Ischemic stroke in the setting of supratherapeutic International Normalized Ratio following coronavirus disease 2019 infection: a case report.

BACKGROUND: SARS-CoV-19 infection is associated with an increased risk of thrombotic events. We present a case of acute middle cerebral artery ischemic stroke in a patient with SARS-CoV-19 infection despite being on warfarin with supratherapeutic INR (International Normalized Ratio). CASE PRESENTATION: A 68-year-old Caucasian female with multiple comorbidities was admitted to the hospital with symptoms of upper respiratory tract infection. A rapid antigen test confirmed the diagnosis of COVID-19 pneumonia, and intravenous remdesivir was initiated. On the fifth day of admission, the patient experienced sudden onset confusion, slurred speech, left-sided hemiplegia, right-sided eye deviation, and left-sided facial droop. Imaging studies revealed an occlusion of the distal anterior M2 segment of the right middle cerebral artery, and an MRI of the brain confirmed an acute right MCA infarction. Notably, the patient was receiving warfarin therapy with a supratherapeutic INR of 3.2. CONCLUSIONS: This case report highlights the potential for thromboembolic events, including stroke, in patients with COVID-19 infection, even when receiving therapeutic anticoagulation therapy. Healthcare providers should be vigilant for signs of thrombosis in COVID-19 patients, particularly those with pre-existing risk factors. Further research is necessary to understand the pathophysiology and optimal management of thrombotic complications in COVID-19 patients.

Management, control, and decision making in unexpected recurrent venous thromboembolism in COVID-19: a case report.

BACKGROUND: Coronavirus disease 2019 was spread worldwide, as a pandemic, from December 2019. Venous thromboembolism events can inflict patients with coronavirus disease 2019 during the hospitalization or convalescent period. Therefore, monitoring of these patients, in terms of venous thromboembolism events signs and symptoms, and timely management of antithrombotic agents are of great importance. CASE REPORT: A 45-year-old Iranian man, who is the first author of this case report, was infected by severe acute respiratory syndrome coronavirus 2 and displayed the typical signs and symptoms of coronavirus disease 2019. Although reverse transcription polymerase chain reaction for coronavirus disease 2019, and specific immunoglobulin M and immunoglobulin G against severe acute respiratory syndrome coronavirus 2, were negative at first, chest computed tomography scan showed the characteristic pattern of lung involvement of a coronavirus disease 2019 infection including bilateral and multilobar ground-glass opacities. At that time, there were no signs or symptoms of deep-vein thrombosis or pulmonary thromboembolism, so these were not investigated. About 30 hours after hospital discharge, the patient presented back to the hospital with acute-onset chest pain. We instantly tested his blood for D-dimer, and sent him to take a Doppler sonography of his lower legs and a chest computed tomography angiography in search of pulmonary thromboembolism and deep-vein thrombosis. Although we could confirm pulmonary thromboembolism with computed tomography angiography in our patient, there were no signs or symptoms of venous thromboembolism in his lower legs, and color Doppler sonography of lower limbs was normal. So, the patient was treated with rivaroxaban as an antithrombotic agent. After some days, he was discharged in good condition. About 1 month later, he was referred to our hospital because of left lower limb edema. Although he was under antithrombotic therapy, color Doppler sonography of lower limbs revealed acute deep-vein thrombosis of the left leg. Hence, we decided to shift antithrombotic therapy from rivaroxaban to warfarin, as it is more potent than rivaroxaban in recurrent venous thromboembolism and when taking new oral anticoagulants. Unlike rivaroxaban, which needs no blood test to monitor its efficacy but has a warning for signs and symptoms of bleeding, warfarin therapy must be monitored carefully by regular blood tests for prothrombin time and international normalized ratio to maintain them in the therapeutic range. The patient was informed about the bleeding cautions, and required regular check of prothrombin time and international normalized ratio to maintain them in the proper and advised range of treatment (international normalized ratio therapeutic range 2-3). CONCLUSION: In the case of unexpected recurrent venous thromboembolism in coronavirus disease 2019, especially when patients are taking rivaroxaban or other new oral anticoagulants, such drugs should be substituted by warfarin, with routine follow-up, to maintain the value of prothrombin time and international normalized ratio within the therapeutic range.

The Clinical Outcomes of COVID-19 in Patients on Warfarin: A Propensity Score Matching Study.

