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Nonobstructive coronary atherosclerosis is associated with adverse prognosis among patients diagnosed with myocardial infarction without obstructive coronary arteries
Corresponding author. Department of Cardiology, Heart Institute, Soroka University Medical Center Department of Public Health, Faculty of Health Sciences, Ben Gurion University of the Negev, PO Box 151, Beersheba, 84101, Israel.
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelClinical Research Center, Soroka University Medical Center, Beersheba, Israel
Department of Cardiology, Soroka University Medical Center, Beersheba, IsraelClinical Research Center, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheba, IsraelDepartment of Cardiology, Soroka University Medical Center, Beersheba, Israel
Myocardial infarction with no obstructive coronary arteries (MINOCA) carries a considerable long-term risk for death and recurrent acute coronary syndrome (re-ACS).
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In MINOCA, the presence of nonobstructive CAD carries higher risk for death or re-ACS.
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Reduced LVEF and older age are associated with increased risk for death and re-ACS.
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Sinus rhythm and female sex are associated with lower risk for death and re-ACS.
Abstract
Background and aims
The prognostic impact of nonobstructive coronary artery disease (CAD), as opposed to normal coronary arteries, on long-term outcomes of patients with myocardial infarction with no obstructive coronary arteries (MINOCA) is unclear. We aimed to address the association between nonobstructive-CAD and major adverse events (MAE) following MINOCA.
Methods
We conducted a retrospective cohort study of consecutive MINOCA patients admitted to a large referral medical center between 2005 and 2018. Patients were classified according to coronary angiography as having either normal-coronaries or nonobstructive-CAD. The primary outcome was MAE, defined as the composite of all-cause mortality and recurrent acute coronary syndrome (ACS).
Results
Of the 1544 MINOCA patients, 651 (42%) had normal coronaries, and 893 (58%) had CAD. The mean age was 61.2 ± 12.6 years, and 710 (46%) were females. Nonobstructive-CAD patients were older and less likely to be females, with higher rates of diabetes, hypertension, dyslipidemia, atrial fibrillation, and chronic renal-failure (p < 0.05). At a median follow-up of 7 years, MAE occurred in 203 (23%) patients and 67 (10%) patients in the nonobstructive-CAD and normal-coronaries groups, respectively (p < 0.01). In multivariable models, nonobstructive -CAD was significantly associated with long-term MAE [adjusted-hazard-ratio (aHR):1.67, 95% confidence-interval (95%CI):1.25–2.23; p < 0.001]. Other factors associated with a higher MAE-risk were older-age (aHR:1.05,95%CI:1.03–1.06; p < 0.001) and left ventricular ejection-fraction<40% (aHR:3.04,95%CI:2.03–4.57; p < 0.001), while female-sex (aHR:0.72, 95%CI: 0.56–0.94; p=0.014) and sinus rhythm at presentation (aHR:0.66, 95%CI: 0.44–0.98; p=0.041) were associated with lower MAE-risk.
Conclusions
In MINOCA, nonobstructive-CAD is independently associated with a higher MAE-risk than normal-coronaries. This finding may promote risk-stratification of patients with nonobstructive-CAD-MINOCA who require tighter medical follow-up and treatment optimization.
Contemporary diagnosis and management of patients with myocardial infarction in the absence of obstructive coronary artery disease: a scientific statement from the American heart association.
Characterization and outcomes of women and men with non-ST-segment elevation myocardial infarction and nonobstructive coronary artery disease: results from the can rapid risk stratification of unstable angina patients suppress adverse outcomes with early.
]. MINOCA may occur in the presence of normal coronary arteries or nonobstructive coronary artery disease.
MINOCA may be caused by multiple pathologies, including microvascular disease, epicardial coronary artery spasm, Takotsubo cardiomyopathy, and coronary dissection. Thus, different etiologies of MINOCA require substantially different and sometimes opposite treatment strategies. Consequently, there is great importance in diagnosing the underlying pathology of MINOCA [
An EAPCI expert consensus document on ischaemia with nonobstructive coronary arteries in collaboration with European society of Cardiology working group on coronary pathophysiology & microcirculation endorsed by coronary vasomotor disorders international.
