Hitoshi Hirose

A slow thrust slip event following the two 1996 Hyuganada Earthquakes beneath the Bungo Channel, southwest Japan

We report a “slow thrust slip event” that occurred beneath the Bungo Channel region, southwestern Japan. On Oct. and Dec., 1996, two Hyuganada earthquakes (both Mw = 6.7), followed by afterslips, occurred. In addition, a crustal movement characterized by an extremely slow rise was observed around the Bungo Channel, about 200 km north from the epicenters, and continued for about 300 days long. Assuming a slow slip on the plate boundary, we estimate its duration and surface displacements from GPS time series data by curve-fitting, and then, determine the fault slip distribution. We found that a slow slip without any earthquakes continued for nearly one year and released the seismic moment comparable to that of the Hyuganada earthquakes. Occurrence of the slow thrust slip event suggests that this kind of event may be a characteristic mode of stress release at a transition region of interplate coupling.

Repeating short- and long-term slow slip events with deep tremor activity around the Bungo channel region, southwest Japan

We report the repeating occurrence of short- and long-term slow slip events (SSE) which are accompanied by deep tremor activity around the Bungo channel region, southwest Japan. Both of these activities are detected by NIED Hi-net, which is composed of densely distributed observatories equipped with a set of tiltmeter and a high-sensitivity seismograph. Since the short-term SSE is small in magnitude, GPS can detect only the long-term SSE. Some of these episodes have nearly the same surface deformation pattern. This shows the existence of ‘slow slip patches’ on a plate interface, where the episodic slow slip is the characteristic slip behavior. We observe a change in periodicity and size of the short-term episode after the onset of the long-term SSE. Moreover, the long-term slow slip accelerates when the short-term activity takes place. This suggests that there is an interaction between these two types of SSEs.

Right ventricular rupture and tamponade caused by malposition of the Avalon cannula for venovenous extracorporeal membrane oxygenation

Placement of the Avalon Elite bicaval dual lumen cannula for venovenous extracorporeal membrane oxygenation (VV-ECMO) via the internal jugular vein requires precise positioning of the cannula tip in the inferior vena cava with echocardiography or fluoroscopy guidance. Correct guidewire placement is clearly the key first step in assuring proper advancement of the cannula. We report a case of unexpected wire migration into the right ventricle at the time of final cannula advancement, resulting in right ventricular rupture and tamponade. Transesophageal echocardiography is an important monitoring modality for appropriate placement of the VV-ECMO guidewire and Avalon cannula, and in particular, for early identification of potential complications.

Slow Earthquakes Linked Along Dip in the Nankai Subduction Zone

Three types of temporally linked slow earthquakes may limit nearby buildup of stress. We identified a strong temporal correlation between three distinct types of slow earthquakes distributed over 100 kilometers along the dip of the subducting oceanic plate at the western margin of the Nankai megathrust rupture zone, southwest Japan. In 2003 and 2010, shallow very-low-frequency earthquakes near the Nankai trough as well as nonvolcanic tremor at depths of 30 to 40 kilometers were triggered by the acceleration of a long-term slow slip event in between. This correlation suggests that the slow slip might extend along-dip between the source areas of deeper and shallower slow earthquakes and thus could modulate the stress buildup on the adjacent megathrust rupture zone.

Coronary artery bypass grafting using the gastroepiploic artery in 1,000 patients

BACKGROUND The gastroepiploic artery (GEA) has been used as a graft in 1,000 patients in our institution, and the clinical outcome and the angiographic long-term results were reviewed. METHODS Between June 1, 1991, and June 30, 2001, 1,000 consecutive isolated coronary artery bypass grafting procedures using the GEA were performed in the Shin-Tokyo Hospital Group. The perioperative data were retrospectively analyzed, and the late angiographic results, cardiac related events, and survival were examined. The end points of the follow-up study were death or the occurrence of a cardiac-related event. RESULTS The GEA was used in 767 men and 233 women (mean age, 63.8 +/- 9.4 years). The GEA was used as an in situ graft in 99.6% of patients and was anastomosed to the right coronary artery in 87.8% and the circumflex artery in 10.0%. In addition, the left internal mammary artery was used in 96.9% of patients, the right internal mammary artery in 28.5%, the radial artery in 41.7%, the inferior epigastric artery in 1.4%, and the saphenous vein in 40.1%. The hospital morbidity and mortality rates were 10.8% and 0.8%, respectively. No abdominal complications were observed. Postoperative myocardial infarction associated with GEA graft failure occurred in 2 patients. During the late follow-up of 4.0 +/- 2.3 years, cardiac-related events were observed in 155 patients. The actuarial 3- and 5-year event-free rates were 91.2% and 84.2%, respectively. There were 86 late deaths, 36 of which were cardiac related deaths. The actuarial 3- and 5-year survival rates were 96.6% and 92.6%, respectively. Angiography was performed on 437 patients within 1 year after operation and in 221 patients more than 1 year postoperatively (mean interval, 3.1 +/- 1.8 years). The actuarial 1-, 3-, and 5-year GEA graft patency rates were 98.7%, 91.1%, and 84.4%, respectively, and the actuarial 1-, 3-, and 5-year LIMA graft patency rates were 99.6%, 98.8%, and 97.0%, respectively (p < 0.0005). CONCLUSIONS The GEA was used for coronary artery bypass grafting with good perioperative results. However, the angiographic patency rate of the GEA was inferior to that of the internal mammary arteries. The late occurrence of angina attributed to GEA graft failure should be carefully monitored.

