Spontaneous Right Coronary Artery Dissection

Abstract

Spontaneous coronary artery dissection is a rather rare cause of myocardial infarction, chest pain, and sudden death. Since the condition was first described in 1931, fewer than 200 cases have been reported in the medical literature. There are currently no known direct causes of this condition, although some correlations have been noted. Many patients are women in the peripartum period or of childbearing age, with few or no risk factors for coronary artery disease. Other associations include contraceptive use and connective-tissue disorders, Ehlers-Danlos and Marfan syndromes, and polyarteritis nodosa. Most of the reported dissections have occurred in the left anterior descending coronary artery. Herein, we report the case of a 36-year-old woman who presented at our institution with an acute ST-elevation myocardial infarction secondary to a spontaneous dissection of the right coronary artery. Thrombectomy and stenting resolved the occlusion of the artery, and the patient was discharged from the hospital on medical therapy. We discuss the pathophysiology, presentation, and treatment of this rare and often fatal condition.

Spontaneous coronary artery dissection is a rare cause of myocardial infarction, chest pain, and sudden death. No direct causes of this condition have been identified, although some correlations have been noted. Many patients are women in the peripartum period or of childbearing age, with few or no risk factors for coronary artery disease.^1,2 Contraceptive use and connective-tissue disorders, Ehlers-Danlos and Marfan syndromes, and polyarteritis nodosa have been associated with spontaneous dissection.^1,3 Most reported dissections have occurred in the left anterior descending coronary artery (LAD). Herein, we report the case of a woman who was diagnosed with spontaneous dissection of the right coronary artery (RCA).

Case Report

In November 2007, a 36-year-old woman was emergently brought to our hospital with substernal, pressure-like, nonradiating chest pain of medium intensity, and dizziness, diaphoresis, and mild shortness of breath. Upon admission, she was short of breath and uncomfortable. She had no history of alcohol, tobacco, or recreational drug use. Her medical history included well-controlled hypertension, gestational diabetes mellitus, and resolved postpartum cardiomyopathy during the second of her 3 pregnancies.

The patient was hemodynamically stable, afebrile, and tachypneic. On examination, all organ systems were normal. Cardiovascular examination revealed a normal S₁ and S₂, regular heart rate and rhythm, and no murmurs, rubs, or gallops. An electrocardiogram revealed sinus rhythm, normal axis, 1st-degree atrioventricular block, and 3- to 4-mm ST-segment elevations in leads II, III, and aVF. The patient was given 650 mg of aspirin and 300 mg of clopidogrel and was started on an intravenous heparin drip before being sent for cardiac catheterization.

On diagnostic coronary angiography, a dissection was found at the ostium of the RCA, resulting in occlusion beginning at that site (Fig. 1). The LAD, left main, and left circumflex coronary arteries were normal, as were aortic and mitral valvular function. Study of the ventricles revealed mild diaphragmatic and moderate posterobasal left ventricular hypokinesis with a left ventricular ejection fraction of 0.54. Thrombectomy was performed on the lesion in the proximal RCA. Subsequently, 5 stents were placed, and normal blood flow was restored with no residual stenosis (Fig. 2). After catheterization, the patient was sent to the coronary care unit in stable condition for observation.

Fig. 1 Coronary angiogram shows the occluded right coronary artery.

Fig. 2 Coronary angiogram shows the right coronary artery after thrombectomy and stenting.

The patient was initially hypotensive with systolic blood pressures in the 80-mmHg range; the hypotension resolved after bolus injections of normal saline fluid. Laboratory studies revealed a cardiac troponin T level that peaked at 6.82 ng/mL on the day after catheterization. The peak creatine kinase level was 2,127 U/L and the creatine kinase–MB fraction was 15.7%. Results of a complete blood count and of blood chemistry were within normal limits. A fasting lipid panel revealed a total cholesterol level of 154 mg/dL, a high-density-lipoprotein cholesterol level of 39 mg/dL, a low-density-lipoprotein cholesterol level of 102 mg/dL, and triglycerides of 64 mg/dL. The patient recovered without complications and was discharged from the hospital 2 days later with stable vital signs. She was asymptomatic, and with cardiac enzyme levels trending downward. She was instructed to take aspirin, clopidogrel, and simvastatin. Low-dose angiotensin-converting enzyme inhibitor and β-blocker therapy were added during outpatient follow-up. At the patient's 1-year follow-up appointment, she had stable vital signs and no chest pain.

Discussion

Spontaneous coronary artery dissection was first described in 1931,⁴ and fewer than 200 cases have been reported in the medical literature (Table I).^5–12 Many cases of spontaneous coronary artery dissection occur in asymptomatic women with few or no risk factors for coronary artery disease.¹³ To be classified as spontaneous, a dissection must occur in the absence of trauma, previous surgery or catheterization, or extension of an aortic dissection.

TABLE I. Incidence and Distribution of Spontaneous Coronary Artery Dissection*

The pathogenesis of spontaneous coronary artery dissection is not yet fully understood.² The condition occurs when blood collects within the media of the coronary artery or between the media and external elastic lamina, causing compression of the true lumen of the artery.¹ The initial event leading to dissection is not clear, and no single factor has been found to be causative.^1,14 Many of the proposed mechanisms pertain to changes in vascular wall properties that lead to weakening of the media and connective tissue. These include changes in smooth-muscle-cell metabolism, the effect of proteases released from eosinophilic infiltrates, and pregnancy-related changes in connective tissue.^1,2,15 Of note, our patient presented with spontaneous dissection and had a history of peripartum cardiomyopathy, both of which may be related through eosinophilic infiltrates¹⁶; however, it is unknown whether this was related to her presenting condition. Other, rarer causes include intense physical exercise and cocaine abuse.¹³ Most patients do not have risk factors for coronary artery disease.¹⁷

In women, 80% of reported spontaneous coronary artery dissections have occurred in the LAD, but our patient's lesion was in the RCA. Postpartum cases of dissection have been reported; however, our patient had borne her last child more than 2 years before the hospital admission for dissection. Coronary artery dissection can occur as a physical extension of an aortic dissection, especially in the presence of cystic medial necrosis associated with connective-tissue disorders such as Marfan syndrome.^15,18 Our patient exhibited no evidence of connective-tissue disease and had no known history of it.

There is no consensus in regard to the management of spontaneous coronary artery dissection, due to the condition's rarity. Numerous cases have been reported after sudden cardiac deaths.² In other instances, conservative management has yielded positive results. As in our patient, early presentation at a medical center with subsequent catheterization and stenting has proved to be a satisfactory intervention for this rare, life-threatening condition.