Search for the Pair Production of Dark Particles X with K_{L}

We present the first search for the pair production of dark particles X via K_{L}^{0}→XX with X decaying into two photons using the data collected by the KOTO experiment. No signal was observed in the mass range of 40-110 MeV/c^{2} and 210-240 MeV/c^{2}. This sets upper limits on the branching fractions as B(K_{L}^{0}→XX)<(1-4)×10^{-7} and B(K_{L}^{0}→XX)<(1-2)×10^{-6} at the 90% confidence level for the two mass regions, respectively.

Study of the K_{L}→π

The rare decay K_{L}→π^{0}νν[over ¯] was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of (7.20±0.05_{stat}±0.66_{syst})×10^{-10}, three candidate events were observed in the signal region. After unveiling them, contaminations from K^{±} and scattered K_{L} decays were studied, and the total number of background events was estimated to be 1.22±0.26. We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of 4.9×10^{-9} on the branching fraction of K_{L}→π^{0}νν[over ¯] at the 90% confidence level.

Search for K_{L}→π

A search for the rare decay K_{L}→π^{0}νν[over ¯] was performed. With the data collected in 2015, corresponding to 2.2×10^{19} protons on target, a single event sensitivity of (1.30±0.01_{stat}±0.14_{syst})×10^{-9} was achieved and no candidate events were observed. We set an upper limit of 3.0×10^{-9} for the branching fraction of K_{L}→π^{0}νν[over ¯] at the 90% confidence level (C.L.), which improved the previous limit by almost an order of magnitude. An upper limit for K_{L}→π^{0}X^{0} was also set as 2.4×10^{-9} at the 90% C.L., where X^{0} is an invisible boson with a mass of 135 MeV/c^{2}.

Intravenous leiomyomatosis extending into the right ventricular cavity: one-stage radical operation using cardiopulmonary bypass--a case report.

The authors describe a 47-year-old woman with intravenous leiomyomatosis (IVL) extending into the right ventricular cavity. This rare entity is a neoplasm originating from smooth muscle of the uterus, with vermiform extensions into the inferior vena cava. The patient underwent a one-stage operation under simultaneous sternotomy and laparotomy, and radical excision of the tumor was successfully achieved with use of normothermic cardiopulmonary bypass. Although this tumor is histologically benign, it sometimes extends into the cardiac cavity and causes sudden death due to incarceration into the atrioventricular orifice. Moreover, recurrence or lung metastasis of IVL has been reported. The authors recommend a one stage-radical resection of the tumor or a two-staged operation within a short interval. In the literature, 24 surgical cases of the intravenous leiomyomatosis with intracardiac extension have been reported. The diagnosis and surgical treatment of this tumor are reviewed and discussed.

Paramalleolar bypass concomitantly with extended endarterectomy for limb-threatening ischemia: A case report.

A 74-year-old male was admitted to our university hospital with a refractory ulcer of the left third toe. The ankle pressure index was 0.43. On his angiogram, the popliteal artery was totally occluded in the distal site, while the peroneal artery was solely patent and inflowed into the distal posterior tibial artery. At surgery, endarterectomy of 7 cm in length was performed on the tibioperoneal trunk of the occluded popliteal artery following patch repair using a saphenous vein to restore the genicular arterial network and infrapopliteal arteries. Thereafter, the bypass surgery was performed using the in situ saphenous vein from the patent proximal popliteal artery to the distal posterior tibial artery. The postoperative angiogram showed patency of the graft as well as restoration of the genicular arterial network and infrapopliteal arteries. The ankle pressure index improved to 1.04, and the refractory ulcer was completely cured one month after revascularization.

Valvular heart disease. A comparative study of results after primary operation, reoperation, and after multiple reoperation.

