Ultrasound Adult Echocardiography Assessment, Protocols, and Interpretation

Anatomy and Physiology

Transthoracic Echocardiography views and anatomy:

Parasternal Long-axis View 

• Structures
  • Chambers identified in this view the left atrium left ventricle, left ventricle outflow tract, and aorta
  • Valves identified in this view: mitral valve and aortic valve 
    • This view helps identify regurgitant and stenotic jets of mitral and aortic valves.[3] See Image. Parasternal Long Axis View on Transthoracic Echocardiography.

Parasternal Short-axis View 

• Structures 
  • Chambers identified in this view: left atrium, right atrium, right ventricle outflow tract, main pulmonary artery
  • Valves identified in this view: aortic valve, pulmonary valve, tricuspid valve
    • This view helps identify the tricuspid and pulmonary valve disease and patent ductus arteriosus.

Apical 4 Chamber View

• Structures
  • Chambers identified in this view: left atrium, right atrium, left ventricle, and right ventricle
  • Valves identified in this view: mitral and tricuspid valve 
    • This view helps identify the wall motion abnormalities of the inferior septal wall and anterolateral wall of the left ventricle, mitral, and tricuspid valve disease. See Image. Apical Four-Chamber View on Transthoracic Echocardiography.

Apical  5 Chamber View

• Structures 
  • Chambers identified in this view: left atrium, right atrium, left ventricle, left ventricle outflow tract, right ventricle, and aorta
  • Valves identified in this view: mitral valve, tricuspid valve, and aortic valve
    • This view provides additional information on the Left ventricle outflow tract, aortic valve, and aortic root compared to the 4-chamber view.

Apical 2 Chamber View 

• Structures 
  • Chambers identified in this view: left atrium and left ventricle
  • Valves identified in this view: mitral valve 
    • This view helps identify the wall motion abnormalities of the inferior wall and anterior wall of the left ventricle and mitral valve disease. See Image. Apical Two-Chamber View on Transthoracic Echocardiography.

Apical Parasternal Long-axis View 

• Structures
  • Chambers identified in this view: left atrium, left ventricle, left ventricle outflow tract, and aorta
  • Valves identified in this view: mitral valve and aortic valve 
    • This view helps identify the wall motion abnormalities of the anterior septal wall and the inferolateral wall of the left ventricle. In this view, mitral valve and aortic valve disease are identifiable. See Image. Apical Parasternal Long-Axis View on Transthoracic Echocardiography.

Subcostal Coronal View 

• Structures 
  • Chambers identified in this view: left atrium, right atrium, left ventricle, and right ventricle
  • Valves identified in this view: mitral and tricuspid valve 
    • This view helps diagnose interatrial septal defect, pericardial effusion, and cardiac tamponade.

Subcostal Saggital view

• Structures 
  • Chambers identified in this view: right atrium, inferior vena cava, hepatic vein, and descending aorta
    • This view helps in assessing the fluid status of the patient.

Suprasternal Noch View

• Structures 
  • Chambers identified in this view: left atrium, aortic arch, brachiocephalic artery, left common carotid artery, left subclavian artery, and right pulmonary artery
    • This view helps diagnose aorta diseases such as aortic dissection and coarctation of the aorta. In this view, a congenital heart defect, patent ductus arteriosus, can be identified.[4] 

Indications

Appropriate Use And Indication Criteria for Echocardiography According to ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/ SCCT/SCMR 2011

1. Symptoms related to cardiac diseases such as chest pain, shortness of breath, syncope, palpitations, transient ischemic attack, stroke, and peripheral embolic event
2. Previous diagnostic tests such as cardiac enzymes, electrocardiogram, and chest X-ray indicating cardiac disease
3. Premature ventricular contraction (frequent or exercise-induced)
4. Arrhythmias such as atrial fibrillation, atrioventricular node re-entry tachycardia, and ventricular tachycardia (sustained or non-sustained)
5. Evaluation of right ventricular function (fractional area change, tricuspid annular plane systolic excursion, right index of myocardial performance, and pulmonary artery pressure in a patient with suspected pulmonary artery hypertension
6. Routine follow-up of patients as surveillance (>1 year) for diagnosed pulmonary artery hypertension patients without a change in symptoms or physical examination
7. To guide management in patients diagnosed with pulmonary artery hypertension and change in cardiac symptoms or physical examination
8. Patient in shock with an uncertain or suspected cardiac cause
9. For evaluation of a patient with a suspicion of myocardial infarction, either with chest pain or diagnostic tests such as cardiac enzymes and electrocardiogram indicating myocardial infarction 
10. For diagnosis of valvular heart disease
11. To guide management in patients diagnosed with valvular heart disease and change in cardiac symptoms or physical examination
12. Patients with suspicion of hypertensive heart disease, prosthetic valve dysfunction,  infective endocarditis, heart failure, congenital heart disease, cardiac mass, pericardial disease, aortic aneurysm, aortic dissection, or cardiovascular source of embolus [5][6] 

