Impaired endothelial function in patients with myocardial bridge

Prognostic impact of nitrate therapy in patients with myocardial bridge and coexisting coronary artery spasm

The aim of this study was to investigate the prognostic impact of nitrate therapy in patients with myocardial bridge (MB) and coexisting coronary artery spasm (CAS). MB often accompanies CAS. Nitrates have been widely used as anti-ischemic drugs in CAS patients, while it is not recommended in MB patients. Thus, we investigated the long-term impact of nitrate on clinical outcomes in patients with both CAS and MB. A retrospective observational study was performed using propensity score matching (PSM) in a total of 757 consecutive MB patients with positive acetylcholine (Ach) provocation test. Patients were divided into two groups according to the regular administration of nitrates (nitrate group: n = 504, No nitrate group; n = 253). The PSM was used to adjust for selection bias and potential confounding factors, and major clinical outcomes were compared between the two groups up to 5 years. Baseline characteristics were well-matched between the two groups following PSM (n = 211 for both groups). There was no significant difference in the incidence of death, myocardial infarction, and major adverse cardiovascular events (MACEs) between the two groups. However, the nitrate group showed a significantly higher rate of recurrent angina which subsequently needed re-evaluation of coronary arteries by follow-up angiography (15.7 vs. 5.7%, Log-rank p = 0.012) compared to the non-nitrate group. Long-term nitrate administration in patients with MB and coexisting CAS did not show benefit in reducing MACE, rather it was associated with a higher incidence of recurrent angina requiring follow-up angiography.

Is myocardial bridge more frequently detected on radial access coronary angiography?

Background

Although the incidence of myocardial bridge (MB) has been defined in different femoral access conventional coronary angiography (FACCA) studies, the frequency of MB on radial access coronary angiography (RACA) is unknown. The aim of this study was to determine the difference in the incidence of MB between patients undergoing RACA and FACCA.

Method

A total of 2500 consecutive patients who underwent RACA and a total of 1455 consecutive patients who underwent FACCA were retrospectively investigated to detect the presence of MB. The incidences of the groups were calculated separately and compared. The clinical and angiographic features of the patients with MB were analyzed.

Results

MB was detected at an incidence of 10.2%, in 255/2500 patients who underwent RACA, and 1.8% in 27/1455 patients who underwent FACCA (p < 0.001). In both RACA and FACCA patients, the most involved coronary artery was the left anterior descending artery (LAD) (86.9% and 93.1%) and the mid-segment (84.9% and 88.9%) was the most affected section. Co-involvement of multiple coronary arteries by MB was 7.8% in patients who underwent RACA and 7.4% in patients who underwent FACCA. Coronary artery disease (CAD) was determined in 111 (35.7%) of the coronary arteries with MB, of which 81.9% were proximal to the MB. No significant CAD was detected in any of the vessels of 69.8% (178/255) of the patients who underwent RACA for different clinical indications.

Conclusion

These data demonstrated that the incidence of myocardial bridge able to be detected on RACA was much higher than FACCA.

Abnormal shear stress and residence time are associated with proximal coronary atheroma in the presence of myocardial bridging

BACKGROUND

Atheromatous plaques tend to form in the coronary segments proximal to a myocardial bridge (MB), but the mechanism of this occurrence remains unclear. This study evaluates the relationship between blood flow perturbations and plaque formation in patients with an MB.

METHODS AND RESULTS

A total of 92 patients with an MB in the mid left anterior descending artery (LAD) and 20 patients without an MB were included. Coronary angiography, intravascular ultrasound, and coronary physiology measurements were performed. A moving-boundary computational fluid dynamics algorithm was used to derive wall shear stress (WSS) and peak residence time (PRT). Patients with an MB had lower WSS (0.46 ± 0.21 vs. 0.96 ± 0.33 Pa, p < 0.001) and higher maximal plaque burden (33.6 ± 15.0 vs. 14.2 ± 5.8%, p < 0.001) within the proximal LAD compared to those without. Plaque burden in the proximal LAD correlated significantly with proximal WSS (r = -0.51, p < 0.001) and PRT (r = 0.60, p < 0.001). In patients with an MB, the site of maximal plaque burden occurred 23.4 ± 13.3 mm proximal to the entrance of the MB, corresponding to the site of PRT.

