Rapid myocardial perfusion imaging with 99Tcm-teboroxime and a three-headed SPECT system: a comparative study with 201Tl.

99Tcm-teboroxime is a new myocardial perfusion agent with a high first pass extraction and rapid myocardial washout. The usefulness of 99Tcm-teboroxime was evaluated for detection of myocardial ischaemia using a three-headed single photon emission tomography (SPECT) system which allows for rapid data acquisition. The subjects consisted of 14 patients, including seven with ischaemic heart disease, four with cardiomyopathy and three others. After the 99Tcm-teboroxime injection, dynamic data was collected every minute for 15 min with continuous rotation. High-quality SPECT images could be obtained by reconstructing the serial scans from 2 to 8 min. The sensitivity, specificity and accuracy of the 99Tcm-teboroxime study for the detection of the ischaemic region were not significantly different from those of the 201Tl study. Myocardial clearance was slow in the ischaemic lesion and in the myocardium of cardiomyopathy patients, while the coronary angiograms did not show any abnormality. These results therefore indicate that the rapid SPECT imaging and myocardial clearance of 99Tcm-teboroxime obtained with a three-headed SPECT system were useful for the detection of myocardial ischaemia.

Relationship of high-density lipoprotein cholesterol and red blood cell filterability: cross-sectional study of healthy subjects.

The deformability of red blood cells (RBCs) is an important rheologic factor in the maintenance of normal blood flow in the microcirculation. Contrary to the well-known relationship between hyperlipidemia and atherosclerosis, the relationship between RBC rheology and the serum lipid profile has remained controversial and obscure. Moreover, the correlation of high-density lipoprotein (HDL)-cholesterol and RBC deformability has not been fully understood. In the present cross-sectional study of 139 apparently healthy subjects, we investigated whole-cell deformability (filterability) of RBCs in relation to the lipid profile, using a nickel mesh filter with 3.2-microm pores. RBC filterability was independent of gender, age and serum levels of low-density lipoprotein (LDL)-cholesterol. The filterability was significantly proportional to the HDL-cholesterol values (r = 0.382, p < 0.01), whereas it was inversely proportional to the triglyceride levels (r = -0.259, p < 0.01). These findings may provide new insight into the role of HDL-cholesterol not only in preventing atherosclerotic progression but also in improving RBC filterability.

[The nature of the external ionic modulation of the myocardial electrical propagation: importance of the safety factor].

The mechanisms of conduction change depending on the extracellular K+ and Ca2+ concentrations ([K+]o and [Ca2+]o, respectively) were investigated. Simultaneous measurements of active and passive membrane properties and net membrane excitability were fulfilled by arranging the intra- and extracellular microelectrodes in a superfused and paced guinea pig papillary muscle. Internal longitudinal resistance (ri), as a parameter of passive property, was evaluated by the intra- and extracellular voltage ratio. The maximum upstroke rate (Vmax) was used as an active property. Apparent threshold potential (Vth) was defined by the breakpoint in the action potential upstroke fitted semilogarithmically. Graded rise in [K+]o (from 2.7 to 15.0 mM) evoked a progressive fall in Vmax, and was associated with less negative resting membrane potential and constant ri. Conduction velocity (theta) was the maximum in 9.0 mM [K+]o ("supernormal" conduction) but not in 2.7 mM [K+]o which gave the greatest Vmax ("subnormal" conduction). Safety factor of conduction (S), as an index of net excitability, could most readily account for the [K+]o-dependent change in theta. This was true also in the case of [Ca2+]o elevation (from 0.9 to 5.4 mM). These results indicate that the cation-modulated propagation is governed by the cable theory including S as a matrix of combined active and passive properties.

Diffuse endocardial thrombus in left ventricle associated with a case of hypereosinophilic syndrome.

A 16-year-old girl appeared with fever and dyspnea. In her peripheral blood, leukocytes were found to have increased up to 25,200/mm3, and eosinophils occupied 49% of the leukocyte population. By echocardiography, an abnormal echo layer which appeared to be thrombus was observed over the entire left ventricular endocardium including the posterior leaflet of the mitral valve, and mild mitral valve regurgitation was noted. After treatment, the abnormal echoes were markedly reduced simultaneously with the improvement of subjective symptoms.

Ability of activation recovery intervals to assess action potential duration during acute no-flow ischemia in the in situ porcine heart. Experimental Cardiology Group, University of North Carolina at Chapel Hill.

