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Coronary vasodilator reserve, pain perception, and sex in patients with syndrome X
S D Rosen1, N G Uren, J C Kaski
1Cyclotron Unit, Medical Research Council Clinical Sciences Centre, Hammersmith Hospital, London, UK.
Insights
This study found no difference in myocardial blood flow (MBF) between patients with Syndrome X and healthy controls, questioning ischemia as the cause of chest pain in Syndrome X. Chest pain occurred similarly in Syndrome X and coronary artery disease patients after dipyridamole administration.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Diagnostic Imaging
Background:
- Syndrome X is characterized by chest pain and ischemic-like ECG changes despite normal coronary arteries.
- The cause of chest pain in Syndrome X, particularly the role of myocardial ischemia from coronary microvascular dysfunction, remains unclear.
- This study aimed to assess coronary microcirculation function and its relation to pain perception in Syndrome X.
Purpose of the Study:
- To evaluate myocardial blood flow (MBF) and coronary vasodilator reserve (CVR) in patients with Syndrome X.
- To compare MBF and CVR in Syndrome X patients with normal control subjects.
- To investigate the relationship between MBF, chest pain, and ECG changes under stress in Syndrome X.
Main Methods:
- Positron emission tomography with H2(15)O was used to measure MBF at rest and after dipyridamole administration.
- Coronary vasodilator reserve (CVR) was calculated as the ratio of post-dipyridamole MBF to resting MBF.
- Syndrome X patients' responses to dipyridamole (chest pain, ECG changes) were compared with those of patients with coronary artery disease (CAD).
Main Results:
- No significant differences in resting or post-dipyridamole MBF or CVR were observed between Syndrome X patients and control subjects.
- Female Syndrome X patients exhibited higher resting MBF compared to males.
- Chest pain occurred in Syndrome X patients after dipyridamole as frequently as in patients with CAD.
Conclusions:
- The findings suggest that myocardial ischemia is unlikely to be the primary cause of chest pain in most Syndrome X patients.
- The lack of correlation between MBF, chest pain, and ECG changes further supports the non-ischemic origin of pain in Syndrome X.
- Coronary microvascular function, as assessed by MBF and CVR, does not appear to be impaired in Syndrome X patients.
Background:
It remains unclear whether myocardial ischemia due to coronary microvascular dysfunction is the cause of chest pain in syndrome X (chest pain, ischemic-like stress ECG despite angiographically normal coronary arteries). To assess the function of the coronary microcirculation and its relation to pain perception, we measured myocardial blood flow (MBF) and coronary vasodilator reserve (CVR) in 29 patients with syndrome X and 20 matched normal control subjects.
Methods And Results:
MBF at rest and after intravenous dipyridamole (0.56 mg.kg-1 over 4 minutes) was measured using positron emission tomography with H2(15)O. CVR was calculated as MBFdipyridamole/MBFrest. ECG changes and chest pain after dipyridamole in syndrome X were compared with those in 35 patients with coronary artery disease (CAD). Resting and postdipyridamole MBFs were homogeneous throughout the left ventricle in syndrome X patients and control subjects. MBF was 1.05 (0.25), mean (SD) versus 1.00 (0.22) mL.min-1.g-1 (P = NS) at rest and 2.73 (0.81) versus 3.00 (1.00) mL.min-1.g-1 (P = NS) after dipyridamole in patients and control subjects, respectively. CVRs were 2.66 (0.76) and 3.06 (1.08) (P = NS) and after correction of resting MBF for rate-pressure product were 2.35 (0.83) and 2.34 (0.90) (P = NS) in patients and control subjects, respectively. Female syndrome X patients had higher resting MBF than males, at 1.18 (0.20) versus 0.88 (0.19) mL.min-1.g-1 (P < .001). Chest pain after dipyridamole occurred in syndrome X as frequently as in CAD (21/29 versus 22/35, P = NS).
Conclusions:
When patients with syndrome X are compared with control subjects, no differences are found in MBF either at rest or after dipyridamole, despite syndrome X patients experiencing chest pain after dipyridamole to the same extent as patients with CAD. These findings, together with the absence of any relation among MBF, chest pain, and ECG changes under stress, cast further doubt on ischemia as the basis of the chest pain, at least in the majority of syndrome X patients.