured using right ventricular (RV) apical extrastimulus testing. S-LV interval shortening in premature RV beats was demonstrated in all 14 patients. The maximum shortening was 20 +/- 9 msec (range 10 to 40), and the maximum % shortening was 16% +/- 6% (7% to 27%). In group B patients with implanted pacemakers, the major (long) and minor (short) axis dimensions of the LV were measured with echocardiography. The major axis dimension was used as an approximate measure of the linear length from the RV apex to the basal lateral wall of LV. The maximum % shortening of the major axis dimensions was 15% +/- 4%, 16% +/- 2%, and 11% +/- 4% during VVI pacing, respectively, at paced cycle lengths of 1,000 (11 patients), 800 (5 patients), and 600 msec (12 patients). The maximum % shortening of the S-LV intervals was comparable in magnitude with that of the major axis dimensions: 20% versus 15% +/- 4%, 15% +/- 7% versus 16% +/- 2% and 16% +/- 6% versus 11% +/- 4%, respectively, at paced cycle lengths of 1,000, 800, and 600 msec. There was also a good temporal correlation between the electrophysiologic (CT shortening) versus echocardiographic (dimensional shortening) parameters. Thus, the intraventricular CT and the major axis dimension of the LV were shortened in a similar magnitude and also at a similar timing in the cardiac cycle. CONCLUSION: These findings suggest the possibility that supernormal conduction may result, at least in part, from dimensional shortening of the pathway length of impulse propagation from the stimulating to recording electrodes, which naturally occurs during ventricular systole.

Adult↗
PubMed1998

Aortic valve replacement with a small mechanical valve prosthesis--a clinical and echocardiographic study of a St Jude Medical valve prosthesis.

The use of small aortic valve prostheses raises concerns about harmful effects of residual obstruction to left ventricular outflow. The present study was undertaken to examine long-term clinical and echocardiographic results in 193 patients who underwent isolated aortic valve replacement (AVR) with a St Jude Medical (SJM) valve of 25 mm or smaller. The study subjects comprised 128 male and 65 female patients with a mean age of 54.1 years. The patients were divided into 2 groups according to the size of the valve prosthesis used for AVR. Small valves (19 or 21 mm) were implanted in 49 patients (group S) and large valves (23 or 25 mm) were used in 144 patients (group L). The group S patients were mainly female, older, and had smaller body surface areas. There were no significant differences in early and late mortality in group S as compared with group L. Furthermore, there was no difference in the incidence of valve-related or cardiac, non-valve-related death, including the incidence of sudden death, between the 2 groups, and they enjoy a similar level of daily routine activity regardless of the valve size used. Left ventricular (LV) function (ejection fraction, fractional shortening, LV mass index, LV end-systolic volume index, and LV end-diastolic volume index) measured by echocardiography improved significantly and returned to normal values after AVR in both groups. Moreover, no significant differences were observed in the postoperative variables of the LV function. These results suggest that 19-mm and 21-mm SJM valves can be safely used for AVR in the majority of Japanese patients.

Aged↗
PubMed1998

Aortic root replacement for Takayasu arteritis associated with ulcerative colitis and ankylosing spondylitis--report of a case.

A 26-year-old man was admitted for treatment of congestive heart failure resulting from aortic regurgitation. The patient had been on medical treatment for ulcerative colitis (UC) since he was 14 years old and for ankylosing spondylitis (AS) since he was 20 years old. On admission, gradients of blood pressure among the extremities were observed. Echocardiography revealed marked dilation of the left ventricle (LV), hypokinetic wall motion of the LV, slightly prolapsed aortic cusps with annular dilatation, and severe aortic regurgitation. Computed tomographic scans demonstrated an aneurysmal dilation of the ascending aorta and thickening of the descending and abdominal aortic wall. Digital subtraction angiography demonstrated an aneurysmal dilation of the ascending aorta; however, there was no clear evidence of steno-occlusive lesions in the brachiocephalic vessels. Blood studies showed positive inflammatory signs and negative rheumatoid factor. HLA typing showed A2, 24(9), B27, 67, Cw1, 7, and DR1, 2. Based on these data, the diagnosis of Takayasu arteritis associated with UC and AS was made. Aortic root replacement was performed. Steroid therapy was restarted immediately after surgery. Histologic studies of the aortic wall showed findings compatible with Takayasu arteritis. The combination of these rare diseases suggests that they have a common pathophysiologic background.

Adult↗
PubMed1998

Ventricular septal defect of the atrioventricular canal type--report of a surgically treated case.

A 19-month-old male infant with Down syndrome was referred for investigation of heart murmur. An electrocardiogram showed normal axis (+100 degrees) of the QRS complex, incomplete right bundle branch block, and biventricular hypertrophy. Echocardiography revealed a ventricular septal defect (VSD) and a cleft of the anterior mitral leaflet with mild value regurgitation. The anterior mitral leaflet and the septal tricuspid leaflet attached to the same level of the ventricular septum were also delineated, however, no atrial septal defects were detected. Cardiac catheterization demonstrated pulmonary hypertension and a left to right shunt at the right ventricle. During operation, no defects in the atrial septum and no cleft of the septal tricuspid leaflet were found. Cleft of the anterior mitral leaflet, continuity between the mitral anterior leaflet and the tricuspid septal leaflet, and a VSD of the atrioventricular canal type were confirmed. The cleft of the anterior mitral leaflet and the VSD were repaired with the aid of cardiopulmonary bypass. The patient recovered uneventfully.

