Hironori Hirai

Widening of the Excitable Gap and Enlargement of the Core of Reentry During Atrial Fibrillation With a Pure Sodium Channel Blocker in Canine Atria

Background—This study aimed to assess the effects of pilsicainide, a pure sodium channel blocker, on electrophysiological action and wavefront dynamics during atrial fibrillation (AF). Methods and Results—In a newly developed model of isolated, perfused, and superfused canine atria (n=12), the right and left endocardia were mapped simultaneously by use of a computerized mapping system. AF was induced with 1 to 5 &mgr;mol/L acetylcholine. The antifibrillatory actions of pilsicainide on AF cycle length (AFCL), refractory period (RP), conduction velocity (CV), excitable gap (EG), and the core of the mother rotor were studied. The RP was defined as the shortest coupling interval that could capture the fibrillating atrium. The EG was estimated as the difference between the AFCL and RP. At baseline, multiple wavefronts were observed. After 2.5 &mgr;g/mL infusion of pilsicainide, all preparations showed irregular activity, and AF was terminated in 2 preparations. The AFCL and RP were prolonged, and CV was decreased significantly. The EG was widened (147%;P <0.01), and the core perimeter was increased (100%;P <0.01). Increasing the dosage either terminated AF (6 preparations) or converted to organized activity (ie, atypical atrial flutter) (4 preparations). On the maps, all “unorganized” AFs were terminated with the excitation of the core of the mother rotor by an outside wavefront, whereas in preparations with atrial flutter, pilsicainide did not terminate its activity. Conclusions—Widening of the EG by pilsicainide facilitates the excitation of the core of the mother rotor, leading to the termination of AF. In some experiments, pilsicainide converts AF to persistent atrial flutter.

Percutaneous bare Z-stent implantation as an alternative to surgery for acute aortic dissection with visceral ischemia

We describe a case of Stanford type B acute aortic dissection causing visceral ischemia. An aortogram showed an hourglass‐like narrowing of the true lumen at the diaphragm with a 60 mm Hg pressure gradient. Placement of a self‐expanding metallic Z‐stent under intravascular ultrasound guidance restored blood flow to the viscera. Cathet Cardiovasc Intervent 2003;58:95–100.

Evaluation of left ventricular diastolic function using color kinesis

PurposeColor kinesis (CK) is a real-time echocardiographic technique based on acoustic quantification that yields regional and global information by tracking and color-encoding endocardial motion. The aim of this study was to determine the feasibility and usefulness of diastolic CK images with ICK software to objectively assess global and regional left ventricular (LV) diastolic function. Accordingly, diastolic properties obtained from CK images were compared with conventional Doppler echocardiographic indices.MethodsWe studied 56 subjects who underwent echocardiographic evaluation in our laboratory for assessment of cardiac structure and function. Criteria for inclusion included the presence of normal sinus rhythm and adequate two-dimensional echocardiographic imaging. Exclusion criteria were (1) all types of arrhythmias, (2) pericardial effusion, (3) heart rates <55 or >90 beats/min, (4) abnormal interventricular septal motion caused by right ventricular pressure or volume overload, (5) moderate to severe mitral or aortic regurgitation, and (6) mitral valve stenosis. Using pulsed Doppler echocardiography, peak velocities during rapid filling (E) and atrial contraction (A) were measured, and the E/A ratio and deceleration time of the E wave velocity (DT) were calculated. The time-velocity integral (TVI) of the E wave (TVI-R), A wave (TVI-A), and rapid-filling fraction (TVI-R/TVI-R+TVI-A) was measured. The early diastolic mitral annular velocity (Ea) was measured by tissue Doppler. The 56 subjects were divided into the following three groups: (1) an impaired relaxation group consisting of 30 patients with normal ejection fraction and a mitral inflow pattern with a reduced E/A ratio (E/A < 1.0); (2) a pseudonormal group consisting of 18 patients with a mitral inflow pattern with an increased E/A ratio (E/A > 1.0), an increased E/Ea ratio (E/Ea 10), and no shortened DT (≧140 ms) [patients with hypertrophic cardiomyopathy (HCM, n = 8), dilated cardiomyopathy (DCM, n = 8), and aortic valve stenosis (n = 2) were included in this group); and (3) a restrictive group consisting of eight patients with a mitral inflow pattern with an increased E/A ratio (E/A >1.5), an increased E/Ea ratio (E/Ea ≧10), and a shortened DT (<140 ms) [patients with DCM (n = 5) and HCM (n = 3) were included in this group]. As a control group, 20 normal subjects (30 ± 18 years) were selected on the basis of having high-quality echocardiographic images. Diastolic CK images were obtained from the LV midpapillary short-axis view. The analysis of CK diastolic images was performed by using ICK software. The CK-diastolic index (CK-DI) was defined as the degree of LV segmental expansion during the first 30% of diastole, expressed as a percentage. The mean CK-DI was calculated from the average CK-DI of six LV segments.ResultsNo relationship was observed between mean CK-DI and rapid-filling fraction in any of the study subjects (r = −0.092, P > 0.2). Mean CK-DI was significantly lower in the restrictive group (34.2% ± 4.3%) compared with the normal group (70.6% ± 7.4%), the impaired relaxation group (50.5% ± 7.7%), and the pseudonormal group (42.3% ± 7.5%). The reduction of mean CK-DI was found to be associated with the progression of LV diastolic dysfunction.ConclusionWe conclude that the analysis of diastolic CK by using ICK software is a useful technique that can be applied to quantitative evaluation of LV global diastolic function.

