New signs characteristic of myocardial bridging demonstrated by intracoronary ultrasound and Doppler

Background Large discrepancies exist concerning the incidence of myocardial bridging. This has been reported to be 0.5%-2.5% following coronary angiog raphy but 15%-85% following autopsy. The purpose of the study was to use in travascular ultrasound and intracoronary Doppler to study the morphology an d flow characteristics of myocardial bridging in order to find feasible par ameters of this syndrome. Methods and Results Intravascular ultrasound was performed in 62/69 patient s in whom typical angiographic 'milking effects' were present. In 48 patien ts, intracoronary Doppler was performed. A specific, echolucent 'half moon' phenomenon surrounding the myocardial bridge was found in all the patients . The thickness of the half moon area was 0.47 +/- 0.19 mm in diastole and 0.52 +/- 0.23 mm in systole. There was systolic compression of the myocardi al bridge with a lumen reduction during systole of 36.4 +/- 8.8%. Using int racoronary Doppler, a characteristic early diastolic 'finger tip' phenomeno n was observed in 42 (87%) of the patients. All patients showed no or reduc ed antegrade systolic flow. Coronary flow velocity reserve was 2.03 +/- 0.5 4. After intracoronary nitroglycerin injection, retrograde systolic flow oc curred in 37 (77%) of the 48 patients, with a velocity of - 22.2 +/- 13.2 c m.s(-1). Intra-vascular ultrasound revealed atherosclerotic involvement of the proximal segment in 61 (88%) of the 69 patients, with an area stenosis of 42 +/- 13%. No plaques were found in the bridge or distal segments in th e 62 patients in whom it was possible to introduce the ultrasound catheter throughout the bridging segment. Conclusion Myocardial bridging is characterized by the following morphologi cal and functional signs: a specific, echolucent half moon phenomenon over the bridge segment, which exists throughout the cardiac cycle; systolic com pression of the bridge segment of the coronary artery; accelerated flow vel ocity at early diastole (finger-tip phenomenon); no or reduced systolic ant egrade flow; decreased diastolic/systolic velocity ratio; retrograde flow i n the proximal segment, which is provoked and enhanced by nitroglycerin inj ection. (C) 1999 The European Society of Cardiology.