ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

From a nationwide twin panel, identical twin pairs with highest discordance in cigarette smoking were selected for a study of arteriosclerosis (49 pairs with a mean age of 52 years). Smoking history was obtained in 1975, 1981, and 1986. The mean life-long smoking dose of the smoking cotwins was 20 package-years. The smoking and nonsmoking cotwins had similar systolic and diastolic blood pressures, total plasma cholesterol level, body mass index, and some psychosocial factors; the only difference was found in use of alcohol, which was greater among smoking cotwins. Duplex sonography of carotid arteries was performed. Carotid artery stenoses (narrowing of area of the lumen with 15–60%) were found in nine pairs: in nine smoking twins and in two of their nonsmoking cotwins (p= 0036). The total area of carotid plaques was 3.2 times larger in smoking cotwins (p< 0.001). The thickness of the inner layer of carotid arteries was more marked in smoking cotwins (p< 0.001). The size of plaques and the degree of inner layer thickening correlated with the dose of smoking (NS). The association of smoking with carotid arteriosclerosis was highly significant even after the adjustment for age, total plasma cholesterol level, diastolic blood pressure, and body mass index in multiple logistic regression analyses.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In 78 consecutive patients with unstable angina, we performed coronary angiography randomized to either the first day of presentation or later during the hospital admission to assess the frequency of intracoronary thrombus and complex coronary morphology relative to the time of symptomatic presentation and the impact of these angiographic features on outcome. Early angiography (17±6 hours) was performed in 42 patients and late angiography in 36 patients (5.7±2.1 days). Twelve patients randomized to late angiography required urgent cardiac catheterization 3.9±2.2 days after admission. Coronary thrombi were present in 43% (18 of 42) of early angiography patients and in 38% (14 of 36) of late angiography patients (p= NS). Only 21% (five of 24) late elective angiography patients had coronary thrombi, but 75% (nine of 12) of late urgent angiography patients had thrombi (p< 0.05 vs. both early and late elective angiography patients). There was no difference in the frequency of complex coronary morphology among patients randomized to early angiography (42%, or 15 of 36), late urgent angiography (42%, or five of 12), and late elective angiography (38%, or nine of 24). Cardiac events (death, myocardial infarction, and urgent revascularization) were more frequent in the patients with coronary thrombus (73%, or 23 of 32), complex coronary morphology (55%, or 16 of 29), and multiple-vessel disease (58%, or 29 of 50) than in the patients without these angiographic features (17%, or eight of 46; 31%, or 15 of 49; and 7%, or two of 28, respectively; allp< 0.05). Multiple regression analysis demonstrated that coronary thrombus was the best angiographic predictor of cardiac events. Thus, angiographic detection of intracoronary thrombi varies according to the temporal relation between angiography and chest pain at rest. Coronary thrombi are also strongly predictive of cardiac events.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Follow-up of 18 patients with aortic dissection (five with type I, one with type II, 11 with type III dissection according to DeBakey) by transesophageal, two-dimensional and color-coded Doppler echocardiography showed a persistence of the false lumen in five of seven patients (71%) after surgery and in nine of 11 patients (82%) after medical therapy. In two patients treated with surgery, the dissected part of the aorta had been resected, whereas in two patients treated medically, a progressive and complete obliteration of the false lumen was observed. In the false lumen, thrombus formation was absent in four, localized in four, and progressive in six patients. Flow within the false lumen could be registered in 14 patients, and two distinct flow patterns were differentiated (laminar biphasic flow or slowly circulating flow). Persisting intimal tears were visualized by two-dimensional echocardiography in four patients, whereas colorcoded Doppler showed an additional one to three intimal tears in the descending aorta in 10 patients. Flow across these intimal tears was biphasic in 75% of patients; that is, systolic flow was directed from the true to the false lumen with diastolic flow reversal. Unidirectional flow was detected in 25% of the communications, directed in 20% from the true to the false lumen, serving as an entry only and in one (5%) as reentry only. Additional information concerning complications like extension of the dissection (one of 18 patients), localized dilatation of the aorta (two of 18 patients), mediastinal hematoma (one of 18 patients), or aortic regurgitation (three of 18 patients) were detected by this method. Concerning the morphologic findings and the detection of flow characteristics, the transesophageal approach was superior to conventional echocardiography especially in the descending thoracic aorta. Thus, transesophageal twodimensional and color-coded Doppler echocardiography seems to be an ideal method not only for the easy detection of aortic dissection but also for follow-up.