]. To achieve maximal diagnostic potential, the recommended workup of MINOCA has recently expanded to include intracoronary imaging and functional testing, along with cardiac magnetic resonance (CMR) [
Although MINOCA is associated with a better prognosis than MI with obstructive coronary artery disease (CAD), this condition is far from benign. MINOCA is associated with an in-hospital mortality rate of ∼1% and a 12-month mortality rate of ∼5%, along with a significant risk of recurrence [
]. Recent works with follow-up lengths of 2–4.5 years suggested that adverse prognostic factors among MINOCA patients were similar to those of patients with obstructive CAD, such as older age, increased creatinine, diabetes, and reduced left ventricular ejection fraction (LVEF) [
Presentation, clinical profile, and prognosis of young patients with myocardial infarction with nonobstructive coronary arteries (MINOCA): results from the VIRGO study.
]. However, the prognostic consequences of nonobstructive-CAD, indicating subclinical coronary atherosclerosis, as opposed to normal coronary arteries among MINOCA patients, remain debatable and poorly explored.
2. Patients and methods
2.1 Study settings and population
This is a retrospective, population-based cohort study among all comers admitted to Soroka University Medical Center (SUMC), a 1000-bed single referral center in Southern Israel, between January 1st, 2005, and December 31st, 2018. SUMC represents a unique case of a single and only referral center in Israel's Southern region. Thus, the great majority of readmissions are at that center [
]. For this analysis, based on a cohort of all coronary angiographies performed in SUMC, we included patients aged ≥18 years who were diagnosed with MINOCA. The definition of MINOCA was based on the combination of acute myocardial infarction according to the Universal Definition of Myocardial Infarction and normal or nonobstructive (<50% stenosis) coronary artery disease on coronary angiography [
]. Cases in which any coronary arteries had more than 50% stenosis were defined as obstructive CAD. We focused on MINOCA patients with unknown underlying etiology per standard workup. Hence, patients with specific plausible diagnoses for MINOCA, such as Takotsubo syndrome, myocarditis, and spontaneous coronary dissection, were excluded. The study was approved by the SUMC institutional review board.
2.2 Data sources
Baseline and demographic information and clinical data were obtained from the hospital's electronic medical records (EMR) system and the patient's health maintenance organization (HMO) using the ninth international classification of diseases (ICD-9). Baseline variables extracted from the EMR were sex, age, body mass index, LVEF, heart rhythm at presentation, ST-elevation MI at presentation, hospitalization duration, and laboratory measures. The HMO-based background variables were socioeconomic state score, smoking, dyslipidemia, hypertension, diabetes mellitus, obesity, atrial fibrillation, and chronic renal failure. Serum troponin-T was expressed as times the upper limit of the normal as defined by the medical center's core laboratory, based on the kit manufacturer (RocheTM) recommendations.
2.3 Study groups
According to their coronary angiography, patients were divided into two groups: normal coronaries and nonobstructive-CAD. The differentiation between normal coronaries and nonobstructive-CAD was validated by cross-matching the primary diagnosis of the coronary angiography report with the detailed angiographic description of each coronary artery as summarized in the report's body.
2.4 Outcomes
The primary outcome was MAE, defined as the composite of recurrent ACS and all-cause death. Secondary outcomes were the individual components of the primary outcome, acute kidney injury, and major bleeding during the sentinel hospitalization.
Outcome data were derived from the EMR and HMO registrations and included all-cause death, recurrent acute coronary syndrome, acute kidney injury, and major bleeding. Acute kidney injury was defined as an increase in serum creatinine by over 50% from a previous value or the need for dialysis, and major bleeding was defined according to the bleeding academic research consortium (BARC) guidelines [
Validation of the bleeding academic research consortium definition of bleeding in patients with coronary artery disease undergoing percutaneous coronary intervention.
