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Infiltrative Diseases of the Heart: A Brief Overview

Infiltrative Diseases of the Heart: A Brief Overview

Infiltrative diseases affecting the heart muscle and function are lesser-known causes of heart failure but are considered major etiologies of cardiomyopathies. Infiltrative cardiomyopathies (IfCM) indicate poor prognosis; however, early detection can lead to potentially curative treatment. Therefore, it is important for clinicians to be aware of these infiltrative diseases affecting the heart.

IfCMs account for a diverse group of cardiac diseases characterized by deposition of abnormal substances within the heart tissue causing disruption in the normal ventricular wall morphology, composition, and function. The degree and extent of the cardiac abnormalities depend on the degree of infiltration and resulting changes in ventricular wall thickness, chamber dilatation, and disruption of the heart's conduction system. These pathologic changes often lead to the development of heart failure and significant arrhythmias (such as atrioventricular blocks and ventricular arrhythmias).

Common Types of Infiltrative Cardiomyopathies

  • Cardiac Amyloidosis (CAmy): This is the archetype of IfCMs. Amyloidosis is a disorder characterized by multisystem deposition of insoluble fibrillary protein called amyloid fibrils. Cardiac involvement is common in amyloidosis, and it is a significant source of morbidity and mortality. The deposition of amyloid fibrils in the heart causes abnormalities in the 3 main processes of cardiac function: contractility, conduction, and coronary blood flow. The most common presentation of CAmy is clinical heart failure with predominant symptoms of right-sided heart failure. It can also present with an acute coronary syndrome-like picture without evidence of coronary disease, syncope/pre-syncope, and atrial or ventricular arrhythmias.
  • Cardiac Sarcoidosis: The main pathologic feature of sarcoidosis is granulomatous infiltration leading to organ dysfunction. In the initial stages of cardiac sarcoidosis, there is more tissue edema present from inflammatory processes, resulting in myocardial thickness leading to diastolic dysfunction. In the later stages, the granulomatous inflammation progresses to fibrosis, leading to ventricular dilatation and global or segmental hypokinesis; thus systolic dysfunction occurs. Disruption to the heart's conduction system can occur due to the inflammation and fibrosis. The clinical presentation of cardiac sarcoidosis depends on the location and extent of granulomatous infiltration. Patients maybe asymptomatic with ECG findings consistent with conduction abnormalities, heart failure, and/or sudden cardiac death.
  • Hemochromatosis (HC): The primary pathologic feature in this condition is excessive deposition of iron. The primary or hereditary type of HC is an autosomal recessive disorder; the secondary type is caused by iron overload due to other conditions such as certain types of anemia, repeated blood transfusions, long-term hemodialysis, or chronic liver disease. In the early stages of HC cardiac involvement, excess iron is deposited in the ventricles, resulting in progressive diastolic dysfunction and restrictive physiology. In the later stages, due to remodeling specifically in the left ventricle, the left ventricle dilates and leads to systolic dysfunction. The clinical manifestations of cardiac iron deposition can be wide-ranging: They may range from classic symptoms of heart failure due to biventricular failure, to supraventricular arrhythmias or AV block due to involvement of the conduction system. Similar to the other IfCMs, in HC (either primary or secondary) the severity of cardiac dysfunction and symptoms is governed by the amount of myocardial iron deposition.
References
  • Bejar D, et al. Infiltrative cardiomyopathies. Clin Med Insights Cardiol. 2015;9(suppl 2):29.
  • Madan N, et al. Clinical evaluation of infiltrative cardiomyopathies resulting in heart failure with preserved ejection fraction. Rev Cardiovasc Med. 2020;21:181.
  • Pereira N, et al. Spectrum of restrictive and infiltrative cardiomyopathies: Part 1 of a 2-part series. JACC> 2018;71:1130.

Filed under: Cardiometabolic

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