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Over the years, so-called univentricular hearts represented one of the greatest challenges for surgical correction. All this changed with the advent of the Fontan procedure,1 along with the realization that it could become the final stage of the sequence of procedures used to correct lesions such as those included in the hypoplastic left heart syndrome,2 which previously had been beyond surgical repair. The overall group of lesions also posed significant problems in adequate description and categorization. Even these days, many continue to describe patients with a double inlet left ventricle as having a single ventricle, despite the fact that, with the availability of clinical diagnostic techniques producing three-dimensional datasets, patients with this lesion can be seen to have two chambers within their ventricular mass, one being large and the other small (Figure 9.1.1). The semantic problems with description can now be resolved by the simple expedient of describing the patients as having functionally univentricular hearts.3
Understanding the anatomy of septal defects is greatly facilitated if the heart is thought of as having three distinct septal structures: the atrial septum, the atrioventricular septum, and the ventricular septum (Figure 8.1.1). The normal atrial septum is relatively small. It is made up, for the most part, by the floor of the oval fossa. When viewed from the right atrial aspect, the fossa has a floor, surrounded by rims. As we have shown in Chapter 2, the floor is derived from the primary atrial septum, or septum primum. Although often considered to represent a secondary septum, or septum secundum, the larger parts of the rims, specifically the superior, antero-superior, and posterior components, are formed by infoldings of the adjacent right and left atrial walls.1 Infero-anteriorly, in contrast, the rim of the fossa is a true muscular septum (Figure 8.1.2).
It is axiomatic that a thorough knowledge of valvar anatomy is a prerequisite for successful surgery, be it valvar replacement or reconstruction. The surgeon will also require a firm understanding of the arrangement of other aspects of cardiac anatomy to ensure safe access to a diseased valve or valves. These features were described in the previous chapter. Knowledge of the surgical anatomy of the valves themselves, however, must be founded on appreciation of their component parts, the relationships of the individual valves to each other, and their relationships to the chambers and arterial trunks within which they reside. This requires understanding of, first, the basic orientation of the cardiac valves, emphasizing the intrinsic features that make each valve distinct from the others. Such information must then be supplemented by attention to their relationships with other structures that the surgeon must avoid, notably the conduction tissues and the major channels of the coronary circulation.
The surgical problems posed by cardiac malformations may be considerably increased when the heart itself is in an abnormal position. This is, in part, due to the unusual anatomical perspective presented to the surgeon because of the malposition, and also to the abnormal locations of the cardiac chambers, which may necessitate approaches other than those already discussed. Cardiac malposition in itself, nonetheless, does not constitute a diagnosis. Any normal or abnormal segmental combination can be found in a heart which itself is abnormally located. The heart may be normal, despite its abnormal location, but extremely complex anomalies are frequently present. Consequently, the very presence of an abnormal cardiac position emphasizes the need for a full and detailed segmental analysis of the heart. All the rules enunciated in Chapter 7 apply should the heart not be in its anticipated position.
Systems for describing congenital cardiac malformations have frequently been based on embryological concepts and theories. As useful as these systems have been, they have often had the effect of confusing the clinician, rather than clarifying the basic anatomy of a given lesion. As far as the surgeon is concerned, the essence of a particular malformation lies not in its presumed morphogenesis, but in the underlying anatomy. An effective system for describing this anatomy must be based on the morphology as it is observed. At the same time, it must be capable of accounting for all congenital cardiac conditions, even those that, as yet, might not have been encountered. To be useful clinically, the system must be not only broad and accurate, but also clear and consistent. The terminology used, therefore, should be unambiguous. It should be as simple as possible. The sequential segmental approach provides such a system.1
The coronary circulation consists of the coronary arteries and veins, together with the lymphatics of the heart. Since the lymphatics, apart from the thoracic duct, are of very limited significance to operative anatomy, they will not be discussed at any length in this chapter. The veins, relatively speaking, are similarly of less interest. In this chapter, therefore, we concentrate on those anatomical aspects of arterial distribution that are pertinent to the surgeon, limiting ourselves to brief discussions of the cardiac venous drainage and the cardiac lymphatics.
