1

Introduction

According to the American Heart Association, almost 1.03 million coronary angiographies and 955 thousand percutaneous coronary interventions (PCI) were performed in the United States in the year 2010 . In-hospital mortality currently remains at approximately 1.31%, while total complication rates are even more significant . Although the prognostic value of post-procedural enzyme elevation is still a matter of controversy, increases in troponin I (TnI) levels have been observed following 16% to 73% of procedures, depending on the clinical scenario . Older age, diabetes mellitus, heart failure, anemia, renal insufficiency, elevated baseline TnI, peripheral atherosclerosis, multivessel disease, multistenting, bifurcation lesions, calcified arteries and intraluminal thrombi have all been described as potential risk factors.

Two types of myocardial damage have been described in these circumstances. Type 1 myocardial injuries involve the myocardium adjacent to the coronary lesion being unobstructed. Conversely, type 2 injuries occur when the distal myocardium and microcirculation are damaged, mainly by plaque debris embolization, and accounts for 75% of enzyme elevations in this situation . Three meta-analyses including studies published up to the year 2009 have suggested that such cases are associated with an increase in morbidity and mortality. However, recent large scale studies have not shared this conclusion . In addition, according to the third universal definition of myocardial infarction (MI), PCI-associated events (type 4a) are only diagnosed if the troponin level rises above 5 times the 99th percentile of the assay’s upper reference limit in the first 48 h after the intervention, and is accompanied by either ischemic symptoms, evidence of ischemia in non-invasive tests or compatible coronary angiography findings. Asymptomatic >5 times enzyme elevations are diagnosed as “myocardial injury”, and are currently of uncertain clinical relevance, given that few studies have addressed the prognostic value of such a diagnosis since it was defined . As a result, the current stricter definition of type 4a MI could have a lower sensitivity for identifying high risk subgroups after PCI. The purpose of this study was to evaluate the association of any and ≥5 times post-PCI TnI levels, regardless of any other clinical criteria, with subsequent 1 year all-cause mortality and long term survival.

2

Methods

In this retrospective study, all consecutive patients submitted to PCI between January 1st 2013 and December 31st 2014 were screened in two reference hospitals in Rio de Janeiro, Brazil. Data regarding clinical, angiographic and procedural characteristics were collected by medical chart review. Only elective procedures were selected, and these were defined by the absence of MI within 2 weeks before the intervention. Patients admitted to the hospital more than 7 days before the procedure or diagnosed with sepsis or active cancer were also excluded. Coronary lesions ≥70% were considered significant to define the number of diseased vessels.

Additionally, at least 1 TnI (Abbot Laboratories, Architect STAT Troponin I) measurement between 6 and 24 h post-intervention was required for inclusion. If more than one measurement was reported, only the highest value was considered in the analysis. When available, baseline TnI levels were also collected, whereas procedures followed only by high sensitivity (HS) troponin measurements were excluded. Levels above the 99th percentile threshold were classified as elevated, although they were defined differently for men (>0.033 ng/ml) and women (>0.013 ng/ml). When the baseline value was already raised, a relative increase ≥20% in the post-PCI level was defined as relevant. The prevalence of elevations ≥5 times above the 99th percentile was also recorded. For these surrogate enzymatic endpoints, the analysis considered the total amount of patient-procedures, since a number of patients underwent more than 1 intervention during the study period. In addition to aspirin, a clopidogrel loading dose between 300 and 600 mg was routinely administered during or immediately after the intervention, even to those previously using the medication.

Mortality rates at 1 year and long term survival were evaluated by including only the most recent procedure among those with multiple interventions. Mortality was established by consulting a public regional online database of births and deaths of Rio de Janeiro State, and follow up for at least 1 year was available for all the included patients. The study conforms to the Declaration of Helsinki and approval for data collection was obtained from both hospitals’ human research committee. Informed consent was not deemed necessary since the information was acquired from retrospective chart review.

2

Methods

In this retrospective study, all consecutive patients submitted to PCI between January 1st 2013 and December 31st 2014 were screened in two reference hospitals in Rio de Janeiro, Brazil. Data regarding clinical, angiographic and procedural characteristics were collected by medical chart review. Only elective procedures were selected, and these were defined by the absence of MI within 2 weeks before the intervention. Patients admitted to the hospital more than 7 days before the procedure or diagnosed with sepsis or active cancer were also excluded. Coronary lesions ≥70% were considered significant to define the number of diseased vessels.

Additionally, at least 1 TnI (Abbot Laboratories, Architect STAT Troponin I) measurement between 6 and 24 h post-intervention was required for inclusion. If more than one measurement was reported, only the highest value was considered in the analysis. When available, baseline TnI levels were also collected, whereas procedures followed only by high sensitivity (HS) troponin measurements were excluded. Levels above the 99th percentile threshold were classified as elevated, although they were defined differently for men (>0.033 ng/ml) and women (>0.013 ng/ml). When the baseline value was already raised, a relative increase ≥20% in the post-PCI level was defined as relevant. The prevalence of elevations ≥5 times above the 99th percentile was also recorded. For these surrogate enzymatic endpoints, the analysis considered the total amount of patient-procedures, since a number of patients underwent more than 1 intervention during the study period. In addition to aspirin, a clopidogrel loading dose between 300 and 600 mg was routinely administered during or immediately after the intervention, even to those previously using the medication.

Mortality rates at 1 year and long term survival were evaluated by including only the most recent procedure among those with multiple interventions. Mortality was established by consulting a public regional online database of births and deaths of Rio de Janeiro State, and follow up for at least 1 year was available for all the included patients. The study conforms to the Declaration of Helsinki and approval for data collection was obtained from both hospitals’ human research committee. Informed consent was not deemed necessary since the information was acquired from retrospective chart review.

