Coronary Artery Vasospasm and Prinzmetal Angina

Etiology

The development of coronary artery vasospasm reflects a multifactorial process influenced by the autonomic nervous system, inflammation, oxidative stress, endothelial dysfunction, smooth muscle cell hypercontractility, genetic predisposition, and lifestyle factors.

Primary (idiopathic) coronary artery vasospasm arises primarily from endothelial dysfunction and smooth muscle hyperreactivity. Endothelial dysfunction reduces nitric oxide production, impairs vasodilation, and promotes a predisposition toward vasoconstriction. Increased sensitivity to vasoconstrictors, eg, acetylcholine and serotonin, enhances intracellular calcium influx, producing exaggerated vasoconstrictive responses.

Molecular and cellular mechanisms contribute significantly to disease expression. Oxidative stress reduces nitric oxide availability, while inflammation increases vascular reactivity. The Rho-kinase pathway is a key mediator of smooth muscle contraction and vasospasm. Autonomic imbalance, including sympathetic stimulation, further contributes to heightened vascular tone and episodic vasoconstriction.

Modifiable risk factors play a central role, with smoking demonstrating the strongest association with coronary artery vasospasm. Additional contributors include alcohol use, emotional stress, and cold exposure. Drug-induced vasospasm occurs with agents, eg, amphetamines, ergot alkaloids including ergotamine, triptans, and certain chemotherapeutic drugs (eg, 5-fluorouracil).

Associated medical conditions also contribute to susceptibility. Even mild atherosclerotic changes may serve as focal sites for spasm. Disorders, eg, migraine and Raynaud phenomenon, demonstrate shared vasospastic tendencies. Genetic predisposition includes polymorphisms affecting endothelial nitric oxide synthase and Rho-kinase activity, which increase susceptibility to vasospasm, with higher prevalence reported in East Asian populations.[5][6][7][8]

Epidemiology

The prevalence of coronary artery vasospasm peaks between ages 40 and 70 and declines after age 70. Geographic distribution varies globally, with the highest incidence reported in the Japanese population compared with Western populations. Provocative testing also demonstrates a higher frequency of multivessel spasm in Japanese patients, occurring in approximately 23%, compared with 7.5% in Caucasian populations.

A German study reported that approximately one in four patients evaluated for suspected obstructive coronary artery disease showed no identifiable culprit lesion. Among those patients who underwent acetylcholine provocation testing, 50% received confirmation of coronary artery vasospasm as the underlying cause of symptoms.

Pathophysiology

The pathogenesis of coronary artery vasospasm remains multifactorial. Originally, the autonomic nervous system was thought to play an important role in the development of coronary artery vasospasm. However, later, endothelial dysfunction, oxidative stress, magnesium deficiency, and respiratory alkalosis were also elucidated as contributing to the pathogenesis. Most recently, genetic mutations that may play a role have also been discovered. Nevertheless, smooth muscle hypertonicity and reactivity in the coronary vasculature play a pivotal role in the development of coronary artery vasospasm.[9][10]

Autonomic Nervous System

An increase in both parasympathetic and sympathetic activity has been found to contribute to coronary artery vasospasm. Coronary artery vasospasm usually occurs at night, when the parasympathetic nervous system is activated. Also, acetylcholine has been shown to induce coronary artery vasospasm, which supports the notion that parasympathetic activity can induce coronary artery vasospasm. However, studies have shown that coronary artery vasospasm at night frequently occurs during rapid eye movement, when vagal tone is reduced and adrenergic activity surges. Furthermore, clinical studies have also shown that elevated catecholamine levels can also induce coronary artery vasospasm. Thus, the autonomic nervous system's relationship with coronary artery vasospasm is complex and still being investigated.

Endothelial Dysfunction

Dysfunctional endothelial nitric oxide synthase and the decreased release of nitric oxide have been associated with the development of coronary artery vasospasm. Acetylcholine, serotonin, and histamine induce endothelium-dependent vasodilatation by releasing nitric oxide from normal endothelium, but they can provoke coronary artery vasospasm in the presence of endothelial dysfunction. However, endothelial dysfunction is not always seen in patients with coronary artery vasospasm. Thus, other factors are also likely associated with the manifestation of coronary artery vasospasm.

Oxidative Stress

Oxidative stress is known to have a detrimental effect on vascular wall health. The reactive oxygen species (ROS) cause inflammation, endothelial damage, and vasoconstriction. Thus, increased levels of ROS lead to vascular dysfunction and remodeling. Smoking has been shown to reduce acetylcholine-induced endothelium-dependent relaxation, suggesting that nitric oxide can be destroyed by ROS. However, the role of this relationship in the development of coronary artery vasospasm is complex, as not all patients with coronary artery vasospasm have endothelial nitric oxide deficiency or dysfunction.

