Biomedical subjects

Keiji Kamohara

Publications and source records attributed to Keiji Kamohara.

At least 19 recordsLinked to original sources

PubMed2007

Impact of left atrial appendage exclusion on left atrial function.

OBJECTIVES: We sought to investigate the short-term and midterm effects of left atrial appendage exclusion on left atrial function. Left atrial appendage exclusion is considered a possible therapeutic option for stroke prevention in patients with atrial fibrillation. Favorable outcomes have encouraged widespread use of left atrial appendage exclusion for cardiac surgical patients-even for patients in sinus rhythm who have stroke risk factors; however, the chronic effects on left atrial function of left atrial appendage exclusion are unclear. METHODS: Nineteen mongrel dogs (29.7 +/- 5.2 kg) in sinus rhythm were studied. The Doppler signals from the pulmonary venous flow, transmitral flow, and tissue Doppler imaging of mitral annular motion were obtained before and after left atrial appendage exclusion. Dogs were evaluated in the same manner at 7 days (n = 2), 30 days (n = 7), or 90 days (n = 10) after left atrial appendage exclusion. RESULTS: Except for a significant increase in early diastolic transmitral flow velocity after left atrial appendage exclusion (P = .01), no significant differences were found in any parameters related to the transmitral flow and tissue Doppler imaging measurements throughout follow-up. The systolic components of pulmonary venous flow at follow-up revealed a significant reduction relative to baseline (peak systolic velocity P < .0001, systolic velocity-time integral P < .0001), despite the lack of significant changes in left atrial pressure, left ventricular volume, and stroke volume. CONCLUSION: Left atrial appendage exclusion may affect left atrial reservoir function in the short-term and midterm periods. Further long-term studies with more clinically relevant models are needed.

Animals↗

PubMed2006

Ventral cardiac denervation increased right coronary arterial blood flow.

BACKGROUND: Cardiac denervation accompanied with coronary artery bypass surgery has been widely performed for the treatment of vasospastic angina associated with atherosclerotic coronary artery disease. However, the effect of cardiac denervation on phasic coronary blood flow patterns of the left anterior descending coronary artery (LAD), left circumflex coronary artery (LCX) and right coronary artery (RCA) remains unknown. This study aimed to investigate the effect of cardiac denervation on phasic coronary blood flow patterns of the LAD, LCX and RCA. METHODS: Phasic coronary blood flow patterns were analyzed using three flow probes placed around the LAD, LCX and RCA with and without LAD stenosis. Ventral cardiac denervation (VCD) was performed in 8 pigs, and 16 pigs were used as control subjects. Autonomic activities before and after the VCD were quantified by wavelet analysis of heart rate variability. RESULTS: The mean LAD flow (34.4+/-9.4 to 32.6+/-7.1 ml/min, p=0.638) and mean LCX flow (26.3+/-10.2 to 27.2+/-6.0 ml/min, p=0.825) showed no significant change after VCD, while the mean RCA flow (31.3+/-9.0 to 38.2+/-11.2 ml/min, p=0.003) significantly increased. The hemodynamic variables in the VCD group were well maintained after creation of LAD stenosis, while they deteriorated in the control group. The low-frequency components, high-frequency components and their ratio did not change after VCD. CONCLUSIONS: VCD prevented the deterioration of cardiac function after creation of an LAD stenosis and resulted in an increase of the mean RCA flow. VCD did not affect autonomic nervous system activity.

Angina Pectoris↗

PubMed2006

Transmural distribution of myocardial blood perfusion and phasic coronary blood flow pattern in a canine model of acute ischemia.

BACKGROUND: Although several investigators have analyzed coronary artery blood flow under various conditions, almost all these studies have measured only some branches of the left anterior descending (LAD), left circumflex (LCX), or right coronary (RCA) artery. METHODS: In a canine model of acute ischemia (n = 5), we simultaneously assessed (a) regional myocardial blood perfusion using microspheres and (b) phasic coronary blood flow patterns as measured by three epicardial flow probes placed around the LAD, LCX, and RCA. RESULTS: The results from this study indicated that the LAD supplies blood to the epicardial (r = 0.687, p<0.0001), midwall (r = 0.556, p = 0.0021), and endocardial layers (r = 0.666, p = 0.0001) of the LAD area; the LCX supplies the midwall (r = 0.514, p = 0.0051) and endocardial layer (r = 0.621, p = 0.0004) of the LCX area, antero-lateral papillary muscle (r = 0.548, p = 0.0025), and postero-medial papillary muscle (r = 0.641, p = 0.0002), especially during the diastolic phase; and the RCA supplies the right ventricular apex (r=0.559, p=0.0020), left atrium (r = 0.618, p = 0.0005), right atrium (r = 0.471, p = 0.0114), and postero-medial papillary muscle (r = 0.486, p = 0.0088), especially during the systolic phase. CONCLUSIONS: These results are potentially relevant to understanding the physiology of myocardial blood perfusion and to improving treatment of acute myocardial ischemia and infarction.

