Kenji Matsuzaki

Wavelet analysis of bileaflet mechanical valve sounds

It has been reported that asynchronous leaflet closure in a bileaflet mechanical valve causes a split in the valve closing sound. We have previously reported that the continuous wavelet transform (CWT) with the Morlet wavelet as modified by Ishikawa (the Morlet wavelet) is the most suitable method among the CWTs for detecting a split in the bileaflet mechanical valve sound because this method can detect the highest frequency signal among the CWT methods with higher time resolution. This is the first article which discusses the acoustic properties of five types of bileaflet valves using the Morlet CWT. Similar behavior of the valve sound split intervals with wide fluctuations over consecutive heartbeats was found to be the common finding for all the bileaflet valves. This result suggests that fluctuation of the split interval proves the normal movement of both leaflets without movement disturbance. The mean differences in the split interval between these bileaflet valves were statistically significant, and the wavelet coefficients of the CWT showed characteristic scalographic patterns, such as a teardrop shape or a triangle beneath the split. However, these two findings gave no valuable information for the diagnosis of bileaflet valve malfunction. A split in the valve closing sound with a fluctuating interval was the common finding in these five normally functioning bileaflet valves, and careful observation of the splits behavior may be a key to diagnosis of bileaflet valve malfunction.

Assessment of hepatosplanchnic pathophysiology during thoracoabdominal aortic aneurysm repair using visceral perfusion and shunt

OBJECTIVE Despite the recognition of importance to avoid visceral ischemia during thoracoabdominal aortic aneurysm (TAAA) repair, the methodology of visceral perfusion seems still controversial and its pathophysiology has not been clearly understood. We investigated hepatosplanchnic metabolism during visceral perfusion/shunt in TAAA repair. METHODS Seventeen patients (10 male, 64+/-15 years old) who underwent elective TAAA repair using visceral perfusion/shunt under mild hypothermic distal aortic perfusion were retrospectively enrolled. Their aneurysm extension was type I and II in eight patients. In seven patients, four visceral arteries were perfused through a side-arm of distal aortic perfusion, while they were perfused by an independent pump in another five patients. In four of these 12 (two in each technique), visceral perfusion was converted into selective shunt after completion of aortic anastomosis. In the remaining five patients, four branches were initially perfused through a side-arm of distal aortic perfusion, and aortic perfusion was subsequently stopped after completion of aortic anastomosis. Hepatic venous oxygen saturation (ShO(2)), oxygen and lactate extraction ratio (OER, LER), and arterial ketone body ratio (AKBR) were measured at six time points. RESULTS There was no mortality, liver/renal dysfunction, or spinal cord injury. Two patients required re-exploration for bleeding. Fourteen patients were extubated within 24h postoperatively. Mean intensive care unit stay was 2.3+/-1.7 days. During visceral perfusion, OER raised (31+/-13% to 68+/-21%, p=0.0012) and ShO(2) decreased (67+/-12% to 34+/-24%, p=0.0026) significantly. They recovered to baseline at skin closure. During the same period, LER (41+/-22% to -1+/-34%, p=0.0035) and AKBR (0.47+/-0.13 to 0.20+/-0.08, p=0.0012) significantly decreased. AKBR recovered to baseline at skin closure, but LER did not. ShO(2) (R(2)=0.483, p=0.0257) and LER (R(2)=0.774, p=0.0018) at skin closure and LER after initiation of partial cardiopulmonary bypass (R(2)=0.427, p=0.0211) had significant correlation with postoperative peak serum bilirubin level. AKBR after initiation of partial cardiopulmonary bypass had significant correlation with postoperative peak serum alanine aminotransferase level (R(2)=0.289, p=0.0476). CONCLUSIONS Visceral perfusion/shunt in TAAA repair may avoid critical irreversible hepatosplanchnic ischemia but provide unphysiological blood flow to the liver and thus should be shortened.

Reoperations after failure of stent grafting for type B aortic dissection: report of two cases.

We describe our successful management of two patients who suffered complications after stent grafting for Type B aortic dissections. One patient was found to have stent-graft migration, which we treated with repeat aortic stent grafting, and the other patient had a proximal endoleak and total occlusion of the stent graft, which we treated with open surgical repair. We discuss the measures used to assist us in deciding on the most appropriate surgery, as well as the treatment alternatives.

Use of a soft reservoir bag in a fully heparin-coated closed-loop cardiopulmonary bypass system for distal aortic perfusion during aortic surgery.

