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 Table of Contents  
Year : 2021  |  Volume : 7  |  Issue : 2  |  Page : 158-167

Use and assessment of knowledge of Vitamin K antagonist therapy in cardiac patients: A Tertiary Care Hospital-based survey

1 Associate Public Health Consultant, Quintiles IMS-Health, Gurgaon, Haryana, India
2 Department of Cardiology, VMMC and Safdarjung Hospital, New Delhi, India
3 Cardiac Electrophysiology(adult), Toronto General Hospital, University Health Network, Toronto(Ontario), Canada
4 Indian Institute of Public Health-Delhi, Public Health Foundation of India, Gurgaon, India

Date of Submission24-Mar-2021
Date of Decision09-Jul-2021
Date of Acceptance12-Jul-2021
Date of Web Publication31-Aug-2021

Correspondence Address:
Anwar Hussain Ansari
Room 737, Superspeciality Block, Department of Cardiology, VMMC and Safdarjung Hospital, New Delhi - 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jpcs.jpcs_16_21

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Background: Safety and efficacy of Vitamin K antagonists (VKAs), the most widely used oral anticoagulant (OAC), is monitored by therapeutic international normalized ratio (INR). The current study was conducted to evaluate the proportion of patients achieving therapeutic range INR and assessment of the knowledge, and awareness among patients regarding OAC therapy, as well as identification of the challenges in the monitoring of INR. Materials and Methods: This hospital-based, single-center cross-sectional study was conducted at a tertiary care hospital in Delhi. Patients on anticoagulation with VKAs were interviewed and their records were reviewed. Information on sociodemographic characteristics, history of cardiac illness, INR range, knowledge, and awareness regarding VKA therapy were analyzed. Data management was done via CSPro and statistical analysis via STATA 13.0. Results: A total of 86 patients were evaluated. The mean age of the study participants was 49 ± 14.9 years. Only 29.1% of the study group achieved therapeutic INR. Overall awareness and knowledge regarding the need for VKA therapy, ideal INR range, complications of poor monitoring, and dietary restrictions were in the range of 31%–48%. Conclusion: Poor INR control is prevalent in Indian patients on VKAs therapy. Although the future practice may move toward newer anticoagulants, a substantial proportion of our population may still need VKAs. Hence, there is a need for improving the knowledge and awareness of patients on VKA therapy to improve therapeutic effectiveness.

Keywords: Atrial fibrillation, mechanical prosthetic heart valve, newer oral anticoagulants, oral anticoagulant, therapeutic international normalized ratio

How to cite this article:
Pattnaik N, Ansari AH, Chakraborty P, Devasenapathy N. Use and assessment of knowledge of Vitamin K antagonist therapy in cardiac patients: A Tertiary Care Hospital-based survey. J Pract Cardiovasc Sci 2021;7:158-67

How to cite this URL:
Pattnaik N, Ansari AH, Chakraborty P, Devasenapathy N. Use and assessment of knowledge of Vitamin K antagonist therapy in cardiac patients: A Tertiary Care Hospital-based survey. J Pract Cardiovasc Sci [serial online] 2021 [cited 2022 Jun 28];7:158-67. Available from: https://www.j-pcs.org/text.asp?2021/7/2/158/325218

  Introduction Top

Despite the availability of several novel oral anticoagulants (NOACs), Vitamin K antagonists (VKAs) are still the most widely used oral anticoagulants (OACs) in India due to easy availability, low cost, the familiarity of physicians, and significant prevalence of compelling indications. However, several practical challenges exist with VKAs therapy due to narrow therapeutic index and inter- and intra-patient variability in dose responsiveness leading to the requirement of frequent monitoring by assessment of international normalized ratio (INR).[1],[2] Patients with improper anticoagulation control are at increased risk of thromboembolism and catastrophic complications, i.e. intracranial bleeds. NOACs have a rapid onset and offset of action, few food and drug interactions, lower risk of bleeding complications, and do not need monitoring.[1],[3] However, shortcomings of NOACs include high cost, susceptibility to gastrointestinal bleeds, uncertain dosing in presence of renal failure, absence of readily available antidote, and lack of assays to test their anticoagulant action.[1],[2],[3] All these factors coupled with their unproven efficacy in patients with mechanical prosthetic valve and valvular atrial fibrillation (AF), two common conditions prevalent in the Indian population, contribute to the use of VKAs in a large number of Indian patients.

