The Heart Attack and the Ischemia That the Angiogram Cannot See

Dr. Job Mogire, MD, FACP, FACC Board-Certified Cardiologist | Carle Foundation Hospital, Champaign, IL

A coronary angiogram is the test cardiology trusts most, and it is built to answer one question: is there an obstructive blockage in a large coronary artery? When the answer is no, the reflexive conclusion has long been that the heart is not the problem. For a large group of patients, most of them women, that conclusion is wrong. Two diagnoses, MINOCA and INOCA, describe genuine ischemic heart disease that a clean angiogram does not exclude.

Two diagnoses, one blind spot

MINOCA, myocardial infarction with non-obstructive coronary arteries, is a heart attack, with elevated troponin and clinical evidence of infarction, in the absence of obstructive disease on angiography. 5 / Solid The AHA scientific statement on MINOCA established it as a working diagnosis requiring a search for cause rather than a dismissal, and it is more common in women than men (Tamis-Holland et al, Circulation 2019).

INOCA, ischemia with non-obstructive coronary arteries, is the chronic counterpart: objective or symptomatic ischemia without a flow-limiting stenosis. Its principal mechanisms are coronary microvascular dysfunction and vasospasm, and it accounts for a substantial share of women with persistent angina and clean angiograms.

The evidence that it is real disease

The Women’s Ischemia Syndrome Evaluation (WISE) program documented that women with signs and symptoms of ischemia but no obstructive disease carry meaningful adverse cardiovascular risk rather than a benign condition. 4 / Promising This reframed non-obstructive ischemia from reassurance to a problem requiring management.

The CorMicA trial closed the diagnostic loop. Patients with angina and non-obstructive disease underwent invasive coronary function testing, and management stratified by the result, microvascular versus vasospastic endotype, improved angina and quality of life compared with usual care (Ford et al, JACC 2018). 4 / Promising The finding matters because it shows the diagnosis is actionable: identifying the endotype changes treatment and outcomes.

What the workup should include

For MINOCA, the task is to find the mechanism: cardiac MRI to characterize the myocardium and distinguish infarction from mimics such as myocarditis or Takotsubo, and assessment for plaque disruption, spasm, and other causes. For INOCA, the task is to characterize coronary function: testing for microvascular dysfunction, measured through coronary flow reserve and microvascular resistance, and for vasospasm through provocation, following the COVADIS framework.

What this means

MINOCA and INOCA are not diagnoses of exclusion to reassure a patient with a clean angiogram. They are specific conditions, more common in women, with established workups and treatments that improve symptoms. The decisive shift is to treat a normal angiogram in a symptomatic woman as a prompt for further testing rather than a conclusion. The disease the angiogram cannot see is still disease, and it is increasingly one that cardiology knows how to find and manage.

The mechanisms behind MINOCA: what actually happened to the artery

MINOCA is not a single disease. It is a clinical presentation with multiple distinct causes, and the workup exists precisely to determine which one applies. Understanding these mechanisms matters because each one carries a different prognosis and requires a different treatment approach.

Plaque disruption without obstruction. A coronary plaque can rupture or erode and trigger thrombosis without producing a flow-limiting stenosis visible on angiography. The thrombus may be small, may have partially lysed by the time the angiogram is performed, or may have embolized distally. Optical coherence tomography, which provides cross-sectional arterial wall imaging at far higher resolution than angiography, has demonstrated plaque disruption in a meaningful proportion of MINOCA cases that angiography characterized as normal. This is not a rare curiosity; it is one of the more common MINOCA mechanisms and it changes downstream antiplatelet and statin management substantially.

Coronary spasm. Epicardial coronary spasm can produce complete or near-complete transient occlusion of an artery that, in its resting state, appears unobstructed on angiography. The spasm resolves, flow returns, and the angiogram looks clean. Without provocation testing, typically with acetylcholine or ergonovine during the catheterization, the spasm will never be identified. Women with vasospastic angina are more likely to have atypical symptom patterns and to present without the classic exercise-triggered chest pain pattern, which compounds the diagnostic delay.

