The St. Jude Medical cardiac valve in infants and children: role of anticoagulant therapy

Mechanical Mitral Valve Replacement: A Multicenter Study of Outcomes With Use of 15- to 17-mm Prostheses

BACKGROUND

The aim of this study was to evaluate early and mid-term outcomes (mortality and prosthetic valve reintervention) after mitral valve replacement with 15- to 17-mm mechanical prostheses.

METHODS

A multicenter, retrospective cohort study was performed among patients who underwent mitral valve replacement with a 15- to 17-mm mechanical prosthesis at 6 congenital cardiac centers: 5 in The Netherlands and 1 in the United States. Baseline, operative, and follow-up data were evaluated.

RESULTS

Mitral valve replacement was performed in 61 infants (15 mm, n = 17 [28%]; 16 mm, n = 18 [29%]; 17 mm, n = 26 [43%]), of whom 27 (47%) were admitted to the intensive care unit before surgery and 22 (39%) required ventilator support. Median age at surgery was 5.9 months (interquartile range [IQR] 3.2-17.4), and median weight was 5.7 kg (IQR, 4.5-8.8). There were 13 in-hospital deaths (21%) and 8 late deaths (17%, among 48 hospital survivors). Major adverse events occurred in 34 (56%). Median follow-up was 4.0 years (IQR, 0.4-12.5) First prosthetic valve replacement (n = 27 [44%]) occurred at a median of 3.7 years (IQR, 1.9-6.8). Prosthetic valve endocarditis was not reported, and there was no mortality related to prosthesis replacement. Other reinterventions included permanent pacemaker implantation (n = 9 [15%]), subaortic stenosis resection (n = 4 [7%]), aortic valve repair (n = 3 [5%], and aortic valve replacement (n = 6 [10%]).

CONCLUSIONS

Mitral valve replacement with 15- to 17-mm mechanical prostheses is an important alternative to save critically ill neonates and infants in whom the mitral valve cannot be repaired. Prosthesis replacement for outgrowth can be carried out with low risk.

Prosthesis-Patient Mismatch Negatively Affects Outcomes after Mitral Valve Replacement: Meta-Analysis of 10,239 Patients

OBJECTIVE

This study sought to evaluate the impact of prosthesis-patient mismatch on the risk of perioperative and long-term mortality after mitral valve replacement.

METHODS

Databases were researched for studies published until December 2018. Main outcomes of interest were perioperative and 10-year mortality and echocardiographic parameters.

RESULTS

The research yielded 2,985 studies for inclusion. Of these, 16 articles were analyzed, and their data extracted. The total number of patients included was 10,239, who underwent mitral valve replacement. The incidence of prosthesis-patient mismatch after mitral valve replacement was 53.7% (5,499 with prosthesis-patient mismatch and 4,740 without prosthesis-patient mismatch). Perioperative (OR 1.519; 95%CI 1.194-1.931, P<0.001) and 10-year (OR 1.515; 95%CI 1.280-1.795, P<0.001) mortality was increased in patients with prosthesis-patient mismatch. Patients with prosthesis-patient mismatch after mitral valve replacement had higher systolic pulmonary artery pressure and transprosthethic gradient and lower indexed effective orifice area and left ventricle ejection fraction.

CONCLUSION

Prosthesis-patient mismatch increases perioperative and long-term mortality. Prosthesis-patient mismatch is also associated with pulmonary hypertension and depressed left ventricle systolic function. The findings of this study support the implementation of surgical strategies to prevent prosthesis-patient mismatch in order to decrease mortality rates.

The ordeal of left atrioventricular valve replacement in children under 1 year of age

OBJECTIVES

This study reviews the outcomes of children under 1 year of age who had left atrioventricular valve (LAVV) replacement (LAVVR) in one centre and explores the benefits of an innovative approach for LAVVR in very small patients.

METHODS

Thirteen consecutive patients operated for LAVV replacement between 1997 and 2016 were reviewed retrospectively. Indication for surgery was regurgitation in 7, stenosis in 5 and both stenosis and regurgitation in 1. Nine patients (69%) had previous LAVV repair. Median age at surgery was 126 days (39-327 days). In the primary surgery, 7 mechanical valves and 1 mitral homograft were implanted. Five inverted semilunar valve conduits were implanted consisting of a Contegra valve in 4 and a pulmonary homograft in 1.

RESULTS

Hospital mortality was 31% (4 of 13). Two patients required postoperative extracorporeal membrane oxygenation. Six patients developed complete atrioventricular block, with 2 survivors requiring a pacemaker. Late mortality was 31% (4 of 13). Two of the 4 patients who received an inverted Contegra conduit died. Median follow-up of the 5 survivors was 4 years (2-16 years). Four patients had 10 further replacements consisting of 6 redo conventional mechanical valves replacement, 3 supra-annular valve implantation, and 1 modified Ross II. The 5 inverted semilunar valve conduits implanted lasted for 1, 5, 6, 22 and 37 months.

CONCLUSIONS

LAVVR below 1 year of age is associated with a considerable operative and late mortality. LAVVR with an inverted conduit bearing semilunar valves may be an alternative strategy for patients with the smallest annuli.

Supra-annular mitral valve implantation in very small children

OBJECTIVE

Mitral valve replacement (MVR) is a surgical option when mitral valvuloplasty is not feasible/successful. This study reviews our experience with MVR in very young children.

METHODS

From July 2004 to January 2014, seven children (mean age 13.3 ± 11.2 months; range 4 months to 35 months; mean body weight 6.0 ± 2.2 kg) underwent MVR with a mechanical prosthesis in the supra-annular position. To provide better exposure in the left atrium, we performed in all but one case a biatrial transeptal incision according to Guiraudon. Six patients had congenital defects of the mitral valve and one had rheumatic. Six patients had undergone previous cardiosurgical procedures.

