Dobutamine stress echocardiography has become a diagnostic tool for the evaluation of coronary artery disease and the detection of myocardial viability. In the diagnosis of significant coronary artery disease, it provides similar accuracy to exercise stress thallium-201 myocardial perfusion scintigraphy. Dobutamine stress echocardiography is also a promising modality for predicting the recovery of hibernating myocardium from contractile dysfunction after coronary angioplasty or bypass surgery. This article, reviews our recent clinical experience with the detection of coronary artery disease and viable myocardium by dobutamine stress echocardiography

抄録全体を表示

Duchenne's progressive muscular dystrophy (DMD) is a genetic muscle disorder that causes degeneration and atrophy of the systemic and cardiac muscle. The disease is manifested early in childhood, and most of patients die by age 20 years of respiratory failure or heart failure. The cardiac involvement in DMD is characterized pathologically by degeneration and fibrosis of the myocardium, centering around the posterolateral wall of the left ventricle. Functionally, an abnormal electrocardiogram, valve motion, wall thickness, and wall motion are observed. Furthermore, abnormalities in plasma levels of atrial natriuretic peptide and autonomic function are also demonstrated.
In this review, the cardiac involvements in DMD in the following aspects are described: 1) Electrocardiogram; a) high-frequency notches on the QRS complexes, b) amplitude of QRS complexes, c) late potential, d) arrhythmias, e) heart rate variability, f) a 10-year follow-up study, 2) Echocardiographic findings, 3) Hemodynamic findings, 4) Atrial natriuretic peptide.

抄録全体を表示

The long-term (average: 10 years) outcome in 220 patients with doublevessel disease (DVD) treated medically was investigated. The patients underwent coronary angiography between September 1973 and February 1984, and significant (75% or more) stenosis was detected in each of two major coronary arteries. These patients showed relatively good 5-year and 10-year survival rates of 94.5% and 87.4%, respectively. Cardiac death occurred in 31 patients (14.1%) and nonfatal myocardial infarction (MI) developed in 16 patients (7.3%) during follow-up. When these were defined as cardiac events, the annual attrition rate was 3.1%. A comparison of the outcome with regard to the presence or absence of MI revealed worse results for the MI group, but no difference was observed between different sites of infarction. There was also no difference in outcome with regard to the presence or absence of lesions in the left anterior descending artery (LAD). In the MI group, patients with impaired left ventricular function (ejection fraction≤40%) had inferior survival to those with good left ventricular function. Thus, DVD associated with good left ven-tricular function had a relatively good outcome when treated medically, while patients with impaired left ventricular function might benefit from revascularization.

抄録全体を表示

The immediate and long-term patency of intermediate size side branches was assessed by serial coronary angiography in 47 patients with 48 lesions to determine whether the presence of these side branches (1-2mm in diameter) is unsuitable for Palmaz-Schatz stent implantation. Coronary angiography was performed at baseline, after conventional balloon angioplasty, immediately after stent implantation, at 1 week, and at 6-month follow-up. Sixty-eight lesion-associated side branches that were 1-2mm in diameter, 11 with branch ostial stenosis (Group A) and 57 without ostial stenosis (Group B) were studied. After stent implantation, 9 (13%) branches became totally occluded and coronary flow deteriorated in 13 branches (19%). The incidence of side branch occlusion during the procedure in group A was greater than in group B (55% vs. 12%; p<0.005). One (2%) patient suffered persistent chest pain, but no procedure was complicated by Q-wave myocardial infarction or significant elevation of creatine kinase concentration. Flow improved in 82% of the occluded side branches after 1 week and in 90% after 6 months. These results suggest that the presence of intermediate size side branches is not a contra-indication to Palmaz-Schatz stent implantation.

抄録全体を表示

Transesophageal echocardiography (TEE) is more sensitive than transthoracic echocardiography (TTE) in detecting the potential source of emboli in cardioembolic strokes (CES). To establish the prevalence of a potential cardiac source of embolism detectable on TEE and its relationship to vascular risk factors, an unselected ischemic stroke population was evaluated. Twenty-six age and sex-matched cases with normal cardiological and neurological examinations as well as normal CT-scans, TTE and ECGs were included in the study as the control group.
One hundred and eight patients with cardioembolic stroke (53 patients), atherothrombotic stroke (36 patients), and lacunar stroke (19 patients) were investigated by TTE and TEE. Seven of the 26 (26.9%) controls had thoracic atherosclerotic plaques on TEE examinations. The prevalence of abnormal TEE findings in patients was higher compared to the controls (p<0.001). TEE revealed more specific findings in every etiological group when compared to TTE (74.0% vs 10.2%, p<0.001). Atrial fibrillation correlated with the abnormalities of TEE (p<0.05) while other risk factors did not.
Left atrial spontaneous echo contrast was the most common finding on TEE of cases with cardioembolic stroke while atherosclerotic aortic plaques were mostly encountered in patients with atherothrombotic stroke. No specific findings by TEE were seen in patients with lacunar stroke.
TEE is capable of detecting definite etiologies in cardioembolic stroke and associated cardiac pathologies in atherothrombotic stroke and lacunar stroke. These observations suggest that TEE is a useful tool to guide the physician for the treatment of ischemic stroke patients.

