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Compensatory and noncompensatory left ventricular dilatation after myocardial infarction: time course and hemodynamic
1Department of Medicine, Julius Maximilians University, Würzburg, Germany.
Insights
Left ventricular dilatation after myocardial infarction can be compensatory, but progressive enlargement in large infarctions worsens outcomes. Stroke volume index (SVI) increases with exercise early post-MI but not long-term in large events.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Myocardial Infarction Research
Background:
- Left ventricular dilatation following myocardial infarction (MI) is associated with decreased survival.
- Early post-MI dilatation may serve a compensatory role, creating a discrepancy with long-term prognostic implications.
Purpose of the Study:
- To investigate the temporal changes in left ventricular volumes and hemodynamics after MI.
- To differentiate the compensatory role of dilatation in small versus large MIs.
- To assess the impact of exercise on cardiac function at different stages post-MI.
Main Methods:
- Prospective study of 39 patients with small MI and 37 with large MI.
- Simultaneous volume and hemodynamic measurements at rest and during exercise.
- Measurements taken at 4 days, 4 weeks, and 6 months post-MI.
Main Results:
- In small MIs, end-diastolic volume index (EDVI) decreased, while ejection fraction and stroke volume index (SVI) remained stable.
- In large MIs, end-systolic volume index (ESVI) and EDVI progressively increased from 4 days to 6 months.
- SVI increased with exercise at 4 weeks but not at 6 months in large MIs, despite stable resting SVI beyond 4 weeks.
Conclusions:
- Progressive left ventricular dilatation and remodeling occur in large MIs, unlike in small MIs.
- The compensatory mechanisms observed early post-MI may not be sustained long-term, particularly in large infarctions.
- Exercise-induced augmentation of stroke volume diminishes over time in patients with large MIs, suggesting impaired cardiac reserve.
Abstract:
Survival after myocardial infarction decreases with left ventricular dilatation, although dilatation at 4 weeks was found to be compensatory. To study this apparent discrepancy, prospective simultaneous volume and hemodynamic measurements at rest were extended in 39 patients with small and 37 with large myocardial infarctions from 4 (range 2 to 6) days and 4 (range 3 to 5) weeks to 6 (range 5 to 8) months after myocardial infarction and were repeated during exercise. In small myocardial infarctions, end-diastolic volume index (EDVI) decreased from 4 days to 6 months; ejection fraction, stroke volume index (SVI), and end-systolic volume index (ESVI) remained unchanged. SVI increased during exercise at 4 weeks and at 6 months. In large myocardial infarctions (n = 37) ESVI (4 days = 38 +/- 3, 4 weeks = 47 +/- 3,* 6 months = 52 +/- 3*; *p less than 0.05 versus 4 days) and EDVI (4 days = 72 +/- 3, 4 weeks = 86 +/- 5,* 6 months = 92 +/- 5* ; *p less than 0.05 versus 4 days and p less than 0.05 versus 4 weeks) increased at constant wedge pressure. SVI remained unchanged beyond 4 weeks (4 days = 35 +/- 2, 4 weeks = 42 +/- 2*, 6 months = 42 +/- 2*; *p less than 0.05 versus 4 days) and increased during exercise at 4 weeks (rest = 45 +/- 2, exercise = 55 +/- 3; p less than 0.05) but not at 6 months (rest = 42 +/- 3, exercise = 45 +/- 3; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)