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Biomedical subjects

A R Snider

Publications and source records attributed to A R Snider.

At least 19 recordsLinked to original sources
PubMed2000

Diastolic function in neonates after the arterial switch operation: effects of positive pressure ventilation and inspiratory time.

OBJECTIVE: To determine the effects positive pressure ventilation have on left ventricular diastolic function in neonates after the arterial switch operation. DESIGN: Prospective case series. SETTING: Pediatric cardiac and multidisciplinary intensive care units in two university-affiliated children's hospitals. PATIENTS AND PARTICIPANTS: The patient population consisted of 12 neonates weighing 2.5-4.2 kg with D-transposition of the great arteries (DTGA) who underwent arterial switch operation. INTERVENTIONS: All patients were mechanically ventilated in a volume-targeted mode with a square wave flow pattern. The positive end-expiratory pressure was held constant. A long inspiratory time was set by extending it over three cardiac cycles. MEASUREMENTS AND RESULTS: Pulsed Doppler measurements of left ventricular diastolic function were performed during the following cardiac cycles: (1) the last diastolic period of expiration (E(L)), (2) first, second and third diastolic periods of inspiration (I1, I2, I3) and (3) the first diastolic period of expiration (E(F)). Doppler measurements of peak E wave, peak A wave, E area/A area, E area fraction, A area fraction, 0.33 area fraction and the deceleration time were made. Doppler tracings were digitized and the data obtained from three sequential study periods were averaged. Data were statistically analyzed using the repeated measures analysis of variance procedure. During (I1), there was a 21% increase in the peak E wave (0.53+/-0.06 vs 0.64+/-0.08 m/s, p < 0.01) and 28% increase in peak A wave (0.47+/-0.07 vs 0.60+/-0.08 m/s, p < 0.01) compared to (E(L)). There was a 24% increase in total area under the E and A waves when I1 was compared to E(L) (0.059+/-0.008 vs 0.073+/-0.009, p < 0.01) and there was no change in mitral valve deceleration time. Compared to the initial diastolic period during inspiration (I1), the third diastolic period during inspiration (I3) had a 38% decrease in peak E (0.64+/-0.08 vs 0.40+/-0.05 m/s, p < 0.01) and 33% decrease in peak A (0.60+/-0.09 vs 0.40+/-0.05 m/s, p < 0.01). In addition, there was a 16% reduction in total area under the E and A waves (0.073+/-0.009 vs 0.061+/-0.008, p < 0.01). There were no changes in the other diastolic indexes that reflect changes in ventricular compliance or relaxation. CONCLUSIONS: In neonates with transposition of the great arteries (TGA) after the arterial switch operation, positive pressure ventilation augments left ventricular filling during the early phase of inspiration. Prolonging the inspiratory time over three cardiac cycles results in a reduction in left ventricular filling during the third diastolic period. There were no changes in the other diastolic indexes that reflect changes in ventricular compliance or relaxation.

Blood Pressure↗
PubMed1998

In vitro analysis of regurgitant fraction using Doppler power-weighted sum of velocities.

The power-weighted sum of velocities (PWS) is the sum of each velocity component of the Doppler signal multiplied by its power. The purpose of this study was to determine (1) whether PWS is linearly related to volume flow and (2) whether PWS can predict the regurgitant fraction in an in vitro pulsatile flow system simulating aortic regurgitation. Doppler analysis of aortic flow was performed with an intact valve and two regurgitant valves. For each valve a linear relation between the forward flow PWS and forward flow volume was demonstrated, with excellent correlation (r = 0.99). For the valves with regurgitant orifices, the values for the PWS-derived regurgitant fraction were compared with measured regurgitant fraction. A fair correlation was demonstrated (r = 0.59), with low accuracy in prediction (error 44% +/- 24%). The PWS was inaccurate in predicting flow ratios in our in vitro system despite the strong relation with forward flow volume. The error incurred may be due to effects of filters that remove low velocity and low amplitude information.

Aortic Valve↗
PubMed1993

Doppler evaluation of femoral arteries in children after aortic balloon valvuloplasty or coarctation balloon angioplasty.

