A Novel Stress Echocardiography Pattern for Myocardial Bridge With Invasive Structural and Hemodynamic Correlation

Abstract

BackgroundPatients with a myocardial bridge (MB) and no significant obstructive coronary artery disease (CAD) may experience angina presumably from ischemia, but noninvasive assessment has been limited and the underlying mechanism poorly understood. This study seeks to correlate a novel exercise echocardiography (EE) finding for MBs with invasive structural and hemodynamic measurements.Methods and ResultsEighteen patients with angina and an EE pattern of focal end‐systolic to early‐diastolic buckling in the septum with apical sparing were prospectively enrolled for invasive assessment. This included coronary angiography, left anterior descending artery (LAD) intravascular ultrasound (IVUS), and intracoronary pressure and Doppler measurements at rest and during dobutamine stress. All patients were found to have an LAD MB on IVUS. The ratios of diastolic intracoronary pressure divided by aortic pressure at rest (Pd/Pa) and during dobutamine stress (diastolic fractional flow reserve [dFFR]) and peak Doppler flow velocity recordings at rest and with stress were successfully performed in 14 patients. All had abnormal dFFR (≤0.75) at stress within the bridge, distally or in both positions, and on average showed a more than doubling in peak Doppler flow velocity inside the MB at stress. Seventy‐five percent of patients had normalization of dFFR distal to the MB, with partial pressure recovery and a decrease in peak Doppler flow velocity.ConclusionsA distinctive septal wall motion abnormality with apical sparing on EE is associated with a documented MB by IVUS and a decreased dFFR. We posit that the septal wall motion abnormality on EE is due to dynamic ischemia local to the compressed segment of the LAD from the increase in velocity and decrease in perfusion pressure, consistent with the Venturi effect.

Case of angina pectoris at rest and during effort due to coronary spasm and myocardial bridging

“…This suggests that cardiologists should consider the possibility of coronary spasm in patients with chest pain and MB on coronary angiograms. Several methods have been used to assess MB-related myocardial ischemia due to mechanical compression of the coronary artery by MB, such as pharmacological stress echocardiography [26] , stress myocardial perfusion imaging [27] , intracoronary blood flow velocity measurements [21,26] , and intracoronary pressure measurements [1,21,26,28] . In the current case, we assessed intracoronary pressure using a pressure wire because this technique has a reliable cutoff value [29] and can be used conveniently in the clinical setting.…”

“…the MB segment is present even at baseline [21] , only during pharmacological stress [1,26,28] , only within the MB segment [26] , or both within and beneath MB [1,21,28] . These different results may have been due to differences in the severity and degree of the MB itself as well as differences in the methods used to measure intracoronary pressure.…”

“…However, it has been reported that dobutamine is more useful as the stress agent during the assessment of MB [1,26,28] because it causes a more severe and longer compression within the MB [28] . Assessing the FFR of the vessel containing the MB can be challenging [30] because atherosclerotic changes often occur proximal to the MB [1] , which may reduce FFR.…”

Functional Versus Anatomic Assessment of Myocardial Bridging by Intravascular Ultrasound: Impact of Arterial Compression on Proximal Atherosclerotic Plaque

“…An MB has traditionally been considered a benign condition because contraction of the bridging muscles alters blood flow within the underlying LAD during systole, whereas coronary flow in the LAD occurs predominantly in diastole. A number of studies, however, have indicated that an MB can lead to significant clinical symptoms, arrhythmia, or adverse cardiac events (ie, myocardial ischemia,4, 5 myocardial infarction,6 and sudden death7) in a subset of patients.…”

Myocardial Bridges on Coronary Computed Tomography Angiography ― Correlation With Intravascular Ultrasound and Fractional Flow Reserve ―

“…The majority of people with a bridge are asymptomatic, but a small subset of patients develop angina, likely secondary to dynamic ischemia in the myocardial territory of septal branches embedded within the bridged segment. 1 Symptoms may develop or progress with the patient's age, because of associated conditions such as endothelial dysfunction, diastolic dysfunction and ventricular hypertrophy. 2 In addition, atherosclerotic plaque can accumulate proximal to the MB, possibly from dynamic retrograde flow in the LAD resulting from compression of the bridged vessel segment.…”