Long-term survival after coronary bypass surgery and ...

[Pages:7]Open Heart: first published as 10.1136/openhrt-2016-000489 on 24 October 2016. Downloaded from on November 15, 2023 by guest. Protected by copyright.

Coronary artery disease

Long-term survival after coronary bypass surgery and percutaneous coronary intervention

Per M?lstad, Rasmus Moer, Olaf R?devand

To cite: M?lstad P, Moer R, R?devand O. Long-term survival after coronary bypass surgery and percutaneous coronary intervention. Open Heart 2016;3:e000489. doi:10.1136/openhrt-2016000489 Received 20 June 2016 Revised 9 September 2016 Accepted 20 September 2016

Department of cardiology, LHL Clinics Feiring, Feiring, Norway Correspondence to Dr Per M?lstad; moelsta@online.no

ABSTRACT Objectives: To assess whether there exists a long-

term difference in survival after treatment with coronary bypass surgery or percutaneous coronary intervention in patients with coronary disease as judged by all-cause mortality.

Methods: Retrospective study from the Feiring Heart

Clinic database of survival in 22 880 patients--15 078 treated with percutaneous coronary intervention and 7802 with bypass surgery followed up to 16 years.

Results: Cox regression and propensity score analysis

showed no difference in survival for one-vessel and two-vessel disease during the whole study period. In three-vessel disease, however, the analysis revealed a consistent and highly significant survival benefit in the first 8 years with an HR of 0.76 (95% CI 0.69 to 0.84, pt) was calculated for each year. The model with the highest log-likelihood was considered the most appropriate model to use.

Selection bias was addressed by propensity score analysis. A logit model was built from baseline variables

predicting treatment allocation (PCI=0, CABG=1). Continuous variables were checked for linearity in logit. All significant variables and interaction were kept in the model that was tested for goodness-of-fit by the Hosmer and Lemeshow test. From the model, the c-statistic was calculated (area under the receiver operating (ROC) curve). The propensity scores were calculated from the logit model. The scores were used as a single adjusting covariate in a Cox regression and the logit of the propensity score was used for 1:1 matching without replacement and a caliper width of 0.2 times the SD of the logit of the propensity score.14 The matched pairs were then used in a Cox regression stratified on pairs. In all Cox regressions, the robust version of calculating SEs was employed.

The effect of an unmeasured binary confounder on the HR for the treatment effect from the Cox model was evaluated using the method of Lin et al.15

All analyses were performed in STATA V.14 (College Station, Texas, USA), and the propensity matching with the STATA program psmatch2.

RESULTS A total of 22 880 patients were eligible for the analysis with known survival status on 20 September 2015, of whom 15 078 were treated with PCI and 7802 with CABG. The study end point was all-cause mortality and was encountered in 5408 patients. The total time at risk was 177 371 patient years in the whole population with 114 115 years in the PCI cohort and 63 256 years in the CABG treatment group. The median time at risk was 7.2 years for the PCI group and 7.9 years for the CABG group.

Baseline demographics, clinical and angiographical data are given in table 1.

The Kaplan-Meier plot of the unadjusted mortality according to treatment strategy is shown in figure 1. From table 1, it is evident that the cohorts have different values for many covariates expected to affect survival. Typically, the surgical cohort is older and has general arteriosclerosis, diabetes and three-vessel disease more frequently.

The variables from table 1 were tested for inclusion in a multivariable Cox model by a forward selection process. The final model contained 13 main effects and one interaction. In fact, a number of interactions were statistically significant, but the only interesting one pertaining to these analyses was the interaction between the number of the diseased vessel and strategy. The other significant interactions had a minimal effect on the other covariates and were not interesting for the present analysis. A Kaplan-Meier plot of mortality in the two strategies for one-vessel, two-vessel and three vessel disease is shown in figure 2. The linktest for the final model was negative and a plot of Cox-Snell residuals versus the Nelson-Aalen estimator indicated a reasonable goodness-of-fit. Proportional hazard assumption was

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M?lstad P, Moer R, R?devand O. Open Heart 2016;3:e000489. doi:10.1136/openhrt-2016-000489

Open Heart: first published as 10.1136/openhrt-2016-000489 on 24 October 2016. Downloaded from on November 15, 2023 by guest. Protected by copyright.

Coronary artery disease

Table 1 Baseline demographic and clinical variables

Variable

PCI N=15 078

CABG N=7802

p Value

Age years (mean?SD) Gender (male/female) % Ejection fraction % (mean?SD) LVEDP mm Hg (mean?SD) Generalised arteriosclerosis % (number) Other significant disease % (number) Exercise ECG % (number) Not performed Negative exercise test Inconclusive result Ischaemic exercise response CCS function class % (number)

0 I II III IV Unstable angina % (number) Diabetes % (number) Hypertension % (number) Current smoker % (number) Previous myocardial infarction % (number) Previous PCI % (number) Previous CABG % (number) Radial entry site % (number) Coronary angiography One-vessel disease % (number) Two-vessel disease % (number) Three-vessel disease % (number)

65?11 73.0/27.0 68?12 14.1?4.8 4.6 (696) 6.2 (933)

37.4 (5281) 9.9 (1395) 25.1 (3536) 27.7 (3904)

1.9 (254) 5.9 (809) 37.7 (5143) 40.5 (5519) 14.1 (1917) 29.3 (4416) 13.3 (1998) 32.5 (4904) 21.6 (3253) 36.3 (5450) 17.0 (2549) 12.5 (1878) 84.2 (12 701)

46.2 (7029) 30.1 (4534) 23.3 (3515)

67?10 78.2/21.8 67?12 15.3?5.9 7.0 (548) 5.6 (438)

29.2 (2155) 6.0 (444) 20.5 (1511) 44.4 (3279)

1.9 (137) 4.7 (336) 33.5 (2374) 46.8 (3316) 13.0 (924) 27.0 (2106) 16.4 (1278) 36.5 (2845) 19.4 (1512) 36.5 (2843) 8.4 (655) 2.1 (163) 82.4 (6430)

2.2 (175) 17.9 (1400) 79.8 (6227)

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