Electrocardiography↗
PubMed1998

Valve surgery in elderly patients 70 years or older: early and late results.

Between April 1986 and March 1997, 75 patients (Group E) who were 70 years or older underwent valvular operations, and another 73 patients who were under 70 years constituted a comparison group (Group Y). Valve replacement was performed on 131 patients (Group E; 65 patients, Group Y; 66 patients), reparative procedures on 11 patients (Group E; 7, Group Y; 4), and aortic root replacement on 5 (Group E; 3, Group Y; 2). Coronary artery bypass grafting was concomitantly performed on 13 patients (Group E; 7, Group Y; 6). In the elderly patients, preoperative clinical status, including cardiac and non cardiac organ functions, was not necessarily more severe than that in the younger patients, however, perioperative restoration of cardiac and pulmonary functions required a longer time in Group E than Group Y. There were no significant differences in operative mortality rate, long-term survival rate, the probability of freedom from all events related to native and prosthetic valves, and in activity of daily life between Group E and Group Y. These results suggest that valvular operation for elderly patients 70 years or older may be safely performed with operative risks similar to those of younger patients by application of modern surgical techniques.

Aged↗
PubMed1998

Prosthetic valve thrombosis after abdominal surgical procedures: a case report.

A 63-year-old woman with a prosthetic mitral valve who developed valve thrombosis after abdominal surgical procedures is reported. She had undergone mitral valve replacement with a Sorin-Bicarbon valve 3 years previously, and was referred for an operation due to rectal cancer with anal bleeding. On admission, the patient was on oral anticoagulant therapy with warfarin, and the intensity of anticoagulation was around 40% of Thrombotest. Doppler echocardiography showed that the prosthetic mitral valve function was normal. Low anterior resection of the rectum was uneventful. Management of the perioperative anticoagulation was peformed with heparin, however, the postoperative anticoagulation using intravenous infusion of heparin was imperfectly achieved. Consequently, thrombosis of the prosthetic mitral valve occurred 8 days after the operation. Replacement of the thrombosed prosthetic valve was performed with successful results. The imperfect postoperative anticoagulation with heparin may have been the cause of the valve thrombosis. The management of perioperative anticoagulation during noncardiac operations is discussed.

Abdomen↗
PubMed1997

Cineradiographic evaluation of ATS open pivot bileaflet valves.

BACKGROUND AND AIMS OF THE STUDY: Echocardiography and cineradiography are both valuable for the evaluation of prosthetic valve function, especially of mechanical valves. Although Doppler echocardiography data are available for the recently developed ATS valve, cineradiographic evaluation of leaflet movement of the valve has not been performed. MATERIALS AND METHODS: Five patients received aortic and another five mitral valve replacement with the open pivot ATS bileaflet prosthetic valve. There were three men and seven women; mean patient age was 58.8 years. Cineradiographic and Doppler echocardiographic evaluations of the ATS valve were performed early after surgery in all 10 patients. RESULTS: There were no early deaths after surgery or after discharge from the hospital. No valve-related complications were seen, and no clinical symptoms or signs of prosthetic malfunction were observed during the follow up period. Doppler-derived values of the ATS valve were comparable with those previously reported; however, cineradiography of the valve demonstrated that the mean angle enclosed by the two open leaflets was 37.6 degrees (range: 34 degrees to 44 degrees) in the aortic position and 29.7 degrees (range: 20 degrees to 35 degrees) in the mitral position. Mean leaflet mobility was 93.0 degrees (range: 86 degrees to 96 degrees) in the aortic position and 100.0 degrees (range: 92 degrees to 110 degrees) in the mitral position. Thus, the opening of the normally functioning ATS valves in vivo was less than that observed in vitro and reported by the manufacturer. CONCLUSIONS: These results suggest that unevenly distributed blood flows with different velocities through the two side orifices and the central orifice may result in incomplete opening of the ATS leaflets, which respond with great sensitivity to localized blood flow. Our findings appear to be important to avoid the removal of a normally functioning ATS valve only because the leaflet opening appears to be 'restricted'.

Adult↗
PubMed1997

[Aortic arch surgery in the elderly].

A consecutive series of 16 patients over 75 years old who underwent aortic arch operations with hypothermic selective cerebral perfusion from 1994 to 1997 was analyzed. These patients (group O) was compared with 18 patients aged from 70 to 74-year-old (group M) and 38 patients under the age of 69 (group Y) who underwent aortic arch operation during the same period. There were 5 males and 11 females with a mean age of 77.8 years (range 75 to 86) in group O. Twelve patients were in aortic dissection and 4 patients were in atherosclerotic aneurysms. There were 5 hospital deaths (31.2%) in group O, 2 (11.1%) in group M and 2 (5.3%) in group Y. There was significant difference in hospital mortality rate between group O and group Y. Cerebral complication occurred in 2 patients (12.5%) and postoperative respiratory failure occurred in 7 (47%) in group O. Aortic arch operations for the elderly patients can be performed with increased but operative mortality in the elderly patients remains high. In this study, we discussed that influence of risk factors on the operative result and operative indication in the elderly patients.