Baseline characteristics are presented across study groups. Categorical variables are presented as percentages, and continuous variables are presented as means and standard deviations or medians and interquartile ranges, according to the variable's distribution. All continuous variables were tested for normal distribution using the Shapiro-Wilk test. Categorical variables were compared using the Chi-square test or Fisher's exact test when needed. Continuous variables were compared using an independent T-test for normally distributed variables or Mann-Whitney for non-normally distributed variables. Prior to using T-tests, the equality of variance between groups was assessed by Levene's test. Thirty-day mortality was compared using univariable and multivariable logistic regressions, adjusting for potential confounders. Long-term survival was assessed by Kaplan-Meier estimates using the Log-rank test for significance. Cox proportional hazards regression analyses were performed to evaluate variables associated with long-term mortality, controlling for potential confounders. Before applying Cox regression, variables were tested for proportionality hazards assumption using Schoenfeld residuals. Variables were included in the multivariable models based on clinical importance or statistical significance with entry criteria of p < 0.1 in univariable analysis. Survival data are presented as hazard ratios (aHR) and adjusted hazard ratios (aHR), for univariable or multivariable models, respectively, with 95% confidence intervals (CI). For all analyses, a two-sided p < 0.05 was considered statistically significant. Statistical analyses were performed using IBM's SPSS software version 26.0 (Armonk, NY, USA) and R Core Team (2020) R: A Language and Environment for Statistical Computing version 4.0 (Vienna, Austria).
3. Results
The study flowchart is depicted in Fig. 1. Of 36,462 patients in the entire cohort, 16,651 (45.6%) had MI. Of these patients, 1544 patients (9.3%) had MINOCA, met the inclusion criteria, and were included in the final analysis. Baseline characteristics of the study population are presented across angiographic coronary diagnosis groups in Table 1. The mean age was 61 ± 13 years, and 46% were females. The normal coronaries group was younger and included more women compared with the nonobstructive-CAD group (58.3 ± 13.0 vs. 63.4 ± 11.9 and 53.8% vs. 40.3%, respectively; p < 0.001 for both comparisons). Compared with the nonobstructive-CAD group, the normal coronaries group had lower rates of dyslipidemia (21.8% vs. 40.4%), hypertension (13.5% vs. 26.8%), and diabetes mellitus (9.1% vs. 19.3%; p < 0.001 for all). In addition, patients with normal coronaries had lower rates of chronic renal failure and atrial fibrillation (p < 0.001 for both). Despite similar increases in serum troponin of around 2.75 (1.1–6.0) times the upper limit of normal, the normal coronaries had lower rates of left ventricular ejection fraction <40% (4.4% vs. 1.5%, p=0.003).
Study outcomes with comparisons between the study groups are detailed in Table 2. Thirty-day MAE occurred in 16 patients (1.8%) in the nonobstructive-CAD group and 6 patients (0.9%) in the normal coronaries group (adjusted-OR 1.07, 95%CI 0.36–3.22, p=0.900). Death occurred in 14 patients (1.6%) in the nonobstructive-CAD group and four patients (0.6%) in the normal coronaries group (p=0.138). Age, hypertension, and lower hemoglobin were associated with increased 30-day MAE, while sinus rhythm at presentation was associated with reduced 30-day MAE (p < 0.05 for all). However, none of these factors remained significantly associated with MAE on multivariable analysis. Acute kidney injury and major bleeding rates were relatively low (1.4% and 0.6%, respectively) and did not differ between study groups (p > 0.1 for both comparisons).
At long-term follow-up with a median of 7 years, 270 patients (17.5%) had MAE. Compared with normal coronaries, the nonobstructive-CAD group had significantly higher rates of MAE [203 (22.7%) vs. 67 (10.3%), p < 0.001]. Survival from MAE across the study groups is showed in Fig. 2. The difference in MAE between the two study groups was driven by both recurrent ACS [73 events (8.2%) in the nonobstructive-CAD group vs. 11 events (1.7%) in the normal coronaries group, p < 0.001] and all-cause death [141 events (15.8%) in the nonobstructive-CAD group vs. 61 events (9.4%) in the normal coronaries group, p < 0.001]. MAE difference between the two study groups was evident as early as one year after the index event.