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The time courses of onset of the electrophysiologic and antiarrhythmic effects of amiodarone were determined with serial electrophysiologic studies in 34 patients with inducible ventricular tachycardia. A standardized oral loading dosage was used for all patients (1,200 mg/day for 14 days; 800 mg/day for 7 days; and 400 mg/day thereafter). Eleven patients had the studies performed at baseline and after 2, 6, 10, and 20 weeks. Subsequently, 23 patients had studies at baseline and after 2 and 10 weeks. Changes in atrial, sinus, and atrioventricular nodal properties and in conduction intervals were maximal within 2 weeks (early effects). For example, atrioventricular nodal Wenckebach cycle length increased between baseline (369±80 msec) and 2 weeks (498±78 msec) (p< 0.001) but did not change further after 10 weeks (500± 89 msec). However, ventricular Class III effects required 10 weeks to become maximal (late effects). For example, the QT interval during atrial pacing increased between baseline (355±36 msec) and 2 weeks (406±37 msec) (p< 0.001) and increased further after 10 weeks (436±45 msec) (p< 0.001). Antiarrhythmic effects also followed different time courses of onset. Suppression of ventricular premature beats was maximal within 2 weeks. However, suppression of ventricular tachycardia inducibility and slowing of ventricular tachycardia rate was not maximal for 10 weeks. Correlations between serum desethylamiodarone concentrations and some late effects suggest that the mechanism of the time delay to maximal ventricular Class HI effects may involve desethylamiodarone. In conclusion, the time courses of onset of the electrophysiologic and antiarrhythmic effects of amiodarone are dependent on the site and type of effect.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Concealed anterograde penetration of the atrioventricular (AV) node has been used to explain a wide variety of electrocardiographic findings. The effects of atrial rate acceleration on this phenomenon remain undefined. To examine the dynamic interrelations between conducted and nonconducted beats at different atrial rates, a unique atrial pacing protocol of functional 2:1 AV block was used in 10 patients. The pacing protocol involved abrupt transitions from 2:1 to 1:1 AV conduction and enabled quantification of conduction delay produced by nonpropagated impulses over extremes of atrial rate. Stable 2:1 AV conduction was maintained over a mean range of atrial paced cycle lengths of 289±29.6 to 223±33.0 msec, respectively. The mean AV conduction time during 2:1 and corresponding 1:1 drives at the longest atrial paced rates were 169±33.5 and 136.5±26.9 msec, respectively-revealing a significant effect of nonpropagated impulses on subsequent conduction. Surprisingly, at the shortest atrial paced rates, the mean AV conduction times were 191.5±31.8 and 161.0±23.3 msec, respectively. The lack of significant changes in conduction time between 2:1 and 1:1 drives at the extremes of atrial rate (32.5 vs. 30 msec,p= NS) suggests that the effect of concealed conduction is “fixed” and independent of rate. Clinical implications and postulated electrophysiologic mechanisms are discussed.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Cardiotonic agents influence myocardial energy consumption by vasodilation, which may reduce energy demand, and by inotropism, which may increase it. To distinguish between the two effects, myocardial oxygen consumption must be analyzed in relation to its hemodynamic determinants. The coupling of myocardial oxygen consumption with its determinants was investigated in 22 patients with idiopathic dilated cardiomyopathy (NYHA Class II and III). Predicted myocardial oxygen consumption by the pressure-work index, the Bretschneider index, and the pressure-volume area correlated moderately with measured myocardial oxygen consumption (r= 0.57,p< 0.001;r= 0.52,p< 0.005; andr= 0.63,p< 0.001). Multiple regression analysis, including left ventricular peak systolic wall stress, systolic stress-time integral, pressure-volume work, maximum rate of left ventricular pressure rise, and mean velocity of circumferential fiber shortening indicated that systolic stress-time integral is the major determinant of myocardial oxygen consumption (r= 0.75,p< 0.001) in these patients. Enoximone, a phosphodiesterase inhibitor, has an inotropic and a vasodilating effect. To investigate the inotropic portion of the energy cost of this phosphodiesterase inhibitor, the influence of enoximone on myocardial oxygen consumption and systolic stress-time integral was compared with the effects of nitroprusside, which is a vasodilator only. Nitroprusside (10 patients) and enoximone (12 patients) reduced left ventricular systolic stress-time integral from 109±22 to 71±21 (p< 0.005) and from 104±23 to 42±10 (p< 0.001) 103 dynes sec/cm2, respectively. Myocardial oxygen consumption decreased from 159±44 to 112±23 (p< 0.005) and from 134±28 to 109±21 (p< 0.001),μl/beat/100 g, respectively. In both groups, there was a significant correlation between the decrease in myocardial oxygen consumption and the decrease in systolic stress-time integral. The slopes of the respective linear regression lines were significantly different (1.27 for nitroprusside and 0.51 μl·cm2/100 g·dynes·sec for enoximone,p< 0.05), indicating a smaller decrease of myocardial oxygen consumption for a given decrease of stress-time integral with enoximone. Applying the pressure-work index or the pressure-volume area instead of systolic stress-time integral yielded comparable results. Thus, vasodilation reduces myocardial oxygen consumption in proportion to the reduction of stress-time integral. With enoximone, the energy-saving effect of vasodilation is counteracted in part by the increased energy demand of inotropic stimulation.