抄録全体を表示

Exercise-induced downsloping ST-segment depression is a common manifestation of severe myocardial ischemia. Although greater downsloping ST-segment depression is suspected to indicate more severe ischemia, its exact relationship to regional myocardial blood flow (RMBF) has not yet been clarified. We investigated the relationship between the magnitude of downsloping ST-segment depression and exercise-induced changes in RMBF and collateral perfusion. Nitrogen-13 ammonia positron emission tomography was performed in 6 healthy volunteers and 72 patients with angiographically proven coronary artery disease. The left ventricle was divided into 11 regions of interest, and RMBF in each region was measured at rest and during low-level supine bicycle exercise. Downsloping ST-segment depression of 0.1mV or more at 80 milliseconds after the J point was accepted as significant. Low-level exercise induced downsloping depression of 0.1 to 0.2mV in 10 patients (group D₁) and downsloping depression of 0.2mV or more in 8 patients (group D₂). Multivessel disease was common in both group D₁ (80% of patients) and group D₂ (88% of patients). Collateral circulation was significantly more frequent in group D₁ (90%) than in group D₂ (13%, p<0.01). Ischemic areas were larger and cardiac function was worse in group D₂ than in group D₁. The RMBF increased Buffciently in all regions (56±30%) with exercise in the healthy group. In group D₁, RMBF was unchanged or decreased in ischemic areas (10±23%) but increased sufficiendy in sumounding areas (50±32%). In group D₂, RMBF was unchanged in ischemic areas (17±24%) and increased insufficiently in surrounding areas (41±21%). Therefore, exercise-induced downsloping ST-segment depression of 0.1 to 0.2mV may reflect an underlying change in blood flow in viable myocardium with collateral perfusion, and downsloping depression of 0.2mV or more may reflect more severely impaired myocardium without collateral perfusion.

抄録全体を表示

QT dispersion (QTd: maximum QT interval-minimum QT interval) is associated with severe cardiac arrhythmia and with abnormal ventricular repolarization. We investigated the influence of exercise on QTd in patients with ischemic heart disease. On standard 12-lead electrocardiograms, QTd was measured before and after treadmill exercise in 7 normal subjects, 17 patients with effort angina pectoris (and_??_75% stenosis on coronary arteriography), and 33 patients with old myocardial infarction. Bazett's formula was used to obtain the corrected QTd (QTcd). The pre-exercise resting QTcd was 45.9±10.6, 44.3±15.2, and 74.8±28.1msec in the respective groups, being significantly greater in the infarct group (p<0.05). The QTcd at 5min after exercise was respectively 49.3±9.0, 58.8±19.9, and 75.4±30.9msec (p=0.0347, infarct vs. controls). The difference in QTcd was significant for the angina group before and after physical exercise (p=0.0003). There was a significant increase of QTcd after exercise in the angina group whether or not the patients were receiving β-blockers. The infarct patients without β-blocker therapy showed an increase of QTcd after exercise, while those receiving β-blockers showed a decrease. The past-exercise difference between these subgroups was significant (p=0.0351). Conclusions: QTcd was significandy increased by exercise in the angina group, possibly reflecting impaired repolarization due to ischemia. Inhibition of the increase in QTd by β-blockers suggested a possible preventive effect on severe arrhythmias due to nonhomogeneous ventricular repolarization.

抄録全体を表示

Insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been postulated as a risk factor for coronary heart disease. We conducted a case-control study of 271 Chinese, including 114 subjects with coronary artery disease (CAD), 42 with non-CAD and 115 apparently normal controls to examine the association of I/D polymorphism and CAD. The genotypes were identified by polymerase chain reaction and the plasma ACE activity was assayed by spectrophotometry. The allele and genotype frequencies were not different among the CAD, non-CAD and apparently normal groups (p=0.42 and 0.63). Plasma ACE activity was not different among the three groups (p=0.32). The D-allele and DD genotype were not more prevalent in subjects with low risk CAD (p=0.07 and 0.16) and subjects with myocardial infarction (p=0.79 and p=0.35). No association was found between I/D polymorphism and severity of CAD (p=0.42 and 0.70). In conclusion, the deletion polymorphism of the ACE gene may not be an independent risk factor in the development of CAD or myocardial infarction in this Chinese population. The unique or synergistic effect of other genes needs further study.

