Introduction
An increasing number of stable patients with evidence of ischemia but no obstructive
coronary artery disease (CAD) at coronary angiography, now termed INOCA, are seen.
Objective myocardial ischemia or limited coronary flow reserve (CFR) consistent with
coronary microvascular dysfunction (CMD) are identified in most of these patients.
Although these patients were previously thought to be at low risk for major adverse
cardiovascular events (MACE) and were provided only reassurance, newer data document
that stable INOCA patients are a heterogeneous population with an elevated MACE risk.
Primary prevention cardiovascular risk scores for asymptomatic populations may underestimate
risk in these patients, while secondary prevention risk scores developed in patients
with established cardiovascular disease may overestimate risk. Medical therapies may
be underutilized when no obstructive CAD is documented, and patients are commonly
discharged from specialty practice. We review the existing knowledge regarding observed
and predicted risk using available risk scores in stable INOCA patients to identify
knowledge gaps and plan investigation needed to develop evidence‐based guidelines
for this growing patient population.
INOCA—Prevalence
Patients with chest pain, evidence of ischemia but no obstructive CAD at coronary
angiography, now termed ischemia with no obstructive CAD or INOCA,1 are increasingly
recognized. Although there is likely overlap between INOCA and myocardial infarction
(MI) with no obstructive coronary arteries, which appears to be increasingly described,
our primary focus is INOCA, the non‐MI syndromes. These stable patients typically
have symptoms of chest pain suspected to be angina and/or abnormal stress testing,
in the setting of no obstructive CAD at coronary angiography.1, 2 The definition of
obstructive CAD varies between different guidelines or studies.3, 4, 5, 6, 7, 8, 9,
10 In general, “normal”‐appearing coronary arteries are defined as 0% luminal stenosis
or <20%, and non–obstructive CAD (NOCAD) is defined as luminal stenosis >20% but <50%.3,
8, 9, 10 However, some studies use a threshold of <70% for NOCAD,4 while anatomical
scores consider a stenosis ≥50% as significant.5, 6, 11 Traditional understanding
of obstructive CAD was 70%12; however, recent European Society of Cardiology and American
College of Cardiology/American Heart Association (ACC/AHA) guidelines shifted to include
stenosis of 50% to 70% if there is associated inducible ischemia or fractional flow
reserve ≤0.08 when considering the physiological significance of stenosis and revascularization
management in patients with stable CAD.6, 7
Depending on the study, up to half of patients undergoing coronary angiography have
no obstructive CAD,13, 14, 15 with a relatively higher prevalence in women (65% in
women versus 32% in men).15 Overall estimates in women and men from the Veterans Administration
Cardiovascular Assessment Reporting and Tracking System,16 the National Cardiac Data
Registry, and the National Heart, Lung, and Blood Institute–sponsored Women's Ischemia
Syndrome Evaluation (WISE)10 databases indicate that there are at least 3 to 4 million
American women and men with stable INOCA. Incurred healthcare costs are similar to
those for obstructive CAD.
Potential explanations for the apparent increasing prevalence of stable INOCA include
more sensitive diagnostics, including advanced cardiac imaging and high‐sensitive
troponins, which likely contribute to earlier detection of ischemic heart disease.
