Cardiology Intensive Board Review, 3 ed.

Cardiac Imaging

Ellen Mayer Sabik • Brian P. Griffin

ANSWERS

1.d. Abnormal mechanical MVR. Figure 14.1 is a 3D echo image showing a malfunctioning bileaflet mechanical MVR. This image demonstrates one leaflet that is open (to the right of the image), while the other remains shut. You can see the sewing ring of the prosthesis well. This is most likely due to thrombus although impingement by a chord or piece of valve could do this as well.

2.b. Percutaneous mitral valvuloplasty (PMV) because he has a split score of 4 to 8 and minimal MR. The MV “split score” as it pertains to “ splittability” of a rheumatic MV with MS is derived by grading four features of the stenotic valve. The features, which are graded on a scale of 1 to 4, include leaflet thickening, leaflet calcification, leaflet mobility, and involvement of the subvalvular apparatus. Grade 1 denotes the least abnormality while 4 denotes the most severe abnormality. Because each feature is graded on a scale of 1 to 4, the total score can range from 4 (more splittable) to 16 (least splittable). A valve with a score of ≤8 is considered amenable to PMV as long as there is no significant MR. Of note, the degree of MR typically increases by 1 grade when a patient undergoes balloon mitral valvuloplasty. A score of >8 denotes a valve that would not be amenable to PMV and if the patient is symptomatic or has significant pulmonary hypertension or other indication for an intervention (other than maximizing medical therapy), the patient would undergo a surgical valve replacement as long as they were considered a surgical candidate. The images presented for this example show a patient with severe MS due to rheumatic disease with minimal leaflet thickening or calcification, and no subvalvular involvement with preserved mobility. The stenosis is due almost entirely to commissural fusion and as such has a split score of 4. In addition, the color Doppler still frame in systole showed only trivial MR. For these reasons, the patient is an ideal candidate for PMV. The images in Figure 14.23A and B were taken following the balloon inflations during the PMV.

Figure 14.23 • A. Three-dimensional images of the mitral valve showing a larger orifice and the split commissures compared with the pre-PMV image. B. The transmitral gradient post balloon inflation. The mean mitral gradient has decreased from 30 to 9 mmHg.

3.c. Right atrial (RA) thrombus or thrombus on central venous catheter. The patient discussed in this question has a malignancy and is likely in a hypercoagulable state. The mass noted within the RA appears to be broad based and may be in association with her central venous catheter. In this situation, this is most likely to be an RA thrombus. The prosthetic appearing structure within the RA appears to be the central venous catheter and does not go through the tricuspid valve (TV) into the RV, and therefore is not an ICD. An RA myxoma typically has a thin stalk and is most often associated with the interatrial septum. It can be seen within the RA or left atrium (LA). Figure 14.24A and B demonstrates a classic myxoma, one showing surgical pathology and the other showing an echo image of a myxoma. A Chiari network is a more fenestrated mobile structure seen at the junction of the vena cava and RA.

Figure 14.24

4.a. Moderate risk of endocarditis. The images in Figure 14.4 demonstrate a PDA. This is seen as the color flow into the pulmonary artery (PA). In this example, the PDA is large and its orifice can be seen in the two-dimensional (2D) images opening into the PA. The complications that can be associated with a PDA include the development of CHF and a moderate risk of endocarditis (although antibiotic prophylaxis is not recommended unless the unrepaired PDA is complicated by pulmonary hypertension/Eisenmenger syndrome causing cyanosis). The clinical manifestations of the PDA depend on the size of the left-to-right shunt. The larger the shunt, the worse the clinical manifestations. The murmur associated with a PDA is a continuous murmur (since the left-sided pressures are higher than the right side throughout the cardiac cycle), not a systolic murmur.

5.d. Aortic insufficiency (AI). Although all of the answers are possible complications of infective endocarditis, the images displayed in Figure 14.5 do not show any significant AI. Figure 14.5A shows the short axis of a bioprosthetic AV with a paravalvular abscess with vegetations. It also shows the valve during systole which although it is open, the opening is restricted suggestive of AS which is confirmed by the peak AV gradient of 92.6 mmHg shown in Figure 14.5BFigure 14.5C shows the long-axis TEE view of the AV with a small fistula into the LA (seen at the top of the image).

