Biomedical subjects
Publications and source records attributed to D R Clarke.
Ventricular fibrillation during sternal reentry can be a fatal complication that is vexing to manage when it occurs before complete exposure of the heart. A technique of intraabdominal paddle placement for internal countershock has been used to successfully manage this complication.
Thirty-one children with postoperative coarctation of the aorta underwent maximal graded bicycle ergometry using an electronically braked ergometer and the James protocol; 18 also underwent expiratory gas measurement using a mass spectrometer. Twenty-two age- and gender-matched normal subjects were used as a control group. The mean age at operation was 41 months and the mean age at evaluation was 134 months (mean follow-up interval 93 months). The original surgical repair was subclavian flap repair in 8 patients, end to end anastomosis in 21, patch aortoplasty in 1 patient and tubular graft in 1. Patients exercised until exhaustion and maximal exercise variables were obtained. The maximal voluntary peak heart rate was 183 beats/min (94.6% of predicted value), indicating excellent effort. Mean power was 111% of predicted value and, when measured, maximal oxygen consumption was 89% of predicted value with an anaerobic threshold at 63 +/- 3.5% of exercise time. The observed work variables were not different from values in the control group and were not affected by the type of repair. The mean peak systolic blood pressure was 152 +/- 7.6 mm Hg versus 147 +/- 5.7 mm Hg in the control group (p = NS). Patients who had associated intracardiac lesions had significantly lower maximal oxygen consumption (85 +/- 3% vs. 98 +/- 4% of predicted value). The results suggest that adequate cardiopulmonary function, normal or above average work capacity and normal exercise systolic blood pressure can be obtained in children with satisfactory repair of coarctation of the aorta performed before school age.
The metabolic basis for the enhanced tolerance of immature hearts to ischemia remains to be elucidated. Loss of high-energy phosphate nucleotides occurs during ischemia/reperfusion in mature (adult) hearts through the breakdown of adenosine triphosphate, diphosphate, and monophosphate (nondiffusible) to adenosine (freely diffusible). However, previous work has shown that after ischemia nondiffusible nucleotides are better retained by immature (neonatal) hearts than by mature hearts. The enzyme responsible for the conversion of adenosine monophosphate to adenosine is 5'-nucleotidase. We therefore hypothesized lower activity of this enzyme in neonatal than in adult myocardium. The purposes of this study were (1) to document 5'-nucleotidase activities in neonatal and adult rabbit myocardium and (2) to correlate differences of 5'-nucleotidase activity with functional recovery from ischemia. Neonatal (5- to 10-day-old) and adult (4- to 6-month-old) rabbit hearts were isolated and perfused (retrograde Langendorff). A left ventricular balloon measured functional parameters. Hearts were subjected to 20 minutes of global 37 degrees C ischemia and 10 minutes of reperfusion followed by freeze clamping. Tissue homogenates were assayed for 5'-nucleotidase by the linked formation of nicotinamide-adenine dinucleotide at 340 nm (Arkesteijn method). Postischemic recovery of developed pressure was 86% +/- 3% in neonates (n = 5) versus 38% +/- 3% in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). 5'-Nucleotidase activity was 4400 +/- 1208 nmol/min/gm in neonates (n = 5) versus 13,938 +/- 830 nmol/min/gm in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). We conclude that (1) 5'-nucleotidase activity is 68% lower in neonatal than in adult myocardium and (2) functional recovery after ischemia inversely relates to 5'-nucleotidase activity.
The Bezold-Jarisch reflex is an inhibitory reflex that originates from the heart, is mediated by the vagus nerve, and is manifested by hypotension and bradycardia. We present 4 pediatric cardiac surgical patients, aged 1 day to 9 months, who exhibited cardiovascular collapse in their early postoperative course. In each patient, cardiovascular deterioration was marked by an insidious decrease in arterial blood pressure without an associated change in heart rate, central venous pressure, or airway pressure. Bradycardia followed the decrease in blood pressure. The Bezold-Jarisch reflex was suspected and atropine was administered, first as a bolus injection at 0.01 mg/kg, and later, as a continuous infusion at 0.01 mg.kg-1.h-1. Atropine prevented recurrent episodes of hypotension and bradycardia. We believe the Bezold-Jarisch reflex is more prevalent than previously suspected in postoperative pediatric cardiac surgical patients.
The extended aortic root replacement technique is used for the surgical repair of left ventricular outflow tract obstruction complicated by concurrent hypoplastic aortic annulus, multiple levels of obstruction, or aortic insufficiency. Extended aortic root replacement incorporates the concepts of aortic root replacement and aortoventriculoplasty to create a comparatively simple procedure. Unique features of the technique include the implantation of an allograft, which makes the need for anticoagulation obsolete, and use of the donor mitral leaflet to enlarge the outflow tract. Since 1985, 32 patients in Denver have undergone placement of a cryopreserved aortic valve allograft as part of extended aortic root replacement. There were four hospital deaths (13%), and 1 child underwent cardiac transplantation 30 hours after operation. In 6 months to 4.8 years of follow-up, a 14-year-old boy with familial hyperlipidemia required coronary artery bypass grafting, and 3 children experienced allograft calcification with progressive insufficiency, which prompted allograft replacement. The other 23 patients are clinically well.
The patient presented is a 27-month-old male with complex congenital heart disease consisting of severe left ventricular outflow tract obstruction and ventricular septal defect who had undergone a pulmonary trunk-to-aorta graft and a pulmonary artery banding procedure as a neonate. Sometime after this repair, but at least 15 months prior to presentation to this institution for placement of an aortic homograft, the pulmonary trunk band apparently slipped and migrated over the right pulmonary artery, severely limiting blood flow to the right lung and increasing flow to the left. Severe pulmonary hypertension developed, with a main pulmonary artery pressure of 94/53 mm Hg. We present clinical and radiographic evidence that the resulting chronic high blood flow and pressure in the left lung ultimately resulted in hypoperfusion of that lung, presumably secondary to chronic vascular changes with greatly increased vascular resistance. Upon surgical repair and removal of the constrictive band from the previously banded right PA, blood flow was increased to the low resistance right lung causing right-sided unilateral pulmonary edema, ventilation/perfusion mismatching, and severe hypoxemia. Perfusion studies documented that less than 10% of blood was directed to the left lung, with greater than 90% to the right. Perfusion studies 9 months postoperatively continued to demonstrate minimal blood flow to the left lung. Discussion focuses on the effects of mechanical forces and the interaction with hypoxia in causing pulmonary vascular remodeling.
Pediatric cardiologists are often consulted to evaluate continuous murmurs in children. This case report describes a child with a congenital vertebral-jugular fistula who presented with torticollis and a continuous murmur. The differential diagnosis of continuous murmurs in this setting is discussed.
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Twelve patients with anomalous left coronary artery (LCA) from the pulmonary artery were treated surgically. Mean age was 13 months and mean weight, 7.7 kg. One of the following techniques was used in 8 patients: suture obliteration of the coronary orifice, ligation of the anomalous LCA and grafting of the internal mammary artery to the distal LCA, aortic reimplantation of the anomalous LCA, creation of an aortopulmonary window, and direct anastomosis to the right subclavian artery. In 4 patients, a new technique to establish a two-coronary artery system involved tube extension of the anomalous LCA with pulmonary artery wall and then anastomosis to the right subclavian artery using cardiopulmonary by-pass without aortic cross-clamping. There were two hospital deaths (17%) and one late death. The condition of the 9 long-term survivors was improved at late follow-up. Postoperative assessment showed smaller Q wave on the electrocardiogram, reduced cardiac size, and good left ventricular function. All patients in whom the repair was done using the new technique were free from postoperative cardiac complications, had shortened hospital stays, and were alive with a patent two-coronary artery system at late follow-up. We believe this approach is a safer method for establishing a two-coronary artery system in infants and small children with an anomalous LCA arising from the pulmonary artery.
We reviewed the records of 167 neonates and older children undergoing ligation of a patent ductus arteriosus to determine the prevalence of recurrent laryngeal nerve injury and identify risk factors that might increase the likelihood of injury. Paralysis or paresis of the left vocal cord was identified by fiberoptic laryngoscopy in seven patients. All seven weighted less than 1500 gm at the time of operation and the ductus had been ligated with a metal clip. All had persistent symptoms when observed for 5 to 19 months. Injury to the left recurrent laryngeal nerve occurs infrequently but may have long-term consequences.