CONCLUSIONS

Regions of low WSS and high PRT occur in arterial segments proximal to an MB, and this is associated with the degree and location of coronary atheroma formation.

Spontaneous coronary artery dissection and associated myocardial bridging: Current evidence from cohort study and case reports

Spontaneous coronary artery dissection (SCAD) is a relatively uncommon and under-diagnosed disease characterized by the dissociation of intima and media of coronary artery wall due to an intimal tear or intramural hemorrhage. The exact pathophysiology of SCAD remains elusive and may involve multiple predisposing or precipitating factors including genetic abnormalities, inherited or acquired vasculopathies, hormonal influences, inflammation, intense exercise, emotional stress, and recreational drugs. Accruing reports, including five case reports and one cohort study, have recently addressed the concurrence of SCAD and myocardial bridging (MB), an anatomic variant in which a segment of the epicardial coronary descends and traverses in the myocardium. Among the patients with coexisting MB and SCAD, the left anterior descending artery was the only artery that harbors both pathologies, with SCAD locating either within the tunneled segment or distal to the MB. No other predisposing factors or precipitating stressors for SCAD were noted. It is hypothesized that the predilection for vasospasm, impaired endothelial function, and disturbed coronary flow dynamics associated with MB bridging could collectively contribute to the development of SCAD. Future studies are warranted to explore the mechanistic implications of MB in patients with SCAD.

Surgical unroofing of hemodynamically significant myocardial bridges in a pediatric population

BACKGROUND

Although myocardial bridges (MBs) are traditionally regarded as incidental findings, it has been reported that adult patients with symptomatic MBs refractory to medical therapy benefit from unroofing. However, there is limited literature in the pediatric population. The aim of our study was to evaluate the indications and outcomes for unroofing in pediatric patients.

METHODS

We retrospectively reviewed all pediatric patients with MB in our institution who underwent surgical relief. Clinical characteristics, relevant diagnostic data, intraoperative findings, and postoperative outcomes were evaluated.

RESULTS

Between 2012 and 2016, 14 pediatric patients underwent surgical unroofing of left anterior descending artery MBs. Thirteen patients had anginal symptoms refractory to medical therapy, and 1 patient was asymptomatic until experiencing aborted sudden cardiac arrest during exercise. Thirteen patients underwent exercise stress echocardiography, all of which showed mid-septal dys-synergy. Coronary computed tomography imaging confirmed the presence of MBs in all patients. Intravascular ultrasound imaging confirmed the length of MBs: 28.2 ± 16.3 mm, halo thickness: 0.59 ± 0.24 mm, and compression of left anterior descending artery at resting heart rate: 33.0 ± 11.6%. Invasive hemodynamic assessment with dobutamine confirmed the physiologic significance of the MBs with diastolic fractional flow reserve: 0.59 ± 0.13. Unroofing was performed with the patient under cardiopulmonary bypass (CPB) in the initial 9 cases and without CPB in the subsequent 5 cases. All patients were discharged without complications. The 13 symptomatic patients reported resolution of symptoms on follow-up, and improvement in symptoms and quality of life was documented using the Seattle Angina Questionnaire version 7.

CONCLUSIONS

Unroofing of MBs can be safely performed in pediatric patients, with or without use of CPB. In symptomatic patients, unroofing can provide relief of symptoms refractory to medical therapy.

The impact of myocardial bridge on coronary artery spasm and long-term clinical outcomes in patients without significant atherosclerotic stenosis

BACKGROUND AND AIMS

Myocardial bridge (MB) and coronary artery spasm (CAS) can induce a sustained chest pain, acute coronary syndrome (ACS) and even sudden cardiac death. The aim of this study is to evaluate the relationship between MB and CAS and its impact on long-term clinical outcomes.