RESULTS

All patients were implanted with a CarboMedics (CarboMedics, Austin, TX, USA) mechanical prosthesis. Mean prosthesis size was 19.0 ± 3.1 mm (range 16 to 25). There were no cases of operative or late mortality. At follow-up (mean 67.1 ± 34.8 months; range 25 to 108 months) two patients (28.6%) required reoperation both for thrombotic pannus formation over the disc at two and three months from first operation, respectively; only in one case was replacement necessary.

CONCLUSION

Supra-annular MVR may be considered a feasible secondary surgical option in children with a small annulus when mitral valvuloplasty is unsuccessful or unsuitable. Early and mid-term outcomes are acceptable but complications are not uncommon, especially related to thrombotic events.

Tissue Doppler imaging in rheumatic carditis

OBJECTIVE

Our study was undertaken to assess cardiac functions by tissue Doppler echocardiography in patient with primary episode of rheumatic carditis.

METHODS

We divided 82 patients with rheumatic carditis were divided in two groups; 50 patients with mild and 32 patients with mitral regurgitation of grade two or more. A control group consisted of 30 healthy children free of any disease. All children underwent conventional and tissue Doppler echocardiography initially and at the time of the follow-up examination.

RESULTS

Myocardial systolic wave velocity of the mitral annulus was significantly higher in patients with mitral regurgitation of grade two or more when compared to the control group, but was not different between patients with mild mitral regurgitation and healthy subjects at the time of the initial attack. Myocardial precontraction time, myocardial contraction time, and the ratio of myocardial precontraction and contraction times were significantly prolonged, and the systolic myocardial velocity of the mitral annulus was significantly decreased in patients with mitral regurgitation of grade two or more at the time of the follow-up examination. The myocardial systolic wave velocity was significantly lower, and myocardial precontraction time, myocardial contraction time, and the ratio of the precontraction and contraction times, were significantly longer or greater between patients with grade two or more mitral regurgitation and the control group at follow-up examination.

CONCLUSION

We detected subclinical systolic dysfunction of the left ventricle in children with a primary episode of rheumatic carditis due to ongoing ventricular volume overload. Tissue Doppler imaging provides a quantifiable indicator useful for cardiac monitoring of disease during the period of follow up.

Antithrombotic therapy in neonates and children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Neonates and children differ from adults in physiology, pharmacologic responses to drugs, epidemiology, and long-term consequences of thrombosis. This guideline addresses optimal strategies for the management of thrombosis in neonates and children.

METHODS

The methods of this guideline follow those described in the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that where possible, pediatric hematologists with experience in thromboembolism manage pediatric patients with thromboembolism (Grade 2C). When this is not possible, we suggest a combination of a neonatologist/pediatrician and adult hematologist supported by consultation with an experienced pediatric hematologist (Grade 2C). We suggest that therapeutic unfractionated heparin in children is titrated to achieve a target anti-Xa range of 0.35 to 0.7 units/mL or an activated partial thromboplastin time range that correlates to this anti-Xa range or to a protamine titration range of 0.2 to 0.4 units/mL (Grade 2C). For neonates and children receiving either daily or bid therapeutic low-molecular-weight heparin, we suggest that the drug be monitored to a target range of 0.5 to 1.0 units/mL in a sample taken 4 to 6 h after subcutaneous injection or, alternatively, 0.5 to 0.8 units/mL in a sample taken 2 to 6 h after subcutaneous injection (Grade 2C).

CONCLUSIONS

The evidence supporting most recommendations for antithrombotic therapy in neonates and children remains weak. Studies addressing appropriate drug target ranges and monitoring requirements are urgently required in addition to site- and clinical situation-specific thrombosis management strategies.

Antithrombotic therapy in neonates and children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about antithrombotic therapy in neonates and children is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs, and Grade 2 suggests that individual patient values may lead to different choices (for a full understanding of the grading, see Guyatt et al in this supplement, pages 123S-131S). In this chapter, many recommendations are based on extrapolation of adult data, and the reader is referred to the appropriate chapters relating to guidelines for adult populations. Within this chapter, the majority of recommendations are separate for neonates and children, reflecting the significant differences in epidemiology of thrombosis and safety and efficacy of therapy in these two populations. Among the key recommendations in this chapter are the following: In children with first episode of venous thromboembolism (VTE), we recommend anticoagulant therapy with either unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) [Grade 1B]. Dosing of IV UFH should prolong the activated partial thromboplastin time (aPTT) to a range that corresponds to an anti-factor Xa assay (anti-FXa) level of 0.35 to 0.7 U/mL, whereas LMWH should achieve an anti-FXa level of 0.5 to 1.0 U/mL 4 h after an injection for twice-daily dosing. In neonates with first VTE, we suggest either anticoagulation or supportive care with radiologic monitoring and subsequent anticoagulation if extension of the thrombosis occurs during supportive care (Grade 2C). We recommend against the use of routine systemic thromboprophylaxis for children with central venous lines (Grade 1B). For children with cerebral sinovenous thrombosis (CSVT) without significant intracranial hemorrhage (ICH), we recommend anticoagulation initially with UFH, or LMWH and subsequently with LMWH or vitamin K antagonists (VKAs) for a minimum of 3 months (Grade 1B). For children with non-sickle-cell disease-related acute arterial ischemic stroke (AIS), we recommend UFH or LMWH or aspirin (1 to 5 mg/kg/d) as initial therapy until dissection and embolic causes have been excluded (Grade 1B). For neonates with a first AIS, in the absence of a documented ongoing cardioembolic source, we recommend against anticoagulation or aspirin therapy (Grade 1B).

