The Dip and Plateau Sign in Constrictive Pericarditis
The dip and plateau sign (also known as the "square root sign") is a characteristic hemodynamic finding in constrictive pericarditis, observed during cardiac catheterization as a rapid early diastolic pressure drop (dip) followed by a rapid rise and plateau in ventricular pressure curves.
Pathophysiology and Mechanism
The dip and plateau sign occurs due to the specific pathophysiological changes in constrictive pericarditis:
- Early diastole (the "dip"): When the atrioventricular valves open, there is a rapid early ventricular filling due to elevated atrial pressures, causing a sharp drop in ventricular pressure.
- Mid-to-late diastole (the "plateau"): The thickened, fibrotic pericardium prevents further ventricular expansion, causing an abrupt cessation of filling and a plateau in the pressure curve.
Diagnostic Context
The dip and plateau sign is primarily identified during:
- Cardiac catheterization: Considered a key diagnostic finding for constrictive pericarditis 1
- Right and left ventricular pressure tracings: The sign is typically present in both ventricles
- Pressure equalization: Accompanied by equalization of right and left ventricular end-diastolic pressures (usually within 5 mmHg) 1
Differential Diagnosis
This hemodynamic pattern helps differentiate constrictive pericarditis from restrictive cardiomyopathy:
| Feature | Constrictive Pericarditis | Restrictive Cardiomyopathy |
|---|---|---|
| Pressure waveform | "Dip and plateau" or "square root" sign in both ventricles | May have similar pattern but less pronounced |
| Ventricular pressures | Equalization of LV and RV diastolic pressures (within 5 mmHg) | LVEDP exceeds RVEDP by ≥5 mmHg |
| RV systolic pressure | Usually <50 mmHg | Often >50 mmHg |
| Ventricular interdependence | Marked (systolic area index >1.1) | Less prominent |
Clinical Significance
The dip and plateau sign is important because:
- It reflects the fundamental pathophysiology of constrictive pericarditis
- It helps confirm the diagnosis in challenging cases
- It aids in distinguishing constrictive pericarditis from restrictive cardiomyopathy
- It may guide treatment decisions, particularly regarding pericardiectomy
Other Diagnostic Findings
The dip and plateau sign should be interpreted alongside other findings:
- Echocardiography: Septal bounce, respiratory variation of mitral inflow velocity >25%, small ventricles with large atria 1, 2
- CT/MRI: Thickened pericardium (>3mm), pericardial calcifications, tube-like ventricular configuration 1
- Clinical presentation: Signs of right heart failure, jugular venous distension, Kussmaul sign, peripheral edema 2
Pitfalls and Caveats
- The dip and plateau sign may be absent in early or transient forms of constrictive pericarditis
- Normal pericardial thickness does not exclude constrictive pericarditis (absent in 18% of surgically proven cases) 1
- The sign may be less obvious in patients with atrial fibrillation
- In early stages, provocative measures like rapid fluid infusion (1-2L normal saline) may be necessary to elicit the sign 1
Understanding the dip and plateau sign is crucial for the timely diagnosis of constrictive pericarditis, which is essential as pericardiectomy is potentially curative but outcomes worsen with delayed intervention 1.