The effects of percutaneous coronary intervention on mortality in elderly patients with non-ST-segment elevation myocardial infarction undergoing coronary angiography

Abstract

Introduction

Although it is recommended that elderly patients with non-ST-segment elevation myocardial infarction (NSTEMI) should undergo an assessment for invasive revascularization, these patients undergo fewer coronary interventions despite the current guidelines. The aim of the study is to evaluate the effectiveness of percutaneous coronary intervention on all-cause mortalities monthly and annually in the population.

Methods

Three hundred and twenty-four patients with NSTEMI aged 65 years or older who underwent coronary angiography and treated with conservative strategy or percutaneous coronary intervention were included in the study. All demographic and clinical characteristics of the patients were recorded and one-month and one-year follow-up results were analysed.

Results

Two hundred eight cases (64.19%) were treated with percutaneous coronary intervention and 116 cases (35.81%) of the participant were treated with conservative methods. The mean age of the participants was 75.41 ± 6.65 years. The treatment strategy was an independent predictor for the mortality of one-year (HR: 1.965). Furthermore, Killip class ≥2 (HR:2.392), Left Ventricular Ejection Fraction (HR:2.637) and renal failure (HR: 3.471) were independent predictors for one-year mortality.

Conclusion

The present study has revealed that percutaneous coronary intervention was effective on one-year mortality in NSTEMI patients over the age of 65. It is considered that percutaneous coronary intervention would decrease mortality in these patients but it should be addressed in larger population studies.

Keywords

Acute coronary syndrome non-ST-segment elevation myocardial infarction percutaneous coronary intervention conservative treatment elderly,mortality

Introduction

It is known that non-ST-segment elevation myocardial infarction (NSTEMI) is one of the leading causes of hospitalisation, disability and mortality in elderly patients.¹ The efficacy of coronary revascularization in the treatment has been clearly demonstrated.^2,3 Although the majority of the patients diagnosed with the disease are adults over the age of 65 and the evidence-based guidelines have recommended that elderly patients with NSTEMI should undergo an examination for invasive revascularization, the number of elderly patients undergoing invasive treatment in clinical practice is relatively low.^4–6 Conservative treatments are generally preferred by the physicians since there are greater haemorrhagic risks and higher rates of comorbidities in the elderly.^7,8 Therefore, the fact that older patients represent a higher risk subgroup and receive less optimal treatment than younger patients increased the importance of examining the effect of treatment strategies in elderly NSTEMI patients.

Various risk scores have been developed in order to help decision making in the treatment of patients with NSTEMI.^9,10 Disregarding the elderly patient population in most of the scoring systems that frequently used in clinical practices and randomised controlled trials have led to the question of at which level these scoring systems represent elderly NSTEMI patients.

The aim of the study was to examine the effect of percutaneous coronary intervention (PCI) treatment on one-month and one-year mortality in NSTEMI patients over the age of 65 and address other factors predicting mortality.

Material and methods

Study design and setting

The study was an observational, clinical and prospective research which was carried out between September 2016 and June 2019 at Sultan Abdülhamid Han Training and Research Hospital in İstanbul/Turkey. The study was first planned as a pragmatic clinical study embedded in a routine clinical practice at the hospital. The approval of the Local Ethical Committee was obtained and the study was carried out in accordance with the Declaration of Helsinki.

Population of the study

The sample of the study consisted of patients with NSTEMI aged 65 years or older who underwent coronary angiography and treated with either a conservative strategy or PCI. Patients clinically indicated for angiography within 72 h of diagnosis were included in the study according to the inclusion and exclusion criteria. Only patients who were followed up for 14 months after NSTEMI were included in the study. Patients underwent coronary angiography with NSTEMI according to the guidelines of the European Society of Cardiology and being 65 years or older were included in the study.² On the other hand cardiogenic shock, pulmonary embolism, valvular heart disease, malignancy (expectancy of life ≤1 year), primary arrhythmia were identified as the exclusion criteria of the study. Moreover, the patients receiving the decision of coronary artery bypass graft operation (CABG) and having the other causes of high troponin levels were excluded. Thus, 324 patients with NSTEMI aged 65 years and over were included in the study (Figure 1).

Figure 1.