A fully heparin-coated closed-loop cardiopulmonary bypass system has recently been introduced into clinical practice. Without a venous reservoir, however, it does not allow control of the preload to the heart. We connected a soft reservoir bag in parallel with a centrifugal pump to enable preload control and clinically evaluated this modified system for distal aortic perfusion during aortic surgery. We have used the modified system in 17 patients since November 2002. For venous drainage, we use long narrow cannulae (21 ± 2 French). We administered 1 mg/kg heparin without cardiotomy suction and 2 mg/kg heparin with suction. We compared the clinical results with those in 13 patients who underwent distal aortic perfusion with an open cardiopulmonary bypass circuit between January 2002 and February 2004. We also analyzed factors affecting the coagulation system in these 30 patients using multiple regression analysis. With the modified system, venous drainage was adequate despite the use of smaller cannulae, and heparin reduction was not associated with thrombotic complication or elevated D-D dimer levels. Abrupt rises in proximal aortic pressure on aortic cross-clamping could be avoided by allowing blood to drain into the soft reservoir bag. Clinical results were not different from those with an open system. In the multiple regression analysis, the peak activated clotting time tended to correlate with postoperative platelet counts. This system is effective in controlling the preload to the heart and allows the safe reduction of heparin dosage. It therefore seems useful for distal aortic perfusion during aortic surgery.

MDCT scan visualizes the adamkiewicz artery

Ischemic spinal cord injury is a serious complication after surgical repair of descending thoracic or thoracoabdominal aortic aneurysm. The Adamkiewicz artery (arteria radicularis magna [ARM]) is well known as a main feeder of the spinal cord. It originates from a segment of the intercostal or lumbar artery. The anatomical information of the ARM is important in conducting surgical strategy and may reduce the risk of postoperative neurologic deficit. To detect the ARM, selective angiography and magnetic resonance angiography have been used and reported to identify the ARM in 70% to 80% of patients. Alternatively, we have adopted a fourchannel multi-detector row computed tomographic (MDCT) scan that could successfully visualize the ARM. A 70-year-old man with a dissecting thoracoabdominal aortic aneurysm (DeBakey type IIIb; maximal diameter, 60 mm) underwent MDCT scan, as seen in this helical computed tomographic image (Fig 1A). The axial computed tomographic image shows the aneurysm that it is 60 mm in maximal diameter (Fig 1B). The study revealed the ARM originating from the left L1 lumbar artery and connecting to the anterior spinal artery with the classic “hairpin” bend, as seen in this preoperative MDCT scan with coronal reformation (Fig 2 [ASA aspirin]). His surgical repair consisted of aneurysmectomy and graft replacement with the reconstruction of the left T8 and T10 intercostal arteries, the left L1 lumbar artery, the celiac artery, the superior mesenteric artery, and the bilateral renal arteries. To minimize the duration of spinal cord ischemia, the left L1 lumbar artery was reconstructed first. The postoperative MDCT scan after the operation showed that the ARM was successfully reconstructed (Fig 3) and no neurologic complication was noticed. The MDCT scan was acquired under a protocol approved by our institutional review board. Computed tomographic images were obtained while injecting 100 mL of 350 mg/dL iodinated contrast medium at a flow rate of 5 mL per second through the right antecubital vein. A 0.5 second tube-detectors rotation time and helical pitch 5 were used. The patient was requested to breathe quietly during the scan. All computed tomographic data were processed in our three-dimensional imaging workstation to get sagittal and coronal reformations of 1-mm thickness. The MDCT scan is noninvasive to visualize the ARM and helpful in surgical repair of the descending thoracic or thoracoabdominal aortic aneurysm. Moreover, this study is economically acceptable and is not time consuming. Address reprint requests to Dr Shiiya, Department of Cardiovascular Surgery, Hokkaido University School of Medicine, Kita 14, Nishi 5, Kita-ku, Sapporo, Hokkaido 060-8648, Japan; e-mail: shiyanor@ med.hokudai.ac.jp. Fig 1.