BACKGROUND: COVID-19 is associated with vascular thrombosis in critical patients. However, warfarin has not been adequately studied in patients with COVID-19. This study aimed to evaluate whether the use of warfarin, a potent oral anticoagulant, was of clinical benefit in patients with COVID-19. METHODS: This was a retrospective cohort study of COVID-19 patients diagnosed at 3 different centers in Turkey between April 2020 and April 2021. Patients were grouped by whether they were taking warfarin or not. Propensity score matching analysis was used to compare the dif ferences between the groups in mortality, hospitalization, and admission to the intensive care unit. RESULTS: A propensity score analysis was performed on 128 patients in the warfarin group and 372 patients in the control group. After matching, 84 pairs of patients were compared. The patients in the control group were more likely to be admitted to the intensive care unit (33.3% vs. 14.3%, respectively; P=.007) and had longer hospital stays than the warfarin group (7.1 vs. 14.1 days; P=.005). The warfarin group had a lower death rate compared to the control group (7.1% vs. 27.4%, respectively; P=.001), and surviving patients were sig nificantly more likely to be in the warfarin group than the control group (56.1% vs. 20.7%, respectively; P=.001). In patients on warfarin, there was a lower incidence of in-hospital death (log-rank test P=.005). CONCLUSIONS: Warfarin therapy could provide clinical benefits in patients with COVID-19. The current data highlight the importance of potent anticoagulation in the treatment of COVID-19.

Management of Adults with Newly Diagnosed Atrial Fibrillation with and without CKD.

BACKGROUND: Atrial fibrillation (AF) is highly prevalent in CKD and is associated with worse cardiovascular and kidney outcomes. Limited data exist on use of AF pharmacotherapies and AF-related procedures by CKD status. We examined a large "real-world" contemporary population with incident AF to study the association of CKD with management of AF. METHODS: We identified patients with newly diagnosed AF between 2010 and 2017 from two large, integrated health care delivery systems. eGFR (≥60, 45-59, 30-44, 15-29, <15 ml/min per 1.73 m2) was calculated from a minimum of two ambulatory serum creatinine measures separated by ≥90 days. AF medications and procedures were identified from electronic health records. We performed multivariable Fine-Gray subdistribution hazards regression to test the association of CKD severity with receipt of targeted AF therapies. RESULTS: Among 115,564 patients with incident AF, 34% had baseline CKD. In multivariable models, compared with those with eGFR >60 ml/min per 1.73 m2, patients with eGFR 30-44 (adjusted hazard ratio [aHR] 0.91; 95% CI, 0.99 to 0.93), 15-29 (aHR, 0.78; 95% CI, 0.75 to 0.82), and <15 ml/min per 1.73 m2 (aHR, 0.64; 95% CI, 0.58-0.70) had lower use of any AF therapy. Patients with eGFR 15-29 ml/min per 1.73 m2 had lower adjusted use of rate control agents (aHR, 0.61; 95% CI, 0.56 to 0.67), warfarin (aHR, 0.89; 95% CI, 0.84 to 0.94), and DOACs (aHR, 0.23; 95% CI, 0.19 to 0.27) compared with patients with eGFR >60 ml/min per 1.73 m2. These associations were even stronger for eGFR <15 ml/min per 1.73 m2. There was also a graded association between CKD severity and receipt of AF-related procedures (vs eGFR >60 ml/min per 1.73 m2): eGFR 30-44 ml/min per 1.73 (aHR, 0.78; 95% CI, 0.70 to 0.87), eGFR 15-29 ml/min per 1.73 m2 (aHR, 0.73; 95% CI, 0.61 to 0.88), and eGFR <15 ml/min per 1.73 m2 (aHR, 0.48; 95% CI, 0.31 to 0.74). CONCLUSIONS: In adults with newly diagnosed AF, CKD severity was associated with lower receipt of rate control agents, anticoagulation, and AF procedures. Additional data on efficacy and safety of AF therapies in CKD populations are needed to inform management strategies.

Time in therapeutic range for virtual anticoagulation clinic versus in-person clinic during the COVID-19 pandemic: a crossover study.

