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Canadian Journal of Cardiology

Do All Patients With Atrial Fibrillation Need a Cardiologist?

  • Stephen B. Wilton
    Correspondence
    Corresponding author: Dr Stephen B. Wilton, GE64 3280 Hospital Dr NW, Calgary, Alberta T2N 4Z6, Canada. Tel.: +1-403-210-7102; fax: +1-403-210-9180.
    Affiliations
    Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
    Search for articles by this author
      Atrial fibrillation (AF) is a 21st-century global cardiovascular epidemic, with increasing incidence, prevalence, and burden of disability reported in many countries.
      • Chugh S.S.
      • Havmoeller R.
      • Narayanan K.
      • et al.
      Worldwide epidemiology of atrial fibrillation: a Global Burden of Disease 2010 Study.
      Many clinicians will be familiar with the estimates on the basis of older data that 1 in 4 adults older than the age of 40 years will develop AF in their lifetime.
      • Lloyd-Jones D.M.
      • Wang T.J.
      • Leip E.P.
      • et al.
      Lifetime risk for development of atrial fibrillation: the Framingham Heart Study.
      This sobering figure might in fact be an underestimate, because recent studies indicate the more intensely we screen for AF in at-risk individuals, the more we find: 3%-4% with simple community-based screening of elderly individuals, and now 34% of participants during 1 year of monitoring with an implantable loop recorder in the Prevalence of Sub-Clinical Atrial Fibrillation Using an Implantable Cardiac Monitor (ASSERT-II) trial.
      • Sandhu R.K.
      • Dolovich L.
      • Deif B.
      • et al.
      High prevalence of modifiable stroke risk factors identified in a pharmacy-based screening programme.
      • Svennberg E.
      • Engdahl J.
      • Al-Khalili F.
      • et al.
      Mass screening for untreated atrial fibrillation: the STROKESTOP study.
      • Gladstone D.J.
      • Spring M.
      • Dorian P.
      • et al.
      Atrial fibrillation in patients with cryptogenic stroke.
      • Healey J.S.
      • Alings M.
      • Ha A.C.
      • et al.
      Subclinical atrial fibrillation in older patients.
      Coupled with our aging population, wider implementation of even basic screening programs will lead to a large increase if the number of Canadians diagnosed with AF. Thus, organizing and delivering high-quality AF care to the population, already a challenge, will become even more difficult in the near future.
      To date, there are few data documenting the delivery of AF care in Canada at the population level, and whether different delivery models are associated with improved guideline adherence and/or clinical outcomes at a population level. This is a critical gap in knowledge that Singh and colleagues have attempted to address in this issue of the Canadian Journal of Cardiology with their article entitled, “The Relationship Between Cardiologist Care and Clinical Outcomes in Patients with New-Onset Atrial Fibrillation.”
      • Singh S.M.
      • Qiu F.
      • Webster L.
      • et al.
      The relationship between cardiologist care and clinical outcomes in patients with new-onset atrial fibrillation.
      This article reports the results of a retrospective observational cohort study of the Ontario population using administrative and physician claims data held by the Institute of Clinical Evaluative Sciences. The objective was to evaluate the association between care by a cardiologist and long-term outcomes among patients 20-80 years of age who were discharged from the emergency department between 2010 and 2012 with a new primary diagnosis of AF. From an original cohort of 22,032, propensity score matching was used to create a 1:1 matched cohort between the 85% of patients seen by a cardiologist at least once within 1 year of an index emergency department visit, and the 15% who were not, with a resulting sample size of 5804. The principal findings reported by the authors were that 6.5% of patients died within 1 year of their initial emergency room visit, and that cardiologist care was associated with reduced mortality (5.3% vs 7.7%; hazard ratio, 0.68; 95% confidence interval, 0.55-0.84; P < 0.001). Cardiologist care was also associated with increased risk for stroke, hospitalization for heart failure, and increased use of cardiovascular procedures.
      The most startling finding from this study was the high rate of death in the cohort overall. The patients were not particularly old (the mean age was younger than 64 years, and those older than 80 years of age were excluded), and the burden of comorbidity was not excessive (the median Congestive Heart Failure, Hypertension, Age (≥75 years), Diabetes, Stroke/Transient Ischemic Attack, Vascular Disease, Age [65-74 years], Sex [Female] [CHA2DS2-VASc] score was 3, less than 14% had a previous diagnosis of heart failure, and only 2.5% had a previous diagnosis of stroke). For reference, this rate of mortality (between 5.3% and 7.7%) is higher than that seen in those discharged alive after an uncomplicated ST-elevation myocardial infarction in a Canadian population-based study (1-year mortality of 3.9%).
      • Kaul P.
      • Ezekowitz J.A.
      • Armstrong P.W.
      • et al.
      Incidence of heart failure and mortality after acute coronary syndromes.
      Causes of death were not reported in this study, but in a recent global epidemiological study, in which the rate of death by 1 year after an emergency room visit with a primary diagnosis of AF was also 6%, the most common causes of death in North America, Western Europe, and Australia were heart failure, other cardiovascular conditions, and stroke.
      • Healey J.S.
      • Oldgren J.
      • Ezekowitz M.
      • et al.
      Occurrence of death and stroke in patients in 47 countries 1 year after presenting with atrial fibrillation: a cohort study.
