When the Artery Squeezes Itself Shut: Coronary Vasospasm

Some chest pain is not a blockage in the artery. It is the artery clamping down on itself, then releasing. The test for it is specific, and so is the treatment.

Coronary vasospasm is focal, intense, transient constriction of one or more epicardial coronary arteries. The artery is not blocked by plaque. There is no fixed stenosis. Instead, the smooth muscle in the arterial wall contracts abnormally, narrowing or completely closing the lumen for minutes. Flow to the downstream myocardium is reduced or stopped. Ischemia follows. The spasm then releases, the artery returns to its resting caliber, and the angiogram, if performed after this, shows nothing.

This is why vasospastic angina has been historically underdiagnosed: the test that confirms coronary anatomy looks normal, because it is looking at the anatomy after the event rather than during it.

What dismissal looks like

A woman in her mid-40s, otherwise healthy, begins waking at 3 a.m. with a tight pressure in the center of her chest. It lasts ten minutes, then disappears on its own. She is not exerting herself. She is not anxious. It happens again three nights later, then twice the following week. She goes to her doctor, who orders a stress test. The stress test is normal. She goes to the emergency department during an episode, and by the time the ECG is running, her chest is already clearing. The ECG shows nothing. She is admitted, observed, and discharged with a diagnosis of atypical chest pain, possibly musculoskeletal. Her angiogram, performed the following month, shows clean coronary arteries. She is told she is fine and that the pain was probably anxiety.

The pain continues for another eight months. She keeps a diary, accumulates 40 episodes, and goes back to her cardiologist with documentation that every single episode occurs at rest, predominantly between 2 and 5 a.m. She asks directly whether provocation testing has been considered. It has not. She is referred to a center that performs acetylcholine testing. The test is positive: greater than 90% focal constriction of her left anterior descending artery, with reproduction of her typical symptoms. She is started on diltiazem. The episodes stop within two weeks.

Her angiogram was not wrong. The question it answered was correct for the question it was asked. It was asked the wrong question.

The biology of vasospasm

Vasospasm is not a random event. It reflects a specific failure at the level of the arterial wall.

Under normal conditions, the endothelium, the single layer of cells lining the inside of every artery, releases nitric oxide continuously in response to shear stress from blood flowing across its surface. Nitric oxide diffuses into the underlying smooth muscle cells and activates pathways that keep those cells relaxed. The artery stays open. This is the baseline state.

In vasospastic disease, endothelial nitric oxide production is impaired. The mechanism varies by patient: oxidative stress degrades nitric oxide before it can act; inflammatory injury reduces endothelial nitric oxide synthase expression; post-menopausal estrogen loss removes one of the key stimulants of nitric oxide production. When nitric oxide signaling falls, the vascular smooth muscle cells lose their tonic inhibition and default toward contraction.

The Rho-kinase pathway is now understood to be central to this contraction. Shimokawa H, writing in Cardiovascular Research in 1999, identified overactive Rho-kinase signaling as a key mechanism of coronary vasospasm: Rho-kinase phosphorylates myosin light chain phosphatase, inactivating it, which increases the sensitivity of the contractile apparatus to calcium. The smooth muscle cell contracts at calcium concentrations that would not normally trigger contraction. This calcium sensitization is the reason calcium channel blockers, which reduce calcium influx, work well but sometimes incompletely. The Rho-kinase problem persists even when calcium influx is partially blocked. This is also why some patients require high-dose calcium channel blockade or combination therapy for adequate suppression.

The endothelium in affected arteries is functionally injured even when the angiogram appears structurally normal. The artery looks clean because there is no plaque. The problem is in the signaling, not the anatomy.

The classic pattern and where it diverges

Vasospastic angina was described by Prinzmetal in 1959 as a syndrome of rest-predominant chest pain associated with transient ST elevation on ECG, occurring particularly in the early morning hours. 5 / Solid This pattern, nocturnal onset, rest rather than exertion predominance, transient ST changes that resolve with the pain, remains the characteristic clinical picture.

Not all vasospastic angina fits this classic pattern. Spasm can occur during exertion as well as rest. It can present with ST depression rather than elevation. Symptoms are sometimes preceded by exposure to cold, emotional stress, or smoking rather than occurring spontaneously. In some patients, spasm is entirely asymptomatic on the ECG record but detectable only by provocation testing.

The COVADIS criteria (Coronary Vasomotion Disorders International Study Group) formalized a diagnostic framework for vasospastic angina requiring: typical symptoms, a documented episode with ischemic ECG changes or confirmed by provocation testing, and evidence of spasm. This framework standardizes diagnosis across centers and is referenced in ESC guidelines on chronic coronary syndromes. 4 / Promising

Vasospasm as a MINOCA mechanism

Coronary vasospasm is a recognized cause of MINOCA: myocardial infarction with non-obstructive coronary arteries. When spasm is complete and sustained for long enough, downstream ischemia progresses to infarction. Troponin rises. The ECG may show transient ST elevation. By the time the angiogram is performed, the spasm has resolved. The artery looks normal. The heart attack was real.

