Ventricular remodeling
Encyclopedia
Ventricular remodeling refers to the changes in size, shape, and function of the heart after injury to the ventricles. The injury is typically due to acute myocardial infarction (usually transmural or ST segment elevation infarction), but may be from a number of causes that result in increased pressure or volume overload (forms of strain) on the heart. Chronic hypertension
, congenital heart disease with intracardiac shunting, and valvular heart disease
may also lead to remodeling. After the insult occurs, a series of histopathological and structural changes occur in the left ventricular myocardium that lead to progressive decline in left ventricular performance. Ultimately, ventricular remodeling may result in diminished contractile (systolic
) function and reduced stroke volume
.
Medically speaking, "ventricular remodeling" implies a decline in function (even though the word "remodeling" usually implies improvement). The term "reverse remodeling" in cardiology implies an improvement in ventricular mechanics and function after a remote injury.
Concentric hypertrophy is due to pressure overload, while eccentric hypertrophy is due to volume overload.
s, collagen
, the interstitium, and the coronary vessels to a lesser extent, also play a role. A common scenario for remodeling is after myocardial infarction. There is myocardial necrosis
(cell death) and disproportionate thinning of the heart. This thin, weakened area is unable to withstand the pressure and volume load on the heart in the same manner as the other healthy tissue. As a result there is dilatation of the chamber arising from the infarct region. The initial remodeling phase after a myocardial infarction results in repair of the necrotic area and myocardial scarring
that may, to some extent, be considered beneficial since there is an improvement in or maintenance of LV function and cardiac output
. Over time, however, as the heart undergoes ongoing remodeling, it becomes less elliptical and more spherical. Ventricular mass and volume increase, which together adversely affect cardiac function. Eventually, diastolic function, or the heart's ability to relax between contractions may become impaired, further causing decline.
activation, genetic factors and gene expression
, and treatment. Medications may attenuate remodeling. Angiotensin-converting enzyme (ACE) inhibitors
have been consistently shown to decrease remodeling in animal models or transmural infarction and chronic pressure overload. Clinical trials have shown that ACE inhibitor therapy after myocardial infarction leads to improved myocardial performance, improved ejection fraction
, and decreased mortality compared to patients treated with placebo. Likewise, inhibition of aldosterone
, either directly or indirectly, leads to improvement in remodeling. Carvedilol
,a 3rd generation beta blocker
, may actually reverse the remodelling process by reducing left ventricular volumes and improving systolic function. Early correction of congenital heart defects, if appropriate, may prevent remodeling, as will treatment of chronic hypertension
or valvular heart disease
. Often, reverse remodeling, or improvement in left ventricular function, will also be seen.
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, congenital heart disease with intracardiac shunting, and valvular heart disease
Valvular heart disease
Valvular heart disease is any disease process involving one or more of the valves of the heart . Valve problems may be congenital or acquired...
may also lead to remodeling. After the insult occurs, a series of histopathological and structural changes occur in the left ventricular myocardium that lead to progressive decline in left ventricular performance. Ultimately, ventricular remodeling may result in diminished contractile (systolic
Systole (medicine)
Systole is the contraction of the heart. Used alone, it usually means the contraction of the left ventricle.In all mammals, the heart has 4 chambers. The left and right ventricles pump together. The atria and ventricles pump in sequence...
) function and reduced stroke volume
Stroke volume
In cardiovascular physiology, stroke volume is the volume of blood pumped from one ventricle of the heart with each beat. SV is calculated using measurements of ventricle volumes from an echocardiogram and subtracting the volume of the blood in the ventricle at the end of a beat from the volume...
.
Medically speaking, "ventricular remodeling" implies a decline in function (even though the word "remodeling" usually implies improvement). The term "reverse remodeling" in cardiology implies an improvement in ventricular mechanics and function after a remote injury.
Concentric hypertrophy is due to pressure overload, while eccentric hypertrophy is due to volume overload.
Pathophysiology
The cardiac myocyte is the major cell involved in remodeling. FibroblastFibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...
s, collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, the interstitium, and the coronary vessels to a lesser extent, also play a role. A common scenario for remodeling is after myocardial infarction. There is myocardial necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
(cell death) and disproportionate thinning of the heart. This thin, weakened area is unable to withstand the pressure and volume load on the heart in the same manner as the other healthy tissue. As a result there is dilatation of the chamber arising from the infarct region. The initial remodeling phase after a myocardial infarction results in repair of the necrotic area and myocardial scarring
Myocardial scarring
Myocardial scarring is fibrous tissue that replaces normal tissue destroyed by injury or disease pertaining to the muscular tissue of the heart....
that may, to some extent, be considered beneficial since there is an improvement in or maintenance of LV function and cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
. Over time, however, as the heart undergoes ongoing remodeling, it becomes less elliptical and more spherical. Ventricular mass and volume increase, which together adversely affect cardiac function. Eventually, diastolic function, or the heart's ability to relax between contractions may become impaired, further causing decline.
Treatment
Many factors influence the time course and extent of remodeling, including the severity of the insult, secondary events (recurrent ischemia or infarction), neurohormonalNeurohormone
A neurohormone is any hormone produced and released by neurons.Examples include:*Thyrotropin-releasing hormone *Gonadotropin-releasing hormone *Adrenocorticotropin-releasing hormone*Oxytocin*Antidiuretic hormone *Epinephrine...
activation, genetic factors and gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
, and treatment. Medications may attenuate remodeling. Angiotensin-converting enzyme (ACE) inhibitors
ACE inhibitor
ACE inhibitors or angiotensin-converting enzyme inhibitors are a group of drugs used primarily for the treatment of hypertension and congestive heart failure...
have been consistently shown to decrease remodeling in animal models or transmural infarction and chronic pressure overload. Clinical trials have shown that ACE inhibitor therapy after myocardial infarction leads to improved myocardial performance, improved ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
, and decreased mortality compared to patients treated with placebo. Likewise, inhibition of aldosterone
Aldosterone
Aldosterone is a hormone that increases the reabsorption of sodium ions and water and the release of potassium in the collecting ducts and distal convoluted tubule of the kidneys' functional unit, the nephron. This increases blood volume and, therefore, increases blood pressure. Drugs that...
, either directly or indirectly, leads to improvement in remodeling. Carvedilol
Carvedilol
Carvedilol is a non-selective beta blocker/alpha-1 blocker indicated in the treatment of mild to moderate congestive heart failure . It is marketed under various trade names including Carvil , Coreg , Dilatrend , Eucardic , and Carloc as a generic drug ., and as a...
,a 3rd generation beta blocker
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
, may actually reverse the remodelling process by reducing left ventricular volumes and improving systolic function. Early correction of congenital heart defects, if appropriate, may prevent remodeling, as will treatment of chronic hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
or valvular heart disease
Valvular heart disease
Valvular heart disease is any disease process involving one or more of the valves of the heart . Valve problems may be congenital or acquired...
. Often, reverse remodeling, or improvement in left ventricular function, will also be seen.