Indication for Transesophageal Echocardiography

1. Transthoracic echo is nondiagnostic due to the patient's characteristics
2. To guide percutaneous noncoronary cardiac interventions such as closure device placement, radiofrequency ablation, and percutaneous valve procedures
3. To rule out cardiovascular sources such as embolus in patients with no other non-cardiac cause
4. To help decide cardioversion, anticoagulation, and ablation in atrial flutter or atrial fibrillation
5. To diagnose infective endocarditis in patients with moderate-high pretest probability

Indication for Stress Echocardiography

1. Patients with intermediate and high pre-test probability for coronary artery disease
2. Patients with a possible acute coronary syndrome (electrocardiogram: no ischemic changes or with left bundle branch block or electronically paced ventricular rhythm, low-risk thrombolysis in myocardial infarction (TIMI) score with either borderline or minimally elevated troponin, high-risk TIMI score with negative troponin)

Contraindications

Appropriate Use Criteria for Echocardiography, Inappropriate Transthoracic Echocardiography Indications According to ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011   

• Patients with asymptomatic sinus bradycardia
• Patients with infrequent atrial premature contractions or ventricular premature contractions
• Patients with presyncope and no other evidence of cardiac disease
• Evaluation of left ventricle function for pre-operative screening in patients without symptoms or signs of cardiac disease
• Routine follow-up of patients as surveillance (<1 year) for diagnosed pulmonary artery hypertension patients without a change in symptoms or physical examination
• Routine follow-up of patients as surveillance in patients with a previous history of pulmonary embolism with normal right ventricular function and pulmonary artery systolic pressure

Absolute Contraindications Of Transesophageal Echocardiography

• History of esophageal stricture, perforation, tumor, laceration, and diverticulum
• History of upper gastrointestinal bleeding 
• Severe atlantoaxial joint disorder
• Conditions that prevent neck flexion 

Inappropriate Transesophageal Echocardiography Indications

• Routine use of transesophageal echocardiography in patients in whom decisions regarding diagnosis and management are already resolved by transthoracic echocardiography
• To diagnose infective endocarditis in patients with low pretest probability
• To rule out cardiovascular sources such as embolus in patients with an obvious cardiac cause
• Patients with atrial fibrillation or atrial flutter in whom the decision to anticoagulant already made  

Conditions In Which Stress Echocardiography Are Inappropriate

•  Patients with low pre-test probability for coronary artery disease
•  Patients with definite acute coronary syndrome

Equipment

Equipment Requirement for Transthoracic Echocardiography

• Echocardiography machine
• Transducer
• Contrast agent [7] 

Equipment Requirement for Transesophageal Echocardiography

• Echocardiography machine
• Transesophageal transducer
• Medication for sedation 
• Transesophageal bite block
• Intravenous cannula for medications 
• For the bubble study: agitated saline, 3-way stop cock, 2 10 ml syringes, and an extension tube connector
• Gel to lubricate transesophageal probe
• Topic anesthetics such as lidocaine to numb the pharynx [8] 

Equipment Requirement for Stress Echocardiography 

• Echocardiography machine
• Exercise stress test machine
• Cardiac monitor to look for vitals 
• Medications (such as dobutamine and atropine) to give stress in patients who can not perform an exercise stress test and medications (such as beta-blockers and calcium channel blockers) to reverse the effect of dobutamine and atropine

Personnel

Personnel required to perform and interpret an echocardiogram include:

• Cardiologist 
• Echocardiogram technician

Technique or Treatment

For transthoracic echocardiography, the patient should lie in the left lateral position.

Complications

The complications from transthoracic echocardiography and stress echocardiography are infrequent.

Transesophageal Echocardiography

1. Gastrointestinal bleeding
2. Esophageal perforation
3. Pharyngeal hematoma
4. Aspiration
5. Laryngospasm
6. Arrhythmia
7. Toxic methemoglobinemia [9][10] 

Stress Echocardiography

1. Myocardial infarction
2. Arrhythmia
3. Coronary spasm
4. Hypertension or hypotension secondary to medication [11][12] 

Clinical Significance

Transthoracic echocardiography: a non-invasive, low-cost, widely available, first-line diagnostic test to evaluate cardiac disease and function. It not only helps to diagnose cardiac disease but also provides useful information to guide therapy.

Transesophageal echocardiography: an invasive test in which transthoracic echo is inconclusive or needs further information on infectious endocarditis. The esophagus's proximity to the heart and absence of intervening structures such as the lung make the Transesophageal echo ideal for examining various important structures.

Stress echocardiography: including imaging in routine stress testing increases the sensitivity and specificity of the test in diagnosing coronary artery disease. Stress echocardiography post-myocardial infarction helps in risk stratification, location, and extent of coronary artery disease. Stress echocardiography can also be used to risk-stratify patients before non-cardiac surgery, as resting echo does not provide essential prognostic information.

Enhancing Healthcare Team Outcomes

To perform echocardiography requires an interprofessional team that includes a cardiologist and an echo technician. It is vital to take a proper history and perform a pre-procedure physical examination to determine the indication of the procedure. Communication between echo technicians and the cardiologist is essential, especially when there is a discrepancy in results.