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Biomedical subjects

T Kawara

Publications and source records attributed to T Kawara.

At least 73 records · Page 4Linked to original sources
PubMed1995

Bradycardia-dependent activation delay of the atrial tissue in a patient with sick sinus syndrome.

Bradycardia-dependent block or activation delay of the atrial tissue has not been documented in the literature. A patient with sick sinus syndrome in whom bradycardia-dependent, as well as tachycardia-dependent, activation delay in the atria was elucidated is reported on. The phenomenon of bradycardia-dependent activation delay was reproducibly demonstrated, both during atrial extrastimulation and incremental atrial pacing from the high right atrium, in the setting of an abnormally prolonged activation interval from the distal stimulating electrodes to the proximal recording electrodes of a quadripolar catheter, which was localized in the high right atrial region. Supernormal conduction seemed to be an unlikely explanation for the observed phenomenon.

Aged↗
PubMed1994

Tricuspid valve replacement with the St. Jude Medical valve.

A study was conducted on 20 patients who underwent tricuspid valve replacement (TVR) with the St. Jude Medical (SJM) valve. Isolated TVR was performed on 9 patients, and additional mitral, or mitral and aortic valve replacements were performed on 11 patients. Four patients (20%) died in the early postoperative period, but there were no deaths related to the SJM valve in the tricuspid position. The mean follow-up period of the 16 survivors was 74.4 months, and there have been no deaths during the follow-up period. The postoperative actuarial survival rate was 80%, 10 years after surgery. Three patients, representing 0.25%/patient-months, developed valve thrombosis, the valve thrombosis-free rate being 72.8%, 10 years after surgery, while entrapment of a leaflet by endothelial pannus was found in one patient, representing 0.08%/patient-months. Thus, the incidence of all prosthetic valve-related complications was 0.34%/patient-months, and the postoperative complication-free rate was 65.3%, 10 years after surgery. The medium-term follow-up study of TVR with the SJM valve revealed no prosthetic valve-related deaths and a relatively low incidence of prosthetic valve-related complications. However, as with other mechanical valves, valve thrombosis was a major risk posed by the SJM valve in the tricuspid position.

Actuarial Analysis↗
PubMed1994

Methicillin-resistant Staphylococcus aureus endocarditis following patch closure of a ventricular septal defect: report of a case.

We report herein the case of a 5-month-old infant who, after developing methicillin-resistant Staphylococcus aureus (MRSA) endocarditis following patch closure of a ventricular septal defect (VSD), was successfully treated by replacement of the Dacron patch with an autogenous pericardial patch. Initially, a large perimembranous VSD was repaired with a Dacron patch and after an uneventful recovery of 1 week, he began to spike intermittent fevers from 38 degrees C to 39 degrees C. Two blood cultures grew MRSA and a two-dimensional echocardiogram performed 16 days after surgery showed an irregular mass attached to the right ventricular aspect of the Dacron patch. At reoperation, a large vegetation attached to the Dacron patch was confirmed, but there was no patch dehiscence. Following removal of the patch, the VSD was repaired with an autogenous pericardial patch, soon after which the fever rapidly subsided. Imipenem, 125 mg every 6 h, and fosfomycin, 300 mg every 6 h, were administered for a total of 24 days after reoperation. The child remains well 12 months after his second operation.

Endocarditis, Bacterial↗
PubMed1994

False aneurysm of the ascending aorta with fistula to the right atrium. Noninvasive diagnosis by computed tomographic scan and two-dimensional echocardiography with successful repair.

A 57-year-old Japanese man presented with symptoms of congestive heart failure 9 years after aortic valve replacement. On auscultation, a continuous murmur was heard at the left lower sternal border. Chest radiograph showed moderate cardiomegaly and a widened upper mediastinum. Computed tomographic scans showed a dilated ascending aorta, in which there was no intimal flap, and also showed a large mass which compressed the right atrium. Two-dimensional Doppler echocardiography revealed abnormal continuous blood flow directed from the dilated ascending aorta to the right atrium and no periprosthetic leak. At operation, a false aneurysm of the ascending aorta which originated from the aortotomy suture line and a fistula from the aorta to the right atrium were confirmed. The fistula was closed with pledgeted sutures, and the ascending aorta was replaced with a collagen-coated double woven velour dacron graft. The patient recovered uneventfully. Computed tomographic scan and two-dimensional echocardiography are complementary techniques for reliable non-invasive assessment of the complexity of an aortic aneurysm.

