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Mitral Valve Replacement in Fifth Decade : Still a High Risk Proposition?
Kaushalendra Singh Rathore, Pawan Kumar, Uday Jadhav, Anil G Tendolkar
 

Abstract

Background : More often than past, now we are getting elderly Rheumatic mitral patients. The purpose of this study is to provide the insight of improvement in morbidity and mortality in these patients, if they’re any.

Material and Methods : This retrospective study includes 105 patients of 50 years or more of age. 75 underwent mechanical valve replacement and remaining received bioprosthetic valve. Data collection done from medical record section and OPD registers. Follow-up done with Transthoracic 2D Echocardiography supported with clinical parameters and X-ray findings.

Results : Mean age was 58.52 ± 2.4 years. Follow-up period ranges from one to eleven years (Mean 6.8 ± 0.9 years). Immediate perioperative mortality 5 patients (4.76%) and long term mortality includes 3 patients (3%). 35 patients previously underwent procedures like closed and open commissurotomy and Balloon valvotomy. Multivariate analysis showed age, redo surgery, atrial fibrillation, tricuspid valve disease, and preoperative functional status as incremental risk factors. Freedom from reoperation at 3 and 6 years was 90% and 85% in more than 60 years age group. Actuarial survival at 4 and 6 years of follow up was 94.24% and 88.52% respectively.

Conclusion : With the improving life expectancy and early interventions, rheumatic valvular disease patients more than 50 yeas are increasing. Definitive betterment is seen in this subset of patients in our study. Although age still remains the main risk factor along with atrial fibrillation, redo surgery, stroke, tricuspid valve disease.

 

Introduction

Rheumatic valvular disease is leading cause of morbidity and mortality faced by this subcontinent. Although many studies have examined the association of age with variation in clinical presentations, co morbid conditions, treatment and its impact on mortality in other cardiovascular disease,1-3 such investigations do not have good number of mitral valve operation. The presentation of rheumatic valvular disease varies from adolescent age to elderly patients. The presentation patterns may be different but inherited severity of pathology is definitely more in both of these groups. Still no cutoff for “Elderly” has been described, but for degenerative valvular diseases age more than 65 years is mentioned by few authors.4 Being rheumatic population in consideration 50 years and above is considered as elderly. Most of the patients in different surgical series comprises young adult population (20 to 35 years). Various factors like chronic disease, atrial fibrillation, multiple valve involvement etc. make rheumatic mitral valvular lesions in elderly a high risk procedure.5 Those studies that have shown age to be an important predictor of mortality after valve operation are unclear as to whether it is related to the intrinsic effect of aging per se or is related to the age-related differences in baseline characteristics, co morbidities, or therapeutic approaches.6 This retrospective study analyze different factors responsible for inferior results in elderly patients. Apart from age we have tried to illustrate other co morbid reasons in these subset of patients.

Material and Method

Patients characteristics : This is a retrospective study of 105 patients. Patients included were of age 50 years or more, operated in our institute over period of seven years. 75 patients underwent mechanical valve replacement and remaining received bioprosthetic valve. All patients of isolated mitral valve surgery with or without tricuspid repair were included. Patients requiring other valvular replacement, coronary surgery, aortic surgery were not included. This is because the morbidity and mortality of multivalvular disease differ from isolated lesions, as they are the predominant lesions in our subset. Coronary angiography done in all patients irrespective of presence or absence of risk factors. Aortic valve involvement was considered to be rheumatic in origin.

Surgical Technique : Median sternotomy, standard cardiopulmonary bypass technique with membrane oxygenator was used. Moderate hypothermia applied in all cases. Myocardial protection was done with cold ante grade blood cardioplegia through aortic root. Tilting disc and bileaflet valves were used for mechanical group (St Jude medical and Medtronic valves). Both methods of valve suturing were used that is, interrupted 2.0 pledgted ethibond and semicontinuous 2.0 polypropylene sutures. Anterior Mitral leaflet was excised completely, post leaflet preserved completely. Only excessive tissue on posterior leaflet was shave off. Calcium on posterior leaflet was nibbled out and complete posterior sub valve preserved. Dopamine was preferred inotropic drug. St Jude Medical bioprosthetic valve used in all cases of bioprosthetic valve.

