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The Current Role of Echocardiography in
the Evaluation of Primary Cardiomyopathies

Jamil Mattar Valente, MD

Federal University of Santa Catarina and
Institute of Cardiology of the State of Santa Catarina,
Florianopolis, SC, Brazil

INTRODUCTION
   The primary cardiomyopathies are part of a group of myocardial diseases in that the dominant characteristic is the direct compromising of the heart muscle. They are not secondary to pericardial diseases, systemic hypertension, valvulopathies, coronary artery disease, or congenital heart defects.

   In 1995, the World Health Organization (WHO) modified the classification of the cardiomyopathies (1), in agreement with new acquired concepts on the pathogenicity of the muscular heart disease. According to this new classification, primary cardiomyopathies can be:

1 - Dilated
2 - Restrictive
3 - Hypertrophic
4 - Arrhythmogenic Right Ventricular Dysplasia
5 - Non Classified

   The cardiac ultrasonography in an exciting and linear way, has developed in what concerns to hardware, software, acquisition of new techniques and knowledge. It has been selected the method of choice on diagnostic evaluation, follow-up and analysis of treatment results of primary cardiomyopathies. The current ultrasound equipments exhibit an impressive improvement of heart image resolution and Doppler effect sensibility. New resources as the tissue Doppler, motivate the development of more studies, whose results are already adding themselves to the current resources on the prognostic and diagnostic evaluation of myocardial diseases.

DILATED CARDIOMYOPATHY
   Characteristically in Dilated Cardiomyopathy, the left ventricle becomes more spherical (2) and end systolic volume is increased, even sometimes before evident fall in ejection fraction. When the end systolic volume index of the left ventricle is greater than 30 mL/m2 of body surface, it indicates significant systolic dysfunction. Ischemic cardiomyopathy studies, although we should consider that it is not a primary cardiomyopathy, can discriminate patients with poor prognostic, when the end systolic volume index is greater than 45 mL/m2. On initial phase of Dilated Cardiomyopathy, we can have subtle anatomic and hemodynamic compromising. The echocardiogram in this phase may not demonstrate significant modifications, and the evaluation can be sometimes difficult, even for experienced examiners. It is advisable in these cases, off-line analysis by three experienced observers. Sometimes we find patients that present primary diffuse left ventricle hypokinesis, severe or not, but without increase of the cavities size. For the current World Health Organization classification, this pathology is a Non Classified Cardiomyopathy, though its behavior and treatment is the same of Dilated Cardiomyopathy, and we should probably be in front of a same disease. For this, the name Dilated Cardiomyopathy may be inappropriate and perhaps we can call it Hypocontractile Cardiomyopathy.

   Echocardiography is not useful on etiological diagnosis of this myocardial pathology. Exception to this happens in Chagas Disease, where this method can demonstrate a cardiomyopathy with regional compromising.

   It is common to find a volume increase of all four cardiac chambers, but sometimes, this volume increase is just of left chambers, or only of the left ventricle. The left ventricular walls habitually have normal thickness, or sometimes they may be thinner, especially in more advanced disease degree.

   The predominant hemodynamic compromise is left ventricular systolic dysfunction. Ejection fraction is below 50%. A diffuse hypokinesis is observed, with poor systolic thickness of the walls (fig. 1). The difference between end diastolic and end systolic diameters is narrow.

Figure 1

   On M mode, an increased separation of the mitral E point is observed in relation to the interventricular septum. This distance becomes larger than 1 cm and presents good correlation with left ventricular ejection fraction and shortening fraction. The mitral valve leaflets excursion amplitude is decreased (fig. 2), as well as also the aortic valve leaflets (fig. 3). This is observed when the disease is in an advanced stage, and it is due to a smaller transvalvar blood flow. With the increase of left ventricular end diastolic pressure, occurs an appearance of a B wave that comes soon after the A wave, giving an aspect of a pine tree tumbled to the mitral valve leaflets.

Figure 2

Figure 3

   The Doppler study allows the determination and quantification of the mitral valvar competence. The detection of associated moderate or severe mitral insufficiency is a sign of worse prognosis. Besides, it is possible to estimate left ventricular dP/dt with continuous Doppler, when there is mitral regurgitation. Marking a point at the speed level of 1 m/s and other at 3 m/s, we have the time that left ventricular systolic pressure took to increase from 4 to 36 mmHg. Then it is extrapolated for one second and we will have the value of the left ventricular systolic pressure increase in mmHg/s. The most recent equipments already own software to achieve this calculation. Values above 1000 mmHg/s are normal. The figure 4 shows an evaluation of a patient with dilated cardiomyopathy, and the result was 533 mmHg/sec. A study with 61 patients showed that a value below 600 mmHg/sec identify a group of high mortality (3). The analysis of left ventricular inflow through pulsed Doppler, with the sample volume positioned on the tip of the mitral valve leaflets, allows the identification of a flow of restrictive pattern in the most severe cases 4. The restrictive pattern is determined by an increased E/A ratio and by deceleration time of the mitral E wave below 150 ms. The appropriate acquisition of a good tracing of the pulmonary venous flow, usually of the superior left pulmonary vein through the apical 4 chamber view, allows the quantification of mean left atrial pressure (fig 5). In a recent study, Kinnaird and cols. 5 measuring the deceleration time of the pulmonary venous diastolic flow slope, observed a more accurate result than the invasive measure of occlusive pulmonary capillary wedge pressure, to predict the mean left atrial pressure. The authors developed the following regression equation: MLAP = 53.236 - [0.302 DTD] + [0.000484 (DTD2 )].

Figure 4

Figure 5

   Nagueh and cols. (6) studied the relationship of the pulsed Doppler measured initial left ventricular inflow velocity (E wave), with the pulsed tissue Doppler measured initial diastolic lateral mitral ring velocity by apical 4 chambers view (Ea wave) (fig. 6). Correlating with the invasive measurement of the mean occlusive pressure of the pulmonary artery, they have got the following regression equation: Mean pulmonary capillary wedge pressure = 1,24 (E/Ea) + 1,9. In a series of 60 patients, they obtained an r = 0.87. The authors observed later that this was a reliable measure even when accomplished by sinus tachycardia.

Figure 6

Measures of systolic flow acceleration time of the right ventricular outflow tract, and also when present, of the tricuspid regurgitation velocity, provide valuable information on the pulmonary artery pressure.

RESTRICTIVE CARDIOMYOPATHY
   
Definition: It is characterized by a compromising of the right and/or left ventricular endocardium and/or myocardium, leading to a decrease of compliance of their walls and restriction to the ventricular filling, in the absence of chambers dilation or important systolic dysfunction.

   Hemodynamic consequences: They depend on the degree of compromising of both ventricles. The atrium corresponding to the committed ventricle, works under increased pressure. In the beginning of the diastole a larger pressure gradient exists between the atrium and the ventricle, causing a decreased isovolumetric relaxation time. After the rapid ventricular filling, abruptly occurs a decrease of the flow, when the compliance of the ventricle prematurely achieves its limit. The intraventricular diastolic pressure rapidly increases and forms a "plateau" giving a classic curve in square root form. The atrial contraction contributes little to the ventricular filling, because it faces a very high ventricular end diastolic pressure, tending to equalize the atrial pressure, or even surpassing it and causing regurgitation through the atrioventricular valve during diastole.

   Causes: It can be caused by a series of systemic diseases. Diabetes mellitus is the most frequent cause, although most of the time it doesn't provoke important diastolic restriction. Amyloidosis, glycogen storage disease, thalassemia, sarcoidosis, hemochromatosis and endomyocardial fibrosis can be involved. It can be idiopathic. State of cardiac transplant rejection can lead to a clinical picture of restrictive compromising.

