Myocardial and Pericardial Disease: Difference between revisions

The identification of the genetic background of HCM resulted in the hypothesis that HCM is a disease of the sarcomere; the contractile unit of the cell. First, mutations were found in the cardiac B-myosin heavy chain gene, while later on other sarcomeric proteins were found to play a role in HCM (Table 1).

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! Table 1. Sarcomeric genes associated with HCM

Two-dimensional echocardiography is the easiest diagnostic modality for detection of HCM, (Table 2) but cardiac magnetic resonance imaging (CMR) may be used when echocardiography is inconclusive, acoustic windows are insufficient, or when more detailed anatomic information is needed for clinical decision making. Echocardiographic characteristics include thickening of the left ventricular wall without cavity dilatation, and a normal or hyperdynamic left ventricle. Left ventricular outflow tract obstruction is not mandatory for the diagnosis of HCM. Moreover, as mentioned previously, although the diagnosis of HCM is based on a cut-off value for maximal wall thickness of 15 mm in the overall population, multiple HCM-linked mutations are associated with only minor LVH, but represent a high risk of sudden cardiac death.  

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!Table 2. Echocardiographic diagnostic criteria for HCM in first-degree relatives of index cases with HCM :

Electrocardiographic signs of HCM are typical as the increase in myocardial tissue increases the size of the QRS complexes. Therefore, a typical ECG characteristic of HCM is that it meets voltage criteria for LVH, and shows changes in repolarization (Table 3).

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!Table 3. Electrocardiographic diagnostic criteria for HCM in first-degree relatives of index cases with HCM :

In patients with medically refractory symptoms, whom are suboptimal candidates for invasive treatment, permanent dual chamber pacing may be considered. Pacing may alleviate symptoms by decreasing the outflow tract pressure gradient. However, maintaining a reduction in gradient requires pre-exitation of the right ventricular apex and distal septum, and complete ventricular caption. For optimal results, this should therefore be performed in highly experienced centers only.

=====Prognosis and outcome=====

In general, symptoms of HCM increase with age. Mortality rates have been reported to account between 2 and 3% per year. Most importantly, patients with HCM may be at high risk of sudden cardiac death, which may even be its initial presentation, in particular in asymptomatic or mildly symptomatic young patients. HCM is the most common cause of SCD in young people, including athletes. The pathophysiological basis for this predilection is unclarified, and although SCD is most frequent in young people less than 30 to 35 years old, an increased risk for SCD extends thereafter. Although HCM presentation and clinical manifestation is heterogeneous, and it has a relatively low prevalence, clinical markers as shown in Table 4 may identify patients at high risk for SCD. Patients at high risk of SCD are eligible candidates for ICD implantation.

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!Table 4. Risk factors for SCD

In general, a wide variety of factors can induce or contribute to the development of DCM including arterial hypertension, myocarditis, alcohol abuse or tachyarrhythmias. A subsequent increase in wall stress combined with activation of neurohumoral pathways induces complex cellular and molecular maladaptation, and programmed cell death finally leads to a decrease in the number of functioning cardiomyocytes. This process of cardiac remodelling itself results in systolic and/or diastolic dysfunction, leading to increased wall stress, and thereby creating a vicious circle of progressive systolic dysfunction (Figure 1).

The failing myocardium has several distinct factors promoting apoptosis of cardiomyocytes in vitro; cathecholamines, wall stress, angiotensin II, nitric oxide and inflammatory cytokines. Hence, medical management of DCM aims at antagonizing these pathways, reducing stress signalling in, and remodelling of the failing heart.

It is important to note that there are several causes of secondary DCM. A foursome of these is of utmost importance to recognize early on, as accurate diagnosis influences the patients treatment strategy and chance for complete recovery.

Is described under ‘Secondary Myocardial Disease’

Is described under ‘Secondary Myocardial Disease’

Is described under ‘Secondary Myocardial Disease’

Is described under ‘Secondary Myocardial Disease’

Treatment of cardiac dysfunction is treated according to the nature of cardiac involvement. Conduction disorders may present which require pacing, and standard heart failure therapy may be instituted in case of ventricular dilatation and functional impairment. Ventricular tachyarrhythmias may be found in particular in myotonic dystrophia, and require the implantation of an internal cardiac defibrillator to prevent its associated sudden cardiac death.