6.d. Pulmonary embolus. The images in Figure 14.6 show the parasternal short axis showing specifically the main PA/PA bifurcation. Both images show a large multilobulated echodensity or mass within the main PA which represents a clot in transit. The patient is hypercoagulable due to her malignancy and has developed a deep venous thrombosis which has embolized and is on its way to the lungs. The multilobular appearance shows that this mass is a cast from a deep vein in the leg. The remaining answers are causes of CP; however, these answers do not describe the situation found on TTE. Patients with malignancy can present with tamponade from a pericardial effusion but no effusion is seen on these images.

7.e. Emergent cardiac surgery. The images demonstrate a patient with cardiac tamponade. Findings include significant respiratory variation of MV inflows (>25%) and RV diastolic collapse, RA inversion, and inferior vena cava plethora (dilated >2 cm and does not collapse normally with inspiration). A patient with a type I dissection and cardiac tamponade needs to go to emergent cardiac surgery as soon as possible for drainage of the pericardium and repair of the aorta. Pericardiocentesis could potentially cause complete rupture of the flap into the pericardium, causing cardiac arrest and death. An aortic stent graft is currently not the treatment of choice for a type I dissection and could certainly not address the problem of tamponade. Coronary angiography in this patient would only delay the definitive therapy (surgery) as well as possibly further propagate the dissection flap. Recall that delay of surgery in a patient with a type I dissection is associated with a 1% per hour increase in mortality in the first 48 hours of the process. (Note that this patient has not had prior cardiac surgery—if the person had prior cardiac surgery, that would likely change the need for cardiac catheterization prior to surgery, although in this patient emergent surgical drainage of the pericardium would be needed.)

8.b. Cleft MV. The image displays an apical four-chamber view of a patient with a primum ASD. (Note Fig. 14.8B with color Doppler shows left-to-right shunting through the ASD.) This is part of either a partial or complete AV canal defect. A complete AV canal defect includes a primum ASD, a cleft anterior mitral leaflet, and a widened anteroseptal tricuspid commissure. A partial AV canal defect is as above but without the VSD. Note that because of the long-term, significant right-to-left shunt through the ASD in this patient the right side is dilated and there is right ventricular hypertrophy from pulmonary hypertension. The short-axis view of the MV (Fig. 14.25A) demonstrates the cleft anterior mitral leaflet, which “splits” in the center, as opposed to opening like a fish mouth as is seen with normal MVs. Figure 14.25B is a drawing showing normal short axis of MV versus cleft MV.

9.d. Coarctation of the aorta with bicuspid AV with AI. The patient is a young man with hypertension beginning in his late 20s or early 30s. Secondary hypertension must be considered and ruled out in this patient. When he was initially diagnosed he should have had his blood pressure checked in both arms and legs in consideration of a coarctation of the aorta. Note: Someone may also notice rib notching on a chest X-ray. Other etiologies that should have been excluded include renal artery stenosis (more commonly seen in women if caused by fibromuscular dysplasia), pheochromocytoma, Cushing syndrome, or primary aldosteronism. This patient’s heart murmur was a diastolic murmur from AI caused by prolapse of a bicuspid AV. At least 50% of patients with a coarctation have a bicuspid AV. Fewer patients with bicuspid AV have a coarctation. Note that bicuspid AVs dome (doming aortic leaflets are seen in Fig. 14.9D) and could be mistaken on initial glance in long axis with a rheumatic AV. However, in addition to doming there is prolapse of the conjoined cusp (which would not be seen in a rheumatic valve) and the anatomic situation could be clarified with a good short-axis view.

Figure 14.25 • A. Parasternal short-axis view of the mitral valve (TTE). B. Drawing comparing the parasternal short-axis view of a normal mitral valve to the opening of a cleft anterior mitral leaflet.

10.e. Intravenous (IV) drug abuser. Right-sided endocarditis is less common than left-sided endocarditis. The TEE image (Fig. 14.26) shown demonstrates a patient with a vegetation on the tricuspid valve, and the organism identified by culture is Pseudomonas. This is associated with IV drug use with contamination at the time of injection. Although the other clinical situations listed are at increased risk for endocarditis (typically left sided), Pseudomonas would be a very unusual pathogen in those situations.

Figure 14.26

Figure 14.27 • A. M-mode through the mitral valve. B. M-mode through the mitral valve. C. M-mode through the mitral valve. D. M-mode through the mitral valve. E. M-mode through the aortic valve. F. M-mode through the aortic valve.

