The interaction effect of CHA2DS2-VASc components on ischemic stroke risk after atrial fibrillation: a population-based cohort study

Background

In the European Union, almost nine million individuals 55 years or older had atrial fibrillation in 2010. It is estimated that around a quarter of all ischemic stroke cases in individuals 80 to 89 years can be attributed to atrial fibrillation. The CHA2DS2-VASc is the most commonly used clinical tool to predict ischemic stroke and incorporates congestive heart failure, hypertension, age 75 years or older, diabetes mellitus, previous stroke/transient ischemic attack/systemic embolism, vascular disease, age 65 to 74 years, and female sex. It remains unknown whether the CHA2DS2-VASc components and atrial fibrillation interact biologically, i.e. whether the CHA2DS2-VASc components and atrial fibrillation increase ischemic stroke rate beyond their individual effects.

Purpose

We examined the interaction effect between CHA2DS2-VASc and atrial fibrillation and on ischemic stroke rate.

Methods

We conducted a population-based cohort study of all adult atrial fibrillation or flutter patients from 1996 through 2016 and a one-to-five comparison cohort from the general population. Members of the comparison cohort were matched on year of birth, sex, and the individual CHA2DS2-VASc components. We followed each individual from the index date (the date of atrial fibrillation or date of matching) until the first of ischemic stroke, death from any cause, loss-to follow-up, 10 years follow-up, or 31 December 2016. We calculated ischemic stroke rates per 1,000 person-years (PYs) and interaction contrasts, which is the proportion of the summed ischemic stroke rate of the CHA2DS2-VASc components and atrial fibrillation that is beyond their individual effects.

Results

After one-year follow-up, the ischemic stroke rate per 1,000 PY among individuals with CHA2DS2-VASc score zero was 5.69 (95% confidence interval [CI]: 4.68–6.69) in the atrial fibrillation cohort and 1.86 (95% CI: 1.60–2.12) in the comparison cohort. Among individuals with CHA2DS2-VASc score one, the mortality rate per 1,000 PY increased to 10.9 (95% CI: 9.75–12.0) in the atrial fibrillation cohort and 7.45 (95% CI: 7.01–7.88) in the comparison cohort. The interaction contrast in individuals with CHA2DS2-VASc score one was −0.41 (10.8 − 7.45 − 5.69 + 1.86) indicating that the ischemic stroke rate was not explained by interaction (−0.41 / 10.8 = −3.8%). The interaction effect was −2.75 in individuals with CHA2DS2-VASc score two and −2.79 in individuals with CHA2DS2-VASc score three or higher, again indicating no interaction. Interaction did not explain the ischemic stroke rate after one to five years follow-up either, but did explain 16% of the ischemic stroke rate in individuals with CHA2DS2-VASc score three or higher after five to 10 years follow-up.

Conclusion

Biological interaction between the CHA2DS2-VASc components and atrial fibrillation does not contribute substantially to the ischemic stroke risk.

Funding Acknowledgement

Type of funding sources: None.

Chronic thromboembolic pulmonary hypertension and mortality after venous thromboembolism: a nationwide population-based cohort study

Background

One of the ultimate long-term complications of venous thromboembolism (VTE) is chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH is a condition defined as an increased mean pulmonary arterial pressure of at least 25 mmHg at rest and abnormal pulmonary artery resistance measured by right heart catheterization. To our knowledge, no study has compared mortality in VTE patients developing CTEPH to those who do not.

Purpose

We aimed to investigate the influence of CTEPH on long-term VTE mortality, by examining how receiving any pulmonary hypertension (PH) diagnosis following VTE influenced mortality.

Methods

We conducted a population-based cohort study of all adult Danish patients with an incident in or outpatient VTE diagnosis from 1995 through 2016. We excluded patients with a previous PH diagnosis. We defined CTEPH as receiving any PH diagnosis within two years following VTE. We categorized VTE by type (deep venous thrombosis [DVT] or pulmonary embolism [PE]) and provoking risk factors. We followed patients from two years after VTE until the first of death, emigration, or 31 December 2016. We calculated mortality rates and standardized mortality rate ratios (SMRs) of the association between PH and all-cause mortality and cause-specific mortality due to cancer and cardiovascular diseases. We also stratified the analyses by baseline presence of comorbidity (congestive heart failure, chronic pulmonary disease, and/or interstitial pulmonary disease).