Reoperation for valvular heart disease has been associated with a higher operative mortality than primary operations, especially in patients who had multiple prior operations. We have analyzed the 226 consecutive patients who underwent valve replacement. These involved 163 primary operations, 52 first reoperation, and 11 second/third reoperations. Preoperative left ventricular dysfunction was more severe, and operation time and cardiopulmonary bypass time were significantly greater according to the number of operations, associated with a greater amount of intraoperative blood loss. The operative mortality after a second/third reoperation was 27.3%, which was significantly higher than that after primary operation (6.7%) (p < 0.05), and that after first reoperation (5.8%) (p < 0.05). Seven (64%) patients who underwent a second/third reoperation had poor preoperative left ventricular function (%FS < 25%), and 5 (71%) of these required postoperative mechanical supports, and 3 (60%) of the 5 patients died of low output syndrome. We have found that poor preoperative left ventricular function and the duration on cardiopulmonary bypass, but not the number of reoperation were correlated with operative mortality. Continued efforts should be directed to decrease the mortality for multiple reoperative valve surgery.

Usefulness of postoperative percutaneous cardiopulmonary support using a centrifugal pump: retrospective analysis of complications.

Between January 1992 and December 1997, we employed percutaneous cardiopulmonary support (PCPS) using a centrifugal pump in 25 patients. In 21 of them, PCPS was used postcardiotomy. These patients could not be weaned from cardiopulmonary bypass due to profound ventricular failure. As for the other 4 patients, PCPS was used preoperatively for profound cardiogenic shock, a thrombosed valve, a stuck valve, and pulmonary embolization. Nine patients (43%) were weaned from PCPS (Group 1), and 3 (14%) were discharged from the hospital. The other 12 patients (57%) had perioperative extensive myocardial infarction and could not be weaned (Group 2). The causes of death were bleeding and multiple organ failure (MOF) associated with ventricular failure. The reasons for MOF were perioperative massive transfusion and hepatic congestion caused by sustained ventricular failure. To increase the survival rate, complete hemostasis and prevention of increased central venous pressure by early use of PCPS are necessary.

Mild hypothermia for temporary brain ischemia during cardiopulmonary support systems: report of three cases.

Recovery without residual neurological damage after cardiac arrest with temporary cerebral ischemia is rare. Therefore, it is most important that every effort is made to prevent brain damage occurring immediately after successful cardiopulmonary resuscitation. We report herein the cases of three patients who suffered either cardiogenic or hypovolemic shock and were resuscitated by a cardiopulmonary support system followed by mild hypothermia. All three patients recovered completely without any neurologic damage. The outcomes of these three patients demonstrated that mild hypothermia may be important for cerebral preservation after cardiopulmonary resuscitation.

Evaluation of local platelet deposition during laser thermal angioplasty.

Laser thermal angioplasty is one of the brand-new transluminal interventions for arterial occlusive disease. And one of the most important prognostic factors of this intervention is the degree of local platelet deposition which causes the acute platelet thrombus and increases the proliferation of smooth muscle cells. The purpose of this study is to assess the degree of platelet deposition on the laser ablated area and to investigate the optimal conditions of laser ablation from the point of thrombogenesis. First of all, the laser ablations of various delivered energy were carried out on canine femoral arteries, then thrombus formation after laser ablation was evaluated with angioscopy. No thrombus was recognized on all ablated areas in the cases with a laser energy of 16 Joule (J) and 20 J. On the other hand, small thrombus on the ablated area was observed in 1 of 4 cases (25%) with that of 24 J, and in 2 of 4 cases (50%) with that of 30 J. Then, the degree of platelet deposition on the laser ablated area was evaluated with platelet labeled radioimmunoassay. Laser ablations were employed in canine femoral arteries varying delivered laser energy. There were no differences in the numbers of platelet deposition when the laser energy for one shot was within 24 J. The numbers of platelet deposition with a laser energy of 30 J and 45 J were significantly (p < 0.05) higher than those with a laser energy within 24 J. The numbers of platelet deposition were gradually increased related to the frequency of laser ablations, and the numbers of platelet depositions in 10 repeated laser ablations of 16 J and 20 J were significantly (p < 0.05) higher than that in single laser ablation of 16 J and 20 J. From the aspect of local platelet deposition, the optimal laser energy for one shot should be restricted within 24 J and the repeated ablation was the most appropriate method of laser thermal ablation.

