Kussmaul sign is a paradoxical rising of jugular venous pressure during inspiration due to restricted late ventricular filling. It is commonly seen in constrictive pericarditis.
How did it happen?
Right ventricular dysfunction –> impair right ventricular filling –> raise atrial pressure
The inability for cardiac chambers to expand due to hypoelasticity or inelasticity of the myocardium caused by conditions such as infection and fibrosis (restrictive cardiomyopathy) mechanical compartmentalization by constrictive pericardial diseases (constrictive pericarditis), or impaired right ventricular function resulting from right-sided myocardial infarction, impede effective right ventricular filling and cause a paradoxical increase in jugular venous pressure during inspiration.
Thus, Kussmaul’s sign is seen in conditions that restrict right ventricular filling. For instance, constrictive pericarditis, right-sided heart failure, right-sided heart infarction, tricuspid stenosis and massive pulmonary embolism. Therefore, conditions that raise right atrial and venous pressure are a prerequisite to cause Kussmaul’s sign.
Do take note that Kussmaul sign may also be seen in restrictive cardiomyopathy.
But, Kussmaul sign is NOT seen in cardiac tamponade!!!
Even though the increase in pericardial pressure exerts an inward force compressing the entire heart during inspiration, the increase in negative intrathoracic pressure is still able to be transmitted to the right side of the heart and subsequent increase in blood flow to the right atrium ensues.
Conversely, the restriction to diastolic filling of the right ventricle in constrictive pericarditis and restrictive cardiomyopathy by the fixed, less compliant constricting pericardium or myocardium respectively at higher chamber volumes, results in the paradoxical increase in jugular venous pressure referred to as Kussmaul’s sign.