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Biomedical subjects

J G Stevenson

Publications and source records attributed to J G Stevenson.

At least 55 records · Page 3Linked to original sources
PubMed1986

Comparison of high pulse repetition frequency and continuous wave Doppler echocardiography for velocity measurement and gradient prediction in children with valvular and congenital heart disease.

To compare the ability of high pulse repetition frequency and continuous wave Doppler echocardiography to detect the peak velocity of a jet flow disturbance and to predict pressure gradients accurately, two groups of children with valvular or congenital heart disease were examined using both Doppler techniques. The use study group included 84 children or adolescents (aged 1 day to 19 years) who underwent examination in the echocardiography laboratory with both Doppler techniques in a randomized sequence. The peak velocity recorded with high pulse repetition frequency Doppler echocardiography was compared with the peak velocity recorded with the continuous wave technique. The accuracy study group included 41 children or adolescents (aged 1 day to 16 years) who underwent examination with both Doppler techniques at the time of cardiac catheterization. Doppler pressure gradients were calculated from the peak velocity using the simplified Bernoulli equation and were compared with peak instantaneous gradients and peak to peak gradients measured at catheterization. In the use study, a high correlation was found between peak velocities detected by high pulse repetition frequency and continuous wave Doppler echocardiography (r = 0.94, SEE = 0.28 m/s). In the accuracy study, close correlations were found between measured peak to peak pressure gradients and pressure gradients calculated from continuous wave (r = 0.95, SEE = 7.9 mm Hg) and high pulse repetition frequency Doppler echocardiography (r = 0.94, SEE = 8.7 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Doppler evaluation of atrial septal defect, ventricular septal defect, and complex malformations.

The Doppler approaches, accuracy, pitfalls and quantitation of atrial and ventricular shunts are reviewed. For both levels of shunting, Doppler demonstration of flow through the septum confirms the diagnosis and directional flow information may provide physiologic information. Shunt sizes may be measured directly by Doppler, and should be reflected by chamber dimensions and volumes. The flow disturbances present in complex malformations such as Ebstein's malformation, transposition of the great arteries with ventricular septal defect, atrial shunting before and after balloon atrial septostomy, total anomalous pulmonary venous return, closely related high velocity flows and coarctation are described. A sequential approach to each anomaly allows one to evaluate each, even if multiple defects are combined in a given patient.

Aortic Coarctation↗
PubMed1986

Doppler evaluation of surgically repaired congenital heart disease.

Surgical repair of a wide variety of congenital heart defects has become commonplace. Evaluation of the adequacy of the surgical repair, and the effects of growth and time upon these repairs has traditionally been through clinical evaluation or invasive study; each method has limitations. Doppler echocardiography provides an accurate and fully noninvasive means for initial evaluation at the time of surgery, and for serial follow-up, without the risk or cost of invasive study. Applications and experience with Doppler evaluation of a variety of surgically repaired defects are discussed. For most lesions, Doppler echocardiography is the procedure of choice for post-operative evaluation.

Aortic Valve Insufficiency↗
PubMed1986

Doppler pressure gradient estimation in children. Accuracy, effect of activity and exercise, and the need for sedation during examination.

Noninvasive estimation of pressure drop has been shown to be an accurate and useful application of Doppler echocardiography. Most accuracy series have used patient-sedated catheterization gradient measurements as the standard of reference. Doppler gradient estimates, however, are commonly made without sedation of the patient when hemodynamics may differ from those present at catheterization. We questioned whether "unsedated" Doppler gradient estimates would correlate in a useful way with "sedated" catheter measurements, Doppler gradient estimates would vary with patient activity, exercise or crying, and Doppler gradient estimates made using chloral hydrate sedation would prove useful in predicting sedated catheter measurements. Twenty-five infants and children were examined under conditions 1 and 2 above, and 20 under condition 3. Sedated Doppler estimates, performed at the time of catheterization corresponded closely with catheter measurements (r = 0.97, SEE = 4.8), confirming the accuracy of the Doppler method. Gradients estimated by Doppler without sedation, or with activity, correlated poorly with sedated catheter measurements (SEE = 16.2, SEE = 34.9, respectively). Use of chloral hydrate sedation for Doppler estimates resulted in good correlation with subsequent sedated catheter measurements. The results demonstrate marked increases in noninvasive Doppler pressure gradient estimates under conditions other than sedation. Clinicians tend to think in terms of sedated catheter gradients as the standard of reference for evaluation of severity and need for surgery. Ultrasonic data can only be used if Doppler estimates are performed under similar physiologic conditions; in children this requires sedation.