In the long term, nonobstructive-CAD was significantly associated with increased MAE risk (HR 2.36, 95%CI 1.79–3.12, p < 0.001). nonobstructive-CAD remained significantly associated with long-term MAE with aHR 1.67 (95%CI 1.25–2.23, p < 0.001) in the fully adjusted multivariable model. The association between nonobstructive-CAD and long-term MAE remained significant also after controlling for treatment with aspirin, P2Y12 adenosine receptor antagonists, angiotensin-converting-enzyme inhibitors, and beta-blockers (that were used similarly across study groups). Other factors significantly associated with long-term MAE were older age (aHR/year 1.05, 95%CI 1.03–1.06, p < 0.001), female sex (aHR 0.72, 95%CI 0.56–0.94, p=0.014), sinus rhythm at presentation (aHR 0.66, 95%CI 0.44–0.98, p=0.041) and LVEF<40% (aHR 3.04, 95%CI 2.03–4.57, p < 0.001). The associations of nonobstructive-CAD with long-term MAE across stepwise incrementally adjusted multivariable models are detailed in Fig. 3.
Fig. 3Association between nonobstructive-CAD and MAE; incrementally adjusted multivariable models.
Model 1: Adjusted for age and sex Model 2: Model 1+dyslipidemia, hypertension, diabetes mellitus, and sinus rhythm at presentation Model 3: Model 2+left ventricular ejection fraction <40%.
In this study, based on long-term follow-up of 1544 consecutive patients with MINOCA, we found that nonobstructive-CAD presence in MINOCA poses a significant and independent risk factor for long-term MAE. Other factors associated with increased risk for MAE were older-age and LVEF <40%, while female sex and sinus rhythm at presentation were associated with lower MAE risk. To our knowledge, this report is the most comprehensive, with the most extended follow-up to date regarding the long-term clinical consequences of nonobstructive-CAD among patients with MINOCA.
MINOCA is a working diagnosis encompassing multiple causes of MI in the absence of significant narrowing of 50% or more in the coronary tree according to angiography and the absence of other overt causes [
]. This definition engulfs various pathophysiologic processes, including coronary pathologies such as coronary spasm, coronary embolism, spontaneous coronary dissection, plaque disruption, microvascular dysfunction, and non-coronary or myocardial causes such as supply-demand mismatch, myocarditis, and Takotsubo cardiomyopathy [
An EAPCI expert consensus document on ischaemia with nonobstructive coronary arteries in collaboration with European society of Cardiology working group on coronary pathophysiology & microcirculation endorsed by coronary vasomotor disorders international.
]. Recent studies highlighted the potential importance of intracoronary imaging and cardiac magnetic resonance to improve diagnostic accuracy among patients with MINOCA. A recent consensus statement of the European Society of Cardiology also advocates using advanced imaging tools as a part of the workup of MINOCA [
]. Nevertheless, advanced imaging technologies may not be readily available in all centers and require expertise and financial resources. Thus, these tools are still underutilized.
In a real-world setting, MINOCA diagnosis is used in cases where the underlying cause of MI remains unknown and requires further workup. Thus, we excluded cases in which alternative etiological diagnoses such as Takotsubo, spontaneous coronary dissections, and myocarditis were made. Therefore, the current study population represents a real-world setting where the underlying cause of MINOCA is unknown and requires further workup to elucidate it and tailor appropriate treatment. Our results indicate that approximately 4% of all MI patients meet the definition of MINOCA of unknown etiology. Our study's incidence of MINOCA and patient characteristics and outcomes aligns with previous reports [
]. While several reports addressed the overall prognostic markers in the setting of MINOCA, the current study aims to shed light on the prognostic relevance of coronary angiography findings among MINOCA patients, which is less studied and still debatable. This is also especially important to improve the risk-stratification of MINOCA patients and selectively allocate resources and conduct a thorough workup in high-risk patients, improving their outcomes.
Several previous reports have explored the prognostic implications of nonobstructive-CAD among stable patients who underwent elective coronary angiography or coronary computed tomography angiograms [
Prognostic value of nonobstructive and obstructive coronary artery disease detected by coronary computed tomography angiography to identify cardiovascular events.
The prognosis of patients with nonobstructive coronary artery disease versus normal arteries determined by invasive coronary angiography or computed tomography coronary angiography: a systematic review.