Animals↗

PubMed2006

Experimental study of new diagnostic system for coronary artery disease using coronary transit index.

OBJECTIVES: Noninvasive cardiac imaging techniques have had an increasing role in the diagnosis of coronary artery disease. However, these techniques are not widely available as a tool in the office setting. The purpose of this study was to provide an accurate assessment of coronary artery disease for screening purposes using Coronary Transit Index (CTI) assessment with small, high-resolution gamma cameras. METHODS: Total coronary blood flow was measured with ultrasonic flow probes placed around the left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery in a total of 33 conditions in 5 healthy mongrel dogs. The coronary blood flow was reduced stepwise with vascular occluders placed around the coronary arteries. The procedure for obtaining CTI included 4 parts: 1) The animal was injected intravenously with a bolus of a radioactive tracer (2.5-5.0 mCi of (99m)Tc-DTPA); 2) Dedicated gamma sensors monitored the passage of the injected bolus; 3) Time-activity curves were measured at the left ventricle with and without its wall; 4) The ratio of the washout rates of the 2 curves determined the CTI. RESULTS: Coronary Transit Index was successfully obtained from the left ventricle. The coronary blood flows measured by flow probes were well correlated with the regional myocardial blood flow. The percentage of the baseline value of the total coronary blood flow had the highest correlation (R=0.807, p<0.0001) with the Coronary Transit Index. CONCLUSIONS: These data indicated that a new diagnostic system using CTI successfully identified reduced coronary blood flow.

Animals↗

PubMed2006

Surgical revascularization for acute coronary syndrome: comparative surgical and long-term results.

OBJECTIVE: The purpose of this study was to evaluate the adequate timing of coronary artery bypass grafting (CABG) for acute coronary syndrome (ACS). METHODS: In our institution, emergency CABG has been avoided when possible for ACS patients favoring stabilization with medical therapies, including intra-aortic balloon pumping or percutaneous coronary intervention. After thorough preoperative examinations, an urgent CABG is performed. A total of 67 patients with ACS underwent CABG, comprised of 33 patients receiving an emergency CABG (emergent group: E-G) and 34 patients receiving an urgent CABG (urgent group: U-G). The early and long-term results were evaluated retrospectively. RESULTS: Preoperatively, the incidences of acute myocardial infarction and cardiogenic shock were significantly higher in E-G. No significant differences were found in the intraoperative factors except for the number of distal anastomoses (2.5 in E-G vs. 3.1 in U-G, p=0.01). The hospital mortality was 9.1% in E-G, and 2.9% in U-G, with no significant difference between the groups. Moreover, no patient in U-G necessitated emergency CABG while waiting for surgery. The patency rate of the grafts was 100% in E-G, and 96.2% in U-G. The 5-year survival rate excluding in-hospital death was 80.3% in E-G, and 78% in U-G (p>0.05). The 5-year cardiac event-free rate was 80.3% in E-G, and 80.9% in U-G (p>0.05). CONCLUSION: An emergency CABG can be reserved for ACS patients when symptoms and hemodynamic state are stabilized with medical therapies. Improvements in long-term results can be expected after high quality and complete surgical revascularization.

Aged↗

PubMed2006

Aortic dissection late after aortic valve replacement.

We experienced 3 cases of an aortic dissection occurring late after an aortic valve replacement, and successfully treated by an aortic root replacement. An aortic dissection involving the ascending aorta can develop late after an aortic valve replacement, and such an occurrence is associated with a high mortality and morbidity. The development of effective surgical strategies at the initial aortic valve surgery, strict control of blood pressure after aortic valve replacement, serial evaluations of aortic size, and the prophylactic replacement of the ascending aorta for patients with aortic dilatation after aortic valve replacement, all play clinically important roles in preventing an aortic dissection after aortic valve replacement. When an aortic dissection occurs in patients with a previous aortic valve replacement, an aortic root replacement should be performed in order to avoid leaving the fragile diseased aortic wall including the sinus of Valsalva.

