a 60-year - old male patient , with a known history of arterial hypertension and type-2 diabetes mellitus , was referred to the outpatient echocardiography laboratory to undergo stress echocardiography because of recent episodes of chest pain occurring on mild exertion .
he was on drug therapy with angiotensin - receptor blocker , thiazide diuretic , nondihydropyridine calcium antagonist , and dronedarone , which had been started because of recent episodes of paroxysmal atrial fibrillation and discontinued 2 days before the stress test .
the patient received a standard protocol of high dipyridamole infusion in two doses ( 0.56 mg / kg and 0.28 mg / kg ) followed by atropine administration ( 1 mg in four 0.25 mg doses ) . at rest , no ischemic abnormalities were observed on electrocardiogram ( ecg ) and transthoracic echocardiography ( tte ) [ figure 1 and videos 13 ] .
after completion of dipyridamole infusion , the patient complained a mild chest discomfort , without any significant ecg changes and any apparent wall - motion abnormalities on tte [ videos 46 ] .
after atropine injection , a worsening of the anginal symptoms combined with a descending st - depression in v3 occurred ; despite the absence of relevant echocardiographic changes , two - dimensional ( 2d ) strain analysis showed lower longitudinal strain of the anterior interventricular septum from rest to peak dose [ figure 2 ] .
afterward , as recommended , aminophylline was administered ; interestingly , a more pronounced st - depression and deep inverted t - waves in v2v4 appeared [ figure 3 ] .
the patient was admitted to the cardiology department and underwent coronary angiography from the radial access , which revealed a long myocardial bridge ( mb ) of the left anterior descending ( lad ) artery with systolic  milking  [ figures 4 , 5 and videos 79 ] .
the patient was , thereafter , treated with a beta - blocker and discharged without symptoms and ischemic abnormalities on rest ecg .
electrocardiogram at rest two - dimensional strain analysis showing global longitudinal strain at rest ( upper panel ) and at peak dose of dipyridamole ( lower panel ) electrocardiogram after injection of atropine and aminophylline coronary angiography images in diastole ( left ) and systole ( right ) showing myocardial bridge of the left anterior descending artery with systolic  milking  angiographic images did not change after intracoronary nitroglycerine administration
this case depicts a clinical scenario of positive dipyridamole stress test in a patient affected by mb of the lad .
although mb has been classically deemed a benign coronary artery abnormality , it has been recently related to acute myocardial infarction and sudden cardiac death .
moreover , mb has been also associated with endothelial dysfunction , early atherosclerosis , and coronary vasospasm . in particular ,
a worsening of systolic coronary narrowing of mb has been found when using vasodilator agents , such as nitroglycerine , which are usually not administered in these patients . in our case ,
dipyridamole provoked chest pain associated with minor ecg ischemic changes , such as an only one - lead ( v3 ) st - depression ; these abnormalities worsened after the administration of atropine and later , aminophylline , likely because of drug - induced positive inotropic and chronotropic effects .
atropine might also have determined myocardial ischemia through a paradoxical coronary vasoconstriction induced by acetylcholine as observed in the presence of endothelial dysfunction and mb .
this case has the following interesting implications : ( 1 ) the ability to detect mb also using a vasodilator stress test ( and not only dobutamine echocardiography or exercise test ) , particularly with the addition of atropine injection , ( 2 ) the utility of 2d strain analysis in confirming subtle regional wall - motion abnormalities , and ( 3 ) peculiar diagnostic features , on stress echocardiography , suggesting mb rather than obstructive coronary artery disease . in particular , the observed ecg and echocardiographic ischemic changes , although suggestive of a lad disease , appeared to be late occurring and less extended than usually observed in patients with stable hemodynamic lad obstruction , which should have determined more pronounced ecg and wall - motion abnormalities .
indeed mb , differently from a fixed coronary obstruction , is a dynamic stenotic lesion , requiring a consistent increase in heart rate and myocardial contractility to provoke myocardial ischemia .
hence , mb could have been clearly unmasked only whenever positive inotropic and chronotropic agents had been added to the vasodilator stress caused by dipyridamole .
thus , the finding of worsening ischemic abnormalities after the administration of atropine ad aminophylline , during dipyridamole stress echocardiography , may represent a particular diagnostic feature of mb .
 a 60-year - old male patient was submitted to dipyridamole - atropine stress echocardiography ( dse ) for chest pain during exertion . at rest , no electrocardiographic ( ecg ) and transthoracic echocardiographic ( tte ) abnormalities were observed . 
 after dipyridamole infusion , the patient complained a mild chest discomfort , without ecg changes and tte wall - motion abnormalities . 
 subsequently , worsening of the anginal symptoms combined with descending st - depression and t - negative waves occurred after atropine and unexpectedly , aminophylline administration . 
 coronary angiography was performed showing a myocardial bridge ( mb ) of the left anterior descending artery . 
 the occurrence , during dse , of worsening ischemic abnormalities after atropine and aminophylline administration may be a particular diagnostic feature of mb . 