Tamponade

Question 1

How does fluid administration affects patients with tamponade?

Answer 1

Once the pericardial pressure exceeds a stretch limit (bar), it increases exponentially with any change in volume. Even when intrapericardial pressure is lower than right-sided pressure, the RV or RA transmural pressure (RA pressure or RV pressure minus intrapericardial pressure) is reduced, which impairs RV outward expansion and filling; in addition, at this point, pericardial pressure is at a steep slope, and there is at least a threatened tamponade.

Although fluid administration may initially increase RV pressure and RV transmural pressure, intracardiac volume can stretch the pericardium and further increase intrapericardial pressure even if intrapericardial volume is unchanged; this explains how fluid administration in euvolemic or hypervolemic patients may be harmful.

Question 2

As opposed to CP however, the respiratory changes of intrathoracic pressure are _____________ to the cardiac chambers.

Answer 2

As opposed to CP however, the respiratory changes of intrathoracic pressure are transmitted to the cardiac chambers

This explains why RA pressure decreases during inspiration and thus venous flow from the SVC to the RA increases during inspiration (absence of the Kussmaul’s sign).

Left-sided flow does not increase because pulmonary veins and LV are both exposed to the negative intrathoracic pressure

Question 3

This is the reduction of systolic arterial pressure by more than 10 mmHg with normal inspiration

Answer 3

Pulsus Paradoxus

The increased venous flow to the right cavities makes the RV push against the LV in diastole, rather than push against the pericardium since the high pericardial pressure prevents that.

This reduces LV filling in inspiration and explains the reduction of systolic arterial pressure by more than 10 mmHg with normal inspiration

Question 4

Difference of Tamponade vs CP

Effect of ventricular interdependence
RA tracing

Answer 4

During inspiration, RV pushes LV in tamponade, whereas RV is sucked by LV in CP

LV flow is reduced in tamponade because of RV compression, not because of a lack of transmission of the negative intrathoracic pressure to LV

Because of the uniform pericardial fluid, the constraint is more uniform across both LV and RV in case of tamponade.

Ventricular interdependence is more prominent in tamponade and leads to pulsus paradoxus, which is only present in one third of cases of CP

The heart is compressed throughout all diastole in tamponade, including early diastole. Thus, RA-to-RV flow is impeded throughout all diastole, including early diastole, and there is no deep Y on the RA tracing and no diastolic dip on the RV tracing.

There is a deep X in early systole as RV annulus moves down and stretches out the compressed RA.

Question 5

Hemodynamic findings in tamponade

Answer 5

1. Elevated mean RA and SVC pressure
2. Deep X, flat Y
3. Equalization of diastolic pressures of 4 cardiac chambers, equal PA diastolic with RVEDP
4. Pulsus Paradoxus
5. Absent Kussmauls sign

Question 6

Pulses Paradoxus may not be seen in cases of

Answer 6

(1) ASD, as the increase in right-sided flow during inspiration is balanced by an increase in right-to-left shunt or reduction in left-to-right shunt, leading to less ventricular interdependence
(2) Local tamponade (eg, compression of LA or RA by a clot after cardiac surgery, leading to a localized increase in pressure)
(3) AI, where the diastolic regurgitant flow damps down respiratory fluctuations of flow.
Pulsus paradoxus is difficult to detect in case of an irregular rhythm such as atrial fibrillation.