Related Experiment Videos
Contraction-relaxation coupling and impaired left ventricular performance in coronary surgery patients
S G De Hert1, T C Gillebert, P W Ten Broecke
1Department of Anesthesiology, University of Antwerp, Edegem, Belgium. sdehert@uia.ac.be
Insights
Cardiac systolic load significantly impacts left ventricular (LV) relaxation and contraction. This study found a tight coupling between LV contraction and relaxation, identifying patients with impaired LV performance under increased load.
Area of Science:
- Cardiology
- Cardiac Physiology
- Hemodynamics
Background:
- Left ventricular (LV) relaxation is influenced by myocardial contractility and systolic load.
- A hypothesis proposed a tight coupling between LV contraction and relaxation.
Purpose of the Study:
- To investigate the relationship between changes in LV relaxation and contraction under varying systolic loads.
- To determine if increased load reveals load-dependent impairments in LV performance.
Main Methods:
- Studied 120 coronary surgery patients with preserved ejection fraction.
- Utilized high-fidelity LV pressure tracings and echocardiography.
- Assessed contraction via dP/dt(max) and stroke area; relaxation via R-value.
- Correlated changes using linear regression analysis.
Main Results:
- Leg raising increased systolic LV pressure, with variable changes in dP/dt(max) and stroke area.
- Changes in contraction parameters (dP/dt(max), stroke area) strongly correlated with relaxation parameter R.
- LV performance and relaxation load dependence varied significantly among patients.
Conclusions:
- A tight coupling exists between LV contraction and relaxation.
- Leg raising effectively identifies patients with load-dependent LV performance impairment and increased relaxation load dependence.
Background:
Dependence of left ventricular (LV) relaxation on cardiac systolic load is a function of myocardial contractility. The authors hypothesized that, if a tight coupling would exist between LV contraction and relaxation, the changes in relaxation rate with an increase in cardiac systolic load would be related to the changes in LV contraction.
Methods:
Coronary surgery patients (n = 120) with preoperative ejection fraction >40% were included. High-fidelity LV pressure tracings (n = 120) and transgastric transesophageal echocardiographic data (n = 40) were obtained. Hearts were paced at a fixed rate of 90 beats/min. Effects on contraction were evaluated by analysis of changes in dP/dt(max) and stroke area. Effects on relaxation were assessed by analysis of R (slope of the relation between tau and end-systolic pressure). Correlations were calculated with linear regression analysis using Pearson's coefficient r.
Results:
Baseline LV end-diastolic pressure was 10+/-3 mm Hg (mean +/- SD). During leg raising, systolic LV pressure increased from 93+/-9 to 107+/-11 mm Hg. The change in dP/dt(max) was variable and ranged from -181 to +254 mm Hg/s. A similar variability was observed with the changes in stroke area, which ranged from -2.0 to +5.5 cm2. Changes in dP/dt(max) and in stroke area were closely related to individual R values (r = 0.87, P<0.001; and r = 0.81, P<0.001, respectively) and to corresponding changes in LV end-diastolic pressure (r = 0.81, P< 0.001; and r = 0.74, P<0.001, respectively).
Conclusions:
A tight coupling was observed between contraction and relaxation. Leg raising identified patients who developed a load-dependent impairment of LV performance and increased load dependence of LV relaxation.