  Differential diagnosis: It includes constrictive pericarditis that in spite of causing similar hemodynamic consequences has different treatment (7). Rajagopalan and cols. (8) recently studied 30 patients referred for evaluation of diastolic function, which had a diagnosis of constrictive pericarditis or restrictive cardiomyopathy established by diagnostic tests, including the clinical evaluation, magnetic resonance image, cardiac catheterization, endomyocardial biopsy and surgical findings. Nineteen patients had constrictive pericarditis and eleven had restrictive cardiomyopathy. The respiratory variation of the mitral E wave pick larger than or equal to 10% predicted constrictive pericarditis with 84% of sensibility and 91% of specificity and the variation of the velocity of the pulmonary venous diastolic pick (D wave) larger than or equal to 18% distinguished pericardial constriction with 79% of sensibility and 91% of specificity. Using the tissue Doppler echocardiography, the velocity of the lateral mitral ring Ea wave obtained with the apical 4 chambers view, if larger than or equal to 8,0 cm/s, differentiated patient with pericardial constriction from restriction with 89% of sensibility and 100% of specificity. A slope larger than or equal to 100 cm/s in the evaluation of M mode color Doppler flow propagation, predicted constriction with 74% of sensibility and 91% of specificity. Fig. 7 and Fig. 8.

Figure 7

Figure 8

   Echocardiographic changes: As well as in dilated cardiomyopathy, the echocardiogram has been the non-invasive method of choice in the evaluation of restrictive cardiomyopathy. The pulsed Doppler ventricular inflow shows a restrictive pattern (9). The E wave, corresponding to the rapid ventricular filling, shows usually increased velocity, and decreased deceleration time (<160 ms). The E/A ratio is increased and the A wave has a decreased peak velocity. The contractility of committed ventricle(s) can be normal or slightly decreased. A flow of restrictive ventricular filling in the presence of a discreetly decreased or normal systolic function is strongly indicative of restrictive cardiomyopathy.

   The thickness of the left or right ventricular walls is increased (in the infiltrative forms as in the storage diseases) or normal. As atrial pressure is increased in the initial diastole, the isovolumetric relaxation time is decreased. During diastole the intraventricular pressure increases quickly and may occur diastolic mitral or tricuspid regurgitation. The hepatic venous flow unlike the normal individual, shows a D wave > S wave, and increase of the reverse A wave on inspiration (10). It differs from constrictive pericarditis, which has an S wave > D wave and the reverse A wave is prominent during expiration. The atria show great volume increase with ventricles of normal size. Pulsed tissue Doppler of the mitral valvar ring (8) almost always shows a Ea wave with velocity < 8,0 cm/s.

   In endomyocardial fibrosis, the diastolic restriction occurs by the formation of a fibrous or calcified tissue on endocardium. It especially occurs on apical area and on ventricular inflow tract. It sometimes also attacks the subvalvular apparatus causing mitral or tricuspid dysfunction. The mitral or tricuspid valvar dysfunction worsens the hemodynamic compromising. The compromising can be univentricular or biventricular.

   In cardiac amyloidosis, the left ventricular filling pattern may be initially of decreased relaxation type with E mitral wave smaller than A wave and deceleration time larger than 230 ms. In a more advanced stage, the left ventricular inflow pattern changes to a restrictive type. The myocardial tissue characterization shows hyperechogenic diffuse granulations because of the infiltration of amyloid tissue in the myocardium. Sometimes the interatrial septum may exhibit increased thickness.

HYPERTROPHIC CARDIOMYOPATHY
   
Definition: It is characterized by an accentuated and disproportionate hypertrophy of the left ventricle, sometimes also committing the right ventricle, in the absence of pressure or volume overload. The interventricular septum usually suffers a disproportionate hypertrophy in relation to the remaining of the left ventricle and for that, it is also called asymmetrical septal hypertrophy, although it sometimes exhibits completely concentric hypertrophy. Occurs a reduction of the left ventricular volume and a lot of times, dynamic left intraventricular obstruction, generating intracavitary pressure gradient during the systole, with maximum peak at the end of the systole. The primary hypertrophic cardiomyopathy can be subclassified in 2 types: obstructive and non obstructive.