Oral anticoagulation therapy in children

Treatment of thromboembolic complications in children has been the subject of considerable research in the last decade. Recommendations for oral anticoagulant therapy in children have been extrapolated from adult clinical trials. Coumarin derivatives are the preeminent oral antithrombotic agents used in children. Warfarin, acenocoumarol and phenprocoumon are the vitamin K antagonists used in children with thrombotic complications in different countries according to their experience and familiarity within a country or region. Prospective studies from Canada and Argentina propose guidelines for administering and monitoring warfarin and acenocoumarol therapy in children. These studies highlight the difficulty of their use in pediatric patients. Infants younger than 12 months of age require increased doses to achieve and maintain the therapeutic target INR, adjustments of loading dose to achieve the target INR faster with no overshooting, more frequent INR testing and dose adjustments, and fewer INR in the target range. The current indications for oral anticoagulants in children with thrombotic complications, the side effects of these agents and the reversal of the anticoagulant effect are discussed.

Antithrombotic Therapy in Children*

This article about antithrombotic therapy in children is part of the 7th American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh the risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this article are the following. In neonates with venous thromboembolism (VTE), we suggest treatment with either unfractionated heparin or low-molecular-weight heparin (LMWH), or radiographic monitoring and anticoagulation therapy if extension occurs (Grade 2C). We suggest that clinicians not use thrombolytic therapy for treating VTE in neonates, unless there is major vessel occlusion that is causing the critical compromise of organs or limbs (Grade 2C). For children (ie, > 2 months of age) with an initial VTE, we recommend treatment with i.v. heparin or LMWH (Grade 1C+). We suggest continuing anticoagulant therapy for idiopathic thromboembolic events (TEs) for at least 6 months using vitamin K antagonists (target international normalized ratio [INR], 2.5; INR range, 2.0 to 3.0) or alternatively LMWH (Grade 2C). We suggest that clinicians not use thrombolytic therapy routinely for VTE in children (Grade 2C). For neonates and children requiring cardiac catheterization (CC) via an artery, we recommend i.v. heparin prophylaxis (Grade 1A). We suggest the use of heparin doses of 100 to 150 U/kg as a bolus and that further doses may be required in prolonged procedures (both Grade 2 B). For prophylaxis for CC, we recommend against aspirin therapy (Grade 1B). For neonates and children with peripheral arterial catheters in situ, we recommend the administration of low-dose heparin through a catheter, preferably by continuous infusion to prolong the catheter patency (Grade 1A). For children with a peripheral arterial catheter-related TE, we suggest the immediate removal of the catheter (Grade 2C). For prevention of aortic thrombosis secondary to the use of umbilical artery catheters in neonates, we suggest low-dose heparin infusion (1 to 5 U/h) (Grade 2A). In children with Kawasaki disease, we recommend therapy with aspirin in high doses initially (80 to 100 mg/kg/d during the acute phase, for up to 14 days) and then in lower doses (3 to 5 mg/kg/d for > or = 7 weeks) [Grade 1C+], as well as therapy with i.v. gammaglobulin within 10 days of the onset of symptoms (Grade 1A).

Late results after mitral valve replacement with bileaflet mechanical prosthesis in children: evaluation of prosthesis-patient mismatch

BACKGROUND

Mechanical prosthesis is the choice of valve at the mitral position in children, although re-replacement of prostheses because of prosthesis-patient mismatch is almost inevitable when prostheses were implanted in small children. The methods to predict prosthesis-patient mismatch as a result of patients' somatic growth or pannus formation in children by noninvasive methods have not been well established.

METHODS

Thirty-two children underwent mitral valve replacement with 37 bileaflet mechanical prostheses (26 St. Jude Medical prosthetic valves, and 11 CarboMedics prosthetic valves) and were followed up a mean of 6.8 years (maximum 18.3 years) with a complete follow-up rate of 94%.

RESULTS

There were no operative deaths and 5 late deaths. Re-replacement of mitral valve because of prosthesis-patient mismatch was required in 5 patients. Freedom from valve-related events and re-replacement of mitral valve at 15 years were 32% +/- 23% and 54% +/- 18%, respectively. Actuarial survival rate was 63% +/- 19% at 15 years. Prosthetic valve orifice area index (manufactured geometric prosthetic valve area divided by patient's body surface area) was well correlated with maximum transprosthesis flow velocity estimated by Doppler echocardiography during follow-up, whereas valve orifice area index had no significant correlation with pulmonary artery wedge pressure assessed by cardiac catheterization. Maximum transprosthesis flow velocity had a significant correlation with pulmonary artery wedge pressure.

CONCLUSIONS

Valve orifice area index itself was not a reliable index to predict prosthesis-patient mismatch. Maximum transprosthesis flow velocity was a useful index to predict pulmonary artery wedge. Invasive cardiac catheterization to determine re-replacement of the prosthesis should be considered when maximum transprosthesis flow velocity exceeds 270 cm/s.

Mitral valve replacement for children with a small annulus using ATS open pivot prosthesis

OBJECTIVES

The present study was conducted to review our experience of mitral valve replacement (MVR) in small children with the ATS open pivot prosthesis.

METHODS

Between January 1999 and March 2002, 14 patients (7 males and 7 females) underwent a total of 15 ATS MVRs; 16AP in 9, 18AP in 3, and 20AP in 3 occasions. The mean age and body weight at operation were 1.1 +/- 0.7 (range 0.2 to 2.7) years and 6.8 +/- 2.6 (range 2.8 to 12.5) kg, respectively.