Smooth Muscle Cell Hypercontractility

Shimokawa et al discovered that enhanced myosin light-chain phosphorylation plays a central role in coronary artery vasospasm. They further elucidated that the hydroxyfasudil-sensitive Rho-kinase-mediated pathway may be responsible for the enhanced myosin light-chain phosphorylation. Thus, a Rho-kinase inhibitor can potentially inhibit vasospastic activity. Further studies have identified other pathways that may contribute to coronary artery vasospasm, eg, in K-mutant or SUR2-K knockout mice. Loss of function of K channels has been shown to cause smooth muscle cell hypercontraction in the absence of atherosclerotic disease. These studies have opened pathways for understanding the implications of smooth muscle hypercontractility in the development of coronary artery vasospasm in humans.

Genetics

No direct genetic link has been uncovered to date linking coronary artery vasospasm to genetic polymorphism. However, mutations or polymorphisms in the endothelial nitric oxide synthase and paraoxonase I genes have been observed in patients with coronary artery vasospasm. Other genetic mutations in adrenergic and serotonergic receptors, angiotensin-converting enzyme, and inflammatory cytokines have also been described. However, a direct genetic link has yet to be identified in all cases of coronary artery vasospasm.

Histopathology

Increased inflammation has been associated with coronary artery vasospasm. In coronary artery vasospasm, inflammation may be characterized histologically by infiltration of inflammatory cells, eg, mast cells. Mast cells have been reported at the site of coronary artery vasospasm, in the adventitia, and in the plaque of coronary arteries in patients with this condition.

History and Physical

Clinical History

Coronary artery vasospasm–related chest pain characteristically occurs at rest, most commonly at midnight or during early morning hours, and may be associated with reduced exercise tolerance, particularly in the morning. Pain typically lasts 5 to 15 minutes, with rapid relief after nitrate administration. Patients often describe the pain as crushing, substernal chest discomfort with possible radiation to the jaw or arm. Approximately 20% to 30% of patients presenting with chest pain and evaluated for obstructive coronary artery disease via coronary angiography demonstrate normal coronary arteries; these patients may present with or without symptoms.

Associated symptoms include palpitations, presyncope, syncope, diaphoresis, and occasional nausea. Recurrent episodes with a circadian pattern, along with transient ST-segment elevation on electrocardiography (ECG), serve as important diagnostic clues. Beta-blocker therapy may exacerbate symptoms and worsen clinical presentation.

Physical Examination

Physical examination findings remain generally normal between episodes. During active vasospastic episodes, patients may appear anxious and diaphoretic, with possible transient hypotension or arrhythmias observed hemodynamically. Rarely, transient S4 may be detected during examination.

Evaluation

Clinical history and an electrocardiographic recording during a spontaneous episode are major elements in the clinical diagnosis of vasospastic angina.[8][9][10][11] The international study group on coronary vasomotion disorders, known as COVADIS, developed diagnostic criteria for Prinzmetal angina. Definite coronary artery vasospasm requires all 3 criteria. Suspected coronary artery vasospasm has 2 of the 3 following criteria:

1. Clinical response to nitrates during a spontaneous anginal episode
2. Transient electrocardiographic changes with concern for ischemia during a spontaneous anginal episode, including ST-segment elevation or depression = 0.1 mV or new U waves
3. Evidence of coronary vasospasm during angiography

Electrocardiogram

An ECG should be recorded during the episode. Changes that can be seen include ST-elevation corresponding to the culprit lesion, with ST depression in the contralateral leads. A diagnosis can be made if the patient is given a fast-acting nitrate during the episode and the ECG findings resolve. In some cases, only ST depression can be seen in the contiguous leads. Other ECG findings may include negative T waves in the culprit lesion territory during recovery from ischemia and negative U waves during active spasm.

Noninvasive Testing

Noninvasive tests, eg, stress tests or ambulatory ECG monitoring (Holter), have limited sensitivity. Holter may show episodes of silent ischemia. Rarely, a stress test can induce ischemia. Most of these patients will have a normal stress test or be negative for ischemia. However, a subgroup of patients (10% to 30%) can have exercise-induced spasms with electrocardiographic changes for ischemia that are not specific for vasospastic angina versus fixed coronary obstruction.

Coronary Angiography

Coronary angiography is frequently required to exclude obstructive coronary artery disease. Provocative testing during angiography is the gold standard to diagnose coronary artery vasospasm. Agents used include acetylcholine and ergonovine. Based on COVADIS criteria, a positive test includes all of the following: reproduction of chest pain, ischemic ECG changes, and greater than 90% constriction of coronary arteries on angiography. Furthermore, reduced coronary flow reserve (CFR) or increased index of microvascular resistance (IMR) suggests impaired microvascular function. 

