Bidirectional Ventricular Septal Defect Shunt: Quantification Technique Using Stress Pulsed Wave Doppler Echocardiography

Purpose: Doppler echocardiography is a sensitive method for diagnosing ventricular septal defect (VSD).In case of bi-directional flow across VSD, we did not identify any study that used velocity time integral to access volume of shunt across VSD during rest/exercise.We identified a case of 28 year old man with bi-directional flow across VSD who presented with unexplained syncopial attacks.Methods: We carried out an Exercise Stress Echocardiogram using WHO protocol.We used colour doppler across inter-ventricular septum to identify the VSD.Sample volume was then placed through VSD to obtain pulsed doppler images at rest and at peak exercise.We averaged all velocity time integrals (VTI) obtained for five cardiac cycles.Results: On exercise he managed stage one of the protocol and achieved 75% of maximum predicted target heart rate.His oxygenation dropped from 93% to 74% on air.However, the pulmonary systolic pressure increased from 63mmHg to 104mmHg.The contraction of the right ventricle increased appropriately with exercise.Averaged VTI at rest for left to right (L-R) shunt was 26.32cm and at stress was 21.6cm.Similarly VTI at rest for right to left shunt (R-L) was 78.08cm and at stress was 79.44cm.Absolute change of VTI ratio during exercise was equal to 0.71 (3.67-2.96).This is equal to 24% increase in ratio of VTIs during stress. Conclusion:According to VTI assessment of bi-directional VSD there was significant worsening of right to left shunt during exercise secondary to increase pulmonary vascular resistance on exercise.This was de-stabilizing his oxygenation and led to syncopial attacks.This case highlights use of Doppler pulsed-wave echocardiography in haemodynamic assessment of bi-directional VSD.