RESULTS

There were 2 early and 2 late deaths, each non-valve related. Excluding one patient, the orifice size of the prosthesis was larger than the predicted normal size of the mitral valve for the age. The postoperative Doppler echocardiogram demonstrated normal maximal flow velocity across the prosthesis. There was no morbidity among survivors except for the patient who developed a stuck and immobile valve disc 10.2 months after the operation and required re-replacement.

CONCLUSIONS

Our experience shows that MVR with the ATS open pivot prosthesis is a promising surgical option for small children.

Mitral valve replacement in children: mortality, morbidity, and haemodynamic status up to medium term follow up

OBJECTIVE

To investigate the outcome of mechanical mitral valve replacement in children after up to 11 years of follow up.

DESIGN

Retrospective analysis of case records. Operative survivors underwent echocardiographic studies to define current haemodynamic status and prosthetic valve function.

SETTING

Tertiary referral centre.

PATIENTS

All 54 children who underwent mitral valve replacement between January 1987 and December 1997.

RESULTS

30 day mortality was 20.3% and was associated with small valve size and supra-annular position. The actuarial freedom from the following events at five years (70% confidence interval (CI)) was: death, including 30 day mortality and transplantation, 68% (70% CI 62% to 75%); bleeding, 89% (70% CI 84% to 94%); non-structural valve dysfunction and reoperation, 92% (70% CI 87% to 97%). The incidence of endocarditis and thromboembolism was low and there was no structural valve failure. Event-free survival was 52% (70% CI 45% to 60%). Low weight, young age, and small valve size increased the chance of death or reoperation. On echocardiography, left ventricular dilatation and wall motion abnormalities were often observed. A high mean gradient over the prosthesis was associated with small valve size but not with length of follow up.

CONCLUSIONS

With the use of mechanical prostheses for mitral valve replacement in children, the problem of structural valve failure is no longer an issue. However, the procedure is still associated with a high complication rate, both at surgery and during follow up, and should therefore be reserved for patients in whom valve repair is not technically feasible.

Comparison of Ross procedures and aortic valve allografts in children

BACKGROUND

The Ross procedure is useful, but at times an allograft valve is the only alternative to a mechanical aortic prosthesis. Since 1994 the Ross procedure or aortic allograft replacement has been used exclusively for aortic valve replacement at our institution.

METHODS

Demographic, clinical, and echocardiographic data of 23 consecutive Ross and 8 allograft patients were compared.

RESULTS

Groups were similar in age and weight. The Ross group had fewer prior operations. There were no deaths or major complications in either group. The Ross group had no late complications of the autograft but 1 reoperation for pulmonary allograft stenosis. In the allograft group there was one reoperation for allograft insufficiency. Echocardiography was performed 2 to 11 days (mean, 4.3 days) after operation and 1 to 28 months (mean, 10.2 months) later. In the Ross group left ventricular wall thickness (mm) decreased from 11.0 +/- 2.3 to 7.8+/-1.7 (p < 0.0001), and left ventricular outflow tract maximal systolic velocity (m/sec) decreased from 1.9 +/-0.6 to 1.4+/-0.4 (p = 0.0001). In the allograft group left ventricular wall thickness (mm) decreased from 10.5 +/-2.6 to 9.0+/-2.6 (not significant), and left ventricular outflow tract maximal systolic velocity (m/sec) increased from 1.5+/-0.9 to 1.9+/-0.7 (not significant).

CONCLUSIONS

The Ross procedure results in significant improvement in left ventricular wall thickness and outflow tract velocity not seen in allograft aortic valve replacements. The Ross procedure remains the preferred operation for children requiring aortic valve replacement.

Guidelines for antithrombotic therapy in pediatric patients

Because of the relatively low incidence of TEs in children, the diagnostic and therapeutic approaches used are largely extrapolated from guidelines for adults. Features that differ in children compared with adults include underlying disorders, high incidence of CVL-related DVT in the upper venous system, and response to SH, warfarin, and thrombolytic agents. There is a paucity of information on the risk/benefit ratio of the therapeutic interventions and long-term outcome. Clinical trials are urgently needed to clarify optimal management for pediatric patients with TEs.

Late left ventricular function after surgery for children with chronic symptomatic mitral regurgitation

BACKGROUND

The use of quantitative echocardiography has been emphasized in optimizing timing of surgery in adult patients with mitral regurgitation to avoid irreversible left ventricular dysfunction. In contrast, surgery for infants and children is often delayed until the appearance of severe symptoms because of the patient's size and anticoagulation requirements and the possible need for early reoperation. The purpose of this study was to determine long-term ventricular function after mitral valve surgery in symptomatic children and to analyze risk factors for adverse outcome.

METHODS AND RESULTS

Thirty-three patients (0.5 to 19 years old) operated on for mitral regurgitation as a single hemodynamically significant lesion were studied. All but 3 had medically refractory symptoms. One patient died during surgery, and 32 were followed for 0.3 to 17.1 years (mean, 4.5 years). The mean preoperative left ventricular shortening fraction was 0.38+/-0.09. Successful mitral valvuloplasty or replacement was documented by long-term normalization of end-diastolic dimensions. Early postoperative shortening fraction was significantly reduced (0.28+/-0.1, P<.01), but it improved to 0.40+/-0.07 (P<.01) on late follow-up, at which time only 1 patient had ventricular dysfunction. Preoperative shortening fractions did not correlate well with early or late postoperative values (r=.18 and r=.31, respectively). Seven of 32 surviving patients had preoperative shortening fractions <0.33 (mean, 0.26+/-0.05) and 25 >0.33 (mean, 0.39+/-0.08). Analysis of these subgroups showed no significant differences between the groups in early or late postoperative function. Duration of mitral insufficiency appeared to be associated with the development of atrial arrhythmias.

