Coronary Ectasia

Etiology

The etiology of coronary artery ectasia can be enigmatic. Atherosclerosis lays claim to the principal etiologic cause responsible for greater than 50% of cases in adults, while Kawasaki disease is the most common cause in children and young adults.[3] The histology of atherosclerosis and ectasia is comparable. Coronary artery ectasia is rarely genetic. Acquired etiologies include atherosclerosis, Kawasaki disease, mycotic or septic emboli, Marfan syndrome, arteritis from polyarteritis nodosa, Takayasu disease, or systemic lupus erythematosus. Coronary artery ectasia secondary to iatrogenic causes includes secondary to percutaneous transluminal coronary angioplasty, stents, and directional coronary atherectomy. 

Risk Factors

Some of the risk factors for coronary ectasia include:

• Hypertension
• Smoking
• Use of illicit drugs like cocaine

Epidemiology

The incidence varies between 0.3% and 4.9%. The Coronary Artery SUrgery Study registry found coronary artery ectasia in 4.9% of coronary angiograms. Coronary artery ectasia is classified as small (vessel size under 5 mm), medium (vessels size 5 to 8 mm), and giant (vessel size over 8 mm). Based on location most common location is in the right coronary artery (68%), proximal left anterior descending (60%), and left circumflex (50%).[4] Based on shape, coronary artery ectasia can be divided into "saccular," when the transverse diameter is larger than the longitudinal diameter, or "fusiform," when the longitudinal diameter is larger than the transverse diameter.

Pathophysiology

The exact pathophysiology of coronary artery ectasia is unknown. CAE is an anatomical variant or a clinical constellation of coronary artery disease because it may present with myocardial ischemia or coronary syndrome. The mechanism of luminal dilation in some atherosclerotic vessels is ambiguous; atherosclerosis typically causes vessel lumen narrowing. Due to the arterial remodeling, there is an expansion of the blood vessel's medial and external elastic membrane. This proposed methodology of arterial remodeling may be operative in the case of coronary artery ectasia. Intravascular ultrasound reveals that arterial remodeling can be bidirectional depending upon the expansion or contraction of the external elastic membrane. Coronary artery ectasia appears to be exaggerated expansive remodeling of the external elastic membrane resulting in luminal expansion.

Enzymatic degradation of the extracellular matrix by matrix metalloproteinases and other lytic enzymes and thinning of the tunica media associated with severe chronic inflammation is considered the principal pathogenesis of expansive remodeling.[5] CAE is also related to apical hypertrophic cardiomyopathy with high wall tension. In addition to that, iatrogenic mechanisms, eg, percutaneous coronary interventions, including balloon angioplasty, stent placement, and atherectomy, can lead to the formation of aneurysms or ectasias. The mechanism seems to be the injury of the media of the blood vessel.[6]

Histopathology

Histology usually shows it thickened fibrotic intima with lipid deposition. The internal elastic laminal layer usually suffers disruption, leading to reduced medial elastic tissue. This loss of elastic tissue is the primary cause along with chronic vascular inflammation leading to ectasia.

History and Physical

The symptoms of coronary artery ectasia may be associated with concomitant coronary disease, Kawasaki disease, or connective tissue disease. Most patients are asymptomatic and may present with angina post-stress tests and acute coronary syndrome. Diminished coronary flow speed or stagnancy of blood flow may cause exercise-induced angina without coexistent stenotic coronary artery disease. Formation of intracoronary thrombus or dissipation leading to distal emboli may be the trigger of acute coronary syndrome, which is hastened by stagnant flow in the ecstatic coronary segment. The hypothesis is that coronary artery ectasia is predisposed to vasospasm, which may elicit angina or acute coronary syndrome. In people younger than 50, CAE should raise concern for connective tissue disorders and vasculitides.[7][8]

Evaluation

Coronary angiography is the gold standard in diagnosing coronary artery ectasia. Intravascular ultrasound is critical for evaluating luminal characteristics and pathologies.[6] Distortions of flow and washout are common in CAE and are related to the severity of ectasia. Signs of stagnant flow include delayed antegrade contrast filling, segmental backflow, and stasis in the ectatic coronary segment.[5] Other investigative techniques include magnetic resonance angiography (MRA) and coronary computed tomography angiography. For the follow-up of patients, MRA is the preferred modality.

Treatment / Management

Management of coronary artery ectasia is fraught with uncertainty because the rarity of CAE prevents large randomized trials comparing different treatment approaches. When coronary artery disease coexists, intense primary and secondary risk factor modifications are mandatory. Management of isolated coronary artery ectasia in a case with angina or myocardial ischemia includes statins and anti-ischemic medications. Acute coronary syndromes associated with CAE may require thrombolysis, heparin administration, and glycoprotein IIb/IIIa receptor inhibitors. Thrombus aspiration may be necessary during primary percutaneous coronary intervention.

Percutaneous and surgical interventions are often beneficial for patients with CAE and stenotic lesions where angina persists despite maximal medical therapy. Optimal stent sizing is essential to prevent misplacement and embolization of stents. Many authors recommend chronic anticoagulation; however, no randomized trial demonstrates its benefit in CAE. The anticipated benefit must counterbalance the risk of hemorrhage.[9][10] Surgery is rarely done but is sometimes a necessity in patients who have recurring complications. The surgery involves ligation of the proximal and distal segments of the ectatic vessel and replacing it with a bypass graft. There should be no attempt to repair the ectatic vessel as the results are poor.(A1)

Differential Diagnosis

The differential diagnoses for coronary ectasia include the following:

• Atherosclerosis
• Bacterial syphilis
• Behcet disease
• Ehler-Danlos syndrome
• Fibromuscular dysplasia
• Giant cell arteritis
• Kawasaki disease
• Marfan syndrome
• Mycotic aneurysm
• Septic emboli

Prognosis

The prognosis for coronary artery ectasia is directly related to the severity of concomitant coronary artery disease. Coronary artery ectasia with underlying coronary artery disease is a dangerous combination with an increased potential for adverse cardiac events. Isolated CAE still carries the risk of myocardial ischemia and infarction. Type 1 and type CAE demonstrate a higher risk than type 3 and type 4 CAE. No reported data shows a relationship between the diameter of an artery and the outcome.[11]

Complications

The complications that can manifest with coronary ectasia are as follows:

• Thrombus leading to myocardial infarction 
• Acute coronary syndromes
• Fistula formation in the cardiac chambers
• Thrombosis
• Distal embolization
• Complications after stenting include:
  • Stent misplacement
  • Embolization of stents
  • Stent thrombosis
  • Restenosis