Flow chart of the study.

Protocol and study procedures

The diagnosis of NSTEMI was based on current guidelines.² All the files of patients underwent coronary angiography and all images of coronary angiography performed using standard techniques were digitally recorded. Patients having exclusion criteria according to coronary angiography data were excluded from the study at this stage. All participants received a conservative strategy or an invasive revascularization.

Clinical evaluation

Demographic data, electrocardiography and echocardiography findings, the history of the medical disease (e.g. renal failure, diabetes, dyslipidaemia) and laboratory testing values (e.g. creatinine, troponin) were carried out according to the routine practice. Creatinine clearance (CrCl) was estimated using the Cockroft-Gault equation. The severity of coronary atherosclerotic lesions in all patients was assessed by SYNTAX¹⁰ score and Gensini¹¹ Score by means of the procedure of two professionally experienced cardiologists. The risk assessment for all patients was calculated with the Global Registry of Acute Coronary Events (GRACE) risk score.⁹ For all patients, a SYNTAX II score was calculated regarding a recommendation between CABG and PCI.¹² Killip classification was performed for the clinical status of the patients and the classification was in two groups as Killip score 1 and Killip score ≥2.¹³

The aim of the study was to examine the prognostic implication of percutaneous coronary revascularization on one-month and one-year all-cause mortality. Therefore, clinical visits were planned on the first month and the first year. Participants included in the study were followed for ≥14 months after NSTEMI. Mortality of the patients was determined upon either national records or hospital records.

Statistical analysis

The dataset of the study was analysed using SPSS version 20 (SPSS, Inc., Chicago, IL). The descriptive data were reported for continuous variables as means and standard deviations and categorical variables, frequencies and percentages. The Chi-square tests were used for analyses of categorical variables. The normal distribution of the continuous data was tested using the Kolmogorov–Smirnov test. Student’s t test was used when continuous variables were found suitable for normal distribution. Kaplan–Meier plots were used for the comparison of survival rate between different subsets of patients, i.e. conservative strategy and PCI. Two-way interactions between the treatment strategy and the other independent variables were tested in order to validate the results of the regression model. The association of treatment strategy with one-month and one-year all-cause mortality was examined by univariable and multivariable Cox regression models and models adjusted for the relevant potential co-founders. The characteristics and clinical parameters of the patients were considered prognostically significant based on the relevant literature. In addition, covariates identiﬁed in the univariable analyses as being associated with follow-up events were reflected in the models. Variables for the inclusion were carefully selected in order to ensure parsimony of the ﬁnal models. Only covariates available were considered as potential predictors. After the analysis was performed using a graphical check, the proportional hazards of the survival probability curves were veriﬁed. The ﬁnal model was adjusted for the participants enrolled in the study. Three landmark analyses starting at the 1st and 12th months after the admission were performed and reported separately in order to assess the prognostic value of treatment strategy carefully depending on the time as of NSTEMI. p values ≤0.05 were considered statistically significant.

Results

Baseline and clinical characteristics

The study included 324 patients with NSTEMI who underwent coronary angiography; 208 cases (64.19%) were evaluated as PCI, whereas 116 cases (35.81%) evaluated as the conservative strategy among the total population. Demographic and baseline characteristics of the participants according to treatment strategy are described in Table 1. The mean age of the study population was 75.41 ± 6.65 years and the participants were predominantly male (57.1%, n = 185). There was a statistically significant difference between the conservative strategy and PCI group with respect to age, gender, using Warfarin at admission, history of coronary artery disease, stroke and PCI (p values were found as 0.009, 0.031, 0.019, 0.006, 0.003 and <0.001, respectively).

Table 1.

Demographic and baseline characteristics of the study population stratified according to conservative strategy and percutaneous coronary intervention.