BACKGROUND: COVID-19 infection affects the quality of the medical services globally. The pandemic required changes to medical services in several institutions. We established a virtual clinic for anticoagulation management during the pandemic using the Whatsapp application. OBJECTIVES: Compare anticoagulation management quality in virtual versus in-person clinics. DESIGN: A retrospective crossover study SETTINGS: Specialized cardiac care center PATIENTS AND METHODS: The study included patients who presented to Prince Sultan Cardiac Center in Riyadh for anticoagulation management during the pandemic from March 2020 to January 2021. We compared time in therapeutic range (TTR) in the same patients during virtual and in-person clinics. All international normalized ratio (INR) measures during the virtual clinic visits and prior ten INR measures from the in-person clinic were recorded. Patients who had no prior follow-up in the in-person clinic were excluded. MAIN OUTCOME MEASURE: TTR calculated using the Rosendaal method. SAMPLE SIZE: 192 patients RESULTS: The mean age was 58.6 (16.6) years and 116 (60.4%) were males. Patients were diagnosed with atrial fibrillation (n=101, 52.6%), mechanical mitral valve (n=88, 45.8%), mechanical aortic valve (n=79, 41%), left ventricular thrombus (n=5, 2.6%) and venous thromboembolism (n=8, 4.2%). Riyadh residents represented 56.7% of the study population (n=93). The median (IQR) percent TTR was 54.6 (27.3) in the in-person clinic versus 50.0 (33.3) (P=.07). CONCLUSION: Virtual clinic results were comparable to in-person clinics for anticoagulation management during the COVID-19 pandemic. LIMITATIONS: Number of INR measures during the virtual clinic visits, retrospective nature and single-center experience. CONFLICT OF INTEREST: None.

Online KidClot education for patients and families initiating warfarin therapy: The eKITE study.

Anticoagulation with Vitamin K antagonists (VKA) has always posed challenges in terms of monitoring requirements. These challenges were further exacerbated in the setting of the COVID-19 pandemic, with limited access to and/or avoidance of laboratory testing. The importance of utilizing point of care (POC) health technology for individualized patient management is salient. The foundation of effective home INR monitoring is establishing patient knowledge about their therapy and INR testing proficiency. The eKITE series was developed to support patients in establishing foundational knowledge required for VKA (warfarin) management and INR monitoring. The primary objectives were to evaluate eKITE, a patient-oriented innovative online education program for warfarin therapy, participant learning stress, and patient preference for online learning. This multi-center prospective study provided patients access to warfarin online education. Participants were required to complete written quizzes assessing warfarin knowledge of key concepts proficiency and identifying knowledge deficits. Patient preference, evaluating calm (lack of anxiety) while learning, and an INR on a home meter was completed. Participants performed INR tests at home and reported INRs by telephone. The analysis included 144 children and caregivers enrolled at five US and CDN sites. Most indications for anticoagulation were cardiac (congenital or acquired heart disease) with varied INR target ranges. Mean knowledge scores for warfarin and INR self-testing modules were 97%, with low anxiety with TTR of 84%. Patient preferred online learning. eKITE is an effective teaching modality for warfarin/home INR monitoring with safe INR testing and warfarin management that is appropriate for pediatrics and adults alike. PROLOGUE: The whir in the hallways is deafening. Lights bright, alarms are ringing in a chorus of unsynchronized beeps and screeches. It has been more than a week since I have slept. Snuggled beside me is my precious child, whining and equally irritated with the asynchronous symphony, further compounded by anxiety, procedures, and pain. The sun has broken. The staff smiles are welcoming and incessant, as one after one, they approach hurried, urgent, assiduous, their need to coach me for our upcoming departure to the warmth of home. Each provides essential information that I will require to keep my child, my treasure, safe and healthy. Yet, my eyes are heavy, blurred, and my brain foggy, trapped in a dark heavy cloud. How am I to follow? Comprehend? and retain anything? As they instruct, my precious child yearns for loving arms, compassion and love, whining, crying in disquiet. Overwhelmed does not adequately describe my ineffable exhaustion. Amidst this, how am I to learn about warfarin? Such a challenging medication, with so much to know. Concentrate, I tell myself, focus; now is my only opportunity to learn. I must be alert. It seems to be nonsensical.

Effect of common maintenance drugs on the risk and severity of COVID-19 in elderly patients.