      Therefore, a new diagnosis of AF, although not immediately life-threatening, should be regarded as an important marker of near-term risk of cardiovascular events. This observation alone provides a potential rationale for desiring early cardiovascular specialist evaluation for these patients.
      All clinicians like to think that their care adds value. Cardiologists, this author included, have more training and experience with the management of AF than do primary care providers, and so it is tempting to take these results at face value, pat ourselves on the back, and perhaps argue for increased access to specialist services. To be sure, this study has important strengths. The authors have used very rigourous methods to identify and mitigate the risks for bias inherent in this type of analysis. This includes matching for a long list of cardiovascular and noncardiovascular comorbidities, income, and place of residence, randomizing the inception date for the group not seen by a cardiologist to mitigate immortal time bias, and inclusion of a negative tracer outcome (pneumonia hospitalization) to assess for a healthy user bias. In short, the authors have done an admirable job of using the data that they had to address their question.
      However, before we accept these results, we need to consider a few limitations. The most important of these is that the results in their totality are not easily explained. Cardiology care would be mainly expected to reduce mortality by increasing use of evidence-based medicine to prevent stroke, prevent and treat heart failure, and manage other cardiovascular risks, which we have seen are the most important causes of death in these patients. However, in this analysis, admissions for heart failure as well as for stroke were more frequent in those cared for by cardiologists. In the discussion, the authors provide a possible explanation for a link between increased heart failure or stroke admission and decreased mortality via increased use of aggressive interventions and risk reduction strategies. They reference another study using Institute of Clinical Evaluative Sciences data showing improved survival after heart failure admission in those cared for by cardiologists vs other providers.
      • Jong P.
      • Gong Y.
      • Liu P.P.
      • et al.
      Care and outcomes of patients newly hospitalized for heart failure in the community treated by cardiologists compared with other specialists.
      However, this analogy does not hold: in that study even those admitted with heart failure under the care of a cardiologist had a 28% 1-year mortality rate. It is difficult to argue that being hospitalized for heart failure or a stroke is better for you than not developing these problems. Importantly, these seemingly paradoxical associations were not seen in a recently published and similar study conducted in the US Veterans Affairs health care system.
      • Perino A.C.
      • Fan J.
      • Schmitt S.K.
      • et al.
      Treating specialty and outcomes in newly diagnosed atrial fibrillation: from the TREAT-AF study.
      In that study, cardiologists' care of patients with AF was associated with decreased risk of stroke, a neutral effect on heart failure hospitalization, and a lesser decrease in mortality.
      Other limitations of this study stem from what the data cannot tell us: how, and why patients were referred to a cardiologist, and importantly whether the 15% of those not seen were never referred, or whether they declined a referral. Those declining a cardiology referral might be less likely to adhere to other physician recommendations. We know that those not seen by a cardiologist were less likely to fill a prescription for oral anticoagulants, but we do not know the proportion of those who received but did not fill prescriptions. However, among those not referred, a risk-referral paradox might be in play. In my own practice, I have certainly seen examples of a bias against referral to cardiology (and even sometimes reluctance by cardiologists to accept referrals) for the sickest patients with AF and other cardiac conditions. The absence of a difference in pneumonia hospitalizations in this study is reassuring, but not sufficient to exclude this possibility. Although those not seen by a cardiologist were likely to see a family physician and/or an internist, those in the cardiology group were even more likely to visit these practitioners. Therefore, prompt access to collaborative care, regardless of who is delivering it, might be an important factor mediating survival advantage.
      Current Canadian and international clinical guideline documents for management of AF express no preference for specialist vs primary care delivery for patients with AF.
      • Healey J.S.
      • Parkash R.
      • Pollak T.
      • Tsang T.
      • Dorian P.
      Canadian Cardiovascular Society atrial fibrillation guidelines 2010: etiology and initial investigations.
      • January C.T.
      • Wann L.S.
      • Alpert J.S.
      • et al.
      2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society [erratum in: 2014;64:2305-7].
      The results of this study will not shift these recommendations, and in my opinion that is just fine. Even if it were possible for every patient with AF to be cared for by a cardiologist, this should be unnecessary. Especially in the increasing proportion of those with AF who are asymptomatic, we can empower family physicians to perform initial investigations and initiate stroke prevention therapy. Instead of mandating that all patients with AF see a cardiologist, we should seek to promote collaborative, patient-centred models of care delivery that work within local contexts and preserve the vital role of primary care providers.

      Disclosures

      The authors have no conflicts of interest to disclose.

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