The fundamental role of stress echo in evaluating coronary artery disease in specific patient populations

Stress echocardiography (SE) was initially used for assessing patients with known or suspected coronary heart disease by detecting and evaluating myocardial ischemia and viability. The implementation of SE has gradually been extended to several cardiovascular diseases beyond coronary artery disease, and SE protocols have been modified and adapted for the detection of coronary artery disease (CAD) or other cardiovascular diseases in specific patient populations. This review attempts to summarize current data concerning SE implementation and clinical value in these specific and diverse populations: patients with an intramural course of a coronary artery - known as a myocardial bridge, chronic severe or end-stage hepatic disease, chronic severe or end-stage kidney disease, cardiac allograft vasculopathy, patients scheduled for solid-organ transplantation and other intermediate and high-risk surgery and, finally, patients treated with anticancer drugs or radiotherapy.

Septal hematoma due to stent implementation in the septal course of the left anterior descending artery

BACKGROUND

The interventricular septal hematoma (IVSH) is a rare and potentially lethal finding. There are variously reported etiologies including instrumental damages during cardiac interventions. Although there are not enough studies available, conservative management is considered as a preferable approach in stable patients.

CASE REPORT

A 45-year man smoker with the previous history of percutaneous coronary intervention (PCI), admitted with unstable angina in present visit. Coronary angiography showed significant in-stent restenosis (ISR) of the left anterior descending (LAD) artery stent. During our intervention for treatment of the ISR, the wire movement caused a diffuse dissection without any runoff, in the distal portion of the LAD. Therefore two stents were deployed in the dissected segment with a short overlapping segment. Unfortunately, the overlapping segment of these stents was located in the myocardial bridge segment. Therefore the contraction of the interventricular septum (IVS) caused a scissor-like movement of the stents, and they ruptured the LAD into the septum. Therefore, the contrast agent was accumulated in the IVS. Immediately, a graft stent was deployed in the overlapping segment of stents and perforation became sealed. In echocardiography, the IVS diameter increased to 30 mm. Since the patient was hemodynamically and electrically stable, he underwent conservative approach and after two months the septum returned to the normal size.

CONCLUSION

During PCI on the LAD artery, the implantation of stents in the septal course with a short overlapping segment can result in coronary perforation, and therefore IVS hematoma by the scissor effect. Septal hematoma may cause life-threatening arrhythmias or ventricular septal rupture, but if it is asymptomatic or uncomplicated. Conservative management is the best strategy.

Increased risk of coronary perforation during percutaneous intervention of myocardial bridge: What histopathology says

Introduction: Myocardial bridge (MB) is a segment of a major epicardial coronary artery that goes intramurally under a bridge of overlying myocardium. Complications have been reported during or after stent implantation particularly coronary perforation. The aim of this study was to determine histological differences between proximal left anterior descending artery (LAD) and the tunneled segment that may have a possible role in increased risk of coronary artery perforation during percutaneous coronary intervention.

Methods: Twenty specimens of MB were obtained from dissection of 45 cadavers. Sections were stained using hematoxylin and eosin (H&E), and trichrome methods. The proximal section and the tunneled artery were compared with a normal sample in terms of the characteristics of a muscle artery.

Results: The findings of this study showed an MB prevalence of 51%, as 23 out of the 45 examined cadavers were discovered to be afflicted by the MB. The intima layer in the suffering artery had gone through significant hypertrophy, while it had remained thin in the tunneled artery section. The epithelial cells under the bridge were spindle-shaped, while they were polygonal in the proximal section. In the myocardium the nuclei of the muscle fibers in the MB section were smaller than the normal section. Adventitial layer was almost normal.

Conclusion: The histopathological differences between MB and proximal part of vessel combined with small vessel diameter in the tunneled segment can explain the high incidence of the LAD rupture and perforation in the section under the bridge.

The role of septal perforators and "myocardial bridging effect" in atherosclerotic plaque distribution in the coronary artery disease

The distribution of atherosclerotic plaque burden in the human coronary arteries is not uniform. Plaques are located mostly in the left anterior descending artery (LAD), then in the right coronary artery (RCA), circumflex branch (LCx) and the left main coronary artery (LM) in a decreasing order of frequency. In the LAD and LCx, plaques tend to cluster within the proximal segment, while in the RCA their distribution is more uniform. Several factors have been involved in this phenomenon, particularly flow patterns in the left and right coronary artery. Nevertheless, it does not explain the difference in lesion frequency between the LAD and the LCx as these are both parts of the left coronary artery. Branching points are considered to be the risk points of atherosclerosis. In the LCx, the number of side branches is lower than in the LAD or RCA and there are no septal perforators with intramuscular courses like in the proximal third of the LAD and the posterior descending artery (PDA). We hypothesized that septal branches generate disturbed flow in the LAD and PDA in a similar fashion to the myocardial bridge (myocardial bridging effect). This coronary architecture determines the non-uniform plaque distribution in coronary arteries and LAD predisposition to plaque formation.

Morphology of human myocardial bridges and association with coronary artery disease

BACKGROUND

The functional significance of myocardial bridging remains controversial. The bridge morphology and structure of the tunneled vessels may modify its ultimate clinical effects.

OBJECTIVE

To describe the morphological characteristics of myocardial bridges and their influence on coronary histology.

DESIGN

A descriptive cross-sectional study.

METHODS

One hundred and nine formalin-fixed adult hearts were evaluated by dissection for these data: prevalence, site, lengths and depths of myocardial bridges. Vessel segments proximal and distal to the bridged portion were also processed for histology and stained to elaborate smooth muscle, collagen and elastic fibers. Stereology was also employed to compare the relative sizes of the tunica intima and the vessel wall to lumen ratios.

RESULTS

Myocardial bridges were found in 40.4% of the hearts, most commonly in the left anterior descending artery (LAD). The average length of the bridges was 22.66 +11.94 mm while the depth was 1.83+ 0.98mm, with only 11% being long (34.87mm - 50mm) and 9% of them being deep (3.46mm - 5.00mm). The tunica intima was thickest proximal to and thinnest under the myocardial bridge. The intima of the proximal segment was also more elastic. An elaborate perivascular 'cushion' of adipose tissue intervened between the intramural coronary and the surrounding myocardium.

CONCLUSIONS

Most myocardial bridges are superficial and short. Tunica intima under myocardial bridges is spared from "atherogenesis". The thick perivascular space around the bridged segment may protect it from extreme compression.