Various studies, conducted in both real-world and controlled settings, have reported wide variability in the percentage of patients in the therapeutic INR range. Studies from the western population have reported more than 50% of the study population in ideal therapeutic INR in the clinical setting with a marginal increase (60%) in controlled settings.[4],[5],[6],[7],[8],[9],[10],[11],[12] On the contrary, few small observational studies from India have reported only 17%–19% of patients to be in therapeutic range for the given indication.[13],[14] A recent study at a tertiary care hospital (2015) found that only 30% of patients achieved therapeutic INR.[15] A large multicenter registry on rheumatic heart disease, the REMEDY study, involving 12 African countries, Yemen, and India has reported that only 41.5% of monitored patients on OACs had therapeutic INR at the time of enrolment.[16]

Knowledge and awareness of VKA anticoagulant therapy among patients have a significant impact on the quality of long-term OAC therapy.[17] The background literacy status of patients, health awareness, and the doctor-to-patient ratio could be some of the factors that could attribute to this awareness among patients. A single-center prospective randomized controlled study in Kerala demonstrated that the involvement of clinical pharmacists in anticoagulation management is associated with improvement in anticoagulation control (73.4% in the intervention group achieved therapeutic INR compared to 53.2% in the control group).[18] While literature exists regarding knowledge and awareness of OAC therapy among patients from the West[19],[20] and Asian population,[17],[21],[22],[23],[24] there is a paucity of data from the Indian population.[15]

Hence, we conducted a hospital-based survey among patients on VKA attending cardiology outpatient department (OPD) to capture information with the following objectives: (1) to obtain the proportion of patients in the therapeutic range at the time of interview and (2) to assess the knowledge and awareness among patients about OAC therapy and the challenges they faced in INR monitoring.

  Materials and Methods Top

This cross-sectional survey was conducted at the cardiology OPD of VMMC and Safdarjung Hospital, a tertiary care academic hospital in Delhi, between February and May 2016. Patients who were receiving VKAs for more than 2 months for various indications were invited for an interview. Patients with age <18 years, pregnancy, history of OAC usage for <2 months, end-organ failure, chronic obstructive airway disease, and end-stage malignancy were excluded. The study was approved by the institutional ethics committees of the collaborating institutes and was conducted as per the national ethical guidelines (Indian Council of Medical Research).

The sample size was calculated for the primary outcome, the percentage of patients in the therapeutic range. Based on the REMEDY RHD registry,[16] we assumed a prevalence of 40%. To obtain a prevalence estimate and a 95% confidence interval (CI) with 10% absolute precision, we required approximately 78 patients with finite population correction.

After obtaining written informed consent from the patients, a structured pretested questionnaire [Appendix 1] was used to collect information on sociodemography, history of cardiac and other medical illnesses, dose and type of currently prescribed OACs, knowledge and awareness about anti-coagulation, and difficulty in repeated laboratory testing for INR. Information about the latest/current and past INR values was collected from the laboratory reports along with prothrombin time (PT) values.

Descriptive statistics were used to present data on demographic and clinical characteristics, adherence and knowledge, and awareness of OAC therapy. Continuous variables were expressed as mean and standard deviation (SD), whereas categorical variables were expressed as frequencies and percentages. INR was categorized as normal therapeutic, supratherapeutic, and subtherapeutic range as per the following criteria: for mechanical prosthetic valve indications, 2.5–3.5 = therapeutic INR, <2.5 = subtherapeutic, and >3.5 = supratherapeutic. For nonmechanical valve indications, 2–3 = therapeutic INR, <2.0 = subtherapeutic, and >3.0 = supratherapeutic. We report a 95% CI for the primary outcome. Association between INR therapeutic range and awareness and association between valvular and nonvalvular indications were explored using Chi-square tests.

  Results Top

The sociodemographic and clinical profile of the study sample (n = 86) is presented in [Table 1].
Table 1: Characteristics of the study population (n=86)

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The mean age was 49 (SD 14.9) years and 57% were female. Of the 86 patients, 65% (n = 56) had AF, 30% (n = 25) had deep-vein thrombosis (DVT), and 26% (n = 22) had prosthetic heart valves. About 12.5% of the study population had a combination of AF and DVT, 13% had DVT and prosthetic heart valve, and 47.8% had combined AF and prosthetic heart valve. RHD was the reason for 70% of valve replacements and 72% of AF. All the prosthetic heart valves were mechanical. At the time of the interview, 17% of the study population were in NYHA Class III and around 40% had other noncardiac co-morbid conditions.

Details of OAC therapy and INR ranges are summarized in [Table 2].
Table 2: Oral anticoagulation use and international normalized ratio monitoring

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A small percentage of patients were prescribed concomitant aspirin (18.6%) and acenocoumarol was the most commonly (91%) prescribed OAC agent. The median duration of OAC usage was 21 (interquartile range [IQR] 5–68) months and the median time in days since the last INR test was performed was 14.5 (IQR 1–23). Seven patients had the last INR report beyond 100 days. Two consecutive INR reports were available for 47 patients at the time of the interview and the median duration in days between the two INR readings was 36 days (IQR 19–84). The mean of tested PT was 23.8 s (SD 11.4) and control PT was 12.8 (SD 1.3).

