الفهرس 
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Abstract
Although not free of complications, mitral valve replacement (MVR) provides a considerably better prognosis than could be expected according to natural history. About 70% of patients are alive without complications for at least 5 years after valve replacement (Kirklin et al 2003).
The aim of this work is to study the influence of MVR operation on the other hemodynamic clinical and echocardiographic parameters at an early (<30 d) and short term follow-up periods, and to record the possible complications.
This study included 36 patients with rheumatic mitral valve disease subjected to MVR operation ( with or without concomitant tricuspid valve {TV} annuloplasty and/or left atrial appendageobliteraton) at Assiut University Hospital and National Heart Institute in the period from January 2005 to February 2006.
All patients were subjected to clinical and echocardiographic evaluation preoperatively, early postoperatively and at 3- and 6- months postoperatively.
Preoperative and postoperative data were compared with respect to NYHA functional classification, heart rate and rhythm, right ventricular (RV) performance (including RV systolic pressure {PASP}, volumes and ejection fraction{EF} ), left atrial (LA) diameter and left ventricular (LV) performance (including LV dimensions, volumes and EF). LV performance was further assessed in relation to the type of mitral valve lesion detected prior to the operation.
Summary and conclusion
The artificial valves used were all bileaflet 3rd generation valves of which only 3 types were used, the St.Jude Medical prosthesis (being inserted in 11 patients), The Carbomedics bileaflet prosthesis (inserted in 3 patients, a number insufficient for statistical analysis) and the On-X prosthesis (used in 21 patients). The safety and the effectiveness of the 3 valves were evaluated and the St.Jude Medical and the On-X prostheses were compared for their clinical performance and incidence of complications during the 6-months period of follow-up.
Besides, the effective orifice area (EOA) was measured for each valve by transthoracic echocardiography, utilizing the classical method of continuity equation and was indexed for the body surface area (B.S.A). Prosthesis-patient mismatch (PPM) was defined as an EOAI ≤1.2 cm2/m2. Patients with moderate (EOAI ≤1.2 and >0.9 cm2/m2) and severe (EOAI ≤0.9 cm2/m2) were compared to those with nonsignificant degree of PPM as regard cardiac index (CI), LA size, time to peak velocity (TPV), PASP, and RV volumes and function, as well as transvalvular mean pressue gradients.
During the 6 months follow-up period, death occurred in 11 patients (30.5% of the studied population). 30-day mortality as well as late deaths included 5 patients each, (45.4% of total mortalities and 13.8% of the cohort of patients in the study). The overall morbidities were 20 (occurring in 47.2% of the study population). There was a statistically significant difference between the St.Jude Medical and the On-X bileaflet prostheses as regard valve-related adverse events (57% of the On-X group vs 9% of the St.Jude group). Paravalvular leakage had the highest prevalence among valve-related complications (16.6% of the whole cohort of patients), with a
Summary and conclusion
significant difference in its incidence between both types of prostheses (29% of the On-X group vs 0% in the St.Jude Medical group). Prosthetic valve thrombosis occurred also more frequently in the On-X group (19% of the On-X group vs 0% of the St.Jude medical group), despite the fact that the On-X prosthesis is formed of pure pyrolytic carbon which, in turn, should decrease its thrombogenicity. Thromboembolism, as a complication, occurred in one patient with PVT. Tissue ingrowth was detected in one patient with St.Jude medical prosthesis. But no mechanical obstruction of the effective orifice was denoted.
Clinical and Echocardiographic outcomes after mitral valve replacement:
The majority of patients were in NYHA class III or IV preoperatively, with significant improvement at the 3 and 6 follow up periods. However, no significant difference between the pre- and the early postoperative NYHA functional class was reported.
The number of patients with sinus rhythm increased postoperatively. 10 patients had sinus rhythm preoperatively. At the 3 months follow-up period 12 patients were reported to have sinus rhythm.
A statistically significant reduction in LA diameter was observed at the early, 3 month and 6 month postoperative follow up periods. The degree of reduction was more in patients with LAA obliteration than those without.
No significant difference between the preoperative and the postoperative echocardiographic derived RV dimensions and volumes, with a tendency to increase during the 6-month follow-up period. This finding was unexpected due to the presence of a statistically significant improvement
Summary and conclusion
in PASP and TPV (P-value ≤0.005), which make a reduction in the RV volumes during the follow-up period more likely.
According to the type of mitral valve lesion prior to surgery, the studied group were further classified into 3 groups: Group (1) included patients with mitral stenosis (MS), group (2) included those with mixed mitral valve disease, and group (3) included patients with pure mitral regurge (MR) lesion.