Furthermore, improved primary prevention risk factor control (reduced smoking, increased
aspirin and statin use) has likely contributed to altered atherosclerosis burden with
relatively less large‐vessel plaque rupture, potentially leading to less adverse arterial
remodeling/obstructive CAD,17 while increasing rates of obesity18 and diabetes mellitus19
may contribute to increasing prevalence of CMD or pathology.20, 21
The ACC/AHA non–ST‐segment–elevation MI guidelines refer to patients with MI and no
obstructive CAD as having Cardiac Syndrome X (CSX),22 while the European Society of
Cardiology stable CAD guidelines no longer use the term CSX when describing patients
with angina and no obstructive CAD12 because testing now allows the diagnosis of CMD
or macrovascular dysfunction12 in a majority of these patients. Previously, the term
CSX was used to refer to patients with no obstructive CAD but did not require proof
of ischemia23, 24 and also included patients with acute coronary syndromes and no
obstructive CAD.22, 23, 25 Advanced evaluation can now identify CMD or macrovascular
dysfunction by invasive or noninvasive measurements of CFR in a majority of these
patients,12, 26 while coronary atherosclerosis and better characterization of plaques
can be assessed by intravascular ultrasound, optical coherence tomography, or computed
coronary tomography angiography when not evident or appreciated at invasive coronary
angiography.27, 28, 29 Since CSX also includes clinical entities other than ischemia,
such as pericardial pain, inappropriate pain perception, and psychiatric syndromes,30
the term INOCA was established to improve the identification and management of patients
with ischemia and no obstructive CAD.1 In our opinion, the European Society of Cardiology
stable CAD guidelines more directly address recent INOCA data and practice implications
compared with the ACC/AHA guidelines.
Among both women and men, up to 60% of stable INOCA patients have documented CMD defined
as the presence of microvascular endothelial‐dependent and/or nonendothelial‐dependent
dysfunction.31, 32, 33 Furthermore, while the CMD was shown to be poorly correlated
with traditional risk factors, age was found to be an independent predictor of CMD
in both women and men.33 Female sex had a nearly significant association with CMD,
with an odds ratio of 1.21 (95% confidence interval, 0.98–1.40) compared with men.33
The high prevalence of endothelial and/or nonendothelial‐dependent CMD26, 31, 33 and
their correlation with outcomes26 underscores the role of comprehensive assessment
in patients with INOCA. Such functional alterations can be identified at a stage when
atherosclerotic lesions are not evident34 and may be useful in designing early effective
interventions to prevent the occurrence of subsequent coronary events.
Evidence of an Adverse Prognosis
Evidence from prospective registries indicate that stable INOCA patients are at more
elevated risk for future MACE, including death, nonfatal MI, nonfatal stroke, and
hospitalization for heart failure or angina than previously thought.
Documented MACE rates in stable INOCA patients are summarized in Table 1.4, 10, 15,
26, 35, 36, 37, 38, 39, 40, 41 Additionally, many of these patients have an adverse
quality of life, functional status, and exercise capacity with relatively frequent
visits to healthcare providers for persistent or recurring disabling symptoms.42 Elevated
MACE rates are observed both early after the index coronary angiogram (eg within the
first year) and at longer‐term follow‐up. In a study of 13 695 subjects, women with
nonobstructive CAD demonstrated a 3‐fold higher MACE rate compared with men and 2.55‐fold
increase compared with women with normal coronary arteries in the first year.43 Hospitalization
for heart failure was the most frequent event, with an observed 10‐fold higher rate
during longer‐term follow‐up compared with asymptomatic community‐based women.35 Studies
that additionally characterized function or anatomy such as myocardial ischemia, CFR,
plaque characterization, or calcium scoring further demonstrate relatively higher
MACE rates related to the presence or degree of such abnormalities (Table 1), in both
sexes. CMD was shown to be highly prevalent in stable INOCA patients and a CFR <2
was a powerful incremental predictor of MACE in both women and men.26 In symptomatic
subjects from the CONFIRM (coronary CT angiography evaluation for clinical outcomes
international multicenter) study there was a 2.5‐fold increase in risk of MI and all‐cause