Age Factors↗
PubMed1997

[Heart valvular disease in patients 70 years old and older].

From June 1986 to December 1996, 69 patients older than 70 years old underwent AVR (29 cases), MVR (21 cases), MVP (5 cases), DVR (10 cases), aortic root replacement (3 cases), repair of PVL (1 case) in our hospital. There are five (7.2%) operative and hospital deaths. The survival rate was 88.4% at 10 year after surgery and three (4.7%) late deaths. The factors associated with early deaths were renal dysfunction and DVR. Our surgical results suggest that open heart surgery can be performed safely even elderly patients, in spite of their precarious physiologic homeostasis. Not the chronological age but the physiological age is important determinant for surgical indication. If quality of life (QOL) can be expected to be enhanced, we recommend an aggressive surgical approach.

Age Factors↗
PubMed1996

Effects on visual functions during tasks of object handling in virtual environment with a head mounted display.

This study examined the effects on visual functions of a prolonged handling task within the helmet-mounted display environment. Both version eye movement and accommodative response became gradually slower during the 40-min task. Although delayed presentation of display after head movement noticeably worsened both visual responses, presentation delay after hand movement did not significantly change the sluggishness of responses. Therefore it is suggested that decreasing time delay after head movement is a more important factor in order to improve human performance of handling tasks within the HMD environment.

Accommodation, Ocular↗
PubMed1996

Earlier activation of the distal than the proximal site of the coronary sinus may represent retrograde conduction through AV node: significance of recording of far distal coronary sinus.

During retrograde conduction through an accessory pathway (AP) or the atrioventricular (AV) node, earlier activation of the distal recording site than a more proximal site of the coronary sinus (CS) generally indicates retrograde conduction via a distally located AP. Thus, after successful ablation of a left-sided AP, if the distal CS recording site is activated earlier than a more proximal site retrogradely, it is considered to suggest-in the absence of His-bundle recording or more frequently in the setting of poor recording of the low septal right atrial electrogram-a conduction via a second AP (located more distally), and not conduction via the AV node. Yet, we hypothesized that retrograde conduction through the AV node may activate the far distal site of the CS (CSD) earlier than a more proximal site, as the anterior atrial wavefront, coming retrogradely from the AV node and traveling along the anterior mitral annulus, could reach the CSD earlier than a more proximal site. To test this we studied 18 patients with intact retrograde conduction via the AV node, but without evidence of an AP. The CSD was recorded by means of a quadripolar catheter (interelectrode distance of 2-5 mm); retrograde activation sequence at the distal (CSD1-2) versus proximal (CSD3-4) bipolar recording site was determined during ventricular stimulation. In 12 of 18 patients the CSD1-2 recording site was activated 5-10 ms earlier than the CSD3-4 recording site, in 3 of 18 patients the CSD1-2 site was activated 5 ms later than the CSD3-4 site; in the remaining 3 patients both recording sites were depolarized simultaneously. The results indicate that the CSD was often depolarized earlier than a more proximal site by impulses that conducted to the atria retrogradely via the AV node while the quadripolar recording catheter was placed at the CSD. This observation, although not well documented previously, suggests that the sequence of retrograde atrial activation in the CS should be studied carefully in consideration of the actual location of the mapping catheter in order to correctly diagnose the presence or absence of conduction via an AP.

Adolescent↗
PubMed1995

Long-term results of mitral valve repair for non-rheumatic mitral regurgitation.

The durability of mitral valve repaired with reconstructive techniques is variable. If the durability continues to be good, mitral valve repair may be the procedure of choice in many patients with mitral regurgitation. Between December 1970 and June 1993, 54 patients had mitral valve repair for non-rheumatic mitral regurgitation. There were 38 men and 16 women with a mean age of 46.8 (range 19-68) years. The pathology which required surgical treatment was torn chordae in 38 patients, elongation of the chordae in five, valve prolapse without elongation or rupture of the chordae in six, infective endocarditis in three, and annular dilatation in two. Forty-four patients had triangular or quadrangular resection of the mitral leaflet, and seven had annuloplasty alone. Choral reconstruction was performed on three patients. There were no operative deaths. Five patients (9%) died late after operation. The actuarial survival rate and the valve-related death-free rate at 10 years were 83.9% and 90.0%, respectively. Seven patients (13%) required reoperation. Freedom from reoperation at 10 years was 84.5%. Improper evaluation of residual regurgitation during operation and suture dehiscence were the principal causes of reoperation. It was concluded that mitral valve repair for non-rheumatic mitral regurgitation showed low operative mortality and stable long-term results. It is suggested that intraoperative transoesophageal colour Doppler echocardiography provides accurate assessment of mitral valve competence and may be helpful in reducing the need for reoperation.

Adult↗