Coronary microvascular dysfunction. In MINOCA, microvascular dysfunction can cause ischemia severe enough to produce troponin elevation without epicardial obstruction. The mechanism involves impaired microvascular perfusion at the level of the arterioles and capillaries rather than the large vessels, and it can produce patchy myocardial injury visible on cardiac MRI even when the epicardial vessels are angiographically clean.

Myocarditis mimicking MINOCA. Myocardial inflammation, including immune-mediated and viral myocarditis, elevates troponin and can produce regional wall-motion abnormalities and ECG changes that closely resemble myocardial infarction. Without cardiac MRI, this distinction cannot be made reliably. Myocarditis has a different natural history, different management, and different implications for physical activity and future risk. Lumping it under an uninvestigated MINOCA label is a clinical error with consequences.

Takotsubo cardiomyopathy. Takotsubo, also called stress cardiomyopathy, produces transient left ventricular dysfunction with a distinctive apical ballooning pattern, typically triggered by intense emotional or physical stress. It presents with chest pain, ECG changes, and troponin elevation and can be mistaken for MINOCA or STEMI. Cardiac MRI and ventriculography distinguish it from infarction. It is far more common in postmenopausal women than in men or younger women, and while it typically resolves, it carries real short-term risk including cardiogenic shock and arrhythmia. Identifying it correctly removes the patient from anticoagulation and antiplatelet regimens that may not be indicated and directs follow-up appropriately.

Why women are affected disproportionately

The sex disparity in MINOCA and INOCA is not fully explained, but several biological and clinical factors converge to make women more susceptible to these non-obstructive ischemic presentations.

Estrogen plays a significant role in endothelial health. Estrogen stimulates nitric oxide production in the vascular endothelium, promoting vasodilation and protecting against inflammation. The decline in estrogen at menopause removes this protection, and the transition period itself is associated with measurable deterioration in coronary microvascular function. This is one reason MINOCA and microvascular dysfunction peak in the perimenopausal and postmenopausal years for women, while atherosclerotic MI remains more common in men until women’s risk catches up in older age.

Women also have smaller coronary artery caliber relative to body size, which may influence susceptibility to both spasm and microvascular dysfunction. Smaller vessels are more sensitive to vasomotor dysregulation and may produce more severe ischemia for a given degree of dysfunction.

The hormonal environment also influences coronary tone directly. Progesterone and estrogen both modulate vascular smooth muscle responsiveness, and fluctuations across the menstrual cycle can affect the threshold for coronary spasm in susceptible women. Some women with vasospastic angina report symptom patterns that track with their cycle.

There are also clinical reasons for the apparent disparity: women with non-obstructive ischemia have historically been less likely to receive the investigations that would identify their mechanism, so the population of diagnosed women reflects both true biological excess and a diagnostic system that was more likely to identify and pursue disease in men.

The WISE-CVD extension and its findings

The WISE program, conducted across multiple academic centers, enrolled women with chest pain or suspected ischemia referred for coronary evaluation. The extension into WISE-CVD added rigorous follow-up and functional testing. Among women with signs of ischemia but no obstructive disease, the program found adverse cardiovascular event rates substantially higher than expected for a population told they had “normal” hearts. 4 / Promising Noel Bairey Merz and colleagues documented that these women had higher rates of major adverse cardiovascular events, hospitalizations, and repeat procedures compared with asymptomatic women, and that coronary flow reserve measured invasively predicted outcomes independent of standard risk factors (Reis et al, NEJM 2001).

This finding reframed the category. The woman discharged with reassurance after a normal angiogram is not at negligible risk. Her risk is real, it is measurable, and it correlates with coronary function measures that standard care routinely omits. The clinical implication is not to alarm but to act: measure, characterize, and treat rather than reassure and discharge.

Long-term prognosis data for MINOCA patients

MINOCA carries adverse long-term prognosis that most patients are never told about at discharge. A Swedish MINOCA registry analysis including over 9,000 patients found that one-year major adverse cardiovascular event rates, including recurrent MI, stroke, and death, were meaningfully elevated compared with the general population, though lower than in obstructive MI (Lindahl et al, JAMA Cardiology 2017). 4 / Promising The patients who fared worst were those who received no secondary prevention treatment, consistent with the hypothesis that the underlying mechanisms, when unaddressed, continue to produce adverse events.

