IOTW 1/25/21

58 y/o M p/w chest pain and dyspnea

  1. What are the four primary sonographic signs of cardiac tamponade?
    • Pericardial effusion. Measure the largest pocket during diastole. Large is >2.0 cm. Moderate is 1.0 – 2.0 cm. Small is <1.0 cm. Trivial is only visible during systole. Important to remember that the rate of accumulation is more important than the actual size in developing tamponade.
    • Right-sided chamber collapse. In normal physiology, the right ventricle contracts during systole and the right atrium contracts during diastole. As an effusion accumulates, the intrapericardial pressure may overwhelm the intracardiac pressure. This will first lead to right atrial systolic collapse and may progress to the later finding of right ventricular diastolic collapse.
    • Plethoric IVC. As with any obstructive cardiac process, there will be loss of respiratory variation of the IVC.
    • Doppler surrogate of pulsus paradoxus. This can be assessed by measuring the inflow velocities of the mitral and/or tricuspid valve. The concept of pulsus paradoxus is that there is an exaggeration of the normal respiratory variation of blood pressure during tamponade physiology when intracardiac volume competes for space with the pericardial sac. This ventricular interdependence during inspiration will cause a decrease in mitral inflow velocity variation >25% and an increase in tricuspid inflow variation >40%.
  2. What intervals are represented by labels “A” and “B”?
    • The Y-axis of M-mode corresponds to depth, thus A represents the right ventricle with layer of pericardial effusion and B represents left ventricle with mitral valve.
  3. Which phases of the cardiac cycle are represented by labels “C” and “D”?
    • The X-axis of M-mode corresponds to time, thus C represents ventricular diastole where the first spike is the E-wave (early diastolic filling) and the second smaller spike is the A-wave (atrial kick). D represents the period of ventricular systole. It is important to recognize labels A-D because you can observe the variation in RV size during diastole to determine if there is true RV diastolic collapse. In this case, there is some RV collapse, however it is primarily in systole and does not overlap significantly with diastole.
  4. In the clinical setting of cardiac tamponade, how much variation throughout the respiratory cycle would you expect to see on the structure labeled “E”?
    • This represents the IVC and you would expect it to be plethoric with minimal to no respiratory variation. This carries a 95-97% sensitivity for cardiac tamponade.
  5. What is being measured in the diagram labeled “F”? Does this represent cardiac tamponade?
    • This is how the measurement of mitral inflow variation is performed. Note the doppler gate in the left ventricle near the mitral valve on the apical-4 view. The velocities of the tallest and shortest E-waves are measured. The percent decrease between 102 cm/s and 83 cm/s is approximately 20%, which is less than 25% and not quite suggestive of cardiac tamponade.

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