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Biomedical subjects

A Shiikawa

Publications and source records attributed to A Shiikawa.

34 records · Page 2Linked to original sources
PubMed1990

[Laser ablation in the treatment of ventricular tachycardia: problems in the clinical case].

I. Experimental Studies We examined if laser ablation could make the same characteristic lesion as cryolesion to canine myocardium. Nine mongrel dogs were used in this experiment. Right lateral thoracotomy was performed and Nd:YAG laser was delivered onto the epicardial surface of both ventricles. Laser power of between 10 and 50 W was used with the various duration of 3 and 20 s, keeping the lasing distance 5 mm above the cardiac surface. Histologically, the lesion showed a well-demarcated area consisted of coagulation necrosis and contraction band necrosis in the acute phase, which changed to a fibrous scar in the chronic phase. There was a good correlation (r = 0.79; n = 52, p less than 0.01) between the lasing energy and the depth of the denaturation zone. II. A Case Report A 45-year-old male with ventricular tachycardia (VT) after aortic valve replacement was operated upon with Nd; YAG laser delivery. An antero-lateral thoracotomy through 4th and 6th inter-costal space was performed. The intraoperative mapping showed the three origins of VTs to be near the apex of left ventricle. With cardiopulmonary bypass, Nd; YAG laser was delivered onto the endocardial surface adjacent to arrhythmogenic foci. The lasing power was 10-30 W with the duration of 5.0-9.9 s. One hundred twenty seven trials were done with the total lasing energy to be 12490 J. Subsequently cryoablation was added on this area. Though VT remained in acute phase, 2 weeks later, all of tachyarrhythmia was abolished spontaneously.

Animals↗
PubMed1990

[Technical considerations for the epicardial approach in Wolff-Parkinson-White syndrome].

Epicardial approach consists of meticulous dissection of the annular fat pad of the Kent bundle site and subsequent cryocoagulation from the epicardial side. This technique obviates the need of atriotomy and makes ablation without cardiopulmonary bypass possible. In performing this approach for patients with the left parietal or posteroseptal pathway through median sternotomy, special technical strategies are necessary to keep hemodynamic status stable during dissection and cryoablation procedures, because in these cases apex of the heart has to be retracted upward to approach the Kent bundle site. For this purpose, the use of an ultrasonic surgical aspirator for dissection of the annular fat pad is required. With this instrument fat tissue is emulsified and aspirated by stroking the fat pad gently, easy dissection is possible without injury to major coronary vessels, even through a narrow operative field. Another point is to dissect the annulus fat below the coronary sinus (i.e., at the space between the coronary sinus and circumflex coronary artery), not above it. By doing this extensive retraction of the apex is no longer necessary. In performing cryocoagulation care has to be taken not to involve the coronary artery into the lesion. However, too tight retraction of the coronary artery may cause another risk of thrombosis. Sometimes moderate systemic heparinization should be performed during coronary retraction and cryocoagulation procedure.

Heart Conduction System↗
PubMed1990

[A case report of successful surgical removal of a lipoma in the left ventricle].

A 63-year-old man with anterior chest oppression was diagnosed as an acute myocardial infarction. The two-dimensional echocardiogram revealed a mass which bulged into the left ventricular cavity. Subsequently, the computed tomographic findings of the mass lesion demonstrated the attenuation values of -49 Hounsfield units, which corresponded to that of fatty tissues. From these findings the left ventricular lipoma was highly suspected. The tumor existed at the base of the anterior papillary muscle. It was successfully resected and mitral valve replacement was performed concomitantly. The tumor was yellowish and sized by 25 X 20 mm. On histological examination of the specimen, the tumor was composed of mature fatty cells. CT scanning was very useful for the preoperative evaluation of lipoma.

Echocardiography↗
PubMed1989

Cryosurgical ablation of accessory atrioventricular pathways without cardiopulmonary bypass: an epicardial approach for Wolff-Parkinson-White syndrome.

An epicardial approach has been developed and applied to 31 Kent bundles (23 parietal, 1 right anteroseptal, and 7 posteroseptal bundles) in 28 patients with Wolff-Parkinson-White syndrome. Our technique consists of dissection of the atrioventricular fat pad of the Kent bundle site using an ultrasonic aspirator and subsequent cryosurgical ablation. For the left parietal and posteroseptal pathways, the apex of the heart has to be retracted upward, but this maneuver was well tolerated in all patients. Moreover, even through a narrow operative field, the ultrasonic aspirator permitted deliberate dissection on the beating heart without injury to major coronary vessels or the atrial wall. In 89% of the patients, operation was performed without the use of heart-lung bypass. All patients were free from preexcitation. With this technique, all Kent bundles except that adjacent to the atrioventricular node can be ablated on the beating heart, usually without heart-lung bypass.

Adolescent↗
PubMed1989

[Direct arrhythmia surgery in ventricular tachycardia: an experience with 18 consecutive patients].

18 patients with ventricular tachycardia (VT) underwent direct arrhythmia surgery between 1984 and 1988. There were 8 patients with ischemic VT, and 10 with nonischemic VT. Operative technique consisted of ablative procedures of the arrhythmogenic area determined by pre- and intraoperative mapping. Induced VT was usually unstable and transient during operation, so that instantaneous multi-point mapping was necessary in almost cases. For VT originated in the left ventricle or interventricular septum, the earliest excitation point determined by the epicardial mapping did not always predict the endocardial arrhythmogenic focus. Pre- and/or intraoperative endocardial mapping was important in this regard. Cryocoagulation (-150 degrees C, 120 sec) was mainly used as an ablative procedure; for ischemic VT, endocardial resection was added, and in nonischemic VT originated in the right ventricular outflow tract, transmural resection was combined with the cryoablation. In performing surgery for nonischemic VT, care must have been taken to make transmural cryocoagulation because the arrhythmogenic focus could exist intramurally. There were no operative deaths. In one patient with nonischemic VT, reoperation was required. After a mean follow-up of 17 month, all the patients are free from sustained VT.

Adolescent↗
PubMed1989

[Studies on intraoperative cardiac mapping].

Precise determination of the arrhythmogenic area by the intraoperative cardiac mapping procedure is a prerequisite to successful surgical therapy for tachyarrhythmias. Because of the limitation of time during operation, mapping should be performed precisely and quickly. For this purpose we have developed and used an on-line portable minicomputer system (modified HPM-6500; Fukuda Denshi Co., Ltd.). A ventricular epicardial excitation sequence map is acquired by measuring the conduction time difference for 51 predetermined points on the whole ventricular surface. The measured data are instantaneously digitized and computed to be displayed as an isochornous map in real time basis. Similar program is available for atrial excitation map. With this system it takes only about ten minutes to get an epicardial isochornous map. Recently a multi-channel signal-processing unit has been incorporated in the HPM-6500. With the use of a sock electrode or a card electrode, a map can be obtained on a few cardiac contractions. Multi-point simultaneous mapping has been proved to be especially important to get a VT isochornous map, for induced VTs during operation are usually unstable and transient.

Arrhythmias, Cardiac↗