   Hemodynamic changes: The systolic left ventricular function is normal, except in the final stages, when may occur hypocontractility, and the presence of a diffuse left ventricular hypokinesis translates bad prognosis. The hemodynamic changes that may occur are diastolic dysfunction that cannot be evident in an initial phase, and the intracavitary obstruction of the left ventricle, which can be located in the outflow tract (more common), intermediate area or apical area (rarer). The disproportionate increase of the muscular mass in relation to the vascular territory and the dynamic left intraventricular obstruction can originate myocardial ischemia even in the absence of obstructive coronary disease (relative ischemia). The dynamic intraventricular obstruction leads to a pressure overload, which contributes to the progression of the ventricular hypertrophy. The diastolic dysfunction, the dynamic intraventricular obstruction and the relative ischemia are the protagonists in the genesis of the symptoms. Tachycardia, hypovolemia, use of positive inotropic drugs and situations that reduce the venous return as the Valsalva maneuver, increase the degree of intracavitary obstruction and elevate the pressure gradient.

   Causes: About 70% of the cases has a family occurrence, with dominant autosomal inheritance. It can be idiopathic.

   Differential diagnosis: It should especially be done with the fixed subaortic stenosis, a congenital disease in that there is persistence of a subaortic membranous ring which causes a pressure gradient on the outflow tract of the left ventricle and secondary concentric left ventricular hypertrophy. The treatment is completely different from the hypertrophic cardiomyopathy. The pressure gradient peak occurs on the middle of the systole and not on the end as in the primary obstructive hypertrophic cardiomyopathy. Disproportionate hypertrophy of the interventricular septum doesn't occur. On transthoracic and still better on transesophageal echocardiogram, the presence of a membrane can be observed obstructing the left ventricular outflow tract.

   In older individuals we have to be careful to not to confuse the interventricular basal septum hypertrophy, or the angulation of the septum, which cause obstruction of the left ventricular outflow tract, with hypertrophic cardiomyopathy.

   Other entities that eventually offer confusion possibility are the systemic arterial hypertension, which occurs in 20% of the adult population and the aortic valvar stenosis. Both can generate secondary concentric hypertrophy of the left ventricle in accentuated degree and may coexist with the primary hypertrophic cardiomyopathy.

   Echocardiographic changes: It stands out the exaggerating and disproportionate hypertrophy of the interventricular septum, which is well visualized through the M mode and two-dimensional mode (Figs. 9 and 10). There is a significant increase of the left ventricular mass. In some cases there may be a variation of the area of hypertrophy, prevailing in the apical area of the left ventricle. This variation has larger incidence in individuals of the Japanese race.

