Methods

As described previously, 287 patients from the United States and Canada were enrolled in a randomized trial designed to determine whether PCI plus OMT, when used as an initial management strategy, reduces the risk of all-cause mortality or nonfatal myocardial infarction in patients with stable CAD compared with OMT alone. CKD was not an exclusion criterion to enrollment, and there was no upper creatinine cutoff value. Glomerular filtration rate was estimated by the abbreviated 4-variable Modification of Diet in Renal Disease equation. CKD was defined as a glomerular filtration rate of <60 ml/min/1.73 m ² . Intensive guideline-directed therapy and lifestyle intervention were applied equally to all patients.

Angina-related health status was measured by SAQ, which was obtained at baseline, 1, 3, 6, and 12 months, and annually thereafter. The SAQ is a self-administered 19-item questionnaire that can be completed in <5 minutes and quantifies disease-specific health status in 5 domains: (1) physical limitations due to angina (e.g., limiting activities to avoid angina), (2) recent change in the severity of angina, (3) the frequency of angina, (4) satisfaction with treatment for angina, and (5) angina-related quality of life. Scores range from 0 to 100, with higher scores indicating better health status. For responder analyses, clinical significance of changes in each of the SAQ scales was determined by the criteria of Wyrwich et al, in which a change of ≥8 points on the physical limitation domain, ≥25 on the angina stability domain, ≥20 on the angina frequency domain, ≥12 on the treatment satisfaction domain, and ≥16 on the quality of life domain were considered clinically significant.

Means of observed scores for each SAQ domain at each time point were analyzed with unpaired t tests, comparing PCI plus OMT versus OMT alone for patients with or without CKD. Linear mixed-effects models were used to analyze SAQ scores longitudinally. These models included the main effects for treatment status, CKD status and time, as well as all 2-way interactions (treatment × time, CKD × time, and treatment × CKD) and the 3-way interaction (treatment × CKD × time). In addition, quadratic terms of time were included to account for nonlinear trends. In these analyses, missing data were considered missing at random. A second set of analyses treated intermittent missing data (e.g., valid values at 3 and 12 months, but a missing value at 6 months) as missing at random and were imputed using the method of multiple partial imputation. The time point after the last available score for a given patient was considered the dropout point. Dropout was considered nonignorable, and the data were analyzed with a pattern mixture model l. Finally, the aforementioned analyses were repeated including age, gender, race, diabetes, heart failure, and hypertension as covariates.

The proportion of patients with clinically significant increases in SAQ scores as defined previously were analyzed by chi-square tests for 2 by 2 tables comparing PCI plus OMT versus OMT alone with respect to change from baseline for participants with and without CKD. These analyses were performed at each time point. Longitudinal analyses were made by a generalized estimating equation for repeated measurements and were used to calculate adjusted percentage of patients with clinically significant improvement (yes or no) at each time point. These analyses included main effects for treatment status, CKD status and time, as well as all 2 interactions described previously. The same covariates included in the mixed models were also included in the general estimating exchange models.

All analyses were truncated at 36 months because data were not available for an increasingly large proportion of patients at later time points. A level of significance of p <0.01 was used for all subgroup analyses and interactions.

The study was approved by institutional review committees at each participating site, and all patients gave informed consent.

Results

There were 2,029 patients with available glomerular filtration rate data from which CKD status could be calculated. Among patients treated with PCI plus OMT, 143 (14%) had CKD, whereas among patients treated with OMT alone, 167 (17%) had CKD. Table 1 compares demographic and clinical data for PCI plus OMT versus OMT alone, stratified by CKD status. There were no significant differences between PCI plus OMT and OMT alone for patients with and without CKD for any of the observed variables, including average Canadian Cardiovascular Society angina class score (1.8 ± 1.0 vs 1.7 ± 1.1, p = 0.552 respectively for patients with CKD and 1.7 ± 1.0 vs 1.6 ± 0.9, p = 0.246 for patients without CKD). However, patients with CKD, regardless of treatment, were older, more likely to be women and to have diabetes mellitus, hypertension, heart failure, and Canadian Cardiovascular Society angina class ≥3 (p <0.01 for all).

