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How rapidly can diastolic function alter with acute afterloading - insights from an experimental closed chest/closed pericardium acute afterload porcine model.

Intro: The speed and timing of changes in diastolic function parameters during acute LV loading/unloading is unknown. Methods: In a closed chest/closed pericardium porcine model, LV systolic pressure was increased by 30% using a transient descending aortic partial balloon inflation. Morphology and mechanical changes were monitored in real time by echocardiography as were changes in left/right heart diastolic pressures by 3 Millar catheters. Simultaneous blood pool and tissue Doppler data (radial+long axis) were acquired during afterload changes. Results: In 7 animals, acute loading consistently induced LV dilatation and rightwards ventricular septal shift due to lateral LV pericardial restraint. This reduced RV volume. Afterload increase caused an immediate decrease in early diastolic filling wave (E) and lateral wall velocity (E'). This was mirrored by an immediate increase in both early diastolic LV (LVDPmin) and LA (LADPmin) pressure (Fig1). Pulmonary vein flow gradually reduced with decreased late flow. The rightwards septal shift induced a small but significant increase in RVDPmin and an increase in mean RA pressure, but failed to increase pulmonary artery pressure. Acute afterload release immediately returned E values to baseline but E' showed a transient further 3 to 5 beat increase before it normalised. Conclusion: Acute afterloading variably elevates all cardiac diastolic pressures and reduces LV relaxation. These early changes in myocardial mechanics occur simultaneous with changes in LVDPmin. Right heart diastolic pressures elevates by septal shift which both reduced RV volume and decreased LV compliance but did not elevate pulmonary pressure. E'/E recovery differed which could be attributed to transient preload changes.

Acute afterload; pressure increase; animal model; diastolic pressures.

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