Aortic valve graft implantation in rats: a new functional model.

BACKGROUND: Allograft heart valves used in cardiac surgery often fail at an unacceptable rate. Immune mechanisms contribute to this failure, but adequate and functional small-animal valve models to characterize this phenomenon are lacking. The objective of this study was to create native aortic valve insufficiency in recipient rats to provide for a functional abdominal aortic valve graft implant. METHODS: Lewis recipient rats underwent single-leaflet injury of their native aortic valve through a right carotid catheter injury. Animals were allowed to recover for 28 days, at which time a Lewis aortic valve graft was implanted infrarenally. Echocardiography with color flow Doppler scanning was performed before aortic injury, 1 week after aortic injury, and after abdominal implantation of a valve graft in animals with native aortic insufficiency. RESULTS: After aortic valve injury, all animals had moderate-to-severe aortic insufficiency with a significant increase in diastolic and systolic left ventricular dimensions. Color flow Doppler scanning revealed diastolic aortic flow reversal from the aortic valve extending to the infrarenal abdominal aorta. Aortic valve grafts were then implanted infrarenally in animals with created aortic valve insufficiency and resulted in 100% patency and preservation of leaflets at 4 weeks after implantation. Leaflet motion of the abdominal graft was visualized by means of M-mode echocardiography. CONCLUSION: Compensated native aortic insufficiency results in aortic diastolic flow reversal distal to the infrarenal aorta, thus allowing normal motion of the infrarenal allograft leaflets. This functional model will provide an opportunity to investigate the role of immunologic valve injury in the failure of valve allografts.

Auscultation of the heart: a trial of classroom teaching versus computer-based independent learning.

Declining skills in auscultation of the heart prompted an evaluation of teaching methods for medical students. A comparison of classroom teaching and computer-aided independent learning of auscultation was carried out with two groups of approximately 20 second-year medical students. Both groups used approximately 20 recorded normal and abnormal heart sounds and murmurs, chosen to illustrate learning issues. For the classroom group a cardiologist presented each case through multiple stethophones and led the discussion. The individual study group used a new CD-ROM collection of cases and recordings in quiz format, with a hypertext link to a comprehensive text on auscultation and additional recordings. Students were tested with 16 multiple choice and 5 open questions on eight selected recordings, and evaluated the teaching by questionnaire. The classroom-taught students scored higher on open questions than the CD-ROM-taught group, but in general performance by both groups was satisfactory and equivalent. Students of both groups repeatedly had difficulty classifying regurgitant and ejection murmurs and identifying characteristics of the second heart sound. Both CD-ROM and classroom teaching methods were highly rated by students but most students preferred a combination.

Atrioventricular septal defect with tetralogy of Fallot: results of surgical correction.

BACKGROUND: The outcome of surgical correction of complete atrioventricular septal defect with tetralogy of Fallot has improved in recent years. Controversy exists about the optimal approach to this complex lesion. Our experience over the past 8 years with a single technique is reviewed. The important anatomic features of this lesion are discussed in relation to our method of repair. METHODS: Between 1988 and 1996, 11 consecutive patients underwent correction of complete atrioventricular septal defect with tetralogy of Fallot. Nine patients had undergone prior palliative shunts. The two-patch technique for atrioventricular septal defect was used. The ventricular septal defect was closed through a right ventriculotomy in each case. The commissure between the superior and inferior bridging leaflets of the left portion of the common atrioventricular valve was closed in each patient. Management of the right ventricular outflow tract was individualized. RESULTS: There was one mortality in the early postoperative period. One patient required reoperation for closure of a dehiscent left atrioventricular valve cleft. All survivors are currently in New York Heart Association functional class I or II at follow-up ranging from 2 to 101 months. CONCLUSIONS: Atrioventricular septal defect with tetralogy of Fallot can be corrected with low mortality using the two-patch technique and closure of the ventricular septal defect through a combined approach using a right ventriculotomy and right atriotomy. Routine closure of the commissure of the left portion of the atrioventricular valve results in a low incidence of regurgitation. A good functional result can be achieved in most patients at intermediate-term follow-up.

Paediatric echocardiography by telemedicine--nine years' experience.

