Purpose: We compared regional myocardial strain measured by speckle tracking during dobutamine stress echocardiography (DSE) in patients with or without intramural course of the LAD.
Methods: Fifty patients (63 ±7 years) were prospectively enrolled and underwent DSE, computed tomography angiography (CTA), quantitative 15-Oxygen water positron emission tomographic perfusion imaging (PET), and invasive angiography. Patients with superficial (>1 mm) or deep (>2 mm) intramural course in the LAD were identified using CTA. Regional longitudinal strain and strain rate (LS, LSr), circumferential strain and strain rate (CS, CSr), as well as radial strain and strain rate (RS, RSr) were measured at rest, at a dobutamine dose of 20 mg/kg/min, at peak stress, and at early recovery (1 min after stress). Obstructive coronary artery disease (CAD) was defined as >75% stenosis or 40% to 75% stenosis combined with either fractional flow reserve < 0.80 or ischemia on PET.
Results: Intramural course of the LAD was detected in 17 patients. Of these, 8 patients had obstructive CAD and were excluded. Thus, 9 patients with intramural course and 11 controls without intramural course or obstructive CAD in the LAD were included. Myocardial strain and strain rate in the myocardial territory distal to intramural segment were similar to those in controls at rest, dobutamine stress and early recovery (Figure). Furthermore, there were no significant differences, at all time points, between the regional strain values of the myocardial segments those distal to the superficial and deep intramural course. In the myocardium distal to an intramural coronary segment, regional myocardial flow measured by PET during adenosine stress correlated with the regional LS (r=0.80, p=0.004), LSr (r=0.66, p=0.03), and CS (r=0.69, p=0.02) and RS (r=0.53, p=0.07) at the peak dobutamine stress. However, there was no correlation between flow and strain at rest.
Conclusions: Myocardial strain is not consistently affected in patients with intramural course of the LAD during dobutamine stress as assessed by speckle tracking echocardiography. Larger studies are warranted to evaluate whether certain anatomical variants cause abnormalities in systolic myocardial strain.