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Biomedical subjects

G W Henry

Publications and source records attributed to G W Henry.

At least 37 records · Page 2Linked to original sources
PubMed1987

Constant postoperative monitoring of cardiac output after correction of congenital heart defects.

A new method has been developed that permits constant postoperative monitoring of mean and phasic cardiac output in patients after correction of congenital heart defects. A miniature ultrasound probe is attached to the adventitia of the ascending aorta at the conclusion of the operative procedure. This is connected to the monitoring equipment by means of polyurethane-covered wires that exit the chest wall through a small stab wound. The probe can easily be removed by gentle traction when the patient's condition is stable. The technique was developed, validated, and refined in extensive animal studies, and this report describes the first series of 20 consecutive human implants, performed between August 1984 and September 1985, in which the absolute cardiac output determination obtained with the ultrasound probe at the time of its application was correlated with cardiac output as measured with a standard electromagnetic flow probe. Fourteen male and six female patients (mean age 5.5 years) were studied. Operations performed included eight atrial septal defect repairs, four procedures for tetralogy of Fallot, three ventricular septal defect repairs, three stenotic valve corrections, and two Senning operations. One operative death occurred, but no complications were related to probe application or removal. The average cardiac output in the 20 patients as measured with the ultrasound probe was 2.2 +/- 1.1 L/min (range 0.67 to 5.27 L/min). This is nearly identical to the results noted with the electromagnetic flow probe, where the mean cardiac output was 2.3 +/- 1.2 L/min (range 0.7 to 6 L/min). Regression analysis revealed a high linear correlation (r = 0.9) between the two techniques. A monitor can display the cardiac output trend with 1 minute updates, which greatly enhance management of intravenous drug therapy and volume administration. In conclusion, this new extraluminal removable probe allows virtually continuous monitoring of the postoperative cardiac output after correction of congenital heart defects and should become a standard technique in the postoperative care of these patients.

Adolescent↗
PubMed1986

Maturation of pulmonary input impedance spectrum in infants and children with ventricular septal defect.

To determine whether pulmonary vascular disease can be detected in infants with ventricular septal defect (VSD) by the presence of an increase in the frequency of the impedance modulus minimum of the pulmonary input impedance spectrum, as has been implied for older children, spectra of 25 infants (2 years or younger) (group 1) were compared with spectra of 20 children (ages 2 to 7 years) (group 2). Groups were subdivided according to mean pulmonary artery (PA) pressure: those with moderate pressure levels (35 mm Hg or less, groups 1A and 2A) and those with high pressure levels (at least 40 mm Hg, groups 1B and 2B). Pulmonary vascular resistance, characteristic impedance and frequency of the modulus minimum were significantly lower in group 2A than in group 1A. The decrease in pulmonary vascular resistance and characteristic impedance with increasing age was consistent with body surface area increases; however, the shift in frequency of the modulus minimum could be more easily related to a decrease in the pulse wave velocity than to a shift in the primary reflection site. Pulmonary vascular resistance, characteristic impedance and the frequency of the first modulus minimum were comparable in groups 1B and 2B; however, none of the patients in group 1B had evidence of pulmonary damage, whereas 3 of 4 group 2B patients had microscopically apparent pulmonary vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1986

Characteristics of blood flow velocity in the hypertensive canine pulmonary artery.

Pulmonary artery blood flow velocity was measured in 15 dogs by a recently developed direct intraluminal pulsed Doppler technique. Changes in velocity characteristics under conditions of experimentally induced hypoxic pulmonary hypertension were observed. Experimental conditions (fractional inspired oxygen concentration = 0.10) produced significant increases in mean pulmonary artery pressure and pulmonary vascular resistance. Overall and maximal negative velocity increased with pulmonary hypertension. Negative velocity occurred predominantly in the posterior half of the pulmonary artery during both control and experimental conditions. With pulmonary hypertension, diastolic negative velocity increased only in the posterior half of the pulmonary artery and systolic negative velocity decreased only in the anterior half. More basic knowledge of pulmonary artery blood flow characteristics may facilitate an informed approach to noninvasive detection of pulmonary hypertension. Direct measurements by this recently developed intraluminal technique will be useful in studying various conditions with altered pulmonary blood flow.

Animals↗
PubMed1985

Radionuclide diagnosis of infradiaphragmatic total anomalous pulmonary venous drainage.