In 1987 we established a realtime echocardiography service by telemedicine from the paediatric cardiology department of a tertiary-care hospital in Halifax. The service was initially provided to single regional hospital but was expanded to six regional hospitals in the three Canadian Maritime Provinces. The system used a dial-up broadband video-transmission service provided by the telephone companies. Records of all transmissions were kept prospectively and reviewed to January 1997. A total of 324 transmissions were made. During 1995-96 there were 135 studies: 69 (51%) were urgent examinations of newborn children and 30 (22%) were urgent examinations of older children; repeat studies and postoperative checks (usually for pericardial effusion) accounted for the other 36 studies (27%). The images were of broadcast quality except in five cases where problems with transmission or poor sedation occurred. A comparison of 26 transmitted studies with repeat, 'in person' studies showed no important discrepancies in diagnosis. During the two-year study period, the cost of the network (equipment leasing costs and telecommunications costs) was C$90,000. Use of the telemedicine network saved unnecessary patient transfer in 31 cases. The cost of the transportation avoided was C$100,000-C$118,000. This review confirms our preliminary findings that broadband echocardiography transmission provides a service comparable in availability and accuracy to that provided in our paediatric cardiology division.

Factors in the early failure of cryopreserved homograft pulmonary valves in children: preserved immunogenicity?

METHODS: Between 1990 and 1995, 48 homograft valves (15 aortic and 33 pulmonary), cryopreserved on-site, were implanted to reconstruct the right ventricular outflow tracts in 44 children (mean age 6.2 +/- 6.0 years; range 3 days to 20.2 years). Blinded serial echocardiographic follow-up evaluation was performed for all 45 valves in the 41 survivors. RESULTS: Four homograft valves were replaced because of pulmonary insufficiency (3) or stenosis and insufficiency (1). Freedom from reoperation was 90% (70% interval, 84% to 97%) at 50 months. During the follow-up period 15 valves developed progressive pulmonary insufficiency of at least two grades. Three valves developed transvalvular gradients of > or = 50 mm Hg, and one of these valves was also insufficient. The freedom from echocardiographic failure (two or more grades of pulmonary regurgitation or > or = 50 mm Hg gradient) was 44% at 50 months (70% confidence interval, 32% to 55%). Young age (p = 0.03), low operative weight (p = 0.04), small graft size (p = 0.04), and homograft retrieval-to-cryopreservation time of less than 24 hours (p = 0.02) were significantly associated with failure. The type of donor valve (pulmonic or aortic), donor age, and blood group mismatch were not associated with failure, although blood group mismatch approached significance (p = 0.05). CONCLUSIONS: Homografts function well as conduits between the pulmonary ventricle and pulmonary arteries if long-term valve competency is not crucial. However, many rapidly become insufficient. This has important implications for the choice of a valve if the indication for valve replacement is to protect a ventricle failing due to pulmonary insufficiency. Short periods between homograft retrieval and cryopreservation enhance viability and antigenicity. This may suggest an immunologic basis for the failure.

Trends in the prevalence of congenital heart disease: comprehensive observations over a 24-year period in a defined region of Canada.

OBJECTIVE: To determine the prevalence of congenital heart disease (CHD) in the three Maritime provinces, and to study prevalence differences among provinces and defined regions within these provinces. DESIGN: Each province was divided by counties into regions. All cases of CHD who were born alive in the study area between 1966 and 1989 were entered in a registry. Prevalences were analyzed for each province and for selected regions per year, per 1000 live births, and by diagnosis made by one year of age and by the 16th birthday. Comparison was then made with prevalences of a group who had severe lesions. INTERVENTIONS: Excepting a small number of CHD cases who were diagnosed by autopsy only, diagnosis was made by pediatric cardiologists using appropriate procedures, including cardiac ultrasound and cardiac catheterization. SETTING: The only tertiary care centre for children's heart disease in the provinces of Nova Scotia, New Brunswick and Prince Edward Island, areas of relative geographic isolation (combined population of 1.75 million people). MAIN RESULTS: A statistically significant positive linear trend occurred in these provinces during the study. The recorded prevalence of CHD in New Brunswick was significantly lower. Pooled prevalences by the first and 16th birthdays (8.0 and 12.5 per 1000 live births, respectively) of two regions of highest prevalence for 1980-86 were significantly higher (P < 0.05) than the pooled prevalence rate of all the remaining regions. Prevalence rates of a group with severe lesions were stable for 1976-86 in all regions. CONCLUSIONS: Differences in prevalence of CHD among provinces and regions were related to ascertainment levels. Prevalence of CHD with diagnosis by the first and 16th birthdays were approximately 8.0 and 12.5 per 1000 live births, respectively. The prevalence rate of a severe lesion group was a stable measure.