Statistical analysis : Data collection done from medical record section and OPD registers. Follow-up done with Transthoracic 2D Echocardiography supported with clinical parameters and X-ray findings. Transthoracic 2D Echocardiography Performed at the time of discharge, then yearly during the follow up. Patients were studied with Transthoracic imaging using a 5 or 7.5 MHz transducer interfaced with a Hewlett-Packard Sonos 5500 echocardiography system. Statistical analysis was done with SPSS Ver. 10 software. Patient characteristics, operative details, and unadjusted outcomes for each age category were tabulated as frequencies and percentages for categorical variables, mean and standard deviation, or median and interquartile range for continuous variables. Significance was determined at a p value of < 0.05. All p values are two sided and confidence intervals are 95%. Overall survival (cardiac-and noncardiac-related deaths) was determined by the Kaplan-Meier method. Multivariate correlates of in-hospital survival were determined by logistic regression and correlates of long-term survival by Cox model.

Long-term anticoagulation with warfarin was used in all mechanical valves but only in the presence of chronic atrial fibrillation with a large atrium in patients who received a bioprosthetic valve.

Definitions

Definitions are considered from the guidelines given by LH Edmunds et al for valvular heart disease surgery reporting.7

Mortality : Hospital mortality was defined as death within any time interval after operation if the patient is not discharged from the hospital. Thirty-day mortality is death within 30 days of operation regardless of the patient’s geographic location.

Morbidity : Structural valvular deterioration : Any change in function of an operated valve resulting from an intrinsic abnormality of the valve that causes stenosis or regurgitation.

Nonstructural dysfunction : Any abnormality in stenosis or regurgitation at the operated valve that is not intrinsic to the valve itself. Dialysis, prolonged ventilation (> 48 hours), reoperation for bleeding, or deep sternal wound infection.

Valve thrombosis : Any thrombus in absence of infection attached or near the valve.

Embolism : Any emboli in absence of infection after immediate perioperative period.

Operated valvular endocarditis : Any infection involving an operated valve.

Reoperation : Any operation that repairs, alters, or replaces a previously operated valve.

Low Cardiac Syndrome : Postoperative low cardiac output syndrome was defined as need for positive inotropic agents or intra aortic balloon pump for more than 24 hours.
Perioperative myocardial infarction was defined as appearance of new Q waves with rising cardiac enzyme levels. Respiratory failure was defined as mechanical ventilation of more than 48 hours. Postoperative renal failure defined as serum creatinine more than 2 mg/dl.8

Results

Patient Profile : Study includes 105 patients. Age ranges from 50 year to 66 years (58.52 ± 2.4 years). Two groups are made on age (Group I < 60 years, Group II > 60 years). Weight ranged from 45 to 71 kg (mean 55 kg). BSA ranged from 1.1 to 1.8 (mean 1.5). 80% presented with DOE class III on medication out of 105, 75 (71.42%) given mechanical valve, remaining bioprosthetic valve. Follow-up ranges 1 year to 11 years (6.8 ± 0.9 years). The demographics and operative characteristics of the 105 patients undergoing mitral valve replacement are shown in Table 1. Preoperative and operative data is given in Table 2 and 3 respectively.

