Carvallo’s sign occurs when the murmur of tricuspid valve regurgitation gets louder with deep inspiration. This, as well as the location of the murmur, helps to distinguish tricuspid regurgitation from mitral regurgitation. Deep inspiration lowers intrathoracic pressures causing increased venous return to the right heart. Since there is more volume in the right heart, the regurgitant volume in the presence of tricuspid regurgitation increases, thus increasing the intensity of the murmur.