Coronary Cameral Fistula

Etiology

The causes of coronary cameral fistulas include:

• Abnormal embryogenesis
  • This is the most common cause
•  Trauma
  • Stab injury or gunshot 
• Invasive procedures
  • Coronary angiography, pacemaker implantation, or endomyocardial biopsy
• Cardiac surgery
  • Septal myomectomy [6]

Epidemiology

Coronary cameral fistulas are rare, occurring in less than 1% of the population and observed in 0.1% to 0.2% of coronary angiographic studies.[5][7] They account for 0.2% to 0.4% of congenital heart anomalies. Approximately half of the coronary vasculature anomalies in children are coronary artery fistulas. Coronary cameral fistulas can be diagnosed at any age. However, it is often identified in early childhood when an asymptomatic child or a child with heart failure symptoms presents with a heart murmur. There is no gender or race predisposition for this condition.

History and Physical

History

The clinical symptoms of a coronary cameral fistula depend on the size of the shunt. Most fistulas are asymptomatic, especially if they are small and do not compromise coronary blood flow. However, myocardial ischemia distal to the fistula can occur, known as the coronary artery steal phenomenon, leading to angina that is particularly noticeable during increased myocardial oxygen demand, such as infant feeding or adult exercise. In infants, angina manifests as diaphoresis, irritability, tachycardia, and tachypnea, whereas adults experience chest pain.[8] Coronary cameral fistulas may also present with heart failure symptoms. Infants with heart failure show signs of fatigue, tachypnea, excessive sweating during feeding, and failure to thrive. Older adults with heart failure can present with complaints of dyspnea, palpitations, fatigue, orthopnea, paroxysmal nocturnal dyspnea, and lower limb swelling.

Physical Examination

Clinical examination findings in patients with coronary cameral fistula include:

• Collapsing pulse
• Wide pulse pressure
• Diffuse apex beat
• Palpable third heart sound (S3)
• A loud, continuous murmur on auscultation that peaks in mid-to-late diastole is heard best at the mid-to-lower sternal border, depending on the site of the fistula's drainage.
• Signs of heart failure
  • Elevated jugular venous pressure
  • S3 gallop, crepitations on auscultation of the lung bases
  • Hepatomegaly
  • Ascites
  • Pitting edema of lower limbs

Evaluation

When the history and physical examination findings suggest a coronary cameral fistula, the diagnosis can be established with the help of the following investigations:

• Laboratory tests
  • Cardiac enzymes may be elevated in patients with coronary cameral fistulas.
  • B-type natriuretic peptide may also be elevated, especially in patients with heart failure.

• Chest radiograph
  • This technique is typically normal; however, chamber enlargement may be observed with a large fistula.
  • Signs of pulmonary congestion or interstitial edema can be present in patients with heart failure.

•  Electrocardiogram
  • This technique is typically normal; however, evidence of ischemia or chamber enlargement can be observed with large shunts.

•  Echocardiography
  • In children, transthoracic 2-dimensional (2D) and color Doppler echocardiography can help diagnose coronary cameral fistula.
  • In adults, transesophageal 2D echocardiography is more sensitive in detecting the fistula.
  • In a study conducted in Italy, color Doppler transesophageal echocardiography allowed diagnosis and precise localization of coronary artery fistulas in 21 patients with angiographically confirmed coronary artery fistula.[9] 
  • Echocardiography can also help detect myocardial ischemia, which manifests as regional or global wall motion abnormalities.

• Computed Tomography scan
  • Coronary cameral fistulas can be detected noninvasively using a 64-slice multidetector computed tomography scanner, which provides high-quality 3-dimensional images of the distal coronary artery and side branches.
  • A study published in 2014 by Lim et al concluded that computed tomography angiography was a useful modality for detecting coronary artery fistulas noninvasively. Moreover, coronary artery fistulas were detected in 0.9% of the study subjects, a percentage higher compared to the generally reported prevalence as detected by coronary angiography.[10][11]

• Magnetic resonance imaging
  • This technique can be used to determine the exact origin and termination of the fistula.

• Cardiac catheterization with coronary angiography
  • These are the tests of choice for diagnosing coronary cameral fistula.
  • The exact size of the fistula can be determined by its anatomical characteristics, such as site of origin, course, site of insertion, and coronary angiography.
  • This test also provides information on the hemodynamic significance of the fistula.

• Nuclear imaging
  • This technique is helpful before and after operative repair to detect regions of myocardial ischemia.[12]

Treatment / Management

The management of coronary cameral fistulas depends on several factors, including the origin of the fistula, such as proximal versus distal; fistula size; and fistula anatomy. In addition, management considerations include patient's age; symptoms; the presence of complications, such as heart failure, angina, rupture, or endocarditis; and the existence of other indications for an invasive procedure.

