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

Background: It has been shown that coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) during dobutamine (DOB) provocation provides a more accurate functional evaluation of myocardial bridging (MB) compared to adenosine. However; the cut-off value of CFVR during DOB for identification of MB associated with myocardial ischemia has not been fully clarified. Purpose: This prospective study aimed to determine the cut-off value of TTDE-CFVR during DOB in patients with isolated-MB, as compared with stress-induced wall motion abnormalities (VMA) during exercise stress-echocardiography (SE) as reference. Methods: Eighty-one symptomatic patients (55 males [68%], mean age 56 ± 10 years; range: 27–74 years) with the existence of isolated-MB on the left anterior descending artery (LAD) and systolic MB-compression ≥50% diameter stenosis (DS) were eligible to participate in the study. Each patient underwent treadmill exercise-SE, invasive coronary angiography, and TTDE-CFVR measurements in the distal segment of LAD during DOB infusion (DOB: 10–40 μg/kg/min). Using quantitative coronary angiography, both minimal luminal diameter (MLD) and percent DS at MB-site at end-systole and end-diastole were determined. Results: Stress-induced myocardial ischemia with the occurrence of WMA was found in 23 patients (28%). CFVR during peak DOB was significantly lower in the SE-positive group compared with the SE-negative group (1.94 ± 0.16 vs. 2.78 ± 0.53; p < 0.001). ROC analyses identified the optimal CFVR cut-off value ≤ 2.1 obtained during high-dose dobutamine (>20 µg/kg/min) for the identification of MB associated with stress-induced WMA, with a sensitivity, specificity, positive and negative predictive value of 96%, 95%, 88%, and 98%, respectively (AUC 0.986; 95% CI: 0.967–1.000; p < 0.001). Multivariate logistic regression analysis revealed that MLD and percent DS, both at end-diastole, were the only independent predictors of ischemic CFVR values ≤2.1 (OR: 0.023; 95% CI: 0.001–0.534; p = 0.019; OR: 1.147; 95% CI: 1.042–1.263; p = 0.005; respectively). Conclusions: Noninvasive CFVR during dobutamine provocation appears to be an additional and important noninvasive tool to determine the functional severity of isolated-MB. A transthoracic CFVR cut-off ≤2.1 measured at a high-dobutamine dose may be adequate for detecting myocardial ischemia in patients with isolated-MB.

Characteristics of coronary flow velocity reserve on transthoracic Doppler echocardiography in patients with a history of Kawasaki disease

Whether the acute inflammation caused by Kawasaki disease will have an effect on the endothelial function of coronary arteries in the future is unknown. Methods: The coronary flow velocity reserve of the left anterior descending artery was examined by transthoracic Doppler echocardiography in 189 patients (male 125, female 64) with a history of Kawasaki disease and 10 volunteers (control). Their ages ranged from 6 to 40 years (median 22 years). The patients were divided into nine groups based on the left anterior descending artery lesions. The coronary flow velocity reserve was measured by intravenous administration of adenosine triphosphate (0.15 mg/kg/minute) while fasting. The coronary flow velocity reserve was calculated as the ratio of hyperaemic to basal mean diastolic flow velocities. The respective groups were as follows: control, no coronary artery lesions (n = 39), no coronary artery lesions in the right coronary artery (n = 29), regression (n = 11), aneurysm at the bifurcation of the left coronary artery (n = 26), aneurysm of the left anterior descending artery (n = 15), localised stenosis <75% (n = 12), localised stenosis ≥75% (n = 17), segmental stenosis (n = 5) and coronary artery bypass grafting (n = 36). One-factor ANOVA followed by Tukey’s test was used to compare the coronary flow velocity reserve among the groups. Results: The coronary flow velocity reserve was significantly lower in the localised stenosis ≥75%, segmental stenosis and coronary artery grafting groups than in the other groups (p < 0.05). Conclusions: The endothelial function in the epicoronary artery was preserved in patients with a history of Kawasaki disease and dilated coronary artery lesions.