BACKGROUND: Maintenance drugs are used to treat chronic conditions. Several classes of maintenance drugs have attracted attention because of their potential to affect susceptibility to and severity of COVID-19. METHODS: Using claims data on 20% random sample of Part D Medicare enrollees from April to December 2020, we identified patients diagnosed with COVID-19. Using a nested case-control design, non-COVID-19 controls were identified by 1:5 matching on age, race, sex, dual-eligibility status, and geographical region. We identified usage of angiotensin-converting enzyme inhibitors (ACEI), angiotensin-receptor blockers (ARB), statins, warfarin, direct factor Xa inhibitors, P2Y12 inhibitors, famotidine and hydroxychloroquine based on Medicare prescription claims data. Using extended Cox regression models with time-varying propensity score adjustment we examined the independent effect of each study drug on contracting COVID-19. For severity of COVID-19, we performed extended Cox regressions on all COVID-19 patients, using COVID-19-related hospitalization and all-cause mortality as outcomes. Covariates included gender, age, race, geographic region, low-income indicator, and co-morbidities. To compensate for indication bias related to the use of hydroxychloroquine for the prophylaxis or treatment of COVID-19, we censored patients who only started on hydroxychloroquine in 2020. RESULTS: Up to December 2020, our sample contained 374,229 Medicare patients over 65 who were diagnosed with COVID-19. Among the COVID-19 patients, 278,912 (74.6%) were on at least one study drug. The three most common study drugs among COVID-19 patients were statins 187,374 (50.1%), ACEI 97,843 (26.2%) and ARB 83,290 (22.3%). For all three outcomes (diagnosis, hospitalization and death), current users of ACEI, ARB, statins, warfarin, direct factor Xa inhibitors and P2Y12 inhibitors were associated with reduced risks, compared to never users. Famotidine did not show consistent significant effects. Hydroxychloroquine did not show significant effects after censoring of recent starters. CONCLUSION: Maintenance use of ACEI, ARB, warfarin, statins, direct factor Xa inhibitors and P2Y12 inhibitors was associated with reduction in risk of acquiring COVID-19 and dying from it.

Patients' and clinicians' perceptions of oral anticoagulants in atrial fibrillation: a systematic narrative review and meta-analysis.

BACKGROUND: Atrial fibrillation (AF) increases the risk of developing a stroke by 20%. AF related strokes are associated with greater morbidity. Historically, warfarin was the anticoagulant of choice for stroke prevention in patients with AF but lately patients are being switched or started on direct oral anticoagulants (DOACs). DOACs are promoted as safer alternatives to warfarin and it is expected that they will be associated with fewer challenges both for patients and healthcare professionals. This systematic narrative review aimed to explore perspectives of patients and professionals on medicines optimisation of oral anticoagulation with vitamin K antagonists and DOACs in atrial fibrillation. METHODS: Prospero registration CRD42018091591. Systematic searches undertaken of research studies (qualitative and quantitative), published February 2018 to November 2020 from several databases (Web of Science, Scopus, Medline Via Ovid, CINHAL via Ebsco, and PubMED via NCBI) following PRISMA methodology. Data were organised using Covidence software. Two reviewers independently assessed the quality of the included studies and synthesized the findings (thematic analysis approach). RESULTS: Thirty-four studies were included. Studies were critically appraised using established critical appraisal tools (Qualsyst) and a risk of bias was assigned. Clinicians considered old age and the associated complexities such as co-morbidities and the increased potential for bleeding as potential barriers to optimising anticoagulation. Whereas patients' health and medication beliefs influenced adherence. Notably, structured patient support was important in enhancing safety and effective anticoagulation. For both patients and clinicians, confidence and experience of safe anticoagulation was influenced by the presence of co-morbidities,  poor knowledge and understanding of AF and the purpose of anticoagulation. CONCLUSION: Age, complex multimorbidity and polypharmacy influence prescribing, with DOACs being perceived to be safer than warfarin. This systematic narrative review suggests that interventions are needed to support patient self-management. There are residual anxieties associated with long term anticoagulation in the context of complexities. TRIAL REGISTRATION: Not applicable.

Warfarin Pharmacogenomics for Precision Medicine in Real-Life Clinical Practice in Southern Africa: Harnessing 73 Variants in 29 Pharmacogenes.