METHODS

A total of 812 patients with MB without significant coronary artery disease (CAD), who underwent acetylcholine (ACH) provocation test, were enrolled. Significant CAS was defined as ≥70% temporary narrowing by ACH test, and MB was defined as the characteristic phasic systolic compression of the coronary artery with a decrease of more than 30% in diameter on the angiogram after intracoronary nitroglycerin infusion. To adjust baseline confounders, logistic regression analysis was performed. The primary endpoint was incidence of CAS, and secondary endpoints were major adverse cardiac events (MACE) and recurrent angina requiring repeat coronary angiography (CAG) at 5 years.

RESULTS

MB is closely implicated in a high incidence of CAS, spontaneous spasm, ischemic ECG change and chest pain during ACH provocation test. In addition, MB of various severity and reference vessel size was substantially implicated in CAS incidence, and severe MB was a strong risk factor of CAS. MB patients with CAS were shown to have a higher rate of recurrent angina compared with MB patients without CAS, up to a 5-year follow-up. However, there were no differences regarding the incidence of MACE.

CONCLUSIONS

Severe MB was associated with high incidence of CAS, and MB patients with CAS were likely to have a higher incidence of recurrent angina. Intensive medical therapy and close clinical follow-up are needed for better clinical outcomes in MB patients with CAS.

Cardiovascular consequences of myocardial bridging: A meta-analysis and meta-regression

Myocardial bridging, a congenital abnormality in which a coronary artery tunnels through the myocardial fibres was usually considered a benign condition. Many studies suggested a potential hemodynamic significance of myocardial bridging and some, usually case reports, implied a possible correlation between it and various cardiovascular pathologies like acute myocardial infarction, ventricular rupture, life-threatening arrhythmias, hypertrophic cardiomyopathy, apical ballooning syndrome or sudden death. The main objective of this article is to evaluate whether myocardial bridging may be associated with significant cardiac effects or if it is strictly a benign anatomical variation. To this purpose, we performed a meta-analysis (performed using the inverse variance heterogeneity model) and meta-regression, on scientific articles selected from three main databases (Scopus, Web of Science, Pubmed). The study included 21 articles. MB was associated with major adverse cardiac events - OR = 1.52 (1.01–2.30), and myocardial ischemia OR = 3.00 (1.02–8.82) but not with acute myocardial infarction, cardiovascular death, ischemia identified using imaging techniques, or positive exercise stress testing. Overall, myocardial bridging may have significant cardiovascular consequences (MACE, myocardial ischemia). More studies are needed to reveal/refute a clear association with MI, sudden death or other cardiovascular pathologies.

The Diagnostic Challenge of Dipyridamole-atropine Stress Echocardiography in a Patient with Myocardial Bridge

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.

Different Accumulation of Elements in Proximal and Distal Parts of the Left Anterior Descending Artery Beneath the Myocardial Bridge

To elucidate the action of the myocardial bridge (MB) on the coronary artery, the authors first prepared the hearts with the MB located in the middle one third of the left anterior descending (LAD) artery and then investigated element accumulation in the LAD artery of the hearts with the MB by direct chemical analysis. Eighty-four formalin-fixed adult Thai hearts were dissected and the MBs were found in 39 of 84 hearts with a total of 44 MBs. The 37 MBs were located in the middle one third of the LAD artery. To examine the action of the MB on element accumulation in the LAD artery, the hearts with the MB which was located in the middle one third of the LAD artery and was longer than 1.5 cm were used as Materials. The left main coronary (LMC) and LAD arteries were removed from these hearts successively and the isolated arteries were divided into eight to ten segments. After incineration of arteries with nitric acid and perchloric acid, seven element contents of Ca, P, S, Mg, Zn, Fe, and Na were determined by inductively coupled plasma-atomic emission spectrometry. To examine the endothelial changes of the LAD artery, the inner surface of segments of the LAD artery was observed by scanning electron microscopy. It was found that the extent of accumulation of Ca, P, Zn, and Na was not uniform throughout the LAD artery and was higher in the proximal part than in the distal part with regard to the LAD artery beneath the MB (the tunneled LAD artery). The extent of accumulation of Ca, P, Zn, and Na in the proximal part of the tunneled LAD artery was similar to that in the segments proximal to the MB, whereas the extent of accumulation of Ca, P, Zn, and Na in the distal part of the tunneled LAD artery was similar to that in the segments distal to the MB.