Ambulatory monitoring of the sudden death of an adolescent with hypertrophic cardiomyopathy.

Sudden death is an important cause of mortality in hypertrophic cardiomyopathy. Several mechanisms have been proposed, but ambulatory monitoring of the event has rarely occurred. The case of an adolescent girl with congenital hypertrophic cardiomyopathy and arthrogryposis multiplex congenita is presented. Despite appropriate therapy and severe activity limitation, the patient's condition progressively worsened. The patient died suddenly in her sleep, one month after a myocardial myomectomy for subaortic stenosis. The fortuitous ambulatory electrocardiographic (ECG) monitoring of the event recorded polymorphic ventricular tachycardia degrading into ventricular fibrillation. Retrospective review of previous ambulatory ECG revealed the presence of nonsustained ventricular tachycardia, a predictive determinant for sudden death, and atrioventricular node dysfunction. However, the patient had never reported symptoms during the dysrhythmias. The pathological specimen showed an unexpected old apical infarction scar, suggesting that her preoperative cardiac status was worse than suspected. In summary, the mechanism of sudden death in this patient was revealed by ambulatory ECG monitoring, and the involvement of neural and myocardial factors are proposed.

Follow-up after patch aortoplasty for coarctation of aorta.

BACKGROUND: Patch aortoplasty (PA) for coarctation of aorta (COA) can lead to aneurysm formation at the repair site. X-ray, echocardiogram and computed tomography are unreliable for diagnosis of this complication. OBJECTIVE: To evaluate prospectively patients with PA for COA by magnetic resonance imaging (MRI) to detect presence of aneurysm at the repair site. DESIGN: All patients who underwent PA at the authors' institution were identified. MRI was performed in transverse and long axis oblique views on all patients except those who had, or were going to have, aortic angiography for other reasons. Details of the surgical procedure were obtained from the hospital records. RESULTS: Of the 18 patients studied, 15 had MRI and three had aortic angiography. Age at PA ranged from one week to 13.3 years (mean 6.3 years). The interval from PA to MRI or angiography was 9.5 years (range four to 12.5). No aneurysm was detected in any patient. Recoarctation was diagnosed in two patients not previously suspected but discovered on MRI. At PA the intimal shelf causing coarctation was either not excised or only minimally trimmed in 14 of 15 instances. CONCLUSIONS: The incidence of late aneurysm formation following PA for COA is low in the authors' patients, possibly due to minimal intimal damage at repair, although these patients should be followed longer. MRI was useful for assessment of aneurysm and restenosis.

Assessment of blood pressures and gradients by automated blood pressure device compared to invasive measurements in patients previously operated on for coarctation of the aorta.

The aim of the study was to compare invasive and non-invasive blood pressure measurements and gradients. Twenty-two children and 16 adults previously operated for coarctation of the aorta were included. Invasive blood pressures were recorded proximally and distally close to the former operation site and non-invasive systolic blood pressures were recorded by an automated sphygmomanometer on right arm and leg. The adults were investigated at rest and during supine exercise. The correlation between invasive and non-invasive measurements of proximal blood pressures in adults at rest and children were the following, r = 0.92, SD 7.6 mmHg (n = 16) and r = 0.85, SD 11 mmHg (n = 22) respectively. The corresponding correlation for the distal blood pressures were the following for adults at rest 0.64, SD 11.9 mmHg and in children r = 0.82, SD 9.2 mmHg. During exercise in adults we found a low correlation when comparing invasive and non-invasive proximal and distal blood pressures and a poor correlation regarding the gradients, r = 0.50, SD 16 mmHg, r = 0.45, SD 15.9 mmHg and r = 0.30, SD 22.9 mmHg respectively (n = 16). We also measured the time interval between cessation of exercise and completion of the blood pressure recordings, which gave a mean interval of 73 sec (range 45-115 sec). During that interval the mean fall in the proximal blood pressure was 37 mmHg (range 20-80 mmHg), and the mean fall of the gradient was from 41 mmHg (range 20-76 mmHg) to 23 mmHg (range 6-56 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiographic and morphologic evaluation of patients following operative repair of aortic coarctation.

Sixty-six patients operated on previously for coarctation of the aorta were included in the study. There were 50 children and 16 adults. Invasive and non-invasive gradients were recorded. Anatomical obstruction was evaluated by angiography in 54 patients and the numbers and size of collaterals were quantified. The closest correlation was found between Doppler-estimated gradients and invasive peak-instantaneous gradients (r = 0.87). The relation between anatomical obstruction and invasive peak-to-peak gradients, Doppler gradients and diastolic flow ere discouraging (r = 0.64, 0.54 and 0.35). Liberal indications for angiography or magnetic resonance tomography are recommended.