 

Out of 105 patients, 15 were post closed mitral commissurotomy, 12 post open mitral commissurotomy, 3 post balloon mitral valvotomy, 5 post mitral valve repair, 15 post closed mitral commissurotomy patients presented after mean follow-up of 8.72 ± 2.43 years. (13 years to 3 years of range), 12 post open mitral commissurotomy patients presented after mean follow-up of 6.21 ± 1.24 years (9 years to 3 years of range), 3 post balloon mitral valvotomy presented after 5.32 ± 2.11 years (7 years to 2 year of follow-up) and 5 post mitral valve repair presented 8.88 ± 3.42 years (10 years to 5 years of range). Preoperatively 48 patients were in atrial fibrillation (45.71%), remaining 57 in sinus rhythm (54.28%). Atrial fibrillation was statistically significant in group II patients (< 0.05).

Immediate postoperative course : Out of 48 years 35 (72.91%) remained in atrial fibrillation after the surgery. Four were in variable rhythm of junctional, sinus and atrial fibrillation. Rest five patients were in sinus rhythm and were of group I. Dopamine was preferred inotropic drug. Preoperative data is given in Table 4.

Mortality
: Immediate perioperative mortality 5 patients (4.76%), one had intracranial bleeding and 4 was in low cardiac output. One patient was in group I while all other four patients were in group II. Long term mortality: 3 patients (3%), one after 4 years of follow-up, 2 at 6 years of follow-up, two patient died of mechanical valve because of thromboembolic episode (Linearized rate of 0.1 events per 100 patients-years), one died after 6 year of follow-up in chronic congestive failure. All three patients were of group II.

Low Cardiac Syndrome
: Eight patients had postoperative Low cardiac output syndrome. Four responded to Dopamine support needed for 72 hours, resulted in long ICU stay. Other four required high doses of Adrenaline; eventually died; out of them 3 patients were of group II.
Actuarial survival at 4 years of follow up was 94.24%, at 6 years of follow up 88.52%. Freedom from reoperation at 3 and 6 years was 90% and 85% in bio prosthetic valve replacement group. Multivariate analysis showed age, redo surgery, atrial fibrillation, tricuspid valve involvement, preoperative functional status as incremental risk factors.

Discussion

Severe valvular lesions requiring surgery in elderly patients becoming more and more common, in western population more than 30% patients with age of 70 years are coming for surgery.1 Their elderly group mostly has aortic stenosis, mitral regurgitation due to mitral valve prolapse. In our subset mitral valve lesions are rheumatic in aetiology. According to the population reference bureau’s 2000 World data sheets, life expectancy at birth for Indian is between 60 and 61 years. Only 4% of our population is over the age of 65%. So we considered lower range of 50 years in this study.

Mitral valve lesions in elderly differs no way from other diseases in posing problems. These problems may be in terms of high morbidity (Longer ventilation, high inotropes, associated procedures, renal failure, stroke, redo surgeries etc) or high mortality. In our subset rheumatic disease present from very young age to adulthood. The surgical aspect may differ in terms of age related degeneration leading to friable tissue, calcification of leaflets infiltrating in the annulus, other valvular pathology, organic pulmonary disease, Left ventricular dysfunction.

Older patients has more severe commissural fusion and leaflet thickening. Calcification more often found in elderly group, begins at commissures and then extends posteriorly. Sub valve damage is more in restenosis patients. Organic pulmonary vasculature changes may develop in long standing disease. In our study 4 patients had mitral valve prolapse with severe regurgitation and needed valve replacement. Chances that mitral valve prolapse requiring valve replacement or repair are low.

Twelve patients were there with prior Open mitral commissurotomy, valve area improvement was significant. Pre OMC valve area was 0.8 ± 0.1 cm2 which increased to 2.65 ± 0.26 cm2. It well correlates with the post procedural valve area. Best recovery occurred with post procedural valve area of > 2.2 cm2. Post OMC thromboembolic rate was 1% per patient year.

The rhythm had signficant difference in these two groups, both in sinus rhythm and atrial fibrillation. Total 54.28% patients were in sinus rhythm, out of which 45.66% were in group I (< 0.05). This might be because of younger age of this group. With increasing age atrial transport functions may be deteriorating.

