Page 80 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax

Chapter 5
Statistical Analysis
To analyze the relationship between cardiac death and CFVR in the infarct- related or reference vessel, we performed 3 sequential analyses. First, we determined the optimal cut-off value for cardiac mortality of CFVR in both vessels using receiver-operator-characteristics curves. The cut-off values with the highest sum of sensitivity and specificity were used for subsequent analyses. Second, the Kaplan–Meier method was used to estimate cumulative cardiac mortality rates according to the previously identified cut-off values, which were compared by means of the log-rank test. Third, the prognostic value of CFVR in the infarct-related and in the reference vessel was evaluated in 2 sets of Cox proportional hazards models. An univariable model was used to identify variables significantly associated with cardiac mortality. Subsequent multivariable analysis was performed using a stepwise Cox proportional hazards model with adjustments for these variables (P<0.1), and including adjustments for age. Data are presented as mean (±SD), frequency (percentage), or median (25th–75th percentile). Student t test, Mann–Whitney U Test, χ2, or Fisher exact test was used, when appropriate, to test for differences between groups. Event rates are reported as 10-year Kaplan–Meier estimates of cumulative cardiac mortality. A 2-sided α-level of 0.05 was considered statistically significant.
Results
Study Population Characteristics
Complete follow-up was obtained in 94 of the 100 patients (94%). Baseline characteristics of these patients are shown in Table 1.
At the end of the procedure, TIMI 3 flow was achieved in the infarct-related artery in 70 patients (75%), and myocardial blush grade 3 was achieved in 50 patients (52%). Mean CFVR in the infarct-related artery was 1.6±0.4 (median, 1.5; 25th–75th percentile 1.3–1.8) in contrast to 2.4±0.5 (median, 2.3; 25th– 75th percentile 2.0–2.7) in the reference vessel (left circumflex coronary artery in 84 patients [89%]; right coronary artery in 10 patients [11%]). A rapid DDT, defined as DDT <600 ms, was found in 49 patients (52%), and SRF was present in 27 patients (29%).
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