Cardiac Chambers

POCUS-first practical categories are listed first. Formal echo reference values are included where useful.

2.1 Left ventricle

LVIDd

  • < 3.6 cm: small or underfilled.

  • 3.6–5.6 cm: normal practical range. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • 5.6 cm: dilated. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 3.9–5.3 cm in women and 4.2–5.9 cm in men. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

LVIDs

  • 2.2–4.0 cm: normal practical range.

  • 4.0 cm: suggests impaired systolic emptying.

IVSd / LVPWd

  • 0.7–1.1 cm: normal. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • ≥ 1.2 cm: thickened.

  • ≥ 1.5 cm: severely thickened, HCM range. (Stoica 2011 [R-2-07 = R-7-03]; XREF §7)

LVEF qualitative

  • Good, moderate, or poor.

LVEF quantitative

  • ≥ 55%: preserved; 50–54%: low-normal; 40–49%: mildly reduced; 30–39%: moderately reduced; < 30%: severely reduced. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 52–72%. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

Fractional shortening

  • ≥ 25%: normal; < 25%: reduced. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 25–45%. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

LV volumes indexed

  • LV EDV indexed: men 40–80 mL/m²; women 30–70 mL/m². LV ESV indexed: men 20–45 mL/m²; women 15–35 mL/m². (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

2.2 Left atrium

LA anteroposterior dimension

  • ≤ 4.0 cm: normal; 4.1–4.5 cm: mildly enlarged; > 4.5 cm: enlarged. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 3.0–4.1 cm. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

LA area

  • 14–22 cm²: normal practical range. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

LA volume index

  • ≤ 34 mL/m²: normal; > 34 mL/m²: enlarged; supports chronic elevated left atrial pressure. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

2.3 Right atrium

RA A / RA B dimension

  • ≤ 6.0 cm: normal; > 6.0 cm: enlarged. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 4.0–6.0 cm. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

2.4 Right ventricle

RVOT basal dimension

  • ≤ 3.2 cm: normal; > 3.2 cm: dilated. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 1.7–3.2 cm. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

RV free-wall thickness

  • 3–5 mm: normal; > 5 mm: thickened. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

RV end-diastolic area

  • Men: 19–32 cm²; Women: 16–27 cm². (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

TAPSE

  • ≥ 17 mm: normal; < 17 mm: impaired; < 14 mm: severely impaired. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Formal echo reference: approximately 17–26 mm. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

RVFAC

  • ≥ 35%: normal; < 35%: impaired. (Kirkpatrick 2024; Johri 2023 [R-2-05/06]; Orsinelli 2015 [R-2-03])

RV/LV diameter ratio

  • < 1: normal; ≥ 1: RV dilation or acute strain. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

RV/LV area ratio

  • < 0.6: normal; 0.6–1.0: mild; ≥ 1.0: marked.

RV S′ lateral tissue Doppler

  • Approximately 9.5–10 cm/s or greater: normal practical range. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

2.5 Inferior vena cava

IVC diameter

  • < 1.5 cm: collapsed or small; possible hypovolaemia.

  • 1.5–2.5 cm: normal or intermediate; correlate clinically.

  • 2.1 cm with inspiratory collapse < 50%: formal elevated RAP estimate; standard formal echo RAP approximately 15–20 mmHg. (Lang 2005/2015; Orsinelli 2015 [R-2-01/02/03])

  • 2.5 cm with poor collapse: plethoric or marked POCUS finding; avoid empiric fluids. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • 3.0 cm with minimal collapse: markedly plethoric; late warning. (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • 3.5 cm: marked plethora in some protocols; not a universal formal RAP cutoff; interpret as protocol-specific late warning. (Kirkpatrick 2024 [R-2-05])

Collapsibility in spontaneous breathing (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • 50%: low CVP; 20–50%: indeterminate; < 20%: high CVP.

  • Formula: collapsibility index = (Dmax − Dmin) / Dmax × 100.

Distensibility in mechanical ventilation (Kirkpatrick 2024; Johri 2023 [R-2-05/06])

  • Dmin-based distensibility: (Dmax − Dmin) / Dmin × 100. Common general controlled-ventilation threshold: ≥ 15%. Validation-specific range: approximately 12–21%. An 18% threshold remains appropriate in selected fully ventilated septic shock protocols; it is a validation-specific operating point, not the only standard.

  • Mean-based variability: (Dmax − Dmin) / [(Dmax + Dmin) / 2] × 100. Common mean-based threshold: 12%.

  • Do not interchange collapsibility, Dmin-based distensibility, and mean-based variability. (Kirkpatrick 2024 [R-2-05])

POCUS safety rule (Kirkpatrick 2024; Johri 2023 [R-2-05/06]) — IVC > 2.5 cm with poor collapse is plethoric; avoid empiric fluids. IVC > 3.0 cm with minimal collapse is markedly plethoric and is a late warning. IVC > 3.5 cm is not a universal formal RAP cutoff; it is a protocol-specific marker of marked plethora.

Technique (Lang 2005/2015 [R-2-01/02]; Kirkpatrick 2024 [R-2-05]) — Measure from the subcostal long-axis view, approximately 1–2 cm from the RA–IVC junction, perpendicular to the IVC long axis. Assess diameter and respiratory variation. In adults, use a low-frequency phased-array or curvilinear probe. Do not use sustained maximal inspiratory strain or Valsalva-like effort for collapsibility. In fully mechanically ventilated patients without spontaneous breathing activity, use distensibility or mean-based variability instead of collapsibility.

2.6 Aortic root

  • < 40 mm: normal; ≥ 40 mm: dilated; ≥ 50 mm: aneurysmal. (Kirkpatrick 2024; Johri 2023 [R-2-05/06]; vascular cross-use: Chang 2021 [R-2-09], XREF §8.1/8.2/8.3; caveat: Q&A book text)

  • Aortic root measurement should be integrated with aortic valve assessment, pericardial effusion, aortic regurgitation, and clinical suspicion for acute aortic syndrome.

2.7 Pitfalls

  • Misidentifying RV as LV in poor windows.

  • Overestimating LV function in a hyperdynamic state.

  • Underestimating RV dilation when chronically enlarged.

  • Failing to distinguish acute from chronic RV enlargement.

References:

  1. Lang RM, et al. J Am Soc Echocardiogr. 2005;18(12):1441–63. [R-2-01]

  2. Lang RM, et al. J Am Soc Echocardiogr. 2015;28(1):1–39.e14. [R-2-02]

  3. Orsinelli DA, et al. J Am Soc Echocardiogr. 2015;28(7):687–97. [R-2-03]

  4. Kirkpatrick AW, et al. 2024. [J/pp TBC] [R-2-05]

  5. Johri AM, et al. Am J Med. 2023;136(4):621–8. [R-2-06]

  6. Stoica, et al. 2011. [TBC] [R-2-07 = R-7-03]

  7. Chang AC, et al. 2021. [1200 Q&A book; TBC] [R-2-09]