11.b. MVP. The M-mode trace is performed through the MV in a patient with myxomatous MV disease with bileaflet prolapse. Note the marked dip backward of the MV leaflets after the closure point (see Fig. 14.11). Note that there is full systolic range of motion creating the “M” trace of the anterior mitral leaflet and the normal “W” trace of the posterior leaflet. This is in contrast with a normal MV M-mode, which would not have the systolic dip (Fig. 14.27A). Thus, there is no rheumatic MS, which would look like Figure 14.27B in which there are still pliable but tethered leaflets causing a loss of the normal “M” and “W” appearance of the mitral leaflets. More advanced MS with thickened and calcified leaflets would have thicker and brighter appearance of the leaflets together with more restriction of the leaflet motion (Fig. 14.27C). M-mode for a patient with HOCM and SAM would appear like the images in Figure 14.27D and E. Note the SAM of the mitral leaflets in Figure 14.27D and the early closure of the AV in Figure 14.27E (compared with the M-mode of a normal AV [Fig. 14.27F]).

Figure 14.28 • A. Mid-esophageal short-axis view of the aortic valve (diastole). B. Mid-esophageal short-axis view of a bicuspid aortic valve with fusion of the RCC and NCC. C. Mid-esophageal short-axis view of a unicuspid aortic valve. D. Mid-esophageal short-axis view of a quadricuspid aortic valve.

12.c. Bicuspid AV with fusion of the RCC and LCC. The 2D TEE mid-esophageal view (see Fig. 14.12) demonstrates a bicuspid AV in short axis. To determine cusp anatomy one must view the AV in systole. If one looks for a “Mercedes Benz” image of the valve in short axis during diastole (Fig. 14.28A), one may mistake a bicuspid valve for a tricuspid valve, not realizing that one of the arms in the Mercedes Benz sign is actually a calcified raphe between two fixed cusps. Thus, it is important to look at the valve in systole to determine the true cusp anatomy. The most common form of bicuspid AV is fusion of the RCC and LCC. Bicuspid AVs are also associated with a dilated aorta with an aortopathy involving cystic medial necrosis. Another form of bicuspid AV is fusion of the RCC and NCC (Fig. 14.28B). There are other congenitally abnormal AVs, including unicuspid valves (Fig. 14.28C) and quadricuspid valves (Fig. 14.28D). The unicuspid and quadricuspid valves are much less common than bicuspid valves.

13.b. Supracristal VSD. This image demonstrates a supracristal VSD. The VSD is located just under the pulmonic valve, best seen in the parasternal short-axis view (seen at 1 o’clock). A membranous VSD would be seen at 10 or 11 o’clock in short-axis view (Fig. 14.29A). Ebstein anomaly involves apical displacement of the tricuspid valve with atrialization of some of the RV (Fig. 14.29B). Patent ductus can also be seen in the parasternal short-axis view seen best by color Doppler showing a flow entering the PA (from the aorta) (Fig. 14.29C). PS is seen on 2D in the parasternal short-axis view with doming pulmonic valve leaflets with color acceleration across the valve. In diastole there may also be some PI as the leaflets may have restricted closing.

14.b. Rheumatic MV disease with MS and MR. The images shown demonstrate a doming anterior mitral leaflet and a fixed posterior leaflet. There is color acceleration across the MV, suggestive of MS, which is supported by the high gradients found by continuous-wave Doppler through the MV. There is also significant MR (posteriorly directed) seen in the systolic frame with color Doppler. The mechanism of MR in this case is restricted leaflet motion. Myxomatous MV disease (Fig. 14.30), in contrast, is characterized by markedly redundant, prolapsing leaflets, which prolapse back into the LA, occasionally with a torn chord causing a flail leaflet. Typically, the jet of MR is very eccentric if only one leaflet is involved (the jet is in the opposite direction from the most involved leaflet). If there is balanced bileaflet prolapse, the jet is usually centrally directed.

Figure 14.29 • A. Parasternal short-axis view (both 2D and with color Doppler). B. Apical four-chamber view (pediatric display with atria at the top of the screen). C. Parasternal short-axis view.

Figure 14.30 • Parasternal long-axis view of a patient with mitral valve prolapse.

