Left atrium (LA), left ventricle (LV), and ascending aorta (Ao) demonstrating the hemodynamic variables used for characterization of diastolic function. (a) Minimum LV pressure; (b) LV pre-A pressure; (c) end-diastolic pressure, LV end-diastolic pressure; (d) LV diastolic filling period; (e) LA peak A wave pressure; (f) V wave height; (g) LA peak V wave pressure; (h) isovolumic relaxation period.

(A) Change in left ventricular outflow tract (LVOT) gradient with septal ablation, (B) change in left atrial pressure (LAP) with septal ablation, and (C) the relation between change in LVOT gradient and change in LAP with septal ablation. Septal ablation resulted in variable effects on left atrial pressure, which correlated with the extent of LVOT gradient reduction. Closed circles = patients with resting LVOT gradients of 40 mm Hg; open circles = patients with resting LVOT gradients of <40 mm Hg.

The effect of septal ablation on minimum left ventricular pressure (A) and the time constant of mycardial relaxation (tau) (B) varied according to the extent of left ventricular outflow tract (LVOT) gradient reduction. Furthermore, the effects on minimum left ventricular pressure and tau were directly related to the changes in left atrial pressure from septal ablation (C and D). Closed circles = patients with resting LVOT gradients of 40 mm Hg; open circles = patients with resting LVOT gradients of <40 mm Hg.

(A) The patient was a 56-year-old woman with a marked increase in the left ventricular outflow tract gradient. After septal ablation, there were acute decreases in tau (the time constant of myocardial relaxation), minimum left ventricular pressure, and left atrial pressure. (B) Similarly, in this 62-year-old man with a left ventricular outflow tract gradient of 113 mm Hg, septal ablation resulted improvement in myocardial relaxation and left atrial pressure. (C and D) Two patients (a 71-year-old man and a 67-year-old man, respectively) who had relatively lower left ventricular outflow tract gradients. Septal ablation resulted in acute prolongation of tau and elevation in ventricular filling pressures in both of these patients. LAP = left arterial pressure; LV-MIN = minimum left ventricular diastolic pressure; other abbreviations as in Figure 1.

Only 2 patients had LVOT gradient <50 mm Hg and grade III or IV mitral regurgitation. However, as shown in (A), septal ablation led to decreases in left atrial pressure in patients with gradient 50 mm Hg independently of the severity of MR, whereas those patients with LVOT gradient <50 mm Hg more commonly had increases in left atrial pressure. *p = 0.002 and **p = 0.03 for comparison versus LVOT gradient <50 mm Hg and grade I or II mitral regurgitation. Furthermore, as shown in (B), improvement in tau (the time constant of myocardial relaxation) was observed in patients with gradients 50 mm Hg independently of the severity of MR. However, prolongation of tau more frequently occurred in those patients with gradients <50 mm Hg. *p = 0.006 and **p = 0.03 for comparisons versus LVOT gradient <50 mm Hg and grade I or II mitral regurgitation. All other comparisons were not statistically significant. LVOT = left ventricular outflow tract; MR = myocardial relaxation.