CHADS2 score

Burning Bridges: Must Warfarin Be Stopped for Device Implantation?

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In a randomized trial, heparin bridging for implantation of a pacemaker or implantable cardioverter-defibrillator was associated with an increase in device-pocket hematoma.

Warfarin increases the risk for bleeding. Surgery is associated with bleeding. The intuitive inference that patients should discontinue chronic warfarin therapy before undergoing surgery, combined with concern about the ensuing thromboembolic risk, has led to the standard use of intravenous heparin or subcutaneous low-molecular-weight heparin as an anticoagulation “bridge” during warfarin washout. However, some practitioners question the benefits of this practice.

In a multicenter trial, 681 warfarin recipients undergoing permanent pacemaker or implantable cardioverter-defibrillator implantation were randomized to continue warfarin or to discontinue warfarin with a heparin bridge for 5 days before surgery. All patients had an estimated annual risk for thromboembolism of 

≥5% (mean CHADS2 score, 3.4). The trial was stopped early because of a strongly significant increase in the rate of device-pocket hematoma in the heparin-bridging group compared with the warfarin-continuation group (16.0% vs. 3.5%). Two patients in the warfarin-continuation group experienced stroke or transient ischemic attack (compared with none in the heparin-bridging group); however, both had subtherapeutic international normalized ratios at the time of surgery.

Comment: These data confirm what many surgeons and electrophysiologists observe on a daily basis — heparin bridging during warfarin interruption increases bleeding risk even more than continuing warfarin does. The findings are important for patients with atrial fibrillation and a high annual risk for thromboembolism. Whether warfarin can be withheldwithout bridging in individuals at low risk for thromboembolism remains unstudied. For such patients, an effective strategy might be to stop warfarin 1 or 2 days — rather than the traditional 5 days — before surgery.

 

Source:Journal Watch Cardiology

 

 

 

Derivation and validation of QStroke score for predicting risk of ischaemic stroke in primary care and comparison with other risk scores: a prospective open cohort study.

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Abstract

Objective To develop and validate a risk algorithm (QStroke) to estimate risk of stroke or transient ischaemic attack in patients without prior stroke or transient ischaemic attack at baseline; to compare (a) QStroke with CHADS2 and CHA2DS2VASc scores in patients with atrial fibrillation and (b) the performance of QStroke with the Framingham stroke score in the full population free of stroke or transient ischaemic attack.

Design Prospective open cohort study using routinely collected data from general practice during the study period 1 January 1998 to 1 August 2012.

Setting 451 general practices in England and Wales contributing to the national QResearch database to develop the algorithm and 225 different QResearch practices to validate the algorithm.

Participants 3.5 million patients aged 25-84 years with 24.8 million person years in the derivation cohort who experienced 77 578 stroke events. For the validation cohort, we identified 1.9 million patients aged 25-84 years with 12.7 million person years who experienced 38 404 stroke events. We excluded patients with a prior diagnosis of stroke or transient ischaemic attack and those prescribed oral anticoagulants at study entry.

Main outcome measures Incident diagnosis of stroke or transient ischaemic attack recorded in general practice records or linked death certificates during follow-up.

Risk factors Self assigned ethnicity, age, sex, smoking status, systolic blood pressure, ratio of total serum cholesterol to high density lipoprotein cholesterol concentrations, body mass index, family history of coronary heart disease in first degree relative under 60 years, Townsend deprivation score, treated hypertension, type 1 diabetes, type 2 diabetes, renal disease, rheumatoid arthritis, coronary heart disease, congestive cardiac failure, valvular heart disease, and atrial fibrillation

Results The QStroke algorithm explained 57% of the variation in women and 55% in men without a prior stroke. The D statistic for QStroke was 2.4 in women and 2.3 in men. QStroke had improved performance on all measures of discrimination and calibration compared with the Framingham score in patients without a prior stroke. Among patients with atrial fibrillation, levels of discrimination were lower, but QStroke had some improved performance on all measures of discrimination compared with CHADS2 and CHA2DS2VASc.

Conclusion QStroke provides a valid measure of absolute stroke risk in the general population of patients free of stroke or transient ischaemic attack as shown by its performance in a separate validation cohort. QStroke also shows some improvement on current risk scoring methods, CHADS2 and CHA2DS2VASc, for the subset of patients with atrial fibrillation for whom anticoagulation may be required. Further research is needed to evaluate the cost effectiveness of using these algorithms in primary care.

 

What is already known on this topic

  • Methods to identify patients at high or low risk of stroke are needed to identify patients for whom interventions may be required, especially those with atrial fibrillation for whom anticoagulation might be needed
  • Current methods for risk scoring, such as CHADS2 and CHA2DS2VASc, are not based on a statistical model, do not include many established risk factors, nor provide absolute risk estimates of stroke
  • We have developed a new algorithm to quantify absolute risk of primary stroke which includes established risk factors and which is designed to work with the QRISK2 cardiovascular disease algorithm
  • QStroke provides a valid measure of absolute stroke risk in the general population of patients free of stroke or transient ischaemic attack as shown by its performance in a separate validation cohort
  • QStroke shows some improvement on current risk scoring methods, CHADS2and CHA2DS2VASc, for the subset of patients with atrial fibrillation for whom anticoagulation may be required
  • Further research is needed to evaluate the clinical outcomes and cost effectiveness of using these algorithms in primary care

What this study adds

 

Source: BMJ