Adolescent↗
PubMed1985

Tetralogy of Fallot: selective staged management.

One hundred twenty-four patients with tetralogy of Fallot have undergone either primary total repair (61), shunt and later repair (30), or an initial shunt (33). The mean ratio of pulmonary anulus to descending thoracic aorta increased from 0.80 +/- 0.25 before the shunt to 1.22 +/- 0.26 before the repair (p less than 0.0001). The mean ratio in the primary repair group was 1.23 +/- 0.25. A transannular patch was necessary in only six of 91 patients (6.6%). Postrepair right ventricular/left ventricular pressure ratio averaged 0.50 +/- 0.11 in the shunt plus repair group and 0.43 +/- 0.12 in the primary repair group. Only four patients had a right ventricular/left ventricular pressure ratio less than 0.65. A significant inverse linear relationship existed between this ratio and the pulmonary anulus size measured at operation and normalized for the patient's height (p less than 0.01). Postoperative complications occurred in 21% of patients after a shunt and 20% of patients after open heart repair. The early mortality was 0.8% (1/124). An initial shunt in patients with a small pulmonary anulus can result in an increased anulus size and better hemodynamic result with frequent avoidance of a transannular patch. Staged repair may result in improved overall mortality rates.

Child, Preschool↗
PubMed1984

Noninvasive estimation of peak pulmonary artery pressure by M-mode echocardiography.

In an attempt to predict peak pulmonary artery pressure from routine M-mode echocardiographic tracings, 95 infants and children with congenital heart disease were examined. Following the Burstin method for prediction of peak pulmonary artery pressure, which was originally based on the phonocardiogram and jugular phlebogram, M-mode echocardiography was used to measure the interval from pulmonary valve closure to tricuspid valve opening, namely, the period of isovolumic diastole. The measured interval was plotted on a modified table relating the interval, heart rate and predicted peak pulmonary artery pressure. The peak pulmonary artery pressure predicted by echocardiography was compared with that measured at cardiac catheterization. The correlation between predicted and actual peak pulmonary artery pressure was good (r = 0.86) for routine studies with the patient in the nonsedated state. All patients with a predicted peak pressure less than 40 mm Hg were found at catheterization to have a pressure less than 40 mm Hg. The correlation was better (r = 0.96) when comparing predictions made from the echocardiogram obtained while the patient was sedated for catheterization. Prediction of the magnitude of elevation of peak pressure was especially good when prediction and measurement were nearly simultaneous. Predictions were less accurate in the presence of tachycardia at rates of more than 155 beats/min. The method for estimating peak pulmonary artery pressure from M-mode echocardiographic tracings is reliable, relatively simple and clinically useful.

Blood Pressure↗
PubMed1984

Noninvasive determination of pressure gradients in children: two methods employing pulsed Doppler echocardiography.

Pulsed Doppler echocardiography has been considered poorly suited for high velocity blood flow measurement, because of the problem of signal aliasing. Two methods for reduction of aliasing in a pulsed system were evaluated in an attempt to measure flow velocities characteristic of significant pressure gradients. With the angle correction method, carrier frequency, pulse repetition frequency and intercept angle were manipulated using a commercially available two-dimensional pulsed Doppler system. Forty children undergoing cardiac catheterization were studied. Gradients of 60 to 70 mm Hg were accurately predicted by this method, and gradients above 90 mm Hg were underestimated. Overall correlation (r) value was 0.95. The method is limited primarily by the introduction of potential error in measurement of intercept angle; it is advantageous in that it can be attempted using currently available pulsed Doppler echographic systems. With the multiple sample volume method, pulse repetition frequency was increased through the addition of extra sample volumes. Carrier frequency was minimized and angle correction was not employed. Thirty-nine children underwent cardiac catheterization using a prototype instrument. Excellent agreement between Doppler predictions and actual gradients was found for gradients up to 100 mm Hg (r = 0.99). Although this method requires new instrumentation, it is advantageous in that gradients are accurately predicted and cannot be overestimated. Both methods retain the advantages of pulsed Doppler study for comprehensive flow evaluation and reference their quantitative application within a two-dimensional echographic format. Neither method is simple, and each has been validated only in pediatric subjects.