]. Notably, a recent computed tomography study reported that the existence and extent of nonobstructive-CAD are associated with worse long-term outcomes, either with or without obstructive coronary artery disease [
]. On the other hand, another study has shown that normal coronaries and nonobstructive-CAD carry similar clinical courses, and their long-term outcome is similar [
]. A meta-analysis of 54 studies on patients undergoing angina workup also showed a higher risk of all-cause death and MI in studies including nonobstructive-CAD patients than with patients with normal coronaries [
Clinical characteristics, sex differences, and outcomes in patients with normal or near-normal coronary arteries, nonobstructive or obstructive coronary artery disease.
]. To date, the prognostic implications of nonobstructive-CAD in the setting of MINOCA remain unclear and sparsely investigated. Furthermore, there is an immense need to identify risk factors associated with a worse long-term prognosis in MINOCA patients since these may aid in identifying patients who require tighter follow-up and intensive medical workup.
According to our study, the existence of nonobstructive-CAD in patients with MINOCA carries a significantly higher risk for long-term MAE, mainly driven by increased risk for all-cause death, independent of potential confounders. This finding may contribute to the risk stratification of patients with MINOCA and suggests that the subset of patients presenting with MINOCA and nonobstructive-CAD should be considered for intensive and thorough workup. The role of advanced imaging modalities in improving diagnosis among MINOCA patients is well substantiated. However, such a workup is cumbersome, requires many resources, and is costly. Thus, factors that may point to patients who will benefit from such workup are valuable. The results of our study may correspond with the results of a previous report where magnetic resonance imaging had low diagnostic yield in patients with MINOCA and normal coronaries, suggesting that patients with normal coronaries may have less diagnostic benefit from advanced imaging workup [
Determinants of long-term clinical outcomes in patients with angina but without obstructive coronary artery disease: a systematic review and meta-analysis.
]. Conversely, other studies among patients with nonobstructive-CAD have shown consistent findings on the high diagnostic yield of MRI in the workup of MINOCA, suggesting that this patient population may benefit from advanced imaging investigations [
Myocardial infarction with normal coronary arteries is common and associated with normal findings on cardiovascular magnetic resonance imaging: results from the Stockholm Myocardial Infarction with Normal Coronaries study.
Coronary optical coherence tomography and cardiac magnetic resonance imaging to determine underlying causes of myocardial infarction with nonobstructive coronary arteries in women.
]. Also, the diagnosis of nonobstructive-CAD in the setting of MINOCA should encourage, as in all cases of proven cardiovascular atherosclerotic disease, close medical follow-up, and optimization of secondary prevention. This is reinforced by the notion that 50% of the patients with recurrent ACS following MINOCA are prone to develop obstructive CAD [
The results of our study regarding potential prognostic markers among MINOCA patients are in line with findings from previous reports with shorter follow-up periods. Thus, our study reinforces the detrimental prognostic consequences of older age and LVEF <40% among MINOCA patients and the lower MAE-risk that characterizes females and patients with sinus rhythm at presentation. Our study's main strength and contribution is the extended reported follow-up period, the longest so far, which provides information on factors that carry long-term risk.
Some limitations of our study should be considered. First, this is a retrospective analysis that relies on data recorded by the attending physicians. A core laboratory did not validate these reports; therefore, some errors in the coronary angiography diagnosis and classifications are possible. Nevertheless, we performed cross-validation of the coronary diagnosis and compared the EMR-based diagnosis with the detailed coronary angiography report; thus, if misclassification of patients exists, its proportion should be negligible. The low 30-day recurrent ACS and mortality event rates observed in our study, which were similar across study groups, also support the assumption that if diagnostic misclassifications were made, they were small in numbers and similar between the study groups. Second, the low rate of MINOCA-related workups, such as CMR or functional tests to elucidate the underlying condition, bundles the entire MINOCA patient population into a single stack, which may include various conditions leading to MINOCA. However, this reflects the current real-world practice characterized by low rates of intracoronary or non-invasive imaging workup and highlights the need to increase the implementation of such tools in routine clinical practice [
]. Third, confounders that were not recorded and thus not included in the analyses might impact prognosis, a potential bias relevant to all historical population-based studies. Nevertheless, we captured all traditional risk factors and conventional prognostic markers and conducted a rigorous multivariable analysis accounting for potential confounders and clinically relevant variables. It is essential, however, to address the findings of this study in the context of possible residual-confounding, and further confirmatory studies to complement and support our findings on the prognostic importance of nonobstructive-CAD in patients with MINOCA are warranted. Fourth, our study is comprised of patient data collected over a considerable period and, thus, is prone to the effects of temporal trends in medicinal and pharmaceutical developments. Despite the inclusive models performed with adjustment to multiple possible confounders, studies involving a more contemporary patient population may add further information on the prognostic importance of nonobstructive-CAD in MINOCA. Fifth, medical diagnoses on which this study was based were derived from EMRs based on ICD-9 codes, thus in cases of nonspecific diagnoses, such as dyslipidemia that can be accounted for hypertriglyceridemia or hypercholesterolemia, we could not be sure of the specific, accurate diagnosis. This is a known limitation of most, if not all, historical registry-based studies; however, dyslipidemia is a complex diagnosis with many definitions that are patient- and era-sensitive and most commonly related to hypercholesterolemia. Also, we did not account for long-term compliance with medical therapy, which may attenuate the association of nonobstructive-CAD with long-term MAE due to possible improved secondary prevention.
