Effect of cough on coronary perfusion pressure: Does coughing help clear the coronary arteries of angiographic contrast medium?

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Abstract
To evaluate if coughing after coronary angiography improves the pressure gradient to clear contrast medium from the coronary circulation, the effect of a single forceful cough on the coronary perfusion pressure (CPP) was studied, calculated as diastolic aortic minus right atrial pressure. During coughing before angiography in 12 normotensive subjects, right atrial pressure increased more than aortic pressure increased, causing CPP to decrease by 17 .+-. 12 mm Hg (mean .+-. SD, P < 0.0001). Immediately after the cough, aortic pressure was less than before, and CPP was decreased by 9 .+-. 4 mm Hg (P < 0.0001). Increased central venous pressure during coughing was not transmitted beyond the thoracic and abdominal exits. The effects of coughing in 23 patients after coronary angiography, when aortic pressures were as low as 28 mm Hg (mean 64 .+-. 20 mm Hg), were similar to those in normotensive subjects: the CPP decreased by 21 .+-. 14 mm Hg (P < 0.0001) during coughing, and was decreased by 7 .+-. 6 mm Hg (P < 0.0001) after coughing. To study the cause of these effects, 200 forceful coughs in 9 normal subjects were studied with simultaneous transesophageal M-mode echocardiography and Doppler brachial artery pulse velocity recordings. Coughing during diastole did not open the aortic valve but produced a peak of diastolic brachial arterial flow velocity. Flow velocity in the beat after coughing was less than control. In normal subjects, coughing displaces aortic volume peripherally, without producing cardiac output in diastole, and prevents venous outflow, causing the CPP to be decreased during and after the cough. Coughing produces similar decreases in CPP in patients with moderate hypotension after coronary angiography. If coughing helps to clear the coronary arteries of contrast medium in such patients, it does not do so by increasing the CPP.

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