Cryopreserved allograft valves and valved conduits have been used in 122 patients during the past 3 years for surgical repair of congenital heart disease. In 55 of these patients, the right ventricular outflow tract was reconstructed with a pulmonary allograft conduit. Although most children requiring a conduit had complex lesions, 12 patients with tetralogy of Fallot without pulmonary atresia or absent valve syndrome have been treated in this manner since April 1985. Patients were selected for conduit therapy because of congenital or iatrogenic pulmonary artery problems (nine patients had 12 prior shunts) or increased pulmonary vascular resistance. Ages ranged from 7 months to 6 years (mean 3.1 years) and weights from 7.4 to 18.5 kg (mean 12.2 kg). Pulmonary artery conduit size ranged from 16 to 24 mm internal diameter (mean 22 mm). Distal pulmonary artery reconstruction beyond the bifurcation was required in nine patients and the proximal connection was completed with a hood-shaped patch. One operative death (8.3%) occurred at 20 days as a result of severe right ventricular dysfunction. Left pulmonary artery thrombosis was discovered postmortem. Eleven survivors observed for 3 to 37 months (mean 17 months) are without cardiac symptoms. A chronologically overlapping group of tetralogy of Fallot repairs accomplished with a transannular patch was also reviewed. Twenty-five patients aged 2 months to 4 years (mean 1.7 years) and weighing 3.6 to 14.8 kg (mean 9.2 kg) underwent this procedure from April 1983 to January 1987 (seven patients had one prior shunt each). The mortality rate in this group was 28% (six operative deaths and one late death). Of 18 survivors observed from 20 to 60 months (mean 41.4 months), five (28%) have required pulmonary artery conduit reconstruction for chronic right ventricular failure. Postrepair right ventricular/left ventricular pressure ratios were available in 19 patients, including five of seven who died and three of five who required reoperation. The ratios averaged 0.54, which indicates adequate relief of obstruction. The operative mortality rate from a number of series for transannular patch repair of tetralogy of Fallot averages 16%, ranging from 3% to 63%. However, when distal pulmonary artery problems are added as a risk factor this rate rises to 21%, and valved conduit insertion increases the mortality rate (Kirklin and Barratt-Boyes, 1986). Although not clearly superior, pulmonary artery conduit repair of tetralogy of Fallot achieves results comparable with those of transannular patch repair and is recommended as an alternative, particularly when distal pulmonary artery anatomy is abnormal or vascular resistance is elevated.
The experience at the University of Colorado with the St. Jude Medical cardiac valve was reviewed to determine the feasibility of placing this prosthesis in children and the role of anticoagulation. A St. Jude Medical cardiac valve was placed in 33 patients ranging in age from 2.5 months to 17 years. Seven patients were less than 1 year of age. Nineteen valves were placed in the aortic position in patients aged 5 months to 17 years (mean 9.5 years). Five patients had valve replacement only, 13 had concomitant aortoventriculoplasty and 1 a Manouguian procedure. Indications for anulus enlarging procedures were recurrent subaortic stenosis or inability to place an adult-sized valve in the native aortic anulus, or both. There were no early or late deaths. Fourteen valves were placed in the mitral position. They were anular positioned in 6 patients aged 6 months to 16 years and supraanular positioned in 8 patients aged 2.5 months to 2 years. There were no deaths with the anular positioned replacements and seven deaths (two early and five late) with the supraanular positioned replacements. Four of the five late deaths were associated with marked pre- and postoperative left ventricular dysfunction. The follow-up time was 784 patient-months in 31 long-term survivors. Anticoagulation was achieved with warfarin, usually in combination with sulfinpyrazone, dipyridamole or aspirin. There were four episodes of thromboembolism, three occurring in patients with suboptimal anticoagulation, and one in a patient lost to follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)
Nonpenetrating traumatic ventricular septal defect is rare. A triad of blunt chest trauma, holosystolic precordial murmur, and ECG abnormalities should suggest the diagnosis. Surgical repair, when indicated by progressive failure, rising pulmonary artery pressures, or significant (2:1 or larger) left-to-right shunt, has been shown to be very effective. Optimally, a period of several weeks from the injury should elapse before operative intervention is undertaken. Intra-aortic balloon pump may be helpful to stabilize patients acutely, and, in selected instances, allow delay of surgical repair so that the tissue around the defect may hold sutures more securely.