CONCLUSIONS

Late left ventricular function normalizes in children after surgical correction of mitral insufficiency. In contrast to adults, delay of surgery in children with significant mitral regurgitation until the onset of severe symptoms does not increase the risk for long-term ventricular dysfunction, although late atrial arrhythmias are more likely to be encountered.

Comparison of human tissues and mechanical prostheses for aortic valve replacement in children

BACKGROUND

Aortic valve replacement in children is problematic because of complications of mechanical valves and uncertain outcomes associated with human valves. The results of pediatric aortic valve replacements over 5 years were reviewed.

METHODS AND RESULTS

Mechanical valves were used exclusively during the first part of this series (n = 26). Thereafter, 25 consecutive aortic valve replacements were performed with autografts (n = 19) or allografts (n = 6). Allografts were used for Marfan's syndrome patients or those with unusable pulmonary valves. Among autograft/allograft recipients, 16 patients underwent 27 prior operations. In the mechanical group, 18 patients underwent 19 previous operations. Three patients in each group underwent a previous mechanical aortic valve replacement. Operative complications included two mild strokes and one pacemaker in the autograft/allograft group and three deaths and two pacemakers in the mechanical group. One autograft recipient required reoperation for pulmonary allograft stenosis. In the mechanical group, late complications included six cases of nonstructural degeneration and two cases of endocarditis, with three reoperations. Reoperation-free survival was 96% at 2 years in the autograft/allograft group and 80% at 2 years and 75% at 3 years in the mechanical group. Event-free survival was 96% at 2 years in the autograft/allograft group compared with 67% at 2 years and 49% at 3 years in the mechanical group (P < .05).

CONCLUSIONS

The frequency of reoperations for mechanical aortic valve replacement has been surprisingly high. Aortic valve replacement in children with only autografts or allografts achieves good early results.

Anticoagulation in children with mechanical valve prostheses

BACKGROUND

Clotting complications in patients with mechanical valve prostheses can be prevented with either warfarin sodium (Coumadin; DuPont, Wilmington, DE) or antiplatelet agents. In children, it is not known whether one treatment regimen is more effective or safe than the other.

METHODS

We prospectively followed up 64 children and young adults (aged 18 years or younger at implantation) with a mechanical valve on the left side of the heart, from October 1986 through October 1996. Forty-eight patients were treated with Coumadin and 16 with aspirin and dipyridamole. The two groups were similar in age, sex, valve location and size, mean length of follow-up, and operative indication. There has been a total follow-up of 272 patient-years on Coumadin and 116 patient-years on aspirin and dipyridamole.

RESULTS

There was no difference between the two groups in survival or freedom from thromboembolism. Bleeding occurred more often in the patients taking Coumadin, but this difference was not statistically significant. Analysis of the literature showed thromboembolism and bleeding rates to be similar in the patients receiving Coumadin and those receiving antiplatelet agents.

CONCLUSIONS

Coumadin and the combination of aspirin plus dipyridamole provided similar protection against complications in this group of children and young adults with left-sided St. Jude (St. Paul, MN) mechanical valves. The choice between the two regimens may depend on other factors, such as patient preference and convenience.

Clinical course and hemodynamic observations after supraannular mitral valve replacement in infants and children

OBJECTIVES

We report the clinical course and unique hemodynamic findings after placement of a supraannular mitral valve prosthesis.

BACKGROUND

Children with symptomatic mitral valve disease whose annulus is too small for the smallest prosthesis are difficult to manage. One option is valve replacement with a prosthesis positioned entirely within the left atrium (LA).

METHODS

We reviewed 17 patients (median age 10 months) with symptomatic mitral valve disease who underwent placement of a supraannular valve prosthesis between 1980 and 1994.

RESULTS

The actuarial survival rates were 88% at 1 month and 71%, 62% and 53% at 1, 2 and 10 years, respectively. Preoperative hemodynamic data (mean +/- SD)) compared with those after placement of the supraannular mitral prosthesis were as follows: "a" wave to left ventricular end-diastolic pressure gradient 17 +/- 5 versus 4 +/- 4 mm Hg (p = 0.003), mean LA pressure 25 +/- 6 versus 20 +/- 6 mm Hg (p = 0.07), "a" wave 30 +/- 6 versus 19 +/- 5 mm Hg (p = 0.006), "v" wave 28 +/- 5 versus 30 +/- 9 mm Hg (p = 0.31), mean pulmonary artery pressure 54 +/- 19 versus 42 +/- 15 mm Hg (p = 0.07) and left ventricular end-diastolic pressure 14 +/- 5 versus 16 +/- 4 mm Hg (p = 0.12).

CONCLUSIONS

Supraannular mitral valve replacement provides relief of mitral stenosis or mitral regurgitation. However, LA to left ventricular early diastolic gradients with large atrial "v" waves contribute to elevated mean LA pressures in the absence of prosthetic valve obstruction or regurgitation. As a result of this unexpected finding, associated left heart obstructive lesions and pulmonary and left ventricular end-diastolic hypertension, the outlook remains poor.

Anticoagulation with warfarin in infants and children

OBJECTIVE

To provide a comprehensive review of warfarin use in infants and children, including recommendations for appropriate dosage and monitoring parameters.

DATA SOURCES

A MEDLINE search (1966-1995) was used to identify pertinent English-language articles in the medical literature. The key search term was warfarin. Additional material was obtained from references cited in articles retrieved through MEDLINE.

STUDY SELECTION

All articles involving children younger than 18 years were evaluated. In addition, articles on the pharmacokinetics and pharmacodynamics in adults, adverse effects, and drug interactions were included.

