Point-of-Care Ultrasound (POCUS): Heart Ultrasound

Introduction

Heart ultrasound through POCUS allows for rapid assessment of cardiac function, structural abnormalities, and conditions such as pericardial effusion, pulmonary embolism, or ventricular dysfunction. Below is a comprehensive guide on the views, objectives, and key findings in heart POCUS.

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Cardiac Ultrasound Views and Probe Placement

1. Parasternal Long Axis View

• Probe Placement:
  • Place the probe to the left of the sternum at the 3rd or 4th intercostal space, with the indicator pointing toward the patient's right shoulder.
• Visualization:
  • Left ventricle (LV), left atrium (LA), right ventricle (RV), aortic valve, mitral valve, and pericardium.
• Clinical Uses:
  • Evaluate LV function, pericardial effusion, and chamber size.

2. Parasternal Short Axis View

• Probe Placement:
  • Same intercostal space as the parasternal long axis, but rotate the probe 90° so the indicator points toward the patient’s left shoulder.
• Visualization:
  • Transverse cross-section of the LV (appears circular), RV, papillary muscles, and pericardium.
• Clinical Uses:
  • Assess LV contractility, wall motion abnormalities, and septal flattening (D-shape of LV in pulmonary embolism).

3. Apical 4-Chamber View

• Probe Placement:
  • Place the probe at the point of maximal impulse (PMI) or below the left nipple, with the indicator pointing toward the patient’s left axilla.
• Visualization:
  • Four chambers: RA, LA, RV, and LV.
• Clinical Uses:
  • Assess global and regional ventricular function, valve abnormalities, and RV/LV ratio.

4. Apical 2-Chamber View

• Probe Placement:
  • From the apical position, rotate the probe approximately 60° counterclockwise.
• Visualization:
  • LV and LA, as well as the anterior and inferior walls.
• Clinical Uses:
  • Evaluate LV function and regional wall motion.

5. Subxiphoid 4-Chamber View

• Probe Placement:
  • Place the probe just below the xiphoid process, angled superiorly and toward the left shoulder, with the indicator pointing to the patient’s left.
• Visualization:
  • Four chambers (RA, RV, LA, LV) and pericardium.
• Clinical Uses:
  • Assess pericardial effusion, IVC collapsibility, and cardiac tamponade.

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Objectives in Heart POCUS

1. Differentiate Pericardial Effusion from Pericardial Fat or Pleural Effusion:
   • Pericardial Fat: Appears as a hypoechoic band anterior to the right ventricle.
   • Pericardial Effusion: Fluid collection within the pericardial sac (surrounds the heart).
   • Pleural Effusion: Fluid posterior to the descending thoracic aorta; distinguish by adjusting depth.
2. Assess Pericardial Effusion:
   • Semi-Quantitative Grading:
     • Small: <1 cm separation.
     • Moderate: 1–2 cm separation.
     • Large: >2 cm separation.
3. Evaluate Pulmonary Embolism (PE):
   • Signs of RV dysfunction:
     • RV dilation: RV/LV ratio >1 (normally <0.9).
     • McConnell Sign: Hyperkinesis of the RV apex with hypokinesis of the free wall (apical 4-chamber view).
     • Flattened Septum (D-shape LV): Parasternal short-axis view.
   • Dilated IVC with reduced collapsibility: Subxiphoid view.

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Key Cardiac Findings

Pericardial Effusion

• Respiratory Paradoxical Septal Motion: Compression of the heart during inspiration.
• RA Collapse: Occurs during diastole; indicates elevated pericardial pressure.
• RV Collapse: Seen in early diastole; more specific for tamponade.

Pulmonary Embolism

• RV Dilation:
  • RV basal diameter > LV basal diameter.
  • RV/LV ratio >1 in apical 4-chamber view.
• D-shaped LV:
  • Flattened intraventricular septum (parasternal short axis).
  • Normal LV appears circular, but the RV overload causes a D-shaped deformation.
• 60/60 Sign:
  • Pulmonary artery acceleration time <60 ms.
  • Tricuspid regurgitation pressure gradient (TRPG) <60 mmHg.
• McConnell Sign:
  • RV apex remains hyperkinetic, while the free wall is akinetic.

Inferior Vena Cava (IVC)

• Dilated IVC:
  • Indicates elevated right atrial pressure (>15 mmHg).
  • Lack of inspiratory collapse suggests RV failure or tamponade.

Cardiac Tamponade

• Beck’s Triad (Clinical): Hypotension, distended neck veins, and muffled heart sounds.
• Ultrasound Signs:
  • RA and RV diastolic collapse.
  • Large pericardial effusion.

Right Heart Thrombus:

• Mobile hyperechoic mass detected in right atrium or ventricle (subxiphoid or apical view).

Pulmonary Embolism Diagnostic Indicators

1. Enlarged RV:
   • Basal RV > LV in parasternal long-axis view.
   • Apical 4-chamber view: RV/LV ratio >1.
2. Septal Flattening:
   • "D-shaped LV" in parasternal short axis.
3. TAPSE:
   • Tricuspid annular plane systolic excursion <16 mm (M-mode).
4. Tissue Doppler Imaging:
   • Tricuspid annulus systolic velocity (S') <9.5 cm/s.
5. IVC Findings:
   • Dilated IVC with reduced inspiratory collapse.

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Conclusion

POCUS for cardiac evaluation is a powerful diagnostic tool, especially for conditions like pericardial effusion, cardiac tamponade, and pulmonary embolism. Mastering probe placement, ultrasound anatomy, and the interpretation of key signs ensures rapid and accurate bedside assessments. Use these findings in conjunction with clinical judgment for optimal patient care.