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Abnormal myocardial blood flow distribution in patients with angina pectoris and normal coronary arteriograms
A Shiraishi1, H Ikeda, N Haramaki
1Department of Internal Medicine III, Kurume University School of Medicine, Japan.
Insights
Patients with syndrome X experience chest pain and ST-segment depression during exercise due to impaired coronary microvascular function. This study shows abnormal myocardial blood flow distribution in syndrome X patients, contributing to their symptoms.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Syndrome X, characterized by chest pain and normal coronary arteries, presents a diagnostic challenge.
- Coronary microvascular dysfunction is a suspected cause of symptoms in Syndrome X.
Purpose of the Study:
- To evaluate coronary microvascular function in patients with Syndrome X.
- To determine the relationship between myocardial blood flow distribution and exercise-induced chest pain and ST-segment depression.
Main Methods:
- Quantitative assessment of transmural myocardial blood flow distribution using 2-dimensional myocardial contrast echocardiography.
- Measurement of the endocardial to epicardial gray level ratio in the left anterior descending coronary artery territory before and after pacing stress.
- Comparison between 11 patients with Syndrome X and 14 control subjects.
Main Results:
- Syndrome X patients exhibited pacing-induced chest pain and ST-segment depression, unlike controls.
- The endocardial/epicardial gray level ratio significantly decreased in Syndrome X patients post-pacing (0.98 to 0.76, p<0.01).
- No significant change in the endocardial/epicardial ratio was observed in controls post-pacing (0.97 to 0.99, NS).
Conclusions:
- Abnormal myocardial blood flow distribution during stress is a key factor in exercise-induced chest pain and ST-segment depression in Syndrome X.
- Coronary microvascular dysfunction plays a significant role in the pathophysiology of Syndrome X.
Abstract:
To evaluate coronary microvascular function and its relation to the genesis of chest pain and ST-segment depression during exercise in patients with syndrome X, pacing-induced changes in transmural myocardial blood flow distribution were quantitatively assessed by 2-dimensional myocardial contrast echocardiography. Of 25 patients with a history of chest pain and normal coronary arteries with the negative ergonovine test, 11 had exercise-induced chest pain and ST-segment depression (syndrome X), and 14 did not (controls). Myocardial blood flow distribution before and after pacing stress was assessed by measuring the ratio of the endocardial to epicardial gray level (ie, endo/epi gray level ratio) in the territory of the left anterior descending coronary artery. Pacing-induced chest pain and ST-segment depression were observed in syndrome X, but not in controls. The endo/epi gray level ratio in syndrome X significantly decreased after pacing (from 0.98+/-0.10 to 0.76+/-0.17, p<0.01), but not in controls (from 0.97+/-0.08 to 0.99+/-0.08, NS). Abnormal myocardial blood flow distribution may play an important role in exercise-induced chest pain and ST-segment depression in these patients.