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.

Case Report: A Case of Unusual Combination of Hypothyroidism, Myocardial Bridging, and Myocardial Infarction-Induced Left Ventricular Aneurysm

Background: Myocardial bridging (MB) of the coronary artery is a congenital anatomical variation, which has traditionally been considered a benign condition that does not cause cardiovascular events. However, recent studies have shown that MB is associated with major adverse cardiac events, including angina, myocardial infarction, arrhythmia, syncope, and even sudden death.Case: We report a case of a 41-year-old man who had hypothyroidism and MB associated with ventricular aneurysm following myocardial infarction. This patient was admitted to our hospital because of 11 days of sudden discomfort and pain in the chest. An electrocardiogram on admission showed an old myocardial infarction. Coronary angiography showed MB in the distal segment of the left anterior descending artery. Left ventricular angiography, which was performed using a pigtail catheter, showed ventricular aneurysm formation. Thyroid ultrasound demonstrated hypothyroidism and Hashimoto's thyroiditis. Patients with hypothyroidism and MB have a high risk of acute myocardial infarction or even sudden death.Conclusion: Observations in our case suggest that early recognition of hypothyroidism and MB is important for risk stratification and prognosis in patients with myocardial necrosis and acute coronary syndrome. Additionally, this early recognition may have positive effects on cardiovascular outcomes in patients with hypothyroidism.

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.

Correction to: Myocardial bridging of the left anterior descending coronary artery as a risk factor for atrial fibrillation in patients with hypertrophic obstructive cardiomyopathy: a matched case–control study

An amendment to this paper has been published and can be accessed via the original article.