15.c. Patient with severe tricuspid regurgitation (TR). The parasternal short-axis still frame in diastole demonstrates a patient with diastolic septal flattening. This is found in a patient with right-sided volumeoverload. You can also see patients with systolic septal flattening, which is consistent with right-sided pressure overload. The patient with severe TR has right-sided volume overload and would have diastolic septal flattening as shown. Patients often have both diastolic and systolic septal flattening if they have both volume and pressure overload on the right side, for example, in a patient with chronic pulmonary embolisms who has developed pulmonary hypertension and also developed significant TR. The lesions of MR and AI are volume loads for the LV, and the subaortic membrane is a pressure load on the LV.

16.b. Septal myectomy. The TEE images demonstrate a patient with HOCM. There is septal hypertrophy and the systolic frame demonstrates SAM, which is SAM of the mitral leaflets (Fig. 14.31). The color Doppler images for this patient demonstrate severe MR that is posteriorly directed, which is classic for MR caused by SAM of the mitral leaflets. SAM can involve either the anterior or posterior leaflet alone, or a patient may have bileaflet SAM. Typically, if the mitral leaflet has not been too damaged by years of contact with the septum, performing a septal myectomy can fix the severe MR by eliminating the left ventricular outflow tract (LVOT) obstruction and eliminating the SAM. This type of MR is often hemodynamically labile depending on the loading conditions of the LV. The SAM can be brought out or accentuated by giving the patient amyl nitrite or isuprel. The SAM is decreased by volume loading the ventricle or increasing the systemic pressure. If the mitral leaflets, however, have been scarred by years of contact with the septum, a simultaneous MV repair or replacement may need to be performed. If the MV has to be replaced, often the surgeon has to use a lower-profile valve (typically a bileaflet mechanical valve) because of the narrowed LVOT. Neither a CABG nor an ascending aortic conduit would help this patient unless he had concomitant CAD or an ascending aortic aneurysm, in which case these procedures would have to be performed in addition to the myectomy.

Figure 14.31

17.d. Thrombus. This patient had a very large anterior MI and has significant thinning and akinesis of the anterior wall and LV apex. Because of this significant wall motion abnormality, there is stasis of the blood and the patient is at risk for forming a thrombus, which this patient has done. The homogeneous nature of the mass with an echogenicity similar to that of the myocardium (or slightly less echogenic than the myocardium) suggests that the thrombus is relatively fresh. As this heals or organizes over time, calcium may be deposited, and old, organized thrombi in the heart are often quite echogenic. A sarcoma, on the other hand, would be an invasive mass and would not respect the boundaries of the myocardium, but rather would infiltrate the myocardium. Teratomas if found in the heart arise from the pericardium, not within the LV cavity. These are typically benign although may compress the heart. A teratoma would also have a more heterogeneous appearance on echo. Myxomas are the most common benign tumor of the heart and 80% of those are located in the LA, and most of the remaining ones are found in the RA. Papillary fibroelastomas are the second most common benign cardiac tumors and are typically pedunculated (with a stalk) and mobile. Most (>80%) are located on heart valves.

18.c. Hibernating myocardium in the LAD territory. There is a matched defect in the LAD territory seen on the resting and post-stress images involving the apex and four periapical segments as well as the mid-anterior and anteroapical segments. This is consistent with a large LAD territory infarct without any inducible ischemia. The metabolic FDG images show a perfusion/metabolism mismatch with FDG uptake seen in the previously mentioned LAD segments, suggesting a large region of hibernation in the LAD territory without any significant scar. (Note that there is significant gastrointestinal [GI] uptake near the inferior wall.) The degree of hibernation involved 40% of the myocardium (6% for each involved segment except for the apex, which represents 4% of the myocardium). A study by Hachamovitch et al.1 in 2003 showed that revascularization was superior to medical therapy if the amount of myocardium at risk (ischemic and hibernating) exceeded 20%. Since the above patient demonstrated a large area of hibernating myocardium in the LAD territory, the patient would benefit from revascularization of the LAD territory as well as the diagonals. This patient underwent surgical revascularization of all three vessels.

