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Physiological Significance of Myocardial Bridging by Fractional Flow Reserve—An Observational Study

Myocardial bridge (MB) is a portion of an epicardial coronary artery that takes an intramuscular course. The systolic compression of MB often gets carried over to early and mid-diastole, compromising coronary blood flow. In clinical practice, we encounter patients with angina, non-invasive evidence of ischemia, and a MB as the only relevant finding on angiography. In view of studies in support of decreased coronary flow reserve in MB, we assessed the physiological significance of MB by fractional flow reserve (FFR).
 Methods and Results We enrolled eight patients with chronic stable angina and positive noninvasive stress test, who had no significant CAD, and with evidence of MB in the left anterior descending artery. Mean age of population was 57.14 ± 6.25 years. Two (25%) were females and six (75%) were males. Four (50%) were smokers, five (62.5%) were diabetics, and two (25%) were hypertensives. Mean length of MB is 19.4 ± 5.04 mm. All underwent physiological assessment by FFR and the baseline, post nitroglycerin (NTG), and post adenosine readings were noted. Mean pre-NTG value, post-NTG, and post-adenosine were 0.974 ± 0.022, 0.96 ± 0.03, and 0.88 ± 0.042 (≤0.80 hemodynamically significant) respectively. Paired t-test showed significant reduction in FFR after NTG (p = 0.0452) and post-adenosine (p = 0.011) but all eight patients did not get significant FFR.
 Conclusion MB was found to be physiologically insignificant in our group of patients. But a statistical significant reduction of FFR in MB, post NTG and post adenosine, does impress on the fact that, an extensive study over a longer period of course, could throw light on this unsettled area of physiological significance and optimal therapeutic approach.