DCM has a highly variable clinical course. Approximately half of DCM patients respond well to routine heart failure medication, and a minority of patients even shows an improving clinical course. Conversely, a subgroup can be identified with a highly unfavourable clinical course, not responsive to heart failure medication and rapidly progressing to inotropy- or LVAD-dependency. Overall, 5-year survival rates approximate 30%.

   

An important differentiation is that between RCM and constrictive pericarditis. Constrictive pericarditis is similarly characterized by impaired ventricular filling with preserved systolic function, but may be adequately treated by pericardiectomy, which makes this distinction of major clinical importance.

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!Table 5  -- Classification of Restrictive Cardiomyopathy  

=====Infiltrative=====

Amyloidosis is a disease that results from tissue deposition of fibrils that have a distinct secondary structure of a beta-pleated sheet configuration, leading to characteristic histological changes. Amyloid depositions can occur in almost any organ, but usually remains clinically undetected unless extensive depositions are present.  

The most frequent types of amyloidosis are the AL (primary) and AA (secondary) types. AL amyloidosis is a plasma cell dyscrasia, which can occur solitarily or in association with multiple myeloma. AA amyloidosis can be considered a complication of chronic inflammatory disease states such as rheumatoid arthritis, in which the depositions consist of fragments of serum amyloid A, which is an acute phase reactant.

Hereditary amyloidosis has been increasingly recognized in the last decade, and results from mutations in the gene for thransthyretin. Some mutations are clinically limited to the myocardium. Its incidence increases with increasing age, with a predilection for men, but its prognosis is better than that of the AL type. Senile systemic amyloidosis results from deposition of normal wild-type transthyretin. This form of amyloidosis is clinically predominated by an infiltrative cardiomyopathy, but progression is slow and prognosis is better than of other acquired forms.

Cardiac amyloidosis is a progressive infiltrative cardiomyopathy. The primary form carries the highest cardiac involvement of approximately one third to half of patients, where deposits may be present even in the absence of clinical symptoms. Secondary amyloidosis is less frequently accompanied by cardiac infiltration, approximately 5% of cases, and is less likely associated with ventricular dysfunction due to a smaller size and more favourable location of the depositions. Familial amyloidosis is associated with clinical signs of cardiac involvement in a quarter of patients, typically presenting after the age of 35 with a distinct involvement of the cardiac conduction system. In senile amyloidosis, the extent of deposits may vary widely from solitarily atrial involvement up to extensive ventricular infiltration.  

*Congestive heart failure of unknown origin, not responding to contemporary medical management.

Diagnostic testing should include a 12-lead ECG, possibly with Holter monitoring, and routine echocardiography. Specific characteristics are a low-voltage 12-lead ECG with increase septal and posterior wall ventricular thickness.

A physical examination may reveal an elevated jugular venous pressure, and signs of systemic edema. Auscultation frequently reveals an apical murmur due to mitral regurgitation, and a third heart sound, but the presence of a fourth heart sound may exclude amyloidosis, as atrial infiltration causes impaired atrial contraction.

Routine 12-lead ECG shows low voltage in the limb leads, and a pseudoinfarct pattern in approximately 50% of patients. Furthermore, conduction abnormalities occur frequently, as does atrial fibrillation.

Thickening of the left ventricular wall with diastolic dysfunction are early echocardiografic features of the disease. In advancing disease, wall thickening increases, resulting in a restrictive cardiomyopathy. “Sparkling” myocardium is a distinct characteristic of cardiac amyloidosis, referring to an increased echogenicity of the myocardium. However, only a minority of patients has this pattern. Doppler evaluation shows a restrictive pattern with E dominance and a short deceleration time.

Furthermore, intracardiac thrombus is common, which is associated with atrial fibrillation and left ventricular diastolic dysfunction.

The thickening of the ventricular wall caused by amyloidosis may be misinterpreted as hypertrophy on echocardiography. An important distinctive characteristic of amyloidosis is the voltage-to-mass ratio. Unlike normal hypertrophic myocardium, the increased ventricular mass in amyloidosis is associated with a decrease in electrocardiographic voltage.

