Related Experiment Videos
[Determinants of left ventricular inflow: the relation of the transmitral velocity profile to loading conditions]
K Miyaguchi1, S Ogawa, M Iwase
1First Department of Internal Medicine, Nagoya University School of Medicine.
Insights
Left ventricular inflow is complex, influenced by loading conditions and heart rate. The ratio of peak velocities (A/R) is not unidirectional and can return to baseline with cardiac dysfunction.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Diastolic Function
Background:
- Left ventricular inflow dynamics are crucial for cardiac function.
- Understanding factors influencing transmitral flow is essential for diagnosing diastolic dysfunction.
Purpose of the Study:
- To investigate the determinants of left ventricular inflow using hemodynamic and Doppler-derived indices.
- To analyze the relationship between transmitral flow velocity patterns and left ventricular loading conditions.
Main Methods:
- Hemodynamic and transmitral Doppler signals were recorded in anesthetized open-chest dogs.
- Intravenous infusion of low molecular dextran altered loading conditions.
- Analysis included stepwise multiple linear regression of the A/R ratio against various hemodynamic parameters.
Main Results:
- The ratio of peak velocities (A/R) showed a non-linear relationship with left ventricular end-diastolic pressure (LVEDP).
- A/R correlated positively with left ventricular afterload and negatively with LVEDP (preload).
- The time constant T was a positive correlate in the ascending limb of the A/R-LVEDP relationship.
Conclusions:
- Transmitral flow velocity profiles are complexly determined by ventricular loading, heart rate, and diastolic properties.
- The A/R ratio can return to baseline values during cardiac dysfunction, indicating altered systolic and diastolic function.
Abstract:
To clarify the factors controlling left ventricular inflow, hemodynamics and Doppler-derived indices were analyzed in six anesthetized open-chest dogs with intact pericardia. Low molecular dextran was intravenously infused at 1 L/hr. During rapid infusion, an electrocardiographic lead, left ventricular pressure curve, and a transmitral Doppler signal were recorded at various heart rates produced by right atrial pacing. In five of the six dogs, the relationship of the ratio of peak velocity during atrial contraction to that during rapid filling (A/R) and left ventricular end-diastolic pressure (LVEDP) showed a non-linear quadratic curve concave to the LVEDP axis. Data from the ascending and descending limbs of the A/R-LVEDP relationship were subjected to stepwise multiple linear regression analysis (criterion variables: A/R; explanatory variables: peak dP/dt, maximum left ventricular pressure, time constant T, minimum left ventricular pressure, LVEDP, and heart rate). In both limbs, the A/R correlated positively with maximum left ventricular pressure (left ventricular afterload) and negatively with LVEDP (left ventricular preload). The time constant T was selected as a positive correlate only in the ascending limb. The transmitral flow velocity profile is determined in a complex manner by multiple factors, including left ventricular loading conditions and heart rate, as well as the left ventricular diastolic property. It was suggested that the A/R is not altered unidirectionally by the changes in cardiac function and loading conditions, but that it returns to the initial value accompanied by systolic and diastolic cardiac dysfunction.