AF and long-term mortality
All-cause mortality occurred in 568 out of 2,628 patients (21.6%) at a
median follow-up of 4 [2-7] years. Preoperative AF was highly
predictive of mortality (97/ 268 (36.1%) deaths in AF group vs 471/
2,360 (19.9%) in SR group; HR: 2.24, 95% CI: 1.79-2.79,
P<0.001). The Kaplan-Meier survival curves separated early and
the difference remained constant for up to 10 years follow-up [Figure
1].
Of the baseline characteristics in Table 1, the following were
associated with long-term all-cause mortality using univariate hazard
regression model of Cox: increasing age (HR: 1.07, 95% CI: 1.06-1.08,
P<0.001), bioprostheses (HR: 3.30, 95% CI: 2.28-4.77,
P<0.001), hypertension (HR: 1.37, 95% CI: 1.14-1.63,
P<0.001), diabetes (HR: 1.59, 95% CI: 1.31-1.95,
P<0.001), raised preoperative serum creatinine (HR: 1.006,
95% CI: 1.005-1.007, P<0.001), chronic pulmonary disease (HR:
1.56, 95% CI: 1.29-1.89, P<0.001), peripheral vascular
disease (HR: 2.03, 95% CI: 1.55-2.66, P<0.001), previous
myocardial infarction (HR: 1.59, 95% CI: 1.16-2.17, P=0.006), poor left
ventricular function (HR: 1.66, 95% CI: 1.24-2.23, P=0.002), and high
EuroSCORE I (HR: 1.29, 95% CI: 1.26-1.34, P<0.001)
[Supplemental table 1].
The following variables were then entered into the final baseline
multivariate Cox proportional hazard model: age, hypertension, diabetes,
preoperative serum creatinine, chronic pulmonary disease, peripheral
vascular disease, pervious myocardial infarction, and left ventricular
function. We did not include bioprostheses in the model, as we felt this
reflects advanced age in the preoperative AF group rather than being a
genuine risk factor. Similarly, we did not include EuroSCORE I in the
model as we felt it would be a repetition, since EuroSCORE I
incorporates risk factors already included in the model, such as age,
chronic pulmonary disease, peripheral vascular disease, serum creatinine
and left ventricular function. Multivariate analysis showed that AF
remained significantly associated with long-term all-cause mortality
after adjustment for other risk factors (HR: 1.54, 95% CI: 1.21-1.96,
P<0.001) and after bootstrap resampling, the
optimism-corrected c-index was -0.012 and the calibration slope was
0.906, which suggests no over fitting of the model. Other independent
predictors of long-term mortality included advanced age (HR: 1.06, 95%
CI: 1.05-1.08, P<0.001), presence of diabetes (HR: 1.46, 95%
CI: 1.18-1.80, P=0.001), chronic pulmonary disease (HR: 1.44, 95% CI:
1.17-1.77, P=0.001), peripheral vascular disease (HR: 1.48, 95% CI:
1.11-1.97, P=0.001), poor left ventricular function (HR: 1.47, 95% CI:
1.04-2.08, P=0.031) and raised preoperative serum creatinine (HR: 1.005
95% CI: 1.003-1.007, P<0.001).
In a propensity score matching analysis, the risk of long-term all-cause
mortality was higher in the preoperative AF cohort (OR: 1.47, 95% CI:
1.04-1.99, P=0.031) compared with the preoperative SR cohort after
adjustment of baseline differences between the two groups
[Supplemental Table 2, Supplement Table 3 and Supplemental Figure
1].