In
cardiology
Cardiology () is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart d ...
, ventricular dyssynchrony is a difference in the timing, or lack of synchrony, of contractions in different
ventricles in the
heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...
. Large differences in timing of contractions can reduce cardiac efficiency and is correlated with
heart failure
Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
.
Types of dyssynchrony
Three chief presentations of dyssynchrony can occur:
Atrioventricular (AV) dyssynchrony occurs when there is an unfavorable difference in timing between
atrial
The atrium ( la, ātrium, , entry hall) is one of two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular valves.
There are two atr ...
and
ventricular contractions.
Interventricular dyssynchrony occurs when there is a difference in timing between
right ventricular
A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...
(RV) and
left ventricular
A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...
(LV) Systole.
Intraventricular dyssynchrony occurs when the timing in a sequence of activations and contractions of segments of the LV wall becomes abnormal.
In all three types, changes in timing lead to changes in the dynamic behavior of the myocardial tissues, leading to ''mechanical dyssynchrony''.
All three presentations allow distinct and easily reproducible electrical signatures as illustrated by left and right bundle branch blocks, hemiblocks, etc. The concise measurement of the time and morphology of the QRS interval allows the interventional ability to manipulate this interval with biventricular pacemakers.
It is important to distinguish ventricular dyssynchrony from ventricular ''dyssynergy''. Dyssynergy refers to changes in relative strength of contractions, whereas dyssynchrony is a change in relative timing of contractions.
Once again the terms inotropy and chronotropy apply to the pathology under examination. Biventricular pacing strongly favors chronotropy over inotropy.
Diagnosis
Echocardiography
An echocardiography, echocardiogram, cardiac echo or simply an echo, is an ultrasound of the heart.
It is a type of medical imaging of the heart, using standard ultrasound or Doppler ultrasound.
Echocardiography has become routinely used in t ...
and
tissue Doppler echocardiography
Tissue Doppler echocardiography (TDE) is a medical ultrasound technology, specifically a form of echocardiography that measures the velocity of the heart muscle (myocardium) through the phases of one or more heartbeats by the Doppler effect (freque ...
are both needed to fully diagnose the different types of ventricular dyssynchrony.
Treatment
Recent studies suggest that
cardiac resynchronization therapy can reduce the incidence of ventricular dyssynchrony and thus increase cardiac efficiency.
See also
*
Bundle branch block
A bundle branch block is a defect in one the bundle branches in the electrical conduction system of the heart.
Anatomy and physiology
The heart's electrical activity begins in the sinoatrial node (the heart's natural pacemaker), which is situat ...
*
Ejection fraction
An ejection fraction (EF) is the volumetric fraction (or portion of the total) of fluid (usually blood) ejected from a chamber (usually the heart) with each contraction (or heartbeat). It can refer to the cardiac atrium, ventricle, gall bladder, ...
*
Pacemaker syndrome
Pacemaker syndrome is a condition that represents the clinical consequences of suboptimal atrioventricular (AV) synchrony or AV dyssynchrony, regardless of the pacing mode, after pacemaker implantation.
It is an iatrogenic disease—an adverse ...
*
Speckle tracking echocardiography
In the fields of cardiology and medical imaging, speckle tracking echocardiography (STE) is an echocardiographic imaging technique. It analyzes the motion of tissues in the heart by using the naturally occurring speckle pattern in the myocardium ...
*
Transthoracic echocardiogram
A transthoracic echocardiogram (TTE) is the most common type of echocardiogram, which is a still or moving image of the internal parts of the heart using ultrasound. In this case, the probe (or ultrasonic transducer) is placed on the chest or abdo ...
References
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Cardiac arrhythmia