Variable	Overall (n = 324)	Conservative strategy (n = 116)	Percutaneous coronary intervention (n = 208)	t/χ² value	p value
Age, years (mean ± SD)	75.41 ± 6.65	76.69 ± 7.10	74.70 ± 6.29	2.613	0.009
Males, n (%)	185 (57.1)	57 (30.8)	128 (69.2)	4.675	0.031
History, n (%)
Diabetes mellitus	92 (28.4)	34 (29.3)	58 (27.9)	0.074	0.785
Dyslipidemia	116 (35.8)	35 (30.2)	81 (38.9)	2.492	0.114
Hypertension	214 (66.0)	71 (61.2)	143 (68.8)	1.890	0.169
Coronary artery disease	133 (41.0)	36 (31.0)	97 (46.6)	7.486	0.006
Peripheral artery disease	16 (4.9)	4 (3.4)	12 (5.8)	0.855	0.355
Chronic renal failure	85 (26.2)	33 (28.4)	52 (25.0)	0.458	0.499
COPD	33 (10.2)	15 (12.9)	18 (8.7)	1.489	0.222
Stroke	10 (3.1)	8 (6.9)	2 (1.0)	8.770	0.003
PCI	54 (16.7)	8 (6.9)	46 (22.1)	12.419	<0.001
Current smoking, n (%)	53 (16.4)	23 (19.8)	20 (14.4)	1.590	0.207
Admission medication n (%)
ASA	106 (46.9)	28 (38.4)	78 (51.0)	3.163	0.075
Clopidogrel	50 (22.1)	12 (16.4)	38 (24.8)	2.023	0.155
Warfarin	22 (9.7)	12 (16.4)	10 (6.5)	5.515	0.019
NOACs	18 (8.0)	8 (11.0)	10 (6.5)	1.319	0.251
RAS blockers	115 (50.9)	43 (58.9)	72 (47.1)	2.775	0.096
Beta-blockers	123 (54.4)	45 (61.6)	78 (51.0)	2.266	0.132
Ca Channel blockers	74 (32.7)	24 (32.9)	50 (32.7)	0.001	0.976

ASA: acetyl salicylic acid, COPD: chronic obstructive pulmonary disease; NOACs: novel oral anticoagulants, PCI: Percutaneous coronary intervention, RAS Blockers: renin-angiotensin system blockers. Bold values indicate statistical significance.

Clinical evaluations and mortality status of the participants according to the treatment strategy are described in Table 2. A statistically significant difference was found between these two groups: haemoglobin, using ASA, clopidogrel, warfarin, statin at discharge, SYNTAX II-PCI, SYNTAX II-CABG, GRACE and Gensini scores (p values were found as 0.043, <0.001, 0.024, <0.001, <0.001, 0.023, 0.008, <0.001 and 0.004 respectively).

Table 2.

Clinical characteristics and mortality of the study population stratified according to conservative strategy and percutaneous coronary intervention.

Variable	Overall (n = 324)	Conservative strategy (n = 116)	Percutaneous coronary intervention (n = 208)	t/χ² value	p value
Admission HR (beat/min.)	83.91 ± 19.50	86.27 ± 20.04	82.59 ± 19.11	1.632	0.104
Admission systole BP (mm/Hg)	132.57 ± 20.64	132.32 ± 22.63	132.71 ± 19.30	−0.154	0.878
Admission diastole BP (mm/Hg)	77.58 ± 11.73	77.66 ± 12.97	77.54 ± 11.00	00.084	0.933
Hemoglobin (mg/dl)	13.09 ± 2.04	12.76 ± 2.25	13.27 ± 1.89	−2.036	0.043
ST segment deviation (yes)	89 (27.5)	36 (31.0)	53 (25.5)	1.153	0.283
Discharge medications n (%)
ASA	279 (86.1)	85 (73.3)	194 (93.3)	24.890	<0.001
Clopidogrel	269 (83.0)	70 (60.3)	199 (95.7)	65.947	<0.001
Warfarin	36 (11.1)	19 (16.4)	17 (8.2)	5.078	0.024
NOACs	24 (12.4)	12 (16.4)	16 (10.5)	1.629	0.202
RAS blockers	217 (67.0)	74 (63.8)	143 (68.8)	0.827	0.363
Beta-blockers	285 (88.0)	101 (87.1)	184 (88.5)	0.136	0.712
Statin	226 (69.8)	66 (56.9)	160 (76.9)	14.156	<0.001
Killip class ≥2, n (%)	68 (21.0)	32 (27.6)	36 (17.3)	4.744	0.029
SYNTAX I, (mean ± SD)	9.79 ± 8.17	8.86 ± 10.11	10.35 ± 6.74	−1.345	0.180
SYNTAX II – PCI, (mean ± SD)	37.31 ± 10.09	39.08 ± 10.75	36.26 ± 9.56	2.293	0.023
SYNTAX II – CABG, (mean ± SD)	35.38 ± 9.04	37.33 ± 10.04	34.22 ± 8.20	2.689	0.008
GRACE score, (mean ± SD)	135.00 ± 22.03	143.46 ± 25.46	130.96 ± 18.71	3.689	<0.001
Gensini score, (mean ± SD)	25.32 ± 18.80	18.55 ± 25.46	28.78 ± 13.06	−2.993	0.004
Left Ventricular Ejection Fraction (%), (mean ± SD)	50.65 ± 9.56	49.32 ± 9.95	51.39 ± 9.27	−1.873	0.062
Creatinine clearance, (mean ± SD)	59.10 ± 19.81	57.55 ± 19.20	59.96 ± 10.14	−1.050	0.295
Admission troponin, (mean ± SD)	2.32 ± 5.74	1.79 ± 3.81	2.61 ± 6.56	−1.376	0.170
One-month mortality, n (%)	12 (3.7)	6 (5.2)	6 (2.9)	1.093	0.296
One-year mortality, n (%)	42 (13.0)	22 (19.0)	20 (9.6)	5.770	0.016