mortality related to a higher CT‐Leaman plaque score.44 Similarly, an increased coronary
calcium score was related to greater risk of both 5‐year mortality and MACE in symptomatic
subjects without significant luminal narrowing.37, 45 The degree of global cardiac
magnetic resonance myocardial perfusion imaging was related to outcome in women with
INOCA.39
Table 1
Annuala MACE Rates in INOCA Patients
Author, Publication Year
Study Population
Test Performed
End Point
Results—Annual Events Ratea (%)
No Obstructive CAD—Anatomical Testing
Normal Coronary Arteries
Nonobstructive CAD
Gulati, 200935
Chest pain or noninvasive positive tests for ischemia
Coronary angiography
All‐cause death, nonfatal MI, nonfatal stroke, hospitalization for heart failure
1.5
3.1
Ovrehus, 201136
Stable angina
Coronary computed tomography angiography
Death and MI
0
0.6
Cardiac death, MI, revascularization
0
1
Jespersen, 201215
Chest pain
Coronary angiography
Cardiovascular mortality, hospitalization for MI, heart failure, or stroke
1.8
2.8
Petretta, 201237
Anginal symptoms and 15%–85% pretest likelihood of CAD
Coronary computed tomography angiography
Cardiac death, nonfatal MI, unstable angina, revascularization
0
3.4
Maddox, 20144
Chest pain or noninvasive positive tests for ischemia
Coronary angiography
All‐cause death, MI
1.48
2.41
Nielsen, 201741
Chest pain
Coronary computed tomography angiography
Revascularization MI, and all‐cause death
0.4
0.9
Kenkre, 201740
Chest pain or noninvasive positive tests for ischemia
Coronary angiography
All‐cause death
1
1.7
Cardiac death
0.6
1.1
No Obstructive CAD—Functional Testing
Normal Test
Abnormal Test
Johnson, 200410
Chest pain or noninvasive positive tests for ischemia
Magnetic resonance spectroscopy
All‐cause death, MI, heart failure, stroke, other vascular events, and hospitalization
for unstable angina
4.4
14
Schindler, 200538
Chest pain
Positron emission tomography
Cardiovascular death, acute coronary syndrome, MI, percutaneous transluminal coronary
angioplasty, coronary artery bypass grafting, ischemic stroke, or peripheral revascularization
0.9
5–7
Doyle, 201039
Chest pain or noninvasive positive tests for ischemia
Cardiac magnetic resonance imaging
All‐cause death, nonfatal MI, or hospitalization for worsening anginal symptoms
4
12
Murthy, 201426
Chest pain
Positron emission tomography
Cardiac death, nonfatal MI, late revascularization, and hospitalization for heart
failure
2.7
6.7
CAD indicates coronary artery disease; INOCA, ischemia and no obstructive coronary
artery disease; MACE, major adverse cardiovascular events; MI, myocardial infarction.
a
Annual MACE rate from the reported mean follow‐up events rate divided by the mean
years of follow‐up.
John Wiley & Sons, Ltd
Longer‐term follow‐up data from the WISE project confirmed a worse prognosis than
previously thought for stable INOCA women where 10‐year all‐cause death and cardiac
death rates were 17% and 11%, respectively, in women with nonobstructive CAD, and
10% and 6%, respectively, in women with normal coronary arteries.40 Furthermore, a
recent meta‐analysis of 48 studies including patients presenting with stable symptoms
undergoing either invasive or noninvasive coronary angiography demonstrated odds ratios
of 1.57 to 1.7 for MACE defined as cardiac death, nonfatal MI, hospitalization for
unstable angina, or revascularization in patients with NOCAD compared with their counterparts
with normal coronary arteries. The odds ratio remained high after excluding revascularization
as an outcome event.46
A number of studies now include comparison of patients with normal coronary arteries,
nonobstructive CAD, and obstructive CAD (Figure 1).4, 41, 47 Specifically, in the
Veterans Administration—Clinical Assessment, Reporting and Tracking System, patients
with nonobstructive CAD in 3 coronary arteries had a similar annual risk for MI and
death as patients with single‐vessel obstructive CAD.4 Risk was related not only to
the degree of luminal stenosis but also to the extent of the angiographic disease,
increasing with the number of vessels affected in both nonobstructive and obstructive
disease.4, 47
Figure 1
Annual MACE rate stratified by normal coronary arteries, nonobstructive CAD, and obstructive
CAD. Annual MACE rates from the reported mean MACE rate divided by the mean years
of follow‐up. CAD indicates coronary artery disease; MACE, major adverse cardiovascular
events; NCA, normal coronary arteries; NOCAD, nonobstructive coronary artery disease.
