摘要:

We assessed the changes in cardiac chamber size, architecture and function in the normal fetus in a prospective, longitudinal, two-dimensional, and two-dimensionally directed M mode echocardiographic study. Serial echocardiograms were recorded in 16 normal fetuses at 4 week intervals from 20 weeks gestation to parturition. Fetal gestational age was assessed by biparietal dianmeter. Left ventricular, right ventricular, and left atrial chamber sizes and aortic diaimieter all increased linearly with age. The ratios of right and left ventricular diameter, left atrial to aortic diameters, and relative left ventricular wall thickness that we used as an index of short-axis left ventricular architecture remained constant. Fractional right ventricular and left ventricular cavity shortening did not change significantly throughout the period of study. Right and left ventricular wall thicknesses were similar both on echocardiograms and in postmortem hearts over the same range of gestational ages. In addition, postmortem right ventricular and left ventricular free wall weights were indistinguishable and contributed the same proportion to total heart weight throughout gestation. Left ventricular echocardiographic mass increased linearly from a mean of 0.86 ± 0.09 to 7.47 ± 2.43 g at term and corresponded closely with postmortem left ventricular weight. We conclude that (1) fetal cardiac chamber dimensions, wall thicknesses, and left ventricular mass increased with gestational age, (2) cardiac architecture in terms of the ratios of right ventricular/left ventricular diameters, left atrial/ aortic diameters, and relative wall thickness remained constant, (3) right and left ventricular fractional shortening did not change with age, (4) left ventricular mass assessed echocardiographically corresponded closely with postmortem left ventricular weights in fetal hearts of similar gestational ages, and (5) the similarities between right and left ventricular sizes, wall thicknesses, and free wall weights in this study do not support the theory of right ventricular dominance in the human fetus.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

At the time of surgical repair, a lung biopsy was performed on patients with congenital heart defects who either had pulmonary hypertension or in whom it would be likely to develop if the lesion were not corrected. Pulmonary vascular changes, assessed morphometrically and also according to the classification of Heath and Edwards (Circulation 18: 533, 1958), were correlated with the postoperative pulmonary hemodynamic findings: mean pulmonary arterial pressure the day after correction and mean pulmonary arterial pressure and pulmonary vascular resistance measured 1 year later. On the first postoperative day, increased mean pulmonary arterial pressure was uncommon in patients with morphometric grade A or B (mild) biopsy findings and Heath-Edwards grade N (normal), and if it was present it was of a mild degree. Mean pulmonary arterial pressure was commonly elevated in those with grade B (severe) or C (mild or severe) and Heath-Edwards grade biopsy results and was more frequently elevated in those with grade findings. Moderate-to-severe elevation of mean pulmonary arterial pressure was invariable in patients with Heath-Edwards grade III changes regardless of the morphometric grade. One year after repair, mean pulmonary arterial pressure and/or pulmonary vascular resistance were normal in all patients whose conditions were corrected surgically before 9 months of age regardless of the severity of the pulmonary vascular changes. Values were normal in patients whose conditions were repaired surgically at 9 months of age or later who had grade A or B (mild) morphometric findings with any Heath-Edwards grade or grade B (severe) morphometric findings with Heath-Edwards grade I but were increased in half of the patients with grade B (severe) morphometric findings and Heath-Edwards grade II or with grade C (mild or severe) and Heath- Edwards grade I or LI changes. Pulmonary arterial pressure and pulmonary vascular resistance were increased in all patients whose conditions were repaired after 2 years of age with grade C morphometric findings and to a severe degree if associated with Heath-Edwards grade III. Thus, although the Heath- Edwards grade can usually be used to identify patients at risk for pulmonary hypertension in the early postoperative period, both the morphometric and the Heath-Edwards grades as well as the age of the patient at the time of repair can be used to determine whether pulmonary arterial pressure and resistance eventually return to normal or remain elevated.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

In the Australian therapeutic trial in patients with mild diastolic hypertension, univariate analysis of possible prognostic characteristics (covariates) at the time of entry into the study showed a higher incidence of trial end points. mainly events due to ischemic heart disease and cerebrovascular disease, in older subjects, men, cigarette smokers, and those with higher systolic blood pressures and lower body mass indexes than in their complementary groups. There was a lower incidence of these events in actively treated subjects than in control subjects at both high and low levels of incidence of each covariate considered, but treatment benefit was most marked in those with lower serum cholesterol levels and lower systolic blood pressures. Multivariate regression analyses of data fronm men and women separately, performed with the Cox proportional-hazards model, confirmed that the incidence of trial end points increased with age and with systolic blood pressure, and showed higher rates in cigarette smokers, which increased markedly with decreasing body weight. With respect to the effects of treatnient. the multivariate analysis showed an increasing benefit with decreasing body weight in smokers. The apparent relationship of treatment benefit to systolic blood pressure in the univariate analysis did not reach statistical significance in the multivariate analysis. The greater benefit from treatment related to lower levels of serum cholesterol found in the univariate analysis was also found in several preliminary multivariate analyses, but did not reach statistical significance in the final model. However, this relationship should be tested in other therapeutic trials in progress or recently completed. Similar results were found when ischemic heart disease events alone were considered. This analysis of covariates did not identify any group of subjects in whom drug treatment was not indicated, but as described in an earlier article, approximately half of the patients in the placebo group were normotensive at 3 years. and niost by 4 months. Thus, a period of observation of sonie 4 months should identify a large number of suspected mild hypertensives who do not require antihypertensive drug treatment.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