Quantification of left to right shunts by echo Doppler cardiography in patients with ventricular septal defects.

Thirty-one patients with ventricular septal defect were evaluated with Echo Doppler cardiography and colour flow mapping. The ventricular septal defect area was estimated by measurement of the jet diameter by colour flow mapping. The ventricular septal defect flow was calculated as the product of the cross-sectional area of the ventricular septal defect and the velocity time integral of flow through the defect. In ten patients the diameter obtained by colour flow mapping was compared with the diameter obtained at angiography, r = 0.88 (SD = 0.14 cm). The aortic flow was calculated as the product of left ventricular outflow tract cross-sectional area and the corresponding velocity time integral. QP/QS ratio was estimated as (ventricular defect flow + aortic flow)/aortic flow and compared to estimates by a radionuclide or oximetric method. A correlation of r = 0.95 (SD = 0.23) was found.

Noninvasive estimation of aortic valve areas in children with aortic stenosis.

Fifteen children with aortic stenosis were examined with Echo-Doppler cardiography in order to evaluate the use of the continuity equation to calculate the aortic valve area. The results were compared to invasive estimates of valve area calculated with the Gorlin's equation. A close correlation between the two methods, r = 0.94, was found and it is concluded that even in children an accurate estimate of valve area can be expected with the use of the continuity equation.

The natural course of supravalvar aortic stenosis and peripheral pulmonary artery stenosis in Williams's syndrome.

The haemodynamic findings from two serial cardiac catheterisations in ten patients with Williams's syndrome were reviewed. The median ages at study were one and nine years. Raised mean (SD) left ventricular peak systolic pressures associated with supravalvar aortic stenosis increased significantly with time from 121 (25) mm Hg to 153 (29) mm Hg. The peak systolic pressure drop between the left ventricle and aorta (measured in seven patients) increased significantly from 25 (25) mm Hg to 50 (35) mm Hg. Raised right ventricular peak systolic pressure associated with peripheral pulmonary artery stenosis (in eight patients) decreased significantly with time from 52 (26) mm Hg to 28 (6) mm Hg. Supravalvar aortic stenosis in Williams's syndrome seems to progress rapidly, and careful monitoring is indicated. There is a strong likelihood that peripheral pulmonary artery stenosis in Williams's syndrome will improve spontaneously with time.

Echocardiography by telephone--evaluation of pediatric heart disease at a distance.

A 24-hour telephone transmission service was established for pediatric echocardiography between a general hospital and a children's hospital 500 km distant. Studies were transmitted in real time for interpretation and diagnosis by a pediatric cardiologist. In the first 9 months of operation, studies were transmitted for 18 children with a median age of 5 months. Image and sound quality was excellent. Complete segmental diagnosis was made in 16 patients, and further study was needed in 2 others. In 8 of the 18 patients a new diagnosis was provided, and in 10 patients diagnosis was confirmed. Congenital heart disease was found in 12 patients, other heart disease in 2 and a normal heart in 4. The population included 2 fetuses whose echocardiograms showed hypoplastic left heart and intracardiac tumor. In 4 patients transport was avoided. This is the first report of echocardiographic transmission by telephone, which was shown to be clearly feasible, cost-effective and diagnostic. It provides emergency access to specialist expertise, and may avoid hazardous and expensive transport of ill children.

Isolated infundibuloarterial inversion (S,D,I): a newly recognized form of congenital heart disease.

A newly recognized form of congenital heart disease is presented that is characterized by viscero-atrial situs solitus (S), D-loop ventricles (D), and inverted normally related great arteries (I), the segmental combination being (S,D,I). This anomaly may be called isolated infundibuloarterial inversion because only the subsemilunar infundibulum and the great arteries are inverted, whereas the atrial and the ventricles are not. All three patients had atrioventricular concordance, ventriculoatrial concordance, dextrocardia, superoinferior ventricles, crisscross atrioventricular relations, underdevelopment of the right ventricle, a large ventricular septal defect, and an inverted tetralogy of Fallot type of malformation of the infundibulum and great arteries. The condition known as crisscross atrioventricular relations was found in these three patients to be a major ventricular malposition characterized by marked clockwise rotation of the ventricles, as seen from the front. Two of these three cases were diagnosed accurately and repaired successfully.

