The effects of breath-holding on pulmonary regurgitation measured by cardiovascular magnetic resonance velocity mapping

BACKGROUND: Pulmonary regurgitation is a common and clinically important residual lesion after repair of tetralogy of Fallot. Cardiovascular magnetic resonance (CMR) phase contrast velocity mapping is widely used for measurement of pulmonary regurgitant fraction. Breath-hold acquisitions, usually acquired during held expiration, are more convenient than the non-breath-hold approach, but we hypothesized that breath-holding might affect the amount of pulmonary regurgitation. METHODS: Forty-three adult patients with a previous repair of tetralogy of Fallot and residual pulmonary regurgitation were investigated with CMR. In each, pulmonary regurgitant fraction was measured from velocity maps transecting the pulmonary trunk, acquired during held expiration, held inspiration, by non-breath-hold acquisition, and also from the difference of right and left ventricular stroke volume measurements. RESULTS: Pulmonary regurgitant fraction was lower when measured by velocity mapping in held expiration compared with held inspiration, non-breath-hold or stroke volume difference (30.8 vs. 37.0, 35.6, 35.4%, p = 0.00017, 0.0035, 0.026). The regurgitant volume was lower in held expiration than in held inspiration (41.9 vs. 48.3, p = 0.0018). Pulmonary forward flow volume was larger during held expiration than during non-breath-hold (132 vs. 124 ml, p = 0.0024). CONCLUSION: Pulmonary regurgitant fraction was significantly lower in held expiration compared with held inspiration, free breathing and stroke volume difference. Altered airway pressure could be a contributory factor. This information is relevant if breath-hold acquisition is to be substituted for non-breath-hold in the investigation of patients with a view to re-intervention.