Arterial concentration of 99mTc-sestamibi at rest, during peak exercise and after dipyridamole infusion

Tracers for myocardial perfusion imaging during stress should not only have high cardiac uptake but they should also have a fast blood clearance to prevent myocardial tracer uptake after the ischaemic stimulus. The present study characterize the early phase of the arterial (99m)Tc-sestamibi (MIBI) time-activity curve after venous bolus injection at rest, during peak exercise and after dipyridamole infusion. We included 11 patients undergoing angioplasty for one-vessel disease (rest study) and 20 patients evaluated for the detection of haemodynamic significant coronary stenoses by (99m)Tc-sestamibi single photon emission computed tomography (SPECT) using either bicycle exercise testing (10 patients) or standard dipyridamole testing (10 patients). Arterial blood samples of 1 ml were taken from the left femoral artery (rest study) or the right radial artery (exercise and dipyridamole studies) every 5 s during the first 5 min postinjection. In the exercise and the dipyridamole studies blood sampling were extended to include blood samples every 5 min 5-30 min postinjection. Peak MIBI concentration was lower and decrease in concentration slower after tracer injection during exercise than during dipyridamole stress testing. This may cause an underestimation of perfusion defects during exercise because of MIBI uptake after the ischaemic stimulus. The implications of the study not only refer to the choice of stress modality when using MIBI. This study also underlines the importance of considering early blood clearance in addition to regional myocardial tracerkinetic aspects such as myocardial extraction fraction when new tracers are introduced.     

Platelet release of beta-thromboglobulin within the coronary circulation during cold pressor stress

Cold stress by increasing circulating catecholamines may sensitize blood platelets to aggregate and release their constituents. This study investigates the effect of cold stress on the release of the platelet-specific protein beta-thromboglobulin into the coronary venous blood of 12 subjects with atherosclerotic coronary artery disease (CAD) and 7 subjects with angiographically normal coronary arteries (NCA). Cold pressor stress caused a greater increase in systolic arterial pressure in patients with CAD than in subjects with NCA (p less than 0.05). There was no significant difference between the platelet counts in the arterial or coronary venous blood either before or during cold stress. Arterial beta-thromboglobulin was higher in the group with CAD (77 +/- 18 ng/ml) than in subjects with NCA (49 +/- 12 ng/ml, p less than 0.01). Although there was no arteriovenous difference of beta-thromboglobulin at rest in either group, during cold stress, coronary venous beta-thromboglobulin increased in both the NCA (53 +/- 16 to 95 +/- 26 ng/ml, p less than 0.05) and CAD groups (76 +/- 13 to 117 +/- 53 ng/ml, p less than 0.025) despite no change in arterial beta-thromboglobulin. Release of beta-thromboglobulin, although not related to the presence of angiographic arterial disease, correlated with the systolic arterial pressure during cold stress (r = 0.66) and inversely with the platelet's ability to generate cyclic adenosine monophosphate (r = 0.69). The release of platelet constituents in the coronary circulation is provoked by cold stress and may play a role in stress-induced acute coronary occlusion in patients with atherosclerotic disease and in those with apparently normal vessels.     

Precordial electrocardiographic mapping in the identification of patients with left main stem narrowing

This study was designed to determine if exercise testing using 16-lead precordial mapping can be used to identify patients with left main stem narrowing. In a group of 235 consecutive patients undergoing coronary angiography there were 35 patients with left main stem narrowing. The patients with left main stem disease differed from the others in that not only did they develop extensive S-T segment depression, but more specifically these changes occupied a characteristic position high on the precordium above the usual site of the precordial leads of the 12-lead electrocardiogram. This finding was then tested prospectively in a second group of 100 patients. Fourteen of the 100 patients had left main stem narrowing; the sensitivity and specificity of S- T segment changes high on the precordium in identifying patients with left main stem disease were 82 and 84% respectively. Thus precordial mapping and exercise testing is valuable in the diagnosis of patients with left main stem narrowing. The technique is simple and inexpensive and provides data not available using the conventional precordial leads of the 12-lead electrocardiogram.     

Programmed electrical stimulation of the heart in coronary artery disease

The induction of ventricular arrhythmia in patients with a history of malignant ventricular arrhythmia by programmed electrical stimulation (PES) is associated with a poor prognosis. However, the incidence and significance of inducible arrhythmia in patients with stable coronary artery disease (CAD) who do not have a history of serious arrhythmia are unknown. We studied 32 such patients (31 men, mean age 55 years) with PES at the time of cardiac catheterization. Fourteen patients (Group I) manifested greater than or equal to 3 extraventricular responses when challenged with 1 to 3 propagated right ventricular extrastimuli during ventricular pacing. Twelve (86%) of these 14 had evidence of left ventricular dysfunction (LVD), defined by a global ejection fraction of less than 50% or regional wall motion abnormalities. The remaining 18 patients (Group II) manifested less than or equal to 2 responses to extrastimulation. Only 4 (22%) of these 18 had LVD. Proximal 3-vessel CAD was more frequent in Group I patients (10 of 14, 71%) than in Group II (7 of 18, 39%). Only 5 patients (4 from Group I and 1 from Group II) demonstrated complex arrhythmia during exercise testing or ambulatory monitoring. The induction of extraventricular responses during PES may serve as an independent marker of electrical instability in the coronary population and is a much more common finding in those with LVD.     

