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Biomedical subjects

J E Lock

Publications and source records attributed to J E Lock.

At least 145 records · Page 8Linked to original sources
PubMed1986

Percutaneous balloon valvotomy of congenital pulmonary stenosis using oversized balloons.

Percutaneous balloon valvotomy was attempted in 27 patients (aged 6 days to 19 years, median 2 years, 11 months) with unoperated typical valvular pulmonary stenosis using a balloon 7 to 60% (mean 30%) larger than the valve anulus. One patient had undergone a previous balloon valvotomy elsewhere. To achieve an oversized dilation diameter in three larger patients, two balloons were inflated side by side. Their "effective dilation diameter" was determined by the diameter of the circle with the same area as that of the oval enveloping the two balloons. A significant reduction of the transvalvular gradient occurred in all patients (mean +/- SD = 74.3 +/- 14.7%, range 33 to 100%). The average gradient of 65.0 +/- 19.0 mm Hg (mean +/- SD) fell to 15.9 +/- 7.6 mm Hg (0 to 30 mm Hg). Twenty-five of 27 patients had a residual transvalvular gradient of less than 25 mm Hg. The calculated valve orifice area increased by an average of 183 +/- 80%. No significant complications occurred. It is concluded that percutaneous balloon valvotomy with a balloon 20 to 40% larger than the valve anulus is the treatment of choice for typical congenital valvular pulmonary stenosis.

Adolescent↗
PubMed1986

Effects of static and fluctuating airway pressure on intact pulmonary circulation.

The direct effects on the pulmonary circulation of static and fluctuation airway pressure were compared in intact close-chest infant lambs with reactive pulmonary vasculature under alpha-chloralose anesthesia. A preparation developed to permit independent ventilation of right and left lungs and independent measurement of right and left lung blood flow was employed to separate direct from indirect effects of unilateral airway pressure changes on pulmonary vascular resistance (PVR). Both static and fluctuating unilateral airway pressure interventions directly elevated ipsilateral PVR. For purposes of comparison mean alveolar pressure (PA) was estimated for both static and fluctuating trials. Fluctuating interventions increased PVR more than did static trials at comparable levels of PA. Substantially less PA was needed to double ipsilateral PVR by fluctuating than by static interventions (16 vs. 26 mmHg, respectively). These data indicate that, in the intact animal with reactive pulmonary vasculature, both PA and the waveform of airway pressure applied can influence PVR.

Animals↗
PubMed1986

Balloon dilatation of calcific aortic stenosis in elderly patients: postmortem, intraoperative, and percutaneous valvuloplasty studies.

To assess the safety and efficacy of percutaneous balloon valvuloplasty in calcific aortic stenosis, balloon dilatation of critically stenosed, calcified aortic valves was performed in five postmortem hearts, in five patients intraoperatively before aortic valve replacement, and in two elderly patients percutaneously at the time of diagnostic catheterization. The etiology of aortic stenosis in the 12 cases was rheumatic in two, congenital bicuspid calcific stenosis in one, and senile calcific degenerative stenosis in the remaining nine. Prevalvuloplasty examination in the 10 postmortem and intraoperative cases revealed rigid valve leaflets with commissural fusion in three valves and extensive nodular calcification in seven. Subsequent balloon dilatation with 15 to 18 mm valvuloplasty balloons resulted in decreased cusp rigidity and increased mobility of valve leaflets in all cases, without evidence of tearing of valve leaflets, disruption of the valvular ring, or liberation of calcific or valvular debris. In the three valve specimens with commissural fusion, balloon dilatation resulted in partial or complete separation of leaflets along fused commissures. In two cases with extensive nodular calcification, balloon dilatation resulted in a fracture of a calcified leaflet that was evident on both gross and radiologic examination. After postmortem and intraoperative studies, percutaneous catheter valvuloplasty was performed at the time of diagnostic catheterization in two elderly patients (93- and 85-year-old women) with long-standing calcific aortic stenosis. Balloon dilatation with 12 to 18 mm balloons resulted in significant decreases in aortic gradients and significant increases in cardiac index and aortic valve area in both patients. Percutaneous valvuloplasty in both patients resulted in a mild increase in aortic insufficiency and no evidence of embolic phenomena.

Aged↗
PubMed1985

Percutaneous catheter commissurotomy in rheumatic mitral stenosis.

