Pericardial Tamponade

Cardiac tamponade is a life-threatening, slow or rapid compression of the heart due to the pericardial accumulation of fluid, pus, blood, clots or gas as a result of inflammation, trauma, rupture of the heart or aortic dissection.

• Cardiac Tamponade is a clinical diagnosis, so assessing for pulsus paradoxus at bedside is very useful.
• H&P
  • Clinical signs in a patient with cardiac tamponade include tachycardia, hypotension, pulsus paradoxus, raised jugular venous pressure, muffled heart sounds
  • ECG:
    • low-voltage
    • electrical alternans
    • May show signs of pericarditis
  • Chest imaging (e.g., CXR) with enlarged cardiac silhouette
  • Classic signs include Beck’s triad
    • neck vein distension with elevated JVP,
    • pulsus paradoxus,
    • diminished heart sounds
  • Pericardial friction rub can be heard if concomitant pericarditis
• Fun fact: cath will show equilibration of average diastolic pressure and characteristic respiratory reciprocation of cardiac pressures, i.e. an inspiratory increase on the right and a concomitant decrease on the left---the proximate cause of pulsus paradoxus.
  • Except in low-pressure tamponade, diastolic pressures throughout the heart are usually in the range of 15-30 mmHg.
• Rate of accumulation is more important than the size of the effusion
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    • Figure source: ¹

Diagnosis

Clinical Exam

• Elevated JVP that does NOT change with respiration (- Kussmaul’s sign) may be seen. This is because of equalization of diastolic pressures with tamponade (“the pericardial pressure takes over everything in tamponade”)
  • Recall, Kussmaul’s sign is where the JVP increases with respiration

Pulsus Paradoxus at Bedside

• Inflate BP cuff until you can’t hear Korotkoff sounds
• Start deflating until you hear sounds intermittently (sounds disappear with inspiration). Record the systolic pressure at which Korotkoff sounds are first audible - ${\text{SBP}}_1$
  • sounds are initially intermittent and respirophasic, becoming audible with expiration and inaudible with inspiration
• Keep deflating until you hear sounds continuously (during inspiration and expiration) - ${\text{SBP}}_2$
• Pulsus paradoxus cutoffs: $\Delta ={\text{SBP}}_1-{\text{SBP}}_2$
  • $\Delta$ >10 mmHg → sens 98%, spec 70%, +LR 3.3, -LR 0.03
  • $\Delta$ >12 mmHg → sens 98%, spec 83%, +LR 5.9, -LR 0.03
  • 
• “Most textbooks define a greater than 10-mm Hg difference between the initial detection of sounds on expiration and the constant presence of sounds with each heartbeat through the respiratory cycle as a “pulsus paradoxus.” Some experts suggest that the absolute value of pulsus paradoxus should be interpreted as a percentage of the pulse pressure or as a percentage of the expiratory systolic pressure.” ²

Echo in Cardiac Tamponade

• Echo is the single most useful diagnostic tool to identify pericardial effusion and estimate its size, location and degree of hemodynamic impact
• Other findings not listed below include:
  • Abnormal ventricular septal motion
  • Inspiratory decrease and expiratory increase in pulmonary vein diastolic forward flow
  • Respiratory variation in ventricular chamber size
  • Aortic outflow velocity (echocardiographic pulsus paradoxus)

Early Echo Findings

• IVC dilated, not collapsing (“plethora”)
  • If IVC isn’t dilated, you may want to question Dx of cardiac tamponade
• Increased respiratory variation in mitral (> 25%) and tricuspid (> 40%) mitral inflow velocities
  • ⚠️ ASE guideline documents have used mitral >30% and tricuspid >60% as well.
  • Using the measured peaks (➕1 and ➕2), the variation is 21%, $\frac{(1.22-0.96)}{1.22}=0.21$. The peaks as designated by the arrows in Dr. Shah’s talk are probably the peaks you should be using, which gives your 57% variation, i.e. concerning for tamponade
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Late Echo Findings

• Early diastolic collapse of RV
  • 
• Late diastolic collapse of RA

Very Late Echo Findings

• LA and/or LV collapse

Waveforms

• Can also see equalization of mean RA, RV, and PA diastolic pressures and mean PCWP

• Recall, normal RA waveform tracings

  • V wave: Passive filling of the RA during RV systole
  • Y descent: TV opens, passive RA emptying
  • A wave: RA contraction
  • X descent: RA relaxation

• In tamponade you will see a blunted Y descent

  • Passive emptying of RA is dependent on pressure difference between RA and RV: in tamponade, the pericardial pressure takes over all other diastolic pressures (∴, loss of Y descent)
  • Occurs d/t diastolic equalization of pressures in the RA and RV + lack of effective flow across the TV in early ventricular diastole
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Footnotes

1. Spodick DH. Acute cardiac tamponade. N Engl J Med. 2003 Aug 14;349(7):684-90. doi: 10.1056/NEJMra022643. PMID: 12917306. ↩

2. Roy CL, Minor MA, Brookhart MA, Choudhry NK. Does this patient with a pericardial effusion have cardiac tamponade? JAMA. 2007 Apr 25;297(16):1810-8. doi: 10.1001/jama.297.16.1810. PMID: 17456823. ↩