Successful surgical treatment of an Edwards type IIIB right aortic arch aneurysm: report of a case.

A true aneurysm of the right aortic arch which accompanies various branching characteristics is very rare. We report herein the successful surgical treatment of an elderly patient found to have an Edwards type IIIB right aortic arch aneurysm encircling and compressing the trachea. The complete right aortic arch and right subclavian artery were reconstructed through the inside of the aneurysm using selective cerebral perfusion. The patient recovered well, with no residual neurologic deficit and with resolution of the dyspnoic attacks he had suffered preoperatively.

[Early and late surgical mortality of acute type A aortic dissections by open distal anastomosis with deep hypothermic retrograde cerebral perfusion].

We have analyzed the operative results and the long-term prognosis of Stanford type A acute aortic dissections. Between 1981 and 1997, 57 patients underwent surgical repairs of acute type A aortic dissection. In the earlier period (1981-1990; n = 21), almost all the operations were performed under aortic cross-clamping with conventional cardiopulmonary bypass, while in the later period (1991-1997; n = 36), radical resections and graft replacements under open distal anastomosis with deep hypothermic retrograde cerebral perfusion (RCP) were performed in 24 patients (66.7%) and with selective cerebral perfusion in 3 (8.3%). The hospital mortality rates were 33.3% in the earlier period and 16.7% in the later period. Two (8.3%) of 24 patients employed RCP failed by preoperative rupture to pulmonary artery and myocardial infarction. Reoperations for enlargement of the remained false lumen were performed in 4 in the earlier period, of whom 2 patients were dead. In the later period, 7 patients were reoperated on, and all patients survived. Over all actuarial survival rates were 57.1% at 5 year and 44.4% at 10 year in the earlier period, while it was 70.7% at 5 year in the later group. We concluded that retrograde cerebral perfusion allows resection of the dissected aorta including primary entry as well as open distal anastomosis, which contributes to the improvement of early and long-term results for acute type A aortic dissection.

Surgical results of composite graft replacement of the aortic root aneurysm.

From 1986 to 1996, 20 patients underwent aortic root replacement. All of the patients had annulo aortic ectasia (AAE); Six had DeBakey type I aortic dissection, three were acute dissections associated with Marfan's syndrome; three had previously undergone the Koster-Collins operation. During 11 years, the original Bentall procedure (1986-91), the Cabrol procedure (1991-), and the modified Bentall procedure (Carrel patch or Piehler technique) were performed. There was only 1 hospital mortality (5.0%). Four patients died during the follow-up period (mediastinitis, myocardial infarction, cerebral bleeding, and rupture of the arch aneurysm). Only 2 patients required reoperation (repair of a pseudoaneurysm of the right coronary artery and paravalvular leakage of the aortic valve replacement). The satisfactory outcomes were the result of the full-thickness anastomoses performed during coronary artery reconstruction.

Impact of retrograde cerebral perfusion with posterolateral thoracotomy on distal arch aneurysm repair.

BACKGROUND: Repair of distal aortic arch aneurysms is difficult to accomplish through a median sternotomy or left thoracotomy, and stroke and respiratory disorders often become lethal complications with the use of circulatory arrest. We investigated the use of retrograde cerebral perfusion with a posterolateral thoracotomy in the repair of distal arch aneurysms. METHODS: Thirty-eight patients underwent repair of a distal arch aneurysm. They were divided into three groups according to the method of surgical repair used. Sixteen patients (group I) underwent proximal anastomosis of the graft with the use of an aortic cross-clamp. Eight patients (group II) underwent open proximal anastomosis with the use of retrograde cerebral perfusion (oxygenated blood perfusion through a superior vena cava cannula) and a median sternotomy and anterolateral thoracotomy. Fourteen patients (group III) also underwent open anastomosis with the use of retrograde cerebral perfusion (cerebral perfusion through blood returned to the right atrium with the patient in the Trendelenburg position) and a posterolateral thoracotomy. RESULTS: The operative mortality rate in group I was 25.0%; 4 of 16 patients died of stroke, myocardial infarction, and intestinal necrosis. In group II, 3 of 8 patients (37.5%) died of respiratory failure and aortic dissection. In group III, only 1 of 14 patients (7.1%) died, as a result of heart failure. CONCLUSIONS: The use of retrograde cerebral perfusion with a posterolateral thoracotomy is an alternative method that minimizes the risk of stroke and respiratory failure during distal aortic arch operations.

