Orthopnea is a classical sign of established CHF.
While paroxysmal nocturnal dyspnea is an early sign of cardiac failure,orthopnea is a late manifestation of cardiac failure .This symptom was mainly attributed to volume displacement from systemic venous to pulmonary circulation when the patient goes to recumbent posture.The exact mechanism of this has been speculative. Now with liberal usage of bedside echocardiography, we have found out there is postural variation in the diastolic function of the failing left venticle.
Many patients develop a restrictive ventricular filling pattern in recumbent posture (Grade 3 diastolic dysfunction). While sitting up some of them revert to normal or downgrade to grade 1 diastolic dysfunctionThis observation proves another fact that every patient with severe systolic dysfunction also has significant diastolic dysfunction at some point in their course of illness.
Dr.S.Venkatesan MD 
hello sir,
i am a student of 2nd mbbs studying at rims raichur,karnataka
can you please give more information about mechanism behind orthopnea and pnd???
if a patient comes with the complaints of cough with hemoptysis,orthopnea and chest pain it should be considered as a rs case or cvs case???
i think on attaining recumbent posture there is increase in LV preload. and on sitting LV preload reduction is known as it is used to augment murmurs of HOCM and MVP. So the changes in MV inflow pattern are related to changes in preload only! Dr U P Singh MD DM