Outcomes include: Sharaf47: cardiovascular death or nonfatal MI; Maddox4: all‐cause
mortality or nonfatal MI; Nielsen41: all‐cause death, MI, late coronary revascularization;
Kenkre18: cardiac mortality; Kenkre18*, all‐cause death.
Primary Prevention Risk Scores
Current guidelines endorse use of primary prevention risk scores in asymptomatic patients.
Related to the asymptomatic populations used to develop primary prevention scores,
the Framingham Risk Score (FRS) appears to underestimate risk in women,48 while the
Reynolds Risk Score may perform better in selected populations.49 Among asymptomatic
subjects enrolled in the MESA (Multi‐Ethnic Study of Atherosclerosis), the current
guideline Atherosclerotic Cardiovascular Disease score and 3 older FRS‐based risk
scores overestimate MACE by 37% to 154% in men and 8% to 67% in women, while the Reynolds
Risk Score underestimated risk in women by almost one quarter.50 Whether knowledge
of the enrolled MESA subjects’ coronary artery calcium score led to activities to
reduce risk is not clear.51 The Atherosclerotic Cardiovascular Disease score accurately
predicted risk in the Reasons for geographic and racial differences in stroke, a contemporary
US dataset that includes representative ethnicity and socioeconomic status.52 A recent
study in stable INOCA patients undergoing Coronary Reactivity Testing (CRT) demonstrated
that a majority were classified as intermediate risk by FRS, which did not accurately
predict MACE, while the addition of coronary macro‐ and microvascular endothelial
dysfunction to the FRS correctly reclassified 23%, with a net reclassification index
of 0.23.53 Coronary endothelial dysfunction, both micro‐ and macrovascular, added
to the FRS in INOCA improved discrimination and risk stratification, further emphasizing
the crucial role of functional assessment.
Obstructive CAD Likelihood Scores
In symptomatic patients, clinical likelihood scores (eg Diamond/Forrester, Morise,
and CAD Consortium Pretest Probability score) assess the likelihood of obstructive
CAD. Several analyses now indicate that these scores overestimate the likelihood of
obstructive CAD in contemporary symptomatic patients undergoing noninvasive computed
coronary tomography angiography. Although designed for predicting likelihood of obstructive
CAD, the Diamond/Forrester and CAD Consortium Pretest Probability score were also
tested for prediction of MACE in the PARTNERS Registry, and demonstrated that the
CAD Consortium score had the highest discriminatory ability (area under the curve
0.687; 95% confidence interval, 0.646–0.728) for MACE.54 Similarly, the Morise pretest
clinical score that includes 9 variables to estimate the likelihood of obstructive
CAD effectively stratified WISE subjects according to the combined end point of cardiac
death/MI during a mean follow‐up of 3.4 years, with separation between the low‐risk
group and the others (P=0.012).55 The intermediate‐ and high‐risk groups were separable
for as long as 1.5 years, but thereafter, became less clearly separable.55 Other obstructive
CAD prediction scores developed in stable or acute chest pain patients have not been
tested for MACE prediction.