Overall, based on the last INR report, 29.1% of patients achieved therapeutic INR range (95% CI, 20–40) at the time of interview, while INR ranges were subtherapeutic and supratherapeutic in 59.3% (95% CI, 48–70) and 11.6% (95% CI, 6–20) patients, respectively. A higher percentage of patients with prosthetic heart valve were on therapeutic INR (36.4% in prosthetic valve vs. 26.6% in the native valve), but it was statistically nonsignificant [P = 0.403, [Table 2]]. Three-fourth of patients reported having taken their medications and not missed any dose of OAC in the last 1 week and 27.4% of patients had missed at least one dose in a week before the interview.

As shown in [Table 3], we present knowledge and awareness of patients with OAC therapy for all patients stratified by indication and INR range. Overall prevalence of awareness and knowledge regarding the necessity of taking OACs, the need for INR monitoring, the ideal INR range, and consequences of poor monitoring were <50%. However, the majority reported having informed other physicians (69.8%) and chemists (70.9%) about the use of OAC. Most (80%) of the study population had a weekly supply of OAC, that was supplied by the hospital free of cost. The study did not find an association between knowledge and awareness about anticoagulant use, being in the therapeutic range. However, those in the prosthetic valve group were more aware than the native valve group [Table 3].
Table 3: Knowledge and awareness regarding warfarin adherence and international normalized ratio monitoring

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Around half of the patients did not report any difficulty in following the OAC regimen. The reported challenges regarding INR testing for other patients include frequent travel to the hospital (24.4%), other comorbid conditions that make it difficult to follow the treatment plan (14%), and financial issues (29%) [Figure 1].
Figure 1: Patient-reported challenges in international normalized ratio testing.

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The most reported bleeding episodes were skin bruising (n = 26; 30%) followed by heavy menstrual bleeding (29%) among women (n = 49). Six patients (7%) reported a major bleeding event, namely bleeding into joints (n = 5) and hematuria (n = 1) and those events were confirmed from patient OPD records. Of the total bleeding events (n = 44), 55% were in the subtherapeutic range group, 27% in the normal range, and 18% in the supratherapeutic range group.

  Discussion Top

This hospital-based cross-sectional study of patients on OAC for cardiac indications demonstrated that 29.1% of patients achieved therapeutic range INR at the time of the interview. Knowledge about complications of poor monitoring, food restrictions, need for INR monitoring, and ideal INR range was low. Only one-third (32.6%–37.2%) of all patients were aware of these parameters. Patients with prosthetic valves were more aware than those with native valves. We did not find an association between awareness and knowledge about anticoagulation use, complications of poor monitoring, and drug–food interactions with anticoagulation control (therapeutic range INR). Better awareness in the prosthetic valve group did not translate into better INR control than the native valve group (P = 0.403).

Previous studies in India suggest poor INR control in patients on chronic VKAs anticoagulation. A recent study at a tertiary care hospital in the national capital (2015) found only 30% of patients in the therapeutic range INR.[15] Compared to the REMEDY study, the percentage of patients in the therapeutic INR range was lower (29% vs. 41.5%), but similar findings have been reported by other Indian studies where 73%–76.3% of the INRs were in the subtherapeutic range, 17%–19.1% in the therapeutic range, while 4.6% INRs were beyond the therapeutic range.[13],[14],[16] Studies conducted in the West have reported more than 50% INRs to be in the therapeutic range in both real and controlled trial settings.[4],[5],[6],[7],[8],[9],[10],[11],[12]

Subtherapeutic INR is a persistent problem in Asian patients in general and India in particular. In the RE-LY AF registry, the proportion of therapeutic INR values was highest in West Europe (67%), lower in Asia (37%), and lowest in India (35%).[25] This may be related to poor awareness of both physicians and patients about anticoagulation control, poor patient education, and inadequate testing facilities.[13],[14] A tendency to chronic underdosing by physicians has been observed.[13] Many systematic reviews of interventional studies conducted in the West have reported that self-monitoring and self-management in long-term OAC users have yielded a better anticoagulation control and reduced the morbidity and mortality due to thromboembolic diseases, but patients need to be self-motivated to follow the benefits of these tools.[26] But how far this will succeed in a country such as India with a majority of patients with the low socioeconomic condition and a low level of health awareness remains to be seen. Services of nonphysician health workers (nurses, pharmacists, and paramedics) at hospitals and community health centers can be useful to help educate patients and help them in home monitoring and dose adjustments as per the INR report. In those who are unable to achieve target INR despite these interventions, the scope of NOACs needs be evaluated especially in the setting of valvular AF with RHD, since there is scarcity of data for their use in this clinical setting. The ongoing INVICTUS rheumatic heart disease research program, an international, multicenter, randomized trial aimed to study the noninferiority of a NOAC (rivaroxaban 20 mg) compared to VKA in patients with rheumatic AF with high thromboembolic risk would provide new information on the use of NOAC in patients with rheumatic AF and poor quality of anticoagulation with VKA.[27] However, a major limitation of NOAC's use remains its cost. It is a major challenge on the part of main stakeholders to make it cost-effective for those in whom it is needed the most and to optimize its benefits. Hence, a cost-effectiveness analysis in the Indian context alongside clinical effectiveness is likely to change clinical practice.

