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J Am Coll Cardiol, 2000; 36:784-787 © 2000 by the American College of Cardiology Foundation |
a Department of Cardiac Electrophysiology, Division of Cardiology, William Beaumont Hospital, Royal Oak, Michigan, USA
Manuscript received July 29, 1999; revised manuscript received March 7, 2000, accepted April 14, 2000.
Reprint requests and correspondence: Dr. Howard I. Frumin, Division of Cardiology, William Beaumont Hospital, 3601 West Thirteen Mile Road, Royal Oak, Michigan 48073-6769
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Abstract |
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The purpose of this study was to evaluate the rate of recognition of atrial fibrillation (AF), use of warfarin and prevalence of cerebrovascular accident (CVA) in paced versus unpaced patients during admission to a tertiary care teaching hospital.
BACKGROUND
The presence of AF underlying a continuously paced rhythm may be under recognized and result in a lower rate of anticoagulation and higher incidence of CVA.
METHODS
The identification of AF on 12 lead electrocardiogram (ECG) and telemetry, "optimal use" of anticoagulants that is, warfarin or aspirin, when warfarin is contraindicated and history of prior CVA was studied in three groups: 1) group A with continuously paced rhythm on ECG and telemetry (n = 30), 2) group B with intermittently paced rhythm on ECG and telemetry (n = 59), and 3) group C with persistent AF and no permanent pacemaker (n = 50).
RESULTS
The identification and documentation of AF was significantly lower in the continuously paced group A (20%) versus the intermittently paced group B (44%). Both groups A and B were substantially lower than unpaced controls. "Optimal use" of anticoagulants was significantly lower in group A (40%) compared with groups B (78%) and C (72%) but was not different between groups B and C. The prevalence of prior CVA was not significantly different between the three groups.
CONCLUSIONS
All ECGs in patients with paced rhythm should be examined closely for underlying AF to prevent under-recognition and under-treatment with anticoagulants.
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Methods |
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The 139 patients were then divided into three groups: 1) group A, 30 patients with continuously paced rhythm on ECG and telemetry and underlying AF, 2) group B, 59 patients with intermittently paced rhythm on ECG or telemetry and underlying AF, 3) Group C, 50 patients with persistent AF without an implanted permanent pacemaker.
Patient characteristics (table 1).
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Statistical analysis. Statistical analysis between the three groups was done using a generalized linear model with the group as the independent variable and age as the dependent variable. The categorical variables were examined using a Pearson chi-square when possible and a Fisher exact test otherwise. Results are reported as mean ± standard deviation. A p value less than 0.05 was considered statistically significant.
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Results |
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Identification of af. Atrial fibrillation was identified and documented within the chart in 6 of 30 patients (20%) in group A compared with 26 of 59 patients (44%) in group B and, by definition, all 50 patients in group C. There was a significant under-recognition of AF in the continuously paced group (A) when compared with the intermittently paced group (B) (p < 0.05) or unpaced controls, group (C).
Anticoagulation at discharge. At discharge, 10 of 30 patients (33%) in group A were anticoagulated with warfarin as opposed to 40 of 59 patients (68%) in group B and 27 of 50 patients (54%) in group C. There was a significant difference between groups A and B and groups A and C; p < 0.01. Contraindications to warfarin were present in 11 of 30 patients (37%) in group A, 11 of 59 patients (19%) in group B and 13 of 50 patients (26%) in group C and were not significantly different among the three groups. In patients with contraindication to warfarin, aspirin was prescribed in 2 of 11 patients (18%) in group A, 6 of 11 patients (55%) in group B and 9 of 13 patients (69%) in group C. The rate of treatment with aspirin was less frequent in group A compared with group C (p < 0.01); however, rate of treatment was not different between groups A and B or between groups B and C. "Optimal use" of anticoagulants, that is, warfarin or aspirin, when warfarin was contraindicated was noted in 12 of 30 patients (40%) in group A, in 46 of 59 patients (78%) in group B and 36 of 50 patients (72%) in group C. There was a significant difference between groups A and B (p < 0.001) and groups A and C (p < 0.01; Fig. 2).
