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

Segmental myocardial tissue remodeling and atrial arrhythmias in hypertrophic cardiomyopathy: Findings from T1-mapping MRI

BACKGROUND

Myocardial fibrosis of the left ventricle (LV) has been associated with atrial fibrillation and other arrhythmias in individuals with hypertrophic cardiomyopathy (HCM). However, few studies have quantitatively examined the segmental relationship between diffuse LV fibrosis and atrial arrhythmias in HCM using T1 mapping and extracellular volume fraction (ECV). The aim of this study is to explore this relationship through T1 mapping, offering imaging insights into the pathophysiology of HCM with atrial arrhythmia.

METHODS

A total of 38 patients with HCM were classified into two groups-those with atrial arrhythmia and those without-based on electrocardiographic and Holter monitor recordings. A covariance analysis was conducted to compare T1 mapping parameters between the two groups, adjusting for wall thickness (WT) as a covariate. Analysis was performed collectively for all 16 myocardial segments, as well as for each segment individually.

RESULTS

Native T1 values were elevated in the entire LV myocardium and in segments S1-3 in patients with HCM with atrial arrhythmias compared to those without (P < 0.001; P < 0.05, 1316.0 ms ± 15.9 vs 1263.1 ms ± 13.6, 1350.5 ms ± 14.2 vs 1311.9 ms ± 11.7, 1305.7 ms ± 2.5 vs 1271.5 ms ± 10.6, respectively). Notably, the basal anterior segment (S1) and basal inferotseptal segment (S3) exhibited prolonged ECV and elevated native T1 values in patients with HCM and atrial arrhythmia (P < 0.05). Multivariable binary logistic regression analysis identified myocardial native T1 values in the basal anteroseptal segment (S2) as a predictor of atrial arrhythmia presence in HCM, with values exceeding 1350 ms correlating with an increased likelihood of arrhythmia development. No significant difference in WT was observed between the groups in hypertrophic myocardial regions (P > 0.05), while non-hypertrophic myocardium in individuals with HCM and atrial arrhythmias exhibited reduced wall thickness (7.7 mm ± 3.0 vs 9 mm ± 3.0, P < 0.001) compared to those without arrhythmias.

CONCLUSION

Fibrosis in the basal septal and anterior regions of the left ventricle plays a crucial role in myocardial tissue remodeling, contributing to the development of atrial arrhythmia in HCM. Elevated native T1 values in the basal anteroseptal segment may may serve as a significant marker for the concurrent occurrence of atrial arrhythmias in individuals with HCM.

Myocardial ischemia caused by the synergistic effect of myocardial bridge and moderate stenosis: case report

BACKGROUND

Clinical events such as angina pectoris, acute coronary syndrome, and sudden death caused by myocardial bridge (MB) have attracted increasing attention. It is still a challenge to diagnose whether MB can cause the symptoms of patients with MB. For most MB patients, medication remains the primary treatment.

CASE PRESENTATION

This article reports a case of chest pain in a patient with MB in the middle segment of the left anterior descending artery (LADm) with moderate stenosis in the proximal segment (LADp). Through functional assessment, we found that neither MB nor fixed stenosis had sufficient effect on coronary blood flow to cause myocardial ischemia, but their synergistic effect resulted in myocardial ischemia. Finally, a stent was implanted in LADp and good clinical results were achieved.

CONCLUSIONS

For symptomatic patients with MB combined with fixed stenosis, functional evaluation may be necessary, which has significant guiding significance for treatment strategy selection. For asymptomatic patients, early detection of myocardial ischemia may also improve the prognosis of patients.

Myocardial bridging in obstructive hypertrophic cardiomyopathy: a risk factor for myocardial fibrosis

BACKGROUND

Myocardial bridging (MB) is common in patients with hypertrophic cardiomyopathy (HCM). There are sparse data on the impact of MB on myocardial fibrosis in HCM. This study was designed to evaluate the relationship between MB and myocardial fibrosis in patients with obstructive HCM.

METHODS

In this cohort study, retrospective data were collected from a high-volume HCM center. Patients with obstructive HCM who underwent septal myectomy and preoperative cardiac magnetic resonance (CMR) were screened from 2011 to 2018.

RESULTS

Finally, 492 patients were included in this study, with an average age of 45.7 years. Of these patients, 76 patients had MB. MB occurred mostly in the left anterior descending artery (73/76). The global extent of late gadolinium enhancement (LGE) was correlated with the degree of systolic compression (r = 0.33, p = 0.003). Multivariable linear regression analysis revealed that the degree of systolic compression was an independent risk factor for LGE (β = 0.292, p = 0.007). The LGE fraction of basal and mid anteroseptal segments in patients with severe MB (compression ratio ≥ 80%) was significantly greater than that in patients with mild to moderate MB (compression ratio < 80%). During a median follow-up of 28 (IQR: 15-52) months, 15 patients died. Kaplan-Meier analysis did not identify differences in all-cause death (log-rank p = 0.63) or cardiovascular death (log-rank p = 0.72) between patients undergoing MB-related surgery and those without MB.

CONCLUSIONS

MB with severe systolic compression was significantly associated with a high extent of fibrosis in patients with obstructive HCM. Concomitant myotomy or coronary artery bypass grafting might provide excellent survival similar to that of patients without MB. Identification of patients with severe MB and providing comprehensive management might help improve the prognosis of patients with HCM.

