Related Experiment Videos
Preload dependence of Doppler-derived indexes of left ventricular diastolic function in humans
C Y Choong1, H C Herrmann, A E Weyman
1Department of Medicine, Massachusetts General Hospital, Boston 02114.
Insights
Nitroglycerin reduced filling pressures, improving left ventricular relaxation and altering mitral flow patterns. This suggests filling pressure significantly impacts left ventricular filling dynamics.
Area of Science:
- Cardiology
- Physiology
Background:
- Left ventricular filling is crucial for cardiac function.
- Understanding the impact of filling pressures on diastolic function is important for clinical management.
Purpose of the Study:
- To investigate how reduced filling pressures, induced by nitroglycerin, affect left ventricular filling patterns in humans.
Main Methods:
- Pulsed wave Doppler echocardiography was used to measure mitral flow velocity.
- Measurements were taken during cardiac catheterization in 11 patients before and during nitroglycerin infusion.
Main Results:
- Nitroglycerin decreased mean arterial pressure and pulmonary capillary wedge pressure.
- Left ventricular relaxation (time constant) improved.
- Peak early filling (E) wave velocity decreased, while the contribution of atrial contraction (A) wave to total filling increased.
Conclusions:
- Reduced filling pressures alter left ventricular diastolic filling patterns.
- Nitroglycerin's effects on mitral inflow suggest improved relaxation and a greater reliance on atrial contraction for ventricular filling.
Abstract:
To determine the effect of filling pressure on the pattern of left ventricular filling in humans, the mitral flow velocity profile was measured by pulsed wave Doppler echocardiography during right and left heart catheterization in 11 patients before and during nitroglycerin infusion. Nitroglycerin reduced mean arterial pressure from 90 +/- 9 to 80 +/- 11 mm Hg (p less than 0.001) and mean pulmonary capillary wedge pressure from 9 +/- 4 to 4 +/- 2 mm Hg (p less than 0.001). Cardiac output fell from 6.6 +/- 1.5 to 5.5 +/- 1.4 liters/min (p less than 0.001) and heart rate increased from 60 +/- 13 to 65 +/- 14 beats/min (p less than 0.002). The time constant of isovolumic relaxation (TI.) decreased from 51 +/- 9 to 46 +/- 8 ms (p less than 0.01), indicating faster left ventricular relaxation. Nitroglycerin altered the Doppler characteristics of the early filling (E) wave but not those of the atrial contraction (A) wave. Peak velocity of the E wave decreased from 56 +/- 14 to 44 +/- 9 cm/s (p less than 0.001), peak velocity of the A wave did not change and the ratio of peak velocities of the E and A waves decreased from 0.97 +/- 0.33 to 0.77 +/- 0.20 (p less than 0.02). The deceleration of the E wave decreased from 289 +/- 138 to 186 +/- 71 cm/s2 (p less than 0.02). The ratio of velocity-time integral of the A wave to total velocity-time integral (that is, contribution of atrial contraction to total filling) increased from 0.31 +/- 0.09 to 0.36 +/- 0.08 (p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)