We attempted percutaneous transcatheter-balloon mitral commissurotomy in eight children and young adults (9 to 23 years of age) with rheumatic mitral stenosis. The atrial septum was traversed by needle puncture, and an 8-mm angioplasty balloon was advanced over a guide wire. The atrial septal perforation was then dilated to allow passage of the valvuloplasty balloon catheter (18 to 25 mm) across the mitral annulus. Inflation of the transmitral balloon decreased the end-diastolic transmitral gradient temporarily in all patients (from 21.2 +/- 4.0 mm Hg [mean +/- S.D.] to 10.1 +/- 5.5 mm Hg; P less than 0.001). The immediate decrease in the gradient was associated with increases in cardiac output (from 3.8 +/- 1.0 to 4.9 +/- 1.3 liters per minute per square meter of body-surface area; P less than 0.01) and in the calculated mitral-valve-area index (from 0.73 +/- 0.29 to 1.34 +/- 0.32 cm2 per square meter; P less than 0.001). Murmur intensity diminished immediately after commissurotomy in all patients. The greatest reduction in pressure gradient (76 to 95 per cent) occurred when the largest balloon (inflated diameter, 25 mm) was used in the smallest patients (0.9 to 1.2 m2). The balloon commissurotomy produced minimal mitral regurgitation in only one child. Follow-up catheterization (at two to eight weeks) demonstrated persistence of hemodynamic improvement with evidence of partial restenosis in one patient. These early results indicate that balloon mitral commissurotomy can be a safe and effective treatment for children and young adults with rheumatic mitral stenosis.

Adolescent↗
PubMed1985

Transcatheter closure of patent ductus arteriosus in piglets.

To better determine the risks of transcatheter closure of a patent ductus arteriosus (PDA), a model of PDA was made in newborn piglets by using 5- to 7-mm angioplasty catheters to dilate the probe PDA. This maneuver resulted in a permanent PDA in most piglets. Four to 6 weeks later PDA closure was attempted using the Rashkind PDA occluder. Twelve such procedures were attempted, using clean but nonsterile technique. Nine of 12 PDAs were successfully closed. Two failures were the result of inability to successfully traverse the PDA. This problem was solved by using a long sheath to position the device properly. Four complications occurred, all related to device release: left pulmonary artery embolization in 1 case, femoral artery embolization in 1, torn pulmonic valve cusp in 1 and lodgment of a prosthesis on a pulmonic valve cusp. Two successfully implanted devices were infected at necropsy. This study demonstrates the value of a piglet model in testing transcatheter PDA occlusion devices, the importance of sterile technique in such procedures, the hazards of device retrieval through the right heart and the feasibility of transcatheter PDA closure.

Angioplasty, Balloon↗
PubMed1985

Morphologic changes induced by dilation of the pulmonary valve anulus with overlarge balloons in normal newborn lambs.

The optimal method for balloon dilation valvuloplasty of congenital pulmonary valve stenosis has not been established. The cardiac damage produced by using a balloon the same size as the pulmonary anulus has not been described. The use of balloons that are larger than the anulus or of a dynamic dilation technique may enhance gradient reduction, but their added risks are not known. The pulmonary valve anuli of 14 normal newborn lambs were dilated with angioplasty balloons 20% smaller to 90% larger than the anulus; in 3 dilations, a dynamic technique was used, consisting of withdrawal of the fully inflated balloon from the anulus into the body of the right ventricle. Twelve lambs were killed immediately after the procedure and 2 were killed later, and detailed gross anatomic and microscopic observations of the heart were made. These observations support the following conclusions: (1) Dilation of the pulmonary valve anulus with overlarge balloons is "clinically" well tolerated in normal newborn lambs. (2) The major damage to the heart from any balloon is not the pulmonary anulus, but to the right ventricular outflow tract and free wall, with mural hemorrhages of varying size. (3) Trauma is minor if the balloon is 30% larger than the anulus, but is considerable when the balloon is 50% larger; (4) Trauma is worst subjacent to the proximal end of the balloon, so that longer balloons may cause greater damage; and (5) Resolution of acute right ventricular hemorrhage occurs with small, patchy areas of fibrosis.

Angioplasty, Balloon↗
PubMed1985

Therapeutic catheter procedures in pediatrics.

