Left ventricular apical diseases

Myocardial thinning (one of the principal signs of myocardial injury) is an important observation in patients suspected of having had ischaemic insults to the heart. However, thinning of the LV apex has been described by anatomists as a normal feature. With the advent of motion-gated cross-sectional cardiac imaging, normal apical thinning can be quite noticeable, especially on computed tomography (CT) in which the spatial resolution is submillimetre [12, 13].

Magnetic resonance imaging has increasing potential in the non-invasive evaluation of patients with myocardial infarction and subsequent complications. The low interobserver variability and the high interstudy reproducibility of MR imaging for quantifying LV volume, wall thickening and mass make it an attractive imaging technique for follow-up studies in patients with ischaemic coronary artery disease and LV remodelling after infarction [14–16] . Moreover, MR imaging can clearly localise the site of the aneurysm, pseudoaneurysm or diverticula, is capable of distinguishing among pericardium, thrombus and myocardium, and delayed enhancement MR imaging helps in the differentiation between a true aneurysm and a pseudoaneurysm [17].

Pseudoaneurysms or false aneurysms are defined as a rupture of the myocardium that is contained by pericardial adhesions. A pseudoaneurysm usually represents a rare complication of myocardial infarction (Fig. 1, Video 1 and 2), but it may also occur after cardiac surgery, chest trauma and endocarditis [18]. They can occur in different locations, but the purpose of this paper is to describe those arising from the apex of the LV. The wall of a false aneurysm is composed of organised haematoma and pericardium (Table 1). Pathological examination shows fibrous tissue and lacks the myocardial elements that are usually seen in the wall of true aneurysms [18].

	Aneurysms	Pseudoaneurysms	Congenital diverticula
Layers	All layers of the ventricular myocardium	Organized hematoma and pericardium	All layers of the ventricular myocardium
Cine	Akinetic dyskinetic segment	Akinetic or dyskinetic segment	Shows contraction during systole
Myocardial late enhancement	Yes	No, only the border of the pseudoaneurysm will show enhancement	No
Pericardial late enhancement	No or faint	Marked	No

Conversely, a true aneurysm, which occurs in 5–10% of patients with acute myocardial infarction, contains the endocardium, epicardium and a predominantly fibrous tissue that has replaced myocardium in its wall [17]. An important difference is the lower rupture potential of a true aneurysm compared with a pseudoaneurysm. Surgical repair is the treatment of choice for pseudoaneurysms, while true aneurysms, in the absence of other surgical indications (i.e. refractory angina pectoris, congestive heart failure, systemic embolisation or refractory arrhythmia) are treated medically [18, 19]. Cine MR and cine CT imaging reveal, in both aneurysms and pseudoaneurysms, an akinetic/dyskinetic segment in the LV wall [18, 19]. A typical feature of pseudoaneurysm is that it has a narrow ostium connecting them to the ventricle. In most cases, the maximal width of the ostium is less than the maximal parallel internal diameter [18].

True aneurysms will show late enhancement, which indicates that their wall is formed by scar tissue secondary to infarcted myocardial muscle. Owing to the fact that their wall is composed only of pericardium, pseudoaneurysm sacs do not show late enhancement; however, their border will show enhancement, indicating a perianeurysmal infarcted area [17, 18]. There is often marked delayed enhancement of the pericardium in pseudoaneurysms, and it is uncommon or faint in true aneurysm, with a sensitivity and specificity of 100% and 83%, respectively [18]. Associated mural thrombus is common in both aneurysms and pseudoaneurysms (Fig. 2 and Video 3) [17, 18].

Apical diverticulum is a finger-like contractile pouch with connection to the ventricle [19]. It is important to differentiate apical diverticula from aneurysm and pseudoaneurysm. Ventricular diverticula are congenital, often asymptomatic and are usually incidentally found while performing diagnostic imaging procedures for other reasons [20]. The wall of the diverticulum contains all layers of the ventricular myocardium with preserved myocardial architecture [20]. Contrary to a LV aneurysm, this diverticulum shows contraction during systole, because it contains a muscular wall [19, 20]. Delayed enhancement is not seen.

In children, apical diverticula can be associated with Cantrell’s syndrome, which is a rare syndrome characterised by a partial sternal cleft, anterior abdominal wall defects, anterior diaphragmatic defect and intracardiac defects of which the ventricular septal defect is the most common and is invariably present. LV diverticulum is present in 20% to 50% of these cases [19].

Hypertrophic cardiomyopathy (HCM) is a primary and genetic myocardial disease characterised by a hypertrophied, non-dilated LV in the absence of another systemic or cardiac disease (e.g. systemic hypertension, aortic valve stenosis) capable of producing LV hypertrophy [1, 24].

There are several distinctive involvement patterns, one variant being the apical hypertrophic cardiomyopathy (AHC). Unlike usual HCM, AHC possesses typical clinical features and has a relatively good prognosis. However, it seems that the clinical course is less benign in western countries than in Japan [9].

The diagnosis is primarily based on the demonstration of localised apical hypertrophy, defined as an end-diastolic LV apical wall thickness greater than 15 mm or a ratio comparing apical LV and basal LV wall thicknesses of ≥1.3–1.5 [25].

More subjective criteria for the diagnosis of AHC include: obliteration of the LV apical cavity in systole, failure to identify a normal progressive reduction in LV wall thickness towards the apex [25] and apical aneurysm formation with delayed enhancement [25, 26]. The formation of apical aneurysm is thought to be due to ischaemia, which results from reduced capillary density, hyperplasia of the arterial media, increased perivascular fibrosis and myocardial bridging. This process usually occurs in the presence of normal epicardial coronary arteries [25].

Patchy delayed enhancement in a mid-wall location is present in most patients with HCM (Fig. 5) [25].

