Clinical anatomy of internal thoracic artery branches

Up-to-Date, Skeletonized or Pedicle Bilateral Internal Mammary Artery; Does It Matter?

PURPOSE

In this article, we reported on the up-to-date literature regarding skeletonized bilateral internal mammary artery (BIMA) flow and the effect on sternal perfusion. We also reviewed the pros and cons of the skeletonization technique versus the conventional pedicle technique for harvesting the BIMA.

METHODS

We performed an up-to-date review using the PubMed database, with a specific focus on the contemporary published literature.

RESULTS

BIMA skeletonization can preserve the sternal microcirculation, minimize tissue damage, and maintain blood supply to the chest wall at the tissue level. This effect is also apparent in diabetics. Deep sternal wound infection (DSWI) rates are significantly less with skeletonization versus the conventional pedicle technique and are comparable to single internal mammary artery harvesting.

CONCLUSIONS

Contemporary large-scale studies demonstrate that skeletonization of the BIMA increases conduit length, provides superior flow, reduces the incidence of DSWIs, and improves late survival. Hopefully, this review will increase awareness of the compelling evidence in favor of using skeletonized internal mammary arteries and stimulate increased uptake of BIMA revascularization surgery.

Clinical Application of the Internal Mammary Artery Perforator Adipofascial Flap

Background:

Skin ulcers on the anterior chest wall are caused mainly by radiation therapy for breast cancer and anterior mediastinitis after thoracotomy, and they are often refractory. Some muscle flaps are commonly used for anterior chest wall reconstruction, but muscle flaps accompany high invasion. We used the internal mammary artery perforator (IMAP) adipofascial flap and IMAP skin flap for the anterior chest wall reconstruction.

Methods:

We examined the IMAPs using a handheld Doppler device and contrast-enhanced computerized tomography preoperatively. Each flap was designed based on the location of the IMAP and the size of the flap was dependent on the coverage required by the size and location of the skin ulcer. The location of the IMAPs functioned as the pivot point of the flap and the flap was flipped or swung on the defect.

Results:

We used IMAP adipofascial flap for 2 cases and IMAP skin flap for 1 case. In those 3 cases, we could elevate the flap with no complications even after the internal mammary artery had been harvested. There was no recurrence of the skin ulcer or wound infection after the operation.

Conclusions:

In this study, we reported 3 cases of skin ulcer on the anterior chest wall reconstructed with the IMAP adipofascial and skin flap. To our knowledge, this is the first report of the use of the IMAP flap as an adipofascial flap. The IMAP adipofascial flap accompanies less invasion than muscle flaps and the surgical procedure is relatively easy. The IMAP adopofascial flap is considered as one of the effective means for anterior chest wall reconstruction.

Anatomic study of the vascular perfusion of the sternum and its clinical relevance in deep sternal wound infection

Introduction: Deep sternal wound infections (DSWI) are a rare but devastating complication after median sternotomy. Minor perfusion in bone and soft tissue, especially after recruiting the internal mammary artery for bypass supports the development of wound infection and nonunion of the sternal bone.

The aim of the study was the macroscopic and radiological presentation of the vascular system supplying the sternum, in particular the compensating blood supply routes in the event that the internal mammary artery is no longer available after use as a bypass vessel.

Method: This anatomic study was carried out on the anterior chest wall of 7 specimens. The thorax plates of 7 specimens were analyzed macroscopically after microsurgical preparation. Different anatomic preparations were produced using different contrast or form-giving substances. Radiological analysis and three-dimensional reconstructions were performed to show alternative, collateral sternal vessel perfusion under estimation of the loss of the internal thoracic artery due to a bypass.

Results: The length of the ITA (internal thoracic artery), measured from the beginning of the first rib to the division into the superior epigastric artery and musculophrenic artery, was an average of 16.3 cm. On average, 18.5 branches were delivered from each artery, 10 medially to the sternum supply, and 8 to the intercostal muscle.

Conclusion: Our analysis gives an overview of the macroanatomic vessel system supplying the sternal bone, describing especially a common trunk deriving from the ITA and supplying multiple branches and playing an important role in building a collateral circulation of the sternum.

For better evaluation, in vivo CT analysis with contrast media should be performed in patients prior to the operation and directly after the use of the double ITA to demonstrate the change in perfusion of the sternum.

In the future, preconditioning of the sternum by coiling the deriving branches could become an option, although patient selection has to be improved and further analysis of the topic performed.