The Tamis-Holland 2019 AHA Scientific Statement on MINOCA lists vasospasm as one of the primary etiologies requiring consideration in MINOCA workup. 5 / Solid A MINOCA patient with rest-predominant symptoms, nocturnal onset, or a history of spasm triggers is a candidate for acetylcholine provocation testing if it was not done at the initial catheterization.

Vasospasm also carries risk of life-threatening ventricular arrhythmia during the ischemic period. Sustained spasm can produce ventricular fibrillation. This is why untreated or undiagnosed vasospastic angina carries a risk profile that goes beyond symptom burden.

The provocation test

Acetylcholine provocation testing is the diagnostic gold standard. 4 / Promising It is performed during cardiac catheterization by delivering incremental intracoronary doses of acetylcholine while the coronary arteries are imaged. Acetylcholine normally produces mild vasodilation through endothelial nitric oxide release. In patients with abnormal vasomotor tone, the smooth muscle response overrides the endothelial effect and the artery constricts.

What the test actually involves: the patient is on the catheterization table with continuous 12-lead ECG monitoring throughout. After standard coronary angiography confirms non-obstructive disease, the catheter is positioned in the coronary ostium and acetylcholine is infused in escalating doses, typically 2 mcg, then 20 mcg, then 100 mcg, with imaging and ECG recording at each step. The operator watches the coronary silhouette in real time, and the patient is asked to report any symptoms. The entire protocol takes roughly 20 to 30 minutes per vessel. Atropine is available at the bedside throughout because acetylcholine can induce bradycardia via muscarinic receptors. If a severe positive response occurs, intracoronary nitroglycerin terminates the spasm within seconds.

A positive test requires: focal constriction greater than 90%, reproduction of the patient’s typical symptoms, and ischemic ECG changes. This triad confirms vasospasm as the mechanism of the patient’s ischemia. A partial response, constriction without symptoms or ECG changes, is interpreted differently and does not meet criteria for vasospastic angina.

The safety profile at experienced centers is acceptable. Major complications, sustained arrhythmia or infarction from the test itself, are uncommon at high-volume centers with standardized protocols. This is relevant because the test’s safety is sometimes cited as a reason not to offer it; the real issue is that it requires training, equipment, and an operator willing to induce the thing the patient has been told they do not have.

The CorMicA trial (Ford et al., JACC 2018) performed systematic invasive physiologic testing including acetylcholine provocation in patients with chest pain and non-obstructive coronary arteries. Endotype-specific therapy assigned on the basis of test results improved six-month angina scores and quality of life compared with standard care. 4 / Promising This is the evidence base for why finding the specific diagnosis, rather than stopping at “clean arteries,” changes outcomes.

Acetylcholine provocation is underused in the United States. It is routine in Japan, where vasospastic disease is most intensively studied and managed. Access to centers that perform it in the US is uneven, and referral to a high-volume center is appropriate when vasospasm is on the differential and local capability is absent.

Why women are particularly affected

Vasospastic angina is not equally distributed between sexes. The data consistently show a higher prevalence in women, with the disparity most pronounced in the post-menopausal period. Kawano H et al., writing in the Journal of the American College of Cardiology in 1996, documented significant gender differences in vasospastic angina, noting that estrogen status is a determinant of vasomotor tone: premenopausal women with vasospastic angina had worse endothelial function than age-matched controls, and their symptoms often worsened in the luteal phase of the menstrual cycle, when estrogen levels fall transiently. 4 / Promising

The mechanism runs through the same nitric oxide pathway described above. Estrogen upregulates endothelial nitric oxide synthase, the enzyme that produces nitric oxide in the arterial wall. This is one reason premenopausal women have, on average, better coronary vasomotor tone than age-matched men. When estrogen falls at menopause, that protective effect diminishes. Endothelial nitric oxide production decreases. The smooth muscle cells become more reactive. In women with underlying susceptibility to vasospasm, this transition can unmask or worsen the condition.

This has a direct clinical implication: a woman in her late 40s or early 50s with new-onset chest pain at rest, particularly if the pattern corresponds temporally with perimenopause, should have vasospastic angina in the differential from the first visit. The pattern of symptom emergence around the menopausal transition is a specific clinical signal that points toward estrogen-related endothelial dysfunction as a contributing mechanism.

The intersection with dismissal is not accidental. Women with chest pain and clean angiograms are more likely to be told their symptoms are non-cardiac. Vasospastic angina is a condition that predominantly affects women, presents with normal angiography, and resolves spontaneously between episodes. Each of these features, individually, makes a clinician less likely to pursue the diagnosis. Together they create a systematic gap between who has the disease and who gets appropriately evaluated for it.

Knowing this does not require patience with the gap. It requires naming it and asking for the test.

Treatment: what works and what to avoid

Calcium channel blockers are the primary therapy. Both dihydropyridines (amlodipine, nifedipine) and non-dihydropyridines (diltiazem, verapamil) reduce spasm frequency. High doses are sometimes needed for adequate suppression. 4 / Promising

Long-acting nitrates add benefit in combination with calcium channel blockers for patients with frequent episodes.