Invasive methods for coronary reserve measurement

During the last years, following numerous trials, the need of functional assessment of stenoses before myocardial revascularization has been established. This came to replace the subjective approach based on the so-called “oculo-stenotic” reflex of the operator. Numerous methods for coronary reserve (CR) estimation as a measure of functional significance of the lesion, have been introduced in the practice. Those methods are noninvasive and invasive. A part of them are based on the measurement of coronary flow velocity before and after hyperemic medication, other are based on the difference of arterial pressure before and after the coronary stenosis. They are divided to such with or without hyperemic medication. During the last years in the diagnostic have been used methods for functional estimation of the lesions based only on standard coronary angiography or even computerized tomography (CT). The aim of this article is to present a review of modern invasive methods for coronary reserve measurement.

Cut-off value of coronary flow velocity reserve obtained by transthoracic Doppler echocardiography during intravenous infusion of dobutamine for diagnosis of functional significant myocardial bridging

Background Recent studies showed that coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) during inotropic stimulation with dobutamine (DOB), in comparison to vasodilation with adenosine, provides more reliable functional evaluation of myocardial bridging (MB). However, the adequate cut-off value of CFVR during DOB for diagnosing functional significant MB has not been fully established. Purpose The purpose of the study was to evaluate the adequate cut-off value of TTDE- CFVR during DOB for diagnosis of functional significant MB. Methods This prospective study included 79 patients (54 males, mean age 55±10 years) with angiographic evidence of isolated MB on the left anterior descending artery (LAD) and systolic compression ≥50% diameter stenosis. Exercise stress-echocardiography test (ExSE) and TTDE-CFVR in the distal segment of LAD during DOB infusion (DOB: 10–40μg/kg/min) were performed in all patients. Percent diameter stenosis (DS) of MB at end-systole and end-diastole were analyzed using quantitative coronary angiography. Results Exercise-SE was positive for myocardial ischemia in 22/79 (28%). CFVR during peak DOB was significantly lower in SE-positive group in comparison to SE-negative group (1.94±0.16 vs. 2.78±0.53, p&lt;0.001). ROC analysis identifies the optimal CFVR during peak DOB cut-off value &lt;2.1 (AUC 0.985, 95% CI: 0.965–1.000, p&lt;0.001), with a sensitivity of 96% and specificity of 95%, positive predictive value of 88%, and negative predictive value of 98%, for identifying functionally significant MB associated with stress-induced myocardial ischemia. The categorical agreement between TTDE-CFVR at peak DOB and ExSE was high (kappa value = 0.877, p&lt;0.001). Multivariate logistic regression analysis showed that percent DS at end-diastole was the only independent predictor of ischemic CFVR value &lt;2.1 (OR: 1.136, 95% CI: 1.045–1.235, p=0.003). Conclusion A cut-off value &lt;2.1 of CFVR during DOB infusion obtained by TTDE may adequate discriminate functional significant MB that induce myocardial ischemia which is caused by an incomplete diastolic MB-decompression. FUNDunding Acknowledgement Type of funding sources: None.

Impact of transcatheter aortic valve implantation on coronary flow reserve by transthoracic Doppler echocardiography 1-year after the intervention in severe aortic stenosis patients