Comparison of the Fluid Resuscitation Rate with and without External Pressure Using Two Intraosseous Infusion Systems for Adult Emergencies, the CITRIN (Comparison of InTRaosseous infusion systems in emergency medicINe)-Study

INTRODUCTION

Intraosseous infusion is recommended if peripheral venous access fails for cardiopulmonary resuscitation or other medical emergencies. The aim of this study, using body donors, was to compare a semi-automatic (EZ-IO®) device at two insertion sites and a sternal intraosseous infusion device (FASTR™).

METHODS

Twenty-seven medical students being inexperienced first-time users were randomized into three groups using EZ-IO and FASTR. The following data were evaluated: attempts required for successful placement, insertion time and flow rates with and without external pressure to the infusion.

RESULTS

The first-pass insertion success of the EZ-IO tibia, EZ-IO humerus and FASTR was 91%, 77%, and 95%, respectively. Insertion times (MW ± SD) did not show significant differences with 17 ± 7 (EZ-IO tibia) vs. 29 ± 42 (EZ-IO humerus) vs. 33 ± 21 (FASTR), respectively. One-minute flow rates using external pressures between 0 mmHg and 300 mmHg ranged between 27 ± 5 to 69 ± 54 ml/min (EZ-IO tibia), 16 ± 3 to 60 ± 44 ml/min (EZ-IO humerus) and 53 ± 2 to 112 ± 47 ml/min (FASTR), respectively. Concerning pressure-related increases in flow rates, negligible correlations were found for the EZ-IO tibia in all time frames (c = 0.107-0.366; p ≤ 0.013), moderate positive correlations were found for the EZ-IO humerus after 5 minutes (c = 0.489; p = 0.021) and strong positive correlations were found for the FASTR in all time frames (c = 0.63-0.80; p ≤ 0.007). Post-hoc statistical power was 0.62 with the given sample size.

CONCLUSIONS

The experiments with first-time users applying EZ-IO and FASTR in body donors indicate that both devices may be effective intraosseous infusion devices, likely suitable for fluid resuscitation using a pressure bag. Variations in flow rate may limit their reliability. Larger sample sizes will prospectively be required to substantiate our findings.

Factors influencing the diameter of human anterior and posterior intercostal arteries

At present, there have not been any detailed studies examining the size relationships of the intercostal arteries. This study was carried out to investigate the relationship between the vessel lumenal diameter of ipsilateral, paired anterior and posterior IC arteries, as well as with the length of the IC space supplied by each artery. Samples were collected from the second-sixth anterior and posterior IC arteries near their site of origin, and the lengths of the corresponding IC spaces were measured in 42 cadavers. Lumenal diameters of both the anterior and posterior IC arteries at consecutive IC space closely followed second degree polynomial regression models (R(2) = 0.9655, and R(2) = 0.9741, respectively), and reached maximum size at the fifth IC space, which was found to be the longest of the IC spaces. No direct relationship was observed between diameters of the paired anterior and posterior IC arteries, although there was a trend for the larger anterior IC arteries to be paired with the larger posterior IC arteries. The calculated rate of blood flow at each IC artery was approximately two-fold greater in males than in females. These results suggest that the length of the IC space, and hence the extent of the thoracic wall supplied, is a major factor in determining the diameter of both anterior and posterior IC arteries. Since COPD is such a prevalent disease, this study also examined its influence on the IC arteries, and found that the posterior IC arteries are significantly larger among afflicted subjects.

Abnormal origin of internal thoracic artery from the thyrocervical trunk: surgical considerations

An unusual case of left internal thoracic artery (ITA) origin from the thyrocervical trunk (TCT) was detected during routine cadaver dissection. The variability of origin and course of ITA has less or more frequently been documented in the literature. However, the ITA origin from the TCT on the left side has been detected less commonly, making its dissection and preparation during coronary artery bypass grafting surgery more difficult. We discuss the ITA origin and course variability as well as clinical significance of the present variant, reviewing the relative literature. The objective of our study is to exhibit a rare ITA origin in order to provide a more accurate knowledge of such variations.