There is a large spectrum of interventional catheter procedures being performed presently in children. The procedures that offer a greater advantage than surgical techniques and that will continue to be established procedures include percutaneous angioplasty of the pulmonary valve, peripheral pulmonary artery and caval stenosis, embolizations of pulmonary collaterals and pulmonary arteriovenous malformations, angioplasty of vascular access shunt, embolization of bronchial arteries for hemoptysis, and percutaneous nephrostomy and abscess drainage procedures. Others that have been successful but not yet routinely established in children include thrombolysis, renal artery angioplasty, embolization of peripheral arteriovenous malformations, dilatation of the urinary and gastrointestinal tract stenosis, and percutaneous biopsy.

Angioplasty, Balloon↗
PubMed1985

Pulmonary and systemic vascular effects of SRS-A blockade in conscious lambs.

There is preliminary evidence suggesting that hypoxic pulmonary vasoconstriction may be mediated by slow-reacting substance of anaphylaxis (SRS-A), which is comprised of leukotrienes C4, D4, and E4. We studied the effects of the SRS-A antagonist FPL 57231 (FPL) on the hypoxic pulmonary vasoconstrictor response and on systemic vascular resistance in awake, chronically instrumented young lambs. Two other studies were performed to ascertain whether FPL's vasodilation was specific for hypoxic pulmonary vasoconstriction: the effect of FPL infusion in pulmonary and systemic vascular resistance was measured in six normoxic lambs, and the effect of FPL on 5-hydroxytryptamine (5-HT)-mediated vasoconstriction was determined. In seven lambs, mean pulmonary arterial pressure was 21 mmHg in room air and 28 mmHg in hypoxia (Po2 = 43 Torr). During hypoxia, FPL infusion (2 mg X kg-1 X min-1) reversibly decreased pulmonary arterial pressure to 15 mmHg; pulmonary arteriolar resistance also fell below normoxia levels with FPL. FPL also caused a fall in aortic pressure and systemic vascular resistance in these hypoxic lambs, but the decrease in systemic resistance was less than the fall in pulmonary resistance. beta-Adrenergic blockade using propranolol (1 mg/kg) did not affect the pulmonary vasodilation caused by FPL. In six normoxic lambs, FPL infusion also significantly decreased pulmonary and systemic vascular resistance (29% in each case). These data are consistent with the idea that leukotrienes may be involved in adjusting both pulmonary and systemic vascular tone, but further work is necessary to establish whether FPL's vasodilation is mediated via its leukotriene antagonism or is a nonspecific effect of FPL.

Adrenergic beta-Antagonists↗
PubMed1985

Morphologic changes in the pulmonary arteries after percutaneous balloon angioplasty for pulmonary arterial stenosis.

The pathologic appearance of pulmonary arteries subjected to balloon dilation was studied in four subjects with stenosis of pulmonary arteries. Nine vessels were dilated. Successful dilation in seven vessels was accompanied by intimal disruption and tearing of the media. In one vessel, at the site of a previous surgical procedure, dilation could not be accomplished. Histologically, this vessel was encased by reactive fibrous tissue, which may have precluded successful dilation. In one case, simultaneous rupture of the dilating balloon and the left pulmonary artery occurred. Morphologic examination could not adequately explain the cause of vessel rupture. Among the six vessels successfully dilated and studied 4 to 14 months after the dilation, the postdilation luminal diamter had been maintained. Tears in the intima and media as seen histologically had been filled in by scar tissue. In one artery a dilated segment distal to a residual obstruction revealed marked intimal proliferation.

Angioplasty, Balloon↗
PubMed1985

Management of congenital stenosis of a branch pulmonary artery with balloon dilation angioplasty. Report of 52 procedures.

