Atrial fibrillation: risk factors included heart disease and hypertension.

Clinical bottom line (level 1b)

  1. Around 7% of people developed atrial fibrillation.
  2. Patients were at an increased risk of developing AF if they had:
    • cardiomyopathy (NNF = 4 for 44 years)
    • myocardial infarction (NNF = 7 for 44 years)
    • valvular heart disease (NNF = 7 for 44 years)
    • heart failure (NNF = 7 for 44 years)
  3. Other risk factors included palpitations and hypertension.
Krahn et al: American Journal of Medicine 1995; 98: 476-484
Expires November 2003

The study

Prospective cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: community, Canada

3983 patients (aged range 18 to 62; mean 31, 100% male) fit for pilot training

Excluded if
  • if in atrial fibrillation on first examination



    • Factors studied:
  • atrial fibrillation
  • cardiomyopathy
  • MI
  • congestive heart failure
  • valvular heart disease
  • angina
  • palpitations
  • supraventricular arrhythmia
  • ST or T wave changes
  • ventricular rhythm disturbance
  • hypertension
  • obesity




    • Multivariate Cox proportional hazard analysis performed on prognostic factors.

    98% followed for 44 years
    Outcomes studied:
  • atrial fibrillation

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    atrial fibrillation 44 years 299/3983 7.5%
    (6.7% to 8.3%)

    prognostic factor for
    atrial fibrillation     		time to outcome adjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    cardiomyopathy 44 years 4.07
    (1.45 to 11.45)     		4
    (1 to 30)
    MI 44 years 3.62
    (2.59 to 5.07)     		7
    (4 to 11)
    congestive heart failure 44 years 3.37
    (2.29 to 4.96)     		7
    (4 to 12)
    valvular heart disease 44 years 3.15
    (1.99 to 5.00)     		7
    (4 to 15)
    angina 44 years 2.84
    (1.91 to 4.21)     		8
    (5 to 17)
    palpitations 44 years 2.22
    (1.24 to 2.97)     		12
    (7 to 60)
    supraventricular arrhythmia 44 years 2.28
    (1.74 to 2.98)     		14
    (9 to 25)
    ST or T wave changes 44 years 2.21
    (1.62 to 3.00)     		22
    (14 to 44)
    ventricular rhythm disturbance 44 years 1.37
    (1.06 to 1.78)     		50
    (24 to 310)
    hypertension 44 years 1.42
    (1.10 to 1.84)     		68
    (34 to 290)
    obesity 44 years 1.28
    (1.02 to 1.62)     		110
    (47 to 1500)

    Comments

    1. The lack of standardisation in reporting of results and concomitant medications weaken these results.
    2. It is unclear if the female population and those with a lower level of physical fitness would have the same risk factors.

    Citation

    1. Krahn AD, Manfreda J, Tate RB, et al: The natural history of atrial fibrillation: incidence, risk factors, and prognosis in the Manitoba follow-up study. American Journal of Medicine 1995; 98: 476-484
    Contributor: Chris Ball and Clare Wotton, November 2000
    Reviewer: Hidenori Kawanishi

    Clinical Question.
    Patient fit men
    Intervention or Exposure risk factors
    Outcome atrial fibrillation