Functional Assessment of Myocardial Bridging With Conventional and Diastolic Fractional Flow Reserve: Vasodilator Versus Inotropic Provocation

Abstract

Background Functional assessment of myocardial bridging (MB) remains clinically challenging because of the dynamic nature of the extravascular coronary compression with a certain degree of intraluminal coronary reduction. The aim of our study was to assess performance and diagnostic value of diastolic‐fractional flow reserve (d‐FFR) during dobutamine provocation versus conventional‐FFR during adenosine provocation with exercise‐induced myocardial ischemia as reference. Methods and Results This prospective study includes 60 symptomatic patients (45 men, mean age 57±9 years) with MB on the left anterior descending artery and systolic compression ≥50% diameter stenosis. Patients were evaluated by exercise stress‐echocardiography test, and both conventional‐FFR and d‐FFR in the distal segment of left anterior descending artery during intravenous infusion of adenosine (140 μg/kg per minute) and dobutamine (10–50 μg/kg per minute), separately. Exercise–stress‐echocardiography test was positive for myocardial ischemia in 19/60 patients (32%). Conventional‐FFR during adenosine and peak dobutamine had similar values (0.84±0.04 versus 0.84±0.06, P =0.852), but d‐FFR during peak dobutamine was significantly lower than d‐FFR during adenosine (0.76±0.08 versus 0.79±0.08, P =0.018). Diastolic‐FFR during peak dobutamine was significantly lower in the exercise‐stress‐echocardiography test –positive group compared with the exercise‐ stress‐echocardiography test –negative group (0.70±0.07 versus 0.79±0.06, P <0.001), but not during adenosine (0.79±0.07 versus 0.78±0.09, P =0.613). Among physiological indices, d‐FFR during peak dobutamine was the only independent predictor of functionally significant MB (odds ratio, 0.870; 95% CI, 0.767–0.986, P =0.03). Receiver‐operating characteristics curve analysis identifies the optimal d‐FFR during peak dobutamine cut‐off ≤0.76 (area under curve, 0.927; 95% CI, 0.833–1.000; P <0.001) with a sensitivity, specificity, and positive and negative predictive value of 95%, 95%, 90%, and 98%, respectively, for identifying MB associated with stress‐induced ischemia. Conclusions Diastolic‐FFR, but not conventional‐FFR, during inotropic stimulation with high‐dose dobutamine, in comparison to vasodilatation with adenosine, provides more reliable functional significance of MB in relation to stress‐induced myocardial ischemia.

Coronary Flow Velocity Reserve Using Dobutamine Test for Noninvasive Functional Assessment of Myocardial Bridging

“…Invasive coronary angiography and detailed frame-by-frame QCA analysis of the interpolated reference diameter, minimal luminal diameter (MLD), and percent DS, at the most severe MB-site, were performed as previously described in detail elsewhere [ 14 , 30 ]. Briefly, all angiographic images were obtained at least 1 min after ic.…”

“…Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography (TTDE) is a clinically useful and feasible noninvasive diagnostic index for the assessment of fixed coronary stenosis severity [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Although adenosine-induced maximal hyperemia is considered a gold standard for TTDE-CFVR measurements in the functional assessment of fixed coronary stenosis, the functional assessment of myocardial bridging (MB) is less reliable [ 9 , 10 , 11 , 12 , 13 , 14 ]. Despite being considered a benign coronary lesion, MB may cause life-threatening events such as ventricular arrhythmias, acute coronary syndrome, or even sudden cardiac death [ 15 , 16 , 17 , 18 ].…”

“…Despite being considered a benign coronary lesion, MB may cause life-threatening events such as ventricular arrhythmias, acute coronary syndrome, or even sudden cardiac death [ 15 , 16 , 17 , 18 ]. As a result of these events, concerns have been raised regarding its clinical significance and the need for appropriate diagnostic test/s which could be helpful in the identification of MB associated with myocardial ischemia [ 14 ]. Therefore, previous studies indicate that the functional assessment of MB should include dobutamine provocation with possibly exaggerated extravascular systolic coronary artery compression [ 9 , 10 , 11 , 12 , 13 , 14 ].…”

“…As a result of these events, concerns have been raised regarding its clinical significance and the need for appropriate diagnostic test/s which could be helpful in the identification of MB associated with myocardial ischemia [ 14 ]. Therefore, previous studies indicate that the functional assessment of MB should include dobutamine provocation with possibly exaggerated extravascular systolic coronary artery compression [ 9 , 10 , 11 , 12 , 13 , 14 ]. Additionally, the feasibility of assessing CFVR by TTDE during dobutamine provocation is high and the steady-state hyperemia induced with a high-doses of dobutamine (>20 µg/kg/min) is similar to adenosine-induced one [ 13 , 14 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”

“…Therefore, previous studies indicate that the functional assessment of MB should include dobutamine provocation with possibly exaggerated extravascular systolic coronary artery compression [ 9 , 10 , 11 , 12 , 13 , 14 ]. Additionally, the feasibility of assessing CFVR by TTDE during dobutamine provocation is high and the steady-state hyperemia induced with a high-doses of dobutamine (>20 µg/kg/min) is similar to adenosine-induced one [ 13 , 14 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Recently, it has been demonstrated that TTDE-CFVR measured at high-dose dobutamine provides a more accurate functional evaluation of MB compared to adenosine [ 13 ].…”