Hiroo Shikata

Simple left atrial procedure for chronic atrial fibrillation associated with mitral valve disease

BACKGROUND A computerized 48-channel mapping system was used to investigate the characteristics of an atrial epicardial electrogram during chronic atrial fibrillation (AF) in patients with solitary mitral valve disease. We have devised a simple left atrial procedure to eliminate the chronic AF during a mitral valve operation. METHODS Using this mapping system, we performed intraoperative atrial mapping in 11 patients with chronic AF associated with mitral valve disease. The AF duration ranged from 0.4 to 15 years (mean, 8.0 +/- 4.5 years). A simple surgical ablation of the AF on the left atrium only was performed during the mitral valve operations. RESULTS The mean AF cycle length of the atria ranged from 129 to 169 milliseconds in the right atrium and from 114 to 139 milliseconds in the left atrium. The mean AF cycle length of the left atrium was shorter than that of the right atrium. Regular and repetitive activation was found in the left atria of 7 of 11 patients. The AF disappeared in all patients immediately after the operation, and 10 of these patients continued to have a sinus rhythm postoperatively (AF-free rate, 91%). CONCLUSIONS Computerized intraoperative mapping revealed a shorter mean AF cycle length in the left atrium. A simple left atrial procedure was effective in eliminating chronic AF associated with solitary mitral valve disease.

Characterization of amino-acid transport systems in guinea-pig intestinal brush-border membrane

The amino-acid transport systems have been characterized in brush-border membrane vesicles prepared from guinea-pig small intestine. Uptake of all amino acids tested was measured at the initial velocity for 5 s. L-Proline, alpha-(methylamino)isobutyrate, glycine, L-alanine and L-methionine were transported dependent solely on an Na+ gradient from the outside to the inside of the vesicles, and L-cysteine, L-phenylalanine and L-leucine were transported dependent largely on the Na+ gradient with a small fraction of Na+-independent transport. The transport of L-aspartic acid and L-lysine was independent of the Na+ gradient and L-lysine transport was somewhat inhibited by the presence of cations, including Na+, K+ and Li+. A cross-inhibition study of the uptake of these amino acids in the brush border of guinea-pig intestine revealed the presence of at least three Na+-dependent and three Na+-independent carrier-mediated systems. One Na+-dependent system interacted mainly with imino acid. Another Na+-dependent system interacted with neutral amino acids, while a third system was selective for glycine. One Na+-independent system is for acidic amino acids, another is responsible for neutral amino acids and a third for cationic amino acids. These transport systems of amino acids in guinea-pig small intestine are compared with those in rabbit and mouse intestine.

Pooled air in open heart operations examined by transesophageal echocardiography

BACKGROUND The clinical significance of pooled air detected by transesophageal echocardiography during open heart operations is not clear. METHODS Thirty-eight consecutive patients undergoing an open heart operation or an operation on the ascending aorta were divided into two groups on the basis of the absence (group 1, n = 14) or presence (group 2, n = 24) of pooled air. They were examined for intramyocardial echo contrast, ST segment elevation, conduction disturbances, and regional wall motion abnormalities. RESULTS Echo contrast was found in no patient in group 1 and 66.7% of group 2 patients (p < 0.001). New regional wall motion abnormalities were detected in no patient in group 1 versus 33.3% of group 2 patients (p < 0.05), and ST segment elevation was seen in 33.3% of group 2 patients versus no group 1 patients (p < 0.05). Intramyocardial cardial echo contrast was newly detected after the appearance of pooled air more frequently in patients with ST segment elevation (p < 0.001). Atrioventricular block and sinus arrest appeared in 3 patients and 2 patients, respectively. Postoperative regional wall motion abnormalities were found in 25.0% of patients and were not closely related to intraoperative echo contrast findings. CONCLUSIONS Pooled air, which is often detected in open heart operation by means of transesophageal echocardiography, is related to several cardiac events, including ST segment elevation, conduction disturbances, and regional wall motion abnormalities, although most of these are transient.

Selective intercostal arterial perfusion during thoracoabdominal aortic aneurysm surgery

BACKGROUND This clinical study evaluated changes in motor evoked potentials (MEP) elicited by direct cerebral cortical stimulation and evoked spinal cord potentials (ESCPs) elicited by direct spinal cord stimulation during selective intercostal arterial perfusion for thoracoabdominal aortic aneurysm (TAAA) repair. We also determined the efficacy of this perfusion method for prevention of paraplegia. METHODS Two kinds of ESCPs and MEPs were monitored during the prosthetic replacement step for TAAA surgeries. We performed selective intercostal arterial perfusion from the T7 intercostal artery to the L1 intercostal artery through a small piece of Dacron graft while monitoring spinal cord potentials in five cases of TAAA. RESULTS The MEP amplitude decreased after clamping the aorta but quickly recovered after selective perfusion of intercostal arteries. Other spinal cord potentials did not change during the reconstruction of intercostal arteries. Postoperative paraplegia or parapalesis did not occur in any of the patients. CONCLUSIONS Monitoring of MEPs during selective intercostal arterial perfusion was a useful adjunct to prevent postoperative paraplegia in TAAA surgery.