Aneurysm, False↗
PubMed1994

Double ventricular responses during extrastimulation of atrioventricular nodal reentrant tachycardia.

In patients with dual atrioventricular (AV) nodal pathways, double ventricular responses to a single atrial depolarization have been shown to occur, but virtually only during atrial pacing in sinus rhythm. We report on a patient with a slow-fast form of AV nodal reentrant tachycardia who exhibited double ventricular responses following extrastimulation during AV nodal reentrant tachycardia. The phenomenon of double ventricular responses during the tachycardia was demonstrated by extrastimulation from the proximal coronary sinus. Retrograde unidirectional block in the slow pathway, and an anterograde effective refractory period that was shorter in the fast pathway than that in the slow pathway, are suggested.

Atrioventricular Node↗
PubMed1994

Extended endocardial repair of postinfarction ventricular septal rupture: new operative technique--modification of the Komeda-David operation.

Between January 1992 and November 1992, four consecutive patients (ages 53 to 81 years) underwent early surgical repair of postinfarction ventricular septal ruptures using a new simple operative technique. The principles of the technique are longitudinal incision of the infarcted left anterior ventricular wall, placement of a saccular patch of single equine pericardium that covers the infarcted left ventricular wall, and large buttressed suture closure of the left ventriculotomy. The infarcted septum and infarcted left ventricular wall are completely separated from the left ventricular cavity. In this procedure, the infarcted myocardium is not resected, and left and right ventricular muscles are preserved. This technique is simple and safe for use in the acute phase of myocardial infarction, and it preserves ventricular function after surgery.

Aged↗
PubMed1994

Coronary artery bypass grafting in elderly patients.

To determine the benefits of coronary artery bypass grafting (CABG) in elderly patients, we evaluated 37 patients more than 70 years old who underwent this surgical procedure and compared the results with those in 177 younger patients. Three-vessel lesions and left main lesion were seen in 78.4% and 48.6% of the elderly patients, respectively. Emergency or urgent surgery was performed on 19 patients and the number of distal anastomoses was 3.0 +/- 0.8 per patient. Left main lesion and emergency surgery were more common in elderly patients than in younger patients. Twelve patients received CABG with only a saphenous vein graft (SVG), while the remaining 25 patients had at least one arterial graft. The quality of the saphenous vein was poor to moderate in 50% of the elderly patients, while none of the arterial grafts showed significant sclerotic change. In 17 elderly patients, the ascending aorta showed sclerotic lesions and care was taken when completing proximal anastomoses of SVG to the aortic wall. After surgery, mechanical ventilation was required for an average of 29 h, which was longer than that in the younger patients. Postoperative low cardiac output, hypertension, and arrhythmia occurred in 6, 6 and 15 elderly patients, respectively. There were no early deaths, although there was one hospital death due to posttransfusion hepatitis. Thirty four elderly patients were classified as New York Heart Association functional class I or II during late follow-up maximum of 5 years) and only one had postoperative angina. The ascending aorta showed more sclerotic lesions, and the quality of the saphenous vein was worse, in the elderly patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

The response of atrioventricular junctional tissue to temperature.

