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Coronary microvascular dysfunction is associated with ischemic-like electrocardiogram during exercise in patients
1Department of Medicine, Veterans General Hospital-Taipei, Taiwan, Republic of China.
Insights
Coronary microvascular dysfunction, not altered metabolism, may cause exercise-induced chest pain and ECG changes in patients with normal coronary angiograms. This finding is crucial for understanding angina of unknown origin.
Area of Science:
- Cardiology
- Physiology
Background:
- Anginal chest pain with normal coronary angiograms presents a diagnostic challenge.
- Ischemic-like electrocardiogram (ECG) changes during exercise in these patients suggest an underlying mechanism.
- Coronary microvascular dysfunction is a potential contributor to these symptoms.
Purpose of the Study:
- To investigate the mechanism of ischemic-like ECG during exercise in patients with angina and normal coronary arteries.
- To differentiate between coronary microvascular dysfunction and altered cardiac metabolism as causes of exertional angina.
Main Methods:
- Prospective study involving 33 patients with angina of unknown cause.
- Treadmill exercise test (TET) and coronary hemodynamic study, including dipyridamole infusion.
- Measurement of great cardiac vein flow (GCVF), coronary vascular resistance, and coronary flow reserve.
Main Results:
- Patients with ischemic-like ECG during TET (TET+) showed significantly lower maximum GCVF and corrected GCVF compared to those without (TET-).
- TET+ patients exhibited higher minimum coronary vascular resistance and lower coronary flow reserve after dipyridamole infusion.
- Myocardial oxygen consumption and efficiency were similar between groups, indicating no significant metabolic alteration.
Conclusions:
- Coronary microvascular dysfunction is implicated in exertional angina and ischemic-like ECG in patients with normal coronary angiograms.
- Altered cardiac metabolism is unlikely to be the primary cause.
- These findings highlight the importance of assessing microvascular function in unexplained angina.
Abstract:
To determine the possible mechanism of the ischemic-like electrocardiogram (ECG) during exercise in the presence of anginal chest pain and normal coronary angiograms, both a treadmill exercise test (TET) and coronary hemodynamic study were prospectively performed in 33 consecutive patients (18 females and 15 males, aged 48 +/- 10 years) with angina of unknown cause. Although baseline characteristics and coronary hemodynamics were similar between patients with (TET+, n = 17) and those without (TET-, n = 16) ischemic-like ECG during TET, effort angina was more frequently seen in the former group (p < 0.01). Compared to TET- patients, TET+ patients had a significantly lower maximum great cardiac vein flow (GCVF, 108.8 +/- 47.0 vs 146.4 +/- 23.4 ml/min, p = 0.007), higher minimum coronary vascular resistance (0.94 +/- 0.41 vs 0.61 +/- 0.09 mmHg/ml/min., p = 0.003), and lower corrected GCVF (GCVF/rate-pressure product, 0.0087 +/- 0.0036 vs 0.0125 +/- 0.0019, p = 0.001) after dipyridamole infusion (0.56 mg/kg for 4 min). Though coronary flow reserve was significantly lower in TET+ than in TET- patients (2.26 +/- 0.59 vs 3.08 +/- 0.48, p = 0.0001), myocardial oxygen consumption and myocardial efficiency (rate-pressure product/myocardial oxygen consumption) were still similar between these two groups after dipyridamole infusion. Thus, coronary microvascular dysfunction rather than altered cardiac metabolism could contribute to effort angina and ischemic-like ECG during exercise in patients with anginal chest pain and normal coronary angiograms.