Reoperation after repair of type A and B dissecting aneurysm.

BACKGROUND: In the late postoperative period after repair of an aortic dissection or dissecting aneurysm, reoperations may be required. The interval to reoperation, size and location of intimal tear, and results of reoperation were evaluated. METHODS: Between January 1982 and April 1997, 138 patients underwent surgery for Stanford type A (90 patients) or type B (48 patients) dissections of the aorta. The entire aorta was evaluated in postoperative follow-up by computed tomography and magnetic resonance imaging for 6 months to 15 years. Reoperations were performed in 14 (10.1%) patients with changes in the aneurysms at the site of the initial repair or in the distal aorta. Selective cerebral perfusion or retrograde cerebral perfusion with deep hypothermia was used in the repair of the ascending, arch, and distal arch aneurysms. Reoperations included aortic root reconstruction (n=3), resection of a pseudoaneurysm (n=1), and replacement of the ascending aorta (n=1), arch (n=5), descending aorta (n=2), thoracoabdominal aorta (n=1), or abdominal aorta (n=1). Secondary reoperations were performed in four patients (replacement of the arch [n=2], thoracoabdominal aorta and abdominal aorta). Consequently two patients had subtotal aortic replacements. The aneurysms were caused by an anastomotic leak, a new intimal tear following aortic cross-clamping, a second intimal tear in the distal arch or abdominal aorta, and Marfan syndrome. RESULTS: Two patients (2/18 11.1%) died of bleeding or low output syndrome. Two patients died of graft infection or prosthetic valve infection 3 months after surgery respectively. CONCLUSIONS: 1) The surgical results of reoperation for type A and B dissections were good. 2) Close postoperative follow-up of the patent false lumen in the entire aorta was necessary. 3) At the initial operation, total resection of the intimal tear in the aortic arch in low-risk patients reduced the risk of reoperation.

Open distal anastomosis in retrograde cerebral perfusion for repair of ascending aortic dissection.

BACKGROUND: In patients with aortic dissection, a patent distal false lumen at long-term follow-up leads to complications. We investigated the feasibility of performing an open distal anastomosis using retrograde cerebral perfusion. METHODS: Over a 10-year period, 41 patients with acute type A aortic dissection underwent 43 surgical repairs. In 1991, an open distal anastomosis using retrograde cerebral perfusion (group 2) was introduced to replace the standard aortic cross-clamp method (group 1). The mean retrograde cerebral perfusion time was 47.3 minutes (range, 22 to 67 minutes), and there were no neurologic sequelae in surviving patients. RESULTS: The operative mortality rate was 18.5% in group 1 and 18.7% in group 2. At long-term follow-up, dilatation of the false lumen (more than 50 mm in diameter) occurred in 9 of 18 patients (50%) in group 1, and 2 patients died of aortic rupture. There were no deaths in group 2, and dilatation of the distal false lumen occurred in only 15.4% of patients (p < 0.05). CONCLUSIONS: The use of retrograde cerebral perfusion in patients with acute aortic dissection provides adequate time to perform a safe, open, distal anastomosis, and could decrease significantly the rate of enlarged, patent, false lumina.

[Surgical treatment of aortic dissection (Stanford type A) using hypothermic retrograde cerebral perfusion in patients older than 70 years of age].