Myocardial bridging analysis by coronary computed tomographic angiography in a Saudi population

AIM: To assess the incidence, location, morphology and clinical association of myocardial bridging in a Saudi population using coronary computed tomographic angiography (CCTA).

METHODS: A total of 350 CCTA of Saudi patients were included in this study (236 men, 114 women) with a mean age of 56.3 years. All patients were examined for appropriateness criteria of CCTA indications (typical chest pain, recent onset cardiomyopathy, left bundle branch block, etc.). The scans were retrospectively reviewed for the presence of myocardial bridging and any other pathological association.

RESULTS: Myocardial bridging was found in 89 of 350 (22.5%) patients. Most of the intramuscular segments were of the superficial type and found in the mid left anterior descending (LAD) (24.6%), followed by distal LAD (3.7%), diagonal branches (2%), ramus intermedius artery (1.4%) and obtuse marginal artery (0.8%). No myocardial bridging was detected in the right coronary or circumflex arteries. No significant differences were found between males and females (P = 0.14). Coronary artery atherosclerosis was found in 51 of 89 (57.3%) patients with MB. Atherosclerotic plaques were not detected in the intramuscular or distal segment of bridging arteries. Dynamic compression was observed in 35 (94.5%) patients with full encasement. No evidence of myocardial hypoperfusion was found in the territories supplied by the bridging arteries.

CONCLUSION: CCTA is excellent in analyzing myocardial bridging in a Saudi population and the results are comparable to other populations. However, finding the real incidence may need a large multicenter study.

Accumulation of calcium and phosphorus in the coronary arteries of Thai subjects

To clarify the manner of accumulation of Ca and P in the coronary arteries, the authors divided the coronary arteries into many segments based on arterial ramification and investigated the element contents of the segments by direct chemical analysis. After ordinary dissection at Chiang Mai University was finished, the left coronary (LC) and the right coronary (RC) arteries were removed successively from the hearts of Thai subjects. The Thai subjects consisted of seven men and five women, ranging in age from 42 to 87 years (average age = 73.9 ± 13.5 years). The LC and the RC arteries were divided into 19 segments based on arterial ramification. After incineration with nitric acid and perchloric acid, element contents of the segments were analyzed by inductively coupled plasma-atomic emission spectrometry. In two cases, a significant content of Ca and P was contained only in the left anterior descending (LAD) artery (type I). In four cases, a significant content of Ca and P was contained in both the LAD and the RC arteries (type II). In five cases, a significant content of Ca and P was contained in all the LAD, the RC, and the circumflex (CF) arteries (type III). In the other one case, no significant content of Ca and P was contained in the coronary arteries. The manner of accumulation of Ca and P in the coronary arteries was classified into the three types, I, II, and III. Regarding the average content of elements in 12 cases, the average content of Ca was the highest in the segment of the LAD artery ramifying the first left diagonal artery and was higher in the proximal and distal adjacent segments of the LAD artery ramifying the first left diagonal artery, the proximal segment of the RC artery, and the proximal segment of the CF artery. To examine an effect of arterial ramification on accumulation of Ca and P, the differences in the Ca and P content between artery-ramifying and non-ramified proximal or distal segments of the coronary arteries were analyzed with Student's t test. It was found that there were no significant differences in the Ca and P content between the artery-ramifying and non-ramified proximal or distal segments of the coronary arteries.

