Focused Cardiac Ultrasound (FoCUS) in the ICU: Essential Views and Interpretation

Focused Cardiac Ultrasound (FoCUS) is a simplified, goal-directed point-of-care ultrasound (POCUS) examination performed by ICU clinicians. Unlike a comprehensive echocardiogram, FoCUS is designed to answer specific clinical questions: Is there a tamponade? Is the LV failing? Is the patient fluid-responsive?

1. The 5 Essential Views

A standard FoCUS exam consists of five primary views. Each provides a unique “slice” of the heart to evaluate function and anatomy.

View	Probe Position	Key Structures Visible	Primary Purpose
Parasternal Long Axis (PLAX)	3rd–4th intercostal space (ICS), left of sternum. Marker to R shoulder.	LV, LA, RV (outflow), Aortic & Mitral valves.	Global LV function, aortic root size, pericardial effusion.
Parasternal Short Axis (PSAX)	Rotate probe 90° clockwise from PLAX. Marker to L shoulder.	LV (cross-section), RV.	Regional wall motion, LV “doughnut” shape, RV pressure (D-sign).
Apical 4-Chamber (A4C)	Point of Maximal Impulse (PMI) / 5th ICS. Marker to L axilla.	LV, RV, LA, RA, Septum.	Comparing RV vs. LV size, assessing contractility and valvular flow.
Subcostal (Subxiphoid)	Below xiphoid process, angled toward L shoulder.	All 4 chambers (through the liver).	Best view for pericardial effusion and tamponade.
Inferior Vena Cava (IVC)	Subcostal, rotate 90° clockwise. Marker toward head.	IVC entering the Right Atrium.	Assessing volume status and fluid responsiveness.

---

2. Interpretation: Key Clinical Findings

In the ICU, interpretation focuses on “binary” or qualitative assessments (e.g., “Yes” vs. “No”).

Left Ventricular (LV) Function

• Hyperdynamic: LV walls almost touch in systole (“kissing papillary muscles”). Often seen in hypovolemia or distributive shock (sepsis).
• Severely Depressed: Minimal wall thickening or inward movement. Suggests cardiogenic shock or acute-on-chronic heart failure.

Right Ventricular (RV) Strain

• RV Dilation: Normally, the RV should be < 2/3 the size of the LV. If the RV is larger than the LV, suspect Pulmonary Embolism (PE) or acute RV failure.
• The “D-Sign”: In PSAX, if the interventricular septum is flattened (making the LV look like a “D” instead of a “O”), it indicates RV pressure/volume overload.

Pericardial Effusion & Tamponade

• Effusion: Anechoic (black) space around the heart.
• Tamponade Signs: Right atrial collapse in diastole or right ventricular collapse in early diastole. This is a medical emergency requiring immediate intervention.

Volume Status (IVC Assessment)

• Plethoric IVC: (Diameter > 2.1 cm with < 50% collapse) suggests high CVP (fluid overload, tamponade, or RV failure).
• Collapsible IVC: (Diameter < 2.1 cm with > 50% collapse) suggests the patient may be fluid-responsive in the setting of shock.

---

3. Integration into ICU Protocols

FoCUS is rarely used in isolation. It is typically part of broader diagnostic algorithms:

• RUSH Protocol: (Rapid Ultrasound in Shock) – Evaluates “The Pump” (Heart), “The Tank” (IVC/Fluids), and “The Pipes” (Aorta/DVT).
• FATE Protocol: (Focus Assessed Transthoracic Echocardiography) – A systematic approach to rule out the most common causes of circulatory failure.

Note: FoCUS is a screening tool. If you find significant valvular disease or complex pathology, a formal Comprehensive Echocardiogram by a cardiologist is indicated.