Heart is externally covered by two layers of pericardium . Pericardial space is formed between parietal and visceral layers of pericardium . It is a narrow space which is normally lubricated with pericardial fluid up to 25ml. When these two tissue surfaces come into contact , pathological rub takes place.It is heard whenever the pericardium is inflammed . Pericardial rub is a distinctive but uncommon clinical sign .
Common clinical conditions
- Acute pericarditis
- Uremic pericarditis.
- Rheumatic pericarditis
- Post myocardial infarction
Pericardium has two layers .
There are four possibilities for pericardial rub to take place.
The rub can occur
1.Between the two layers of pericardium
2.Between the visceral pericardium and the epicardial layer of heart*.
3.Between parietal pericardium and the chest wall
4.Pericardium can rub with the adjacent pleura( Pleuro pericardial rub )
The second and third mechanisms are very rare.
We have realized one more possibility . Diaphragm forms the floor of the heart on which the hanging heart rests . Rubbing of pericardium over diaphragmatic surface is a beat to beat affair that lasts the entire life !. In inflammatory states of diaphragm especially the contagious ones from abdomen , can result in pericardio- diaphragmatic rubs .These rubs are almost impossible to hear clinically.
*The anatomic mystery : Is epicardium same as visceral layer of pericardium ?
Some anatomist feel that both are same entities. If that is the case myocardium can never split its relationship with visceral pericardium.But it is also a anatomical fact visceral pericardium engulfs the coronary artery and are located sub epicardially.
How many components of pericardial rub are clincally heard ?
Pericardial rub classically has three components. Systolic, mid diastolic, and pressytolic atrial components. Pericardial rubs are typically described as to and fro rub. Systolic component is most consistent. In atrial fibrillation mono component pericardial rub is heard.
Superficial , scratchy, high pitched ( Can also be low pitched)
Left sternal border , left 2nd or 3rd space .Best heard in sitting , leaning forward in inspiration. Many times the rubs are transient and evanescent . Since it has multiple components it may be mistaken for added heart sound like S 3 or S 4.
What is the mechanism of pericardial rub in the immediate post MI phase ?
Presence of pericardial rub post MI indicate a transmural involvement or atleast significant epicardial involvement . Recognition of this is important as presence of pericardial rub increases the risk of rupture and hemorrhagic effusion if anticoagulants are used.
What is the relationship between pericardial effusion and pericardial rub ?
Generally it is said with the onset of effusion pericardial rub disappear.But this is not necessarily true.
Rubs after contusion chest and fracture ribs can be with the chest wall and may have no relationship with effusion.
Is pericardial rub a painful condition ?
Pericardial rub associated with acute inflammatory pathology is severely painful (like a pleuritis).But pericarditis associated with chronic inflammatory conditions are less often generate pain.The exact reason is not known.
What is pleuro pericardial rub ?
This clinical entity is poorly defined , often taught by veteran professors in clinical auscultation classes.It can be heard in the mid segment or diaphragmatic pleuritis with or without pericardial effusion in patients with atypical pneumonias.