**10. Classic findings in catheterization**


The atrial pressure curve shows high "a" and high "v" waves and prominent "x" and "y" descents ("M" and "W" appearance) (**Figure 2**)*.*

Due to high venous pressure, ventricular filling is rapid in early diastole. The result is a deep fall in early diastole followed by a spike ("tip") and a high diastolic plateau in ventricular pressure curves. This typical finding is called "square root sign" because it resembles the " deep and plateau" and the square root ( ) sign (**Figure 3**)*.*

#### **Figure 2.**

*High "a" and "v" waves, deep and slow "x" and "y" descents (M view) in right atrial pressure curve for constrictive pericarditis.*

#### **Figure 3.**

*"Deep" and plateau (square root, indicated by a red elliptical circle) sign in the right ventricular pressure curve for constrictive pericarditis.*


When the gradient between pulmonary capillary wedge pressure and intrathoracic and left ventricular diastolic pressure develops, a difference of ≥5 mmHg between the expiration and inspirum has been reported as 81% specificity and 93% sensitivity for the diagnosis of constrictive pericarditis (**Figure 4**) [63].

### **10.1 Biopsy and surgical exploration**

There may be cases where the diagnosis remains uncertain even after extensive evaluation with hemodynamic catheterization, imaging modalities, and echocardiography. Surgical exploration is sometimes recommended in these cases. Endomyocardial biopsy may be a suitable option before surgical exploration [64] (**Table 4**).

### **10.2 Treatment**