There was a statistically significant difference between the 3 groups as regard the pre- and the immediate postoperative LV dimensions and volumes.
For patients with pure MR and those with mixed mitral valve lesions, there was statistically insignificant reduction in LV end-diastolic volume (LVEDV) and end-diastolic dimension (LV EDD) early postoperatively. No change in LV end-systolic dimension (LV ESD) or End-systolic volume (LV ESV) was noted. This resulted in quite statistically significant reduction in mean values of EF (measured by either M-Mode or Simpson’s rule) in both groups, compared to preoperative values, with a statistically significant difference between the 3 groups detected early postoperatively.
For patients with isolated MS, there was a rise in LV EDV from a mean of 70.0 ± 23.6 ml preoperatively to a mean value of 75.3 ± 20.9 ml postoperatively. But, no significant change as regard ESV. This resulted in an increase in EF from a mean of 59.1 ± 12.5 % preoperatively to a mean of 62.8 ± 8.09 % early postoperatively.
For patients with MR, further reduction in LVEDD, LVESD, and LVESVs was noted at 3 months follow-up periods, compared to the
Summary and conclusion
immediate postoperative results. However, no change in LVEDV was detected. This resulted in further improvement of EFs (from a mean of 56.3 ± 13.9% early postoperatively to a mean of 60.3 ± 11.4% at 3 months follow-up period, when measured by M-Mode, and a mean of 43.667 ± 10.4% to a mean of 56.7 ± 4.04 % when measured by Simpson’s manoeuvre)
However, for patients with mixed mitral valve disease, there was no further improvement in LVEDV or LVESV at the 6 months follow-up period, compared to the early postoperative values. There was also an unexpected, statistically insignificant, increase in LVESV, compared to the preoperative data. This was consequently associated with a significant reduction in LV EF 6 months postoperatively. These results might be partly attributed to the techniques utilized during MVR in this group of patients, where partial chordal preservation and total chordal resection techniques were used.
For patients with MS, there was a statistically insignificant, persistent rise in LV EDD, ESD and LV volumes during the 6 months follow-up period. EF measured by M-Mode declined from a mean of 66 ± 6.93% preoperatively to a mean of 62.5 ± 7.37% 6 months postoperatively. But, EF, measured by Simpson’s rule, remained unchanged.
Impact of effective orifice area indices (EOAIs) on other clinical and echocardiographic derived variables:
Patients with moderate/severe PPM acquired higher values for PASP and lower values for TPV at the early follow-up periods. But 3 and 6- month follow-up periods, patients with severe PPM showed highest values for PASP and lowest values for TPV than those with moderate/insignificant PPM.
Summary and conclusion
As for right ventricular volumes and function, mean right ventricular end-diastolic dimension and volume were greater in patients with severe degree of PPM than those with moderate and clinically insignificant degree of PPM. . However, no difference was found as regard RV ESV or EF among the 3 groups.
Patients with severe PPM were also reported to have higher mean values for LA diameter, and lower values for CI, compared to those with moderate and clinically insignificant PPM.
However, no significant difference between the 3 groups as regard transvalvular mean gradients, at either stage of follow up was detected.
In the end, we conclude the following;
1) Despite improvement in myocardial handling techniques, myocardial protection and mitral valve replacement procedures in the recent years, 30-day and late mortalities and morbidities are higher in our locality compared to other recent studies, in other localities.
2) As regard the safety and effectiveness of the St.Jude Medical and the On-X bileaflet prostheses. The St.Jude Medical prosthesis showed much more effectiveness and durability than the On-X type, with a more incidence of valve-related complications in the On-X group, especially for clinically significant paravalular leakage, and thrombotic complications. 3) For normal survivors, there is usually marked improvement in functional capacity, LA diameter and RV pressure. But no improvement in RV volumes or EF was detected in this study.
Summary and conclusion
4) For patients with MR and mixed mitral valve disease, LV end-diastolic parameters and LV EF tend to decrease immediately posoperatively. Further decline in LV volumes should continue overtime, with a much more improvement in LV EF, unless conventional or partial chordal preservation methods of MVR are used.
For patients with MS, a significant increase in LV end-diastolic volume, early postoperatively, usually occurs. This increase in LV volumes might continue overtime, partly due to increased preload.
5) EOAI is an important determinant of the hemodynamic performance of valve prostheses. Patients with severe PPM have lower values for CI, as well as higher values of LA diameter and right ventricular volumes, dimension, and systolic pressure.
Limitations of the study:
1) Non homogenous population of patients, and it has been better to use a merely one type of preoperative mitral valve lesion.
2) Small numbers of groups in the study.
3) The use of three types of different bileaflet prostheses.