Left ventricular function during systole and diastole in mitral incompetence

Left ventricular function during systole and diastole was studied in 17 young patients with mitral incompetence and sinus rhythm; 13 had established chronic mitral incompetence, 3 had prolapsing posterior leaflet syndrome and 1 had ruptured chordae tendineae. In chronic mitral incompetence and prolapsing posterior leaflet syndrome, clinical disability was related to a low forward stroke index, a large regurgitant volume and tall left atrial V wave. The defect was mechanical, and the ventricle had adapted by compensatory dilatation so that overall systolic function was normal, as measured by peak rate of rise of left ventricular pressure ($\text{dP}\text{dt}$) and ejection fraction. The dilated ventricle operated at a normal or slightly increased end-diastolic pressure, a consequence of normal resting tension (O point) and a more elastic myocardium with a low rate of change of instantaneous stiffness (m) and a flattened diastolic pressure-volume curve.In acute mitral incompetence, systolic function was normal but the sudden volume overload caused the unprepared ventricle with an almost normal modulus of elasticity and slope (m) to ascend its pressure-volume curve in diastole. End-diastolic pressure was increased.     

Morphology of chronic lymphocytic leukemia and its relationship to survival

The morphology of lymphocytes in blood and bone marrow from patients with chronic lymphocytic leukemia was studied; blood lymphocyte morphology was related to survival. Three primary morphologic groups emerged. Group I was characterized by small to medium-sized lymphocytes with narrow rims of cytoplasm and coarsely clumped nuclear chromatin. In group II the predominant lymphocytes were large with abundant cytoplasm. Group III was characterized by a heterogeneous population of lymphocytes with characteristics of both groups I and II. Clinical features of the patients were studied, and B and T typing of the lymphocytes was done. The median survival in group I was 26+ months; In group II 46+ months; and in group III 50+ months. Our data are at variance with previous reports and suggest that survival in patients with large lymphocytes Is longer than in those with small lymphocytes.     

“四川省医院科技能力评价指标体系”的信度与效度检验及鉴别力与区分度分析

目的探讨已建立的＂四川省医院科技能力评价指标体系＂的信度与效度检验及鉴别力与区分度。方法采用分层随机抽样的方法对回收合格的调查问卷进行整理,抽取54家二、三级医院进行实证研究,采用克朗巴哈系数、因子分析分别检验指标体系的信度和效度。结果整套指标体系、1～3级指标的克朗巴哈系数分别为0.91、0.80、0.79、0.81;二级医院的整套指标体系、1～3级指标的克朗巴哈系数分别为0.89、0.70、0.68、0.78;三级医院的整套指标体系、1～3级指标的克朗巴哈系数分别为0.86、0.60、0.60、0.64。3个一级指标的因子分析结果如下：特征根大于1的公因子1个,累积贡献率为72.885%;因子负荷估计值分别为0.804、0.907、0.847。科技投入的二级指标的因子分析结果为特征根大于1的公因子1个,累积贡献率为48.810%;因子负荷估计值分别为0.824、0.689、0.558。科技管理及活动的二级指标的因子分析结果为特征根大于1的公因子1个,累积贡献率为52.377%;因子负荷估计值分别为0.600、0.647、0.764、0.857。科技产出的二级指标的因子分析结果为特征根大于1的公因子3个,累积贡献率分别为39.371%、66.633%、83.798%。在第一个公因子上,因子负荷估计值分别为0.651、0.652、0.518、0.817、0.759、0.040;在第二个公因子上,因子负荷估计值分别为0.544、0.264、0.747、-0.525、-0.627、-0.208;在第三个公因子上,因子负荷估计值分别为0.252、-0.210、0.068、-0.120、-0.003、0.950。该套指标体系除外5个指标,其余指标的变异系数均在10.00%以上,最高为19.55%。进一步分析指标的整体区分度,三级医院得分均秩为45.25,二级医院得分均秩为22.43,差异有统计学意义（P=0.001）。结论整套指标体系、1～3级指标的克朗巴哈系数均在0.6以上,表明该套指标内部一致性较好,具有较好的信度和效度;鉴别力与区分度的分析说明指标体系的所测结果既具有较好的稳定性又有较强的真实性。     

Retrograde block during dual pathway atrioventricular nodal reentrant paroxysmal tachycardia

There are limited reported data regarding the occurrence of retrograde block during dual pathway atrioventricular (A-V) nodal reentrant paroxysmal tachycardia. This study describes two patients with this phenomenon. The first patient had 2:1 and type 1 retrograde ventriculoatrial block during the common variety of A-V nodal reentrance (slow pathway for anterograde and fast pathway for retrograde conduction). Fractionated atrial electrograms suggested that the site of block was within the atria. The second patient had type 1 retrograde block (between the A-V node and the low septal right atrium) during the unusual variety of A-V nodal reentrance (stow pathway for retrograde and fast pathway for anterograde conduction). The abolition of retrograde block by atropine suggested that the site of block was within A-V nodal tissue. Both cases demonstrate that intact retrograde conduction is not necessary for the continuation of A-V nodal reentrant paroxysymal tachycardia. Case 2 supports the hypothesis that the atria are not a requisite part of the A-V nodal reentrant pathway.