To assess long-term femoral artery complications after aortic balloon valvuloplasty or coarctation balloon angioplasty, we examined 19 children who were 3 weeks to 21 years old (mean 7.6 years) at the time of catheterization. Two-dimensional and Doppler echocardiographic examinations of the common, superficial, and deep femoral arteries were performed at an average of 2.0 years after balloon dilatation. Pulsatility index (PI) was calculated as the maximum velocity minus the minimum velocity divided by the mean velocity. No patient was suspected clinically of having peripheral arterial disease prior to the echocardiographic examination. Fourteen patients had normal femoral arteries. Of these, 10 had normal two-dimensional and Doppler echocardiographic examinations of both femoral arteries. These patients had triphasic flow patterns (forward in systole, reverse in early diastole, forward in middiastole) and Pls of 3.7-41.6 (mean 9.5). Four of the 14 normal patients had abnormal pulsed Doppler examinations showing continuous forward flow and low Pls (1.7-3.5) reflecting residual coarctation (10-30 mmHg gradients). Five patients had abnormal femoral arteries. Of these, two had no visible obstruction by two-dimensional echocardiography and color-flow imaging but had abnormal pulsed Doppler patterns (continuous forward flow and low Pls of 2.5 and 2.9) only on the side of the balloon catheter insertion. Three of the five abnormal patients had visible obstructions by two-dimensional echocardiography and color-flow imaging and had abnormal pulsed Doppler patterns (continuous forward flow and low Pls from 1.1-3.6).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1993

Echocardiographic guidance during placement of the buttoned double-disk device for atrial septal defect closure.

The usefulness of two-dimensional and Doppler echocardiography during buttoned double-disk device closure of an atrial septal defect was evaluated in 20 consecutive patients at the time of interventional catheterization. Transesophageal echocardiography was used in 11 patients (ages 5 to 62 years, weights 20 to 91 kg). Because of the size of the available transesophageal echo probe, transthoracic echocardiography was used in the remaining 9 patients (ages 4 to 5.5 years, weights 14 to 21 kg). In the transesophageal echo group, 1 patient was found to have no atrial septal defect despite a previous diagnosis by transthoracic echocardiography, 3 patients had atrial septal defects too large for closure despite attempts in 2, and 7 patients had transesophageal echo guided device placement. All of these 7 patients had small residual shunts by color Doppler, 2 had unusual arm positions, and 2 had surgical removal of the device due to embolization to the pulmonary artery in 1 and failure to obtain close approximation of the occluder and counteroccluder in 1. In the transthoracic echo group, 2 patients had atrial septal defects too large for closure, 1 patient had no femoral venous access, and 6 patients had transthoracic echo guided device placement. All of these 6 patients had small residual shunts by color Doppler and 3 of the 6 had unusual arm positions. For atrial septal defect sizing, transesophageal echo measurements correlated with catheter balloon size more closely than did transthoracic echo measurements (r 2 = 0.97 vs 0.86).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

The management of severe subaortic stenosis, ventricular septal defect, and aortic arch obstruction in the neonate.

Neonates with ventricular septal defect and aortic arch obstruction frequently have subaortic stenosis resulting from posterior deviation of the infundibular septum. Because the aortic anulus is often hypoplastic, making direct resection of the infundibular septum through the standard transaortic approach difficult, the optimal method of repair is uncertain. From September 1989 through November 1991, seven patients with ventricular septal defect, coarctation (n = 4), or interrupted aortic arch (n = 3) and severe subaortic stenosis underwent repair with use of a technique that included transatrial resection of the infundibular septum. Their ages ranged from 5 to 63 days (median 15 days) and weights from 1.3 to 5.4 kg (mean 3.1 kg). Only one patient was older than 1 month. The systolic and diastolic ratios of the diameter of the left ventricular outflow tract to that of the descending aorta were 0.53 +/- 0.09 mm (standard deviation) and 0.73 +/- 0.11, respectively. At operation, the posteriorly displaced infundibular septum was partially removed through a right atrial approach by resecting the superior margin of the ventricular septal defect up to the aortic anulus. The resulting enlarged ventricular septal defect was then closed with a patch to widen the subaortic area. In each patient the aortic arch was repaired by direct anastomosis. All patients survived operation; there was one late death from noncardiac causes 3 months after repair. The survivors remain well from 3 to 14 months after repair (mean 8 months). All are in sinus rhythm and none has a residual ventricular septal defect. One patient underwent successful balloon dilation of a residual aortic arch gradient late after repair. No patient has significant residual subaortic stenosis, although one has valvular aortic stenosis. This series suggests that in neonates with ventricular septal defect and severe subaortic stenosis resulting from posterior deviation of the infundibular septum, direct relief can be satisfactorily accomplished from a right atrial approach. This method provides effective widening of the left ventricular outflow tract and is superior to palliative techniques or conduit procedures.

Aortic Arch Syndromes↗
PubMed1993

Results of a policy of primary repair of truncus arteriosus in the neonate.

