Key result
Cardiac syndrome X is linked to ~76% higher IMR vs matched controls.
Why the study?
Increased coronary microvascular resistance is speculated to cause myocardial ischemia in cardiac syndrome X, but it has never been directly demonstrated or correlated with ischemia severity.
Does coronary microvascular resistance differ between patients with cardiac syndrome X and control subjects, and does it correlate with ischemia severity?
Case-Control (n=36)
Does coronary microvascular resistance differ between patients with cardiac syndrome X and control subjects, and does it correlate with ischemia severity?
Absolute Event Rate: 33.1% vs 18.8%
p-value: p=<0.001
Intracoronary thermodilution demonstrates that patients with cardiac syndrome X have increased microvascular resistance that correlates with ischemia severity.
Supports microvascular dysfunction assessment in cardiac syndrome X; leaves open whether resistance-guided interventions improve outcomes.
BACKGROUND: Although increased coronary microvascular resistance (CMR), resulting in coronary microvascular dysfunction, is speculated to be responsible for myocardial ischemia in patients with cardiac syndrome X (CSX), it has never been directly demonstrated, and the correlation between CMR and severity of myocardial ischemia has not been elucidated in this setting. This study aimed to ascertain the increased CMR directly and to explore the relationship between CMR and severity of ischemia in patients with CSX. METHODS AND RESULTS: We studied 18 patients with CSX and 18 age- and sex-matched control subjects. Thermodilution-derived coronary flow reserve and index of microvascular resistance were measured using a pressure-temperature sensor-tipped coronary wire. Exercise treadmill test was performed by the Bruce protocol for calculating Duke treadmill score. Coronary flow reserve was significantly lower (2.37±0.81 versus 3.68±0.72; P<0.001) and index of microvascular resistance was higher (33.1±7.9 versus 18.8±5.6 U; P<0.001) in patients with CSX compared with those in control subjects. The Duke treadmill score was correlated positively to coronary flow reserve (r=0.539; P=0.021) and negatively to index of microvascular resistance (r=-0.742; P<0.001) in patients with CSX. CONCLUSIONS: Using an intracoronary thermodilution method, we for the first time directly demonstrated an increased microvascular resistance in patients with CSX. Furthermore, severity of ischemia was found to be intimately associated with CMR in this setting.
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Luo et al. (2014) conducted a case-control in Cardiac Syndrome X (n=36). Cardiac syndrome X vs. Age- and sex-matched control subjects was evaluated on Index of microvascular resistance (p=<0.001). Cardiac syndrome X was associated with a significantly higher index of microvascular resistance (33.1 vs 18.8 U; P<0.001) and lower coronary flow reserve compared to matched controls.
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