Twenty Years Experience With the Gastroepiploic Artery Graft for CABG

Background— To improve the longterm outcome after CABG, several strategies have been used using arterial conduits. Our 20 years experience with the right gastroepiploic artery (GEA) graft was evaluated. Methods and Results— In 1352 patients having CABG with the GEA graft, (1092 men, mean 63 years, 99% multivessel disease, and mean EF 0.51), internal thoracic artery, saphenous vein, and radial artery grafts were concomitantly used in 1312 (97%), 783 (58%), and 128 (8%) patients, respectively. The mean number of distal anastomoses was 3.1, and 2.4 coronary arteries were bypassed with arterial grafts. The sites for GEA grafting were 70 anterior descending, 268 circumflex, and 1089 right coronary arteries. The operative mortality was 1.26%. In 1118 follow-up patients (82.6%), 5, 10, and 15 years survival rates were 91.7%, 81.4%, and 71.3%, and the cardiac death-free survival rates were 95.8%, 91.7%, and 88.6%, respectively. The cumulative patency rate of the GEA graft was 97.1% at 1 month, 92.3% at 1 year, 85.5% at 5 years, and 66.5% at 10 years, respectively. In 172 skeletonized GEA grafts with 233 distal anastomoses, the patency rate at immediate, 1, and 4 years after surgery was 97.6%, 92.9%, and 86.4%, respectively. In 124 patients with late (5 to 17 years) restudy, patency rate was 96% (114/119) in the left internal thoracic artery, 87% (108/124) in GEA, and 68% (67/98) in saphenous vein grafts. New stenosis was uncommon in GEA. Conclusion— The GEA graft is a safe and effective arterial conduit for CABG.

Skeletonized radial artery grafting: improved angiographic results

BACKGROUND The radial artery has been used for coronary artery bypass grafting (CABG) but its early angiographic results were relatively inferior to that of the internal mammary artery, most likely due to spasm of the graft. To avoid vasospasm we harvested the radial artery using a skeletonized technique and spasm was completely reversed before use. The graft patency of the skeletonized radial artery was compared with the radial artery graft harvested as a pedicle. METHODS A total of 112 patients underwent isolated CABG using a pedicled radial artery between September 1, 1999, and August 31, 2000 (group P), and a total of 131 patients with a skeletonized radial artery between September 1, 2000, and August 31, 2001 (group S). An ultrasonic scalpel (Harmonic Scalpel; Ethicon EndoSurgery, Cincinnati, OH) was used for skeletonization and removing satellite veins and surrounding tissue. CABG was performed by the standard technique. Perioperative results were prospectively collected and compared between the two groups. Early angiographic results performed within 3 months were also compared. RESULTS There were two hospital deaths in group S. Major complications were observed in 11 (8.4%) in group S and 3 (2.7%) in group P (p = not significant [NS]). None were related to the radial artery graft. Angiography was obtained in 96 patients of group S and 76 patients in group P and revealed that the stenosis free graft patency rate of group S (138 of 143, 96.5%) was superior to that of group P (73 of 86, 84.9%) with p < 0.005. CONCLUSIONS Skeletonization of the radial artery with the ultrasonic scalpel is safe and contributes to reducing the incidence of early graft stenosis.

Coronary Artery Bypass Grafting Using the Radial Artery: Midterm Results in a Japanese Institute