Evaluation of plasma and urinary levels of 6-keto-prostaglandin F1alpha as a marker for asymptomatic myxomatous mitral valve disease in dogs

Endothelial dysfunction might be involved in the pathogenesis of myxomatous mitral valve disease (MMVD). The aims of this study were (1) to validate an enzyme immunoassay (EIA) for canine 6-keto-prostaglandin (PG)F(1alpha) (prostacyclin metabolite and marker for endothelial function) and (2) to compare plasma and urinary 6-keto-PGF(1alpha) in dogs with asymptomatic MMVD. The study included two breeds predisposed to MMVD and two control groups (Cairn terriers and dogs of different breeds). Echocardiography was used to estimate the severity of MMVD. The intra- and inter-assay coefficients of variation were between 3.1% and 24.5% in the assay range. No echocardiographic parameter was correlated with plasma or urinary 6-keto-PGF(1alpha) (P>0.05), but all control dogs had lower urinary 6-keto-PGF(1alpha) (P<0.02) and the Cairn terriers had higher plasma 6-keto-PGF(1alpha) (P<0.02). The EIA appeared valid for measuring canine 6-keto-PGF(1alpha) in plasma and urine. It is suggested that 6-keto-PGF(1alpha) levels are related to breed and not MMVD in asymptomatic stages.

Clinical relevance of myocardial bridging severity: single center experience

BACKGROUND

Myocardial bridging refers to intramyocardial systolic compression of a segment of an epicardial coronary artery. We aimed to identify the clinical significance of myocardial bridging by assessing the clinical presentation in non-obstructive coronary artery disease among a cohort of consecutive patients presenting for coronary angiography.

MATERIALS AND METHODS

A retrospective review of our institution's database between September 2002 and March 2005 was conducted to review coronary angiography reports of 14,416 patients. The study group included 226 patients (prevalence=1.57%) with isolated myocardial bridging and <50% stenosis in the non-bridged arteries. Cases with myocardial bridging were classified according to the percentage of systolic compression of the left anterior descending artery into group I (<50% compression), group II (50-70% compression) and group III (compression >or= 70%).

RESULTS

Mean age was 57.6+/-15.5 years; 59% were men. The mean duration of follow-up was 12+/-2 months. The left anterior descending was the most common site of bridging (210, 93%). There was a significant difference between groups I and III with respect to the percentage of patients who presented with non-fatal myocardial infarction (P=0.02). Unstable angina had the highest association with myocardial bridging, but there was no significance among the level of myocardial bridging severity and the clinical presentation of angina.

CONCLUSIONS

Myocardial bridging is not a benign variation of coronary anatomy. It is associated with angina and myocardial infarction in patients with >or= 70% systolic compression. The bridged segment may be a cause of enhanced atherosclerotic plaque formation.

Apical hypertrophic cardiomyopathy might lead to misdiagnosis of ischaemic heart disease

PURPOSE

In this study, demographic, clinic, electrocardiographic and angiographic properties of patients, on whom coronary angiography was performed with the pre-diagnosis of coronary artery disease (CAD) and whose ventriculography demonstrated typical apical hypertrophic cardiomyopathy (AHCM), were investigated.

METHODS

Seventeen patients (mean age 58 +/- 10 years, 10 male) with CAD pre-diagnosis, on whom coronary angiography was performed and had typical spade-like appearance on left ventriculography, were included in the study between January 2000 and May 2005.

RESULTS

As risk factor for CAD, 8 (47%) patients had hypertension, 8 (47%) patients had dyslipidaemia, 2 (11%) patients had type 2 diabetes mellitus, 13 (77%) patients had a history of smoking, and 2 (11%) patients had family history. Seven (42%) patients presented unstable angina pectoris, 8 (47%) patients presented stable angina pectoris and 2 (11%) patients were asymptomatic. On coronary angiography, it was determined that 10 (58%) patients had normal coronary arteries, 3 (17%) patients had non-significant stenosis and 4 (25%) patients had myocardial bridging. Five (30%) patients revealed mid-ventricular obstruction and intraventricular gradient was 25 +/- 5 mmHg by the catheterization. All patients showed ''giant'' negative (> or = 10 mm) T waves in the precordial leads, whereas 2 patients had atrial fibrillation. Maximum wall thickness was measured as 18 +/- 4 mm in the apical region by transthoracic echocardiography. One patient (5%) who had mid-ventricular obstruction developed atrial fibrillation during 2 years follow-up, though any other events did not occur during hospitalization or follow-up period.

CONCLUSIONS

Physicians caring for patients with chest pain should consider AHCM in their differential diagnosis in case of a patient with chest pain and electrocardiographic changes suggestive of CAD.