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Heart failure learning module 2: diagnosis
Released1 November 2017 Expires: 01 November 2019 Programme:
Echocardiography also gives an assessment of:
global systolic function – can be measured in various ways
stroke volume (LV outflow tract area x left ventricular outflow tract velocity time integral [VTI]),
cardiac output (stroke volume x heart rate)
ejection fraction (biplane Simpson’s method)
diastolic function (LV filling pressures)
restrictive filling pattern on transmitral spectral Doppler is associated with worse outcome
longitudinal systolic and diastolic function by tissue Doppler imaging
the ratio of the early mitral peak velocity to early diastolic mitral annular velocity is used to estimate LV filling pressure
can besecondary to ventricular dilatation in heart failure
tricuspid regurgitation (figure 10) also allows estimation of right ventricular systolic pressures (figure 11). In combination with IVC appearances, this can be used to estimate pulmonary artery systolic pressure.
Exercise or pharmacological stress echocardiography may be used to identify the presence and extent of inducible ischaemia and to determine whether non-contracting myocardium is viable.
Transoesophageal echocardiography (TOE)
TOE is usually not needed in routine diagnostic assessment unless the transthoracic ultrasound window is inadequate (e.g. because of obesity, chronic lung disease, ventilated patients) and an alternative modality (e.g. cardiac magnetic resonance [CMR] imaging] is not available or appropriate. In special cases, such as endocarditis, TOE can give more detailed information to guide diagnosis and management.
Cardiovascular magnetic resonance
Cardiac magnetic resonance (CMR) scanning is becoming more widely available and can provide a range of information on different aspects of cardiac function, as well as suggest the underlying cause of heart failure. CMR is recommended by the ESC as the best alternative imaging modality in patients with non-diagnostic echocardiographic studies as recommended in the European Society of Cardiology (ESC) heart failure guidelines. For a more detailed discussion with examples, please click below.
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In the last 10 years there has been an exponential growth in the use and availability of CMR in the UK, with the most common reason for referral being the assessment of heart failure and cardiomyopathy.15 ESC guidelines recommend CMR in patients with inconclusive echocardiographic imaging and suspected inflammatory or infiltrative conditions.5 European registry data suggest that CMR changes patient management in around two-thirds of cases and is diagnostic in up to 16%.16 A typical CMR study involves the following steps:
Anatomical thoraco-abdominal imaging
This can be done in any plane, but typically involves a transverse stack. Figure 12 shows a patient presenting with acute pulmonary oedema in the week before the CMR study. A white blood transverse stack is shown. There is a large abdominal aortic aneurysm with intramural thrombus. A number of renal cysts are seen. In the thorax, sternal wires are present and the left ventricle and atrium are dilated. The aorta follows a tortuous course.
Cardiac anatomy and ventricular volumes, function and mass assessment
Cine imaging can be taken in any tissue plane, typically the long axis and short axis views. Figure 13 shows the long and short axis cine images from the same patient. The left ventricle is dilated with an indexed end diastolic volume of 182 ml/m2 (normal: 60–95) and has an ejection fraction of 47%. Note the regional wall motion abnormalities and the small apical microaneurysm. The indexed LV mass is raised at 206 g/m2 (57–90). The views of the aortic valve in figure 14a show significant aortic regurgitation (AR). A short axis cut through the valve (figure 15) shows it to be functionally bicuspid with an early aneurysm of the right sinus of Valsalva. Flow imaging found a large regurgitation fraction (51%) through the valve, confirming severe AR.
Late gadolinium enhancement
Gadolinium is an extracellular contrast agent. Following intravenous administration, it will accumulate in areas of the myocardium where there is expansion of the extracellular space. Expansion can occur as a result of fibrosis, infarction, oedema and infiltration. Areas of focal expansion can then be shown using CMR sequences which are particularly affected by the presence of gadolinium. These areas of abnormality appear white and are known as late gadolinium enhancement (LGE). The pattern of LGE can suggest the cause for heart failure and give prognostic information.
CMR in the dilated LV: differential diagnosis
In patients with global LV dysfunction, LGE-CMR accurately differentiates ischaemic from non-ischaemic cardiomyopathy and hence can be used as a ‘gatekeeper’ for coronary angiography.17 Areas of infarction will involve the sub-endocardium, a pattern very rarely seen in non-ischaemic cardiomyopathy. In figures 16 and 17, patients with global LV impairment are shown. Figure 16a shows that the patient has transmural LGE in the septum and anterior walls, and was found to have three-vessel disease on angiography. Figure 16b shows the patient has mid-wall and epicardial LGE. He had a family history of dilated cardiomyopathy and was found to have a desmosomal mutation.
CMR can also identify other causes of a dilated LV. Figure 17a shows a coronal image from a patient presenting with severe heart failure, and figure 17b shows his severe biventricular dilatation and dysfunction. Bilateral large pleural effusions are seen and the liver appears more “black” than usual. This is seen in patients with iron overload. A specific sequence, T2*, was therefore performed which allows myocardial and liver iron quantification. There was severe iron overload in both organs. Following genotyping, a diagnosis of haemochromatosis was made and cardiac function recovered after iron chelation therapy (figure 17c).
The cine imaging of a patient presenting with a two month history of increasing breathlessness is shown in figure 18a. There is severe biventricular failure. The LGE imaging is shown in figure 18b. There is a large amount of LGE which does not correspond with coronary artery territories, although it is transmural in places. In figure 18c, areas of lymphadenopathy are arrowed. A diagnosis of sarcoidosis was subsequently confirmed on lymph node biopsy.
Myocardial viability and coronary revascularisation
For over two decades, cardiologists worldwide have used the results of non-invasive imaging tests to help determine the need for revascularisation in patients with ischaemic LV dysfunction. This dogma was challenged by the results of the STICH (Surgical Treatment for Ischemic Heart Failure) trial which suggested that there was no role for revascularisation in patients without angina.18 However, the STICH extension study suggests that there may be a small benefit from revascularisation in carefully selected patients,19 and so imaging is still used to assess viability. Techniques used include: