Title : Comparison of left ventricular myocardial interstitial fibrosis in two groups of patients with rheumatic mitral valve stenosis (Wilkins score <8 vs >10) and their early post-operative outcome
Abstract:
Background: A prospective comparative study was conducted at our institution comparing the left ventricular myocardial interstitial fibrosis in two groups of patients with Rheumatic mitral valve stenosis (Wilkins score <8 vs >10) analyzing the ventricular tissue biopsy and their early post operative outcome after mitral valve replacement.
Methods: A total of 40 patients with the diagnosis of severe mitral stenosis were included in this study with 20 subjects in Group 1 (Wilkins Score < 8) and 20 others into Group 2 (Wilkins Score >10). Primary outcome was to quantify the degree of left ventricular intra-myocardial fibrosis, cardiac indices, and inotropic scores. Secondary outcomes were new onset arrhythmias, lactate levels, duration of mechanical ventilation, intensive care unit and hospital stay.
Results: The 2 groups were comparable. The average age in Wilkins Score <8 (Group 1) and Wilkins Score >10 (Group 2) was 33.65±4.97 and 35.25±5.39 years respectively. Out of the total study subjects, 80% in Group 1 and 85% in group 2 were female and the rest were males. Out of total 20 patients in Group 1, in the anterior left ventricular wall biopsy, 17 had Grade 1 myocardial interstitial fibrosis, and 3 had Grade 2. In the posterior left ventricular wall biopsy sample, 2 had Grade 1, 17 had Grade 2 and 1 had Grade 3 myocardial interstitial fibrosis. In the myocardial biopsy taken form interventricular septum from the left ventricular side, 2 had Grade 0, 17 had Grade 1 and 1 had Grade 2 fibrosis. Out of total 20 patients in Group 2, in the anterior left ventricular wall biopsy 9 had Grade 1 myocardial interstitial fibrosis, and 11 had Grade 2. In the posterior left ventricular wall biopsy sample, 1 had Grade 1, 7 had Grade 2 and 12 had Grade 3 myocardial interstitial fibrosis. In the myocardial biopsy taken form interventricular septum from the left ventricular side, 2 had Grade 1, 12 had Grade 2 and 6 had Grade 3 fibrosis.
The myocardial fibrosis grading was significantly higher in Group 2 at all the three biopsy sample sitesof the left ventricle (p<0.05). The primary endpoint of Cardiac index measured noninvasively using ICON monitor was 4.56 ± 0.55 L/m2 in Group1 while in the Group 2 it was 4.03 ± 0.43 L/m2 (p-0.002) at shifting to ICU (0 hour). At 6th hour of postoperative period, it was found to be 4.66 ± 0.44 L/m2 in Group 1 and 4.08 ± 0.56 L/m2 in Group 2 (p-0.001). At 24 hours, it was found to be 4.96 ± 0.09 L/m2 in the Group 1 while in Group 2 it was 4.56 ± 0.58 L/m2 (p-0.004). The one-way Analysis of Variance Test showed that this difference was statistically significant at all the three instances measured.
There was a constant decrease in the Inotropic score from POD 0 to POD3. The mean IS from POD 0 to POD 3 in Group 1 were 8.45 ± 1.43, 5.50 ± 1.32, 2.30 ± 1.22 and 0.15 ± 0.36 respectively while in Group 2 it measured 13.10 ± 3.91, 14.00 ± 9.34, 8.40 ± 5.55 and 1.50 ± 2.06, respectively. The one-way Analysis of Variance Test showed that the inotropic score was more in Group 2 and was statistically significant at all the four instances measured (p<0.05). Intraoperative parameters like aortic cross clamp time were less in group 1 (p-0.014) but the CPB time (p-0.13) were comparable between the 2 groups. The serum lactate levels were significantly higher in Group 2 compared to Group 1 at 0 and 2 hours after shifting to ICU (p<0.05). However, the same was slightly higher in Group 2 at 6,12 and 24 hours but statistically insignificant.
Duration of mechanical ventilation was 4.25 ± 1.94 hours Group 1 vs 7.70 ± 2.18 hours in Group 2 (p<0.001). Similarly, the ICU stay in Group 1 and 2 were 1.35 ± 0.49 days and 2.05 ± 0.76 days respectively (p<0.001). The over all hospital stay in Group 1 was lesser but not significant statistically (6.70 ± 1.08 vs 7.55 ± 1.85 days (p-0.084)).
Conclusion: The amount of left ventricular myocardial fibrosis, as measured by myocardial biopsy, is linked to postoperative complications following mitral valve surgery in patients with rheumatic mitral stenosis. Greater myocardial fibrosis is associated with a higher risk of postoperative complications after mitral valve surgery. However, these findings require further validation through larger studies.