Although the early mortality for repair of truncus arteriosus has decreased in the modern era, routine correction in the neonate has not been widely adopted. To assess the results of our protocol of early repair, we reviewed 46 neonates and infants undergoing repair of truncus arteriosus at the University of Michigan Medical Center from January 1986 to January 1992. Their ages ranged from 1 day to 7 months (median 13 days) and weights from 1.8 kg to 5.4 kg (mean 3.1 kg). Repair was performed beyond the first month of life in only 8 patients, because of late referral in 7 and severe noncardiac problems in 1. Associated cardiac anomalies were frequently encountered, the most common being interrupted aortic arch (n = 5), nonconfluent pulmonary arteries (n = 4), hypoplastic pulmonary arteries (n = 4), and major coronary artery anomalies (n = 3). Truncal valve replacement was performed in 5 patients with severe regurgitation, 3 of whom also had truncal valve systolic pressure gradients of 30 mm Hg or more. The truncal valve was replaced with a mechanical prosthesis in 2 patients and with a cryopreserved homograft in 3 patients. Right ventricle-pulmonary artery continuity was established with a homograft in 41 patients (range 8 mm to 15 mm), a valved heterograft conduit in 4 (range 12 mm to 14 mm), and a nonvalved polytetrafluoroethylene tube in the remaining patient (8 mm). There were 5 hospital deaths (11%, 70% confidence limits 7% to 17%). Multivariate and univariate analyses failed to demonstrate a relationship between hospital mortality and age, weight, or associated cardiac anomalies. Only 1 death occurred among 9 patients with interrupted aortic arch or nonconfluent pulmonary arteries. Hospital survivors were followed-up from 3 months to 6.3 years (mean 3 +/- 0.4 years). Late noncardiac deaths occurred in 3 patients, all within 4 months after the operation. Actuarial survival was 81% +/- 6% at 90 days and beyond. Despite the prevalence of major associated conditions, early repair has resulted in excellent survival. We continue to recommend repair promptly after presentation, optimally within the first month of life.

Abnormalities, Multiple↗
PubMed1992

Echocardiographic evaluation of atrioventricular orifice anatomy in children with atrioventricular septal defect.

In atrioventricular (AV) septal defect, the common AV valve can have a common orifice or can be divided by bridging leaflet tissue into two separate orifices. To determine the accuracy of a two-dimensional echocardiographic technique devised specifically for evaluation of the number of AV valve orifices, all 69 children undergoing surgical repair of AV septal defect from April 1987 to August 1990 were examined prospectively. The presence of bridging leaflet tissue and the number of AV valve orifices were determined with use of a subcostal imaging plane. From a standard subcostal four-chamber view, the plane of sound was rotated 30 degrees to 45 degrees clockwise until the AV valve was seen en face. The plane of sound was then tilted from a superior to an inferior direction so that cross-sectional views of the AV valve were examined from the inferior margin of the atrial septum to the superior margin of the ventricular septum. Of the 69 patients, 6 (9%) were excluded because the appropriate subcostal images were not obtained (in 3 because of obesity and in 3 as a result of operator failure). The remaining 63 children, ranging in age from 1 day to 13.5 years and in weight from 1 to 55 kg, constituted the study group. Echocardiographic results were compared with surgical observations in 62 patients and with autopsy findings in 1 patient. With the two-dimensional echocardiographic technique, 32 of 33 patients with a common orifice and 28 of 30 patients with two separate AV valve orifices were correctly identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Echocardiographic assessment of subvalvular aortic stenosis before and after operation.

The development of two-dimensional and Doppler echocardiography has provided a noninvasive technique for the diagnosis and serial assessment of patients with subvalvular aortic stenosis. The clinical records and echocardiographic data were reviewed of all patients with subaortic stenosis diagnosed between 1983 and 1991. Of the 77 patients identified (45 male and 32 female), 28 had isolated subaortic stenosis and 49 had associated cardiac lesions. The most frequently encountered associated lesions were ventricular septal defect (n = 19) and coarctation of the aorta/interrupted aortic arch (n = 14). Serial echocardiographic studies, performed in 38 of the 77 patients, documented significant progression of the left ventricular outflow tract gradient in 25 patients (66%) and development of aortic regurgitation in 25 patients (66%). Surgical resection was performed in 36 patients. The preoperative outflow tract peak gradient was 62.9 +/- 31 mm Hg (range 0 to 153), whereas the immediate postoperative gradient was 14.4 +/- 14 mm Hg (range 0 to 67). The two patients with a significant residual gradient (37 and 67 mm Hg, respectively) in the immediate postoperative period had severe subaortic stenosis preoperatively with marked left ventricular hypertrophy and intracavitary gradient. The immediate postoperative echocardiograms demonstrated no worsening of aortic regurgitation in any patient and regression of regurgitation in one patient from mild to none. Intermediate-term follow-up studies were available for review in 13 postoperative patients at a mean of 4 years postoperatively. In 2(15%) of these 13 patients, subaortic stenosis recurred; however, the degree of aortic regurgitation did not increase in any patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗
PubMed1992

Intermediate-term survival and functional results after arterial repair for transposition of the great arteries.