Few treatments for cardiac amyloidosis exist, and those available are dependent on the type of amyloidosis present. Hence, typing of the disease is pertinent. AL amyloidosis may be treated with chemotherapy using alkylating agents alone or in combination with bone marrow transplantation. Heart transplantation in combination with bone marrow transplantation after high-dose chemotherapy was shown to be result in approximately a third of treated patients surviving over 5 years, but as the great majority of patients with AL amyloidosis has severe non-cardiac amyloidosis, most patients are not suitable transplant candidates. Patients with other types of amyloidosis frequently have less affected hearts, and progression of the disease is slow. AA amyloidosis may respond to anti-inflammatory and immunosupressive drugs that reduce production of the acute-phase reactant protein. If heart failure is present, it is usually more prone to routine medical treatment to reduce symptoms. If needed, heart transplantation can be performed successfully. In patients where transthyretine is the amyloidogenic protein, liver transplantation may be curative as tranthyretine is produced in the liver, but the cardiac disease may progress regardless in some patients.

Overall, caution should be taken in prescribing digitalis, nifedipine, verapamil and ACE-inhibitors to cardiac amyloidosis patients. There is a high susceptibility to digitalis intoxication, nifedipine-induced hemodynamic deterioration, verapamil-induced left ventricular dysfunction, and ACE-inhibitor induced profound hypotension. If atrial fibrillation is present, or systolic ventricular function is severely impaired anticoagulation is indicated to prevent intracardiac thrombi. In selected patients with conduction disorders, pacemaker implantation may be considered. If ventricular function is severely impaired, ICD implantation may be considered. Nonetheless, prognosis of especially AL amyloidosis is poor.

Sarcoidosis is a multisystem inflammatory condition characterized by the formation of non-caseating granulomas, most frequently affecting the lungs and lymphatic system. Myocardial involvement is seen in one quarter of cases only. Genetic factors are suggested as there was found to be an aggregation of cases within families.

Non-caseating granulomas may infiltrate the myocardium, leading to fibrotic scarring of the myocardium. Involvement of the myocardium is usually patchy, resulting in a relatively high likelihood of false-negative results from biopsy. Cardiac sarcoidosis must be differentiated from chronic active myocarditis and giant cell myocarditis.

Patients may present with syncope, heart block or congestive heart failure. Sudden cardiac death may well be the initial manifestation of the disease due to malignant ventricular arrhythmias, but both atrial and ventricular arrhythmia is common at initial presentation. Symptoms of heart failure may result from direct myocardial involvement, but can also be due to extensive pulmonary fibrosis; cor pulmonale.

Minimal evaluation of a patient suspected of cardiac sarcoidosis consists of a 12-lead ECG, Holter monitoring and echocardiography.

Early detection of the disease is critical for its clinical course. Immunosuppression using corticosteroids to halt the progression of inflammation is the treatment of choice in sarcoidosis, to which myocardial dysfunction, conduction disturbances, and arrhythmias may all respond. Most important is the differentiation of sarcoidosis from giant cell myocarditis, which is a more aggressive disorder requiring intensive medical and mechanical support and frequently necessitating heart transplantation. Pacemaker or ICD implantation is indicated in patients with conduction disorders or malignant arrhythmias, as medical treatment is usually ineffective in these cases.  

=====Storage diseases=====

Hemochromatosis is defined as a disorder of the iron metabolism, resulting in accumulation of iron in parenchymal tissues. In particular cardiac, liver, gonadal and pancreatic involvements are typical for hemochromatosis, in which the toxicity of redox-active iron results in organ dysfunction. Typically, hemochromatosis leads to a combination of heart failure, cirrhosis, impotence, diabetes and arthritis. Although several organ systems are usually involved, cardiac complications predominate the initial presentation, which are dependent on the site and amount of cardiac depositions. DCM is the typical phenotype of cardiac involvement, but a restrictive pattern may be present.

The invariably present symptoms of heart failure may frequently be accompanied by arrhythmias, especially ventricular extrasystoles, supraventricular tachycardia, and atrial fibrillation or flutter; either due to atrial iron depositions, or ventricular dysfunction resulting in increased ventricular pressure. Furthermore, conduction system involvement may lead to AV block or sick sinus syndrome.

Symptoms at initial presentation may vary. Echocardiography may show increased left ventricular wall thickness, ventricular dilatation, and ventricular dysfunction. CMR imaging represents a sensitive mean and may aid in early detection of the disease. Electrocardiographic characteristics include ST-segment and T-wave abnormalities as well as supraventricular arrhythmias, but occur as the disease advances. Biochemical testing reveals increased elevated transferrine saturation, increase plasma iron levels with low or normal iron binding capacity.