In conclusion, nonobstructive-CAD, a marker of subclinical coronary atherosclerosis, is associated with higher long-term MAE-risk among MINOCA patients. The prognosis of MINOCA is far from benign, and factors such as older age, LVEF< 40%, male sex, and non-sinus rhythm are associated with worse long-term outcomes, mainly driven by increased all-cause death rates. Future investigations should focus on intervention measures to reduce the risk of future cardiovascular events among patients with MINOCA.
CRediT authorship contribution statement
Gal Tsaban: Conceptualization, Investigation, Methodology, Project administration, results interpretation, Writing – original draft, report drafting. Orit Barrett: Conceptualization, critical review of the report. Ido Peles: Data curation, Formal analysis, Methodology. Yigal Abramowitz: Conceptualization, critical review of the report. Hezzy Shmueli: Conceptualization, critical review of the report. Hilmi Alnsasra: Conceptualization, critical review of the report. Carlos Cafri: Conceptualization, critical review of the report. Doron Zahger: Conceptualization, critical review of the report. Edward Koifman: Conceptualization, study design, Supervision, Resources, Project administration, results interpretation, Writing – original draft, report drafting.
Declaration of competing interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Long-term survival and causes of death in patients with ST-elevation acute coronary syndrome without obstructive coronary artery disease.
Contemporary diagnosis and management of patients with myocardial infarction in the absence of obstructive coronary artery disease: a scientific statement from the American heart association.
Characterization and outcomes of women and men with non-ST-segment elevation myocardial infarction and nonobstructive coronary artery disease: results from the can rapid risk stratification of unstable angina patients suppress adverse outcomes with early.
An EAPCI expert consensus document on ischaemia with nonobstructive coronary arteries in collaboration with European society of Cardiology working group on coronary pathophysiology & microcirculation endorsed by coronary vasomotor disorders international.
Presentation, clinical profile, and prognosis of young patients with myocardial infarction with nonobstructive coronary arteries (MINOCA): results from the VIRGO study.
Validation of the bleeding academic research consortium definition of bleeding in patients with coronary artery disease undergoing percutaneous coronary intervention.
Prognostic value of nonobstructive and obstructive coronary artery disease detected by coronary computed tomography angiography to identify cardiovascular events.
The prognosis of patients with nonobstructive coronary artery disease versus normal arteries determined by invasive coronary angiography or computed tomography coronary angiography: a systematic review.
Clinical characteristics, sex differences, and outcomes in patients with normal or near-normal coronary arteries, nonobstructive or obstructive coronary artery disease.
Determinants of long-term clinical outcomes in patients with angina but without obstructive coronary artery disease: a systematic review and meta-analysis.
Myocardial infarction with normal coronary arteries is common and associated with normal findings on cardiovascular magnetic resonance imaging: results from the Stockholm Myocardial Infarction with Normal Coronaries study.
Coronary optical coherence tomography and cardiac magnetic resonance imaging to determine underlying causes of myocardial infarction with nonobstructive coronary arteries in women.
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