CHAPTER 76: COR PULMONALE: THE HEART IN PARENCHYMAL LUNG DISEASE

INTRODUCTION

Cor pulmonale, or “pulmonary heart,” describes the pathological changes and associated signs and symptoms of right ventricular failure resulting from pulmonary hypertension (PH) in the setting of parenchymal lung disease such as chronic obstructive pulmonary disease (COPD).¹

The pulmonary circulation (with the exception of the bronchial arteries, which deliver oxygenated blood from the left heart) is characterized not only by the delivery of venous deoxygenated blood to the alveoli for oxygen uptake, but also by low resistance and large capacitance. The pulmonary circulation in the absence of right-to-left shunts has to accept the entire cardiac output, approximately 5 L/min at rest and up to fivefold during maximal exercise. Normal mean pulmonary pressure is less than 20 mm Hg at rest, with a level greater than 25 mm Hg diagnostic of PH.² Although pulmonary pressures do rise with exercise, pulmonary vascular resistance (PVR) normally drops further with exercise to accommodate the marked increase in cardiac output. In PH, although there is an exaggerated increase in pulmonary pressures during exercise without an appropriate decrease in PVR, criteria for exercise-induced PH have not been established.² To accommodate the large amount of blood flow, the pulmonary circulation provides a large cross-sectional area. Reduction in the cross-sectional area by up to 50%, as with a pneumonectomy, is well tolerated without PH at rest. Further reductions, as may occur with advanced pulmonary disease, can lead to PH both on exertion and at rest with resultant pressure overload on the right ventricle.

The term cor pulmonale originated over two centuries ago and has been applied variably in the past to right heart failure as a result of various lung conditions, both parenchymal and vascular in origin, as well as a result of pulmonary emboli. Indeed, from a pathophysiologic and clinical standpoint, any disease in which pulmonary arterial pressures increase sufficiently to affect right ventricular function results in a similar clinical syndrome of right heart failure. In 1963, the World Health Organization (WHO) defined cor pulmonale as “hypertrophy of the right ventricle resulting from diseases affecting the function and/or structure of the lungs.”³ Strictly speaking, therefore, the term should be applied only to group III PH and excludes group I (pulmonary arterial hypertension, including idiopathic pulmonary arterial hypertension, connective tissue diseases, and congenital heart disease), group II (secondary to left heart failure), group IV caused by chronic thromboembolic disease, and group V (miscellaneous conditions such as sarcoidosis) based on the 2013 Updated Clinical Classification of Pulmonary Hypertension.⁴ PH is discussed in detail in Chap. 74.

Chronic cor pulmonale is typically a manifestation of various parenchymal lung diseases. Acute pulmonary embolism, if large, leads to acute right heart failure, which has been termed by some as acute cor pulmonale. Pulmonary embolism is not an intrinsic lung disease, and as such, the term is not strictly within the definition used here for cor pulmonale. The ...