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Small vessel pathology and coronary hemodynamics in patients with microvascular angina
1Third Department of Internal Medicine, Showa University, School of Medicine, Tokyo, Japan.
Insights
Microvascular angina patients show cardiac microcirculation disturbances. These include narrowed small arteries and capillary changes, leading to ischemic electrocardiogram changes.
Area of Science:
- Cardiology
- Vascular Biology
- Pathology
Background:
- Microvascular angina presents with ischemic symptoms despite normal coronary arteriograms.
- The underlying pathophysiology of microvascular angina remains incompletely understood.
Purpose of the Study:
- To investigate the ultrastructural changes in cardiac myocytes and small blood vessels in patients with microvascular angina.
Main Methods:
- Endomyocardial biopsies from 21 patients with microvascular angina were analyzed.
- Light and electron microscopy were used to examine tissue ultrastructure.
- Coronary sinus blood flow and myocardial oxygen consumption were measured during atrial pacing.
Main Results:
- All patients exhibited ischemic ST segment depression during pacing.
- Light microscopy revealed myocardial hypertrophy, small artery sclerosis, and perivascular fibrosis in 95% of patients.
- Electron microscopy showed swollen endothelial nuclei in capillaries and narrowed lumina in small arteries due to smooth muscle cell abnormalities.
Conclusions:
- Disturbances in the coronary microcirculation, including arteriolar and capillary abnormalities, are implicated in microvascular angina.
- These microcirculatory changes likely contribute to the observed ischemic electrocardiogram findings.
Abstract:
We studied the ultrastructure of cardiac myocytes and small blood vessels obtained by endomyocardial biopsy from 21 patients with microvascular angina. Ischemic ST segment depression during atrial pacing was recognised in all the patients who had normal coronary arteriograms and biopsy tissues were examined by light and electron microscopy. In patients with microvascular angina, insufficient increases in coronary sinus blood flow and in myocardial oxygen consumption measured with a Webster's catheter were apparent during atrial pacing. Biopsy samples under the light microscope showed evidence of myocardial hypertrophy and sclerosis of small arteries and arterioles with perivascular fibrosis in 18 of 19 (95%) patients. Electron microscopy revealed that many endothelial nuclei in capillaries were swollen and that lumina of small arteries and arterioles were irregularly narrowed with proliferated and deformed medial smooth muscle cells. These findings suggest that disturbances in the coronary microcirculation in these patients is responsible for the ischemic changes in electrocardiograms.