Therefore, in patients with AS, percutaneous aortic balloon dilation is not a substitute for AVR. Some clinicians contend that, despite the procedural morbid- ity and mortality rates and limited long-term results, percutaneous aortic balloon dilation can have a temporary role in the management of some symptomatic patients, such as those patients with severe AS and refractory pulmo- nary edema or cardiogenic shock, who might benefit from percutaneous aortic balloon dila- tion as a bridge to TAVI or SAVR. However, this approach is used less frequently given the availability and success of immediate TAVI even in very high-risk patients (Table 14).35 38 4. AORTIC REGURGITATION 4.1. Acute Aortic Regurgitation Acute aortic regurgitation (AR) may result from abnor- malities of the valve, most often endocarditis, or abnor- malities of the aorta, primarily aortic dissection. Acute AR may also occur as an iatrogenic complication of a transcatheter procedure or after blunt chest trauma. The acute volume overload on the LV usually results in severe pulmonary congestion, as well as a low forward cardiac output. Urgent diagnosis and rapid intervention are lifesaving. 4.1.1. Diagnosis of Acute AR TTE or TEE is indispensable in confirming the pres- ence, severity, and etiology of acute AR; determining whether there is rapid equilibration of the aortic and LV diastolic pressures; visualizing the aortic root; and evaluating LV size and systolic function.1,2 A short deceleration time on the aortic flow velocity curve and early closure of the mitral valve are indicators of markedly elevated LV end-diastolic pressure. A pres- sure half-time of <300 ms on the AR velocity curve indicates rapid equilibration of the aortic and LV diastolic pressures. The degree of holodiastolic flow reversal in the aortic arch, in comparison with the forward systolic flow, provides a quick semiquantita- tive estimate of regurgitant fraction. 