Figure 9

Figure 10

   Also in hypertrophic cardiomyopathy, the echocardiogram stands out as the method of choice in the diagnosis, follow-up and prognostic evaluation. The left ventricular cavity can have normal dimensions but it is usually decreased. The systolic function of the left ventricle is normal or increased. The presence of left ventricular systolic dysfunction in primary hypertrophic cardiomyopathy is a sign of bad prognosis. Such finding is seen in individuals in terminal stage. It can have dynamic obstruction during systole, which may be localized in the outflow tract (more frequent), intermediate area or apical area of the left ventricle. When left intraventricular dynamic obstruction occurs, it is called obstructive hypertrophic cardiomyopathy. Usually when dynamic intracavitary obstruction exists, a systolic anterior movement of the mitral valve leaflet is seen, going to the interventricular septum during the systole, causing a reduction of the area of the left ventricle outflow tract. This anomalous movement of the anterior mitral leaflet many times also leads to a lack of appropriate coaptation of the valve leaflets. This lack of coaptation causes mitral regurgitation of varied degrees, sometimes with severe mitral insufficiency and aggravation of the hemodynamic compromising. In hypertrophic cardiomyopathy of the obstructive type, we may observe systolic vibrations of the aortic valve leaflets and still partial closing of the leaflets of the aortic valve in the midsystole. With pulsed Doppler, placing the sample volume in the outflow tract of the left ventricle, just after the area of intracavitary obstruction, it is obtained a turbulent flow of high velocity with maximum peak in the end of the systole, giving a dagger form to the registration of the curve. This is due to the fact that the left intraventricular pressure increases with evolution of the systole and reaches the peak at the end of the systole. Through the measure of the peak velocity of the flow, we obtain the peak intraventricular pressure gradient. This dynamic pressure gradient sometimes occurs only during physical effort, being absent in rest. We use in a routine way, the measure of the velocity of the left intraventricular systolic flow, with and without Valsalva maneuver. This maneuver allows us to have an approximate idea of what occurs with the intraventricular pressure gradient during the physical effort. The Valsalva maneuver increases the intrathoracic pressure and reduces the venous return to the heart, causing decrease of the left ventricular filling and increase of the intracavitary obstruction during the systole. After proof of the presence of left intraventricular dynamic obstruction, we should evaluate the possibility of concomitant aortic valvar stenosis. In the absence of valvar aortic stenosis, continuous Doppler in the left ventricular cavity will show in a more accurate way high velocity flows, allowing reliable quantification of the left intraventricular gradient. We have to take care of not confuse the mitral valve regurgitation with the flow of the left ventricular outflow tract during the use of continuous Doppler.

   Older carriers of hypertrophic cardiomyopathy, frequently present calcification of the mitral valvar ring. The diastolic dysfunction of the left ventricle may not be present on the initial stages, but it is frequent during the evolution of the cardiomyopathy. The sample volume of pulsed Doppler placed in the inflow tract of the left ventricle, shows a E wave with slow slope and smaller amplitude than the A wave. With the appearance of the diastolic dysfunction, also appears an increase of the left ventricular isovolumetric relaxation time. Just in a terminal stage we can see a left ventricle filling of restrictive pattern.

   The echocardiogram is quite useful also in the evaluation of the treatment results. The improvement resulting from the conservative or invasive treatment, results in reduction of the intraventricular gradient and of the left ventricular diastolic dysfunction, and it is correlated with the symptomatology improvement.

   Nagueh and cols. (11) recently published a study using pulsed tissue Doppler to measure the mitral valvar ring velocity, in which, consistently they detected abnormalities in the longitudinal myocardial contractility in patients with hypertrophic cardiomyopathy. This new resource of the echocardiography was capable to detect the disease precociously, before and independently of the hypertrophy appearance. The authors studied with two-dimensional echocardiography, Doppler and pulsed tissue Doppler, thirty patients with family hypertrophic cardiomyopathy. Of this group, thirteen individuals were positive for several genetic mutations but they didn't present left ventricular hypertrophy. Other thirty normal individuals were studied as control. The thickness of the walls of the left ventricle and the left ventricular mass was significantly larger in the individuals with family hypertrophic cardiomyopathy versus those without hypertrophy and those of the control group. There were not significant differences in the two-dimensional echocardiogram and Doppler between the mutation positive individuals without hypertrophy and those of the control group. However on tissue Doppler, the systolic (S wave) and initial diastolic (Ea wave) velocities were significantly lower in the group with family hypertrophic cardiomyopathy, inclusive in the thirteen individuals mutation positive without hypertrophy, when compared to the control group (p <0,001). These reduced velocities to tissue Doppler had a sensibility of 100% and a specificity of 93% to identify individuals mutation positive without left ventricular hypertrophy.