Table 2 lists PCI plus OMT versus OMT comparisons of observed domain means according to the CKD status. Mean scores for all but treatment satisfaction, which began high, increased substantially from baseline to 1 month for both PCI plus OMT and OMT alone, and then plateaued in both patients with and without CKD. The nonadjusted longitudinal analyses taking into account missing data showed similar results. For the physical limitation domain, there was a significant treatment status × CKD status interaction (p = 0.006), but this was due primarily to a difference in baseline scores. For treatment satisfaction, there was a significant effect of treatment status (p = 0.003). Patients treated with PCI plus OMT had better scores than patients treated with OMT alone whether they had CKD or not. The interaction treatment status × CKD status was not significant (p = 0.063) but was for the CKD status × time (p = 0.022), suggesting a different rate of improvement for those with and without CKD. Patients with CKD had lower treatment satisfaction scores at baseline than patients without CKD but increased at a greater rate and were similar to non-CKD scores from 12 months onward ( Figure 1 ). CKD status was no significant factor influencing change in the quality of life or angina frequency domains. There was a significant treatment status × time interaction for the angina frequency (p = 0.003) domain. For angina frequency, scores of patients treated with PCI plus OMT were higher than in patients treated with OMT alone through 12 months of follow-up but were essentially at the same level by 36 months ( Figure 1 ).

Table 2

Seattle Angina Questionnaire means, SDs, and sample size by chronic kidney disease (CKD) status, treatment, and follow-up