Recurrent tunnel stenosis of the left ventricular outflow tract following operation for subaortic stenosis and hypoplastic aortic annulus remain a challenge for pediatric cardiac surgeons. We have recently applied a new technique of extended aortic root replacement using an aortic allograft to treat three patients who had previously been operated upon for subaortic stenosis and three who had aortic stenosis with a hypoplastic aortic annulus. This new procedure combines the concept of aortoventriculoplasty with allograft aortic root replacement and coronary artery reimplantation. The valved aortic homograft is used in place of an aortic valve prosthesis and the attached anterior mitral leaflet augments the interventricular septum to relieve the subvalvular left ventricular outflow tract obstruction. The coronary ostia are then reimplanted into the allograft and distal graft to ascending aorta anastomosis completed. Allograft aortic tissue is then used to patch the right ventricular outflow tract. There have been no operative or late deaths. One patient developed Serratia marcescens mediastinitis but recovered uneventfully after mediastinal drainage. Two cases of transient complete heart block reversed spontaneously. A patient with type II hyperlipidemia developed postpericardiotomy syndrome early, which resolved but then required reoperation at six months for stenosis of the distal anastomosis and left main coronary stenosis, both thought to be complications of his underlying disease. Completely benign convalescence and early follow-up has occurred in the last two patients. This modified technique using aortic allograft was very helpful in treating these difficult problems, and the lack of mortality, limited morbidity, and good function results are encouraging.
Complex left ventricular outflow tract obstruction after operation for subaortic stenosis or with hypoplastic aortic anulus remains a challenge for pediatric cardiac surgeons. We have recently applied a new technique of extended aortic root replacement using a cryopreserved aortic allograft to treat two patients who had previously been operated on for subaortic stenosis and a third who had aortic stenosis with a hypoplastic aortic anulus. This new procedure combines the concept of aortoventriculoplasty with aortic root replacement and coronary artery reimplantation. The valved aortic homograft is used in place of an aortic valve prosthesis and the attached anterior mitral leaflet augments the interventricular septum to relieve the subvalvular left ventricular outflow tract obstruction. The coronary ostia are then reimplanted into the allograft and an anastomosis between the distal graft and the ascending aorta is completed. Allograft aortic tissue is then used to patch the right ventricular outflow tract. One patient had aortic stenosis with annular hypoplasia and did well after extended root replacement. Two patients had previous operations for subaortic stenosis before undergoing extended aortic root replacement. One required mediastinal exploration and drainage at 2 weeks for Serratia marcescens mediastinitis and bacteremia, but uncomplicated recovery followed. The other patient had complete heart block for 2 days, but normal sinus rhythm resumed and convalescence was benign. This modified technique with the aortic allograft was very helpful in treating these difficult problems, and the lack of mortality, limited morbidity, and good functional results are encouraging.
A four-year-old boy with DORV and hypoplastic left ventricle underwent a modified Fontan procedure. He had a very difficult postoperative course complicated by continued pleural effusions. Eventually he died during a last ditch effort to ligate the thoracic duct at the right diaphragm. At autopsy, an obstructing giant thrombus was found in the right atrium. This rare complication probably was due to multiple factors, but we now anticoagulate all Fontan patients routinely in an effort to prevent this fatal problem.
A 3 1/2-year-old boy experienced right ventricular failure approximately two years after an operation for critical pulmonic stenosis. Severe pulmonary and tricuspid valvular insufficiency was documented echocardiographically and at cardiac catheterization. Treatment consisted of a tricuspid valve annuloplasty and creation of an autologous monocusp valve using the anterior wall of the pulmonary artery. The procedure was well tolerated, and early competence of the pulmonary valve was shown intraoperatively by pressure recordings and postoperatively by Doppler echocardiography. However, at recatheterization one year later, there was no evidence that the monocusp valve was functioning. This experience does not support the prior successful application of this technique in animals.