There are three types of apical HCM: (1) true apical form (“spade-like” configuration), (2) involvement of the apex and symmetric hypertrophy of the four ventricular wall segments, and (3) involvement of the apex with asymmetric involvement of the wall segments (“non-spade” apical HCM) [27].

The MR findings are characterised by LV myocardial oedema with a diffuse and transmural distribution better visualised on the STIR T2-weighted sequences as high signal intensity (Figs. 6, 7) that matches with wall-motion abnormalities seen on cine-MRI. Hypokinesis or akinesis in the mid- and apical segments (although it can affect the basal segments alone) of the LV causes “apical ballooning” with compensatory basal segment hyperkinesis, taking the name of Tako-Tsubo from the morphology of LV in the ventriculography, which is similar to the Japanese pot used to capture octopuses. These wall motion abnormalities can produce a dynamic obstruction in the LV outflow (LVOT) seen as a “jet” in the LVOT plane and also mitral regurgitation [28].

Tako-Tsubo cardiomyopathy and acute myocardial infarction (Fig. 8) can be clinically indistinguishable. Nevertheless, the differential diagnosis of the disorders can be suspected by the oedema location in the apical and mid-segments of LV that does not correlate with a vascular territory (Table 4) [29], and TSC has rarely been reported to cause late enhancement. Wall-motion abnormalities extend beyond the region supplied by one coronary artery. This feature is characteristic of Tako-Tsubo cardiomyopathy, whereas wall-motion abnormalities observed in acute myocardial infarction are often more localised. Acute myocarditis can also be clinically similar to TSC (acute chest pain, elevated cardiac enzymes levels and ECG changes), but has a more diffuse, heterogeneous distribution of the oedema (Fig. 9), often with sub-epicardial affectation that may be accompanied by pericardial enhancement [28].

	Tako-Tsubo	AMI	Myocarditis
Hyperintensity distribution in T2-STIR	Transmural or diffuse	Transmural or subendocardial	Medium or subepicardic
Location	Apical and mid ventricular segments without vascular distribution	Vascular distribution	Patchy, without vascular distribution
Hyperintensity durability in T2-STTR	2 weeks	More than 2 weeks

Another characteristic feature of TSC is the lack of hypoperfusion on the first-pass imaging and at rest and of late enhancement on the delayed contrast sequence (Fig. 6) in the LV segments where there is STIR spotted oedema, which allows the differentiation from anterior ST elevation myocardial infarction. A rare but serious complication is the thrombus formation in the LV. The LV wall thickness is normal [28].

In combination with clinical history and catheterisation findings, cardiac MR imaging can be useful in supporting the diagnosis and monitoring functional recovery [30]. MRI is also useful in differentiating Tako-Tsubo cardiomyopathy from myocardial infarction and myocarditis. Although coronary CT angiography is not indicated in the initial evaluation of patients with Tako-Tsubo cardiomyopathy, reports are emerging of the use of coronary CT angiography in the subsequent evaluation of patients with TSC [31].

LV non-compaction (LVNC) may be an isolated finding (isolated left ventricular non-compaction) or may be associated with other congenital heart anomalies (left ventricular non-compaction). It is a congenital cardiomyopathy [24] characterised by a thickened wall with multiple prominent ventricular trabeculations and deep intertrabecular recesses (sinusoids) in communication with the ventricular cavity, resulting in systolic and diastolic ventricular dysfunction. Non-compaction involves predominantly the apical portion of the LV chamber, with or without right ventricular involvement, due to an arrest in the normal embryogenesis [32–34].

Because both the left and right ventricles normally have trabeculations, there is always the risk of over-diagnosis of this disease. It is therefore essential to be thorough while establishing the relationship between compacted and non-compacted myocardium when the diagnosis of this entity is being made. Using MRI, the most appropriate criteria would be a ratio between non-compacted and compacted areas greater than 2.3 (Fig. 10) in a diastolic long-axis view [35].

Although ventricular non-compaction can appear similar to ventricular diverticula or prominent trabeculations (while virtually always <3 in number in normal variants), diagnosis of ventricular non-compaction usually requires the finding of more than three deep intertrabecular recesses in one imaging plane apically from the insertion of the papillary muscles [20, 32, 36]. False tendons, dilated cardiomyopathy, endocardial fibroelastosis and cardiac metastases are other important differential diagnostic considerations [34, 36].

Although echocardiography has been the diagnostic test of choice for non-compaction, other techniques have been used for the diagnosis, including CT and MRI [34]. Echocardiography may not visualise the apical region optimally, leading to underestimation of the degree of left ventricular non-compaction [37]. MRI provides good correlation with echo for the localisation and extent of non-compaction, and is useful in cases of poor echocardiographic image quality. In addition, the demonstration of differences in MRI signal intensity in non-compacted myocardium may help identify substrates for potentially lethal arrhythmias [34].

Arrhythmogenic right ventricular dysplasia (ARVD) is an uncommon form of inheritable cardiomyopathy [24] and is characterised by progressive loss of myocytes and fibrofatty replacement of the right ventricular myocardium [24, 38–41].

The diagnosis of ARVD is based on established criteria determined by a task force comprising the European Society of Cardiology and the International Society and Federation of Cardiology [42].

Reports of left ventricular involvement have led to the recognition of ARVD as a diffuse disease of the heart muscle affecting both ventricles [40, 41, 45, 46]. There is evidence of LV involvement with fibrofatty replacement, chamber enlargement and myocarditis in up to 75% of patients [24]. Focal left ventricular dyskinesia can also be present in the setting of fatty infiltration within the left ventricle [39]. Late left ventricular enhancement has also been described in patients with ARVD [39, 47]. In addition, these changes can definitely affect the LV apex.