In a randomized double-blind trial we sought to determine whether short-term therapy with ticlopidine (250 mg bid for 14 days) inhibited platelet deposition on Dacron aortic bifurcation grafts that had been in place a year or longer. A total of 10 men, 42 to 69 years old, underwent indium-111 platelet imaging during both placebo and drug phases of the trial at 24, 48, and 72 hr after the injection of labeled platelets. Platelet accumulation was quantitated by a graft/blood ratio that compared background-corrected activity of indium- 11 1-labeled platelets in the graft with whole-blood activity of indium-1 1 1-labeled platelets. Additionally, blinded qualitative visual analysis of the unprocessed images was used to compare graft area activity with activity in adjacent native arteries. Ticlopidine significantly prolonged the template bleeding time from 5.3 ± 0.5 to 17.1 ± 3.1 min (± SEM) (p= .003). However, by quantitative analysis there was no significant reduction in platelet deposition in the graft during ticlopidine therapy compared with placebo at 24 hr (graft/blood ratio 2.3 ± 0.4 vs 2.6 ± 0.3),48 hr(3.l ± 0.5 vs 3.2 ± 0.4),or 72 hr(3.9 ± 0.7 vs 4.0 ± 0.6) afterinjection of labeled platelets. By visual analysis, nine patients had positive results for abnormal platelet deposition when on placebo that were unchanged when on ticlopidine. The tenth patient had an equivocal result for abnormal platelet deposition when on placebo and a negative result for abnormal platelet deposition when on ticlopidine. We conclude that ticlopidine, in a dosage that significantly prolonged the bleeding time, did not inhibit platelet deposition on Dacron prosthetic surfaces in humans. The procedures described in this study may be useful for the evaluation in vivo of platelet accumulation on prosthetic materials and for the study of effects of antithrombotic drugs.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The plasma level of fibrinopeptide A (fpA) was used as an index of thrombin action on fibrinogen in order to investigate the rates of fibrin formation and the effect of heparin on thrombin in patients with acute myocardial infarction. The fpA levels measured on admission in 19 patients with acute myocardial infarction ranged from 1.7 to 12.4 ng/ml and were elevated (>2.5 ng/ml) in 16 patients. A loading dose of 5000 IU of heparin resulted in a significant decrease within 20 min of the mean fpA level (from 5.1 to 2.2 ng/ml;p<.001) and in an fpA normalization in five/ of 16 patients. During the following continuous infusion of 20,000 IU of heparin per day, the mean fpA levels measured on day 0, 1, and 2 were 3.0, 3.2, and 3.4 ng/ml, respectively, with 16 of 46 fpA values within the normal range. In 10 additional patients, the effect of higher concentratio, ns of heparin and the consequences of stopping heparin infusion were studied. An additional 5000 IU of heparin injected intravenously during continuous infusion of 20,000 IU of heparin per day resulted in a substantial decrease of the plasma fpA level in three of 10 measurements. The stopping of heparin infusion led to an impressive increase of the mean fpA level (from 3. 1 to 12.9 ng/ml;p<.001) within 2 hr. These data demonstrate increased fibrin formation in patients with acute myocardial infarction and neutralization of thrombin in vivo by heparin. They also suggest that heparin doses higher than those conventionally used may be required to fully inhibit fibrin formation and that additional thrombin may be generated after cessation of heparin infusion.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Coronary spasm is an accepted cause of transient myocardial ischemia in patients with variant angina; more recently it has been suggested that dynamic stenoses could also play an important role in the pathophysiology of exertional angina. To test this hypothesis we submitted 31 patients with histories typical of exertional angina to ergonovine testing and compared the electrocardiographic and clinical responses to those observed in seven patients with variant angina. All underwent bicycle ergometric exercise testing and coronary angiographic examination. For all tests, ST segment shifts of 0.1 mV or greater were considered to be diagnostic of myocardial ischemia. In patients with exertional angina, exercise testing produced diagnostic ST segment depression in 21 (68%). Ergonovine testing produced diagnostic ST segment depression in nine (29%). All nine had positive exercise test results and two- or three-vessel disease, yet the test was negative in seven other patients with positive exercise test results and similar angiographic findings. Conversely, in the seven patients with variant angina, results of exercise testing were positive in five (ST segment depression in two, ST elevation in three), while ergonovine produced ST segment elevation in all seven. Coronary angiographic examination showed normal arteries in two, one-vessel disease in four, and three-vessel disease in one. Results of all ergonovine tests were positive at values of rate pressure product much lower than those observed during exercise. Consequently it seems reasonable to postulate that in a sizable proportion of patients with exertional angina and diffuse coronary atherosclerosis, dynamic stenoses can contribute to produce ischemia, although the different electrocardiographic response to ergonovine testing suggests that the effects of vasoconstriction are less severe than those in variant angina.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