Adult↗

PubMed2006

Complete rupture of the posterior papillary muscle caused by late reperfusion for acute myocardial infarction.

We describe a patient with acute mitral regurgitation due to complete rupture of the papillary muscle immediately after successful late reperfusion for inferior myocardial infarction. An 81-year-old woman was admitted complaining of mild chest discomfort. Although the electrocardiograms, biochemical test results, and her clinical history showed that several days had passed since the onset of acute myocardial infarction, a late coronary stenting was performed. Immediately after successful stenting, she suddenly developed acute pulmonary edema, leading to cardiogenic shock. In addition to high pulmonary capillary wedge pressure (mean 35 mmHg), color Doppler imaging revealed massive mitral regurgitation caused by complete rupture of the posterior papillary muscle. Emergent mitral valve replacement with a prosthetic valve was performed, saving the patient. Hence, late reperfusion should be considered carefully when treating a patient with a high risk, such as an elderly patient or a patient with single-vessel disease or initial transmural myocardial infarction.

Aged, 80 and over↗

PubMed2006

A safer technique of aortic root replacement after aortic valve replacement.

Aortic root replacement after aortic valve replacement (AVR) is often complicated by bleeding around the aortic root, which increases the risk of morbidity and mortality, making it a technically challenging procedure. We describe a new technique of aortic root replacement designed to minimize bleeding around the aortic root. This surgical technique focuses on safe dissection and exposure of the aortic root to avoid inadvertent entry into the right atrium or right ventricle; on modifying the proximal anastomosis of the graft to the aortic annulus; and on performing a coronary artery reimplantation that achieves complete hemostasis at the suture lines. We performed aortic root replacement after AVR in four patients over a 4-year period, without encountering any bleeding around the aortic root.

Adult↗

PubMed2006

Evaluation of a novel device for left atrial appendage exclusion: the second-generation atrial exclusion device.

BACKGROUND: The left atrial appendage is a frequent source of thromboemboli in patients with atrial fibrillation. Exclusion of the left atrial appendage may reduce the risk of stroke in patients with atrial fibrillation. The atrial exclusion device, previously developed to perform left atrial appendage exclusion on a beating heart, was modified to accommodate different anatomic patterns of the human left atrial appendage and to ensure uniform pressure and occlusion. The purpose of this study was to evaluate this second-generation atrial exclusion device during a midterm period in a canine model. METHODS: Ten mongrel dogs (mean weight 28.9 +/- 4.6 kg) were used in this study. The atrial exclusion device, constructed from two parallel and rigid titanium tubes and two nitinol springs with a knit-braided polyester fabric, was implanted at the base of the left atrial appendage through a left thoracotomy on a beating heart using a specially designed delivery tool. Dogs were evaluated at 30 days (n = 4) and 90 days (n = 6) by epicardial echocardiography, left atrial and coronary angiography, gross pathology, and histologic inspection. RESULTS: Device implantation was performed without complications in all dogs. Complete left atrial appendage exclusion without device migration or hemodynamic instability was confirmed, and there was no damage to the left circumflex artery or pulmonary artery. Macroscopic and microscopic assessments revealed favorable biocompatibility during midterm follow-up. CONCLUSION: The atrial exclusion device enabled rapid, reliable, and safe exclusion of the left atrial appendage. Clinical application may provide a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation.

Animals↗

PubMed2006

An experimental rabbit model for off-pump left ventricular reconstruction following left ventricular aneurysm.

BACKGROUND: Cardiac electromechanical remodeling following left ventricular reconstruction (LVR) surgery is not fully understood. Further development of an animal model will facilitate investigations in this area. In the present study, we aimed to establish a novel LVR procedure without the use of cardiopulmonary bypass in a rabbit left ventricular (LV) aneurysm model. METHODS: LV aneurysm was created in 6 rabbits by ligation of the distal left coronary artery. More than a month later, LVR aneurysm surgery was performed off-pump using a purse-string suture around the aneurysm. Cardiac dimensions and function were evaluated using echocardiographic techniques perioperatively and 4 weeks after LVR surgery. Six structurally normal hearts were used as controls. RESULTS: LVR surgery was successfully performed in all 6 rabbits. Both LV end-diastolic volume (LVEDV, 4.6 +/- 0.9 to 3.3 +/- 0.6 mL; P < .01) and LV end-systolic volume (LVESV, 2.5 +/- 0.6 to 1.5 +/- 0.2 mL, P < .01) were decreased immediately postsurgery versus presurgery, and LV ejection fraction (LVEF) was increased (44.5 +/- 5.3 to 55.6 +/- 4.8%, P < .001). For comparison, in normal rabbits (n = 6), LVEDV, LVESV and LVEF were 3.1 +/- 0.7 mL, 1.2 +/- 0.5 mL, and 64.5 +/- 8.8%, respectively. During follow-up, one rabbit died 3 weeks after surgery from an unknown cause. In the remaining 5 animals, improvements of LVEDV (3.7+/- 0.4 mL, P < .05), LVESV (1.7 +/- 0. 3 mL, P < .01), and LVEF (53.1 +/- 2.8%, P < .01) were maintained versus presurgery values for more than 4 weeks after LVR. CONCLUSIONS: Off-pump LVR of rabbit LV aneurysm is an effective and less invasive surgery that resulted in sustained improvement in cardiac function with no gross intraoperative or postoperative mortality. This may be a useful model for investigations of electromechanical remodeling following LVR.

