Chest Pain With Normal Arteries: A Diagnosis, Not a Dead End

If you are having chest pain right now that is new, severe, or accompanied by shortness of breath, jaw pain, arm pain, or sweating, call emergency services immediately. Do not read further.

“Your arteries are clear” should be the second sentence of a longer conversation, not the last sentence of the appointment. When it functions as the last sentence, the clinician has answered one question and left several others unasked, and the patient leaves with a false assurance that the heart has been fully evaluated.

The clinical error this article addresses is the treatment of a normal coronary angiogram as the endpoint of a cardiac investigation, when it is actually a finding that redirects the investigation toward the coronary microcirculation.

The Mechanism

Coronary angiography is the reference standard for detecting obstructive atherosclerosis in the large epicardial coronary arteries. A catheter is advanced into the coronary ostia, contrast is injected, and X-ray fluoroscopy visualizes the vessel lumens. Stenoses of 50% or greater in diameter are considered hemodynamically significant. When the report reads “no obstructive coronary artery disease,” it means no significant narrowing was identified in the vessels that are large enough to be seen by this method.

The coronary microvasculature, defined as vessels with internal diameters below approximately 500 micrometers, is invisible on angiography. These microvessels are not decorative. They are the site of the majority of coronary vascular resistance and are responsible for regulating blood flow to the myocardium in response to demand. Angiography tells you nothing about them.

Microvascular angina arises when those small vessels fail to dilate appropriately in response to increased myocardial oxygen demand. The mechanisms include three overlapping pathophysiological processes. The first is functional impairment: the endothelium fails to produce adequate nitric oxide in response to shear stress or pharmacological stimulation, and the smooth muscle layer of the microvessels does not relax normally. The second is structural remodeling: chronic hypertension, diabetes, and estrogen deficiency each cause thickening of the arteriolar walls and narrowing of luminal diameters independent of atherosclerosis. The third is increased microvascular resistance at baseline, meaning that even resting coronary blood flow is lower than expected for the myocardial mass being supplied.

The measurable parameters that reflect these processes are coronary flow reserve (CFR) and index of microvascular resistance (IMR). CFR is the ratio of maximal blood flow achievable after pharmacological vasodilation (using adenosine or acetylcholine) to resting blood flow. Normal CFR is generally above 2.5; values at or below 2.0 are considered clearly abnormal and consistent with microvascular dysfunction. IMR is a pressure- and temperature-based index obtained with a coronary pressure wire and thermistor that quantifies the resistance of the microcirculation independent of epicardial vessel physiology. Elevated IMR indicates true microvascular disease rather than epicardial obstruction.

Coronary vasospasm is a distinct but frequently overlapping mechanism. In epicardial vasospasm, a large vessel undergoes transient and severe constriction that can completely occlude the lumen, producing ST-elevation ischemia. This is Prinzmetal’s or variant angina. In microvascular vasospasm, the spasm occurs at the level of the small vessels and produces angina without the dramatic angiographic findings of epicardial spasm. Both forms can coexist.

Vasospasm has a recognizable clinical signature. Chest pain tends to occur at rest rather than exclusively with exertion, is often worse at night or in the early morning hours when vagal tone is highest, and frequently responds to sublingual nitroglycerin. Cold exposure and emotional stress are recognized triggers. The distinction matters because the treatment differs from that of microvascular dysfunction: vasospasm is treated primarily with calcium channel blockers and long-acting nitrates, while microvascular dysfunction responds to a different pharmacological profile.

The diagnostic method for vasospasm is intracoronary acetylcholine provocation testing, performed during cardiac catheterization. Acetylcholine at physiologically appropriate concentrations should cause vasodilation through endothelium-dependent mechanisms; a vasospastic response manifests as constriction, which reproduces symptoms and confirms the diagnosis. The COVADIS (Coronary Vasomotion Disorders International Study) group published consensus diagnostic criteria for both microvascular angina and coronary vasospastic angina in 2016, providing the field with standardized definitions that have since been incorporated into international guidelines (Ong et al., Journal of the American College of Cardiology, 2018).

