Effusion

Pericardial Effusion - Tamponade

Pericardial effusion. Measurement should be taken in diastole. Tamponade is a diastolic problem, with restrictive filling. Here, the effusion seems circumferential. Not surprisingly, in a newborns that is lying on his back, the effusion collects posteriorly along the posterior wall of the LV. The fluid can be seen in parasternal short and long axis view in this particular case.

Evaluation of restricted filling - PW of RV and LV inflow. 

• Increased tricuspid valve inflow variability on spectral PW-Doppler (normal <40%)

• Increased mitral inflow variability on spectral PW-Doppler (normal <25%)

A good practice is to compress time in order to observe variation in inflow Doppler velocities. This may be altered in individuals that are not spontaneously breathing.

Ref: https://pedecho.org/library/chd/pericardial-tamponade

Measurements should be done at the end of diastole. Here, as outlined by the ECG tracing, just before the P-wave.

Ultrasound signs of Tamponade

Right atrial collapse during ventricular contraction / systole. 

Swinging Heart (M-mode echocardiography): The heart appears to swing back and forth within the pericardial sac during systole and diastole due to the restricted movement caused by the pericardial effusion.

Respiratory flow variation across the atrio-ventricular valves (mitral or tricuspid). Doppler Surrogate of Pulsus Paradoxus.

Right ventricular collapse during ventricular relaxation (diastole) - tamponade is a diastolic and filling condition. This could be appreciated by M-Mode.

Inferior vena cava distended with minimal respiratory variability

More Information Here and Here.

Long axis subcostal / subxyphyoid view outlining circumferential pericardial effusion with collapse of the right atrium.

Subcostal/subxyphoid short axis view outlining circumferential effusion. The IVC is seen distended and without variation in caliber. This outlines some degree of tamponade physiology.

Apical view outlining the RV and RA collabse. RA collabse during systole and RV collapse during diastole. Large effusion not obliterating during diastole.

Parasternal views (long and short axis). One may appreciate the RV collapse during diastole, as well as the circumferential pericardial fluid. 

Emergency Pericardiocentesis Procedure

Multi-Disciplinary Pediatric Point of care Ultrasound Bootcamp Simulation Scenario 

The crashing neonate

Case shared by Dr Brahim Bensouda from Hôpital Maisonneuve Rosemont 

A newborn presented initially with significant retractions without bradycardia. Dr Bensouda, TnECHO specialist and Neonatologist member of the TnECHO Quebec Collaborative, had done the workshop on pericardiocentesis and had trained through simulation on how to perform this technique at the bedside. A TnECHO was obtained and the images are shared below.

The views above are in the subcostal area showing a large pericardial effusion. There is altered filling and contractility. The heart is moving in the pericardial pocket during contraction. The liquid is anechoic (black appearance). 

Milky pink fluid aspirated by emergency pericardiocentesis. After puncture, it is important to remove the needle from the catheter to avoid puncture of the muscle wall upon re-expansion while draining the pericardial fluid. The fluid should be sent for cytology / cell count (especially for lymphocytes), culture, total protein, LDH albumin level, triglycerides and biochemistry (electrolytes and glucose) - to evaluate if presence of total parenteral nutrition (TPN) fluid and intravenous lipid fluid. In this case, upon fluid drainage, one can see that the heart function is back to normal with adequate filling. A catheter is seen in the right atrium, which has been withdrawn.  The fluid analysis was compatible with extravasated TPN/Lipids. 

Bilateral pleural effusions in the subxyphoid view.

Example of a right sided pleural effusion (before drainage)

After drainage:

Variations in inflow velocity explained

The variations in inflow velocity observed in cardiac tamponade, especially more pronounced on the right ventricle (RV) side compared to the left ventricle (LV) side, can be explained by the following mechanisms:

1. Intrathoracic Pressure Changes:

   • During respiration, intrathoracic pressure changes influence the venous return to the heart. In cardiac tamponade, the pericardial pressure is elevated and restricts the heart's ability to expand. However, the RV, being more compliant and under lower pressure compared to the LV, is more susceptible to these pressure changes.

   • During inspiration, the negative intrathoracic pressure increases venous return to the right side of the heart (RV). However, because the heart is constrained by the tamponade, this increased venous return cannot be accommodated, leading to an increase in RV inflow velocity. During expiration, the opposite occurs, reducing venous return and RV inflow velocity.

2. Ventricular Interdependence:

   • In cardiac tamponade, the constrictive pressure affects all chambers of the heart equally, but due to the fixed pericardial volume, any increase in volume of one chamber must be accompanied by a decrease in volume of another chamber. This interdependence is more noticeable in the RV because it is more affected by changes in intrathoracic pressure.

   • When the RV fills more during inspiration, it can lead to a transient reduction in LV filling (due to the shifting of the interventricular septum toward the LV). This mechanism results in less variation in LV inflow velocities because the LV operates at higher pressures and is less influenced by the intrathoracic pressure changes compared to the RV.

3. Pericardial Constraint:

   • The pericardial fluid in tamponade creates an equal pressure environment around the heart, but the thin-walled RV is more affected by this external pressure compared to the thicker-walled LV. Thus, changes in intrathoracic pressure during the respiratory cycle have a more significant impact on the RV filling dynamics.

4. Pressure-Volume Relationship:

   • The RV operates at lower pressures compared to the LV and is more compliant. This means the RV can accommodate changes in volume more readily than the LV, but within the constrained environment of tamponade, these changes manifest as variations in inflow velocity. The LV, being stiffer and working under higher pressures, exhibits less variation in inflow velocity under the same conditions.

Clinical findings in Tamponade

Symptoms:

1. Poor Feeding: Newborns may refuse to eat or have difficulty sucking.

2. Irritability or Lethargy: They may appear more irritable or unusually sleepy.

3. Tachypnea: Fast breathing due to decreased cardiac output and poor oxygenation.

4.  Pallor or Cyanosis: Pale or bluish skin indicating poor perfusion and oxygenation.

5. Decreased Urine Output: Oliguria due to reduced renal perfusion.

Physical Examination Findings:

1. Beck's Triad:

   • Hypotension

   • Hepatomegaly or Distended Neck Veins (Difficult to observe in newborns, but may be suggested by bulging fontanelles).

   • Muffled Heart Sounds: On auscultation, heart sounds may be faint due to the insulating effect of pericardial fluid.

2. Tachycardia: Rapid heart rate as a compensatory mechanism.

3. Pulsus Paradoxus: May be difficult to assess in newborns but can be inferred from significant respiratory variations in blood pressure.

4. Hepatomegaly: Enlarged liver due to venous congestion, palpable under the right costal margin.

5. Poor Peripheral Perfusion, Cold extremities, prolonged capillary refill time.

Diagnostic Test Findings:

1. Electrocardiogram (ECG): Low voltage QRS complexes and electrical alternans might still be seen, though obtaining a good quality ECG can be challenging.

2. Chest X-ray: Enlarged cardiac silhouette. A central line positioned in the heart may be the etiology of the tamponade/effusion (as such, one have to stop the fluid from running as one of the first step of management).a

3. Echocardiography (Echo): 

   1. Pericardial Effusion: Presence of fluid around the heart is easily visualized (usually anechoic around the heart and the subcostal view being the best approach).

   2. Diastolic Collapse: Collapse of the right atrium and ventricle due to increased pericardial pressure.