Amyloidosis

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Definition

Amyloidosis is an infiltrative disease characterised by extracellular deposition of autologous protein-derived fibrils characterised by a B-sheet structure (amyloid) in various tissues.

Classification

Several subtypes of cardiac amyloidosis have been described[1]:

  • Primary amyloidosis (AL), most common form, with clinically evident cardiac involvement in about one third to half of cases [2]. AL amyloidosis develops in monoclonal gammapathies such as multiple myeloma and results from deposition of immunoglobulinlight chains.
  • Familial Transthyretin amyloidosis (ATTR)
  • Senile systemic amyloidosis (Wild-Type ATTR)
  • Isolated atrial amyloidosis (amyloid deposits derived from atrial natriuretic peptide)
  • Systemic amyloidosis (AA)

Cardiac involvement is a leading cause of morbidity and mortality, especially in primary light chains (AL) amyloidosis and transthyretin amyloidosis. Cardiac amyloidosis, presents as a progressive diastolic and subsequently systolic biventricular dysfunction and arrhythmias.

Echocardiography

Echocardiography is helpful in diagnosing the cardiac involvement in amyloidosis, although typical echocardiographic findings appear usually in the late stages of the disease[3]. New deformation imaging techniques offer promise in detecting early stages of cardiac involvement in amyloidosis. Furthermore these techniques were shown to be able to differentiate between cardiac amylodosis and various forms of left ventricular hypertrophy[4].

Conventional echocardiography

Morphological analysis

Two-dimensional echocardiography reveals a particular “granular” appearance of the myocardium resulting from extracellular amyloid deposition leading to cardiac wall thickening. This finding is nevertheless non-specific and is highly dependent on the echocardiographic machine settings [5] Cardiac chambers measurements show normally sized ventricles with increased wall thickness in both ventricles. The left ventricular wall thickening is usually concentric although assimetrical patterns with interventricular septum involvement with dynamic left ventricular outflow tract obstruction have been described [6]. Biatrial dilatation and interatrial septal thickening are a typical findings in advanced stages of the cardiac amyloidosis. In the advanced stages of the disease, bi-atrial enlargement can be seen with normally sized ventricles, a typical finding for restrictive cardiomyopathy. In the late stages, ventricular dilatation can be noted [7]. Valve thickening can also be demonstrated although usually without significant functional consequences. Pericardial effusion, usually develops in advanced stages of the disease and, when present, rarely leads to the tamponade[2].

Functional and hemodynamic analysis

Left ventricular function is usually preserved even when overt wall thickening is present. However most of the preserved left ventricular function results from maintained radial function with a clear reduced longitudinal performance [8] (this can be confirmed conventionally by measuring the MAPSE – mitral ring annular plane systolic excursion). In the late stages of the disease a systolic dysfunction of the left ventricle can be demonstrated by measuring the ejection fraction. Right ventricle systolic dysfunction develops later than left ventricle. Impairment of left ventricle diastolic function is the first functional sign of cardiac involvement. The typical stages of diastolic dysfunction seen in patients that develop restrictive cardiomyopathy can be described in cardiac amyloidosis. At first, a reduced E wave with an increased deceleration time and a reduced early diastolic velocity of the left ventricular wall (E’) are noted. In the advanced stage of the disease, an overt restrictive pattern can be found with increased E wave und decreased A wave, shortened mitral inflow deceleration time and severely reduced E’ wave velocity. [9]

New echocardiographic techniques

The new echocardiographic techniques related to deformation imaging have shown promising results in diagnosing subclinical involvement in various cardiac pathologies [10]. Tissue Doppler derived Strain and Strain Rate were able to show systolic dysfunction in patients with cardiac amyloidosis and no signs and symptoms of cardiac failure.[8] New deformation techniques were shown not only to be able to diagnose early cardiac involvement in amyloidosis but were also proven to differentiate between various conditions associated with increased left ventricular wall thickness. A pattern of apical sparing as shown by longitudinal strain analysis using speckle tracking techniques was shown to be able to differentiate cardiac involvement from other cardiac pathologies associated with increased wall thickness (hypertrophic cardiomyopathy or left ventricular hypertrophy secondary to aortic strenosis)[11]. In the latter, a globally reduced longitudinal strain was noted. Speckle tracking longitudinal strain should be performed routinely for the assessment of cardiac involvement and prognosis of the patients with amyloidosis.

Reference List

  1. Kapoor P, Thenappan T, Singh E, Kumar S, Greipp PR. Cardiac amyloidosis: a practical approach to diagnosis and management. Am J Med 2011 Nov;124(11):1006-15.
  2. 2.0 2.1 Hare JM. The dilated, restrictive and infiltrative cardiomyopathy. Braunwald's Heart Disease - A Textbook of cardiovascular medicine. eighth ed. Elsevier Saunders; 2008. p. 1751-3.
  3. Banypersad SM, Moon JC, Whelan C., Hawkins P.N., Wechalekar AD. Updates in cardiac amyloidosis: A Review. Journal of the American Heart Association 2012
  4. Liu D, Niemann M, Hu K, Herrmann S, Stork S, Knop S, et al. Echocardiographic evaluation of systolic and diastolic function in patients with cardiac amyloidosis. Am J Cardiol 2011 Aug 15;108(4):591-8.
  5. Rahman JE, Helou EF, Gelzer-Bell R, Thompson RE, Kuo C, Rodriguez ER, et al. Noninvasive diagnosis of biopsy-proven cardiac amyloidosis. J Am Coll Cardiol 2004 Feb 4;43(3):410-5.
  6. Ginghina C, Popescu BA, Jurcut R. Cardiomiopatii. Esentialul in ecocardiografie. 1 ed. Editura medicala Antaeus; 2005. p. 151-77.
  7. Badano L, Fox K, Sicari R, Zamorano JL. Disease with a main influence on myocardial tissue damage. EAE Textbook of echocardiography. 1st ed. Oxford medical press; 2011. p. 335-6.
  8. 8.0 8.1 Koyama J, Ray-Sequin PA, Falk RH. Longitudinal myocardial function assessed by tissue velocity, strain, and strain rate tissue Doppler echocardiography in patients with AL (primary) cardiac amyloidosis. Circulation 2003 May 20;107(19):2446-52.
  9. Otto MC. Cardiomyopathies, Hypertensive and Pulmonary Heart Disease. Textbook of Clinical Echocardiography. third ed. Elsevier Saunders; 2004. p. 227-59.
  10. Jurcut R, Wildiers H, Ganame J, D'hooge J, Paridaens R, Voigt JU. Detection and monitoring of cardiotoxicity-what does modern cardiology offer? Support Care Cancer 2008 May;16(5):437-45.
  11. Phelan D, Collier P, Thavendiranathan P, Popovic ZB, Hanna M, Plana JC, et al. Relative 'apical sparing' of longitudinal strain using two-dimensional speckle-tracking echocardiography is both sensitive and specific for the diagnosis of cardiac amyloidosis. Heart 2012 Aug 3.
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