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← Section III · Chamber Size and Function
III.E

Left Atrium, Pulmonary Veins, and Coronary Sinus

12 cards

Notes

LA normal values

  • LA volume index (biplane method of disks): normal ≤ 34 mL/m².
  • LA volume is a superior marker of LA size to LA AP diameter.
  • Mildly enlarged 34–41; moderate 42–48; severe > 48 mL/m².

Causes of LA enlargement

  • Diastolic dysfunction with chronically elevated filling pressures.
  • Chronic AF.
  • Mitral valve disease (MR, MS).
  • Chronic HTN.
  • Athlete's heart.
  • Obesity.
  • High-output states.

Pulmonary vein Doppler

  • Sampled 1–2 cm into the right upper or right lower PV (best window from apical or subcostal).
  • S wave - systolic forward flow.
  • D wave - diastolic forward flow.
  • Ar wave - retrograde flow with atrial contraction.

Normal patterns

  • Young adult: S ≈ D or S > D; Ar velocity < 0.35 m/s; Ar duration < mitral A duration.

Abnormal patterns

  • S > D → normal or Grade I diastolic dysfunction.
  • S < D → elevated LAP (Grade II or higher).
  • Ar velocity ≥ 0.35 m/s OR Ar duration exceeds mitral A duration by ≥ 30 ms → elevated LVEDP.

Left atrial appendage (LAA)

  • Best visualized on TEE (mid-esophageal at 45–90°).
  • Pectinate muscles: finger-like ridges (100–110°).
  • Emptying velocity:
    • Normal ≥ 40 cm/s.
    • < 20 cm/s → severe SEC risk, thrombus, high embolic risk.
  • Spontaneous echo contrast (SEC) - swirling smoke-like echoes; marker of stasis and future embolic events.
  • LAA thrombi typically located at the tip and may be multilobulated.
  • Coumadin ridge ("Q-tip") - muscular ridge between LAA orifice and left upper PV; normal anatomy, NOT thrombus.
  • Post-LAA ligation: high incidence of residual flow between LA and LAA (partial closure).

Coronary sinus

  • Runs in the posterior AV groove; receives most cardiac venous drainage; opens into the RA at the Thebesian valve.
  • Dilated CS - causes:
    • RA hypertension (severe TR, PHT, right heart failure).
    • Persistent left SVC to CS (most common congenital cause).
    • Coronary AV fistula draining to CS.
    • Anomalous pulmonary venous return to CS.
  • Contrast injection into the left arm enters the persistent left SVC and opacifies the CS before the RA - pathognomonic for persistent left SVC.

Pulmonary vein anatomy

  • 4 pulmonary veins normally (2 R, 2 L).
  • Anomalous pulmonary venous connection:
    • PAPVR - usually right upper PV to SVC (associated with sinus venosus ASD).
    • TAPVR - all four PVs connect to systemic venous system (supracardiac, cardiac (CS), infracardiac, mixed).

Cor triatriatum sinistrum

  • Fibromuscular membrane divides the LA into two chambers: posterior (receives PVs) and anterior (connected to LAA and MV).
  • Gradient present in BOTH systole and diastole (unlike valvular MS, which is diastolic only).

Cards

  • basicIII.E-001
    State the LA volume index upper limit of normal.
    → ≤ 34 mL/m² by biplane method of disks in the apical 4- and 2-chamber views (end-systole, before MV opening).
  • basicIII.E-002
    Why is LA volume index preferred over LA anteroposterior diameter for size assessment?
    → LA volume better reflects three-dimensional remodeling. AP diameter alone underestimates LA size when enlargement is longitudinal or asymmetric.
  • basicIII.E-003
    State the LAA emptying velocity thresholds for normal vs high embolic risk.
    → Normal ≥ 40 cm/s. < 20 cm/s → severe SEC risk, thrombus formation, and cardioembolic events.
  • basicIII.E-004
    What is spontaneous echo contrast (SEC) and what does it imply?
    → Swirling smoke-like echoes within the LA/LAA reflecting slow blood flow and RBC rouleaux formation. Marker of stasis; associated with prior CVA and future embolic events in AF.
  • basicIII.E-005
    Where in the LAA are thrombi most commonly located?
    → At the tip (distal-most portion) of the appendage. They may be multilobulated. Pectinate muscles at 100–110° are the main mimic — should not be mistaken for thrombus.
  • basicIII.E-006
    What is the 'Coumadin ridge' (also called 'Q-tip' or warfarin ridge)?
    → A muscular ridge between the LAA orifice and the left upper pulmonary vein. It is a normal anatomic structure — often mistaken for thrombus.
  • basicIII.E-007
    List four causes of a dilated coronary sinus.
    → 1) RA hypertension (severe TR, PHT, right heart failure). 2) Persistent left SVC draining to CS (most common congenital cause). 3) Coronary arteriovenous fistula draining to CS. 4) Anomalous pulmonary venous return to CS.
  • basicIII.E-008
    How can persistent left SVC be confirmed at the bedside?
    → Inject agitated saline into the LEFT arm — bubbles appear in the coronary sinus first (which is dilated), then flow into the RA. Contrast in the CS before the RA is diagnostic.
  • basicIII.E-009
    What are the three waves of a normal pulmonary vein Doppler?
    → S (systolic forward flow), D (diastolic forward flow), Ar (retrograde flow with atrial contraction). Young adults typically have S ≥ D; Ar velocity < 0.35 m/s.
  • basicIII.E-010
    How does the PV S/D ratio change with elevated LA pressure?
    → S < D. Normal LAP: S ≥ D. As LAP rises with diastolic dysfunction, systolic filling is impaired and D dominates.
  • basicIII.E-011
    What is Cor triatriatum sinistrum and how does its Doppler differ from valvular MS?
    → Congenital fibromuscular membrane dividing the LA into two chambers. Doppler shows a gradient across the membrane in BOTH systole and diastole (unlike valvular MS which is diastolic only).
  • basicIII.E-012
    What is partial anomalous pulmonary venous return (PAPVR) and its most common ASD association?
    → One or more (but not all) PVs drain to the systemic venous system. Most common: right upper PV to SVC — strongly associated with sinus venosus ASD.