ASA: acetyl salicylic acid, BP: Blood pressure; COPD: chronic obstructive pulmonary disease; HR: heart rate, NOACs: novel oral anticoagulants, RAS Blockers: renin-angiotensin system blockers. Bold values indicate statistical significance.

The ROC curve was performed based on the primary endpoint in order to find the clinical cut-off of the impact of left ventricular ejection fraction (LVEF) on mortality. Predictive value of 42% was found to describe one-month mortality (cutoff = 42, sensitivity 82.4%, specificity 76.7% and AUC 0.841).

Survival curves according to the treatment strategy for the patients are shown in Figure 2. The time-to-event analysis revealed signiﬁcant differences for the main endpoint including all-cause mortality for the treatment strategy at one-year (invasive vs. conservative: hazard ratio = 2.085, 95% CI: 1.031 to 4.220, p = 0.041; Figure 2).

Figure 2.

Cumulative risk of overall death in patients stratified according to conservative strategy and percutaneous coronary intervention.

One-month all-cause mortality

There was no statistically significant difference between the conservative strategy and PCI group for one-month mortality (p = 0.296) (Table 2). Univariate and multivariate analysis for identifying the determinants of one-month all-cause mortality is presented in Table 3. Univariable Cox regression analysis showed that Killip class ≥2, LVEF and renal failure were associated with one-month mortality.

Table 3.

Predictors of one-month; one-year mortality: Univariable and multivariable Cox regression analysis.

Predictor	Hazard ratio (95% CI)	p value
Univariable analysis for 1-month mortality
Treatment (conservative strategy)	1.809 (0.584–5.610)	0.304
Admission troponin (1-point increase)	0.938 (0.775–1.136)	0.511
Killip class ≥2	3.897 (1.257–12.085)	0.018
Left Ventricular Ejection Fraction (%) <42	8.874 (2.671–29.478)	<0.001
Renal failure	33.039 (4.265–255.937)	0.001
Univariable analysis for 1-year mortality
Treatment (conservative strategy)	2.094 (1.143–3.837)	0.017
Admission troponin (1-point increase)	1.035 (1.000–1.071)	0.049
Killip class ≥2	3.440 (1.873–6.318)	<0.001
Left Ventricular Ejection Fraction (%) <42	4.044 (2.202–7.429)	<0.001
Renal failure	4.051 (2.206–7.442)	<0.001
Multivariable analysis for 1-year mortality
Treatment (conservative strategy)	1.965 (1.037–3.720)	0.038
Admission troponin (1-point increase)	1.033 (0.996–1.073)	0.083
Killip class ≥2	2.392 (1.268–4.511)	0.007
Left Ventricular Ejection Fraction (%) <42	2.637 (1.373–5.065)	0.004
Renal failure	3.471 (1.853–6.502)	<0.001

Bold values indicate statistical significance.