Animals↗

PubMed2005

Phasic coronary blood flow pattern during a continuous flow left ventricular assist support.

OBJECTIVE: Continuous flow left ventricular assist devices (LVADs) have been introduced and tested as a bridge to heart transplantation, bridge to recovery, and destination therapy, and several studies have been conducted to assess the physiologic effects of continuous flow LVADs. However, the effect of reduced pulsatility on the phasic coronary blood flow pattern is unknown. The aim of this study was to investigate the phasic coronary blood flow patterns during continuous flow LVAD support. METHODS: Phasic coronary blood flow patterns and hemodynamic data were analyzed using three flow probes placed around the left anterior descending coronary artery (LAD), left circumflex coronary artery (LCX), and the right coronary artery (RCA) in 16 pigs before and after initiating the LVAD support with or without creating LAD stenosis. RESULTS: The total coronary blood flow (TCBF, 112.8+/-31.4 mL/min) gradually decreased when the continuous flow LVAD support increased to 2.0 L/min (110.7+/-29.0 mL/min, P = 0.571), 2.5 L/min (103.7+/-26.1 mL/min, P = 0.079), and 3.0 L/min (101.5+/-27.2 mL/min, P = 0.027) because of decreases in LAD flow and LCX flow. LVAD support caused decrease in systolic and peak systolic LAD flow, LCX flow, and RCA flow, whereas diastolic RCA flow increased. In the presence of LAD stenosis, the TCBF (97.7+/-36.1 mL/min) decreased when the continuous flow LVAD support increased to 2.0 L/min (83.9+/-22.1 mL/min, P = 0.029), 2.5 L/min (83.2+/-25.2 mL/min, P = 0.012), and 3.0 L/min (87.6+/-23.4 mL/min, P = 0.005) because of decreases in LCX flow. CONCLUSION: Use of a continuous flow LVAD decreased TCBF, LAD flow, and LCX flow secondary to reduced systolic LAD flow and LCX flow, and decreased TCBF and LCX flow in the presence of LAD stenosis. These findings are potentially relevant to understanding the physiology of myocardial blood perfusion during continuous flow LVAD support especially in patients with coronary artery disease.

Animals↗

PubMed2005

MagScrew total artificial heart in vivo performance above 200 beats per minute.

PURPOSE: Downsizing pulsatile devices requires an increase of beat rate if flow capacity is to be maintained. We applied this concept to the preclinical MagScrew total artificial heart (TAH). DESCRIPTION: The device fills passively with a stroke volume of 45 ml and beat rates up to 250 beats per minute (bpm). EVALUATION: Stable hemodynamics were observed during a 30-day bovine implant with a flow of 8.7 +/- 1.2 L/min at beat rates of 204 +/- 18 bpm. Device filling was exceptional up to 250 bpm generating flow of greater than 12 L/min. Beat rate adapted to preload in a way similar to a Frank-Starling response. Left and right atrial pressures were balanced. The aortic pulse pressure was 49-70 mm Hg, which translates to a pulsatility index of 0.49-0.77. Organ functions were preserved and blood damage did not occur. CONCLUSIONS: Increasing the beat rate while downsizing the MagScrew TAH was successful with strong flow generation by passive filling. Pulsatility was maintained at high beat rates. This innovative approach may be used to develop small pulsatile pumps.

Animals↗

PubMed2005

A novel device for left atrial appendage exclusion.