Clinical Implication of Orbital Ultrasound Monitoring During Selective Cerebral Perfusion

BACKGROUND We evaluated clinical relevance of orbital ultrasound (OUS) monitoring to neurological events in aortic surgery associated with selective cerebral perfusion (SCP). METHODS In 24 consecutive cases, blood flow was monitored at central retinal artery (CRA) and retrobulbar vessels. The threshold perfusion pressure for detecting CRA flow in the color Doppler mode (BPt) was determined in individual eyes. RESULTS The BPt ranged from 25 to 71 mm Hg. Events (infarction, anisocoria, delirium) occurred in 8 cases. Infarction occurred in all 3 cases when retrobulbar flow was severely impaired for 40 minutes or longer, while none of the remaining 21 cases had infarction (p = 0.0005). Among the latter cases, perfusion pressure was below BPt for longer than 100 minutes in all 5 cases with events, and in 5 of 16 cases without events (p = 0.0124). No significant difference was found in age, duration of cardiopulmonary bypass, SCP, and circulatory arrest, and duration of blood pressure below 50 mm Hg. CONCLUSIONS Sustained hypoperfusion detected with OUS monitoring is related to an occurrence of neurological events.

Neurotensin receptors on the rat liver plasma membranes

Neurotensin (NT) is now classified as a brain-gut peptide in the central nervous system and gastrointestinal tract. In the present study, we characterized the NT receptors on the rat liver plasma membranes. The specific binding of [3H]NT was time dependent, reversible, and saturable. Scatchard analysis of the specific binding data yielded two classes of binding sites, a high affinity site and a low affinity site. The average maximum number of binding sites (Bmax) amounted to 13.3 +/- 1.1 fmol/mg protein at high affinity site and 122.3 +/- 21.5 fmol/mg protein at low affinity site, respectively. The dissociation constant (Kd) had values of 0.39 +/- 0.01 nM at high affinity site and 8.1 +/- 1.1 nM at low affinity site, respectively. The amount of specifically bound [3H]NT was significantly reduced in the presence of mono and divalent cations, EDTA, EGTA and a peptidase inhibitor bacitracin, NT1-13 competed with [3H]NT for its binding site with an IC50 of 0.19 nM at high affinity site (0.2 nM concentration of [3H]NT) and 0.7 nM at low affinity site (4.0 nM concentration of [3H]NT). Xenopsin, a NT analogue separated from the skin of Xenopus laevis, was equipotent (IC50 0.75 nM) with NT1-13 at 4.0 nM concentration of [3H]NT. C-terminal sequence of NT contains the structure necessary for interaction with NT binding sites whereas N-terminal sequence had no binding activity. Since NT has a hyperglysemic and a hypercholesterolemic effects in rats, these NT receptors on the rat liver plasma membranes may be involved in the hyperglycemia and/or hypercholesteroremia induced by NT.

Evaluation of motor- and sensory-evoked potentials for spinal cord monitoring during thoracoabdominal aortic aneurysm surgery

OBJECTIVE To assess the utility of spinal cord monitorings for prediction of spinal cord ischemia, we investigated the role of both motor evoked potentials and sensory evoked potentials during thoracoabdominal aortic aneurysm surgeries. METHODS We monitored two kinds of sensory evoked potentials; descending evoked spinal cord potentials from the lumbar enlargement after cervical spinal cord stimulation and segmental evoked spinal cord potentials at the lumbar enlargement elicited by peroneal nerve stimulation, and motor evoked potentials from the lumbar enlargement elicited by direct subcranial stimulation in 9 thoracoabdomonal aortic aneurysm surgeries. RESULTS Postoperative paraplegia occurred in one case in which the patients died during the perioperative period. One case showed transient paraparesis, but recovered following rehabilitatation. These cases showed a decrease in the amplitude of descending evoked spinal cord potentials and motor evoked potentials. CONCLUSION The recovery of the amplitude of the motor evoked potentials and the descending evoked spinal cord potentials after declamping correlated with the neurologic outcome.

A modified maze procedure performed only on the left atrium for chronic atrial fibrillation associated with mitral valve disease: report of a case.

We describe herein the successful treatment of a patient with chronic atrial fibrillation (AF) associated with mitral valve stenosis and regurgitation, achieved by performing a modified maze procedure on the left atrium alone. The patient was a 51-year-old man who had suffered from intractable AF for 17 years, causing multiple cerebral emboli and palpitations. He had undergone open mitral commissurotomy and balloon commissurotomy 15 and 7 years ago, respectively. On admission, an echocardiogram revealed mitral valve restenosis and thrombosis in the left atrial appendage. Prosthetic valvular replacement was performed following isolation of all pulmonary veins with cryoablation to the posterior wall of the left atrium and excision of the left atrial appendage. Postoperatively, the AF disappeared and echocardiogram demonstrated a left atrial kick in the mitral valvular inflow without any evidence of thrombosis in the left atrium. Thus, we believe that our modified “left side only” maze procedure is a simple and efficient method for the treatment of chronic AF with mitral valve disease.

Identification of creatine as a cofactor of thiamin-diphosphate kinase

Thiamin‐diphosphate (TDP) kinase which catalyzes thiamin triphosphate formation from TDP requires a low‐molecular‐mass cofactor in addition to ATP and Mg2+. The cofactor was isolated in a crystalline form from pig skeletal muscle and identified as creatine by proton NMR, mass spectrometry, infrared spectrometry and elemental analysis. The isolated cofactor and authentic creatine supported the same activity of partially purified TDP kinase at identical molar concentrations. Neither creatine phosphate nor creatinine showed activity as a cofactor. This is the first report showing evidence of the existence of a creatine‐dependent enzyme.

Surgical repair of Wolff-Parkinson-White syndrome complicated with myocardial bridging

Myocardial bridging causes myocardial ischemia during supraventricular tachycardia. We present a case of Wolff-Parkinson-White syndrome combined with myocardial bridging. The patient complained of angina pectoris during paroxysmal supraventricular tachycardia because of severe constriction of the left anterior descending coronary artery during systole. A myocardial scintigram revealed myocardial ischemia in the anteroseptal wall during paroxysmal supraventricular tachycardia. Myotomy to prevent myocardial bridging and interruption of the accessory conduction pathway was successfully accomplished in a one-stage operation.