The newly developed PROMISE (Prospective Multicenter Imaging Study of Chest Pain)
minimal risk tool was designed to identify “low‐risk” patients in whom deferred noninvasive
testing (noninvasive coronary angiography or functional stress testing) may be considered.56
Subjects with minimal risk had a low‐risk profile (0.5% risk of cardiovascular death
and MI at a median 25 months). While this could be of use for risk stratification
in INOCA, prior studies suggest that the majority of INOCA patients are classified
in the “intermediate‐risk” class.36
Among patients with an intermediate pretest risk for obstructive CAD, with a normal
ECG and who can exercise, guidelines recommend that exercise ECG stress testing be
considered as the first test. In women evaluated for signs and symptoms of ischemia
undergoing clinically ordered coronary angiography in the WISE project, a pretest
clinical score and an exercise test score designed for use in women with suspected
CAD performed better than the commonly used Duke score in stratifying women with a
low prevalence of obstructive CAD.41, 55
Nevertheless, treadmill ECG stress testing, stress echocardiography, and single photon
emission computed tomography stress all have a limited sensitivity and specificity
for detection of ischemia in INOCA patients.57 This is not surprising given the lack
of a large regional territory of ischemia, as in the obstructive CAD populations used
to validate these techniques. Among subjects from the National Cardiovascular Data
Registry's Cath Percutaneous Coronary Intervention (CathPCI) undergoing invasive coronary
angiography for stable chest pain, while low‐ or intermediate‐risk findings on noninvasive
testing were associated with no obstructive CAD, the ability to predict MACE was not
tested.58 Notably, >50% of MACE occurred in subjects with normal stress testing in
the PROMISE,59 emphasizing the lower sensitivity and specificity to detect ischemia
in less than obstructive CAD. An anatomical computed coronary tomography angiography
approach offered better prognostic information once NOCAD was visualized.59 Furthermore,
mechanisms leading to acute coronary syndromes are not solely depending on degree
of luminal stenosis. An ischemic event is the consequence of a complex interaction
among plaque characteristics, endothelial dysfunction, coronary blood flow hemodynamics,
hemostasis factors, and metabolic, inflammatory, neurohormonal, and environmental
factors60 that are not addressed by commonly used tests.
Secondary Prevention Risk Scores
The Synergy between Percutaneous Coronary Intervention with TAXUS and Cardiac Surgery
(Syntax) II is a coronary angiographic‐based score used to optimize outcomes relative
to revascularization in obstructive CAD.12 Other secondary prevention scores are relevant
in early61, 62 or longer‐term63 risk stratification after a vascular event. Scores
using obstructive CAD variables are not applicable to INOCA patients. Recently, the
Gensini score, which includes lesser‐than‐obstructive CAD (epicardial luminal diameter
stenosis <50%), was found to be useful for prognosis in men and women referred for
invasive coronary angiography with no obstructive CAD.64 Previously, in women, a WISE
coronary angiographic score that assigned points according to severity of stenosis,
adjusted for the presence of collaterals and weighted by lesion location, predicted
MACE in stable INOCA patients. Specifically, MACE risk was positively associated with
increased coronary atherosclerosis scores in the absence of obstructive CAD.47
Additional scores developed for secondary prevention in patients with established
cardiovascular disease (CVD) do not include obstructive CAD as a variable, but were
developed in populations dominated by obstructive CAD,63, 65, 66, 67, 68, 69, 70,
71 and therefore are of unknown appropriateness for stable INOCA patients.
The Long‐Term Intervention with Pravastatin in Ischemic Disease (LIPID)63 score identifies
higher‐risk subjects on statin therapy, developed again in an obstructive CAD population.
A score from the Guangdong Coronary Artery Disease Cohort (GCADC) study65 had good
predictive value for mortality among secondary prevention patients, and the European
trial on reduction of cardiac events with perindopril in stable coronary artery disease
(EUROPA) score model predicted CVD mortality but not nonfatal outcomes or combined
end points.71 Again, these studies addressed mostly obstructive CAD patients.
