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The Big Heart Disease Lie

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Fig. 1. A 75-yr-old female with cardiovascular risk factors and acute neurological deficits. High parasternal long-axis view showing calcified atherosclerotic plaque.

Fig. 1. A 75-yr-old female with cardiovascular risk factors and acute neurological deficits. High parasternal long-axis view showing calcified atherosclerotic plaque.

Atrial Appendage Thrombus
Fig. 2. Midesophageal zoomed image of the left atrial appendage (LAA) at omni 90° showing well-defined thrombus in a patient with atrial fibrillation.

should be distinguished from lacunar or hemorrhagic strokes, which are secondary to intrinsic cerebrovascular disease and/or hypertension. In elderly patients (>55 yr old), atherosclerosis of the great arteries and internal carotid arteries are thought to account for 20-60% of embolic strokes. These patients often have coexisting cardioaortic disease and internal carotid artery disease, rendering it difficult to identify which vessel is the culprit source of embolus in many cases. Atrial fibrillation with associated thrombus forming in the left atrial appendage (Fig. 2) is also one of the most frequent causes of embolic stroke. Younger patients (<55 yrs old) with embolic strokes are less likely to have significant atheromatous disease, and more likely to have cardiogenic sources of

Table 1

Potential Cardiovascular Etiologies of Stroke

A. From great arteries

Internal carotid artery atheroma Aortic root and ascending aortic atheroma Arterial dissection Vasculitis

B. Cardioembolic

Atrial fibrillation, rheumatic heart disease ^ atrial thrombus Left ventricular dysfunction ^ ventricular thrombus Mitral stenosis, prolapse, mitral annular calcification Endocarditis ^ valvular vegetations; marantic endocarditis Tumors: myxoma, papillary fibroelastoma, fibrin strands

Mitral valve and aortic valve prostheses, particularly mechanical ^ thromboemboli Intracardiac shunts:

Patent foramen ovale and/or atrial septal aneurysm Atrial septal defect Ventricular septal defect Hematologic hypercoagulable state: activated protein C resistance/Factor V Leiden mutation, anticardiolipin antibody, Lupus anticoagulant, prothrombin mutation embolus or hypercoagulable states. Approximately 40% of strokes are of undetermined origin ("cryptogenic"), of which up to half have been associated with various cardiac abnormalities, which are detectable by echocardiography.

Other systemic emboli—those targeting the eye, kidney, spleen, or skin—are usually the result of vegetation or thrombus shed from an abnormal or prosthetic cardiac valve, or the result of atheromatous debris dislodged by intra-arterial catheter procedures.

A pulmonary embolus is the result of a deep venous thrombosis, which has broken free and traveled to the lung bed. Risk factors for venous stasis, the diagnosis, treatment, and echocardiography findings of pulmonary embolism are discussed in Chapter 18.

Etiology

Potential cardiovascular etiologies of stroke are listed in Table 1. Transthoracic echocardiography (TTE) can detect the majority of the potential cardioembolic causes of systemic emboli. The prevalence of cardiac abnormalities predisposing to emboli differ according to the age of the patient.

In older patients, significant findings may include the following: atheroma may be seen as irregular thickening of the aortic wall in the aortic root, ascending aorta, arch, and descending abdominal aorta. Calcified plaques tend to appear very jagged and echobright, and associated thrombus can appear as tethered but mobile elements. Plaques that are more than 4 mm in thickness, or which contain mobile or protruding elements, are associated with a higher risk of stroke. Atheroma are better visualized on transesophageal echocardiography (TEE) (Fig. 3A,C; please see companion DVD for corresponding video). When coronary artery bypass surgery is contemplated in patients with significant aortic root disease, TEE or epiaortic scanning routinely assists in guiding bypass pump cannula placement, to decrease the risk of causing a stroke by dislodging plaque in the punctured area. The presence of atrial fibrillation, particularly in the presence of rheumatic heart disease, increases the risk of atrial thrombus formation. Atrial thrombi often occur in association with spontaneous echo contrast, which is thought to represent increased fibrin and red blood cells in the early stages of coagulation. Although TTE often does not fully visualize the left atrial appendage, thrombi may occasionally be seen in the body of the left or right atrium. Figure 4 is a parasternal short-axis view of a thrombus within the left atrial appendage (see Chapter 16). The presence of a dyskinetic or aneurysmal area of left ventricle in a patient with a history of myocardial infarction should always prompt evaluation for an associated intramural thrombus (see Chapter 7), which can vary greatly in shape and mobility.

Right Atrial Appendage Thrombus
Fig. 3. (See legend, facing page)

Mitral stenosis, stranding, and mitral annular calcification have all been suggested to be associated with risk of embolus, although there are often confounding risk factors. Mitral valve prolapse was historically implicated as a risk factor, but this appears to be an artifact of overdiagnosis of mitral valve prolapse in this population, rather than comprising a true etiological substrate. Bacterial vegetations (Fig. 5; please see companion DVD for corresponding video) are more likely to occur on abnormal native valves, such as bicuspid aortic or myxomatous mitral valves. Prosthetic valve thrombus or vegetation may be detected as independently mobile echodensities, predominantly located on the low-pressure side of the valve. On mechanical prosthetic valves, the masses may not be clearly visualized because of acoustic shadowing by the prosthesis, but if one or more discs appear immobile or an unusually high transvalvular gradient is detected by Doppler, suspicion for obstruction remains high and a TEE should be performed. Marantic endocarditis is a disease associated with cancer, inflammatory, and hypercoagulable states, and is caused by continuous formation of fibrin and thrombus on the valves, which then break off into the bloodstream. Other findings commonly found in elderly

Fig. 3. (A) Transesophageal short-axis view of the descending thoraci aorta showing large calcified atheromatous plaque. (B) Transesophageal long-axis view of the desecending thoraci aorta (same patient in A) showing the longitudinal extent of the large calcified atheroma. (C) Serial short-axis transesohageal echocardiographic images of the aorta showing mobile element of atheromatous plaque. (Please see companion DVD for corresponding video.)