An assessment of late morbidity and mortality is essential before arterial repair can be considered truly corrective for patients with transposition of the great arteries. We describe the early and intermediate-term results in 126 patients who underwent arterial repair. Operation was performed at a median age of 6 days, with 76 patients operated on within the first 7 days of life. Coronary artery anatomy differed from the usual arrangement in 37 patients. Simultaneous procedures included ventricular septal defect closure (35) and repair of interrupted aortic arch (2) or coarctation (5). Hospital mortality was seven of 126 (5.5%), with three deaths among the most recent 100 patients (3%). There were one late, noncardiac death and one late death after reoperation. Reoperation for pulmonary artery stenosis was required in 10 of the first 63 patients (16%), all of whom underwent pulmonary artery reconstruction with separate patches for closure of the coronary excision sites. Of the last 63 patients, all of whom underwent pulmonary artery reconstruction with a single pantaloon-shaped pericardial patch, one (2%) required reoperation for pulmonary artery stenosis. Doppler flow studies and echocardiography performed in 115 of 119 surviving patients at a mean of 12 months after repair demonstrated normal left ventricular function, minimal left ventricular outflow gradients, and no more than trivial aortic regurgitation. Peak gradient across the right ventricular outflow tract was 19 +/- 3 mm Hg in patients with separate pulmonary artery patches and 5 +/- 2 mm Hg in those with a single pantaloon patch (p = 0.0001). Follow-up is 96% complete from 1 month to 8 years after operation (mean 2.5 years). The actuarial survival rate at 5 years, including operative mortality, was 92%. All patients are in sinus rhythm, and none requires antiarrhythmic medications. These data suggest that pulmonary artery reconstruction with a single pantaloon patch may be associated with a decreased requirement for reoperation. Intermediate-term survival and functional results are excellent after arterial repair for transposition of the great arteries.

Actuarial Analysis↗
PubMed1991

Doppler evaluation of aortic valve area in children with aortic stenosis.

To evaluate the usefulness of the Doppler-derived aortic valve area calculated from the continuity equation in assessing the hemodynamic severity of aortic valve stenosis in infants and children, two-dimensional and Doppler echocardiographic examinations were performed on 42 patients (aged 1 day to 24 years) a median of 1 day before or after cardiac catheterization. The left ventricular outflow tract diameter was measured from the parasternal long-axis view at the base of the aortic cusps from inner edge to inner edge in early systole. The flow velocities proximal to the aortic valve were measured from the apical view with use of pulsed Doppler echocardiography; the jet velocities were recorded from the apical, right parasternal and suprasternal views by using continuous wave Doppler echocardiography. The velocity-time integral, mean velocity and peak velocity were measured by tracing the Doppler waveforms along their outermost margins. Seventeen patients (all less than or equal to 6 years old) had a very small left ventricular outflow tract diameter (less than or equal to 1.4 cm) and cross-sectional area (less than or equal to 1.5 cm2). The Doppler aortic valve area calculated with use of velocity-time integrals in the continuity equation (0.57 +/- 0.25 cm2/m2, mean value +/- SD) correlated well with the Doppler aortic valve area calculated by using mean (0.55 +/- 0.25 cm2/m2) and peak (0.54 +/- 0.24 cm2/m2) velocities, with correlations of r = 0.97 and 0.95, respectively. Thirty-four patients had sufficient catheterization data to calculate aortic valve area from the Gorlin formula.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Doppler assessment of pulmonary artery flow patterns and ventricular function after the Fontan operation.

