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Change in (dP/dt)max as an index of myocardial microvascular permeability
Abstract:
We frequently study processes that alter microvascular permeability in the heart. Myocardial microvascular permeability has been estimated by determining the filtration independent reflection coefficient for beta-lipoprotein (sigma beta-LIPO). This technique requires the measurement of myocardial lymph flow rate and the lymph-to-plasma protein concentration ratio. Unfortunately, it is a nonsurvival procedure. An index of myocardial microvascular permeability was needed that could be determined in experimental preparations without sacrificing valuable chronically instrumented animals. We attempted to relate changes in myocardial microvascular permeability and myocardial edema formation to some index of myocardial performance. In 33 acute, anesthetized dogs (with normal or disrupted myocardial microvasculatures), we measured systemic arterial pressure, systemic venous pressure, coronary sinus pressure, left ventricular pressure, the maximum rate of change in left ventricular pressure (dP/dt)max, myocardial lymph flow rate, and myocardial extravascular fluid volume. Following an increase in coronary sinus pressure, the amount of edema fluid entering the myocardium varied as a function of myocardial microvascular permeability. Further, as the heart became edematous, (dP/dt)max changed with respect to time [delta(dP/dt)max/delta t]. Finally, a significant relation was found between sigma beta-LIPO and delta(dP/dt)max/delta t. Since coronary sinus pressure can be elevated and delta(dP/dt)max/delta t can be measured in chronic animals, this technique may be useful for evaluating myocardial microvascular permeability on a long-term survival basis.
Insights
This study introduces a new method to assess heart microvascular permeability without harming animals. Changes in heart function correlate with microvascular permeability, offering a potential long-term survival measurement.
Area of Science:
- Cardiovascular Physiology
- Microvascular Research
- Biomedical Engineering
Background:
- Assessing myocardial microvascular permeability is crucial for understanding heart conditions.
- Current methods, like measuring the reflection coefficient for beta-lipoprotein (sigma beta-LIPO), are invasive and nonsurvival procedures.
- A non-invasive method is needed for chronic animal studies.
Purpose of the Study:
- To develop and validate a new index of myocardial microvascular permeability.
- To correlate changes in myocardial microvascular permeability and edema with myocardial performance.
- To establish a technique for long-term survival assessment of myocardial microvascular permeability.
Main Methods:
- Studied 33 anesthetized dogs with normal or disrupted microvasculatures.
- Measured systemic arterial pressure, venous pressure, coronary sinus pressure, left ventricular pressure, and maximum rate of change in left ventricular pressure (dP/dt)max.
- Quantified myocardial lymph flow rate and extravascular fluid volume.
Main Results:
- Increased coronary sinus pressure led to myocardial edema, varying with microvascular permeability.
- Cardiac edema formation correlated with changes in (dP/dt)max over time [delta(dP/dt)max/delta t].
- A significant relationship was found between sigma beta-LIPO and delta(dP/dt)max/delta t.
Conclusions:
- The change in (dP/dt)max over time [delta(dP/dt)max/delta t] serves as a viable index for myocardial microvascular permeability.
- This non-invasive technique allows for long-term survival evaluation of myocardial microvascular permeability in chronic animal models.
- The findings support using cardiac performance changes to monitor microvascular integrity.