To determine the optimal temperature for catheter heat mapping without damaging cardiac tissue, we studied the electrophysiologic and histologic responses of the atrioventricular (AV) conduction system exposed to a specific range of temperatures. In 18 closed-chest dogs, an electrode catheter with a thermistor, tip was positioned transvenously at the AV junction. Radiofrequency current (RFC) was applied in incremental temperature steps until transient 2nd-degree AV block was induced. Catheter tip temperature (CTT) was measured at each step. RFC was immediately discontinued when AV block occurred. AV conduction was evaluated before and 4 weeks after the procedure. Acute transient 2nd-degree AV block was induced in 45 applications, during which the average CTT was 48.7 +/- 2.7 degrees C. In another 40 applications in which 2nd degree AV block was not induced, the average CTT was significantly lower [46.3 +/- 2.5 degrees C] (p < 0.001). Eleven of 16 dogs showed acute 2nd-degree AV block, but had normal AV conduction at 4 weeks (Group A). In the other 5 dogs, 1st-degree AV block was seen at 4 weeks (Group B). The lowest CTTs in Groups A and B were 45 and 49 degrees C, respectively. Histologic findings in 2 dogs from Group A revealed that 10-15% (by area) of the AV node was fibrotic. These findings suggest that the induction of fully reversible AV block can be achieved by titration of RFC, during the application of RFC to the AV junction. In conclusion, RF energy was used to produce a tip temperature of between 45 degrees C and 49 degrees C, which induced reversible and significant interruption of conduction of in tissue in the AV junction, and presumably also in target sites in clinical RF ablation.

Animals↗
PubMed1993

Obstruction of the St. Jude Medical valve--diagnostic and therapeutic values of cineradiography.

Between 1984, and 1992, we observed 8 patients with an obstructed St. Jude Medical (SJM) valve. Of these, 1 had an obstructed SJM valve in the aortic position, 3 in the mitral position, and 4 in the tricuspid position. Diagnosis of obstruction of the SJM valve was made by cineradiography combined with echocardiography in all 8 patients. Restriction or absence of movement of the leaflet of the SJM valve was observed by cineradiography in all of the 8 patients. Normal range of leaflet mobility of the SJM valve was measured by conventional cineradiography in 70 patients with a normal SJM valve, and the results were compared with the leaflet mobility obtained from the 8 patients with an obstructed SJM valve. In this study, leaflet function in the obstructed SJM valve was strikingly abnormal, with both opening and closing angles, and leaflet motion clearly outside the normal range. Of the 8 patients, 4 underwent urgent prosthetic valve replacements after cineradiography and echocardiography were carried out. Thrombolysis using urokinase was performed in 4 patients, and this treatment was successful in 1 patient. Efficacy of thrombolytic therapy was evaluated by repeat cineradiography. Three of the 4 patients who received thrombolysis showed no significant improvement of leaflet mobility after at least 72 hours of thrombolytic therapy, and finally required surgical correction for the obstructed SJM valve. We believe that cineradiography combined with echocardiography is the optimal method for the diagnosis of obstruction of the SJM valve, and to follow the effect of thrombolytic therapy on prosthetic valve function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Nonuniformity of AH intervals during stimulation at different left atrial sites.

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at different left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CS) affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atrial sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on: stimulus-atrium (SA), AH, and stimulus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900-350 msec, mean 532 +/- 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 +/- 10 msec, 57 +/- 10 msec, 44 +/- 11 msec, and 32 +/- 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for HRA vs proximal CS). The mean AH intervals were 123 +/- 23 msec, 104 +/- 28 msec, 95 +/- 15 msec, and 90 +/- 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CS). In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > or = 15 msec; in 9 patients this difference was only < or = 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.

Adolescent↗
PubMed1993

"Paradoxical" AH shortening caused by proximal coronary sinus stimulation during orthodromic reciprocating tachycardia.

INTRODUCTION: During extrastimulation or entrainment of orthodromic atrioventricular (AV) reciprocating tachycardia (ORT), the atrium-His (AH) interval as measured at the His-bundle recording site is expected to lengthen due to extrastimulation-dependent or pacing rate-dependent slowing of AV nodal conduction by impulses that penetrate the tachycardia circuit. We report 6 patients in whom the AH interval "paradoxically" shortened during ORT in response to extrastimulation and rapid pacing from the proximal coronary sinus. METHODS AND RESULTS: Accessory pathway location was right anterior (1 patient), right anteroseptal (1 patient), and left anterior (4 patients). Cycle length of ORT was stable (variation < or = 5 msec) and ranged from 325 to 410 msec. During ORT, extrastimulation and rapid pacing were performed from the proximal coronary sinus and the right atrium. Extrastimulation from the proximal coronary sinus late in diastole caused significant shortening of AH interval in all patients by a mean of 18 +/- 3 msec (range 15 to 20 msec). AH shortening was demonstrated without a change of either the timing or morphologic appearance of the low septal right atrium at the His-bundle recording site. This phenomenon was not observed during right atrial extrastimulation. Rapid pacing from the proximal coronary sinus at cycle lengths of 305 to 390 msec (i.e., 15 to 20 msec shorter than the cycle length of each ORT) again demonstrated shortening of AH interval in all patients by a mean of 15 +/- 3 msec (range 10 to 20 msec). By contrast, rapid pacing from the right atrium demonstrated classical AH prolongation at any paced cycle length. CONCLUSION: AH shortening without a change of either the timing or morphologic appearance of the low septal right atrium at the His-bundle recording site confirms the existence of a distinct posterior atrial input to the AV node. In this setting low septal right atrial activation is not requisite for AV nodal conduction. Whether activation of the low septal right atrium is essential for, or contributes to, AV nodal conduction of atrial impulses from locations other than the proximal coronary sinus needs to be determined.

Adolescent↗
PubMed1993

Doppler echocardiographic evaluation of St. Jude Medical valves in the tricuspid position.

Sixteen of 20 patients who underwent tricuspid valve replacement with a St. Jude Medical valve at our hospital were followed for three to 164 months. Doppler echocardiographic and cineradiographic examinations of the replacement device were performed in 13 patients. There were six males and seven females in the study, with a mean age of 41.9 years. A St. Jude Medical prosthesis had also been implanted in the mitral or mitral and aortic positions of eight of these thirteen patients. Ten patients had normally functioning valves in the tricuspid position and three were diagnosed as malfunctioning. The peak velocity in those patients with normally functioning tricuspid valves was 1.3 +/- 0.2 m/sec. The calculated peak and mean pressure gradients were 6.7 +/- 1.9 mmHg and 2.6 +/- 1.1 mmHg, respectively, and the mean pressure half-time was 120 +/- 22 msec. All normally functioning valves in the tricuspid position had peak velocities of less than 1.55 m/sec, and peak and mean pressure gradients of less than 9.6 mmHg and 5 mmHg, respectively, with the pressure half-time being less than 140 msec in all cases, except for one of the three Doppler studies performed in one patient. However, three Doppler studies performed in two patients with a malfunctioning tricuspid valve revealed peak velocities, peak and mean pressure gradients and pressure half-times which were above these values. After replacement of the malfunctioning valve, or thrombolysis, all of the Doppler-derived values returned to the range found in normally functioning valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Left atrial free-floating ball thrombus in a patient without mitral valve disease].

A free-floating ball thrombus in the left atrium is a rare clinical problem with potentially catastrophic consequences. Thus, early diagnosis and prompt surgical intervention are mandatory. This report dealt with a free-floating ball thrombus in the left atrium in a case without mitral valve disease. A 82-year-old woman was presented with dyspnea, hypotension, and fever. On admission she had cardiac arrhythmia, but had no cardiac murmur. The electrocardiogram revealed atrial fibrillation. Chest X-ray examination showed marked cardiomegaly (cardio-thoracic rate; 94%) without evidence of pulmonary venous congestion. Coagulation studies revealed decreased coagulability. Transthoracic and transesophageal echocardiograms showed retention of pericardial effusion, and a free-floating ball thrombus in the dilated left atrium. Thickening, calcification, and restricted motion of the mitral leaflets were not observed by echocardiography. Removal of the free-floating ball thrombus in the left atrium was successfully performed on the emergency basis. The intact mitral valve was also confirmed at operation. The patient recovered uneventfully. Usefulness of echocardiography, particularly transesophageal echocardiography, for precise diagnosis and intraoperative management of a free-floating ball thrombus in the left atrium is discussed.

