Point-of-Care Cardiac Ultrasound

POCUS Cardiac - Echo Essentials

• FoCUS: Rapid, qualitative, goal-directed bedside cardiac exam.
• Key Applications (Perioperative):
  • LV/RV function, gross valvular assessment.
  • Pericardial effusion/tamponade.
  • Fluid responsiveness, shock (hypotension/hypoxia).
• Basics & Knobology:
  • Transducer: Phased array (1-5 MHz).
  • Modes: 2D, M-mode, Color Doppler, PW Doppler.
  • 📌 BART: Blue Away, Red Towards.
  • Acoustic Impedance ($Z = \rho c$) differences create images.
  • Controls: Depth, Gain, Freeze.
• Technique: Probe orientation, patient position (left lateral decubitus).

⭐ M-mode provides superior temporal resolution for dynamic measurements like TAPSE (Tricuspid Annular Plane Systolic Excursion).

Standard Views - Window Shopping

• Parasternal (PSL): Left sternal edge, 2nd-4th ICS.
  • PSLAX (Long Axis): LV, RV, LA, MV, AoV. LV global function.

    ⭐ PSLAX is crucial for initial assessment of LV size, global systolic function, and pericardial effusion.

  • PSSAX (Short Axis): "Mercedes-Benz" (AoV), "Fish-mouth" (MV), papillary muscles. RV assessment.
• Apical (APL): Point of Maximal Impulse (PMI).
  • A4C (4-Chamber): All 4 chambers, MV, TV. RV size/function.
  • A2C (2-Chamber): LA, LV (anterior, inferior walls).
  • A5C (5-Chamber): A4C + LVOT, AoV.
• Subcostal (SC): Subxiphoid.
  • SC 4-Chamber: Good for pericardial effusion, tamponade. Often best in ventilated patients.
  • SC IVC View: IVC diameter & collapsibility (fluid status).
• Suprasternal Notch (SSN): Aortic arch, great vessels.

LV & RV Assessment - Pump Power

• LV Global Function:
  • Qualitative: Hyperdynamic, Normal, Mild/Moderate/Severe ↓ contractility.
  • EPSS (E-point Septal Separation): Distance from anterior mitral leaflet to septum. Normal < 7mm. > 10mm suggests ↓ LVEF.
  • Fractional Shortening (FS): $FS = \frac{(LVIDd - LVIDs)}{LVIDd} \times 100%$. Normal 25-45%.
• RV Size & Function:
  • RV/LV Basal Diameter Ratio: Normal < 0.6. RV dilatation if > 1.0.
  • TAPSE (Tricuspid Annular Plane Systolic Excursion): Normal > 17mm. < 16mm indicates RV dysfunction.
  • RV S' (Tissue Doppler): Lateral tricuspid annulus systolic velocity. Normal > 9.5 cm/s.
• Pericardial Effusion & Tamponade:
  • Effusion: Echo-free space around heart.
  • Tamponade signs: RA/RV diastolic collapse, IVC plethora (dilated, < 50% inspiratory collapse).

  ⭐ Right ventricular diastolic collapse is an early and specific echocardiographic sign of cardiac tamponade.

Hemodynamics & Valves - Fluid & Flow

• Volume Status (IVC):
  • Diameter: < 2.1 cm (low RAP, ~0-5 mmHg), > 2.1 cm (high RAP, ~10-20 mmHg).
  • Collapsibility Index (CI) > 50% with sniff/inspiration → fluid responsive.
  • 📌 "Small & Squishy IVC" → needs Sips (fluids).
• LV Function & Filling:
  • "Kissing walls" (end-systolic obliteration) → severe hypovolemia.
  • Assess global LV contractility (qualitative).
• Fluid Responsiveness Tests:
  • Passive Leg Raise (PLR): ↑CO/SV > 10-15%.
  • IVC CI > 50% (spont. breathing).
• Basic Valve Assessment (Qualitative):
  • Stenosis: Leaflet mobility ↓, thickening, calcification.
  • Regurgitation: Color Doppler (jet origin, size, direction).
• Flow Parameters (Doppler):
  • Stroke Volume ($SV$) via LVOT VTI: $SV = VTI_{LVOT} \times CSA_{LVOT}$.
  • Cardiac Output ($CO = SV \times HR$).

⭐ PLR-induced increase in LVOT VTI > 12-15% predicts fluid responsiveness with high sensitivity and specificity.

High‑Yield Points - ⚡ Biggest Takeaways

• Key Views: PSLA, PSSA, A4C, Subcostal are fundamental for rapid cardiac assessment.
• LV Function: Qualitatively assess global and regional wall motion; estimate ejection fraction (EF).
• RV Assessment: Check RV size (RV/LV ratio < 0.6) and TAPSE for RV function.
• Tamponade: Identify pericardial effusion and look for signs like diastolic RV collapse.
• Volume Status: Use IVC diameter and collapsibility index to guide fluid management.
• FEEL Protocol: In cardiac arrest, rapidly exclude reversible causes like tamponade, PE, severe hypovolemia.
• Gross Valvular Lesions: Quickly identify significant stenosis or regurgitation impacting hemodynamics.