Mobile Aortic Plaque

Fig. 3. (A) Transesophageal short-axis view of the descending thoraci aorta showing large calcified atheromatous plaque. (B) Transesophageal long-axis view of the desecending thoraci aorta (same patient in A) showing the longitudinal extent of the large calcified atheroma. (C) Serial short-axis transesohageal echocardiographic images of the aorta showing mobile element of atheromatous plaque. (Please see companion DVD for corresponding video.)

patients that may increase the risk of stroke include aortic sclerosis (irregular tissue thickening of the aortic valve leaflet edges), Lambl's excrescences (fibrin-containing strands found on the leaflet edges and occasionally in the left ventricle outflow tract), and papillary fibroelastomas (see Chapter 19). More rarely, echocardiography can discern aortic dissections with the intimal flap extending cranially to occlude a carotid artery. Subcostal views of the inferior vena cava infrequently detect previously unsuspected deep venous thrombi.

obtained. Although the interatrial septum looked normal, and no shunting was detected by color Doppler, an injection of intravenous agitated saline ("bubble study") showed right-to-left inter-atrial shunting within five cardiac cycles. This is indicative of a patent foramen ovale (PFO) (Fig. 6; please see companion DVD for corresponding video). Note that the patient was asked to "sniff," a quick inhalation that transiently increases right atrial pressure to increase sensitivity for right-to-left shunting.

Epidemiology of Cardiac Source of Embolus in Younger Patients

The epidemiology of cardiogenic emboli in younger patients is different from that of older subjects. Those with abnormal native valves, such as myxomatous or prolapsed mitral valve or bicuspid aortic valves are susceptible to endocarditis and resultant vegetation, which can embolize. Vegetations, which are more than 10 mm are at the highest risk for causing embolic complications. Among intracardiac tumors, myxomas are also more often found in younger patients owing to embolization (see Chapter 19).

CASE VIGNETTE 2, YOUNGER PATIENT

A 25-yr old active male presented with a "grayed-out" section of his left upper visual field 1 d after returning home from a long intercontinental flight. He had no prior medical history, and recalled no recent headache, fevers, chest pain, shortness of breath, palpitations, weakness or pain in his extremities, or other neurological problems. A head magnetic resonance imaging (MRI) showed a subacute right occipital infarct, without evidence of acute bleeding. He was treated with intravenous heparin, and a TTE was

Left Atrial Appendage Thrombus
Fig. 4. Parasternal short-axis view showing clot in left atrial (LA) appendage.

Paradoxical embolus is a well-known risk of congenital heart disease with intracardiac shunting, as in the case of atrial septal defects or ventricular septal defects. The presence of a dilated right atrium and/or right ventricle in the absence of other causes should prompt a diligent search for intracardiac shunting by both two-dimensional imaging and Color Doppler (Fig. 7; please see companion DVD for corresponding video).

PFO is a condition in which the ostium primum arises from the left atrial side and spans the fossa ovalis, but does not fuse completely with the apposing ostium secundum. PFO is essentially a normal variant, occurring in 25-30% of the population. Under conditions in which right atrial pressure exceeds left atrial pressure, the PFO can allow right-to-left intracardiac flow to occur (similar to a trap door or flap). The potential channel of the PFO is typically not visible on two-dimensional echocardiography, although increased mobility of the septum in the fossa ovalis area can be a clue to the presence of one. A careful color Doppler scan of a sector zoomed in on the interatrial septum, particularly in the subcostal window, can occasionally detect flow across the PFO as a narrow red jet of transient left-to-right flow (Fig. 8). Flow is typically greatest in late systole and early diastole.

Care should be taken to avoid false positives caused by eccentric tricuspid regurgitant jets or swirling caval flow. A "bubble study," or injection of intravenous saline that has been agitated with air to produce echo contrast, is an echocardiography method used to detect PFO. Because the bubbles produced by agitation within a syringe are relatively large and usually filtered by the pulmonary bed, the appearance of echogenic bubbles in the left side of the heart immediately (within six beats of opacifying the te*

Fig. 5. Parasternal long-axis views (PLAX) showing verrucous bacterial vegetation affecting the aortic valve—especially the noncoronary cusp. (Please see companion DVD for corresponding video.)

Fig. 6. Agitated saline contrast (bubble study) showing adequate right heart opacification in this apical four-chamber view. Note the right-to-left shunt (bubbles in the left heart chambers) via a patent foramen ovale (arrow). The Valsalva maneuver (sniff test) transiently increase right-sided pressures—thereby increasing the sensitivity of the "bubble study." (Please see companion DVD for corresponding video.)

right atrium) is indicative of right-to-left shunting (Fig. 6; please see companion DVD for corresponding video). Because left atrial pressure is usually higher than right atrial pressure, manuevers, which transiently increase right atrial pressure such as the Valsalva maneuver, coughing or sniffing, abdominal compression, or raising the legs can increase the sensitivity of a bubble study for detecting PFO. PFOs can allow paradoxical emboli from

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Responses

  • Lily Reid
    Is it possible to see the left atrial appendage in short axis view on echo?
    8 months ago

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