Tamponade Pathophysiology Flashcards
(32 cards)
What is Cardiac Tamponade?
Compression of the heart by fluid within the pericardiac which impairs diastolic filling of both ventricles
Pathophysiology of Tamponade?
- Fluid, blood, clots, pus, gas or combinations accumulate in pericardial sac
- Increased intra-pericarddal pressure(IPP)
- Compression
- Impeded diastolic filing of both ventricles
- Systemic and pulmonary congestion
- Decreased SV and CO
Clinical signs of tamponade: signs of systemic and pulmonary congestion?
- JVD (jugular vein distention)
- Hepatomegaly
- Ascites
- Peripheral oedema
Clinical signs of tamponade: signs of reduced SV and CO?
- Hypotension/shock
- Reflex tachycardia
- Pulsus paradoxus
- Most overt clinical signs of tamponade relate to reduced SV and CO
What are the most common clinical findings in tamponade?
- Tachycardia
- Elevated jugular venous pressure
- Pulsus paradoxus
(Note: up to 30% of tamponade pts will not have classic clinical features)
Is tamponade an echo or clinical diagnosis?
- Clinical diagnosis
- Echo can be useful in confirming diagnosis when classic clinical signs are absent
What are transmural filling pressures (TMFP)?
- Describes the difference in pressure between the inside and the outside of the heart
- TMFP = ICP - IPP
- TMFP is positive: prevents cardiac chambers from collapsing, even when pressure inside the heart is zero
Normal thoracic cavity pressure (ITP) and pericardial cavity pressure (IPP)?
- Normally ITP is almost the same as pressure in the pericardium (IPP)
- Both of these pressure are usually sub atmospheric or slightly negative
Normal heart pressure (ICP)?
- ICP is normally positive, buy may be zero at end-diastole
What pressure is pulmonary venous return influenced by?
Pulmonary veins contained entirely within thoracic cavity so influenced by ITP
What pressure is systemic venous return influenced by?
- IVC and SVC are not entirely contained within the thoracic cavity
- IVC in abdominal cavity so influenced by intra-abdominal pressure (IAP) as well as ITP
Normal right heart filling with inspiration?
- Diaphragm descends resulting in increased IAP (intra-abdominal pressure) and reduced ITP
- Augments systemic venous return
- Increased right heart filling
Normal right heart filling with expiration?
- Diaphragm moves up
- Decreased IAP
- Increased ITP
- Decreases systemic venous return
- Reduced right heart filling
Normal left heart filling with respiration?
- Minimal variation as pulmonary veins contained within thoracic cavity
- Changes in ITP transmitted to pericardial sac and pulmonary veins
Normal left heart filling with inspiration?
- As ITP falls with inspiration, so too does pulmonary venous pressure and IPP
Normal left heart filling with expiration?
- ITP, pulmonary venous pressure and IPP all increase to the same degree
Normal arterial pressure over respiration?
- Increased RV filling during inspiration causes IVS to bow slightly towards the left
- Slight respiratory reduction in LV filling and LV SV
- Also slight inspiratory fall in systemic arterial systolic pressure (< 10mmHg)
What is ventricular interdependence?
- Changes to the size, shape, pressure and volume of one ventricle affects the size, shape, pressure and volume of the other ventricle
- Normal ventricular interaction is minimal
Normal ventricular interdependence?
- With inspiration;
1) increased RV filling slightly
2) reduces LV filling which leads to
3) slight decrease in CO and slight
4) decrease in systemic arterial pressure
Changes in transmural filling pressure with tamponade?
Decreased
Changes in right and left heart filling with respiration in tamponade?
Exaggerated primarily due to increased IPP
Changes in ventricular interdependence with tamponade?
Enhanced
Transmural Filling Pressures (TMFP) with tamponade?
- As IPP rises, ICP also rises in an attempt to maintain positive TMFP and adequate CO
- As IPP becomes more positive despite increase in ICP, resultant TMFP becomes negative, resulting in collapse of cardiac chambers
Left heart filling with tamponade?
- ITP falls with inspiration as normal, ITP fall transmitted to pul. veins as normal
- However, IPP elevated so diastolic filling gradient between pul. veins and left heart falls during inspration
- With inspiration, left heart filling is decreased more than normal