RIGHT VENTRICULAR ARRHYTHMOGENIC CARDIOMYOPATHY
   Definition: It is a primary disease of the myocardium, characterized by a regional substitution of myocardial fibers by fibrous fat tissue of the right ventricle, with or without involvement of the left ventricle, but relatively sparing the interventricular septum (1,12,13). By the fact that sometimes occurs involvement of the left ventricle, possibly would be more appropriate to call it of Arrhythmogenic Fibrodysplasic Cardiomyopathy.

   Hemodynamic changes: Monomorphic ventricular tachycardia with left bundle branch block morphology on ECG is the more commonly observed arrhythmia in the Right Ventricular Arrhythmogenic Cardiomyopathy (RVAC). Right cardiac failure can sometimes occurs (16). Cardiac sudden death is the most preoccupying event, being more frequent than the right cardiac failure (17), and if prevented, the life expectation can be normal or close of the normal. The cardiac sudden death more frequently occurs in patients with right ventricular diffuse dilation (55%) and in those with left ventricular involvement (36-56%) compared to those with localized compromising of the right ventricle (8%) (13). The left ventricular compromising seems to be a risk factor for ventricular fibrillation and sudden death with a sensibility of 56% and specificity of 86% (13).

   Causes: The disease has a family occurrence in at least 30% of cases, with a dominant autosomal inheritance and incomplete penetrance (14). A recessive form with compromising of the skin and hair (Naxos Disease) has been recognized (15).

   Differential diagnosis: The regional isolated ischemic compromising of the right ventricle may sometimes cause clinical and echocardiographic diagnostic difficulty, though the coronary arteriography can explain these cases. Dilated cardiomyopathy can be excluded easily because there is in this last condition a diffuse involvement of the two ventricles.

   Echocardiographic changes: The diagnosis of right ventricular arrhythmogenic cardiomyopathy is a sum of different anatomical and electric characteristics, including a positive family history for sudden death or ventricular arrhythmias. In this cardiomyopathy class, unlike the others, the echocardiography isolated is not a powerful diagnostic method and it should be used in association with other diagnostic methods and clinical data. Of great importance is the presence of changes in global or regional contractility of the right ventricle, which can be detected through the echocardiography most of the time. In some cases an increase of the right ventricular cavity volume is present. The magnetic resonance image has been a valuable method on diagnosis of this cardiomyopathy. Besides usually revealing contractility changes and an increase of the right ventricular volume, it still exhibits changes of the myocardium texture caused by substitution of the muscular fibers by fibroadipose tissue.

   The dilation of the right ventricular cavity can be diffuse or localized on outflow tract. Akinesis or dyskinesis areas may be present especially on outflow tract, on apex or below the tricuspid valve and in the inferior wall of the right ventricle. These areas are characterized by a thinning of the free wall. It is important also to visualize through apical view, the apex of the right ventricle, which is frequently involved. The apical view is also useful for the evaluation of the interventricular septum, which is involved more rarely, and for the exclusion of the extension of the disease to the left ventricle. Compromising of the left ventricle is found in some specific subgroups of right ventricular arrhythmogenic cardiomyopathy, probably genetically determined.

REFERENCES

1. Richardson P, McKenna W, Bristow M, Maisch B, Mautner B, O'Connell J, Olsen E, Thiene G, Goodwin J, Gyarfas I, Martin I, Nordet P. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation. 1996 Mar 1;93(5):841-2.

2. Simonson JS, Schiller NB. Descent of the base of the left ventricle: an echocardiographic index of left ventricular function. J Am Soc Echocardiogr. 1989 Jan-Feb;2(1):25-35.

3. Kolias TJ, Aaronson KD, Armstrong WF. Doppler-derived dP/dt and -dP/dt predict survival in congestive heart failure. J Am Coll Cardiol. 2000 Nov 1;36(5):1594-9.

4. Hansen A, Haass M, Zugck C, Krueger C, Unnebrink K, Zimmermann R, Kuebler W, Kuecherer H. Prognostic value of Doppler echocardiographic mitral inflow patterns: implications for risk stratification in patients with chronic congestive heart failure. J Am Coll Cardiol. 2001 Mar 15;37(4):1049-55.

