Abstract
An ASD is a common congenital cardiac lesion, comprising 6–10% of such anomalies at birth, although diagnosis may not occur until adulthood. The lesion may present as an atrial arrhythmia, paradoxical embolic stroke or exercise limitation secondary to RV volume overload. ASDs may be single or multiple and are associated with additional cardiac lesions in 30% of cases.
Introduction
The utility of TOE in cardiac surgery extends beyond the assessment of ventricular and valvular function. A comprehensive study reveals much about the structural abnormalities of the heart and associated vessels. This chapter will cover some ancillary topics, including:
Congenital heart disease – ASDs
Cardiac masses – thrombus, tumours and vegetations
Pericardial disease – tamponade and constrictive pericarditis
Aortic disease – aortic dissection
Atrial Septal Defects
An ASD is a common congenital cardiac lesion, comprising 6–10% of such anomalies at birth, although diagnosis may not occur until adulthood. The lesion may present as an atrial arrhythmia, paradoxical embolic stroke or exercise limitation secondary to RV volume overload. ASDs may be single or multiple and are associated with additional cardiac lesions in 30% of cases.
A PFO is not, by the strictest definition, an ASD, as there is no deficiency of septal tissue. The prevalence of a PFO at autopsy is approximately 25%. The PFO is associated with atrial septal aneurysm and Chiari networks.
ASDs are anatomically classified into:
Secundum ASD – 80%
Primum ASD – 15%
Sinus venosus ASD – 4–5%
Coronary sinus ASD – <1%
Secundum ASDs occur in the fossa ovalis area of the interatrial septum (Figure 35.1A). Primum ASDs are best viewed in the mid-oesophageal 4-chamber view, with the defect occurring just above the crux of the heart (Figure 35.1B) and are often associated with atrioventricular (A-V) valve abnormalities. Sinus venosus ASDs are visualized in the mid-oesophageal bicaval view, occurring at the SVC–RA junction (superior sinus venosus ASD) or the IVC-RA junction (inferior SV ASD). They are typically associated with partial anomalous pulmonary venous drainage. Coronary sinus ASDs involve an unroofed coronary sinus and are usually associated with a persistent left-sided SVC.
Figure 35.1 Mid-oesophageal four-chamber view showing (A) secundum ASD and (B) primum ASD
Many secundum ASDs are amenable to percutaneous device closure and the goal of the echocardiographer is to determine the size, location and number of defects.
Cardiac Masses
Intracardiac masses are a common source of embolism and can be categorized into thrombi, tumours and vegetations.
Cardiac Thrombus
The pathogenic continuum begins with a low-flow state within a cardiac chamber, visible as spontaneous echo contrast or ‘smoke’. This eventually leads to the deposition of thrombus in areas of stasis. In AF, the left atrial appendage (LAA) is particularly vulnerable to clot formation. Due to its position adjacent to the oesophagus, the LA and LAA are well suited to interrogation by TOE. Prominent pectinate muscles in the LAA may create difficulty in the diagnosis of thrombus. The use of CFD and PWD can provide additional information: an absence of blood flow in the LAA on CFD and an ejection velocity below 40 cm s–1 on PWD are suggestive of thrombus.
Ventricular thrombus formation occurs in areas of stasis, typically in akinetic or aneurysmal regions following infarction. When evaluating a potential thrombus, diagnosis requires visualization of the lesion in orthogonal planes and the lesion must be differentiated from artefact, false tendons and prominent trabeculations. Right-sided thrombi are often attached to foreign material, such as central venous catheters or pacemaker leads.
Tumours
The vast majority of cardiac tumours are caused by secondary malignant disease, with spread to the heart via direct tumour extension and venous or lymphatic metastasis. Typical primary malignancies with secondary cardiac involvement include lung, oesophagus, breast, kidney and melanoma.
Of the primary cardiac neoplasms, approximately 90% are benign, of which most are myxomas. Other benign tumours include papillary fibroelastoma, lipoma and fibroma.
Most myxomas occur in the LA, arising from the fossa ovalis (Figure 35.2.). They are more common in females and 7% are associated with Carney complex. They may be an incidental finding; they can present with systemic embolization; or they can cause complications due to the mass effect, often causing functional MS due to MV orifice obstruction.
Figure 35.2 Mid-oesophageal four-chamber view showing a myxoma (arrow) filling most of the LA
Papillary fibroelastomas are the second most common benign cardiac tumour. They are typically seen adherent to valves, on the aortic side of the AV and the ventricular side of the MV. They are well-circumscribed, attached to the valve by a stalk and often highly mobile.
Approximately 95% of primary cardiac malignant tumours are sarcomas. They are more common in the right side of the heart. Sarcomas occurring in the PA (Figure 35.3) are typically poorly differentiated with an unfavourable prognosis.
Figure 35.3 Upper oesophageal view showing a sarcoma (arrow) occluding the right PA. Ao, ascending aorta
Vegetations
TOE has an important role in the assessment of infective endocarditis. Surgical intervention can be guided by intraoperative TOE findings: size, location and mobility of vegetations; extension of infection into surrounding structures; mechanism and severity of valvular defects; assessment of prosthetic valve function; and the haemodynamic consequences of the various lesions.
Vegetations typically colonize the low-pressure side of valves: the atrial side of the A-V valves (Figure 35.4.) and the ventricular side of the semilunar valves. Right-sided lesions are associated with IV drug use. The embolic risk is proportional to vegetation size and more common when occurring on the anterior leaflet of the MV.