Cardiac Enzymes

Blood can also be checked for cardiac biomarkers, including troponin I or T and creatine kinase. However, these biomarkers are not always elevated in patients with coronary artery vasospasm-induced chest pain.

Treatment / Management

Management Overview

Medical therapy, including comprehensive risk factor modification, serves as the cornerstone of treatment and long-term management for this patient population. Treatment strategies prioritize the reduction of angina episodes and the prevention of complications, eg, myocardial injury and clinically significant arrhythmias.

General measures emphasize lifestyle modification, with smoking cessation representing a critical intervention for reducing episode frequency. Avoidance of agents known to precipitate coronary vasospasm, including cocaine, marijuana, and ephedrine-based products, remains essential.[11][10] Stress reduction and maintenance of adequate sleep also contribute to symptom control, along with avoidance of alcohol use.

Pharmacological Therapy

Pharmacologic therapy primarily relies on calcium antagonists, which serve as first-line agents because of their coronary vasodilatory effects.[12] Calcium channel blockers achieve symptom relief in approximately 90% of patients, and clinical evidence demonstrates improved myocardial infarct-free survival with their use. Long-acting formulations administered at night align with the circadian pattern of vasospasm, which occurs more frequently at midnight and early morning hours. High-dose regimens of agents, eg, diltiazem, amlodipine, nifedipine, or verapamil require individualized titration to balance efficacy and adverse effects. Combination therapy using both dihydropyridine and nondihydropyridine calcium antagonists may benefit patients with suboptimal response to single-agent therapy.

Long-acting nitrates provide additional protection against vasospastic events, although chronic use may result in tolerance. In patients with incomplete response to calcium antagonists, long-acting nitrates may be added, while short-acting sublingual nitrates provide acute symptom relief. Nicorandil, a nitrate and potassium-channel activator, offers adjunctive benefit and serves as second-line therapy.

Avoidance of beta-blockers, particularly those with nonselective adrenoceptor activity, remains important due to potential symptom exacerbation. High-dose aspirin may worsen vasospasm through prostacyclin inhibition and should be avoided, whereas low-dose aspirin may be appropriate in the presence of coexisting coronary artery disease. Additional therapies, eg, guanethidine, clonidine, or cilostazol, have shown benefit in select cases receiving calcium channel antagonists, although evidence remains limited. Fluvastatin may reduce coronary spasm through effects on endothelial nitric oxide availability and vascular smooth muscle function.

Alternative therapies under investigation include fasudil, magnesium, vitamins C and E, iloprost, alpha-receptor blockade, selective serotonin receptor inhibitors, and thromboxane A2 synthetase inhibition.[13][14] However, variability in clinical response and limited evidence preclude their use as standard first-line therapies.

Management in High-Risk Patients

High-risk patients with aborted sudden cardiac death, ventricular arrhythmias, or syncope may require implantable cardioverter-defibrillator placement and intensive vasodilator therapy. The role of implantable cardioverter-defibrillators in coronary artery vasospasm associated with ventricular tachycardia or ventricular fibrillation remains uncertain, although reports describe favorable outcomes in selected survivors of malignant ventricular arrhythmias secondary to vasospasm.[15][16]

Differential Diagnosis

Due to the heterogeneous presentation of coronary artery vasospasm, the condition can initially be mistaken for multiple other cardiac pathologies. Coronary artery vasospasm may present with chest pain, ECG changes, and elevated cardiac biomarkers. All causes of troponin-positive nonobstructive coronary artery disease should be considered, including:

• Coronary causes
  • Coronary artery dissection
  • Coronary plaque rupture or erosion
  • Coronary microvascular dysfunction
  • Coronary artery emboli

• Noncoronary causes
  • Stress cardiomyopathy
  • Myocarditis
  • Sepsis
  • Pulmonary thromboembolism
  • Congenital coagulation abnormalities

Prognosis

In patients without coronary artery stenosis, 1-year survival is up to 99%, and 5-year survival is approximately 94%. Recurrent episodes of angina are usually seen in 4% to 19% of patients. Advanced age and impaired left ventricular function have been identified as factors for poor prognosis in patients who present with acute coronary syndrome due to coronary artery vasospasm. In addition, elevated hs-CRP levels predict a higher risk of death, nonfatal myocardial infarction, and recurrent angina requiring repeat coronary angiography. Multivessel spasm and prior history of cardiac arrest or arrhythmia are other significant poor prognostic factors. However, the prognosis is usually favorable as long as the patients are maintained on calcium channel blockers and risk factors such as smoking are addressed. 

Complications

Complications of coronary artery vasospasm include:

• Life-threatening arrhythmias
• Myocardial ischemia
• Sudden cardiac death
• Recurrent angina
• Left ventricular dysfunction