Predicting the performance of mitral prostheses implanted in children under 5 years of age

Mitral valve replacement (MVR) is occasionally indicated in infants and young children, necessitating the use of small prostheses. The performance of these small valves during somatic growth of the patient can lead to patient-prosthesis mismatch. This study examines performance of these valves over time to establish predicted performance and timing of replacement.

Records were reviewed of all patients under 5 years of who underwent small mechanical MVR between 1988 and 2004 (n=24). Valve sizes were between 17 and 23 mm (Bileaflet 91.6%, Tilting Disc 8.3%) with a median size of 19 mm. Mean age of patients was 1.4+/-1.3 years with a mean weight of 7.8+/-3.4 kg.

Early deaths (n=5, 20.8%) were excluded. There were two late deaths and five patients required redo-MVR: four for outgrowth and one for acute thrombosis at 3 months. Age at redo for outgrowth was 8.6+/-6.6 years with mean body weight of 22.5+/-17.5 kg. Mean time between original operation and redo was 8.6+/-6.1 years in these four patients. Follow-up was a median of 7.5 years (range 0.1-15.7 years). Overall freedom from death or valve replacement was 82.6+/-9.1% at 5 years and 75.7+/-10.6% at 10 years. The performance of the original prostheses showed a peak blood flow velocity across the valves of 1.5+/-0.6 m/s at 5 years and 2.2+/-0.5 m/s at 10 years. Seventy-five percent of the survivors still have their original valve at a mean of 8.1+/-4.4 years postoperative with New York Heart Association status of I or II. Actuarial curves suggest that gradients across the valves reach a peak of >10 mmHg at a mean between 6.5 and 7 years postoperative.

MVR in children under 5 years carries a high mortality. Nevertheless, small mechanical MVR perform remarkably well in young children with durable haemodynamics despite growth of the patients well beyond more than double the initial bodyweight. Valves can be expected to last over 8 years before requiring re-replacement.