We hypothesized that infradiaphagmatic total anomalous pulmonary venous drainage (ITAPVD), because of its unique physiology, could be diagnosed with radionuclide angiography. Seven neonates with severe respiratory distress were injected intravenously with 3 mCi technetium-99m pertechnetate. In each of four neonates demonstrated to have ITAPVD by pulmonary angiography, nuclide recirculation through the right atrium occurred 3-6 s after initial passage. In addition, direct visualization of the anomalous common pulmonary trunk with nuclide as a "tail" below the diaphragm was obvious in the third infant studied. This prompted review of the first two infants with ITAPVD; in retrospect the anomalous trunk was also visualized with nuclide in both of these infants. All three were injected via the upper extremity. In the fourth ITAPVD infant, nuclide was injected via the lower extremity. In that infant, preferential streaming of the inferior vena caval flow and nuclide across the foramen ovale into the left heart led to simultaneous opacification of anomalous trunk and descending aorta, obscuring the "tail" sign.

False Negative Reactions↗
PubMed1985

Changes in ventricular hemodynamics caused by a systemic-pulmonary shunt.

Systemic pulmonary shunts are both surgically created (Blalock-Taussig anastomosis) and obliterated (patent ductus arteriosus), but the effects of such a vascular communication on left ventricular hemodynamics have not been examined quantitatively. To study these effects, innominate arterial allografts were sutured between the descending thoracic aorta and the left main pulmonary artery in nine mongrel dogs. Left ventricular output (LVO) and shunt flow (SF) were monitored with electromagnetic flow probes while simultaneous phasic and mean pressures were recorded from the right atrium, aorta (AOP), and pulmonary artery. Data points (192) were analyzed while SF was varied between 0.02 and 5.5 liters/min using a variable-sized constricting band. Regression analysis showed increases (P less than 0.01) in LVO, stroke work (SW), and stroke volume (SV) in all dogs which were linearly related to SF (r = 0.64-0.99). Increasing SF was also associated with decreases (P less than 0.01, r = 0.61-0.99) in resistance (RES) facing the left ventricle and in diastolic (D) AOP. To compensate for differences in allograft size and to quantify the effects of a patent shunt, the regression equations were used to compare the percentage change in all parameters at SF = 0 and SF = 1.5 liters/min. Increases occurred in SV (46 +/- 21%), SW (32 +/- 14%), and LVO (48 +/- 21%), and decreases were present in DAOP (15 +/- 12%) and RES (32 +/- 13%). These data show that despite the decreases in pressure or the decreases in resistance facing the left ventricle in the presence of a systemic pulmonary shunt, a substantial increase in stroke work occurs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Radionuclide diagnosis of anomalous origin of the right pulmonary artery from the ascending aorta (so-called hemitruncus).

A 5-week-old infant presented with signs of severe congestive heart failure and pulmonary hypertension. Injection of technetium-99m pertechnetate demonstrated anomalous perfusion of the right lung. Subsequently, anomalous origin of the right pulmonary artery from the ascending aorta was proven at cardiac catheterization and repaired. Repeat injection of radionuclide 1 week postoperatively demonstrated normal flow to the right lung.

Aorta, Thoracic↗
PubMed1985

Cardiovascular effects of positive end-expiratory pressure (PEEP) after pneumonectomy in dogs.

Little is known regarding the hemodynamic effect of positive end-expiratory pressure (PEEP) following pneumonectomy. To investigate this, 9 mongrel dogs underwent PEEP before and after lung resection. With the chest closed, the dog anesthetized, and partial pressure of carbon dioxide constant, PEEP was added in increments of 2 mm Hg until the animal's condition became hemodynamically unstable. At each level of PEEP, aortic, pulmonary, left atrial, and central venous pressures were monitored while aortic flow (cardiac output) was determined with an electromagnetic probe and airway pressure was measured with a Millar catheter in the respiratory tubing. Pneumonectomy was then performed, PEEP was again sequentially added, and the same measurements were recorded. Both before and after pneumonectomy, a strong positive linear correlation exists between the level of PEEP and pulmonary vascular resistance (PVR) (r greater than 0.74; p less than 0.05). Also, there is a high negative linear correlation between the level of PEEP and cardiac output (r greater than -0.76; p less than 0.05). At 0 mm Hg of PEEP, the PVR is higher after pneumonectomy than before (p less than 0.02). The incremental elevation in PVR persists after pneumonectomy at each level of PEEP, and in 5 of the 9 dogs the slope of the linear regression line relating PVR to PEEP was steeper following resection (p less than 0.05), thereby demonstrating an exaggerated effect of PEEP on PVR. In addition, all animals had a lower cardiac output at each comparable level of PEEP following pneumonectomy (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Childhood traumatic infarction causing left ventricular aneurysm: diagnosis by two-dimensional echocardiography.