The Second Manifestation of Arterial Disease (SMART),69 Thrombolysis In Myocardial
Infarction Risk Score for Secondary Prevention (TIMI‐TRS2oP),70 and A Coronary Disease
Trial Investigating Outcome with Nifedipine (ACTION) risk66 scores, all showed substantial
variability in risk among patients with stable CVD, but more importantly that aggressive
guideline treatment in high‐risk patients decreased their risk.69 Similarly, the PREDICT
CVD (New Zealand Primary Care Cohort Study) score developed for patients with previous
CVD recognizes patient‐specific risks of future events and how they may be reduced
through therapeutic and behavioral strategies.68
The “Cardiovascular Disease Research Using Linked Bespoke Studies and Electronic Health
Records” (CALIBER) score67 used real‐world commonly available data that contributed
to important prognostic information in unselected patients with a wide phenotype of
stable ischemic heart disease. The CALIBER models had good calibration and discrimination
in internal and external validation with C‐index 0.811 (0.735) for all‐cause mortality
and 0.778 (0.718) for nonfatal MI or coronary death in established stable ischemic
heart disease.67
Primary and Secondary Prevention Risk Versus Observed INOCA Risk
Comparison of primary, secondary prevention risk versus observed risk in an example
of stable INOCA patient is presented in Figure 2.40, 47, 56, 63, 65, 66, 67, 68, 69,
70, 71 The primary prevention scores, developed in asymptomatic populations, predicted
that risks vary between 1% and ≈5% and underestimate the observed INOCA risk. The
related primary prevention risk guidelines for these low‐risk scores would include
therapeutic lifestyle change and not statin therapy. Among secondary risk scores,
developed in symptomatic but mainly obstructive CAD patients, the predicted risk varied
widely, either over‐ or underestimating the observed INOCA risk.
Figure 2
Predicted primary and secondary prevention scores risk vs observed 10‐year risk in
an example INOCA patient. Model variables used: female, 55 years, hypertension, systolic
blood pressure 139 mm Hg on treatment, heart rate 80 bpm, total cholesterol 200 mg/dL
(5.17 mmol/L); low‐density lipoprotein 80 mg/dL (2.068 mmol/L), high‐density lipoprotein
60 mg/dL (1.55 mmol/L), high‐sensitivity C‐reactive protein (hs‐CRP) 2 mg/dL, creatinine
0.9 mg/dL (79 μmol/L), white blood cell count 10 K3/mL, hemoglobin 12 g/dL, no family
history, height 5′ 67″ (170 cm), weight 158 pounds (72 kg), body mass index 24.9,
low‐risk country, chest pain related to physical/mental stress, glomerular filtration
rate 60 mL/min per 1.73 m2. Predicted 10‐year Risk: Primary Prevention Risk Scores:
ASCVD—risk of cardiovascular death, nonfatal MI, nonfatal stroke; SCORE—risk of fatal
cardiovascular disease; Reynolds (RRS)—risk of myocardial infarction, ischemic stroke,
coronary revascularization and cardiovascular death; QRISK2—risk of MI or Stroke;
FRS CVD—risk of CHD or coronary insufficiency death, MI, or angina; Secondary Prevention
Risk Scores: CALIBER—myocardial infarction, cardiovascular death; GCAD—cardiovascular
death; PROMISE—myocardial infarction, cardiovascular death; ACTION—myocardial infarction,
stroke, all‐cause death; SMART—myocardial infarction, stroke, vascular death; LIPID—myocardial
infarction, cardiovascular death; EUROPA—cardiovascular death; TRS2P—myocardial infarction,
stroke, cardiovascular death; PREDICT—myocardial infarction, stroke, cardiovascular
death. The 10‐year risk was calculated from the reported risk divided by the numbers
of follow‐up years and then projected to 10 years. Observed 10‐year Risk: Sharaf—cardiovascular
death or MI (median follow‐up of 9.3 years); Kenkre—cardiac mortality (median follow‐up
9.5 years). ACTION indicates A Coronary disease Trial Investigating Outcome with Nifedipine;
ASCVD, Atherosclerotic Cardiovascular Disease; CAD, coronary artery disease; CALIBER,
Cardiovascular disease research using Linked Bespoke studies and Electronic Health
Records; EUROPA, European trial On reduction of cardiac events with Perindopril in
stable coronary Artery disease; FRS‐CVD, Framingham Risk Score Cardiovascular Disease;
GCAD, Guangdong Coronary Artery Disease Cohort; INOCA, ischemia and no obstructive
coronary artery disease; LIPID, Long‐Term Intervention with Pravastatin in Ischemic
Disease; NCA, normal coronary arteries; NOCAD, nonobstructive coronary artery disease;
PREDICT, Patients with Renal Impairment and Diabetes undergoing Computed Tomography;
PROMISE, Prospective Multicenter Imaging Study of Chest Pain; QRISK2, QRESEARCH cardiovascular
disease risk score; RRS, Reynolds Risk Score; SMART, Second Manifestation of Arterial
Disease; SCORE, Systematic Coronary Risk Evaluation; TRS2P, Thrombolysis In Myocardial
Infarction Risk Score for Secondary Prevention.