OBJECTIVE: The left atrial appendage is a frequent source of thromboemboli in patients with atrial fibrillation. Exclusion or excision of the left atrial appendage may reduce the risk of stroke in patients with atrial fibrillation. We evaluated the ability of a novel device to exclude the left atrial appendage during early and intermediate follow-up periods in a canine model. METHODS: Eight mongrel dogs (mean weight 29.1 +/- 4.0 kg) were used in this study. The occlusion device, constructed from 2 stainless steel strips covered with a knit braided polyester fabric, was implanted at the base of the left atrial appendage through a left thoracotomy on a beating heart. Dogs were evaluated at 7 days (n = 2), 30 days (n = 2), and 90 days (n = 4) by epicardial echocardiography, left atrial angiography, histologic inspection, and gross pathology. RESULTS: Device implantation was performed without complications in all animals. Complete exclusion of the left atrial appendage from the circulation was confirmed acutely and chronically by echocardiographic and angiographic evaluations. There was no device migration or damage to adjacent structures. CONCLUSION: This novel device enables rapid, reliable, and safe exclusion of the left atrial appendage. The device provides a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation.

Animals↗

PubMed2004

Dual left anterior descending coronary artery: report of a case.

We report a case of Type I dual left anterior descending artery (LAD) successfully treated by coronary artery bypass grafting including the long LAD. This rare coronary artery anomaly is of clinical importance in the field of myocardial revascularization.

Angina Pectoris↗

PubMed2004

Endothelial integrity of ultrasonically skeletonized internal thoracic artery: morphological analysis with scanning electron microscopy.

OBJECTIVE: The skeletonized internal thoracic artery (ITA) has several advantages over a pedicled one in coronary artery bypass grafting (CABG). An ultrasonic scalpel makes ITA skeletonization easy and speedy, however, the ultrasonic energy that is transmitted to the artery itself can occasionally injure the endothelium. Therefore, the endothelial integrity of the ultrasonically skeletonized ITA is a major concern related to this technique. The purpose of this study is to assess the endothelial integrity of the ultrasonically skeletonized ITA. METHODS: We skeletonized the left ITA with an ultrasonic scalpel in nine patients who underwent CABG, and thereafter the terminal portion of this artery was subjected to a morphological study. The endothelial integrity of this artery was morphologically assessed using scanning electron microscopy, and the results were compared to that of the left ITA skeletonized with fine scissors. RESULTS: All ITA specimens showed a completely confluent endothelium, and no endothelial injury was observed by the scanning electron microscopic study. CONCLUSIONS: The skeletonization of the ITA with an ultrasonic scalpel had no deleterious effect on the endothelium. This morphological study confirmed the safety and the reliability of this technique, and we therefore recommend its clinical use in the skeletonization of the ITA for CABG.

Endothelium, Vascular↗

PubMed2003

Passing the right internal thoracic artery through the transverse sinus.

We describe a simple reliable method to pass the right internal thoracic artery safely through the transverse sinus. At first, a 4-mm-wide vascular tape is passed through the transverse sinus. The cut end of the right internal thoracic artery is then attached to the right end of the tape with a hemoclip. Pulling the left end of the tape leftwards can ensure the passage of the right internal thoracic artery without any risk of twisting.

Humans↗

PubMed2003

Left ventricular myxoma originating from the papillary muscle.

A rare case of left ventricular myxoma presenting embolization into the brachial artery is reported. The sessile tumor originated from the posteromedial papillary muscle and involved the chorda supporting the posterior mitral leaflet. Complete excision of the tumor with the posterior head of the posteromedial papillary muscle, with the chorda and with the posterior mitral leaflet necessitated valve replacement. The tumor was well visualized by the superior-septal and transaortic approaches. These enabled exploration of all four cardiac chambers so as not to overlook any multifocal myxoma. The left ventricular myxoma should be completely resected with the surrounding endocardium in order to avoid recurrence of the disease.

Cardiomyopathies↗

PubMed2002

Coronary artery bypass grafting to a calcified right coronary artery.

A severely calcified coronary artery demands a special technique in coronary artery bypass surgery. We have successfully developed a "punch-out" technique for a calcified right coronary artery in a dialysis patient. After an incision into the target coronary artery, the calcified arterial wall was resected using a punch to make an oval hole for anastomosis. Limited endarterectomy, which consisted of dissection and removal of the calcified endothelium and media around this hole, preserving the adventitia, enabled the anastomosis. This technique can be used for a severely calcified coronary artery that is unamendable to conventional coronary artery bypass grafting.

Calcinosis↗