BACKGROUND To avoid remote cardiac events associated with graft occlusions, arterial conduits are being increasingly utilized in coronary artery bypass grafting (CABG). The development of antispasmic agents has enabled the use of the radial artery as a graft conduit in CABG. METHODS Between December 1995 and December 1998, 920 consecutive isolated CABG operations were performed at Shin-Tokyo Hospital. The radial artery was used for graft conduits in 475 of these patients, and their data were analyzed in this study. The patients were followed to determine midterm graft patency, cardiac events, and survival. All data are given as mean +/- standard deviation. The end points were patient death or occurrence of cardiac events. RESULTS The radial artery was used in 475 patients (366 males and 109 females, with a mean age of 64.5+/-8.5 years). The left internal mammary artery was used in 94.9% of patients, the right internal mammary artery in 17.5%, the gastroepiploic artery in 50.9%, the inferior epigastric artery in 0.2%, and the saphenous vein in 39.2%. The in-hospital morbidity and mortality rates of the studied group were 12.8% and 0.6%, respectively. A major complication related to radial artery harvesting, compartment syndrome of the arm due to postoperative bleeding, was observed in 1 patient. No postoperative myocardial infarction attributable to radial artery bypass was observed. During the late follow-up period of 3.5+/-0.9 years, cardiac events were observed in 63 patients, giving actuarial 2- and 3-year event-free rates of 92.8% and 89.6%, respectively. A total of 24 late deaths were noted, including seven cardiac deaths, giving actuarial 2- and 3-year survival rates of 98.1% and 97.2%, respectively. Postoperative angiography was performed in selected patients. The cumulative graft patency rate of the radial artery was 93.0% during the mean angiographical follow-up period of 1.5+/-1.1 years. CONCLUSIONS No adverse effects were noted after CABG using a radial artery graft in this short- and midterm follow-up period.

Coronary artery bypass grafting for patients with non-dialysis-dependent renal dysfunction (serum creatinine ≧2.0 mg/dl)

INTRODUCTION Patients with renal dysfunction carry a risk of coronary atherosclerosis. The purpose of this study was to evaluate the outcome after coronary artery bypass grafting (CABG) in patients with decreased renal function (serum creatinine > or =2.0 mg/dl). METHODS We retrospectively analyzed consecutive patients who had undergone isolated CABG at Shin-Tokyo Hospital between May 1, 1991 and April 31, 2000. Preoperative, perioperative, and follow-up data of the non-dialysis-dependent patients with preoperative serum creatinine equal to or more than 2.0mg/dl (group R, n=59) were collected, and compared with those of the control patients (serum creatinine < 2.0, group C, n=1666). Group R was further divided into the off-pump and on-pump CABG group and their perioperative results were compared. RESULTS Group R included 51 males and eight females with a mean age of 66.4. The mean number of anastomoses was not significantly different between groups; however, clump time and pump time were longer in group R. Postoperative recovery was longer in group R than in group C, which is associated with a more frequent occurrence of major complications (28.8% in group R and 10.7% in group C, P<0.0001) and mortalities (6.8% in group R and 0.5% in group C, P<0.0005). The patients who underwent off-pump CABG experienced relatively faster recovery than those who underwent on-pump CABG, despite decreased renal function. At the mean follow-up of 2.4 years, the actuarial 3-year survival rate of groups R and C were 75.3 and 96.9%, respectively (P<0.0001), excluding hospital mortality. The actuarial 3-year cardiac event-free rate was 76.7% in group R and 87.3% in group C (P<0.05). CONCLUSIONS Patients with decreased renal function carry significant operative risks and require prolonged hospital care. Even after adequate surgical revascularization was completed, the long-term cardiac event-free and survival rates in the patients with renal dysfunction were inferior to the patients with normal renal function.

Weaning of extracorporeal membrane oxygenation using continuous hemodynamic transesophageal echocardiography.

BACKGROUND Venoarterial extracorporeal membrane oxygenation (VA ECMO) has been used for profound cardiogenic shock to bridge to decision, ventricular assist device(s) (VADs), or transplant. To assess ventricular function and volume status along with hemodynamics during ECMO weaning, we developed a standardized weaning protocol, guided by a miniaturized transesophageal echocardiography probe designed for continuous hemodynamic monitoring (hemodynamic transesophageal echocardiography [hTEE]). We reviewed our experience with this weaning protocol with hTEE guidance to assess if we could predict patient outcomes. METHODS During the academic year of 2011, hTEE-guided ECMO weaning was performed in 21 patients on VA ECMO. Left and right ventricular function and volume status were assessed by continuous hTEE, while attempting to wean ECMO after a standardized protocol. The clinical outcomes, management, and positive predictive value of the device were investigated and analyzed for this cohort of patients. RESULTS Of the 21 patients, 6 (29%) had left and right ventricular recovery and underwent optimal medical therapy or revascularization for underlying coronary artery disease; 7 (33%) had nonrecoverable left and right ventricular function; and 8 (38%) had right ventricular recovery without improvement of the left ventricular function. These 8 patients underwent left VAD placement; none subsequently developed profound right ventricular failure. The positive predictive value for ventricular recovery by hTEE was 100% using our standardized ECMO weaning protocol (95% confidence interval, 73%-100%). CONCLUSIONS The hTEE-guided ECMO weaning protocol accurately predicted the ability to wean ECMO to decision. This protocol can be applied by cardiac intensivists as a part of standard bedside intensive care unit assessment.