According to the American College of Cardiology (ACC)/American Heart Association (AHA) 2008 guidelines for treating adults with congenital heart disease, the class 1 recommendations for the management of artery fistulas are as follows:

• In patients with a continuous murmur, echocardiography, computed tomography, or magnetic resonance imaging should be used to determine the exact origin and termination of the fistula.
• Regardless of symptoms, a large fistula should be closed percutaneously or surgically after the exact anatomy of the fistula is determined.
• Small-to-moderate–sized fistulas with complications such as ischemia, arrhythmia, ventricular dysfunction, or endarteritis should be closed either percutaneously or surgically after determining the exact anatomy of the fistula.[13]
(A1)

The updated ACC/AHA 2018 guidelines for the management of adults with congenital heart disease make the following statements regarding coronary artery fistulas:

• A coronary artery fistula is an abnormal communication between a coronary artery and another cardiovascular structure, including a cardiac chamber, coronary sinus, superior vena cava, or pulmonary artery. The incidence of coronary artery fistulas is 0.1% to 0.2% in all patients undergoing coronary angiography. Fistulous communications may be congenital or acquired. Specific management strategies have been controversial, including surgical repair or catheter embolization. In a series of 46 patients treated with surgery, predominant preoperative symptoms included angina and heart failure. Notably, postoperative myocardial infarction occurred in 11% because of low flow in the dilated coronary artery proximal to fistula closure. Late survival was also significantly reduced compared to an age-matched population.
• The presence of coronary artery fistula(s) requires review by a knowledgeable team that may include congenital or noncongenital cardiologists and surgeons to determine the role of medical therapy and percutaneous or surgical closure.[14]
(A1)

Small coronary cameral fistulas are typically managed through close echocardiographic or angiographic monitoring to observe any potential enlargement of feeding vessels over time. These fistulas often have a benign course, are typically asymptomatic, and may even close spontaneously.[8] Conversely, large fistulas necessitate closure, which can be achieved through transcatheter embolization or surgical intervention. The choice of approach depends on the expertise of the healthcare team managing the patient, with surgical closure preferred for large fistulas, those with multiple openings, aneurysmal dilation, or complex anatomical features unsuitable for catheterization.[15][16](B3)

Moderate-to-large fistulas without symptoms are managed based on their location. Closure, through transcatheter or surgical, is recommended for a proximal fistula. Antiplatelet therapy should be initiated after closure and continued for at least 1 year. For distal fistulas, management options include indefinite observation with antiplatelet therapy or closure followed by 1 year of antiplatelet therapy.

Although closure is advised for moderate-to-severe shunting due to potential long-term complications, debates continue regarding asymptomatic cases. Surgical closure has demonstrated effective outcomes, but catheter-based methods offer alternatives with high closure rates, minimal morbidity, and mortality. However, transcatheter closure may not be suitable for certain patient groups, particularly those with large fistulas exhibiting high-flow shunts, multiple communications and terminations, aneurysmal formation, or requiring simultaneous coronary bypass or valve surgery. Surgical complications may include myocardial infarction, arrhythmia, transient ischemic changes, and stroke.[17][18]

Prophylactic antibiotics are generally unnecessary for isolated coronary cameral fistulas but should be considered for patients with coexisting cyanotic congenital heart disease before procedures likely to cause bacteremia.[19][20](A1)

Differential Diagnosis

The differential diagnosis of coronary cameral fistula sincludes the following:

• Coronary arteriovenous malformation
• Pulmonary arteriovenous malformation
• Intrathoracic systemic fistula
• Congenital systemic fistulas to the pulmonary veins
• Ruptured aneurysm of sinus of Valsalva
• Vasculitides, such as Takayasu arteritis or Kawasaki disease

Prognosis

Patients with a coronary cameral fistula typically have an average life expectancy. Studies indicate favorable prognoses with both transcatheter and surgical management approaches. The incidence of requiring additional surgery due to recurrent disease is low, affecting only about 4% of patients.

Complications

Common complications associated with coronary cameral fistula include:

• Cardiac ischemia
• Congestive heart failure
• Cardiac arrhythmia
• Infective endocarditis
• Rupture of coronary cameral fistula [6]

Complications related to the management of coronary cameral fistula (transcatheter embolization versus surgical closure) are as follows:

• Transcatheter embolization
  • Coronary artery spasm
  • Ventricular arrhythmia
  • Coronary artery perforation or dissection
  • Cardiac ischemia from coronary artery thrombosis or improper positioning of occlusive devices
• Surgical closure
  • Cardiac ischemia or myocardial infarction
  • Recurrence of coronary cameral fistula [5]