After being struck by an automobile, a 9 year old boy developed transient right bundle branch block followed by electrocardiographic changes of inferior wall myocardial infarction and an increase of serum cardiac enzymes. Two-dimensional echocardiography demonstrated a prominent septal aneurysm. Subsequent cardiac catheterization confirmed septal aneurysm and demonstrated an additional inferior aneurysm. Six weeks after the accident, resection of the inferior aneurysm was performed. At 1 year follow-up study, residual septal aneurysm and cardiomegaly are present, but the boy is asymptomatic.

Bundle-Branch Block↗
PubMed1985

Two-dimensional in vivo pressure/diameter relationships in the canine main pulmonary artery.

Ultrasonic measurement of blood flow within the main pulmonary artery (MPA) requires a precise knowledge of the mean blood velocity within this vessel and the cross-sectional area (CSA). Small conformational changes in the elliptical shape of the MPA have substantial effects on the calculation of CSA and, subsequently, flow. We examined the extent of these changes by measuring the pulsatile and mean elliptical dimensions of the MPA in nine anaesthetised, open-chested, mechanically ventilated mongrel dogs using two pairs of 10 MHz ultrasonic, piezoelectric crystals. These custom-made devices were sutured to the PA adventitia along the long and short cross-sectional axes 2 cm distal to the pulmonary valve. Axial dimensions were collected during normal, elevated (via noradrenaline and fluid additions) and reduced (via exsanguination) PA pressures. We confirmed the linear pressure/diameter response in 15/18 axial data sets (r greater than 0.80). Further, the linear axial responses of the long and short diameters were parallel (7/9, p less than 0.05) and have different zero-pressure intercepts (7/9, p less than 0.0001). A mathematical consequence of this parallelism is predictable, although non-constant, eccentricity. Finally, error analysis of multi-axial measurement techniques were shown to improve CSA accuracy by as much as 50% when compared with uni-axial determinations.

Animals↗
PubMed1985

Ultrasound detection and quantitation of left to right aortopulmonary shunt flow in a canine model.

To test the sensitivity and accuracy of pulsed Doppler ultrasonography to detect and quantitate left to right aortopulmonary shunt flow, an arterial allograft aortopulmonary anastomosis was constructed in nine adult mongrel dogs. Cardiac output and allograft flow were measured as the diameter of the allograft was varied. Piezoelectric crystals attached to the carotid artery and proximal descending aorta were energized with 20 MHz pulsed Doppler signals. Negative Doppler shift and negative Doppler shift/positive Doppler shift were calculated for seven dogs. All dogs exhibited negative Doppler shift in the carotid artery at zero allograft flow; five of the seven dogs exhibited a similar pattern in the descending aorta. Increasing negative Doppler shift was measured in all dogs from both sites as the allograft flow increased. Excellent linear correlation existed between allograft flow and negative Doppler shift and negative Doppler shift/positive Doppler shift for each dog from both sampling sites. However, marked interanimal variation in the slopes of the linear regression lines existed, making the composite linear correlation very poor. Detection of small left to right aortopulmonary shunting and single measurements to quantitate accurately left to right aortopulmonary shunting introduce errors due to intersubject variation. However, these results suggest that serial ultrasound measurements made over a short time can accurately predict changes in left to right aortopulmonary shunting.

Animals↗
PubMed1984

Infradiaphragmatic total anomalous pulmonary venous drainage: new diagnostic, physiologic, and surgical considerations.

Numerous diagnostic pitfalls were noted among 6 infants with infradiaphragmatic total anomalous pulmonary venous drainage, including prolonged moderate respiratory distress in 2 infants, normal cardiac examination in 2, normal electrocardiograms in 2, arterial PO2 in excess of 100 torr in 3 cases, right radial/umbilical arterial PO2 gradients consistent with significant right-to-left ductal shunting in 2 of 4 cases, misleading M-mode echocardiography in 2 of 4 cases, and missed diagnosis at initial cardiac catheterization despite pulmonary angiography in 1 case. Helpful radiographic features included small heart, congested lungs, and pleural effusions in all 6 cases, and visualization of the anomalous trunk overlying the liver on slightly rotated abdominal flat plates in both cases so examined. Bedside umbilical venous catheterization was pathognomonic in 3 cases and suggestive of the diagnosis in the fourth case. Cross-sectional echocardiography was diagnostic in the 1 case in which it was employed. Intraoperative and postoperative pulmonary hypertension led to the demise of the 4 infants who survived long enough to undergo surgery. In addition to early diagnosis, measures to insure maximal decompression of the pulmonary circuit at surgery should improve survival.