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Discussion |
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Anticoagulation at discharge. Several large randomized trials in patients with nonrheumatic AF have demonstrated a 37% to 86% risk reduction for CVA in groups treated with oral anticoagulation compared with placebo (1–8). In our study a higher prevalence of prior CVA was not observed; however, the sample size was small, the follow-up period short, a prospective analysis for CVA was not performed, nor was there any attempt to quantitatively assess prior risk exposure (e.g., years unprotected AF) between patient groups. Cerebrovascular accident was evaluated solely by history, an admittedly crude index. Prior studies attesting to the benefit of anticoagulation in nonrheumatic AF support the contention that our study group is at increased risk of CVA and mitigates against the role of another prospective trial for this subgroup.
The use of warfarin in patients with AF has been reported to be 40% to 64% of hospitalized patients without contraindication to anticoagulation (12–16). In this report, 54% of unpaced patients received warfarin although >72% were "optimally" treated when both warfarin and aspirin were considered.
Two previous studies address the incidence of anticoagulation in paced patients with underlying AF. Sparks et al. (17) in a study of 53 high-risk patients with AF and permanent pacemakers being followed in an outpatient pacemaker clinic reported that only 8 of 53 patients (15%) were anticoagulated with warfarin. In an earlier report by Langenfeld et al. (18), warfarin was used in only 1 of 63 patients (2%) with permanent pacemakers and AF. This study was published before the randomized trials (1–9) reporting the benefits of warfarin, which may partially explain the findings. We report a higher incidence of warfarin use (56%) in our paced population and "optimal" treatment with warfarin or aspirin in 65%. The subgroup of continuously paced patients had the lowest anticoagulation rate (33%) and rate of "optimal" treatment (40%) and clearly represents a risk exposed subset.
Study limitations. There are several limitations of this study. It was not possible to clarify whether the low rate of identification and documentation of AF, our primary end point, occurred due a diagnostic problem or a judgement error. If physicians do not recognize the need to anticoagulate paced patients with underlying AF, identification of the dysrhythmia will not improve their management.
The link between failure to document AF and the failure to anticoagulate is implied but not proven. Other factors may have been responsible for the low rate of anticoagulation, and our assessment of anticoagulation may overestimate the problem somewhat. For the purpose of this study, we defined "optimal" use of anticoagulation as treatment with warfarin or aspirin when a contraindication to warfarin was documented. Our definition of "optimal use" of anticoagulants may slightly underestimate a true ideal since some patients with contraindication to warfarin also have contraindications to aspirin, and some patients may have had contraindications that were undocumented or missed in our survey.
Finally, the failure to note an increased prevalence of prior CVA in our paced patients was somewhat of a surprise; however, the groups were small, there was no prospective follow-up nor was there any attempt to quantitatively assess prior risk exposure (e.g., years unprotected AF) between patient groups. Nevertheless, we believe the link between AF and CVA is well established and that paced patients are at equal or greater risk than their unpaced counterparts.
Clinical implications. The identification of AF in patients with predominantly paced rhythm on 12 lead ECG is often overlooked. We suspect this is due to the absence of an irregular rhythm. Failure to recognize AF on ECG in patients with continuous pacing suggests under-recognition may have made a significant contribution to under-treatment. Regardless of the reason, that is, failure to recognize or failure to treat, the incidence of anticoagulation at discharge was significantly lower in the continuously paced group compared with the intermittent or unpaced groups. Although this study did not show an increased prevalence of prior CVA in the continuously paced subgroup, there is every reason to anticipate an eventual excess incidence of thromboembolic events in this group. We recommend that all ECGs interpreted as paced rhythms be examined closely for evidence of underlying AF with particular attention to continuously paced rhythms. Atrial fibrillation, if discovered, must be documented and patients treated according to currently accepted guidelines for anticoagulation (19).
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