Abstract

Aims and Objectives: To evaluate the indications for uses of homografts in cardiac patients at srijayadeva institute of cardiac sciences & research and their follow up.

Methodology: Patients who received homografts in last two years (2012 to 2014) were included in this study. Homografts used  in the  study  group,  were  processed,  preserved  and thawed according to  protocols at our  institute’s  tissue valve bank. Prospective data was collected for all cases from 1.8.2012 to 31.7.2014 in all surgical units at Sri jayadeva institute of cardiac sciences and research Bangalore and followed up postoperatively for evaluation by clinical and echographic assessment for 6 months of duration. Homograft heart valves were retrieved from non beating heart donors, usually from cadavers during postmartum. Surgeons collected the heart using aseptic precaution, with sterile instruments. A piece of tissue from aorta and pulmonary artery were collected for culture into sterile container. Heart with great vessels transported in sterile double bags over ice from mortuary to our institute’s homograft valve bank. Heart was kept immersed in “Hank’s balanced salt solution” (HBSS) with antibiotic at 4⁰ C, till dissection. Dissection of valve and conduit was done at earliest possible time. Homografts were kept moist during dissection by irrigation with HBSS. The coronary arteries were ligated and cut. Each valve was kept in 200 ml of HBSS with antibiotics and incubated for 72 hours at 4⁰ C. The valves were transferred into fresh HBSS with antibiotic solution .After 72 hrs of sterilisation homograft valves were prepared for freezing, under sterile conditions. Aortic and pulmonary valve were packed separately in cold HBSS (90 ml) and 10 ml of DMSO (dimethyl sulphoxide) solution. After the freezing cycle for 1^1/₂  hours the valves were stored in vapour phase of liquid nitrogen between - 120 ⁰ C to  – 180⁰ C.The required valve was sent to operation theatre in cryo shipper maintaining the temperature below - 100⁰C.The fast thawing procedure was used. Outer cover of cryobag was cut open and inner cover was handed over to the scrub nurse. The valve was rinsed for 5 to 10 minutes with sterile water at 40⁰ C. After that second and first bags were cut open and valve transferred into HBSS with DMSO 5% Solution for 5 min rinse time, followed by two rinses in plain HBSS.

Results: Total of 23 patients had received homograft, from 1.8.2012 to 31.8.2014 at our institute. 3 patients were died in perioperative period, hence excluded from the study.

Out of 20 live patients,13 (65%) were males and 7 (35%) female. The disease distribution was 17 (85%) cases out of 20 live patients were operated for a congenital disease (including bicuspid aortic valve). Rest 3(15%) cases were operated for rheumatic and degenerative heart diseases.3 out of the 23 patients died in our study. Two due to low cardiac output, in immediate perioperative period  (< 48 hrs ) and one due to renal dysfunction followed by Multi organ dysfunction (MODS) in late postoperative period ( at 45 days). These patients were excluded from the statistical analysis pertaining to valve dysfunction. Pulmonary homografts were used in 13 (65%) patients and aortic in the other 7 (35%) patients with size ranging from 18- 24 mm (mean – 20.45 mm). Mean size of aortic homografts used is 19 mm while that of pulmonary homografts was 21.23 mm. Pulmonary homografts were mainly used in pulmonary circulation (10 cases). Only in 3 cases they were used in aortic position. Aortic homografts were used in both aortic (3 cases) and pulmonary position (4 cases).Most (12) of the homografts used (60%) were cryopreserved for a period of less than 3 months. 25% (5) were preserved for 3-6 months and 15% (3)were older than that (>6 months). Of the 20 patients, 3 had homograft valve dysfunction in the post operative period- 2 were associated with homograft valvar regurgitation and 1 with homograft valvar stenosis (increased gradient). All 3 patients presenting with complications had homografts which were cryopreserved for less than 3 months with valve sizes 22-24 mm. Homograft pulmonary valve was used in all 3 cases, one in pulmonary and two in aortic position. Hence cryopreservation time, for implanted homografts, is not significantly associated with homograft dysfunction. Also, position of implanted pulmonary homograft (aortic / pulmonary) was statistically analysed in relation to homograft dysfunction using chi square test. Hence pulmonary homografts used in aortic position were related to significantly higher homograft dysfunction rate. In case of aortic homografts , 3 were used in aortic position and 4 in pulmonary position. However, none of these patients, developed homograft dysfunction/ complications. Probably, a larger series of patients or longer follow period is required to analyse the same.

Conclusion: Cryopreservation time was not significantly associated with homograft dysfunction. The use of pulmonary homografts in aortic position was associated with significantly higher complication and homograft dysfunction rate. The homograft valve is the best substitute and suited to Indian population. In cases of endocarditis of the native or mechanical prosthetic valve in the aortic position with coexisting abscesses of the ascending aorta, the implantation of a homograft is lifesaving. Logical use of homografts in adult and paediatric cardiac surgery when indicated with the proper surgical technique ensures a very good postoperative result and an excellent quality of life for the patient.