INTRODUCTION: The ability to assess transmural changes in action potential duration during acute no-flow ischemia is essential to an understanding of the tachyarrhythmias that occur in this setting. The purpose of this study was to determine if activation recovery intervals determined from unipolar electrograms would provide this information. METHODS AND RESULTS: We recorded simultaneously transmembrane action potentials and unipolar electrograms from sites located as closely together as possible in the center and at the lateral margin of the ischemic zone during acute no-flow ischemia and correlated the changes in activation recovery intervals obtained from the unipolar electrograms to the changes in action potential duration. We found that the activation recovery intervals provided an accurate measure of the changes in action potential duration during acute no-flow ischemia provided the electrograms had a well-defined, single negative component to the QRS complex with a maximum negative dV/dt > 10 V/sec and a single positive component to the T wave having a maximum positive dV/dt > 1.6 V/sec. Electrograms meeting these criteria comprised 90% of the electrograms recorded at the margin of the ischemic zone throughout 60 minutes of no-flow ischemia. In the center of the ischemic zone, 75% of the recorded electrograms met these criteria for the first 20 minutes of no-flow ischemia. Thereafter, the percentage declined and after 40 minutes of no-flow ischemia, none of the electrograms recorded in the center of the ischemic zone met these criteria. CONCLUSION: Activation recovery intervals obtained from unipolar electrograms provide an accurate assessment of changes in action potential duration throughout the ischemic zone during acute no-flow ischemia, provided the characteristics of the electrograms meet specific predetermined criteria.

Increased plasma epinephrine but not reduced heart rate variability leads to ventricular arrhythmias in patients with acute myocardial infarction.

Ventricular arrhythmia observed in the acute stage of myocardial infarction is profoundly related to the autonomic balance. To investigate prediction of ventricular arrhythmia, heart rate variability and plasma catecholamine concentration were simultaneously measured for a week in 17 consecutive patients with first anterior or anteroseptal Q wave infarction treated without specific coronary intervention. The cross-sectional plot of coefficient of variance (= standard deviation of N-N interval/mean N-N interval x 100; %) as a function of plasma epinephrine on the day of admission remained lower than the standard average. Ventricular premature contractions increased in proportion to the plasma epinephrine concentration. In the first week of hospitalization, plasma epinephrine concentration and frequency of premature contraction decreased exponentially, whereas the coefficient of variance showed a modest decline. Ventricular tachycardia refractory to xylocaine with rate accelerating with persistence was observed only in patients with the peak epinephrine concentration > 375 pg/ml. Plasma epinephrine concentration rather than coefficient of variance during sleep after the first acute episode is more closely related to the following triggered ventricular arrhythmia.

Thrombotic obstruction of the right coronary artery in a postoperative patient with Bland-White-Garland syndrome.

A 53-year-old female presented with symptoms of severe chest and back pain associated with oliguria. The patient had a history of exertional dyspnea since the age of 20, and easy fatigability since the age of 27. At the age of 41, she noted marked exacerbation of these symptoms after suffering from a cold and was ultimately diagnosed as having Bland-White-Garland (BWG) syndrome with mitral valve regurgitation. The patient then underwent re-implantation of an anomalous left coronary artery from the pulmonary artery to the posterolateral wall of the aorta. Eleven years later, she re-presented with symptoms of angina and congestive heart failure. Coronary angiography was subsequently performed and a total occlusion of the right coronary artery with probable thrombus was revealed. The right coronary artery was filled via collaterals from the implanted left coronary artery. Mitral regurgitation was noted during angiography. The patient underwent aorto-coronary artery bypass grafting of the right coronary artery and concomitant mitral valve replacement. Her postoperative condition remained excellent.

Coronary dilating effects of intracoronary nicorandil. Comparison with isosorbide dinitrate.

Although nicorandil, N-(2-hydroxyethyl) nicotinamide dinitrate, is a nitrate ester, its cardiovascular action differs from that of nitrate compounds in several aspects. In this quantitative angiographic study, the acute coronary dilating effect of intracoronary nicorandil (0.25, 0.50, 1.0 mg) was compared with that of isosorbide dinitrate (ISDN; 1.0 mg) in 46 patients with or without ischemic heart disease (IHD). Dose-dependent right coronary dilating action was observed by intracoronary administration of nicorandil without any adverse effects. The same degree of right coronary dilation was achieved by the intracoronary application of equivalent doses of ISDN. We conclude that intracoronary administration of nicorandil is beneficial for the supportive treatment of IHD during coronary artery investigation and intervention without the risk of severe systemic hypotension.