Relationship between spontaneous echo contrast in the thoracic aorta and plasma von Willebrand factor

PurposeTo clarify the relationships between spontaneous echo contrast (SEC) detected by transesophageal echocardiography (TEE) and coagulopathy, ultrasonographic findings that may correlate to biochemical coagulation markers were examined.MethodsTEE was performed on 49 consecutive patients (mean age 64 ± 14 years; 28 men, 21 women). Blood samples were taken at the same time as TEE was carried out. Aortic SEC (Ao-SEC) and left atrial SEC (LA-SEC) were classified into three grades: absent, mild and marked. Levels of von Willebrand factor (vWF), thrombin antithrombin III complex (TAT), prothrombin fragments 1+2 (F1+2) and fibrinopeptide A (FPA) were measured.ResultsMean plasma vWF levels by Ao-SEC grade were 144 ± 39% for absent, 177 ± 55% for mild and 210 ± 73% for marked, with significantly higher levels in the Ao-SEC marked group than in the Ao-SEC absent group (P < 0.05). Mean plasma vWF levels by LA-SEC were 185 ± 73% for absent, 180 ± 49% for mild and 201 ± 62% for marked, with no significant differences apparent between groups. Moreover, no relationships were identified between Ao-SEC grade and plasma levels of coagulation indicators TAT, F1+2 and FPA.ConclusionPlasma vWF levels correlated to grade of aortic SEC. Characteristics of the coagulation system differ between Ao-SEC and LA-SEC. Ao-SEC offers a clinical indicator of platelet thrombus formation.

A case of chronic dissecting aortic aneurysm complicated with rupture into the right atrium: Diagnosis by transesophageal echocardiography

Although rupture of a dissecting aortic aneurysm into the pericardial sac, pleural cavities, or mediastinum is a frequently encountered complication of this entity, rupture into a right-sided cardiac chamber is extremely rare. An 80-year-old woman was admitted to this institution because of dyspnea and facial edema. One year before admission, a diagnosis of dissecting aortic aneurysm (Stanford A type) was made based on results of magnetic resonance imaging and transesophageal echocardiography (TEE); however, the patient and her family refused surgical therapy. On admission, blood pressure was 120/60 mmHg, and a Levine 3/6° continuous murmur was audible at the third and fourth intercostal spaces of the right sternal border. Chest x-ray film showed moderate cardiomegaly, congested lung fields, and bilateral pleural effusion. A two-dimensional echocardiogram revealed severe aortic root dilatation 80 mm in diameter with the intimal flap. Color flow Doppler imaging demonstrated abnormal flow toward the back space in dilated ascending aorta. Continuous wave Doppler imaging showed the peak velocity of this flow to be 4.8 m/s. This high-velocity flow strongly suggested that the dissecting aortic aneurysm had ruptured into the right-sided cardiac chamber, and shunt flow from the false lumen of the aortic aneurysm into the right atrium was directly visualized by TEE. Our diagnosis, based on these findings, was chronic dissecting aortic aneurysm with communication into the right atrium. In view of the patient’s deteriorating clinical condition, cardiac catheterization was not performed before surgery. Surgery revealed an aneurysm of the ascending aorta measuring 90 mm in diameter and multiple fistulas approximately 2 to 3 mm in diameter arising from the false lumen of the aorta into the right atrium at the base of the atrial appendage. The patient underwent successful replacement of the ascending aorta and closure of the aorto-right atrial fistulas. She had an uneventful postoperative course and was discharged 7 weeks after surgery.