DATA EXTRACTION

Material selected for review included clinical trials, case reports, and surveys of practice.

DATA SYNTHESIS

Warfarin has been used as prophylactic therapy in children with prosthetic cardiac valves as well as for prevention of thromboembolic complications associated with autoimmune disorders and protein C or protein S deficiency. Warfarin also has been used to prevent embolization in children with deep-vein thrombosis or clots in central venous catheters. According to the literature, an initial dosage of 0.1 mg/kg/d should provide anticoagulation without significant adverse effects. As in adults, dosing should be adjusted to achieve a target international normalized ratio (INR). Although the target range in children is not well established, INR values of 1.5-3 are recommended for most patients. Higher values have been used in children with prosthetic cardiac valves and hereditary clotting disorders.

CONCLUSIONS

Due to its infrequent use, there is limited information on the effects of warfarin in children. Basic guidelines for initiating and monitoring warfarin were developed by using data gathered from clinical trials, retrospective reviews, case series, and surveys of practice.

Indications and drugs for anticoagulation therapy in children

The indications for using anticoagulants in children are reviewed. These include venous thromboembolic disease, thrombosis associated with central venous lines, inherited conditions, arterial thromboembolic disease and umbilical catheterization. The anticoagulants presently available for paediatric use consist of heparin and oral agents including low molecular weight heparin (LMWH). The problems associated with their use in children are examined and potential advantages described. Increasing numbers of children are now requiring anticoagulant therapy and the potential advantages of LMWHs makes it imperative that randomized, controlled trials be carried out in children in prophylactic as well as therapeutic situations.

Long-term follow-up of the St. Jude Medical prosthesis in pediatric patients

BACKGROUND

The St. Jude Medical prosthesis has become the most commonly used artificial heart valve, yet few data are available in the pediatric population. This study addresses results of the use of this prosthetic valve in pediatric patients over a 13-year time frame.

METHODS

From January 1982 through June 1994, 73 patients (49 male) underwent 75 valve replacements using the St. Jude Medical prosthesis at Minneapolis Children's Medical Center. Follow-up was complete in 71 patients, with a mean follow-up of 39 +/- 32 months (mean +/- standard deviation; range, 4 to 142 months).

RESULTS

Valves' positions were aortic in 36 patients, mitral or left atrioventricular valve in 34, tricuspid in 1, and double valve in 2. Patient age was 8 +/- 6 years, with a range of 1 week to 19 years. Sixteen patients were less than 24 months of age at valve replacement. Prior cardiac procedures had been performed in 82% of mitral patients, 58% of aortic patients, and all of the tricuspid and double-valve patients. Elective valve replacement was performed in 62 to 73 patients (85%). Seven patients (44%) less than 24 months of age had urgent valve replacement; 4 patients (7%) older than 24 months required urgent valve replacement. Overall early mortality was 8% (6 of 73); 36% (4 of 11) in the patients undergoing urgent valve replacement and 3% (2 of 62) in the elective group. All but one of the deaths were due to cardiac dysfunction. There were four late deaths, from 4 to 125 months postoperative, primarily caused by congestive heart failure or pulmonary vascular disease. Cumulative freedom from valve-related events was 93%, 85%, and 77% at 1, 5, and 10 years, respectively. Valve-related complications included thromboembolism (4), bleeding (5), perivalvar leak requiring reoperation (2), transient ischemic attack (1), and endocarditis (1). There have been no permanent strokes or mechanical malfunction. The majority of patients are currently managed with warfarin. Five surviving patients whose initial valve replacement was at age 24 months or younger have undergone repeat valve replacement (42%). Ninety-five percent of patients enjoy good health at follow-up.

CONCLUSIONS

The St. Jude Medical prosthesis offers correction of valvular disease with low morbidity and mortality, and excellent functional result.

Pulmonary autograft in children: realized growth potential

Pulmonary autograft replacement of the aortic valve has the potential to remain viable and grow in proportion to the somatic growth of the child. Changes in aortic annulus and sinotubular dimensions were compared early and late postoperatively, and related to normal. Eighty-six children, 0.9 to 21 years, were operated on between 1986 and 1993: 42 had a root replacement, 24 an inclusion cylinder, and 20 a scalloped subcoronary implant. Actuarial survival at 7 years was 96.5% +/- 2.0%. Freedom from reoperation for the pulmonary autograft or the homograft reconstruction of the right ventricular outflow tract was 92% +/- 4%. Freedom from reoperation on the autograft in root replacements was 96% +/- 4%, in the inclusion cylinder was 100%, and in the scalloped subcoronary was 90% +/- 7% (not significant). Aortic annulus and sinotubular junction diameters were compared with normal values predicted by body surface area. In 22 intraaortic implants, early and late postoperative annulus diameter mean Z values are in the normal range. In the 23 root replacements, early annulus diameter was within the normal range, but late Z values were larger than normal (p < 0.02). Intraaortic implant annulus diameter increased proportionally to somatic growth, but the sinotubular junction, which was small, remained small but increased toward normal. In the root replacements, the annulus increased in diameter and became dilated. The sinotubular junction, which was small early, increased and was within the normal range late. Lower operative risk and valve durability without failure suggest improved results with inclusion cylinder technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic valve prosthesis obstruction after aortoventriculoplasty: reconstruction with aortic allograft

An aortoventriculoplasty (Konno procedure) operation was performed for relief of tunnel-type subaortic stenosis using a Bjork-Shiley valve aortic prosthesis. The mechanical prosthesis thrombosed and cerebral embolism occurred when anticoagulant medication was stopped. The aortic root was successfully reconstructed with a cryopreserved aortic allograft using freehand implant technique. The cryopreserved aortic allograft is an excellent replacement device in the young adult patient in cases of failed prostheses, even in the presence of complex left ventricular outflow tract morphology or previous reconstruction operations.