The prognosis varies by mechanism. MINOCA from plaque disruption carries a different trajectory than MINOCA from myocarditis or Takotsubo. This is another argument for the full workup: the outcome data that exist are mechanism-specific, and treating all MINOCA as uniform is both intellectually imprecise and clinically insufficient.

Women make up a majority of MINOCA cases in most registries, and outcomes data consistently show that they are less likely to receive secondary prevention therapies, including statins and antiplatelet agents, than men with obstructive MI. This gap is not biologically justified; it reflects the historical assumption that a clean angiogram means a benign condition.

The role of cardiac MRI in MINOCA workup

Cardiac MRI is not an optional add-on for MINOCA. It is the investigation that makes the workup complete. 4 / Promising Its specific contributions are as follows.

Late gadolinium enhancement distinguishes ischemic scar from myocarditis. Infarction produces subendocardial or transmural enhancement in a coronary territory distribution. Myocarditis produces patchy mid-wall or epicardial enhancement, typically not in a coronary territory, often in the lateral wall. This distinction cannot be made from troponin, ECG, or angiography alone.

T1 and T2 mapping quantify myocardial edema and inflammation, allowing characterization of the acute injury pattern and providing objective evidence of the disease type even in the absence of classic late gadolinium enhancement.

In Takotsubo, cardiac MRI demonstrates the absence of late gadolinium enhancement in the dysfunctional territory and often shows myocardial edema consistent with stunned but viable myocardium, a pattern distinct from infarction.

Cardiac MRI also characterizes ventricular function precisely. In a patient presenting with regional dysfunction and elevated troponin, the MRI provides a baseline against which recovery can be measured, which matters for Takotsubo, where the expectation is complete functional recovery, and for myocarditis, where follow-up imaging guides decisions about return to activity.

The ESC position statement on MINOCA specifically identifies cardiac MRI as a recommended investigation when the cause is not established by clinical assessment and angiography. The question is not whether to order it but whether the clinical system will deliver it, since MRI slot availability and ordering patterns vary considerably by institution.

What happens when MINOCA is missed or dismissed

The downstream harm of an uninvestigated MINOCA is concrete and preventable. A woman sent home without a mechanism diagnosis does not receive secondary prevention tailored to her cause. If her MINOCA was from plaque disruption, she is not on antiplatelet therapy and a statin with the intensity that evidence supports. If it was from spasm, she is not on a calcium channel blocker and may be on aspirin that does little for vasospasm. If it was from myocarditis, she may be returning to vigorous exercise before inflammation has resolved, a pattern associated with arrhythmia risk.

Repeat presentations are common. Women with uninvestigated MINOCA return to emergency departments with recurrent chest pain, repeat elevated troponin, and sometimes another acute coronary event. Each of these encounters is a missed opportunity that was preceded by a discharge with inadequate investigation.

The psychological harm compounds the physical. A woman told her heart is fine while she continues to have disabling symptoms, or who has a second event after being told she was at low risk, has grounds to distrust the medical system that failed her. That distrust is rational, but it also interferes with future care-seeking at exactly the moments when timely care is most important.

Questions to ask your cardiologist after a MINOCA or INOCA diagnosis

The following questions are not aggressive or adversarial. They are the questions a patient with an incomplete workup should be able to answer, and if she cannot, the workup is incomplete.

After MINOCA: Did I have a cardiac MRI? If not, why not, and can it still be done? Do you know what caused my heart attack, as in the specific mechanism? Based on the mechanism, what secondary prevention medications am I on, and why those specifically? What is my risk of a recurrent event, and what would change that risk? Are there activities I should avoid, and for how long?

After INOCA: Has anyone measured my coronary flow reserve or performed coronary function testing? If not, has my endotype been characterized at all? Am I being treated for microvascular disease, vasospasm, or both, and how was that determined? What does my long-term prognosis look like given current management?

These questions are not designed to challenge the cardiologist. They are designed to reveal whether the diagnosis is complete. A cardiologist who has done the full workup will answer them readily. If the answers are absent or vague, the appropriate next step is referral to a center with expertise in coronary function testing and MINOCA evaluation.