To assess local myocardial relaxation abnormalities in patients with coronary artery disease, local myocardial left ventricular wall stress was computed in nine normal subjects and in 22 patients with coronary artery disease. In normal left ventricles, the rate of decrease in isovolumic local stress was not significantly different from the rate of decrease in isovolumic pressure, and the residual wall stress at the end of isovolumic relaxation was uniformly low. In patients with coronary artery disease, the residual wall stress was increased both in infarcted areas and in noninfarcted areas perfused by stenosed arteries (43 ± 31 and 30 ± 19 kdyne/cm2, respectively, vs 9 ± 5 kdyne/cm2in normal areas;p<.001). The rate of decrease in local stress in infarcted areas paralleled the rate of decrease in pressure (48 vs 49 msec; NS), but in ischemic areas the rate of decrease in stress was significantly slower than the rate of decrease in pressure (69 ± 35 vs 48 ± 15 msec;p<.05). It is concluded that in patients with coronary artery disease, indexes based only on the analysis of decreases in isovolumic pressure underestimate the severity of local impairments in relaxation rate and cannot be used to predict the level of residual diastolic wall stress.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The feasibility of using continuous on-line recording of intraventricular electrical impedance to measure ventricular stroke volume was assessed in 12 patients at cardiac catheterization with a multielectrode impedance catheter and a 1.3 kHz measuring current of 4 μA. Stroke volumes determined by electrical impedance were compared with stroke volumes determined by the thermodilution technique in 10 patients and correlated with an r value of.95. Directional changes in impedance recordings throughout the cardiac cycle were also compared with volume curves obtained from six patients by radionuclide ventriculography, and in all instances the agreement between the two volume recordings was excellent. For all patients, on-line measurements of impedance showed a beat-by-beat decrease in stroke volume with the Valsalva maneuver and the administration of amyl nitrite, as well as an immediate increase in stroke volume in the contraction following an extra-systolic beat. Similar directional changes in stroke volume were recorded in both left and right ventricles. Left ventricular pressure-volume relationships were assessed with simultaneous left ventricular pressure recordings and volume signals recorded from the impedance catheter to determine if impedance measurements of volume can be used clinically. Pressure-volume diagrams were subsequently plotted, and for all patients these diagrams showed characteristic isovolumetric contraction and relaxation phases as well as typical ejection and filling periods. Moreover, beat-by-beat sequential pressure-volume diagrams constructed for patients during the administration of amyl nitrite revealed a linear end-systolic pressure- volume relationship. We conclude that measurement of intracavitary electrical impedance can be used to monitor instantaneous changes in stroke volume in patients and may be helpful in the construction of pressure-volume diagrams and the assessment of left ventricular end-systolic pressure-volume relationships.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Electrocardiograms obtained from patients during arrhythmia-free intervals do not identify those prone to sustained ventricular tachycardia (VT) despite the occult delayed activation that is presumably present. To determine whether frequency-domain analysis facilitates detection of this hallmark of predisposition to VT, fast-Fourier transform analysis (FFTA) procedures were developed and tested with a computer-generated mathematical model. The FFTA approach developed allows inherent limitations of high-gain amplification and a priori filtering used commonly for time-domain analysis to be avoided. After demonstrating that FFTA detected low-amplitude oscillatory waveforms in signal-averaged recordings in the frequency domain, the procedure was applied to signal-averaged X, Y, and Z lead recordings from the following three groups of patients: group 1, patients with prior myocardial infarction and episodic sustained VT (n= 16); group 11, patients with prior myocardial infarction without overt sustained VT (n= 35); and group Ill, normal control subjects (n= 10). Results of FFTA demonstrated significant (p<.0001) differences in the decibel drop at 40 Hz and the area under the curve from the fundamental frequency to the frequency at which the spectral amplitude was decreased by 60 dB for both the terminal 40 msec of the QRS and ST segment in patients in group 1 compared with those in groups II and II, in whom results were similar. Results were independent of QRS duration (r=.2), left ventricular ejection fraction (r=.19), and complexity of spontaneous ventricular ectopy. Thus, patients known to manifest sustained VT also exhibited relatively greater high-frequency content in arrhythmia-free intervals in the terminal QRS and ST segment than those without VT (88%, 15%, and 0% in groups I through III, respectively). FFTA offers promise for the noninvasive detection of patients at risk for the development of sustained VT.

ISSN:0009-7322    

出版商:OVID    

年代:1984

数据来源: OVID