19.b. Multivessel ischemia. The resting scan showed GI activity, but overall normal tracer uptake. There was increased septal uptake caused by the moderately severe LVH. Post stress there is severely reduced tracer uptake involving the mid- and apical anterior, entire anteroseptal, and inferolateral walls and inferior wall and apex. There was also cavity dilation post stress. This is known as transient ischemic dilation (TID). The gated images that accompanied this study demonstrated hypokinesis of the above segments. Note that the post-stress gated images are acquired post stress, but at rest. That is to say that there is a delay between stress and imaging, which may allow for some recovery of function. This scan is of high risk in that there is ischemia in all three vascular territories with TID and extensive wall motion abnormalities. Although the patient was asymptomatic under his baseline conditions, it was appropriate to order the adenosine nuclear stress test since the patient is diabetic with prior revascularization and with a questionable functional status who was going to undergo a high-risk surgical procedure (aortic aneurysm repair).

20.d. Scar and ischemia in the LCx/RCA territory. The full interpretation of the study was that there was marked GI activity in the rest images, but there was also a severe resting perfusion defect involving the basal and mid-inferolateral segments. Although GI activity can make the basal and mid-inferior segments difficult to interpret at rest, the post-stress images clearly show that the defect now involves the entire inferolateral and inferior walls, showing infarct with peri-infarct ischemia in the LCx/RCA territory. Cardiac catheterization demonstrated a total obstruction of the proximal LCx (a dominant LCx) with collaterals from the RCA and LAD. There were no obstructions in the RCA and LAD. Important points from this case include that diabetics are at high risk for CAD and clinical parameters do not predict ischemia (from the detection of ischemia in asymptomatic diabetes (DIAD) trial). Myocardial perfusion imaging can be performed safely post MI to assess infarct size and the amount of myocardium at risk. It is also a good test to assess the adequacy of collateral blood flow.

21.e. LAD and LCx versus left main ischemia. The resting images demonstrate normal perfusion. Post stress, however, there are significant perfusion defects in the anterior, anterolateral, and inferolateral walls. There is also cavity dilatation, which is consistent with either left main disease or multivessel ischemia. The gated images showed new wall motion abnormalities in the LAD and LCx territories. The presence of stress-induced perfusion defects in multiple vascular territories as well as TID and new wall motion abnormalities on the gated images are all findings associated with high-risk scans. The cardiac catheterization in this patient demonstrated 70% stenosis in the proximal LAD, while the stent in the mid-LAD was patent. There was a large obtuse marginal with a 90% proximal stenosis. There was mild disease in the proximal RCA, and the stents in posterior descending artery and posteroventricular branch were patent.

22.d. Patients with this condition who survive past childhood often present with varying degrees of heart failure, myocardial ischemia, and MR, depending on the development of collateral circulation. This CT demonstrates an anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). Also known as Bland-White-Garland syndrome, ALCAPA is a rare but serious congenital anomaly. It is caused by either (a) abnormal septation of the conotruncus into the aorta and PA or (b) persistence of the pulmonary buds together with involution of the aortic buds that eventually form the coronary arteries. Occurrence is similar between men and women and is not considered an inheritable congenital cardiac defect. Because of the low pulmonary vascular resistance, left coronary artery flow reverses and enters the pulmonic trunk (coronary steal phenomena). As a result, the LV myocardium remains underperfused, leading to infarction of the anterolateral LV wall. This often causes anterolateral papillary muscle dysfunction and variable degrees of mitral insufficiency. Consequently, the combination of LV dysfunction and significant MV insufficiency leads to CHF symptoms (e.g., tachypnea, poor feeding, irritability, and diaphoresis) in the young infant. Collateral circulation between the right and left coronary systems eventually develops. Approximately 85% of patients present with clinical symptoms of CHF within the first 1 to 2 months of life. Left untreated, the mortality rate in the first year of life is 90% secondary to myocardial ischemia or infarction and MV insufficiency leading to CHF. In unusual cases, the clinical presentation with symptoms of myocardial ischemia may be delayed into early childhood. Rarely, a patient may stabilize following infarction and may present with MV regurgitation, periodic dyspnea, angina pectoris, syncope, or sudden death later in childhood or even adulthood, as in this patient. Treatment consists of surgical ligation of the anomalous coronary artery origin and bypass grafting to the left coronary artery. Reimplantation onto the native aortic root is typically not possible because of the friable quality of the anomalous left coronary artery ostium.

REFERENCE

1.Hachamovitch R, Hayes SW, Friedman JD, et al. Comparison of the short-term survival benefit associated with revascularization compared with medical therapy in patients with no prior coronary artery disease undergoing stress myocardial perfusion single photon emission computed tomography. Circulation. 2003;107(23):2900–2907.