What the Evidence Shows

The epidemiology of this problem is not theoretical. The Women’s Ischemia Syndrome Evaluation (WISE), a prospective observational study conducted at four U.S. centers and funded by the National Heart, Lung, and Blood Institute, enrolled women referred for coronary angiography with suspected ischemia and followed them longitudinally. Principal investigators included C. Noel Bairey Merz and colleagues. The landmark finding: 65% of the women in WISE had no obstructive coronary artery disease on angiography. A substantial proportion of this group had measurable microvascular dysfunction by adenosine coronary flow reserve testing.

The critical second finding from WISE was what happened to these women over time. Those with coronary microvascular dysfunction had significantly higher rates of major adverse cardiac events during follow-up than women without ischemic symptoms, despite their normal epicardial arteries. At five-year follow-up, women with chest pain and no obstructive CAD had an annual major adverse cardiovascular event rate of approximately 2.5%, which is not the zero risk that “your arteries are clean” implies (Pepine et al., Journal of the American College of Cardiology, 2010). These women also reported persistently reduced quality of life and continued healthcare utilization driven by ongoing symptoms.

The WISE data established that the clinical outcome difference between “obstructive CAD” and “no obstructive CAD” in women presenting with chest pain is far smaller than previously assumed, and that the subgroup with identifiable microvascular dysfunction carries a meaningfully elevated risk profile.

The next evidence gap the field needed to close was therapeutic: does identifying the specific mechanism in a patient with non-obstructive CAD actually change outcomes? The CorMicA trial answered this question. Published in The Lancet in 2018 by Berry et al., CorMicA randomized patients with angina and no obstructive coronary artery disease at a United Kingdom center to one of two strategies: invasive coronary function testing with endotype-directed treatment, or blinded sham procedure with standard care. Invasive testing in the active arm used CFR and IMR to classify each patient as having microvascular dysfunction, vasospasm, both, or neither. Treatment was then matched to the endotype. Patients with microvascular dysfunction received intensified antianginal therapy directed at microvascular resistance. Those with vasospasm received calcium channel blockers and nitrates. Those with both received combination therapy.

At six months, the primary endpoint was the Seattle Angina Questionnaire (SAQ) summary score. Patients in the endotype-directed arm showed a statistically significant improvement in SAQ score of 11.7 points compared with 6.2 points in the control arm, a difference of approximately 5.5 points on the SAQ scale, which exceeds the threshold for clinical meaningfulness (Berry et al., Lancet, 2018). Angina frequency scores and physical limitation scores both improved significantly more in the active arm. The trial demonstrated that the mechanism matters for treatment selection and that identifying it produces measurably better angina control.

The European Society of Cardiology’s 2019 guidelines on chronic coronary syndromes (Knuuti et al., European Heart Journal, 2020) formally recognized coronary microvascular dysfunction and coronary vasospasm as diagnostic entities with specific criteria, dedicated investigation pathways, and treatment recommendations. The guidelines specify that invasive coronary function testing should be considered in patients with angina and no obstructive CAD when non-invasive testing has not provided a diagnosis, and they recommend acetylcholine provocation testing for suspected vasospasm. This is not experimental territory. It is guideline-endorsed standard of care.

Non-invasive assessment options exist for centers or clinical situations where invasive coronary function testing is not available or not performed. Stress cardiac MRI with adenosine or regadenoson can detect subendocardial perfusion abnormalities consistent with microvascular disease that are invisible to standard stress echocardiography. Coronary CT perfusion combines anatomic and functional assessment in a single acquisition. Neither non-invasive method has the diagnostic specificity of invasive CFR and IMR measurement, but both provide meaningful functional information that goes substantially beyond what an angiogram alone provides.

Treatment in INOCA: Matching Therapy to Mechanism

The CorMicA trial’s core contribution was demonstrating that knowing the endotype improves outcomes. The practical implication is that treatment in INOCA is not one-size-fits-all but mechanism-specific.