Stenosis of individual pulmonary veins: radiologic findings.

Congenital stenosis of individual pulmonary veins is uncommon. Of the 49 cases reported, four were seen at the IWK Hospital for Children and are reported here. Plain radiographs show a shift of the heart toward the side of major involvement, Kerley B lines, fluid in the fissures, and interstitial edema of the affected lobes. These findings, while subtle, should nevertheless suggest stenosis. Technetium-99m macro-aggregate lung perfusion scans show absence of or diminished perfusion of the affected lobes. The diagnosis can usually be confirmed with angiography. Congenital stenosis of individual pulmonary veins should be considered in children with repeated pulmonary infections, dyspnea, failure to thrive, hemoptysis, or unexplained pulmonary hypertension.

Balloon catheter dilatation of coarctation of the aorta in young infants.

In four young infants with symptomatic coarctation of the aorta the narrow aortic segment was dilated with a balloon angioplasty catheter. Three of the infants also had appreciable heart defects and one infant had undergone surgery before and had had one previous dilatation. Dilatation was well tolerated and good femoral pulses appeared in all cases, but these disappeared over one to seven days. Despite this, two patients showed some symptomatic improvement over four months. One patient died after perforation of the aorta by an angiographic catheter after dilatation. Relieving coarctation in young infants by catheter dilatation appears incomplete, but it may give symptomatic improvement. Further trial of the procedure will determine whether patients who have undergone surgery and those who have not may benefit. Careful attention to technique and avoidance of manipulations after dilatation are essential if complications are to be avoided.

Frequent ventricular ectopic activity without underlying cardiac disease: analysis of 45 subjects.

Forty-five subjects, aged 2 weeks to 62 years, who presented with frequent (greater than 100/day) ventricular ectopic beats (VEBs) and without evidence of underlying cardiac disease were studied. The spectrum of ventricular dysrhythmia was assessed by 24-hour ambulatory electrocardiography and exercise tolerance test. Sinus rhythm was the prevailing rhythm in all subjects. VEB frequency averaged 444 +/- 454 per hour (range 0 to 1,863) over the 24-hour monitoring period and was not significantly different during waking or sleeping periods. There was no simple correlation of VEB frequency with prevailing sinus rate (r = -0.0006; p = not significant [NS]). The prevalence of complex VEBs (multiform, R-on-T and repetitive) was relatively high (18 of 45 patients), and was equally distributed about the median VEB frequency of 314 VEBs/hour (7 of 18 versus 11 of 18; NS). Of the 43 subjects who had exercise tests, 37 had VEBs during the preexercise rest phase, compared with only 11 at peak exercise (p less than 0.0001). To assess the short-term natural history of the VEBs, 27 subjects had repeat clinical examinations and 24-hour electrocardiograms at a mean interval of 8 months. All remained well. Although there was considerable individual temporal variability of VEB frequency in this subgroup, there was no significant change in group mean values (415 +/- 409 VEBs/hour initially versus 401 +/- 383 VEBs/hour at follow-up study; NS). The relative temporal constancy of VEB frequency in the group as a whole was also reflected in a high linear correlation of VEB frequency at initial and follow-up studies (r = 0.816; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Polytetrafluoroethylene shunts in congenital heart disease.

Over a 2-year period the authors inserted 22 systemic to pulmonary artery shunts using a polytetrafluoroethylene (PTFE) graft in 19 children. A modified Blalock-Taussig shunt was established in 18 instances and an aorta to pulmonary artery shunt in 3: one patient had an aorta to right ventricle infundibulum shunt. Three children had obstructed grafts and in two others the grafts became stenosed; on of the latter group had successful removal of thrombus. The remaining grafts functioned well. Three other patients are presented. In two an interrupted aortic arch was repaired using a PTFE graft; one of these patients died at later closure of an aortopulmonary window, the other did well following repair of a ventricular septal defect and aortic valvotomy. The third child had a right ventricle to pulmonary artery shunt established for tetralogy of Fallot with pulmonary atresia; this resulted in some growth of the pulmonary arteries. The modified Blalock-Taussig shunt, using a PTFE graft, can be inserted without opening the pericardium, normal flow through the subclavian artery is not interrupted, the PTFE is easy to handle and the shunt can be inserted and taken down more easily than traditional shunts. For these reasons, the authors believe that this procedure, using PTFE, has an important role to play in the surgical management of children with congenital heart disease.