Repeated phlebotomy is the cornerstone of hemochromatosis treatment, although chelating agents such as deferoxamine may be considered. Early detection of the disease is critical, as depletion of iron overload may result in complete reversal of symptoms at this stage. Evidence was found that a threshold exists beyond which iron depletion does not result in recovery of function. At end-stage disease, heart transplantation is a viable option with good survival rates. Importantly, screening of first degree relatives is important to ensure early detection of hereditary forms of hemochromatosis.

ARVC is a difficult diagnosis to make. Therefore, the European Society of Cardiology has created a list of diagnostic criteria for the diagnosis of ARVC, which were updated in 2009 (Table 6). An [http://www.arvc.ca/pdg/public.php?rep=arvc_cri online calculator] can help in assessing the risk in an individual patient.  

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! Table 6. The Revised Task Force Criteria for ARVD / ARVC Revised Task Force Criteria

A two-layered structure of the myocardium, with a thin compacted epicardial band and a thick non-compacted endomyocardial part, overall resulting in a thickened myocardium. LVNC is diagnosed by the ratio between the maximal non-compacted and compacted myocardial layer thickness measured during end-systole. In adults, a non-compacted/compacted thickness ratio of =2 confirms the diagnosis, whereas a ratio of =1.4 is considered diagnostic in children. The non-compacted layer is further characterized by prominent trabeculations, with intertrabecular spaces in direct connection with the left ventricular cavity. The non-compacted regions are predominantly found in the lateral, apical or inferior wall of the left ventricle. Where normal myocardium, originally consisting of a sponge-like structure of myocardial fibres, shows a pattern of basal to apical, and epicardial to endocardial compaction of the myocardial fibres during the 5th to 8th week of embryonal development, non-compaction supposedly originates from halting of this process due to a genetic defect.

Age of onset may be highly variable, with cyanosis, failure to thrive or dysmorphic features described in the neonatal period, to adult patients presenting with LV failure or ventricular arrhythmia. Possibly, sudden cardiac death entails one of the manifestations of LVNC, although evidence is only limited at this moment. Owing to technical advances in the field of echocardiography, predominantly an increase in image resolution, LVNC has only recently been recognized as an independent entity in the spectrum of cardiomyopathies, which supposedly has frequently been misdiagnosed as HCM in the past.

Considering the genetic background of LVNC, inheriting most commonly autosomal dominant, echocardiographic evaluation of family members of LVNC patients is pertinent.

Treatment strategies are mainly extrapolated from other cardiomyopathies: standard heart failure therapy in case of LV dysfunction, beta-blockade and/or amiodarone in non-sustained VT in the absence of LV dysfunction, and ICD placement indicated in patients with LVEF <35%, sustained VT or recurrent unexplained syncope. Routine anticoagulation in not indicated, but anticoagulation may be instituted in case of ventricular dilatation or systolic LV function impairment.

Acute inflammation of the pericardium may result from a wide variety of etiologies (Table 1), and typically presents with chest pain, a pericardial friction rub on auscultation, and repolarization changes on the electrocardiogram.   

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!Table 1. Causes of acute pericarditis

Fluid accumulation in the pericardium, pericardial effusion, is a common finding on routine echocardiography, and is asymptomatic in the absence of inflammation or cardiac tamponade. It may result from any disease of the pericardium, or be iatrogenic. Most frequently it results from idiopathic pericarditis, malignancy, or iatrogenic defects (Table 2).  

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!Table 2. Causes of pericardial effusion

Any form of pericarditis may end in constrictive pericarditis, presenting with chronic fatigue, dyspnoea, jugular distension, proto-diastolic pericardial knock, hepatomegaly, ascites, peripheral oedema, and pleural effusion. Atrial fibrillation is a common finding, and diffuse flattened or negative T-waves are usually present. These suggestive clinical findings, in addition to a physiology of restriction or constriction on echocardiography, and the presence of a thickened pericardium provide the diagnosis. However, a thickened pericardium may be absent, which does not rule out constrictive pericarditis. Pericardiectomy is the only effective treatment, which should be instituted shortly after diagnosis, as surgical mortality increases with increasing age and functional impairment.

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!colspan="2"|Table 3.  Differential diagnosis between chronic constrictive pericarditis and restrictive cardiomyopathy