Heparin reduction with the use of cardiotomy suction is associated with hyperfibrinolysis during distal aortic perfusion with a heparin-coated semi-closed cardiopulmonary bypass system

We sought to elucidate the effects of different anticoagulation levels and the use of cardiotomy suction on the postoperative coagulatory and fibrinolytic systems in patients undergoing distal aortic perfusion using a fully heparin-coated (semi-)closed cardiopulmonary bypass (CPB) system incorporating a soft reservoir bag. Thirty-two patients were divided into two groups: those who underwent cardiotomy suction (S group, 18 patients) and those who did not (N group, 14 patients). We administered 1–2 mg/kg heparin in the S group, which achieved an activated clotting time (ACT) of 345 ± 71 s. In the N group, we administered 0.7–1 mg/kg heparin, which achieved an ACT of 297 ± 52 s. Data on platelet counts and serum levels of fibrinogen, antithrombin III, D-dimer, and fibrin degradation products (FDP) were collected, and factors influencing these variables were analyzed by multiple regression analysis. Both the patient group and the initial ACT level were independent factors influencing postoperative levels of FDP and D-dimer, whereas peak ACT level and the use of selective visceral/renal shunt/perfusion, but not the patient group, were independent factors influencing the postoperative platelet counts. In the S group, a significant inverse correlation was found between the ACT and levels of FDP or D-dimer, whereas no correlation was found in the N group. The use of cardiotomy suction was associated with elevated FDP and D-dimer levels even when a fully heparin-coated semi-closed CPB system was used. Lower ACT levels with the use of cardiotomy suction were associated with higher FDP and D-dimer levels, whereas such a relationship did not exist when cardiotomy suction was not used.

Descending aorta to carotid bypass for takayasu arteritis as a redo operation

In Takayasu arteritis recurrent brain ischemia, due to bypass graft failure, is frequent. Redo bypass grafting from the ascending aorta may be at risk if a failing but patent graft that is critical for brain blood flow is present, because partial clamping the ascending aorta may disturb graft flow if the ascending aorta is short. We report such a patient who successfully underwent redo bypass grafting from the descending aorta. In type I Takayasu arteritis, this operation may be valuable because the descending aorta is usually disease free and brain blood flow is maintained during the operation.

Simultaneous coronary artery bypass grafting and ascending aorta bifemoral bypass in small aorta syndrome.

A 55-year-old man with severe coronary artery disease and aortoiliac occlusive disease with small aorta syndrome was admitted to our department with angina pectoris and bilateral claudication. Intravenous subtraction angiography showed total occlusion of the right common iliac artery and 99% stenosis of the left common iliac artery with a markedly hypoplastic infrarenal aorta only 9 mm in diameter. It also revealed 90% stenosis at the origin of the left subclavian artery. Coronary angiography showed total occlusion of the left anterior descending artery and 90% stenosis of the circumflex artery. Simultaneous coronary artery bypass grafting and an ascending aorta-bifemoral bypass were conducted using an in-situ right internal mammary artery graft, an autologous saphenous vein graft, and a Y-figured expanded polytetrafluoroethylene graft. Postoperative angiography showed grafts to the coronary and bifemoral arteries were patient. This combined procedure is useful for patients with coronary artery disease and aortoiliac occlusive disease, especially in those with small aorta syndrome.

Abdominal Compartment Syndrome Causing Respiratory Failure During Surgery for a Ruptured Descending Thoracic Aneurysm: Report of a Case

Elevated intra-abdominal pressure causing widespread organ dysfunction is known as abdominal compartment syndrome (ACS). The subject of our case report is a 64-year-old man who underwent repair of a ruptured descending thoracic aortic aneurysm (TAA) under deep hypothermic circulatory arrest. During the operation, decompression laparotomy was required to relieve intra-abdominal hypertension causing respiratory failure, before the patient could be weaned off cardiopulmonary bypass. We report this case to alert surgeons to the fact that ACS can occur during surgery on the thoracic aorta, especially if massive fluid resuscitation is required and venous drainage for extracorporeal circulation is less than optimal. Early recognition and prompt decompression by laparotomy is essential to save the life of the patient.

Proximal Aortic Replacement with Ascending-Descending Bypass for a Diffuse Aneurysm : Report of a Case

We performed successful ascending-arch aortic replacement and concomitant ascending-to-descending aorta bypass with exclusion of a descending thoracic aneurysm, via median sternotomy, for a ruptured aortic aneurysm involving the entire thoracic aorta. The patient was an 80-year-old man with cardiopulmonary dysfunction and a history of lung tuberculosis. This operation, which has been used for complex descending thoracic aortic lesions such as recoarctation, is a feasible option for a diffuse thoracic aortic aneurysm when single-stage repair is mandatory.