Qp/Qs Ratio Calculator
- Qp Qs Ratio Calculator Summary and Clinical Context
The Qp Qs ratio is a Doppler based calculation used to quantify the relationship between pulmonary blood flow and systemic blood flow. It is an essential parameter when evaluating patients with suspected intracardiac shunts such as atrial septal defect, ventricular septal defect, or patent ductus arteriosus. Doppler echocardiography provides a noninvasive method to estimate these flows by combining the velocity time integral with the cross sectional area of the outflow tracts. A ratio greater than one suggests that pulmonary blood flow exceeds systemic blood flow, which is consistent with a left to right shunt. Conversely, a ratio less than one indicates a right to left shunt which is typically associated with advanced pulmonary vascular disease or complex congenital lesions. In clinical practice, a ratio of one indicates balanced flow without evidence of significant shunting. A Qp Qs ratio of at least one point five is commonly used as a threshold for recommending closure of certain defects such as secundum atrial septal defect when accompanied by right ventricular enlargement. Interpretation must always be combined with clinical assessment, chamber size evaluation, and hemodynamic significance.
References
Rudski L, Lai W, Afilalo J et al. Guidelines for the echocardiographic assessment of the right heart in adults. Journal of the American Society of Echocardiography 2010.
Baumgartner H, De Backer J, Babu Narayan S et al. ESC Guidelines for the management of adult congenital heart disease. European Heart Journal 2020.
Otto C and Prendergast B. Textbook of Clinical Echocardiography. Fifth Edition. Elsevier.
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