Twenty-four children, aged 4 months to 16 years (nine patients 2 years old or younger), underwent balloon dilation angioplasty of hypoplastic or stenotic branch pulmonary arteries between July, 1981, and April, 1984. Most children had tetralogy of Fallot, with or without pulmonary atresia, or isolated peripheral pulmonary artery stenosis. Fifty-two dilations were attempted, 44 in the catheterization laboratory and eight in the operating room. Of these, 26 (50%) were judged successful; the average vessel diameter on angiogram increased from 4.1 +/- 0.3 to 7.2 +/- 0.3 mm (76%), the gradient across the narrowed segment fell from 60 +/- 10 to 36 +/- 5 mm (40%), pressure in the main pulmonary artery or right ventricle proximal to the obstruction decreased from 83 +/- 10 to 66 +/- 6 mm Hg (20%), and the radionuclide-determined fraction of cardiac output directed to the lung ipsilateral to the dilated pulmonary artery increased from 40 +/- 4 to 51 +/- 4 (28%). All changes were significant at the p less than 0.005 level. Reasons for failure included inadequate technique (balloon too small, inability to position balloon or wire) in 14 and the refractory nature of the lesion itself in 11. Technical failures were age independent. Nondilatable lesions were more common in children more than 2 years old (10/25 versus 1/10) or with isolated peripheral pulmonary artery stenosis (5/7). Five of seven stenoses near previous shunts were nondilatable. One child exsanguinated when the pulmonary artery ruptured during dilation, but other complications were few. Eight dilations, followed up for an average of 6 months after dilation, showed angiographic persistence of improvement; two of four lesions were successfully redilated to a larger size. Balloon dilation angioplasty appears beneficial, both short and long term, for some patients with hypoplastic or stenotic branch pulmonary arteries, especially if performed early in life.

Adolescent↗
PubMed1984

Chronic percutaneous pericardial drainage with modified pigtail catheters in children.

To determine the safety and efficacy of chronic percutaneous pericardial drainage in children, pigtail catheters were inserted over curved guidewires under fluoroscopic control into the pericardial space in 7 consecutive children with pericardial effusion. Pericardiocentesis was therapeutic (for tamponade) in 1 child, diagnostic in 4 and both therapeutic and diagnostic in 2. The children were 0.5 to 16 years old and weighed 5 to 65 kg. Underlying diagnoses included cancer (3 children), congenital heart disease (2 children) and immunodeficiency and hemolytic uremic syndrome (1 each). When unmodified pigtail catheters, designed for angiography, were used (as in the first 3 children), either the catheters clotted within 36 hours, necessitating operative pericardial drainage, or repeated heparin infusions were required to keep the catheter patent. However, when 8Fr catheters were modified by placing 0.050-inch side holes along the distal shaft, the catheters remained patent and effectively drained the pericardial space for 3 to 7 days. Heparin infusion was not required, no child managed with the modified catheters required subsequent drainage and no complications occurred. In conclusion, percutaneous pericardial drainage is safe, even in small children, and can be effective chronically if catheters with large drainage holes are used.

Adolescent↗
PubMed1984

Complications of vascular catheterization in critically ill children.

Invasive hemodynamic monitoring is widely used in the care of critically ill children. In a prospective study, a total of 330 arterial catheters, 397 central venous catheters, and 47 pulmonary artery catheters were placed in 467 children, between February 1981 and September 1982. Complications observed included: bleeding in seven of 774 vascular catheterizations, arterial obstruction in three of 377 arterial catheterizations, and sepsis in 11 of 774 vascular catheterizations. Of the 21 complications noted, 71% occurred in children less than 5 yr of age. A total of 19 (4.1%) children suffered complications of bleeding, arterial obstruction, and/or sepsis. In contrast, the overall mortality in this group of patients was 16%. The risk of morbidity from vascular catheterization appeared justified in this group of critically ill children.

Adolescent↗
PubMed1984

Pulmonary vascular effects of vasoactive intestinal peptide in conscious newborn lambs.

Vasoactive intestinal peptide (VIP) may be a neurotransmitter in a peptidergic nervous system and is found in nerves in pulmonary blood vessels. Information regarding its pulmonary vascular effects is limited. We therefore studied VIP's effect on pulmonary vascular tone in the immature lung. Normoxic and hypoxic unsedated newborn lambs with chronically implanted flow probes around the right and left pulmonary arteries were used. VIP was injected into one pulmonary artery only, and direct effects of this peptide on the pulmonary vessels were determined by comparing the flow changes in the injected vs. the uninjected lung. VIP was a powerful pulmonary vasodilator with a threshold of 0.3 microgram/kg. It also was a systemic vasodilator (after 1 microgram/kg, aortic pressure fell 27% and cardiac output increased 29%, both P less than 0.01), with a threshold of 0.1 microgram/kg. Pretreatment with propranolol (1 mg/kg iv) did not abolish pulmonary or systemic vasodilation after VIP. On the other hand, pretreatment with indomethacin (3 mg/kg per day for 3 days) abolished VIP-induced pulmonary vasodilation but probably did not affect systemic vasodilation. We conclude that VIP is a powerful pulmonary vasodilator in the newborn lamb and that this dilation can be blocked by the cyclooxygenase inhibitor indomethacin. VIP is also a powerful systemic vasodilator in the newborn lamb but this effect is not blocked by either propranolol or indomethacin.