Relationship between myocardial bridging and fatal ventricular arrhythmias in patients with hypertrophic cardiomyopathy: the HCM-MB study

BACKGROUND

Myocardial bridging (MB) and hypertrophic cardiomyopathy (HCM) are associated with the risk of fatal ventricular arrhythmias (VAs). The goal of the study was to determine the relationship between MB and fatal VAs in HCM patients with implantable cardiac defibrillators (ICD).

METHODS

A total of 108 HCM patients (mean age: 46.6 ± 13.6 years; male: 73) were enrolled in this retrospective study. All patients underwent transthoracic echocardiography and coronary computed tomography angiography. Fatal VAs including sustained ventricular tachycardia and ventricular fibrillation were documented in ICD records.

RESULTS

There were documented fatal VAs in 29 (26.8%) patients during a mean follow-up time of 71.3 ± 30.9 months. Compared with the other groups, the fatal VA group had a higher incidence of the following: presence of MB (82.8 vs. 38%, p < 0.001), deep MB (62.1 vs. 6.3%, p < 0.001), very deep MB (24.1 vs. 0%, p < 0.001), long MB (65.5 vs. 11.4%, p < 0.001), presence of > 1 MB (17.2 vs. 0%, p = 0.001), and MB of the left anterior descending artery (79.3 vs. 17.7%, p < 0.001) . Sudden cardiac death (SCD) risk score (hazard ratio: 1.194; 95% CI: 1.071-1.330; p = 0.001) and presence of MB (hazard ratio: 3.815; 95% CI: 1.41-10.284; p = 0.008) were found to be independent predictors of fatal VAs in HCM patients.

CONCLUSIONS

The current data suggest that the SCD risk score and presence of MB were independent risk factors for fatal VAs in patients with HCM. In addition to conventional risk factors, the coronary anatomical course can provide clinicians with valuable information when assessing the risk of fatal VAs in HCM patients.

The relationship between CTA performances and cardiac function indicators in myocardial bridge and mural coronary artery

OBJECTIVE

To investigate the relationship between computed tomography angiography (CTA) performances and cardiac function indicators in patients with myocardial bridge and mural coronary artery (MB-MCA).

METHODS

The clinical data of 60 patients with MB-MCA receiving CTA in the First Hospital of Zhangjiakou from January 2021 to February 2022 were analyzed retrospectively. The patients were divided into different groups based on CTA performances, including the degree of stenosis of the left anterior descending (LAD) MCA, whether there was atherosclerosis in the anterior segment of MB of LAD branch, the MB thickness, and the degree of stenosis of the LAD branch. The correlation between these TCA performances and cardiac function indicators including end-systolic volume (ESV), end-diastolic volume (EDV), stroke volume (SV), cardiac output (CO), and left ventricular ejection fraction (LVEF) was analyzed. Besides, the receiver operating characteristic (ROC) curve was used to analyze the predictive performance of cardiac function indicators for the severity of MB-MCA.

RESULTS

ESV, EDV, SV, CO and LVEF were statistically different between the moderate stenosis group and mild stenosis group (all P < 0.05). EDV, SV, CO, and LVEF were statistically different between the atherosclerosis group and non-atherosclerosis group (all P < 0.05). SV, CO, LVEF in the deep group were lower than that in the superficial group (all P < 0.05). EDV, CO, LVEF were different between the LAD moderate stenosis group and LAD mild stenosis group (all P < 0.05). The AUC (areas under the curve) of combined detection of ESV, EDV, SV, CO, and LVEF in predicting the severity of MB-MCA was 0.907, which was higher than the single indicator predictive effect.

CONCLUSIONS

Cardiac function indicators, mainly CO and LVEF are correlated with the CTA performance of MB-MCA patients. The combination of cardiac function indicators has a good effect in predicting the severity of MB-MCA.

Systematic Review and Meta-Analysis of Cardiovascular Consequences of Myocardial Bridging in Hypertrophic Cardiomyopathy

Myocardial bridging (MB) is a congenital variant in which a segment of a coronary artery follows an atypical intramural course under a "bridge" of myocardium and is notably common in hypertrophic cardiomyopathy (HCM). This systematic review and meta-analysis explored the clinical consequences of MB in patients with HCM. A total of 3 outcome domains were investigated: cardiovascular mortality, nonfatal adverse cardiac events, and investigative indicators of myocardial ischemia. A meta-analysis was performed on 10 observational studies comparing outcomes in patients with HCM with and without MB. Studies were identified through a systematic search of 4 databases (PubMed, Scopus, Medline Complete, and Web of Science). The quality of the studies was assessed using a modified version of the Downs and Black tool, from which studies could score a maximum of 23 points. The mean score was 17.5 ± 1.3 (good). The meta-analysis showed that MB was not associated with cardiovascular mortality (odds ratio [OR] 1.70, 95% confidence interval [CI] 0.56 to 5.15, p = 0.35) or nonfatal adverse cardiac events (OR 1.80, 95% CI 0.98 to 3.28, p = 0.06) but was associated with myocardial ischemia (OR 1.89, 95% CI 1.03 to 3.44, p = 0.04). In conclusion, the potential prognostic implications of MB in HCM, especially in those with hemodynamically significant bridges and/or severe underlying disease, should not be ignored. The focus of future studies should be to establish functional and morphologic thresholds, by which MB may adversely influence prognosis by corroborating imaging findings with clinical outcome data.