Cardiovascular Treatment Rates in INOCA Patients
Registry data demonstrate that half or less of stable INOCA patients are treated with
cardiovascular medication effective for ischemic heart disease, such as angiotensin‐converting
enzyme inhibitor or angiotensin II receptor blocker, β‐blocker, calcium channel blocker,
or statin therapies (Table 2).15, 41, 47, 72, 73, 74, 75, 76, 77 Furthermore, the
intensity of treatment, specifically for the maximally tolerated angiotensin‐converting
enzyme inhibitor/angiotensin II receptor blocker and potent statin categories, is
unknown in these registries. These findings suggest that the presence of normal coronary
arteries or NOCAD at coronary angiography may be associated with diagnostic and therapeutic
uncertainty, resulting in patients being less often treated with either primary prevention
or secondary prevention guidelines therapy. This practice seems unchanged despite
knowledge about adverse outcome in this population. The current ACC/AHA guidelines
for patients with stable CAD echoes the ACC/AHA recommendations for patients with
unstable angina/non–ST‐segment–elevation MI for subgroups of patients with no obstructive
CAD, which was defined as CSX.22, 78 While there have been studies evaluating therapy
in patients with CSX,79, 80, 81, 82 these studies are limited in their characterization
of coronary vasomotor function. Indeed, this emerging INOCA patient population remains
underdiagnosed and undertreated, likely perseverating this observed therapeutic equipoise.
The observed elevated MACE rate endorses this as a knowledge gap. Even mild degrees
of atherosclerosis or abnormal coronary vasoreactivity are related to increased health
risk.4, 26, 83, 84 Furthermore, the majority of MIs result from rupture of nonobstructive
plaque, highlighting the importance of optimizing therapy in these patients.85, 86
To date, limited data exist about the effectiveness of therapy in stable patients
with no CAD and high prevalence of CMD. Nevertheless, prior work in obstructive CAD
has demonstrated that atherosclerotic progression can be slowed and MACE reduced with
optimal medical therapy,69 while surrogate outcome trials in CMD patients indicate
improvement in endothelial function, CFR, and angina with optimal medical therapy,
as well.87 Patients with INOCA deserve to receive optimal treatment as per current
guidelines while awaiting future dedicated trials.
Table 2
Cardiovascular Treatment Rates in INOCA Patients
Author, Publication Year (n)
Hypertension/Angina Therapy (%)
Statin Therapy (%)
Maddox, 201072 (n=237 167)
51
47
Johnston, 201173 (n=5386)
21–56
51
Shaw, 201174 (n=824)
10–20
32
Jespersen, 201215 (n=5183)
44
50
Sedlak, 201275 (n=1864)
34
32
Sharaf, 201347 (n=567)
2–39
10a/31b
Chow, 201576 (n=10 418)
N/A
33.3
Nielsen, 201741 (n=14 205)
11.8–32.3
25–39.2
Galway, 201777 (n=2642)
18–46
34–59
Hypertension/Angina therapy includes: angiotensin‐converting enzyme inhibitor, angiotensin
II receptor blocker, β‐blocker, and calcium channel blocker medication. INOCA indicates
ischemia and no obstructive coronary artery disease; N/A, not applicable.
a
Normal coronary arteries.
b
Nonobstructive coronary artery disease.