Out-of-range INR has important clinical consequences with both increased thrombotic risk and bleeds. Common reasons for subtherapeutic INR may be nonadherence to VKAs, dose reductions, interruptions for surgery, continued low INR due to underdosing, or drug–food interactions.[28] Patients from India are at least a decade younger with a higher percentage of females when compared to the patients on prophylactic anticoagulation from the West.[4],[5],[6],[7],[8],[9],[10],[11],[12] This has important social and economic implications because most patients in this age group are physically active and have dependent family members to look after and many women are still in the reproductive age group. Any morbidity associated with inadequate or over-anticoagulation will have implications not only for the individual but for the family as well.

Our findings on awareness of the use of this medication are concordant with other Asian studies[17],[21],[22],[23] and western data.[19],[20],[29] The knowledge regarding OAC therapy in western studies[19],[29] was 37%–74% and in Asian studies[17],[21] between 41% and 54% and the an Indian study[15] showed poor knowledge score in 50% of patients. Even in the study by Baker et al. where 74% of patients had good knowledge of anticoagulation therapy, no significant association was found between patient warfarin knowledge and INR control.[29] Conversely, Davis et al. showed a significant association between adherence to therapy and good anticoagulant control, but in this study too, no association was found between patient's knowledge and anticoagulation control.[19] On the contrary, a study by Mayet did not show any association between adherence and anticoagulation control.[23] Our patients primarily relied on specialist physician information on VKAs and the time allowed in busy OPD settings might have been insufficient for this purpose. It has been shown that a dedicated anticoagulation clinic care versus general OPD care may provide better outcomes as assessed by INR time in range.[29],[30] Providing education to new patients, attendants, and families in anticoagulation clinics and subsequent reinforcements in follow-up visits improves patient knowledge about VKAs.[29] Improved awareness in prosthetic valve group versus nonprosthetic valve group in our study might have been because these patients had undergone a major lifesaving surgery and therefore were more receptive to doctors' advice and prescription. These patients had been hospitalized for a variable period and during hospitalization and doctors would have warned them more about the consequences of inadequate anticoagulation and patients would have heeded to doctors' advice.

Optimal information and awareness are key parameters to control and prevent any illness. The significance of this factor increases with a chronic condition; hence, knowledge and awareness regarding VKA therapy and adherence to treatment could be an important indicator for management of this chronic condition even if we did not show a statistically significant association. While the future treatment practice may move toward NOACs, we still would have a substantial proportion of VKA's. Hence, future research should focus on understanding the health literacy and numeracy of patients and caregivers to contextualize and designing context-specific interventions that can improve patient satisfaction and clinical outcomes.

Limitations of the study

This study has several limitations. The findings of this study are based on a single INR report, present at the time of the interview. Due to the small sample size, we did not find any significant association of anticoagulant control with knowledge and awareness, and we did not collect this information from a physician's perspective. Furthermore, we did not collect detailed drug history, except for aspirin, and various drug interactions with VKAs could have affected the anticoagulation quality. Our study does not find reasons for a sub- or supratherapeutic range as suboptimal INR range could be attributed to many other factors such as drug interactions or genetic variations. However, for the primary outcome, our study results are generalizable to some extent as the study center is a large tertiary care hospital catering to a large section of the population in the northern region of the country.

  Conclusion Top

There is a dire need to improve VKA anticoagulation therapy management in our country. A large number of our patients will still need VKA due to the high prevalence of rheumatic mitral valve disease and mechanical heart valves. There is a need for improving not only the knowledge and awareness of patients on VKA therapy but also to know the physician perspective to correct any subtherapeutic dosing to improve therapeutic effectiveness since majority of patients (60%) had subtherapeutic INR. Home monitoring of INR and dose adjustments of VKAs, easy availability of free-of-cost standardized INR testing facilities, and dedicated anticoagulation clinics are important measures which have been instrumental in achieving desired results.

Ethical clearance

The study was part of thesis for the student of Indian Institute of Public Health and carried out at VMMC and Safdarjung Hospital. So, Ethical clearance of both institutes were taken


We thank the coordinating centers of this study, i.e. the Indian Institute of Public Health and VMMC and Safdarjung Hospital. We want to thank Mr. Manoj Soni for his help in the creation of the database and his assistance in data management of the study. Last, but not the least, we also would like to extend our vote of thanks to all the participating patients in this study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Table 1], [Table 2], [Table 3]


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