When we describe the heart in this chapter, and in subsequent chapters, our account will be based on the organ as viewed in its anatomical position.1 Where appropriate, the heart will be illustrated as it would be viewed by the surgeon during an operative procedure, irrespective of whether the pictures are taken in the operating room, or are photographs of autopsied hearts. When we show an illustration in non-surgical orientation, this will be clearly stated.
In the normal individual, the heart lies in the mediastinum, with two-thirds of its bulk to the left of the midline (Figure 1.1). The surgeon can approach the heart, and the great vessels, either laterally through the thoracic cavity, or directly through the mediastinum anteriorly. To make such approaches safely, knowledge is required of the salient anatomical features of the chest wall, and of the vessels and the nerves that course through the mediastinum (Figure 1.2).
Regardless of the surgical approach, once having entered the mediastinum, the surgeon will be confronted by the heart enclosed in its pericardial sac. In the strict anatomical sense, this sac has two layers, one fibrous and the other serous. From a practical point of view, the pericardium is essentially the tough fibrous layer, since the serous component forms the lining of the fibrous sac, and is reflected back onto the surface of the heart as the epicardium. It is the fibrous sac, therefore, which encloses the mass of the heart. By virtue of its own attachments to the diaphragm, it helps support the heart within the mediastinum. Free-standing around the atrial chambers and the ventricles, the sac becomes adherent to the adventitial coverings of the great arteries and veins at their entrances to and exits from it, these attachments closing the pericardial cavity.1
The disposition of the conduction system in the normal heart has already been emphasized (see Chapter 2). In that earlier chapter, we pointed to the importance, during surgical procedures, of avoiding the cardiac nodes and ventricular bundle branches, and scrupulously protecting the vascular supply to these structures. In this chapter, we will consider the anatomy of these tissues relative to the treatment of intractable problems of cardiac rhythm, specifically the normal and abnormal atrioventricular conduction axis. The abnormal dispositions of the conduction tissues to be found in congenitally malformed hearts, features of obvious significance to the congenital cardiac surgeon, will be discussed in the sections devoted to those lesions in the chapters that follow. In this chapter, nonetheless, we will also discuss surgical procedures performed to treat arrhythmias that develop in the setting of the Fontan circulation.
Abnormal systemic venous connections are usually of little surgical significance, since their clinical consequences are limited, although in the severest form, totally anomalous connection, the changes can be profound. Fortunately, totally anomalous systemic venous connection is very rare. The less severe variants are more likely to be encountered as the surgeon pursues a more complex associated intracardiac anomaly, such as the sinus venosus interatrial communication. The anomalous connections in general are of most significance in the setting of isomeric atrial appendages, which we discuss in Chapter 11, emphasizing how so-called visceral heterotaxy is best considered in terms of right versus left isomerism. In this chapter, we consider the features of the anomalous systemic venous connections in their own right. They may be grouped into the categories of absence or abnormal drainage of the right caval veins, persistence or abnormal drainage of the left caval vein, abnormal hepatic venous connections, and totally anomalous systemic venous connections.
This classic textbook on cardiac anatomy has been updated in its fifth edition with additional high quality surgical and pathological photographs, as well as new information and recent findings of the last decade. Beginning with an overview of surgical approaches to the heart, the book goes on to discuss the surgical anatomy of the cardiac chambers, the valves, and the circulation and conduction system within the heart, moving on to cover malformations, lesions, and abnormalities. This edition is informed by the most up-to-date research findings, and a new chapter has been added which reviews cardiac development. A complimentary digital companion now accompanies the book, allowing readers to view the images in high-resolution on screen. Written from the stance of the cardiac surgeon, this updated book is essential reading for consultants and trainees in cardiac surgery, cardiology and cardiovascular radiology, and anatomists.
