ABSTRACT
Obstruction of flow across the tricuspid valve serves to limit increases in cardiac output and hence exercise tolerance. In addition, mean gradients as low as 5 mmHg (0.7 kPa) result in elevation of RA pressure, especially during expiration. This increase in pressure leads to RA enlargement and is transmitted to the systemic venous circulation. Since diastole is disproportionately shortened with increasing heart rate, tachycardia can produce dramatic increases in the pressure gradient by shortening the time available for antegrade transvalvular flow.
