REGIONAL PULMONARY VASOCONSTRICTION AS AN INDIVIDUAL FACTOR IN GENESIS OF COR PULMONALE

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Abstract
Fifty-eight patients with obstructive lung disease were classified as responders (39) or nonresponders (19), based on the presence or absence of a significant increase in physiologic dead space/tidal volume ratio when they breathed O2. Ecg evidence of right-sided cardiac abnormality and the presence of a history of heart failure were compared in responders and nonresponders. There was no significant difference in the incidence of relevant ecg changes or a history of heart failure between the 2 groups. Responders showed each variety of abnormality at a higher mean forced expiratory volume in 1 sec. (FEV1), a higher mean arterial O2 saturation (SaO2), and a lower mean arterial CO2 tension (PacO2) than did nonresponders. At FEV1 levels of less than 0.75 1, ecg abnormalities and a history of heart failure were common in both groups. At FEV1 levels of more than 0.75 1, ecg abnormalities and a history of heart failure were seen only in responders. Responders may correspond to those normal subjects who show brisk pulmonary vascular reactivity to hypoxia, and when obstructive lung disease supervenes, regional vasoconstriction occurs in the poorly ventilated regions of their lungs; nonresponders may correspond to those normal subjects who fail to show a brisk pulmonary vascular response to hypoxia. Regional pulmonary vasoconstriction may determine the onset of right heart changes at an earlier stage of the lung disease among responders than among nonresponders and at the same time preserve blood gas tensions at better levels.