Pacific Island Countries and Areas (PICs) represent some of the most remote and logistically challenging locations – with thousands of islands covering vast ocean territory. Since 2017, Pacific Ministries of Health have been developing EMTs, and all have worked to train team members to be deployment-ready.1
Objectives:
To describe an EMT training package specifically tailored to PIC contexts, including curated content, practical exercises, and “talanoa” discussions to improve EMT readiness, with a focus on logistics in remote and austere PIC contexts.
Method/Description:
WHO leveraged EMT training materials developed globally and regionally to continuously tailor an in-person EMT training package, emphasizing readiness for the deployment of light, mobile clinical teams for disaster-prone small island/large ocean countries. Emphasis was placed on practical learning exercises focusing on skills and competencies needed to manage complex Pacific deployments, and to care for populations on remote, difficult-to-reach islands with limited resources and referral options.
Results/Outcomes:
The Pacific EMT training program includes a mix of didactic and practical sessions coupled with a full-scale simulation exercise; it was designed with and for Pacific EMTs. The effectiveness of the training package has been evidenced through many successful national EMT deployments in several PICs, as well as through consistently positive participant feedback.
Conclusion:
Tailoring training materials to specific country contexts is essential. In the Pacific, core EMT training content with an emphasis on practical activities and simulations and “talanoa” discussions reflecting on previous deployments in remote islands has been viewed by participants as critical to preparing them for real-world deployments.
Pacific Island Countries and Areas (PICs) represent some of the most logistically challenging locations, covering vast ocean territory and remote islands. Light, mobile clinical response capability is critical in the disaster-prone Pacific. Beginning in January 2021, WHO researched, tailored, and procured EMT cache “kits” specifically for Pacific Island contexts, based on the core standards of the global EMT initiative.
Objectives:
To research, tailor, and procure cache “kits” to ensure self-sufficiency and high-quality out-patient mobile medical care for national EMTs in PICs.
Method/Description:
WHO facilitated the development of national cache kits for 10 PICs EMTs. A need for specialized equipment and supplies or “cache” for team self-reliance is critical. Through a consultative process, including Pacific EMT leadership and team members, EMT mentors, and regional partners, WHO curated and procured cache kits for 10 PICs EMTs.
Results/Outcomes:
The Pacific EMT cache kit is designed for four-to-six-person teams with the capacity to deploy for a minimum of three days, with full self-sufficiency. Because of the complex and remote access to many Pacific Islands, EMT cache must be practical for transport on small aircrafts and maritime vessels. A consultative process resulted in a curated cache list for Pacific national EMTs of over 125 items, estimated to weigh approximately 440 kilograms per kit. By the end of 2022, a total 31 kits will be delivered to EMTs in ten countries.
Conclusion:
The design, development, and procurement of Pacific EMT cache for national response operations will allow for increased speed and agility for response to disasters and public health emergencies.
Many Pacific governments have committed to establishing deployable, self-sufficient national EMTs following recent tropical cyclones, measles outbreaks, and the COVID-19 pandemic. However, for much of the COVD-19 pandemic, PICs have closed international borders limiting in-person team member training.
Objectives:
To develop a remote, interactive EMT training series to engage current and prospective EMT team members in the PICs during the COVID-19 pandemic.
Method/Description:
From July through September 2021, WHO hosted a weekly webinar series to introduce the concepts of the EMT Initiative to current and prospective EMT team members in the PICs. The sessions utilized Pacific deployment experience using faculty from EMTs in Australia, Fiji, New Zealand, Papua New Guinea, Solomon Islands, Tonga, and Vanuatu.
Results/Outcomes:
Attendees from over 23 countries from across the Pacific and other areas of the world participated in the 11 sessions, with a total of over 300 individual participants. The average number of participants per sessions was 85. Feedback was sought after every session. The most significant adaptation of the sessions from the feedback was incorporating the Pacific tradition of talanoa, or storytelling, into the sessions.
Conclusion:
Adapting the session plans to incorporate the talanoa style of communication in the Pacific created an environment of learning from colleagues throughout the Pacific and increased participant engagement in the virtual setting. The webinar series provided knowledge of EMT basics and increased engagement and excitement in the establishment and continued growth of EMTs in the Pacific.