Management of systemic atrioventricular valve regurgitation in infants and children

Since September 1979, 53 patients have required operation for systemic atrioventricular valve regurgitation at Children's Hospital and Health Center of San Diego. (Primary repairs of atrioventricular canal defects are excluded from this report.) Diagnoses include single ventricle, cardiomyopathy, congenital mitral insufficiency , Marfan's disease, rheumatic heart disease, and a history of prior repair of atrioventricular canal defect. Ages ranged from 4 months to 19 years; median age is 5 years. In 31 patients, the atrioventricular valve could be repaired. In 24 patients, the valve was replaced (including two patients previously repaired). There were four operative deaths, all in the valve replacement group: three following valve replacement, and one following emergency thrombectomy. Two early failures in the repair group required valve replacement. Techniques for repair included leaflet resection, commissural annuloplasty, ring annuloplasty, and chordal shortening. Follow-up reveals good-to-excellent status in 38 patients. There were seven late deaths: six following valve replacement (one death valve related). Current surgical technique permits repair of the systemic atrioventricular valve in many infants and children requiring operation for regurgitation. The long-term results of valve repair are good to excellent. Repair avoids the morbidity and mortality of valve replacement, e.g., anticoagulation, fixed orifice size, and catastrophic mechanical valve malfunction.

Replacement of the aortic valve or root with a pulmonary autograft in children

Between January 1967 and December 1988, 34 patients ranging in age from 3 to 18 years (mean, 14 +/- 3.6 years) underwent replacement of the aortic valve or root with their own pulmonary valve. The indication for operation was left ventricular outflow obstruction in 16 patients (47%), aortic regurgitation in 14 (41%), mixed aortic valve disease in 3 (9%), and failure of a previously implanted aortic homograft in 1 (3%). There were four early deaths, all before 1971, giving a hospital mortality of 11.8% (70% confidence interval, 6% to 20%). Surviving patients have been followed up a cumulative total of 214 patient-years, the longest period of observation being 16 years 8 months. Late mortality was 13.3% (70% confidence interval, 7% to 23%), and 4 other patients required removal of the pulmonary autograft for endocarditis. Actuarial rates at 16 years were 74% +/- 11% for freedom from reoperation on the left ventricular outflow tract, 80% +/- 10% for freedom from reoperation on the right ventricular outflow tract, and 77% +/- 10% for late survival. There was no instance of primary structural degeneration in the pulmonary autograft, and all surviving patients were in New York Heart Association functional class I without medication. This experience demonstrates that the pulmonary autograft can achieve good early and medium-term results in young patients. Should growth potential be realized, it might constitute the ideal biological valve for the left ventricular outflow in children.

Prosthetic valves in children and adolescents

The purpose of this paper is to present the short- and long-term results of prosthetic valve replacement in children. During a 7-year period that ended in April 1985, 186 children, ages 1 to 20 years, underwent valve replacement; there were 55 (30%) aortic valve replacements, 95 (51%) mitral valve replacements, and 36 (19%) multiple valve replacements. Ninety-four percent of the lesions were rheumatic in origin, 4% were congenital, and 2% were infectious. Of 223 valves replaced, 175 (78%) were mechanical valves and 48 (22%) were heterografts; the latter were in the mitral position in all but three patients. Surgical mortality rates were 3.6%, 4.2%, and 19.4% respectively for aortic valve, mitral valve, and multiple valve replacements. Five-year actuarial survival was 91% for aortic valve replacement, 82% for mitral valve replacement and 60% for multiple valve replacement. Major events included reoperation in 34 (with three deaths), progressive myocardial failure that led to death in 10, sudden unexpected death in two, thromboembolic complications in 19 (death in five), subacute bacterial endocarditis in five (two deaths), and bleeding that required transfusion in two patients. Five-year complication-free actuarial survival rates were 83% for aortic valve replacement, 63% for mitral valve replacement, and 57% for multiple valve replacement. The respective five-year complication-free survival rates were 83%, 48%, and 43%. Significant morbidity and mortality rates are associated with valve replacement. Therefore every effort should be made to preserve the native valve by plastic reparative procedures. When prosthetic replacement of mitral valve is contemplated, our data would suggest that heterografts should not be inserted in children 15 years of age or younger, although heterografts may be used in children over 15 years of age with the expectation of valve survival comparable to that of mechanical valves. When complications that are associated with anticoagulant therapy were reviewed, platelet inhibiting drugs seem quite satisfactory in patients with aortic valve replacement; patients with mitral valve replacement seem to require warfarin therapy, and warfarin must be used in patients with multiple valve replacement to reduce the risk of thromboembolic complications.

Ten-year results with the St. Jude Medical prosthesis

Although the hemodynamic characteristics and durability of the St. Jude valve prosthesis have been reported, the need for and the degree of anticoagulation in patients who receive these valves remain uncertain. Our 10-year experience with 165 patients (100 men and 65 women, mean age of 58 +/- 13 years), who underwent valve replacement with St. Jude prostheses, is reported. Of the 165 patients, 147 were treated with warfarin. A prothrombin time 1.3 to 1.8 times control (range 15 to 20 seconds) was maintained in 134 patients with single valve and 1.8 to 2 times control (range 20 to 25 seconds) in 13 patients with double valve prostheses. The 10-year actuarial event-free incidence from thromboembolic and hemorrhagic complications was 84 and 95%, respectively. Of the 8 patients receiving antiplatelet therapy alone, 4 had thromboembolic events. Of the 10 patients on neither warfarin nor antiplatelet therapy, 3 had thromboembolic events. The 10-year actuarial event-free incidence from valve failure was 95%. The 10-year actuarial patient survival was 55%. Thus, the St. Jude valve is a safe and reliable prosthesis with acceptable overall long-term performance in patients given a modest anticoagulation regimen. Patients who receive St. Jude prosthetic valves without anticoagulants have a high incidence of thromboembolic events despite therapy with antiplatelet agents.

