High-density contrast echocardiography for patent foramen ovale assessment: sensitivity and relationship with invasively measured shunt severity and atrial septum morphology

BACKGROUND: Transthoracic contrast echocardiography (cTTE) is a first-line method for patent foramen ovale (PFO) assessment, but its sensitivity is reported as low and inconsistent. We aimed to investigate the sensitivity of high-density cTTE for PFO detection, and the relationship between left-heart contrast opacification grade, invasively measured shunt severity and atrial septum/PFO morphology. METHODS: Fifty-five consecutive patients with proven PFO on contrast transoesophageal echocardiography (cTOE) underwent cTTE with high density contrast (colloid, mannitol) and invasive quantification of right-to-left shunt severity using the thermodilution method. Echocardiographic shunt severity was classified according to the degree of left atrial (cTOE) or left atrial/ventricular (cTTE) opacification as grade 0 (no bubbles), grade 1(mild), grade 2 (moderate) grade 3 (significant opacification). RESULTS: For PFO detection, the sensitivity of rest + Valsalva cTOE was 100%. Compared with this reference, sensitivity of rest + Valsalva cTTE was 98.2%, Valsalva cTTE 97.7%, rest cTTE, 83.9% and rest cTOE, 77.3%. No significant association was observed between left-heart opacification grade on rest or Valsalva cTTE/cTOE and invasively measured right-to-left shunt severity categorized as < 10%, 10-19%, or ≥ 20% (p = 0.10-0.26). A moderate association only was identified between rest + Valsalva cTOE left atrium opacification grade and < 10% and ≥ 10% right-to-left shunt severity (p = 0.024, Cramér's coefficient = 0.368). No significant relationship was found between left-heart opacification grade and the presence of atrial septal aneurysm, Eustachian valve/Chiari's network, or PFO channel width and length (p = 0.45-0.77). Compared with rest cTOE, rest cTTE demonstrated equal contrast opacification grade in 56% and higher in 40%. Valsalva cTTE showed equal contrast opacification grade in 29% and higher in 46% of studies vs. Valsalva cTOE. CONCLUSIONS: In studies using high-density contrast, cTOE and cTTE with Valsalva, but not rest studies, are highly sensitive for PFO assessment. There is no clinically relevant relationship between the left-heart bubble opacification grade and invasively measured right-to-left shunt severity or atrial septum morphology. The left-heart contrast opacification grade is equal to or higher in cTTE than in cTOE, especially in rest studies.