<prompt> The most commonest cause for chronic cor pulmonale isRecurrent pulmonary embolizationCOPDcystic fibrosisBronchial asthma  <response>: Ref Harrison 19 th ed pg 1505 Once patients with chronic pulmonary or pulmonary vascular disease develop cor pulmonale, the prognosis worsens. Although chronic obstructive pulmonary disease COPD and chronic bronchitis are responsible for approximately 50 of the cases of cor pulmonale . 