Mitral valve replacement in the first 5 years of life

Between 1976 and 1986, 19 children aged 1 month to 5 years underwent replacement of the mitral (systemic atrioventricular) valve. Indications for valve replacement included isolated congenital mitral stenosis (n = 2), valve dysfunction associated with a more complex procedure (n = 15), and failed valvuloplasty (n = 2). Seven different valve types were used; nine were mechanical valves and ten were bioprosthetic valves. There were 6 hospital deaths (32%; 70% confidence limits, 20% to 47%). Among the 13 survivors there were 3 late deaths at a mean of 14 months after operation. The late deaths were unrelated to valve malfunction. Thromboembolic events occurred in 2 patients, both with mechanical valves. One minor bleeding complication occurred among 10 patients on a regimen of Coumadin (crystalline warfarin sodium). Five patients, all with bioprostheses, required a second valve replacement. Indications for reoperation included prosthetic valve regurgitation (n = 1) and calcific stenosis (n = 4). No early or late deaths occurred after second valve replacement. Survival was 51% +/- 12% (standard error) at 112 months after valve replacement. Analysis failed to identify age, weight, sex, previous operation, underlying cardiac lesion, or prosthesis size and type as significant risk factors for mortality. Mechanical valves had a lower reoperation rate compared with bioprostheses. These data suggest that although mitral valve replacement within the first 5 years of life is associated with a high operative and late mortality, satisfactory long-term palliation for many patients can be achieved. Mechanical valves are superior to bioprosthetic valves, and offer the best long-term results.

Late reoperation for systemic atrioventricular valve regurgitation after repair of congenital heart defects

Since 1979, 17 infants and children have undergone reoperation for systemic atrioventricular (AV) valve regurgitation 6 weeks to 7 years after repair of congenital heart defects. Prior operations were repair of incomplete or complete AV canal (14 patients), Mustard repair of complex transposition of the great arteries including ventricular septal defect closure (2 patients), or first-stage operation for hypoplastic left heart (1 patient). Age ranged from 6 months to 11 years. In 12 of the 17 patients (10, AV canal; 1, transposition; 1, hypoplastic left heart), valve reconstruction was possible. Operative techniques included a combination of septal cleft approximation, leaflet resection, commissural annuloplasty, or ring annuloplasty. There were no operative deaths, and there were no reoperations in the repair group. The condition of these patients has improved. Follow-up ranges from 1 month to 9 years (mean follow-up, 4.1 years). Five of the 17 patients (4, AV canal; 1, transposition) underwent valve replacement. There were no operative deaths. Follow-up ranges from 3 to 8 years. Three patients later underwent re-replacement of the prosthetic valve; there was 1 late death. The condition of all 4 survivors is improved. Substantial AV valve regurgitation can occur months or years after repair of congenital heart defects. A combination of reconstructive techniques may be useful in preserving native valve function and avoiding systemic AV valve replacement.

Anticoagulant therapy in children with prosthetic valves

The purpose of this study was to evaluate the effectiveness and complications of several types of anticoagulant therapy in children with prosthetic valves. During a 7-year period ending April 1985, 130 children aged 1 to 19 years underwent left-sided valve replacement. Operative mortality was 3%, 5%, and 9%, respectively, for aortic, mitral, and aortic and mitral valve replacement. Among the 123 survivors, 32 (26%) had had aortic, 71 (58%) had had mitral, and 20 (16%) had had aortic and mitral valve replacement. Follow-up ranged from 2 months to 8.2 years, a total of 544 patient-years. The survivors were divided into three groups based on anticoagulant treatment: warfarin sodium, aspirin plus dipyridamole, and no anticoagulants. Among the patients who had aortic valve replacement, thromboembolic complications developed in 2.5% (2.5/100 patient-years) of the aspirin plus dipyridamole group and 5% of the group given no anticoagulants. Only the warfarin group (4%) experienced bleeding complications. Among the patients having mitral valve replacement, thromboembolic complications developed in 4% of the warfarin group, 3% of the aspirin plus dipyridamole group, and 11% of the no anticoagulant group. In addition, 2% of patients in the warfarin group experienced severe bleeding. Two fatal cerebrovascular accidents occurred, both in the aspirin plus dipyridamole group. Patients who received a mitral heterograft were not prescribed any anticoagulant medications, and no thromboembolic complications developed. Among patients having double-valve replacement, complications developed in 5% of the warfarin group and 27% of the group given no anticoagulants.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary response to dynamic exercise after heart and combined heart-lung transplantation

The exercise capacity and cardiopulmonary response to progressive dynamic exercise of eight healthy recipients of heart-lung transplants were compared with those of matched recipients of orthotopic cardiac transplants and normal controls. In both transplant groups the maximum workloads were lower than that in the normal group. The transplant recipients had higher pre-exercise heart rates and lower maximum heart rates than the normal controls. Ventilation during submaximal exercise was similar in the heart transplant group and the controls. The heart-lung group had an increased ventilatory response associated with lower end tidal carbon dioxide concentrations. Exercise capacity after combined heart-lung transplantation is similar to that after cardiac transplantation. Transplant recipients have an abnormal heart rate response during exercise related to cardiac denervation. The altered ventilatory response in heart-lung recipients may be the result of pulmonary denervation.