The interpretation of left atrial (LA) hemodynamics have become increasingly important since a variety of left atrial interventions in addition to balloon mitral valvuloplasty (BMV) are more commonly being performed in the catheterization laboratory.In contrast to coronary interventions, which are monitored by fluoroscopy, balloon mitral valvuloplasty is guided by hemodynamic, echocardioraphic, and angiographic input during the procedure. From minute to minute during a BMV procedure, the most critical variable to influence decision-making is the left atrial pressure and the left atrial pressure waveform.A pulmonary capillary wedge pressure (PCWP) tracing is inadequate for a number of reasons. While a number of studies have shown a good correlation between PCWP and left atrial pressure (LAP) with or without pulmonary hypertension [1,2], there are substantial data suggesting otherwise. Generally, the PCWP overestimates the LAP and mean transmitral gradient and, as such, the severity of mitral stenosis [3]. The problem of overestimation of the LAP is greatest when there is severe pulmonary hypertension. Despite the appearance of a good PCWP wave form, the PCWP pressure may be a hybrid with the pulmonary artery pressure. Even more so, PCWP is not accurate to assess success of gradient reduction post-BMV [4]. A poor PCWP waveform may be due to improper catheter positioning (overwedging), damping due to a bubble, catheter or pressure line kinking, or inadequate flushing of the fluid path. Good flushing, checking for kinks in tubing, using a stiffer end-hole catheter, and ensuring wedge saturation Ͼ 95% all help to decrease the pitfalls during use of PCWP as a guide during the procedure if LAP cannot be utilized. Direct monitoring of the left atrial pressure by a transseptal puncture is essential for BMV, since the fidelity of the pulmonary wedge pressure is not adequate to reflect hemodynamic events in the left atrium or the relationship between left ventricular and left atrial mechanics. An exception exists among patients with a mechanical aortic valve prosthesis. When BMV is preformed in patients with a mechanical aortic valve prosthesis, monitoring of the transmitral gradient is performed using the PCWP as an approximation of the LAP, and the dilatation balloon catheter itself remains in place in the left ventricle, rather than using a transprosthetic valve pigtail to monitor left ventricular pressure. Normal left atrial pressure is illustrated in Figure 1. Figure 2 shows the disparity between pulmonary wedge pressure and directly recorded left atrial pressure in a patient with mitral regurgitation. The wedge pressure tracing shows a phase delay, with a delayed peak in the v-wave. In addition, there is significant blunting of the magnitude of the v-wave. The most common artifact in a wedge pressure tracing is a false elevation due to contamination of the waveform with pulmonary artery pressure. When the PCWP is used for measurement of mitral valve area, this artifact can result in considerable overestimation of the ...