Animals↗
PubMed1984

Cardiopulmonary effects of unilateral airway pressure changes in intact infant lambs.

Direct effects of airway pressure changes on the pulmonary vascular bed of the intact infant lamb were studied under chloralose anesthesia using a preparation developed to permit independent ventilation of right and left lungs and independent measurement of right and left lung blood flow. A specially designed endobronchial tube eliminated the need for thoracotomy the day of study. Unilateral changes in positive end-expiratory pressure (PEEP) during volume-regulated ventilation increased ipsilateral but not contralateral airway pressure, confirming adequate separation of right and left lungs and suggesting rigidity of the mediastinum. Such interventions ( UPEEP ) at levels of 5, 10, and 15 cmH2O reduced ipsilateral but not contralateral pulmonary blood flow (by 10, 25, and 46%, respectively) but did not alter end-tidal PCO2 of either lung. UPEEP had less effect on cardiac output, stroke volume, right atrial, left atrial, esophageal, and pulmonary arterial pressures than did PEEP applied to both lungs. Because this preparation separates the predominantly direct effects of UPEEP on the ipsilateral lung from its indirect effects on the contralateral lung, it is well suited to studies of direct pulmonary vascular effects of airway pressure changes in an intact closed-chest preparation with reactive pulmonary vasculature.

Airway Resistance↗
PubMed1984

Distribution and quantitative developmental changes in guinea pig pulmonary beta-receptors.

Studies using tissue homogenates have demonstrated an increase in pulmonary beta-receptors during development. However, techniques using disrupted tissue have not permitted the precise anatomic localization of pulmonary beta-receptors or identification of structures where increases occur. Using L-[3H]dihydroalprenolol, beta-receptors were radioautographically localized and quantitated in sections of newborn (NB) and adult (A) guinea pig lung. Scatchard analysis showed a single class of binding sites with a maximum binding capacity of 189 +/- 3 (NB) and 305 +/- 37 (A) fmol X mg-1 protein (P less than 0.02). Binding was of high affinity with the dissociation constant (Kd) = 1.46 +/- 0.2 (NB) and 1.26 +/- 0.3 (A) nM (NS). The majority of beta-receptors were localized in alveolar wall and airway epithelia (alveolar much greater than bronchiolar greater than bronchial) (P less than 0.0001). Airway and vascular smooth muscle had significantly fewer demonstrable beta-receptors. The increased number of beta-receptors in the adult appeared to be due primarily to a 2.0 +/- 0.12-fold increase in alveolar wall and airway epithelia as opposed to only a 1.3 +/- 0.18-fold increase in the already low number in airway and vascular smooth muscle (P less than 0.05). While apparent receptor density may not necessarily correlate with physiological response or importance, radioautographic localization of pulmonary beta-receptors may significantly enhance our understanding of their role in normal and pathologic states.

Aging↗
PubMed1984

Coil embolization of congenital thoracic vascular anomalies in infants and children.

When significant thoracic vascular anomalies occur in children, they may present surgical difficulties making operative management undesirable. The recent development of a new, accurate coil-delivery system has enabled us to embolize 17 vessels in five children by passing Gianturco steel coils coated with thrombogenic Dacron strands through No. 5 or 6F end-hole catheters suitable for infants. Coils of 0.038 inch packed diameter were fed through the catheter lumen by a flexible guidewire emerging as 3, 5, or 8 mm diameter loose coils. Fifteen of 17 vessels were successfully occluded. No complications or errors in placement of coils occurred. Four of five children clearly benefitted from the procedure. One died in spite of partial occlusion. Coil embolization can be performed accurately and safely even in small infants with a high rate of successful occlusion and may prove to be a valuable adjunct to operative management.

Aorta↗