Left-to-right atrial shunting after percutaneous mitral valvuloplasty. Incidence and long-term hemodynamic follow-up.

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Abstract
To assess the incidence and long-term evolution of left-to-right atrial shunting (AS) after the performance of percutaneous mitral valvuloplasty (PMV), venovenous indicator dilution curves and right heart oximetric measurements were obtained in 68 consecutive patients before and after successful PMV. The procedure increased the mitral valve area (p less than 0.0001) and decreased the mitral gradient (p less than 0.0001). No AS was detected before PMV, but it was detected immediately after PMV. Oximetry identified AS in 17 patients (25%), and dilution curves identified AS in an additional 25 (total, 62%). The ratio of mean pulmonary to systemic blood flow (Qp/Qs) was 1.31 +/- 0.2, and in six patients (9%), the ratio was 1.5 or greater. Among nine clinical, 20 hemodynamic, and six procedural variables, stepwise logistic regression analysis selected the following as independent predictors of AS: smaller increases in valve area (p = 0.01) after PMV, absence of previous surgical commissurotomy (p = 0.02), mitral valve calcification (p = 0.02), and smaller left atria (p = 0.06). Among the 33 patients recatheterized at 6 months, oximetry had detected AS in 10, and dilution curves detected AS in an additional nine (total, 58%) immediately after PMV. At 6 months, AS had decreased or disappeared in 14 of these patients (74%), had increased in three (16%), and was unchanged in two (10%). Overall, at 6 months, oximetry identified AS in three patients, and dilution curves identified AS in an additional 13 (total, 48%). AS was detected at 6 months in only three patients but was not detected immediately after PMV. Although AS is very frequent immediately after PMV, Qp/Qs is usually less than 1.5. The appearance of shunting correlates with patient characteristics and with less improvement in valve area after PMV. Atrial shunting usually persists at 6 months, but its severity almost always decreases.