Results

In 89,062 VTE patients alive two years after their VTE, 724 developed PH. The mortality rate per 1,000 person-years was 121 (95% confidence interval [CI]: 110–134) in patients with PH and 48 (95% CI: 47–48) in patients without PH. The SMR was 2.05 (95% CI: 1.77–2.37) for all VTE patients, 2.20 (95% CI: 1.53–3.16) for DVT patients, and 1.72 (95% CI: 1.47–2.01) for PE patients. The SMR was 1.79 (95% CI: 1.28–2.51) in VTE patients with a provoking VTE risk factor and 2.15 (95% CI: 1.83–2.53) in VTE patients without a provoking VTE risk factor. PH was associated with increased cause-specific mortality due to cardiovascular diseases (SMR=2.31, 95% CI: 1.75–3.06), but not cancer (SMR=0.94, 95% CI: 0.64–1.38). The SMR was 2.36 (95% CI: 2.06–2.71) in patients with comorbidity and 1.80 (95% CI: 1.45–2.24) in patients without comorbidity.

Conclusion

Development of PH, as a measure of CTEPH, within two years following incident VTE was associated with two-fold increased mortality in two-year VTE survivors. The increase in mortality was driven by cardiovascular causes.

Funding Acknowledgement

Type of funding sources: None.

Potential of comorbidity indices and CHA2DS2-VASc to predict ischemic stroke and mortality in patients with atrial fibrillation: a validation study

Background

Atrial fibrillation represents a large health burden and increases the risk of ischemic stroke and mortality. A large proportion of atrial fibrillation patients also has other comorbidities. It remains unknown whether comorbidity burden summarized as a comorbidity score can predict ischemic stroke and mortality after atrial fibrillation. In an aging population burdened with comorbidities, it thus has become increasingly important to understand the impact of comorbidity burden on the prognosis of atrial fibrillation.

Purpose

We examined the ability of the Danish Comorbidity Index for Acute Myocardial Infarction (DANCAMI), the Charlson Comorbidity Index (CCI), the Elixhauser Comorbidity Index (ECI), and the CHA2DS2-VASc to predict ischemic stroke and all-cause mortality within one year after atrial fibrillation or flutter.

Methods

We identified all patients with a first-time atrial fibrillation or flutter hospital diagnosis in Denmark from 2000 through 2015 (n=318,939). We identified all comorbidities in each index using hospital diagnoses in the 10 years before diagnosis of atrial fibrillation or flutter. For each comorbidity index, we calculated Harrell's C-Statistic to predict ischemic stroke, all-cause mortality, and cause-specific mortality due to cardiovascular diseases and cancer within one year after atrial fibrillation or flutter. We also calculated hazard ratios of the association of the DANCAMI comorbidities not included in the CCI with ischemic stroke and all-cause mortality within one year after atrial fibrillation or flutter, after conditioning on age, sex, and all CCI comorbidities.

Results

The C-Statistic to predict ischemic stroke was 0.64 (95% confidence interval [CI]: 0.63–0.64) for DANCAMI, 0.63 (95% CI: 0.63–0.64) for CCI, 0.63 (95% CI: 0.63–0.64) for ECI, and 0.64 (95% CI: 0.63–0.64) for CHA2DS2-VASc. The C-Statistic to predict all-cause mortality was 0.74 (95% CI: 0.74–0.75) for DANCAMI, 0.74 (95% CI: 0.73–0.74) for CCI, 0.73 (95% CI: 0.72–0.73) for ECI, and 0.69 (95% CI: 0.69–0.69) for CHA2DS2-VASc. Among the DANCAMI comorbidities not included in the CCI, five predicted increased risk of ischemic stroke (epilepsy, alcohol and drug abuse, schizophrenia, affective disorder, and chronic kidney disease) and eight predicted increased risk of all-cause mortality (coagulopathy, neurodegenerative disorder, epilepsy, alcohol and drug abuse, schizophrenia, affective disorder, chronic kidney disease, and chronic pancreatitis). Compared with all-cause mortality, DANCAMI was better at predicting mortality due to cardiovascular diseases (C-Statistic=0.79, 95% CI: 0.79–0.80) and cancer (C-Statistic=0.78, 95% CI: 95% CI: 0.76–0.80)

Conclusion

In patients with first-time atrial fibrillation or flutter, no comorbidity index predicted ischemic stroke well. However, DANCAMI predicted all-cause mortality on a par with the CCI and the ECI and better than CHA2DS2-VASc.

Funding Acknowledgement

Type of funding sources: None.