Muscular subaortic stenosis: the quantitative relationship between systolic anterior motion and the pressure gradient.

Abstract

We performed simultaneous echocardiographic and hemodynamic studies in 11 patients with muscular subaortic stenosis to determine whether systolic anterior motion (SAM) of the anterior mitral leaflet and the pressure gradient are related quantitatively. SAM without septal contact was associated with either no gradient or a small impulse gradient of less than 10 mm Hg. SAM with septal contact was always associated with a pressure gradient of more than 10 mm Hg. The size of the pressure gradient correlated inversely with the time periods: (1) onset of SAM-septal contact (r = .79, p less than .001) and (2) onset of aortic ejection to onset of SAM-septal contact (r = -.89, p less than .001). Size also correlated directly with the time period: (3) duration of SAM-septal contact (r = .80, p less than .001). Thus when the time from the onset of SAM to the onset of SAM-septal contact was long, SAM-septal contact developed late in systole, the duration of SAM-septal contact was brief and the pressure gradient was low. When SAM-septal contact developed in early systole, the duration of SAM-septal contact was long and the pressure gradient was high. With the index of time period (3) divided by time period (1), a regression equation was devised to predict the size of the pressure gradient (pressure gradient [mm Hg] = 25 [ratio] + 25; r = .90, p less than .001; SE +/- 15 mm Hg). The echocardiographic time period index was validated prospectively in nine other patients and the significant correlation with the hemodynamically determined gradient persisted (r = .89, p less than .01). We conclude that SAM and the pressure gradient are related quantitatively in muscular subaortic stenosis. These observations have implications regarding the mechanism and significance of the pressure gradient in muscular subaortic stenosis.

Mechanism of Benefit of Negative Inotropes in Obstructive Hypertrophic Cardiomyopathy

“…That is, the pressure difference is time dependent. 27 This occurs because after mitral-septal contact the pressure difference, the new hydrodynamic force on the obstructing leaflet, forces it further against the septum. This further decreases the orifice size, which further increases the pressure difference.…”

Verapamil prevents silent myocardial perfusion abnormalities during exercise in asymptomatic patients with hypertrophic cardiomyopathy.

“…Because of the lack of important symptoms, the patients did not routinely undergo cardiac catheterization as part of this protocol. The presence of left ventricular outflow obstruction was assessed at cardiac catheterization in three patients and from the M-mode echocardiogram, based on the magnitude and duration of systolic anterior motion of the mitral valve, 14,15 in the other 26 patients. Eleven patients (38%) had evidence of resting left ventricular outflow obstruction.…”

“…Thus, the verapamil dosage at the time of repeat study ranged from 240 to 480 mg/day (mean, 453), and this dosage was maintained for a mean of 6.7 days (range, 2-56) before the repeat study. The verapamil studies were performed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] weeks (mean, 6±5) after the initial control studies.…”

Spontaneous Variability of Left Ventricular Outflow Tract Gradient in Hypertrophic Obstructive Cardiomyopathy

“…An unacceptably high error is induced in the estimation of pressure gradient if the angle between the interrogating ultrasound beam and the direction of blood flow is more than 20 degrees. 20 To limit the influence of this variable on the daily measurements of pressure gradient, all echocardiograms were performed by experienced sonographers who were trained to interrogate the LVOT systolic flow jet from multiple acoustic windows with careful angulation of the transducer to isolate the maximal velocity spectral profile. Aortic valve pressure gradients in a control group of aortic stenosis patients were also studied in a similar manner on 5 consecutive days to determine if the observed variability in pressure gradient found in this study was largely due to technical factors.…”

“…Systolic anterior motion was graded as follows: 0, absent; 1ϩ, present with minimum distance between mitral valve and ventricular septum during systole Ͼ10 mm; 2ϩ, without mitral-septal contact but with a distance Ͻ10 mm between mitral valve and septum; 3ϩ, brief mitral-septal contact (Ͻ30% of echocardiographic systole); and 4ϩ, prolonged mitral-septal contact (Ͼ30% of systole). 20 Provoked pressure gradient was obtained after giving 0.4 mg NTG sublingually. All patients tolerated NTG, except one who refused it due to a history of severe nitrate headaches and alternatively performed the Valsalva maneuver.…”