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Angina due to coronary microvascular disease in hypertensive patients without left ventricular hypertrophy
J E Brush1, R O Cannon, W H Schenke
1Cardiology Branch, National Heart, Lung, and Blood Institute, Bethesda, Md.
Insights
Hypertension can cause angina due to coronary microvascular dysfunction, not just blockages. This study found abnormal blood vessel responses in hypertensive patients with angina, indicating microvascular issues contribute to myocardial ischemia.
Area of Science:
- Cardiology
- Hypertension Research
- Vascular Biology
Background:
- Angina in hypertensive patients is often linked to coronary artery disease or left ventricular hypertrophy.
- Coronary microvascular abnormalities may also contribute to angina in this population.
- This study investigates the role of microvascular function in hypertensive patients experiencing angina without significant epicardial coronary disease.
Purpose of the Study:
- To determine the contribution of coronary microvascular abnormalities to angina in hypertensive patients.
- To evaluate coronary responses to rapid atrial pacing and ergonovine administration in hypertensive patients with and without angina.
- To compare these responses with those of normotensive subjects.
Main Methods:
- Evaluated 12 hypertensive patients with pacing-induced angina and 13 normotensive controls.
- Measured coronary flow and resistance using rapid atrial pacing before and after ergonovine administration.
- Assessed myocardial oxygen extraction and lactate consumption during pacing.
Main Results:
- Hypertensive patients with angina showed a blunted increase in coronary flow during pacing compared to normotensive subjects (48% vs. 83%).
- Ergonovine administration induced vasoconstriction in hypertensive patients, with a reduced coronary flow increase (32%) and coronary resistance decrease (15%).
- Normotensive subjects exhibited a significantly greater coronary flow increase (112%) after ergonovine and pacing.
Conclusions:
- Angina in hypertensive patients without epicardial coronary disease can be caused by myocardial ischemia.
- This ischemia appears to result from abnormally elevated resistance in the coronary microvasculature.
- Coronary microvascular dysfunction is a significant factor in angina presentation among hypertensive individuals.
Abstract:
When angina occurs in patients with hypertension, it is usually attributed to coronary artery disease or left ventricular hypertrophy. To determine the contribution of coronary microvascular abnormalities to angina in patients with hypertension, we evaluated hypertensive patients without coronary artery disease or left ventricular hypertrophy by measuring the coronary responses to rapid atrial pacing before and after administration of ergonovine. We compared 12 hypertensive patients who had pacing-induced angina with 13 normotensive subjects without such angina. The two groups had similar coronary flow (in the great cardiac vein) at rest; however, pacing increased coronary flow less in hypertensive patients with angina than in normotensive subjects (48 vs. 83 percent; P = 0.05). In the hypertensive patients with angina, pacing after ergonovine increased coronary flow by only 32 percent (as compared with 48 percent before ergonovine; P less than 0.05) and decreased coronary resistance by 15 percent (as compared with 28 percent before ergonovine; P less than 0.05), indicating the presence of ergonovine-induced vasoconstriction. In normotensive subjects, in contrast, cardiac pacing after ergonovine increased coronary flow by 112 percent (P less than 0.001), and its effect on coronary resistance was not different from that of pacing before ergonovine. The hypertensive patients with angina had a significant increase in myocardial oxygen extraction during pacing after ergonovine and less of an increase in myocardial lactate consumption - a response consistent with the presence of myocardial ischemia. Thus, angina in hypertensive patients without epicardial coronary disease may be caused by myocardial ischemia, which appears to be due to an abnormally elevated resistance of the coronary microvasculature.