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Ann Thorac Surg 2000;70:285-287
© 2000 The Society of Thoracic Surgeons
a Department of Pediatrics, Harefield Hospital, Middlesex, United Kingdom
b Department of Cardiothoracic Surgery, Harefield Hospital, Middlesex, United Kingdom
Address reprint requests to Dr Onuzo, Department of Pediatrics, Harefield Hospital, Hill End Rd, Harefield, Middlesex UB9 6JH, United Kingdom
e-mail: o.onuzo{at}rbh.nthames.nhs.uk
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Abstract |
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months and 2 months later, successfully underwent heterotopic cardiac transplantation in combination with partial left ventriculectomy. The benefits of combining both procedures in such a young infant particularly with regard to containment of early graft dysfunction, reduction of respiratory problems, and weight mismatch are discussed. |
Introduction |
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months underwent HCT in combination with PLV for dilated cardiomyopathy. To our knowledge, this combination of cardiac surgical procedures has not been reported in an infant.
The patient was first seen at age 3 months with a 5-day history of respiratory distress. She was found to be in congestive heart failure. A diagnosis of dilated cardiomyopathy was established at echocardiography. She required ventilation and intravenous inotropic support for resolution of the heart failure but remained ventilator dependent. In addition, she was found to have right renal agenesis with left horseshoe kidney, early nephrocalcinosis, and recurrent urinary tract infection. Renal function was normal.
At the age of 4 months, the patient was transferred to our unit. She weighed 6.6 kg, required ventilation, and was on a regimen of milrinone lactate, phentolamine, dopamine hydrochloride, furosemide, and spironolactone. Blood gases were normal on admission, and she was in hemodynamically stable condition. Full blood count, electrolyte study, and liver function test results were unremarkable. The values for blood urea nitrogen and serum creatinine were 9.1 mmol/L and 68 µmol/L, respectively. Echocardiography confirmed the diagnosis of severe dilated cardiomyopathy with no measurable fractional shortening (FS). The right side of the heart was compressed by the grossly dilated left side. Enoximone was substituted for milrinone, and aminophylline was added. The patient remained in stable condition and was successfully extubated 4 days after admission. Thereafter, the medications and echocardiographic findings remained unchanged until HCT was performed 20 days later.
The donor heart was from an anencephalic infant weighing 3.0 kg. The surgical technique has been previously described for children in our unit [2]. Partial left ventriculectomy of the recipient heart was performed at the same time. The left ventricular diastolic dimension was reduced to about 75% of its preoperative size (37 mm to 27 mm).
The patient was first extubated on the seventh postoperative day but required intermittent periods of nasal continuous positive airway pressure until the first episode of rejection on postoperative day 13. Rejection was diagnosed by echocardiography, as biopsies are not routinely done in our practice in small children. Her condition subsequently deteriorated, and she required full ventilation for 4 more days followed by nasal continuous positive airway pressure for 2 weeks. Because of initial deterioration in renal function, peritoneal dialysis was performed for 24 hours on the third postoperative day. No other problems were encountered, and renal function has remained normal (current creatinine level, 44 µmol/L). Immunosuppression was started and maintained using oral cyclosporine and azathioprine. Cyclosporine was titrated to achieve a 12-hour trough level of 300 to 350 ng/mL for the first postoperative week with a decrease to 200 to 250 ng/mL at the end of the first month.
Initially the donor heart functioned very poorly with an unmeasurable FS, whereas the recipient heart had vastly improved function (FS, 0.41). Synchronized sequential pacing of both hearts was tried but was unsuccessful. By the end of the first postoperative week, the donor heart had partially recovered (FS, 0.22) with progressive improvement thereafter except during an episode of rejection on postoperative days 13 to 15. The function of the recipient heart, on the other hand, deteriorated between postoperative weeks 6 and 25 before returning to normal. The donor heart retains slightly better function (current donor heart FS, 0.41; recipient heart FS, 0.33). The size of the recipient heart has remained small (left ventricular diastolic diameter, 37 mm before transplantation; 25 mm currently).
At 12 months after operation, the patient remains clinically well, is feeding normally, and is gaining weight adequately. She has had no further episodes of rejection with an acceptable cyclosporine level.
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Comment |
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The decision to perform HCT in our patient was based on weight mismatch. Orthotopic cardiac transplantation is not recommended when the weight of the donor is 75% or less than that of the recipient [5] and when performed under these conditions, tends to result in poorer outcomes in our experience. The weight of the donor compared to the weight of our patient was approximately 50%. The appeal of performing HCT plus PLV in a small infant lies mainly in the creation of an increased intrathoracic space to accommodate the donor heart without interfering greatly with lung function. Using this combination, we were able to perform HCT in a critically sick infant who might otherwise have died while awaiting a suitably sized orthotopic donor. We have not experienced any unusual problems with ventilatory support, and our patient was initially successfully extubated on postoperative day 7.
Moreover, the combination of HCT and PLV proved beneficial, as the improved left ventricular function of the patient’s own heart supported the circulation satisfactorily at the time of severe donor heart dysfunction in the early postoperative period. This is in contrast to what we usually see; the recipient left ventricle after HCT continues to function poorly, and quite often there is progressive dilation because of retrograde flow across the aortic valve. This can lead to thrombus formation with the attendant risk of systemic embolization. This has happened in 1 of our patients.
We can only speculate as to the reasons for the poor function of the donor heart in our patient. Perioperative ischemia of the donor heart is a well-known cause of early postoperative graft failure. However, the time of ischemia in our patient was less than 60 minutes, as the organ was harvested in an adjoining theater. Acute rejection is unlikely in view of the fairly speedy recovery without enhanced immunosuppressive treatment.
There is another factor intrinsic to the combination of HCT and PLV that could lead to early postoperative donor heart dysfunction. After isolated HCT, the donor left ventricle usually ejects blood into the recipient aorta, which receives very little blood from the failed recipient left ventricle. Postoperatively, the recipient left ventricular function may markedly improve, as in our patient, to the point where the donor left ventricle can find it difficult to eject blood against the flow from the recipient heart unless their function is synchronized. This functional synchrony can be accomplished by sequential pacing of both hearts so that the donor heart ejects during the diastole of the recipient heart [6]. We failed to achieve this because of the fast heart rate of both hearts (greater than 150 beats per minute) with a very short diastolic interval, which made sequential pacing of both hearts impossible.
Medium-term to long-term benefits of the concomitant use of HCT and PLV remain to be seen. If the underlying pathologic process affecting the recipient heart is progressive, the patient’s survival will depend on the function of the donor heart. It is not clear why the recipient left ventricular function deteriorated for a period. However, in both size and function, it remains improved from preoperative values. Therefore we are optimistic about its ability to support the patient’s circulation in the event of a new episode of rejection of the donor heart.
In conclusion, we have shown that the combination of HCT and PLV is feasible in a small infant with dilated cardiomyopathy and this widens the donor pool. It may avoid some of the early postoperative complications related to lung compression and temporary donor heart dysfunction that are encountered in small infants. It may also provide a safe clinical model for the study of medium- and long-term outcome of PLV in the treatment of end-stage heart failure in the pediatric population. However, we consider these procedures experimental, and a prospective study limited to institutions well versed in both operations seems prudent.
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