3

Results

From January 1st 2013 to December 31st 2014, a total of 1533 procedures from both participating hospitals were screened, of which 455 were excluded according to the predefined criteria. An additional 638 interventions (631 exclusively from one of the hospitals) were further excluded from the remaining 1078 elective procedures, as they did not have a post-intervention TnI measurement. Furthermore, 33 interventions had only post-procedural HS TnI levels and were also not considered. As a result, 407 procedures were included in the enzyme elevation analysis ( Fig. 1 ). Considering that 22 patients had 2 procedures and one patient had 3 during the study period, the interventions were performed in 383 individual patients, who were evaluated for 1 year all-cause mortality and survival on follow up.

Flow chart for the procedures included in the study. PCI, percutaneous coronary interventions .

In order to verify the possibility of selection bias for the procedures with at least 1 post-PCI TnI result, the cohort of patients without enzyme measurements was compared to that included in the study regarding clinical characteristics and 1 year mortality, which were available for all patients in both cohorts. This assessment was restricted to one of the hospitals, where 631 procedures (576 individual patients) did not contain this information and 328 (322 individual patients) had at least 1 TnI measurement. There were no significant differences in age, gender or clinical risk factors such as hypertension, diabetes and dyslipidemia between the two groups, and 1 year mortality rates were also similar ( Table 1 ).

Patients included in the study were predominantly males, with a mean age of 63.5 years (SD ±10.6) and an elevated prevalence of cardiovascular risk factors and symptomatic coronary artery disease. There was also a predominance of single vessel disease and normal left ventricular function ( Table 2 ). Troponin I elevation above the 99th percentile occurred after 74.7% of the 407 procedures. In the univariate analysis, any elevation was significantly related to age ≥ 70 years (OR 1.91 [95% CI 1.12–3.27], p = 0.018), female gender (OR 2.14 [95% CI 1.23–3.71], p = 0.007), multivessel angioplasty (OR 2.6 [95% CI 1.43–4.73], p = 0.002) and multistenting (OR 2.94 [95% CI 1.79–4.85], p < 0.001). Aspirin (OR 0.54 [95% CI 0.33–0.89], p = 0.016) use on admission was inversely associated with any level of enzyme elevation. In the multivariate model, all of the variables with statistical significance in the univariate analysis remained predictive of any TnI elevation. In addition, anti-diabetic medication usage, including insulin, had an independent protective effect regarding post-procedural TnI increase (OR 0.47 [95% CI 0.24–0.93], p = 0.031). Finally, elevations ≥5 times above the 99th percentile were recorded after 41.3% of the interventions, and were independently associated with age ≥ 70 years (OR 2.45 [95% CI 1.33–4.51], p = 0.004) and multistenting (OR 3.09 [95% CI 1.8–5.3], p < 0.001). Previous hypoglycemic medication usage was also inversely related to higher TnI elevations in the multivariate analysis (OR 0.32 [95% CI 0.16–0.65], p = 0.002).

Table 2

Clinical, angiographic and procedural characteristics according to 1 year mortality.

Patient characteristics	Total, n = 383 (%)	Death within 1 year (%)		p value
		No, n = 363	Yes, n = 20
Mean age, yrs. (SD ±)	63.5 (10.6)	63.2 (10.6)	68.8 (10.2)	0.022
Male gender	69.7	71.4	40	0.003
Hypertension	94.5	94.1	100	0.265
Diabetes	41.2	39.7	64.7	0.042
Hyperlipidemia	90.5	91.4	75	0.054
Heart Failure or LVD	10.2	8.8	35	<0.001
Prior MI or symptomatic CAD	85.3	85.2	86.7	0.878
Mean baseline HGB, mg/dl (SD ±)	13.5 (1.5)	13.5 (1.5)	12.6 (1.9)	0.022
Mean post-PCI HGB, mg/dl (SD ±)	12.4 (1.6)	12.5 (1.5)	10.7 (2.4)	<0.001
Median baseline Cr, mg/dl (IQR)	0.95 (0.82–1.15)	0.94 (0.82–1.14)	1.08 (0.87–1.25)	0.3
Median post-PCI Cr, mg/dl (IQR)	0.86 (0.75–1.01)	0.86 (0.75–1.01)	0.96 (0.85–1.77)	0.02
Pre-procedural medications a
Aspirin	52	52.6	41.2	0.361
Clopidogrel	29.6	29.3	35.3	0.598
β-blockers	65.1	64.4	76.5	0.435
ACEi or ARB	69.6	68.6	88.2	0.107
CCB	25.9	26	23.5	1.0
Statins	66.6	67.3	52.9	0.222
Antidiabetics b	23.4	23.4	23.5	1.0
Procedural aspects
Multivessel disease c	28.3	29.3	10	0.074
Multivessel PCI d	27.2	28.2	10	0.075
Multistenting e	44.4	45.2	30	0.184
Median baseline TnI, ng/ml (IQR) f	0.01 (0.001–0.02)	0.004 (0.001–0.02)	0.014 (0.01–0.07)	0.002
Median post-PCI TnI, ng/ml (IQR)	0.1 (0.03–0.44)	0.1 (0.03–0.4)	0.38 (0.09–0.64)	0.054
Any post-PCI TnI elevation	75.2	74.1	95	0.034
≥ 5 times post-PCI TnI elevation	41.8	40.5	65	0.031

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