Background Coronary flow reserve (CFR) which is one of indexes reflecting coronary microcirculation in patients without significant epicardial coronary lesions can be impaired in patients with severe aortic stenosis (AS). It has been shown that CFR is an independent predictor for future cardiovascular events in AS patients. Transcatheter aortic valve implantation (TAVI) has rapidly become widespread and is becoming the standard treatment for severe AS. This procedure may have a good effect on CFR due to reduction of severe afterload in patients with severe AS. Although the recent reports evaluated change in CFR immediately and 6 months after TAVI, it has not been evaluated whether impaired CFR improves 1-year after TAVI in AS patients with preserved left ventricular ejection fraction (LVEF). Purpose The purpose of the present study was to investigate whether impaired CFR improves 1-year after TAVI in severe AS patients with preserved LVEF. Methods The study population consists of consecutive 105 patients with severe AS undergoing TAVI. Exclusion criteria were atrial fibrillation, old myocardial infarction, history of coronary artery bypass grafting, significant lesions in the left anterior descending artery (LAD), moderate or severe mitral valve disease, history of valve replacement, LVEF &lt;50% and preoperative CFR &gt;2.2. CFR was obtained from coronary flow velocity by transthoracic echocardiography at rest and maximal hyperemia in LAD before, immediately and 1-year after TAVI. We compared CFR between before and after TAVI in the study patients who did not meet the exclusion criteria. Results After exclusion of 76 patients who met the exclusion criteria, the final study patients consist of 29 patients (8 male, 84.9±5.2 years). There was no significant difference in LVEF (61.3±3.4% vs 61.6±4.4%, P=0.667) and LV end-diastolic volume (LVEDVI; 58.2±9.2 mL/m2 vs 55.8±9.0 mL/m2, P=0.089) between before and immediately after TAVI. LVEF (61.0±2.8%, P=0.721) and LVEDVI (58.0±9.1 mL/m2, P=0.949) 1-year after TAVI were similar to those before TAVI. There was no significant difference in coronary flow velocity at rest between before and immediately after TAVI (27.4±8.9 vs 24.4±7.0 cm/s, P=0.051) and between before and 1-year after TAVI (25.9±8.3 cm/s, P=0.396). Coronary flow velocity at maximal hyperemia 1-year after TAVI significantly increased compared with that before TAVI (from 48.8±13.9 to 67.9±21.0 cm/s, P&lt;0.001) while there was no significant difference between before and immediately after TAVI (52.0±12.0 cm/s, P=0.186). Impaired CFR before TAVI (1.82±0.28) increased immediately (2.03±0.39, P=0.009) and 1-year after TAVI (2.69±0.57, P&lt;0.001). Conclusions The present results suggest that impaired CFR in patients with preserved LVEF improves 1-year after TAVI. TAVI may have a good effect on CFR in severe AS patients with preserved LVEF. FUNDunding Acknowledgement Type of funding sources: None.

Comparison of coronary flow reserve feasibility and values in different stress echocardiography protocols: dobutamine, dipyridamole, exercise and rapid pacing

Background and aims To compare the feasibility of Coronary Flow Velocity Reserve (CFVR) assessment in the left anterior descending (LAD) artery in four types of stress echocardiography (SE): dobutamine (DOB), dipyridamole (DIP), rapid pacing (PAC) and bicycle exercise (EXE). Methods and results We subjected 369 patients (mean age: 67±11 years) to SE with DOB (up to 40 mcg/kg/min, n=230), DIP (0.84 mg/kg, n=73), PAC (n=22) or EXE (n=44). CFVR was measured as the ratio of peak diastolic coronary flow velocity (CFV) during exercise, pharmacological stress or pacing and peak diastolic CFV at rest in distal or mid LAD. The feasibility was excellent during PAC (100%), DOB (95%) and DIP (95%) and lower during EXE (73%, p&lt;0.01 vs other groups) when assessed in all consecutive patients. When assessed in patients having readable LAD flow at rest the feasibility achieved even higher values, being however still lowered in EXE group, see Figure 1. In multivariate analysis only the EXE protocol was a predictor of LAD flow loss during SE, with OR = 8.23 (95% CI 2.17 – 31.33), p=0.0019. CFVR was lower with PAC (1.8±0.4) as compared to DIP (2.2±0.6, p=0.0061) and DOB (2.2±0.6, p=0.0025), but similar to EXE (2.0±0.6, p=0.178), and correlated best with the peak heart rate in EXE and PAC, see Figure 2. Conclusion CFVR in LAD can be obtained during all forms of SE, but the feasibility is significantly higher with PAC and pharmacological tests as compared to EXE, which was identified in our study as the independent predictor of the loss of LAD flow recording at the peak of stress test. Moreover, CFVR values were the lowest in PAC group which however encompassed the older patients with more advanced coronary artery disease. Significant correlation between HR and CFVR observed in EXE and PAC suggests that in this type of SE cut-off value of CFVR should be probably indexed to maximal HR achieved. FUNDunding Acknowledgement Type of funding sources: None. Figure 1 Figure 2