In microvascular dysfunction, the therapeutic target is reducing microvascular resistance and improving coronary flow reserve. Beta-blockers reduce myocardial oxygen demand by slowing heart rate and increasing diastolic filling time — both directly relevant to a microvascular system that already runs at reduced perfusion pressure. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers demonstrate endothelial benefits in microvascular disease in smaller randomized trials, likely through nitric oxide pathway restoration and anti-inflammatory mechanisms. Statins are now recommended in patients with INOCA and microvascular dysfunction regardless of LDL level, primarily for their endothelial and anti-inflammatory effects independent of lipid-lowering.

Ranolazine, a late sodium channel inhibitor approved for stable angina, showed specific benefit in microvascular angina in a randomized trial by Mehta and colleagues published in the Journal of the American College of Cardiology in 2011. Women with non-obstructive CAD and documented microvascular dysfunction who received ranolazine experienced fewer anginal episodes and improved myocardial perfusion on cardiac MRI compared with placebo. The mechanism involves improved diastolic relaxation and reduced wall stress, which lowers microvascular resistance independently of epicardial vessel tone. 4 / Promising

In coronary vasospasm, treatment differs substantially. Calcium channel blockers are the primary pharmacological agent, suppressing smooth muscle-mediated vasoconstriction at the coronary level. Long-acting nitrates provide additional vasodilatory support. Beta-blockers are generally avoided in pure vasospasm, as they may allow unopposed alpha-adrenergic vasoconstriction and paradoxically worsen symptoms in some patients. The distinction matters clinically: a patient with vasospasm started empirically on beta-blocker monotherapy may worsen, while the same patient treated with a calcium channel blocker after acetylcholine provocation testing confirms the endotype typically responds well.

Exercise rehabilitation in INOCA has support from WISE study follow-up data: women with non-obstructive CAD who had lower exercise capacity had substantially higher adverse event rates than those with better fitness. Structured aerobic training improves endothelial nitric oxide production, reduces sympathetic tone, and lowers microvascular resistance with sustained training exposure. The physiological rationale for cardiac rehabilitation in INOCA is coherent, and its underutilization reflects the historical tendency to reserve rehabilitation for patients with obstructive disease.

What to Do This Week

1. Request a specific answer about coronary function testing. If you have received a “normal angiogram” result for persistent chest pain, ask your cardiologist in direct terms: Was coronary function testing performed during the procedure? Was CFR or IMR measured? Was acetylcholine provocation testing done? If the answer to all three is no, ask whether referral for invasive or non-invasive functional assessment is appropriate for your situation.

2. Track the symptom pattern before your next appointment. Documenting whether your chest pain occurs at rest versus with exertion, whether it wakes you from sleep, whether it responds to nitroglycerin, and what triggers it (cold, stress, meals) provides the clinical pattern information that distinguishes microvascular angina from vasospasm before any testing is performed. Bring this record to your appointment.

3. Ask about non-invasive functional testing if invasive testing is not offered. Stress cardiac MRI with a vasodilator protocol or coronary CT perfusion can provide functional information about myocardial perfusion that goes well beyond what angiography assesses. These are available at most academic cardiology centers and are appropriate to request when invasive testing is not performed.

4. Pursue non-cardiac workup in parallel, not as a substitute. Esophageal causes of chest pain, including gastroesophageal reflux and esophageal spasm, are common and deserve evaluation. Musculoskeletal causes produce chest wall tenderness reproducible on physical examination. These workups should run concurrently with cardiac functional assessment, not as the default explanation when cardiac testing has been incomplete.

5. Name the clinical framework. The term INOCA, ischemia with non-obstructive coronary arteries, is the framework under which your symptoms may be evaluated. Knowing this term allows you to ask informed questions about whether your care has followed the diagnostic pathway for INOCA, and whether your center has experience with coronary function testing.

Normal coronary arteries on angiography are a meaningful finding that narrows the differential. They are not a diagnosis of exclusion, and they are not reassurance that the cardiac investigation is complete. The evidence from WISE, CorMicA, and the COVADIS consensus documents describes a clear investigative direction when the large vessels are clean and the symptoms persist. That direction has a name, it has a physiology, it has diagnostic tools, and it has treatments that produce measurably better outcomes when applied to the right patients. The appropriate response to a normal angiogram in a patient with ongoing chest pain is the next question.