Older age is often associated with increased operative risk and have negative influence on outcome. Because of this nonsurgical treatment is more readily chosen in patients older than 75 years.5 After correction of expected mortality within age group, relative survival in older patients was worse compared with that in younger ones. Even in our study group II patients had poor immediate post operative results, longer inotropic support, prolong ventilation and more neurological complication. Parsonnet et al predict operative mortality of 17% for patients more than 70 years undergoing redo mitral valve surgery.6 This study showed age more than 60 years as significant poor long term prognosis, although operative mortality was low.

ACC/AHA guidelines for management of patients with valvular heart disease clearly stated that patients more than 70 years were mostly in NYHA class III and IV at the time of surgery. Irrespective of age, preoperative NYHA class was most important risk factor both for mortality and morbidity.9,10

Mechanical valves work for very long period but have definite risk of anticoagulant related complications. On other hand bioprosthetic valve have risk of degenerative changes. Matsuhiko Matsuyama et al showed in recent article that bioprosthetic valves should be used for patients more than 60 years of age.11 Katsuhiko Matsuyama et al showed that higher age and NYHA are independent risk factors for lower survival rate. Author suggested bioprosthetic valve use in patients with age more than 60 years. Newer generation bioprosthetic valve are improved and various studies showing compatible results for 15-18 years of follow-up. So in our subset of patients, who present to us in the age bracket of 55 to 65 years, bioprosthetic valves may be a wise answer. Patients less than 60 years of age have high chances of redo surgery in life time. This group of patients may require mechanical valves. Reoperation for valvular heart disease in octogenarian patients carry a high postoperative mortality and morbidity.12

Our inhospital mortality was 5% which is lesser than other authors reported, the reason may be younger age group in our study, single valve lesions, no associated coronary artery disease and at last improved intensive care management.

Data clearly revealed more severe tricuspid valve involvement in group II suggesting prolong disease certainly deteriorating lung functions and ultimately right ventricle. Not only functional TR and TS was more, organic affection of tricuspid valve was also statistically significant. More than 50% of patients of group II had severe mitral valve calcification as compared to group I. Redo surgery, increasing age, other interventions increase the severity of subvalvular pathology. Although no statistical difference in subvalvular pathology found in both the groups.

Adding both in hospital and long-term mortality make group II a high risk proposition (17.5%). Data is stating that patients who are more than 60 years of age are definitive at higher risk of mortality and morbidity. There was no difference in pulmonary artery pressures in both groups. Intraoperative findings of both groups also resembled.

Those who are given mechanical valve have definitive high incidence of bleeding problems. It is controversial that elderly patients have high chances of coagulation related problems as compared to patients with mechanical valves.13-15 Atherosclerosis, prior neurological event, diabetes, female sex, atrial fibrillation, duration of cardiopulmonary bypass, low ejection fraction are the predictors of high mortality.16,17 Left ventricle dysfunction was seen in 12.50% patients of group II as compared to 2.50% in group I. Low ejection fraction in pure mitral stenosis may be because of chronic under filled left ventricle, severe posterior basal and anterior lateral segment hypokinesia.18,19

Conclusion

Increasing life expectancy in our subcontinent with more and more conservative procedures like balloon mitral valvotomy, closed and open commissurotomy leading to increase in elderly aged patients with mitral valve disease. Multivariate analysis showed age, redo surgery, atrial fibrillation, preoperative functional status as incremental risk factors. This study showed decrease in mortality and morbidity in this subset of patients. But results must be taken with pinch of salt as our patients in this study do not include multivalvular lesions, poor left ventricle, coronary artery disease etc.

References

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LOW CHOLESTEROL MAY NOT INCREASE RISK OF STROKE

High alcohol consumption may explain the association between low blood cholesterol and increased risk of haemorrhagic stroke. Haemorrhagic stroke was negatively associated with blood cholesterol, but this inverse association was confined to participants with hypertension.

BMJ, 2006; 333 : 22.

 
 
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