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Mechanism of augmented left atrial pump function in myocardial infarction and essential hypertension evaluated by
M Matsuzaki1, M Tamitani, Y Toma
1Second Department of Internal Medicine, Yamaguchi University School of Medicine, Japan.
Insights
Essential hypertension and myocardial infarction impair left atrial (LA) pump function, indicated by increased LA dimension and A loop area. These conditions alter LA mechanics, affecting its pumping efficiency.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Left atrial (LA) function is crucial for maintaining cardiac output.
- Essential hypertension and myocardial infarction are common conditions that can affect cardiac structure and function.
Purpose of the Study:
- To analyze and compare left atrial (LA) pump function in normal subjects, patients with essential hypertension, and patients with healed myocardial infarction.
Main Methods:
- Simultaneous recording of LA dimension (aortic-root echogram) and pressure (catheter-tip manometer) in 25 patients.
- Analysis of the LA pressure-dimension relation, focusing on the A loop representing pump function.
Main Results:
- LA dimension at the start of active shortening was significantly greater in hypertensive and myocardial infarction patients compared to normal subjects.
- The area of the A loop, reflecting LA pump function, was significantly increased in hypertensive and myocardial infarction patients.
- Mean fractional shortening velocity of the LA increased in hypertensive subjects, while LA peak wall tension increased in both hypertensive and myocardial infarction groups.
Conclusions:
- Essential hypertension and healed myocardial infarction significantly alter left atrial (LA) pump function.
- These conditions lead to increased LA dimensions, altered pressure-dimension loops, and increased wall tension, indicating impaired LA mechanics.
Abstract:
To analyze left atrial (LA) pump function in normal subjects, in patients with essential hypertension and in patients with a healed myocardial infarction, LA dimension (aortic-root echogram) and pressure (catheter-tip manometer) were simultaneously recorded in 25 patients (8 normal subjects, 7 with hypertension and 10 with myocardial infarction). The pressure-dimension relation of the left atrium was composed of 2 loops: the A loop (expressing the pump function of the left atrium) and the V loop. LA dimension at the beginning of active LA shortening was significantly greater in hypertensive subjects (33 +/- 3 mm) and in those with myocardial infarction (32 +/- 4 mm) than in normal subjects (28 +/- 3 mm) (p less than 0.01, p less than 0.05, respectively). The area of the A loop significantly increased in subjects with hypertension (48 +/- 3 mm Hg.mm, p less than 0.01) and in subjects with myocardial infarction (29 +/- 10 mm Hg.mm, p less than 0.05), compared with normal subjects (20 +/- 8 mm Hg.mm). The mean fractional shortening velocity of the left atrium significantly increased in subjects with hypertension, compared with normal subjects and those with myocardial infarction (p less than 0.05 for both). LA peak wall tension during the LA active contraction period significantly increased with hypertension and with myocardial infarction, compared with normal subjects (p less than 0.01, p less than 0.05, respectively). The area of the A loop was directly proportional to the LA dimension at the beginning of active LA shortening (r = 0.53), p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)