John Wiley & Sons, Ltd
Implications and Conclusions
An increasing number of stable INOCA patients and observed elevated MACE rate calls
attention to several important knowledge gaps (Table 3). Existing primary and secondary
prevention risk assessment tools do not appear to predict MACE risk in INOCA patients;
investigation is needed to specifically address tools to accurately assess risk in
these patients. Furthermore, there appears to be diagnostic and therapeutic uncertainty
in INOCA patients with potentially inappropriately low rates of cardiovascular therapy
given the documented atherosclerotic and ischemia burden. Evidence‐based primary or
secondary treatment guidelines do not specifically address this population, which
is indicative of the absence of cardiovascular outcome trials in INOCA subjects. This
important knowledge gap must be addressed to get ahead of this emerging issue. Clinical
trials designed to test the impact of optimal medical therapy in INOCA patients are
needed.
Table 3
Knowledge Gaps in Stable INOCA
CVD Primary Prevention Guidelines
Stable CAD Guidelines
Secondary CVD Prevention Guidelines
Knowledge Gaps
Detection
N/A
Likelihood of CAD score
Limited to the presence of obstructive CAD
Limited to established coronary or other atherosclerotic vascular disease
Evidence regarding the utility, benefits, and risks of invasive and noninvasive detection
strategies in INOCA patients is needed to develop evidence‐based detection guidelines
Stress testing
Limited to the presence of obstructive CAD
CCTA
Limited to anatomical coronary plaque/stenosis and obstructive CAD flow
Coronary angiography
Limited to anatomical stenosis and obstructive CAD flow; no evidence‐based guidelines
for less than obstructive CAD
Risk assessment
Limited to asymptomatic patients
Limited to stable known or suspected obstructive CAD
Risks scores limited to prior MI and established CAD
Risk scores developed in INOCA populations to develop evidence‐based risk assessment
guidelines are needed
Treatment
Limited to asymptomatic patients
Echoes treatment recommendations for specific subgroups of patients from UA/NSTEMI
guidelines. Emphasis on the lack of dedicated treatment trials for INOCA
Limited to established coronary or other atherosclerotic vascular disease
MACE trials to inform evidence‐based guidelines for treatment strategies are needed
CAD indicates coronary artery disease; CCTA, computed coronary tomography angiography;
CVD, cardiovascular disease; INOCA, ischemia and no obstructive coronary artery disease;
MACE, major adverse cardiovascular events; MI, myocardial infarction; N/A, not applicable;
NSTEMI, non–ST‐segment–elevation myocardial infarction; UA, unstable angina.
John Wiley & Sons, Ltd
Sources of Funding
This work was supported by contracts from the National Heart, Lung, and Blood Institute
nos. N01‐HV‐68161, N01‐HV‐68162, N01‐HV‐68163, N01‐HV‐68164, grants U0164829, U01
HL649141, U01 HL649241, K23HL105787, T32HL69751, T32HL116273, R01 HL090957, 1R03AG032631
from the National Institute on Aging, GCRC grant MO1‐RR00425 from the National Center
for Research Resources, the National Center for Advancing Translational Sciences Grant
UL1TR000124 and UL1TR000064, and grants from the Gustavus and Louis Pfeiffer Research
Foundation, Danville, NJ, The Women's Guild of Cedars‐Sinai Medical Center, Los Angeles,
CA, The Ladies Hospital Aid Society of Western Pennsylvania, Pittsburgh, PA, and QMED,
Inc., Laurence Harbor, NJ, the Edythe L. Broad and the Constance Austin Women's Heart
Research Fellowships, Cedars‐Sinai Medical Center, Los Angeles, CA, the Barbra Streisand
Women's Cardiovascular Research and Education Program, Cedars‐Sinai Medical Center,
Los Angeles, The Society for Women's Health Research (SWHR), Washington, DC, The Linda
Joy Pollin Women's Heart Health Program, and the Erika J. Glazer Women's Heart Research
Initiative, Cedars‐Sinai Medical Center, Los Angeles, CA.
Disclosures
None.