Aortic Valve↗
PubMed1984

Arteriohepatic dysplasia: phenotypic features and family studies.

Arteriohepatic dysplasia (AHD) is a disorder characterized by intrahepatic cholestasis and peripheral pulmonary artery stenosis. We have reviewed the phenotypic features in the 56 previously reported cases and 7 persons from our institutions with AHD to summarize the type of cardiac, hepatic, facial, ocular and skeletal manifestations observed in this disorder. Family studies evaluating first-degree relatives of patients with AHD are compatible with an autosomal dominant mode of inheritance with reduced penetrance and variable expressivity.

Abnormalities, Multiple↗
PubMed1984

Sexual dysfunction due to antihypertensive agents.

A review of sexual dysfunction due to antihypertensive agents is presented. Sexual dysfunction is a relatively common complication of antihypertensive drug therapy and has been associated with nearly all of the antihypertensive agents. The physiology of the normal sexual response, proposed mechanisms of sexual dysfunction, and the types of disorders and relative incidence rates associated with individual agents are discussed. Since a disturbance in sexual function may lead to poor compliance with the drug regimen, it is important that the clinician be familiar with this topic. Information on the detection of antihypertensive-agent-induced sexual dysfunction, patient counseling, and therapeutic alternatives, should a disorder in sexual function occur, also is provided.

Adrenergic beta-Antagonists↗
PubMed1984

Pulsed Doppler echocardiographic evaluation of ventricular septal defect patches.

Doppler echocardiography has been shown to have high sensitivity and specificity for noninvasive detection of the flow disturbance of ventricular septal defect. After surgery for ventricular septal defect, one might expect loss of the ventricular septal defect flow disturbance. We used two-dimensional and pulsed Doppler echocardiography to evaluate 30 children undergoing surgery for ventricular septal defect to determine postoperative Doppler findings and the effect of ventricular septal defect patch material on those findings. Twenty-one patients had Dacron patches and nine pericardial patches. Doppler examinations were performed immediately after surgery and at intervals thereafter. The patches were imaged on two-dimensional echocardiograms and the Doppler method was used to evaluate flow at the patches. Doppler echocardiography was also used to estimate volume flow in the aorta and pulmonary artery to estimate postoperative ratio of pulmonary to systemic flow (Qp/Qs). Immediately after surgery 93% of patients had a flow disturbance detected by Doppler echocardiography in the region of the surgically placed patch. On postoperative day 1, 62% of Dacron-patched defects and 66% of pericardial patched defects showed evidence of residual shunting on Doppler examination. By the third postoperative day, this prevalence fell to 23% and 44%, respectively. By 2 weeks after surgery there was evidence of residual shunting in only two patients. In 26 of 30 early postoperative Qp/Qs estimates were under 1.6/1; all but two of these lost the Doppler-detected flow disturbance by 2 weeks after surgery. In three of 30 Qp/Qs estimates exceeded 1.9/1; two of these three required reoperation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Volume Determination↗
PubMed1984

Hemodynamic effects of ketamine in children with congenital heart disease.

