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Coronary microvascular dysfunction (CMVD) can mediate angina and myocardial ischemia in a proportion of patients presenting with signs and symptoms of myocardial ischemia in the absence of obstructive epicardial coronary artery disease (CAD). Previous studies have shown sex based difference in coronary flow reserve (CFR) however sex based difference in other measures of CMVD have not been explored.
Assess sex differences in invasive measures of coronary microvascular dysfunction using Index of Microcirculatory Resistance (IMR).
From 2011-2016, 87 patients presenting with ischemia and non-obstructive CAD underwent invasive assessment using IMR. IMR is a resistance index which measures global microcirculatory resistance (IMR= hyperemic distal coronary pressure X hyperemic coronary blood flow). IMR < 20 is considered normal. Multiple hemodynamic variables were compared between women and men using standard statistical methods.
Mean age of the group was 54.7 ±10.3 and 68% were women. Overall, prevalence of abnormal IMR was 30%. Women had higher mean aortic and distal perfusion pressures. On the other hand baseline and hyperemic flow was faster and CFR was lower among women compared to men. There was no difference in the prevalence of abnormal IMR between the sexes. Men were significantly more likely to have angiographic slow coronary flow phenomena (Table 1).
Among patients with angina and non-obstructive CAD, overall prevalence of abnormal IMR is similar between the sexes. There are however, significant sex based differences in invasive coronary hemodynamics that need to be better studied and understood. These findings continue to highlight sex based differences in pathophysiology of ischemic heart disease.
|Women N=59||Men N=28||P value|
|Baseline transit time (BTT) (sec)||0.82±0.50||1.31±0.54||<0.001|
|Hyperemic transit time (HTT) (sec)||0.27±0.13||0.41±0.29||<0.001|
|Fractional Flow Reserve||0.92±0.05||0.89±0.05||0.01|
|Coronary Flow Reserve (HTT/BTT)||3.07±1.68||3.94±2.01||0.04|
|IMR (HTT X Pressure (distal))||21±10.64||29.42±24.28||0.02|
|Abnormal IMR (%)||16 (27)||10 (35)||NS|
|Slow Coronary Flow Phenomena||4 (7)||12 (43)||<0.001|