5. Kinnaird T.D., Thompson C. R., Munt B. I. The Deceleration Time of Pulmonary Venous Diastolic Flow Is More Accurate Than the Pulmonary Artery Occlusion Pressure in Predicting Left Atrial Pressure. J Am Coll Cardiol. 2001 Jun 15;37(8):2025-30.

6. Nagueh SF, Middleton KJ, Kopelen HA, Zoghbi WA, Quinones MA. Doppler tissue imaging: a noninvasive technique for evaluation of left ventricular relaxation and estimation of filling pressures. J Am Coll Cardiol. 1997 Nov 15;30(6):1527-33.

7. Hancock EW. Differential diagnosis of restrictive cardiomyopathy and constrictive pericarditis. Heart. 2001 Sep;86(3):343-9.

8. Rajagopalan N, Garcia MJ, Rodriguez L, Murray RD, Apperson-Hansen C, Stugaard M, Thomas JD, Klein AL. Comparison of new Doppler echocardiographic methods to differentiate constrictive pericardial heart disease and restrictive cardiomyopathy. Am J Cardiol. 2001 Jan 1;87(1):86-94.

9. Fernando Guadalajara J, Vera-Delgado A, Gaspar-Hernandez J, Galvan-Montiel O, Huerta-Hernandez D. Echocardiographic Aspects of Restrictive Cardiomyopathy: Their Relationship with Pathophysiology. Echocardiography. 1998 Apr;15(3):297-314.

10. Hatle LK, Appleton CP, Popp RL. Differentiation of constrictive pericarditis and restrictive cardiomyopathy by Doppler echocardiography. Circulation. 1989 Feb;79(2):357-70.

11. Nagueh SF, Bachinski LL, Meyer D, Hill R, Zoghbi WA, Tam JW, Quinones MA, Roberts R, Marian AJ. Tissue Doppler imaging consistently detects myocardial abnormalities in patients with hypertrophic cardiomyopathy and provides a novel means for an early diagnosis before and independently of hypertrophy. Circulation. 2001 Jul 10;104(2):128-30.

12. McKenna WJ, Thiene G, Nava A et al. Diagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy. Task Force of the Working Group Myocardial and Pericardial Disease of the European Society of Cardiology and of the Scientific Council on Cardiomyopathies of the International Society and Federation of Cardiology . Br Heart J 1994; 71: 215-8.

13. Priori SG, Aliot E, Blomstrom-Lundqvist C, Bossaert L, Breithardt G, Brugada P, Camm AJ, Cappato R, Cobbe SM, Di Mario C, Maron BJ, McKenna WJ, Pedersen AK, Ravens U, Schwartz PJ, Trusz-Gluza M, Vardas P, Wellens HJ, Zipes DP. Task force on sudden cardiac death of the european society of cardiology. Eur Heart J. 2001 Aug;22(16):1374-450.

14. Rampazzo A, Nava A, Danieli GA et al. The gene for arrhythmogenic right ventricular cardiomyopathy maps to chromosome 14q23-q24 . Hum Mol Genet 1994; 3: 959-62.

15. McKoy G, Protonotarios N, Crosby A et al. Identification of a deletion in plakoglobin in arrhythmogenic right ventricular cardiomyopathy with palmoplantar keratoderma and woolly hair (Naxos disease) . Lancet 2000; 355: 2119-24.

16. Peters S. Right ventricular cardiomyopathy: diffuse dilatation, focal dysplasia or biventricular disease . Int J Cardiol 1997; 62: 63-7.

17. Corrado D, Basso C, Thiene G et al. Spectrum of clinicopathologic manifestations of arrhythmogenic right ventricular cardiomyopathy/dysplasia: a multicenter study . J Am Coll Cardiol 1997; 30: 1512-20.

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2nd Virtual Congress of Cardiology

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