抄録全体を表示

Experimental studies have shown the limitation by calcium antagonists of the propensity to fibrillation secondary to the occlusion of a large coronary artery. However, this capacity, studied in the acute phase of infarction, is less obvious and still under debate. Ischemia was therefore produced in anesthetized, open-chest pigs by complete occlusion of the left anterior descending coronary artery according to two modes, either near its origin during brief but increasing periods (30, 60, 120, 180s, etc) or half-way from this origin for a much longer time (60min). The time course of vulnerability to fibrillation was monitored by ventricular fibrillation threshold (VFT), measured by trains of diastolic stimuli of 100ms. Verapamil was administered in a 50μg/kg dose followed by 2μg/kg/min infusion. 1) In the case of brief proximal occlusions under pacing at a constant high rate (180 beats/min), verapamil slowed the decline of VFT from 6-8mA to nearly 0mA. VFT was 4.4±0.4mA after 60s ischemia, whereas it had already fallen to 1.8±0.3mA (p<0.001) in the absence of the drug. Accordingly, the onset of spontaneous fibrillation which depends on the decrease in VFT to about 0mA was prolonged from 2-3 to 6-9min. Bradycardia, concurrently produced by verapamil, is a factor which enhances these alterations.2) In the case of a persistent midportion occlusion of the artery under sinus rate, fibrillations were similarly delayed by verapamil from 14-25 to 23-49min after occlusion, but they were more numerous. VET was lowered to critical values later, but also for a longer time. The period propitious to fibrillation was prolonged because the return of VFT to higher values reflecting hypoexcitabihty subsequent to the first cell injury was substantially delayed. Consequently, calcium antagonists should often prevent ventricular fibrillation when transient ischemia disappears before VFT falls to the vicinity of 0mA. In contrast, a real benefit could not be expected from these drugs when ischemia is persistent since they then only delay fibrillations, the number of which is increased.

抄録全体を表示

Ventriculo-arterial coupling is expressed as the ratio E_max/e_am (maximum ventricular elastance/arterial elastance). Different areas under the end-systolic pressure-volume relation (ESPVR) are expressed in terms of E_max/e_am. The explicit inclusion of the active force of the myocardium in the mathematical formalism describing the pressure-volume relation (PVR) leads to new insight into the mechanics of left ventricular contraction. Applications to experimental data related to stroke work area SW under ESPVR are discussed and provide further evidence for the consistency of the mathematical formalism used.

抄録全体を表示

This study investigated the effect of chronic digitalis glycoside use on β-adrenergic sympathetic activities in heart failure. Twenty-two Japanese white rabbits were anesthetized by intravenous injection of chloral hydrate. Aortic regurgitation (AR) was produced by perforating aortic valves in 14 rabbits. Digoxin was given for 1 week to 7 rabbits with AR (AR+Dig) and saline to 7 rabbits with AR (AR+C). Sham operation was performed in the remaining 8 rabbits (S). The left ventricular end-diastolic pressure was higher in AR+C than S (p<0.05). It was lower in AR+Dig than AR+C (p<0.05). Cardiac output was lower in AR+C than S (p<0.05). There was no difference between AR+Dig and S. Both the left ventricular end-diastolic and end-systolic diameters were larger in AR+C (p<0.05) than S, but they were similar between AR+Dig and S. Plasma norepinephrine level was lower in AR+Dig than AR+C. Myocardial β-adrenergic receptors number determined by radioligand binding assay using 30-800pM ¹²⁵I-iodocyanopindolol was lower in AR+C than S (28.8±7.9 vs. 69.9±12.3fmol/mg protein, p<0.05). It was higher in AR+Dig (39.9±9.8) than AR+C (p<0.05). Myocardial norepinephrine content was lower in both AR+C (p<0.05) and AR+Dig than S (p<0.05). Thus, digitalis glycosides exert favorable effects on β-adrenergic sympathetic activities in addition to the effects on hemodynamic variables in this animal model of heart failure.

抄録全体を表示

We examined the relative expression of laminin α1, α2, α4 and β1 chain genes in the heart of embryonic, neonatal and adult BALb/c mice. The reverse transcriptase-polymerase chain reaction was employed to determine the mRNA expression of these chains because of the relatively small amount of RNA extracted from rat embryonic hearts. Glyceraldehyde 3-phosphate dehydrogenase and β-actin were used as internal controls. Among the hearts examfined, a relatively high expression of laminin α1 chain was observed in the embryonic hearts, while its expression was very weak in the neonatal and negligible in the adult hearts. Conversely, expression of laminin α2 chain was virtually not observed in the embryonic hearts, but this chain was expressed weakly in the neonatal and substantially in the adult hearts. Similar to laminin α1, laminin α4 was expressed in the embryonic hearts, while its expression was relatively weak in the neonatal and adult hearts. Laminin β1 was expressed in the hearts of mice at all stages examined. These results demonstrate that the laminin chain gene expression changes in the different developmental stages of the hearts of BALb/c mice.

抄録全体を表示

We performed a total repair for a 1-year-old boy with left isomerism, a common atrium, incomplete atrioventricular septal defect and hemiazygos continuation. The operation performed was intraatrial rerouting with a baffle and mitral repair. The postoperative course was uneventful.
However, two and a half years after the total repair, the patient revealed obstruction of the systemic atrium constructed by the baffle and the left ventricular outflow tract. Reoperation to relieve these obstructions was successful.

抄録全体を表示