Extra-anatomical revascularization of the Adamkiewicz artery using the internal mammary artery: preliminary anatomical study

Ischemic spinal cord injury remains a major complication of both open and endovascular repairs of extensive lesions of the thoracic or thoracoabdominal aorta. Patients undergoing endovascular treatment cannot benefit from direct revascularization of the Adamkiewicz artery (AA). Primary revascularization of the intercostal artery (ICA) giving rise to the AA using the internal mammary artery (IMA) could ensure uninterrupted flow in the AA even if the origin of the feeding ICA was obstructed. The purpose of this study was to assess the anatomical feasibility of revascularization of the ICA giving rise to the AA using the IMA. Twenty-four dissections were carried out on 12 cadavers (eight men, four women) with a mean age of 76 at the time of death. Preparation consisted of intra-arterial injection of polymethylsiloxane (Rhodorsil, Rhodia, France). For each IMA, the following parameters were determined: diameter in relation to the ICA in the paravertebral region before division, length, and level of the intercostal space in which direct anastomosis was possible. Dissection showed that the mean diameter at the end of the IMA was 1.8mm (range 1.2-2.4). The mean diameter of the ICA in the paravertebral region was compatible with that of the IMA, i.e., 1.6mm (range 0.9-2.5). The mean length of the IMA was 185 mm (range 165-230). The lowest intercostal space available in the paravertebral region for direct anastomosis between the IMA and ICA was the seventh space in one case, the eighth in 12, the ninth in eight, and the tenth in three. The findings of this preliminary study document the feasibility of using the IMA to revascularize the ICA in the paravertebral region. This technique could provide a means of preserving spinal cord vascularization during endovascular treatment of thoracic or thoracoabdominal aortic lesions.

Blood supply of the sternum and its importance in internal thoracic artery harvesting

BACKGROUND

The internal thoracic artery (ITA) is the conduit of choice in coronary bypass grafting, due to the excellent long-term results achieved using it. However, increased incidence of sternal infections after pedicled ITA harvesting has revived interest in the morphology of sternal blood supply. Our aim was to discuss the topography of the sternal branches with emphasis on internal thoracic artery harvesting.

METHODS

This study was conducted on 50 fresh specimens of the anterior thorax wall. Radio-opaque material was injected and angiograms of the ITA were performed. Subsequently, the specimens were preserved and a dry dissection of each ITA and its branches was carried out.

RESULTS

In dry dissected specimens, four types of vessels were identified that have the potential to carry blood to the sternum after harvesting the ITA. In the first group, the artery to the sternum also supplies the intercostal space. In the second morphologic variant, the sternal branch gives off the perforating and anterior intercostal arteries. In the third group, we classified the common branch of the sternal and perforating arteries. In the fourth group, the sternal artery originated from the ITA as an independent branch.

CONCLUSIONS

For sternal-intercostal, perforating-intercostal, and sternal-perforating branches to function as collaterals after ITA harvesting, the common trunk of origin must remain intact. Based on morphologic data, we recommend ligating the common trunk as close as possible to the ITA; in this way, collateral blood flow to the sternum remains intact.

Gelatin sheet incorporating basic fibroblast growth factor enhances sternal healing after harvesting bilateral internal thoracic arteries

OBJECTIVE

We previously reported that a gelatin sheet incorporating basic fibroblast growth factor accelerated sternal healing after bilateral internal thoracic artery removal in normal and diabetic rats. The aim of this study was to evaluate the effects of this therapeutic modality on sternal healing in a large-animal model before performing a clinical trial.

METHODS

After median sternotomy and bilateral internal thoracic artery removal in a pedicled fashion, 14 beagle dogs received either a gelatin sheet incorporating basic fibroblast growth factor (100 mug per sheet) on the posterior table of the sternum (FGF group, n = 7) or did not receive a gelatin sheet (control, n = 7). We compared sternal healing 4 weeks after surgical intervention between the groups.

RESULTS

Scintigraphic images obtained by using technetium 99 methylene diphosphonate bone scanning were assessed visually, and the impulse rate was quantified 30 and 60 minutes after injection of technetium 99 methylene diphosphonate to evaluate the sternal perfusion. Sternal uptake was significantly increased in the FGF group (30 minutes: 221% +/- 30% vs 180% +/- 36%; 60 minutes: 267% +/- 26% vs 197% +/- 42%; P <.01). Apparent sternal dehiscence, as assessed radiographically, was observed only in the control animals. Histologically, complete healing of the sternum with marked angiogenesis was observed in the FGF group, whereas poor healing with limited angiogenesis was seen in the control animals. Both bone mineral content (134 +/- 49 vs 52 +/- 32 mg, P <.01) and bone mineral density (133 +/- 53 vs 66 +/- 32 mg/mm(2), P <.05) along the incision line of the sternum, as assessed by means of dual-energy x-ray absorptometry, were higher in the FGF group.

CONCLUSIONS

A gelatin sheet incorporating basic fibroblast growth factor enhances sternal perfusion and accelerates sternal bone healing in large animals.23