Dagger-shaped LVOT Doppler - classic in HOCM, but increasingly relevant in
#CriticalCare #Nephrology #POCUS
• What you see
Late-peaking, “dagger” CW Doppler profile
Slow rise → abrupt mid–late systolic peak
• Why it matters
Distinguishes dynamic LVOT obstruction from fixed AS (which peaks early)
• Mechanism
Systolic anterior motion (SAM) of mitral valve
→ leaflet pulled into LVOT during ejection
→ obstruction worsens as systole progresses
• Hemodynamics
Gradient = 4 × V²
≥30 mmHg → significant obstruction
Not just HCM — big ICU problem
Dynamic LVOTO can occur without structural HCM
Seen in septic shock, stress cardiomyopathy, hypovolemia
🚨 Can present as refractory hypotension
…and paradoxically worsens with inotropic vasoactive agents.
Triggers
• Hypovolemia
• Inotropes (dobutamine 👎)
• Low afterload (sepsis)
• Tachycardia, hypercontractility
• High sympathetic tone
Substrate
• LVH (common in
#ESRD)
• Small LV cavity
• Sigmoid septum
• Elderly, often female
#POCUS clues (don’t miss this)
• Hyperdynamic, small LV
• SAM of mitral valve (use M-mode in PLAX)
• LVOT flow acceleration
• Dagger-shaped CW Doppler (key finding)
Management flips the script (“LVOTO bundle”)
❌ Stop harm
• Inotropes
• Diuretics
✅ Do the opposite
• Fluids → increase preload
• Afterload → switch norepinephrine to phenylephrine/vasopressin
• Beta-blockade → reduce contractility
• ↓ PEEP if too high
Bottom line
Not all hypotension needs more inotropy.
If you see a dagger, think LVOTO and reverse your reflexes.