Aged↗
PubMed1992

New approach for detection of amplification in cancer DNA using restriction landmark genomic scanning.

We developed a new approach for detecting the gene amplification of cancer DNAs with restriction landmark genomic scanning (RLGS). In cancer research, much effort has been made to find the amplified loci of cancer DNAs, because many lines of evidence indicate association between oncogene amplification and carcinogenesis. Conventionally, such gene amplification has been detected by using Southern hybridization with DNA probes. However, only the information of one locus can be obtained by one hybridization procedure, and analysis of many loci throughout the genome is too laborious and time consuming, even if only several candidate genes are investigated. On the other hand, the "in-gel renaturation method" was reported as another alternative for detection of amplified regions. However, even though this method is much improved, it is difficult to detect less than 7-fold amplification, which is often higher than the amplification of many cancer cases. To overcome these limitations and, in addition, to locate the amplified DNA two dimensionally, we applied RLGS for analysis of DNA amplification in cancer tissues, such as breast cancer (infiltrative tubuloadenocarcinoma), neuroblastoma, meningioma (endotheliomatous meningioma), and thyroid cancer (papillary adenocarcinoma). In some cases of breast cancer, several amplified spots located on the same amplicon were detected. In thyroid cancer, in which no amplification has yet been reported, low-grade amplification was also detected. In this report, we demonstrated that RLGS allows us to screen 2000-3000 restriction landmarks distributed on the genome simultaneously, and even low-grade amplification could be detected effectively. Thus, RLGS has proven to be a very useful method in detecting DNA amplification.

Breast Neoplasms↗
PubMed1992

Complete correction of the tetralogy of Fallot in adults using separated extracorporeal circulation to block intrathoracic collateral circulation and improve perfusion of the renal vasculature.

During the last 10 years, complete correction of the tetralogy of Fallot (TOF) has been performed on 28 adult patients using the "separated extracorporeal circulation" (separated ECC) technique developed by us. In addition to the usual ascending aortic and dual right arterial cannulations for ECC, the separated ECC also involved femoral arterial cannulation and the insertion of a catheter with two balloons via the other femoral artery. Flow via the ascending aorta and femoral artery were maintained separately during ECC. The urine output during separated ECC was significantly better than that during ordinary ECC (P < 0.01) and the operative field for intracardiac correction was clearer as a result of blocking the collateral circulation. Thus we believe separated ECC to be a superior method for total correction of TOF in adults, which may enhance the operative outcome.

Adult↗
PubMed1992

Long-term follow-up results after reconstruction of the mitral valve by leaflet advancement.

In this study, we discuss the clinical results of mitral leaflet advancement performed on 29 patients over the past 10 years and attempt to determine the indication. Preoperative diagnosis of mitral valve lesion consisted of mitral regurgitation in 21 patients and mitral stenosis in 8 patients. Mitral valve repair was applied to the anterior mitral leaflet in 2, the posterior mitral leaflet in 25, and bilateral leaflets in 2 patients. Reoperation was performed on 13 patients, and 1 patient died of renal failure immediately after reoperation. No reoperation was needed for 96.6% of the patients at 1 year, 89.5% at 5 years, 75.0% at 8 years, 63.8% at 10 years, and 52.6% at 15 years postoperatively. At reoperation, the repaired mitral leaflet was found to be calcified in 3 patients more than 9 years after the initial operation. Of the 12 survivors without reoperation, mitral stenosis associated with regurgitation was obvious in 6 patients. Of the 21 patients with preoperative mitral regurgitation, 90.0% showed no deterioration at 5 years, 79.7% at 8 years, and 69.1% at 10 years. On the other hand, for the 8 patients with mitral stenosis, the rates were 87.5% at 1 year, 62.5% at 5 years, 50.0% at 8 years, and 25% at 10 years. Our results suggest that mitral leaflet advancement shows satisfactory results in patients with mitral regurgitation but is not successful for patients with mitral stenosis in the long term because the repaired valve tends to be stenotic in the late postoperative period.

Adolescent↗