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Left ventricular compliance in acute transmural myocardial infarction in man
Insights
Myocardial infarction significantly alters left ventricular stiffness, impacting cardiac function. Compliance changes vary based on infarct location and severity, affecting ejection fraction.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Recent transmural myocardial infarction can lead to significant changes in left ventricular (LV) mechanical properties.
- Understanding alterations in LV compliance post-infarction is crucial for patient management and prognosis.
Purpose of the Study:
- To evaluate changes in left ventricular compliance after myocardial infarction.
- To assess the relationship between infarct location, stiffness moduli, and LV function.
Main Methods:
- Left heart catheterization and cineangiographic left ventriculography were performed on 130 patients.
- Modulus of chamber stiffness (K) and modulus of muscle stiffness (Laird index) were calculated.
- Patients were grouped based on study timing and infarct characteristics.
Main Results:
- Patients studied before and after infarction showed increased chamber and muscle stiffness.
- LV compliance shifted rightward in anterior infarcts and leftward in posterior infarcts.
- No correlation between asynergy extent and chamber stiffness modulus was found; ejection fraction was higher with reduced compliance.
Conclusions:
- Transmural myocardial infarction alters LV stiffness and compliance.
- Infarct location influences the direction of P-V curve shift, indicating differential effects on LV mechanics.
- Reduced LV compliance post-infarction may be associated with preserved or enhanced ejection fraction in some cases.
Abstract:
130 patients with recent transmural myocardial infarction were studied in order to evaluate changes in left ventricular compliance. Left heart catheterization and cineangiographic left ventriculography were performed. The modulus of chamber stiffness (K) was determined from the slope of the linear relation between volume stiffness (dP/dv) and pressure; the modulus of muscle stiffness was evaluated by the Laird index (asymptotic slope of logP vs log V). Patients were divided in 3 groups: Group A included 5 patients studied before and after myocardial infarction who experienced an increase in the modulus of chamber and muscle stiffness after infarction. Group B included 10 patients who were studied at the onset of infarct and 15 days later: this group demonstrated changes in LV compliance with, most often a rightwardshift of P-V curve in anterior infarct and inversely a leftward shift in posterior infarction. The 115 patients of Group B are roughly equally distributed in the areas of normal, increased or decreased compliance. Any correlation was found between the extent of asynergy and changes in modulus of chamber stiffness. However, ejection fraction or VCF were higher in patients with a reduction of compliance than in patients with an increase of compliance.