Superior vena cava Doppler flow velocity patterns in pericardial disease

Doppler superior vena cava (SVC) flow patterns were studied in 34 patients with pericardial disease and in 8 normal adults; the pulse transducer on the echocardiographic instrument was used for respiratory monitoring, rather than a separate nasal thermistor-based device. First expiratory SVC diastolic flow velocities (Dfe) did not differ in normal subjects and patients with hemodynamically insignificant pericardial effusions (23 +/- 3 cm/s and 29 +/- 13 cm/s, difference not significant). Dfe were less than 15 cm/s only in the 14 patients with cardiac tamponade (9 +/- 3 cm/s, p less than 0.01). A ratio of systolic to diastolic flow velocity less than or equal to 1.1 in the first expiratory beat distinguished constrictive pericarditis from all other groups (p less than 0.01), although not from restrictive cardiomyopathy. Expiratory ablation of diastolic SVC flow mimicking cardiac tamponade was not observed in constrictive pericarditis. Respiratory variation in SVC flow velocities was slight in normal subjects and patients with constrictive pericarditis, increased in patients with hemodynamically insignificant pericardial effusions (p less than 0.01) and greatest in patients with cardiac tamponade (p less than 0.01). Quantitative analysis of SVC flow velocity patterns is a useful addition to the echocardiographic evaluation of pericardial disease.