Negative intrathoracic pressure induced by the Müller maneuver significantly decreased the left ventricular outflow tract gradient from 69 to 7 mm Hg (p<0.001) in muscular subaortic stenosis.
Observational (n=9)
Do respiratory maneuvers that produce negative intrathoracic pressure reduce the left ventricular outflow tract gradient in patients with muscular subaortic stenosis?
Negative intrathoracic pressure significantly reduces the left ventricular outflow tract gradient in patients with muscular subaortic stenosis, likely by increasing left ventricular afterload.
Absolute Event Rate: 7% vs 69%
p-value: p=<0.001
To study the effect of respiration and negative intrathoracic pressure on the left ventricular outflow tract gradient in patients with muscular subaortic stenosis, we studied nine patients using various respiratory maneuvers at the time of cardiac catheterization. Deep inspiration decreased the left ventricular outflow tract gradient from 60 +/- 11 to 34 +/- 6 mm Hg (p less than 0.01) and decreased the left ventricular ejection time (corrected for heart rate) from 0.42 +/- 0.01 to 0.38 +/- 0.01 second (p less than 0.001). The Müller maneuver decreased the left ventricular outflow tract gradient from 69 +/- 13 to 7 +/- 3 mm Hg (p less than 0.001) and decreased the corrected left ventricular ejection time from 0.42 +/- 0.02 to 0.24 +/- 0.01 second (p less than 0.01). In keeping with this amelioration of left ventricular outflow tract obstruction, echocardiography showed a reduction or abolition of the systolic anterior motion of the anterior mitral leaflet, and auscultatory and phonocardiographic studies revealed a decrease or abolition of the apical systolic murmur. These findings indicate that negative intrathoracic pressure reduced the left ventricular outflow tract gradient in muscular subaortic stenosis. We believe that negative intrathoracic pressure produced these changes by increasing left ventricular afterload through an increase in left ventricular transmural pressure, resulting in a decrease in the left ventricular outflow tract obstruction. These observations provide an explanation for the decrease in pressure gradient that occurs on inspiration in patients with muscular subaortic stenosis.
Buda et al. (Wed,) conducted a observational in Muscular subaortic stenosis (n=9). Negative intrathoracic pressure (Müller maneuver and deep inspiration) vs. Baseline was evaluated on Left ventricular outflow tract gradient (p=<0.001). Negative intrathoracic pressure induced by the Müller maneuver significantly decreased the left ventricular outflow tract gradient from 69 to 7 mm Hg (p<0.001) in muscular subaortic stenosis.