To assess the relation between ventricular systolic and diastolic function and pulmonary artery (PA) flow patterns after the Fontan operation, 15 postoperative patients were prospectively evaluated with echocardiography. Blood flow velocities in the PA were recorded with pulsed Doppler echocardiography. Ejection fraction was measured by 2-dimensional echocardiography using Simpson's rule. Indexes of diastolic function were measured from the systemic atrioventricular valve inflow Doppler and included peak E and A velocities, peak filling rate normalized for stroke volume, the fractions of filling in early and late diastole (E and A area fractions), and the E/A velocity and area ratios. Compared with 15 age-matched control subjects, the 15 patients who had undergone the Fontan procedure had decreased peak E velocity (0.65 +/- 0.20 vs 0.87 +/- 0.10 m/s), decreased E/A velocity ratio (1.29 +/- 0.23 vs 1.98 +/- 0.46), decreased normalized peak filling rate (6.09 +/- 0.90 vs 6.81 +/- 0.83 s-1), decreased E area fraction (0.63 +/- 0.09 vs 0.72 +/- 0.07), increased A area fraction (0.37 +/- 0.07 vs 0.24 +/- 0.06), and decreased E/A area ratio (1.77 +/- 0.45 vs 3.33 +/- 1.15) (p less than 0.05). These diastolic filling abnormalities are consistent with impaired ventricular relaxation and decreased early diastolic transvalvular pressure gradient. PA Doppler recordings showed 2 distinct patterns of flow. Pattern I, observed in 9 patients, showed biphasic forward flow with peak velocities in mid to late systole and mid-diastole. Pattern II, observed in the remaining 6 patients, showed decreased systolic forward flow, a late systolic to early diastolic flow reversal, and delayed onset of diastolic forward flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Long-term assessment of right ventricular diastolic filling in patients with pulmonic valve stenosis successfully treated in childhood.

Patients with severe pulmonic stenosis (PS) have right ventricular (RV) diastolic filling abnormalities detectable by tricuspid valve pulsed Doppler examination. To determine if these abnormalities persist long term after successful therapy of PS, 19 patients were examined 8 +/- 3 years after PS therapy. At the time of follow-up Doppler examination, the PS gradient was 15 +/- 8 mm Hg. From the tricuspid valve inflow Doppler study, the following measurements were obtained at peak inspiration: peak velocities at rapid filling (peak E) and during atrial contraction (peak A), ratio of peak E to peak A velocities, RV peak filling rate normalized for stroke volume, deceleration time, the fraction of filling in the first 0.33 of diastole as well as under the E and A waves, and the ratio of E to A area. Data from PS follow-up patients were compared with our previously reported data from 12 age-related control subjects and 14 untreated patients with PS. Patients with PS who were followed up had higher peak E velocity (0.75 +/- 0.14 vs 0.59 +/- 0.21 m/s), lower peak A velocity (0.47 +/- 0.09 vs 0.64 +/- 0.28 m/s), higher E/A velocity ratio (1.65 +/- 0.33 vs 1.11 +/- 0.52), higher 0.33 area fraction (0.52 +/- 0.08 vs 0.34 +/- 0.14), lower A area fraction (0.29 +/- 0.06 vs 0.45 +/- 0.21) and higher E/A area ratio (2.48 +/- 0.82 vs 1.73 +/- 1.05) than PS patients without treatment (p less than 0.03). All Doppler indexes of the patients with PS who were followed up were the same as those of the control subjects except for the peak E velocity that was slightly higher (0.75 +/- 0.14 vs 0.63 +/- 0.11 m/s), the peak A velocity that was slightly higher (0.47 +/- 0.09 vs 0.38 +/- 0.09 m/s) and the E/A area ratio that was slightly lower (2.48 +/- 0.82 vs 3.50 +/- 1.25) (p less than 0.03). Thus, at long-term follow-up, all RV diastolic filling indexes in successfully treated patients with PS improved compared with the untreated patients and approached values found in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Left ventricular ejection fraction measured with Doppler color flow mapping techniques.

To determine if left ventricular (LV) ejection fraction (EF) can be accurately measured from the color Doppler examination, 11 patients (aged 0.4 to 22 years) underwent 2-dimensional and color Doppler examinations within 24 hours of cardiac catheterization. With use of a biplane Simpson's rule, LV end-diastolic volume, end-systolic volume and EF were measured from cineangiograms, 2-dimensional echocardiograms and color Doppler examinations. The 2-dimensional echocardiographic and color Doppler measurements were obtained from apical 4-chamber and long-axis views. The color Doppler examinations were performed by placing the color sector over the left ventricle only. The velocity scale was set at the lowest possible Nyquist limit (less than 0.17 m/s), and the highest possible carrier frequency was used to obtain this limit. With these settings, all flow signals in the LV chamber were aliased so that the entire chamber was filled with mosaic color Doppler signals. Motion of the surrounding LV walls gave rise to nonaliased (pure red-blue) signals. With use of an off-line analysis system equipped with a color frame grabber, the border of the mosaic color flow area was traced to obtain volumes and EF. End-diastolic and end-systolic volumes measured with color Doppler correlated well with those measured from 2-dimensional echocardiography (r = 0.99, standard error of the estimate [SEE] = 11.9 ml; r = 0.99, SEE = 4.4 ml, respectively) and cineangiography (r = 0.92, SEE = 16.8 ml; r = 0.90, SEE = 9.9 ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