Beta-blockers are generally avoided in vasospastic angina, or used only with caution. Unopposed alpha-adrenergic tone can worsen spasm. If a patient also has obstructive disease requiring beta-blockade, the vasospasm component should be managed simultaneously with a calcium channel blocker.

Smoking cessation reduces spasm frequency and is among the highest-yield interventions available. Smoking increases sympathetic tone and impairs endothelial nitric oxide production. The effect is dose-dependent and the reduction in events with cessation is documented. 4 / Promising

Trigger avoidance: cold exposure, stimulant drugs including cocaine, vasoconstricting medications such as triptans and ergotamines. Triptans, which are commonly prescribed for migraine and frequently used by women in the perimenopausal age range, are potent vasoconstrictors and should be reviewed in any patient with confirmed vasospastic angina.

Coronary Microvascular Dysfunction: The Overlapping Diagnosis That Requires Different Testing

Vasospastic angina involves the large epicardial coronary arteries — the vessels visible on standard angiography. A second and increasingly recognized condition, coronary microvascular dysfunction (CMD), involves the small resistance vessels that are below the resolution of angiographic imaging. Both conditions produce chest pain or MINOCA with a clean standard angiogram. Both disproportionately affect women. And both require specialized testing beyond standard catheterization to diagnose. The mechanisms are distinct and the treatments differ, which is why distinguishing them matters.

In coronary microvascular dysfunction, the problem is not intermittent constriction of large vessels. It is impaired vasodilation of the small intramyocardial resistance arteries, typically defined as vessels below 500 micrometers in diameter. These vessels account for approximately 40 percent of total coronary vascular resistance at rest, and they are responsible for the appropriate increase in blood flow during exertion or stress. When they fail to dilate adequately — whether from endothelial dysfunction, inflammation, autonomic dysregulation, or structural remodeling — the heart cannot receive adequate oxygen under increased demand, producing ischemia that looks identical clinically and on ECG to ischemia from obstructive epicardial disease.

The diagnostic metric is coronary flow reserve (CFR): the ratio of maximal coronary blood flow induced by vasodilatory challenge (typically adenosine or regadenoson) to resting coronary blood flow. A CFR below 2.0 is the standard definition of CMD in invasive physiologic testing. Measuring it requires a pressure/flow wire placed during cardiac catheterization — it must be intentionally added to the procedure and does not happen automatically when a standard angiogram returns clean.

Data from the WISE (Women’s Ischemia Syndrome Evaluation) study, reported by Pepine and colleagues in JACC, demonstrated that nearly half of women referred for coronary angiography for suspected ischemia who had no obstructive coronary disease showed abnormal coronary vasoreactivity — either microvascular dysfunction or spasm — when tested with provocative protocols. This established CMD as a common cause of ischemic symptoms in women with clean angiograms, not a rare exception. 4 / Promising

The COVADIS (Coronary Vasomotion Disorders International Study Group) has published consensus diagnostic criteria for CMD to parallel those for vasospastic angina. The criteria include the symptom pattern, evidence of microvascular origin (such as slow coronary flow or a perfusion defect in the absence of epicardial disease), and an abnormal CFR or elevated microvascular resistance on provocative testing.

The treatment overlap between CMD and vasospastic angina is partial but not complete. Calcium channel blockers reduce smooth muscle reactivity across vessel sizes and help both conditions. Beta-blockers, which are contraindicated in vasospasm, may have a role in CMD by reducing myocardial oxygen demand. Ranolazine, which improves ischemic tolerance without affecting vasomotion, has shown benefit specifically in CMD and is not a standard vasospasm treatment. Identifying which condition is present determines which pharmacological approach is appropriate — and that distinction requires provocative testing, not a standard angiogram alone.

What to do this week

1. If you have recurring chest pain at rest, particularly with a nocturnal or early morning pattern, and your angiogram was clean, ask whether acetylcholine provocation testing was performed. If not, ask whether it should be.

2. If you are currently on a beta-blocker for chest pain and have not had a vasospasm evaluation, ask your cardiologist to review whether vasospastic angina should be in your differential before continuing or escalating beta-blocker therapy.

3. Smoking is a direct vasospasm trigger. If you smoke and have any of the above pattern, cessation is not optional background advice; it is first-line treatment.

4. Keep a symptom diary: time of onset, activity versus rest, duration, what resolved the pain. Rest-predominant and nocturnal patterns are the clinical signal that makes vasospasm the leading diagnosis.

5. If you use triptans for migraine and have been told you have chest pain with clean coronaries, bring both conditions to the same visit. The medication you use for one problem may be triggering the other.

6. If your symptoms changed around perimenopause, say that explicitly to your cardiologist. It is clinically relevant information and it belongs in the differential.

Vasospasm has a mechanism, a specific test, and a specific treatment. The path from symptom to therapy runs through the diagnosis. The test exists. The treatment works. The barrier is almost always the question being asked rather than the answer available.