Background: The coronary flow velocity (CFV) has been used to estimate coronary flow reserve (CFR) during dobutamine stress echocardiography (DSE). However, the relationship of the CFR to myocardial wall thickening (WT) has not been investigated.
Objectives: The aims of this study were: (1) to assess the feasibility of obtaining systolic and diastolic CFV and thus CFR during DSE and (2) to assess the relation between CFR and stress induced WT.
Methods: Distal left anterior descending CFV was recorded by transthoracic Doppler echocardiography during DSE. Systolic and diastolic velocities were measured at rest, low and peak dobutamine doses, simultaneously, WT of distal anteroseptal segment was assessed by 2D-guided M-mode. The CFV and CFR of patients with normal WT defined as thickening of >50% (group 1) at peak stress were compared to that of patients with abnormal WT (group 2).
Results: A total of 67 patients, 34 females and 33 males (mean age of 66.5+/-14.5 years) were studied. The feasibility of assessing the CFR was 97% from peak diastolic velocity, 91% from diastolic time velocity integral, 91% from peak systolic velocity, and 90% from systolic time velocity integral. Contrast agent was used in 6 patients (7%) to obtain the CFV. Twenty-five of 67 patients demonstrated abnormal wall thickening. The percentage of WT was 30.9+/-15.7% in group 2 compared to 80.8+/-24.3% in group 1 (p<0.0001). The 25 patients in group 2, who developed abnormal WT, demonstrated significantly lower CFR at low dose, as well as at peak dobutamine dose compared to patients in group 1 (1.55+/-0.5 vs. 2.03+/-0.6, p<0.008).
Conclusion: CFV and CFR assessments are feasible during DSE with second harmonic imaging in most patients without use of contrast agent. CFR assessment during DSE correlates well with wall thickening and was able to detect ischemia early before development of wall motion abnormality.