Since 1991, 27 consecutive patients with aortic dissection (Stanford A) have been operated on using deep hypothermic retrograde cerebral perfusion (RCP). There were no differences in ECC time (247 +/- 15 vs 307 +/- 22 min), and RCP time (47 +/- 2 vs 47 +/- 3 min) between the aged (> or = 70 y.o., n = 11) and non-aged (< 70 y.o., n = 16) group. Although the aged group showed the higher incidences of postoperative neurological complications of prolonged emergence (2 cases) and delirium (3 cases), respiratory disorder (3 cases), and renal dysfunction (3 cases), there was no significant difference in hospital mortality (18% in the aged vs 13% in the non-aged). We concluded that RCP is well acceptable procedure for surgical treatment of the aged patients with aortic dissection.

Cerebral complications and distal false lumen in the repair of aortic dissection with retrograde cerebral perfusion.

BACKGROUND: In aortic dissection, patent distal false lumen at long-term follow-up leads to complications. We investigated the feasibility of an open distal anastomosis under retrograde cerebral perfusion. METHODS: During a 15-year period (1981-1995), 51 patients with type A dissection underwent 59 surgical repairs. In 1990, a distal open anastomosis with retrograde cerebral perfusion (group II) was introduced to replace the aortic cross clamp method (group I). Mean retrograde cerebral perfusion time was 50 minutes (range 22 to 65 minutes) with no neurologic sequelae in surviving patients. RESULTS: Operative mortality was 28.6% in group I, and 16.1% in group II. At long-term follow-up, dilatation of the false lumen (more than 50 mm in diameter) occurred in 56.2% (9/16) in group I, and 4 patients died of aortic rupture. There was no mortality in group II, and dilatation of the distal false lumen occurred in only 15.3% (p<0.05). CONCLUSIONS: Use of retrograde cerebral perfusion in aortic dissection allowed for adequate time to perform a safe, open, distal anastomosis. Intraoperative cerebral complications and enlarged patent false lumens decreased significantly.

A simple technique for the prevention of lower limb ischemia during femoral veno-arterial cardiopulmonary support.

OBJECTIVE: We describe a simple technique to prevent the lower limb ischemia during femoral veno-arterial cardiopulmonary support (CPS). PATIENTS: Between July 1994 and September 1995, five patients underwent the insertion of femoral veno-arterial CPS with distal limb perfusion for the treatment of circulatory collapse after cardiac surgery. METHODS: After CPS is established, the ipsilateral superficial femoral artery (SFA) is punctured downward with a 14-gauge Teflon catheter and connected to the side port of the membrane oxygenator. RESULTS: None of the patients were complicated by lower limb ischemia for up to 77 hrs on CPS with distal limb perfusion. CONCLUSIONS: Active perfusion through a 14-gauge Teflon catheter downstream to the ipsilateral SFA is effective in preventing lower limb ischemia during prolonged femoral veno-arterial CPS after cardiac surgery.

A new simplified method for laser sinus node modification without electrophysiological technique.

As the treatment of inappropriate sinus tachycardia, beta-adrenoreceptor blockade therapy is the most common method for pharmacological heart rate control, but it is occasionally limited by side effects of the drugs, especially in patients with cardiac dysfunction. On the other hand, cryoablation or surgical exclusion of the sinus node have not been accepted generally for their necessity of permanent pacemaker implantation. Modification of the sinus node function is a new method of nonpharmacological treatments, although the skillfull and troublesome technique is required. In this study, the efficacy and safety of laser sinus node modification without electrophysiological technique were investigated as a new simplified method. In six mongrel dogs, the laser-tissue interactions by epicardial Nd-YAG laser irradiation were investigated by measuring the diameter and the depth of the irradiated lesions. Laser irradiations were performed from the head to the tail on the sinus node areas directed only by terminal groove for the visual landmark without electrophysiological technique until about 25% decrease in heart rate occurred in other six open-chest dogs.