Domain	Visit	CKD					No CKD
		PCI Plus OMT		OMT Alone		p	PCI Plus OMT		OMT Alone		p
		n	Mean ± SD	n	Mean ± SD		n	Mean ± SD	n	Mean ± SD
Physical limitations	Baseline	109	54.7 ± 25.6	142	63.6 ± 26.2	0.008	765	67.1 ± 24.5	692	66.4 ± 25.0	0.60
	1 month	104	65.5 ± 24.6	120	67.8 ± 23.7	0.47	689	74.1 ± 23.5	635	69.8 ± 24.3	0.003
	3 month	108	65.0 ± 24.1	119	68.6 ± 23.8	0.26	685	77.1 ± 23.0	629	72.9 ± 23.3	<0.001
	6 month	98	67.9 ± 24.7	117	64.9 ± 27.1	0.39	717	77.8 ± 22.6	606	73.2 ± 23.5	<0.001
	1 yr	96	66.0 ± 26.1	114	70.5 ± 27.0	0.22	682	75.6 ± 23.8	599	73.2 ± 23.4	0.07
	2 yrs	90	68.0 ± 23.8	97	71.3 ± 24.7	0.36	600	74.1 ± 24.3	551	71.4 ± 24.2	0.06
	3 yrs	64	65.1 ± 26.6	72	72.0 ± 26.0	0.13	474	74.8 ± 23.8	448	73.6 ± 23.4	0.43
Quality of life	Baseline	116	47.1 ± 23.3	151	51.1 ± 26.2	0.20	787	51.8 ± 24.9	702	51.6 ± 24.8	0.99
	1 month	108	67.4 ± 23.2	128	63.2 ± 24.0	0.17	707	67.8 ± 23.6	657	61.3 ± 24.1	<0.001
	3 month	110	71.9 ± 21.8	125	68.5 ± 22.7	0.25	701	73.1 ± 22.1	639	68.2 ± 23.1	<0.001
	6 month	104	71.6 ± 24.7	118	67.0 ± 24.7	0.14	729	75.1 ± 21.8	622	70.8 ± 22.6	<0.001
	1 yr	100	73.9 ± 22.3	121	75.8 ± 21.9	0.52	694	75.6 ± 20.9	608	71.7 ± 22.4	0.001
	2 yrs	91	93.1 ± 11.4	97	78.1 ± 20.9	0.53	616	76.5 ± 22.1	557	74.8 ± 22.3	0.20
	3 yrs	68	80.8 ± 18.5	75	79.1 ± 18.6	0.60	483	77.8 ± 20.3	454	76.9 ± 20.8	0.52
Treatment satisfaction	Baseline	116	88.2 ± 14.9	151	84.8 ± 17.7	0.10	789	87.6 ± 15.0	700	85.9 ± 16.6	0.04
	1 month	108	91.1 ± 11.6	129	85.6 ± 17.9	0.004	707	91.6 ± 12.0	656	89.0 ± 14.3	<0.001
	3 month	110	92.6 ± 11.8	125	87.2 ± 14.3	0.002	701	92.2 ± 12.2	640	90.1 ± 13.9	0.003
	6 month	104	91.3 ± 11.8	119	87.4 ± 14.6	0.03	726	91.6 ± 12.9	622	90.5 ± 13.6	0.15
	1 yr	100	91.9 ± 12.2	121	90.1 ± 14.8	0.34	693	92.1 ± 11.7	610	89.9 ± 13.8	0.003
	2 yrs	91	93.1 ± 11.4	97	92.1 ± 12.5	0.55	615	92.2 ± 12.9	558	91.8 ± 12.7	0.53
	3 yrs	68	91.3 ± 13.8	75	88.6 ± 14.7	0.29	483	91.6 ± 12.1	455	91.8 ± 11.0	0.79
Angina frequency	Baseline	116	65.9 ± 26.8	151	68.9 ± 26.8	0.37	788	69.5 ± 26.3	712	70.0 ± 25.5	0.25
	1 month	108	80.6 ± 21.3	129	76.1 ± 25.5	0.15	709	81.7 ± 22.9	657	61.3 ± 24.1	<0.001
	3 month	110	83.2 ± 22.7	125	79.8 ± 24.3	0.27	702	85.0 ± 21.9	640	81.0 ± 23.0	0.001
	6 month	104	83.9 ± 21.5	120	83.3 ± 22.1	0.83	730	87.0 ± 19.6	622	83.5 ± 21.2	0.002
	1 yr	100	83.9 ± 21.6	120	85.7 ± 20.7	0.54	695	87.8 ± 19.1	610	84.4 ± 20.6	0.002
	2 yrs	91	89.9 ± 16.2	99	88.6 ± 18.6	0.61	617	88.9 ± 17.9	560	85.9 ± 19.4	0.007
	3 yrs	68	91.2 ± 13.2	75	89.1 ± 16.5	0.40	480	88.2 ± 19.3	451	87.7 ± 18.5	0.68
Angina stability	Baseline	114	50.7 ± 32.3	148	58.1 ± 32.0	0.58	774	54.6 ± 33.1	694	52.2 ± 31.9	0.16
	1 month	108	80.3 ± 24.4	128	69.5 ± 31.0	0.003	700	80.6 ± 26.8	649	73.2 ± 27.4	<0.001
	3 month	108	76.6 ± 27.0	124	72.6 ± 26.4	0.25	694	77.2 ± 27.9	630	73.2 ± 27.4	0.009
	6 month	103	76.5 ± 27.1	116	70.4 ± 30.0	0.12	717	75.6 ± 28.0	614	73.7 ± 28.1	0.22
	1 yr	97	69.8 ± 28.9	117	71.6 ± 29.3	0.66	679	74.0 ± 26.7	595	69.9 ± 27.9	0.008
	2 yrs	91	77.2 ± 24.1	97	70.9 ± 26.9	0.09	600	72.5 ± 27.4	551	69.5 ± 27.1	0.06
	3 yrs	67	72.0 ± 27.0	75	69.3 ± 27.4	0.56	474	71.2 ± 27.9	442	70.9 ± 28.2	0.88

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