Relationship Between Patients' Knowledge On Anticoagulation After Mechanical Valve Replacement And Anticoagulation Quality

Objective:To evaluate the relationship between patients' knowledge on anticoagulation therapy after mechanical valve replacement and their anticoagulation quality measured by INR time in therapeutic range.Method:In this cross-sectional research,a questionnaire is designed to survey the patients undergone mechanical valve replacement in cardiac surgery department of Shanghai Zhongshan hospital from January 2006 to December 2007.Patients who are eligible for follow-up are those on long term anticoagulation therapy after mitral valve replacement,aortic valve replacement or double valve replacement.There is no specific limitation on patients' gender,age,medical history,method of surgery or the brand of mechanical valve.The questionnaire collects patients' basic information, knowledge of anticoagulation,habits on therapy,latest INR to a specific date and anticoagulation related complications.The follow-up data are then analyzed by gender, age,time of surgery,anticoagulation knowledge,overall knowledge score,interval between INR monitoring and complications using statistical software SPSS.Result:There are 1053 valid questionnaires included in the research.When the data are analyzed by gender,there is no significance(p＞0.05) on all survey entries between groups but trends can be observed that females have less knowledge about anticoagulation than males do.Two kinds of grouping are used in age analysis.There is no significance(p＞0.05) on all survey entries between groups in the first kind of grouping in which patients are divide by every 10 years of age.The other kind of grouping is by type of age like juveniles,the youth,the middle-aged and the old. There is difference in interval between INR monitoring among groups.The longest mean interval is in 10-18 year-old group and the shortest is in 55-70 year-old group (11.25±8.14 weeks vs.6.92±6.23 weeks,p=0.00365).There is no significance(p＞0.05) in other survey entries but trends can be observed that patients in 40-50 year-old group as well as the middle aged have less knowledge on anticoagulation and lower TTR.Time of surgery is also sorted by two kinds of grouping.Firstly,group 2006 and 2007 are compared and there is more complication occurred in 2006 than in 2007 (11.75%vs.4.96%,p＜0.0001);longer interval between INR monitoring in 2006 than in 2007(9.20±7.01 weeks vs.6.16±5.31 weeks,p＜0.0001).Secondly,patients are compared by grouping of quarter and there is most complications occurred in the first quarter of 2006 while least in the third quarter of 2007(13.89%vs.3.05%,p=0.0053); longest interval between INR monitoring in the second quarter of 2006 while shortest in the fourth quarter of 2007(10.10±7.22 weeks vs.3.74±3.22 weeks,p＜0.0001). When patients are categorized by 5 survey entries about anticoagulation knowledge, their TTR increases in the sequence of knowing "Check Blood","See INR","INR target range","Out-of-range risk" and "Method of control anticoagulation".Trends can be observed that the longest interval of INR monitoring is in patient group of knowing "Check blood" while the shortest in group of knowing "Method of control anticoagulation"(7.44±6.18 weeks vs.5.15±3.35 weeks);most complications in group of knowing "Out-of-range risk"(10.35%,p=0.0035) while least in group of knowing "Check blood"(7.91%,p＞0.05).The overall knowledge score indicates patients knowledge level of anticoagulation.There are 0.38%,27.92%,8.36%, 13.30%,18.33%and 31.72%patients in group of 0 point,1 point,2 points,3 points,4 points and 5 points respectively.There is difference in TTR among groups(p＜0.0001). If analysis excludes 0-point patients,facts can be observed that the highest TTR is in 5-point patients INR 1.8～2.5:68.26%;INR 1.8～2.8:76.95%;INR 2.0～3.0:64.97%; INR 1.8～3.0:79.34%and TTR increases in the sequence of overall scores.There is significance in the linear correlation of overall knowledge score and TTR:INR 1.8～2.5:r=0.9053,p＜0.05;INR 1.8～2.8:r=0.9330,p＜0.05;INR 2.0～3.0:r=0.9443, p＜0.05;INR 1.8～3.0:r=0.9548,p＜0.05.There is also difference in interval of INR monitoring among score groups.The longest mean interval is in 0-point group and the shortest is in 5-point group(26.00±12.00 weeks vs.4.91±2.95 weeks,p＜0.0001). When patients are analyzed by interval of INR monitoring,there is difference in overall knowledge score among groups.The highest score is in 1-4 week-interval group and lowest is in＞12 week-interval group(3.72±1.47 points vs.1.76±1.29 points,p＜0.0001).There is also difference in TTR among groups.TTR under all three 1NR target range,except target INR 1.8～2.5,decreases in the sequence of 1-4 weeks, 4-8 weeks,8-12 weeks and＞12 weeks interval.The linear correlation between interval of INR monitoring and TTR are INR 1.8～2.5:r=-0.9129,p＞0.05;INR 1.8～2.8:r=-0.9641,p＜0.05;INR 2.0～3.0:r=-0.9880,p＜0.05;INR 1.8～3.0:r=-0.9708, p＜0.05.When patients are analyzed by whether they suffered from anticoagulation related complications.There is difference in overall knowledge score between groups (p=0.0023).More patients in non-complication group than that in complication group (28.90%vs.16.67%) score 1 point in low score level(0 point to 2 points) and more patients in complication group than that in non-complication group(39.29%vs. 31.06%) score 5 points in high score level(3 points to 5 points).There is no significance in 5 anticoagulation knowledge survey entries between groups(p＞0.05) but trends can be observed that except the entry of "Check blood",all the other 4 entries show higher knowing ratio in complication group than that in non-complication group("See INR" 67.86%vs.66.36%;"INR target range" 65.48% vs.62.23%;"Method of anticoagulation control" 40.48%vs.36.12%;"Out-of-range risk" 66.67%vs.50.05%).Conclusion:This cross-sectional research on the patients' knowledge of anticoagulation therapy after mechanical valve replacement and their anticoagulation quality indicates:1.Patients' knowledge on anticoagulation therapy is not as much as expected.2.Patients' knowledge level on anticoagulation positively correlated with INR time in therapeutic range.3.The higher patients' knowledge level on anticoagulation the shorter their interval of INR monitoring is.All these prove that anticoagulation quality can be improved through better patient education on anticoagulation therapy.