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Digitalis glycosides exert both excitatory and inhibitory autonomic actions in animals and produce vasoconstriction in normal humans but produce vasodilation in heart failure patients. To determine whether or not these contrasting vascular responses are due to differing autonomic actions of the drug, we compared the responses to intravenous administration of Cedilanid-D (0.02 mg/kg) in eight normal subjects (mean age, 23±1 years) and eight patients with moderate-to-severe heart failure (mean age, 52±5 years, NYHA Class III-IV). Hemodynamics and efferent sympathetic nerve activity to muscle (MSNA) were measured during 5-minute periods before (control) and 20 minutes after drug administration. In the heart failure patients, Cedilanid-D significantly increased systolic and pulse pressures, whereas mean arterial pressure was unchanged. There was a decrease in right atrial pressure and a tendency for a decrease in pulmonary artery diastolic pressure with a slowing of heart rate. Cardiac index increased by 24±7%. Short-term administration of digitalis in these heart failure patients produced a fall in forearm vascular resistance (from 37.6±8.2 to 31.8± 8.1 units,p< 0.05) and an early, profound, and sustained decrease in MSNA (from 831.0±118.4 to 474.4±103.6 units/100 heart beats,p< 0.01). Digitalis glycosides produced different vascular and MSNA responses in the normal subjects. In the normal volunteers, the drug significantly increased systolic, mean, and pulse pressures and decreased central venous pressure and heart rate. Despite the significant increase in arterial pressure, there was no change in forearm vascular resistance (from 11.7±1.0 to 12.7±1.0 units,p= NS) or MSNA (from 494.8±88.5 to 369.1± 60.5 units/100 heart beats,p= NS), suggesting a sympathoexcitatory response in normal subjects. To determine whether or not the digitalis-induced sympathoinhibition in the heart failure patients was simply due to an inotropic effect (stimulation of inhibitory cardiac mechanoreceptors), we studied the responses of seven additional patients with heart failure before and during administration of dobutamine (3.4±0.4 μg/kg/min). Dobutamine produced a 34±3% increase in cardiac index, no significant change in systemic arterial pressures, a decrease in pulmonary artery diastolic and right atrial pressures, and no change in heart rate or forearm vascular resistance (from 30.2 ±4.3 to 26.5 ±4.7 units,p= NS). In contrast to the sympathoinhibition seen after digitalis administration and despite comparable inotropic effects of the two agents, there was no change in MSNA during dobutamine infusion (from 527.6±112.7 to 443.7± 95.9 units/ 100 heart beats,p= NS). These studies provide the first direct evidence that digitalis glycosides produce marked sympathoinhibitory actions in humans with heart failure, an efect that likely cannot be ascribed solely to an inotropic action of the drug. We suggest these autonomic effects result from afferent activation of low- or high-pressure baroreceptor mechanisms by digitalis in patients with heart failure.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The static elastic properties of arterial tree (abdominal aorta and common carotid artery) were studied in 19 normal subjects and in 49 patients with myocardial infarction with an ultrasonic phase-locked echo-tracking system that allows continuous transcutaneous measurement of the arterial diameter. The stifness index β which represented the mechanical properties in the arterial wall, was calculated from the relation between systemic blood pressure and the diameter of the artery. Patients with myocardial infarction underwent coronary angiography in their convalescent period to determine involved vessels. In 11 patients, coronary artery was patent; 15 patients had one-vessel disease, 12 had two-vessel disease, and the remaining 11 patients had three-vessel disease. In normal subjects, increasing age was associated with an increase in arterial stiffness. An average value of the stiffiess index of the abdominal aorta was 8.58±3.02 (mean± SD) and that of common carotid artery was 9.17±2.22. In patients with three-vessel disease, these values were significantly higher (22.37±4.29 in abdominal aorta and 13.17±4.56 in common carotid artery) than those in normal subjects. Stiffness index of patients with two- or one-vessel disease was also increased but lower than those in patients with three-vessel disease (p< 0.05). Forty-four of 49 patients with infarction had an arterial stiffness index of abdominal aorta higher than the 95% confidence limits of the normal data (p< 0.05). Twenty-eight patients were outside the nomogram of common carotid artery (p< 0.05). The mechanical properties of these elastic arteries provided sufficiently reliable information on changes caused by atherosclerosis.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exerciseinduced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23–100%; SD, 16%; and mean specificity, 77%; range, 17–100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a “better” test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

ISSN:0009-7322    

出版商:OVID    

年代:1989

数据来源: OVID