Pharmacogenomics is universally relevant for worldwide modern therapeutics and yet needs further development in resource-limited countries. While there is an abundance of genetic association studies in controlled medical settings, there is a paucity of studies with a naturalistic design in real-life clinical practice in patients with comorbidities and under multiple drug treatment regimens. African patients are often burdened with communicable and noncommunicable comorbidities, yet the application of pharmacogenomics in African clinical settings remains limited. Using warfarin as a model, this study aims at minimizing gaps in precision/personalized medicine research in African clinical practice. We present, therefore, pharmacogenomic profiles of a cohort of 503 black Africans (n = 252) and Mixed Ancestry (n = 251) patients from Southern Africa, on warfarin and co-prescribed drugs in a naturalized noncontrolled environment. Seventy-three (n = 73) single nucleotide polymorphisms (SNPs) in 29 pharmacogenes were characterized using a combination of allelic discrimination, Sanger sequencing, restriction fragment length polymorphism, and Sequenom Mass Array. The common comorbidities were hypertension (43-46%), heart failure (39-45%), diabetes mellitus (18%), arrhythmia (25%), and HIV infection (15%). Accordingly, the most common co-prescribed drugs were antihypertensives, antiarrhythmic drugs, antidiabetics, and antiretroviral therapy. We observed marked variation in major pharmacogenes both at interethnic levels and within African subpopulations. The Mixed Ancestry group presented a profile of genetic variants reflecting their European, Asian, and African admixture. Precision medicine requires that African populations begin to capture their own pharmacogenetic SNPs as they cannot always infer with absolute certainty from Asian and European populations. In the current historical moment of the COVID-19 pandemic, we also underscore that the spectrum of drugs interacting with warfarin will likely increase, given the systemic and cardiovascular effects of COVID-19, and the anticipated influx of COVID-19 medicines in the near future. This observational clinical pharmacogenomics study of warfarin, together with past precision medicine research, collectively, lends strong support for incorporation of pharmacogenetic profiling in clinical settings in African patients for effective and safe administration of therapeutics.

COVID-19 and Anticoagulation for Atrial Fibrillation: An Analysis of US Nationwide Pharmacy Claims Data.

Background Adherence to oral anticoagulation (OAC) is critical for stroke prevention in atrial fibrillation. However, the COVID-19 pandemic may have disrupted access to such therapy. We hypothesized that our analysis of a US nationally representative pharmacy claims database would identify increased incidence of lapses in OAC refills during the COVID-19 pandemic. Methods and Results We identified individuals with atrial fibrillation prescribed OAC in 2018. We used pharmacy dispensing records to determine the incidence of 7-day OAC gaps and 15-day excess supply for each 30-day interval from January 1, 2019 to July 8, 2020. We constructed interrupted time series analyses to test changes in gaps and supply around the pandemic declaration by the World Health Organization (March 11, 2020), and whether such changes differed by medication (warfarin or direct OAC), prescription payment type, or prescriber specialty. We identified 1 301 074 individuals (47.5% women; 54% age ≥75 years). Immediately following the COVID-19 pandemic declaration, we observed a 14% decrease in 7-day OAC gaps and 56% increase in 15-day excess supply (both P<0.001). The increase in 15-day excess supply was more marked for direct OAC (69% increase) than warfarin users (35%; P<0.001); Medicare beneficiaries (62%) than those with commercial insurance (43%; P<0.001); and those prescribed OAC by a cardiologist (64%) rather than a primary care provider (48%; P<0.001). Conclusions Our analysis of nationwide claims data demonstrated increased OAC possession after the onset of the COVID-19 pandemic. Our findings may have been driven by waivers of early refill limits and patients' tendency to stockpile medications in the first weeks of the pandemic.

Mechanical thrombectomy of COVID-19 DVT with congenital heart disease leading to phlegmasia cerulea dolens: a case report.

BACKGROUND: COVID-19 and Fontan physiology have each been associated with an elevated risk of venous thromboembolism (VTE), however little is known about the risks and potential consequences of having both. CASE PRESENTATION: A 51 year old male with tricuspid atresia status post Fontan and extracardiac Glenn shunt, atrial flutter, and sinus sick syndrome presented with phlegmasia cerulea dolens (PCD) of the left lower extremity in spite of supratherapeutic INR in the context of symptomatic COVID-10 pneumonia. He was treated with single session, catheter directed mechanical thrombectomy that was well-tolerated. CONCLUSIONS: This report of acute PCD despite therapeutic anticoagulation with a Vitamin K antagonist, managed with emergent mechanical thrombectomy, calls to attention the importance of altered flow dynamics in COVID positive patients with Fontan circulation that may compound these independent risk factors for developing deep venous thrombosis with the potential for even higher morbidity.

Association between warfarin and COVID-19-related outcomes compared with direct oral anticoagulants: population-based cohort study.

