Is constrictive pericarditis always visiible on a heart echo?

No: It can be a difficult diagnosis in some cases.

Difficult diagnosis: First a few definitions because this field is fraught with poor nomenclature: acute pericarditis is most often not diagnosed by echocardiography. Chronic pericarditis which can lead to constriction (also called constrictive pericarditis) can often be suspected on echo (something called ventricular interdependence). Cardiac mri, cardiac ct and cardiac catheterization can help confirm the diagnosis.

Not always: Constrictive pericarditis may be seen with pericardial effusion or thickening ( easily seen on echo) or with a normal thickness of pericardium. In the latter case, it can be detected by echo based on its restriction of cardiac wall motion , however this can be subtle and may be confused with other conditions.