What is CUS (Cardiac Ultrasound Study)?

Focused Cardiac Ultrasound (FoCUS)

FoCUS is a point-of-care cardiac ultrasound examination performed according to a standardized but restricted scanning protocol to add information to the physical examination by clinicians who may not be fully trained in comprehensive echocardiography but are appropriately trained in FoCUS. 1

Definition and Purpose

• FoCUS is designed to detect a limited number of critical cardiac conditions at the point of care, providing qualitative assessments typically reported as "absent/present" or "yes/no" 1
• It differs from comprehensive echocardiography, which is a full investigation of cardiac morphology and function performed by fully trained operators using fully equipped echocardiographic machines 1
• FoCUS is typically used by non-cardiologists who have undergone focused training, though it can also be performed by fully trained cardiologists in emergency settings 1

Clinical Applications

• FoCUS is primarily used in emergency and critical care settings to rapidly assess patients with:

  • Circulatory compromise/shock 1
  • Cardiac arrest 1
  • Chest pain 1
  • Chest/cardiac trauma 1
  • Respiratory compromise 1, 2

• The Society of Critical Care Medicine suggests using Critical Care Ultrasonography (CCUS), which includes FoCUS, in acutely ill adults to improve clinical outcomes 1

Evidence-Based Targets of FoCUS

FoCUS is specifically designed to assess:

• Global left ventricular systolic function and size 1
• Global right ventricular systolic function and size 1
• Pericardial effusion 1
• Intravascular volume assessment 1

Clinical Benefits

• FoCUS may reduce time to correct diagnosis (by approximately 1.23 hours) 1
• It may reduce time to correct treatment (by approximately 20.67 hours) 1
• It may reduce duration of mechanical ventilation (by approximately 3.26 days) 1
• Studies show FoCUS findings can beneficially modify patient management 1
• When used for targeted volume management, FoCUS may reduce mortality compared to usual care 1

Limitations and Risks

• Being an inherently limited approach, FoCUS carries risks of:
  • Overlooking important abnormalities 1
  • False readings of incomplete datasets 1
  • Error rates higher than comprehensive echocardiography, especially when performed by operators not fully trained in echocardiography 1
• Failure to appreciate these limitations may lead to serious misinterpretation with potentially devastating clinical consequences 1

Equipment

• While any echocardiographic machine can be used, smaller hand-held and pocket-size imaging devices are more frequently used for FoCUS 1
• Current pocket-size devices offer diagnostic-quality two-dimensional and some color Doppler cardiac imaging in real-time 1
• Image quality is generally inferior compared to high-end systems, which is particularly important in difficult patients 1

Quality Control and Follow-up

• All patients with cardiovascular abnormalities detected by FoCUS should be referred for comprehensive echocardiographic examination as soon as appropriate 1
• FoCUS examinations should be recorded, permanently stored, and reports issued in a timely manner 1
• Continual supervision and quality control of FoCUS examinations are essential, preferably by accredited echocardiographic laboratories 1

Training Requirements

• Specific training in FoCUS is essential to understand its capabilities and limitations 1
• The European Association of Cardiovascular Imaging recommends incorporating theoretical knowledge of emergency cardiovascular conditions in FoCUS training programs 1
• Recognition of the limitations of FoCUS must be incorporated in any training protocol 1

FoCUS represents an important tool in modern clinical practice, but must be used with clear understanding of its scope and limitations to ensure patient safety and optimal outcomes.