One-year all-cause mortality

There was a statistically significant difference between the conservative strategy and the PCI group for one-year mortality (p = 0.016) (Table 2). Univariate and multivariate analysis for identifying determinants of one-year all-cause mortality is presented in Table 3. Univariable Cox regression analysis showed that the treatment strategy, Killip class ≥2, LVEF and renal failure were associated with one-year mortality. The independent predictors of one-year mortality revealed the treatment strategy, Killip class ≥2, LVEF and renal failure with an adjusted hazard ratio of 1.965 (95% CI:1.037 to 3.720), 2.392 (95% CI:1.268 to 4.511), 2.637 (95% CI:1.373 to 5.065) and 3.471 (95% CI:1.853 to 6.502), respectively.

Discussion

The effects of PCI and the conservative treatment strategies on mortality rate in NSTEMI patients over the age of 65 were compared in this study. The most important result of the study was that PCI was not found to be effective on one-month mortality in NSTEMI patients over 65 years of age, whereas it reduced all-cause mortality for one-year. In addition, it was noted that renal failure, LVEF and Killip class had an effect on mortality. We believe that the results play a key role in terms of assisting clinicians for the determination of the treatment strategies in the elderly population.

It has been recommended in the guidelines in clinical practices that elderly NSTEMI patients should be treated with similar strategies compared to the younger patient population. However, it has also been recommended that their comorbidity and fragility should be considered and the treatment to be individualised.^2,14 On the other hand, since the elderly population is excluded from most of the randomised trials, uncertainties could still be found regarding the treatment approach for elderly NSTEMI patients. Therefore, clinicians accept the advanced age as an obstacle for an invasive treatment.¹⁵

It is shown that invasive treatment may be beneficial and safe in elderly patients today. A recent study including patients over the age of 75 reported that early invasive treatment reduced in-hospital mortality in patients with Acute Coronary Syndrome (ACS).¹⁶ In a meta-analysis involving FRISC II, RITA-3 and ICTUS studies, it was revealed that routine invasive strategy reduced the likelihood of cardiovascular mortality and myocardial infarction within five years.¹⁷ In another study where conservative and invasive treatment results in elderly NSTEMI patients were presented, it was observed that invasive treatment was associated with lower incidence of six-month mortality.¹⁸ The results of this study revealed that the invasive treatment strategy had a positive effect on mortality for one year as in previous studies.

There are two recent randomised clinical trials focusing on ACS treatment strategy in elderly patients. A recent study for one-year follow-up of 75-year-old NSTEMI patients showed that invasive treatment did not have any effect on the mortality rate. However, nearly half of the patients were found to have normal cardiac enzymes and PCI was found to be beneficial in patients with high troponin levels in this study when examined the subgroup analysis.¹⁹ Similarly, in a study of ACS patients over 80 years of age, the invasive strategy has been shown to be superior to the conservative approach. However, when exclusion criteria are examined, it is seen that a healthier population is represented in this study.²⁰ Accordingly, we pay attention to the results of our study in terms of reflecting the actual patient population including patient groups with high risk criteria such as renal failure and high troponin levels.

Another result of our study was that renal failure, LVEF and Killip class had an effect on mortality rate being in consistency with the relevant literature.^9,16,21,22

Limitations

First of all, the present study was not fully covering the majority of elderly population because the number of patients was insufficient and the follow-up time was short. Failure to record patients’ data that may affect mortality such as contrast nephropathy and intervention site complications should also be considered as factors that may change the results. Likewise, it should be noted that there may be differences in the management of borderline patients according to clinician preferences. Moreover, another limitation was that the causes of death have not been determined precisely.

Conclusion

In conclusion, ischemic heart disease is one of the leading causes of death in the world. WHO has noted that deaths due to coronary heart diseases will increase by 120–137% over the next 20 years with an increasing elderly population.²³ Therefore, it is important to determine a strategy on how to treat coronary artery disease in elderly patients. Considering the results of our study, we believe that the use of invasive management in elderly patients with NSTEMI will reduce the mortality rate. Therefore, it is highlighted that studies randomising more patients having comorbidities and a long median follow-up will shed light on the management of elderly patients with ACS.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Pınar Demir Gündoğmuş

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