Background The Frank-Starling law describes the relation between left ventricular volume and function. However, little studies described the relation between left atrial volume (LAV) and function.
Aim To describe a LA Frank-Starling law by studying changes in LAV measured by real-time three-dimensional echocardiography (RT3DE).
Methods In seventy patients LAV was calculated by RT3DE at end-systole (Vmax), end-diastole (Vmin) and pre-atrial contraction (Vpre-A). According to Vmax, patients were classified into three groups: Vmax <50 ml (Group I), Vmax 50 to 70 ml (Group II), and Vmax >70 ml (Group III). Calculated indices of LA pump function were active atrial stroke volume (AA-SV) defined as Vpre-A ¡V Vmin and active atrial emptying fraction (AA-EF), defined as AA-SV / Vpre-A x 100%
Results AA-SV increased from Group I to Group II (8.2,,4.9 vs. 19.0,,b 9.2 ml, P <0.0001), but (non-significantly) decreased from Group II to Group III (19.0,,b 9.2 vs. 16.7,,b 12.5 ml). AA-SV was well correlated with Vpre-A (r = 0.56, P <0.0001), but decreased with larger Vpre-A. AA-EF tended to increase from Group I to Group II (33.2,,b 17.5 vs. 43.1,,b 18.2, P < 0.10), but decreased from Group II to Group III (43.1,,b 18.2 vs. 26.2,,b 18.5, P <0.01).
Conclusion A Frank-Starling mechanism could be described by RT3DE and evidenced by an increase in LA contractility in response to an increase in LA preload up to a point, beyond which LA contractility decreased.
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