Pulmonary and systemic vascular responses to ketamine (2 mg X kg-1, intravenously) were studied during cardiac catheterization in 20 children with congenital heart lesions. Pulmonary and systemic resistances (Rp, Rs), ratios between pulmonary and systemic flows (Qp/Qs), and left to right (L----R) and right to left shunts (R----L) were calculated before and after ketamine administration. Statistically significant (P less than 0.05) but clinically minor increases in heart rate (106.8 to 109.9 beats/min), mean pulmonary artery pressure (20.6 to 22.8 mm Hg), and Rp/Rs (0.12 to 0.14) were seen after ketamine. There were no significant changes in systemic arterial pressure, Rs, Qp/Qs, L----R, R----L, or arterial oxygen or carbon dioxide tensions. No patient had any major untoward effects from ketamine administration. It is concluded that the hemodynamic alterations after ketamine administration in children undergoing cardiac catheterization are small and do not alter the clinical status of the patients or the information obtained by cardiac catheterization.

Blood Gas Analysis↗
PubMed1983

Noninvasive evaluation of Blalock-Taussig shunts: determination of patency and differentiation from patent ductus arteriosus by doppler echocardiography.

Pulsed Doppler echocardiography has been used to detect continuous turbulent flow in the right pulmonary artery after Blalock-Taussig shunts. Since continuous turbulent flow could also arise from patent ductus arteriosus (frequently present in the neonate), continuous turbulent flow in the right pulmonary artery is not specific for Blalock-Taussig shunt function. We evaluated 35 Blalock-Taussig shunts from suprasternal or high parasternal approach for flow in the right pulmonary artery, and in the Blalock-Taussig shunts themselves. From precordial approach, Doppler evaluations of the main pulmonary artery were also made in search of flow characteristic of patent ductus arteriosus. Doppler detection of flow within the Blalock-Taussig shunts indicated shunt patency, and indicated that continuous turbulent flow in the right pulmonary artery was not due to only patent ductus arteriosus. Shunts were proven patent in 31 patients, occluded in four. Twelve patients also had patent ductus arteriosus. By Doppler, the right pulmonary artery had continuous turbulent flow in 30 of 31 patients in whom the right pulmonary artery was found. From the suprasternal or high parasternal approach, the right Blalock-Taussig shunts were detected by marked continuous turbulent flow directed away from the transducer, between the aortic and superior vena caval flow signals. Left Blalock-Taussig shunts had similar directional continuous turbulent flow. Prosthetic shunts were identified by the dense shunt material. Twenty-four of 31 functional shunts were identified, and all contained continuous turbulent flow. Three left-sided shunts were missed. All four occluded shunts were identified by Doppler, and had no lumen flow within.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis, Differential↗
PubMed1982

Left ventricular performance in endotoxin shock in dogs.

Endotoxin shock, with maximal velocity of contraction (Vmax) as our index of contractility, showed no myocardial depression in an earlier 4-h study (Guntheroth, Proc. Soc. Exp. Biol. Med. 157: 610--614, 1978). Because of reports of late deterioration, we studied six dogs until spontaneous death (9--18 h). Heart rate nearly doubled and left ventricular filling pressure and aortic mean pressure fell, but Vmax did not change significantly. Because of concern that the marked increase in heart rate may have contributed to an artifactual maintenance of Vmax (due to its frequency dependence, inherent in dp/dt), we studied a final group of five dogs with three additional indicators of contractility. End-systolic pressure-diameter ratio (Emax), ejection fraction (sonar-determined from the minor axis of the left ventricle), and frequency-normalized average rate of generation of power density (FARPD) all fell early and remained low until death. We conclude that myocardial contractility is significantly reduced in endotoxin shock, early and sustained. Its presence is masked somewhat in the untreated subject by the reduced work load, secondary to hypovolemia.

Animals↗
PubMed1980

Doppler echocardiography: applications, limitations and future directions.

On the basis of principles that are similar to (but differ slightly from) those that underlie M mode and two dimensional techniques, pulsed Doppler echocardiography permits evaluation of intracardiac blood flow noninvasively. This technique is helpful in the diagnosis and management of patients with valvular and congenital heart disease, and in some circumstances provides information not available from M mode or two dimensional imaging. Despite several notable limitations, pulsed Doppler echocardiography is a useful diagnostic technique whose clinical application is likely to increase as future technologic improvements occur.

Aortic Valve Insufficiency↗