BACKGROUND: Thromboembolism has been reported as a consequence of severe COVID-19. Although warfarin is a commonly used anticoagulant, it acts by antagonising vitamin K, which is low in patients with severe COVID-19. To date, the clinical evidence on the impact of regular use of warfarin on COVID-19-related thromboembolism is lacking. METHODS: On behalf of NHS England, we conducted a population-based cohort study investigating the association between warfarin and COVID-19 outcomes compared with direct oral anticoagulants (DOACs). We used the OpenSAFELY platform to analyse primary care data and pseudonymously linked SARS-CoV-2 antigen testing data, hospital admissions and death records from England. We used Cox regression to estimate hazard ratios (HRs) for COVID-19-related outcomes comparing warfarin with DOACs in people with non-valvular atrial fibrillation. We also conducted negative control outcome analyses (being tested for SARS-CoV-2 and non-COVID-19 death) to assess the potential impact of confounding. RESULTS: A total of 92,339 warfarin users and 280,407 DOAC users were included. We observed a lower risk of all outcomes associated with warfarin versus DOACs [testing positive for SARS-CoV-2, HR 0.73 (95% CI 0.68-0.79); COVID-19-related hospital admission, HR 0.75 (95% CI 0.68-0.83); COVID-19-related deaths, HR 0.74 (95% CI 0.66-0.83)]. A lower risk of negative control outcomes associated with warfarin versus DOACs was also observed [being tested for SARS-CoV-2, HR 0.80 (95% CI 0.79-0.81); non-COVID-19 deaths, HR 0.79 (95% CI 0.76-0.83)]. CONCLUSIONS: Overall, this study shows no evidence of harmful effects of warfarin on severe COVID-19 disease.

"I just didn't want to trust it at all": Atrial fibrillation patient's treatment experience of rivaroxaban and warfarin.

BACKGROUND: In the treatment of atrial fibrillation (AF), anticoagulant medications such as warfarin and rivaroxaban are commonly prescribed to reduce the risk of ischaemic strokes, and other thromboembolic events. Research has highlighted advantages and disadvantages of each of these medications, but there remains an absence of qualitative evidence regarding the lived experiences of AF patients. The present study helps address this gap and obtain a greater understanding of the patient experience and beliefs surrounding their anticoagulant medication. METHOD: Semi-structured qualitative interviews with a purposive sample of 20 participants (10 warfarin, 10 rivaroxaban). Interviews were transcribed verbatim and thematically analysed. RESULTS: Data analysis led to the generation of three key themes: positive perceptions of medication, distrust of alternatives, and inconsistencies in support experiences. CONCLUSIONS: Positive perceptions of one anticoagulant medication (ACM) and distrust of alternatives may influence patients' confidence in switching medications. This is potentially problematic where there is a lack of patient engagement in medication changes, as seen during the COVID pandemic. Gaps in patient understanding of anticoagulation, including lack of clarity around medications selection and misconceptions about treatment, were evident. By addressing these misconceptions, clinicians may be better positioned to support people with AF in self-management of their ACM.

Extending INR testing intervals in warfarin patients at a multi-center anticoagulation clinic.

Warfarin has been used as an anticoagulant by millions of patients due to its effectiveness, availability, and low cost. Evidence on the safe extension of international normalized ratio (INR) testing frequency remains an area of interest, especially during the recent COVID-19 pandemic. The purpose of this study is to safely extend INR testing intervals in patients throughout a multisite, system-wide anticoagulation clinic. Updates were made to the pharmacist's collaborative practice agreement (CPA) and nurse protocol to optimize practice and allow INR testing interval extension up to a maximum of 8-weeks. The primary outcome was the change in duration between INR tests (INR testing interval) measured before and after providing staff education on clinic updates. The mean duration between INR tests (SD) was 23.69 days (11.29) in the pre-intervention period and 25.58 days (13.91) in the post-intervention period. During the COVID-19 pandemic (post2), intervals were extended further to 27.81 days (14.96), demonstrating a statistically significant increase in INR testing interval from pre-intervention to post-intervention and to post2 (p < 0.001 and p < 0.001, respectively). A secondary outcome indicated the mean time in therapeutic range (SD) showed no significant difference in pre-intervention 70.11% (25.95) versus post-intervention of 69.76% (25.69) with a difference of - 0.35% (29.93) (p = 0.956) or versus the post2 of 68.82% (27.20) with a difference of - 1.29% (33.20) (p = 0.120). This study showed that changes to the CPA and protocol allowed for a significant increase in INR testing interval while simultaneously maintaining a mean time in therapeutic range > 60% for the clinic population.