Cardiac Catheterization↗
PubMed1984

Cerebral arteriovenous malformation presenting as persistent fetal circulation. Diagnosis by cross-sectional echo.

Two infants with cerebral arteriovenous malformation (CAVM), both initially seen with persistent fetal circulation, were studied with cross-sectional echo. The descending aorta, which is dilated in infants with CAVM, was identified in the subxiphoid four-chamber and short-axis views in both infants. In both infants the arteriovenous malformation was readily identified by cross-sectional echo as a lucency within the brain. Pulsation of the cranial lucency was noted in one infant, but only still frames from the head echo were preserved in the other infant, and pulsation was not commented on in that case.

Diagnosis, Differential↗
PubMed1984

Velocity profile in the main pulmonary artery in a canine model.

The velocity profile of the main pulmonary artery was determined in nine adult, open-chested, mechanically ventilated mongrel dogs using an intraluminal, needle-mounted, range-gated, pulsed Doppler technique. Mean phasic point velocities were determined at 2 mm intervals across the lumen of the vessel, 2 cm above the pulmonary valve, by recording the Doppler shift of an activated 20 MHz piezoelectric crystal, range-gated 3.5 mm in the direction of the pulmonary valve. Mean Reynolds numbers from the main pulmonary artery ranged from 275 to 1140. Radially normalised intraluminal distance versus mean phasic point velocity plots were constructed which demonstrated a curved profile in all 9 dogs. First order regression analysis demonstrated a poor fit (r: 0.05-0.68). Second order (r:0.61-0.97) and third order (r:0.72-0.99) regression analyses markedly improved the fit, confirming the non-linear nature of the velocity profile. Step-wise third order regression analysis to determine the importance of the entry sequence demonstrated that the most important term for determining the regression coefficient was the X2 term in six dogs. In addition, the velocity profile was noted to be shifted, with the highest velocities recorded between the centre of the vessel and the anterior wall in eight of nine dogs (location of highest velocity: +0.26 radius +/- 0.25 (mean +/- SD).

Animals↗
PubMed1984

The velocity profile in the canine ascending aorta and its effects on the accuracy of pulsed Doppler determinations of mean blood velocity.

The velocity profile in the ascending aorta, which has been variously reported as parabolic, skewed or flat, was measured using an intraluminal probe equipped with a miniature piezoelectric crystal activated by a 20 MHz pulsed Doppler with a 1 mm3 sample volume size. Phasic velocities, determined via spectral analyses, were obtained at 2 mm intervals across the aortic lumen of anaesthetised open-chest dogs by sequentially moving the crystal between posterior and anterior walls, maintaining the ultrasound beam parallel to the flow axis. Range-gating allowed data acquisition 3.5 mm proximal to the crystal, thus eliminating probe induced turbulence. Time and spatial distributions of velocities over the cross-section were computed. Expected errors in vessel mean velocity estimates based on point measurements were calculated. Analysis of phasic waveforms showed increased posterior velocities during systole but third order regression analysis of normalised point mean velocities across the lumen showed the best fit was a statistically flat straight line. Centreline referenced analyses indicated the expected difference between point mean velocity and vessel mean velocity was maximal (19.3 +/- 10.1%) 4 mm toward the posterior wall and minimal (4.7 +/- 9.1%) 5 mm toward the anterior wall. Anterior posterior wall referenced analyses indicated the most reliable position for estimating vessel mean velocity from point mean velocity along this axis was 5 mm from the anterior wall.

Animals↗
PubMed1983

The transmitral approach to left ventricular outflow tract obstruction.

Left ventricular outflow tract obstruction is a particularly vexing problem in patients with complete transposition (atrioventricular concordance and ventriculoarterial discordance) and intact ventricular septum. Previous techniques, such as resecting the obstructive lesion through the pulmonary valve or bypassing the obstruction, have not given entirely satisfactory results. An alternative approach of resection through the left atrium and the retracted mitral valve has recently been proposed. We have used this new technique to achieve excellent relief of this condition in three patients with different types of obstruction.

Cardiomyopathy, Hypertrophic↗