Abstract 3433: The Effect of Normal Pulmonary Arterial Bed Bubble Contrast Conductance and Latency on Bubble Contrast Echocardiography: Does “Any Bubbles” in the left atrium always mean Patent Foramen Ovale (PFO)?

Abstract

BACKGROUND: The presence of a PFO remains a controversial possible mechanism for a significant number of cryptogenic strokes. However, unvalidated and arbitrary criteria of left heart contrast-bubble appearance on echocardiography form the basis for PFO diagnosis, treatment, and research. We postulated that variable conductance of contrast bubbles through the pulmonary artery (PA) vascular bed, as well as bubble latency can result in the misdiagnosis of PFO. METHODS: Consecutive pts (N=50) undergoing PFO closure by intra-cardiac echocardiography (ICE) guided imaging and right heart catheterization were studied. PULMONARY CONDUCTANCE: Prior to septal closure, ICE imaging of the left atrium was performed during selective PA bubble contrast injections (BCI) at baseline and after injection of 200micrograms of nitroprusside (NP). The appearance of left atrial bubbles was quantified by a validated 1–5 grading system (5–100 bubbles) at rest and following NP. A definite NP response was determined to be present if 2 observers agreed there was at least one grade level increase in bubble conductance from rest. PULMONARY LATENCY: 120 seconds after right atrial BCI, trans-tricuspid ICE pulmonic valve imaging was performed for count of residual bubbles as a correlate of bubbles remaining in the PA at rest. RESULTS: Age was 42 ± 18 years; 70% were female. Pulmonary conductance was present in most pts (84% =grade 1–2, 8% =grade 3– 4). Residual bubbles at the pulmonic valve at 2 minutes were common (range 0 –30 bubbles, mean 6.2 ± 6.5; 42% >5 bubbles). “Definite” increase in conductance after NP was present in 38% of pts. The difference between baseline and NP grade agreed with subjective “definitive” change and “no change” readings (1.26 vs −0.03; p=0.0001). Augmentation of pulmonary conductance by NP was significant (grade 1.32 ±.79 vs 1.74 ± 1.1; p=0.0001) and definitive change was more likely in women than in men (45.7% vs 20.0%; p=0.08). CONCLUSION: We conclude that: pulmonary conductance of bubbles is common, variable, modifiable, and more common in women. Bubble latency in the pulmonary system may erroneously augment Valsalva shunt evaluation. Caution should be exercised when equating lower bubble counts on echocardiography with the diagnosis of PFO.