| Ventricle | |
|---|---|
 Computer generated animation of cut section of the humanheart showing both ventricles. | |
| Details | |
| Identifiers | |
| Latin | ventriculus cordis |
| MeSH | D006352 |
| TA98 | A12.1.00.012 |
| FMA | 7100 |
| Anatomical terminology | |
Aventricle is one of two large chambers located toward the bottom of theheart that collect and expelblood towards the peripheral beds within the body and lungs. The bloodpumped by a ventricle is supplied by anatrium, an adjacent chamber in the upper heart that is smaller than a ventricle. Interventricular means between the ventricles (for example theinterventricular septum), while intraventricular means within one ventricle (for example anintraventricular block).
In a four-chambered heart, such as that inhumans, there are two ventricles that operate in adouble circulatory system: the right ventricle pumps blood into thepulmonary circulation to thelungs, and the left ventricle pumps blood into thesystemic circulation through theaorta.
Ventricles have thicker walls than atria and generate higherblood pressures. The physiological load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles. Further, theleft ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs.[citation needed][1]
On the inner walls of the ventricles are irregular muscular columns calledtrabeculae carneae which cover all of the inner ventricular surfaces except that of theconus arteriosus, in the right ventricle. There are three types of these muscles. The third type, thepapillary muscles, give origin at their apices to thechordae tendinae which attach to the cusps of thetricuspid valve and to themitral valve.
The mass of the left ventricle, as estimated bymagnetic resonance imaging, averages 143 g ± 38.4 g, with a range of 87–224 g.[2]
Theright ventricle is equal in size to the left ventricle[citation needed] and contains roughly 85 millilitres (3 imp fl oz; 3 US fl oz) in the adult. Its upper front surface is circled and convex, and forms much of thesternocostal surface of the heart. Its under surface is flattened, forming part of the diaphragmatic surface of the heart that rests upon the diaphragm.
Its posterior wall is formed by theventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. Its upper and left angle forms a conical pouch, theconus arteriosus, from which the pulmonary artery arises. A tendinous band, called the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta.[citation needed]
The left ventricle is longer and more conical in shape than the right, and on transverse section its concavity presents an oval or nearly circular outline. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart. The left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure.
The right ventricle is triangular in shape and extends from the tricuspid valve in the right atrium to near theapex of the heart. Its wall is thickest at the apex and thins towards its base at the atrium. When viewed via cross section however, the right ventricle seems to be crescent shaped.[3][4] The right ventricle is made of two components: the sinus and the conus. The Sinus is the inflow which flows away from the tricuspid valve.[5] Three bands made from muscle, separate the right ventricle: the parietal, the septal, and the moderator band.[5] The moderator band connects from the base of the anterior papillary muscle to the ventricular septum.[4][6]
By young adulthood, the walls of the left ventricle have thickened from three to six times greater than that of the right ventricle. This reflects the typical five times greater pressure workload this chamber performs while accepting blood returning from the pulmonary veins at ~80mmHg pressure (equivalent to around 11 kPa) and pushing it forward to the typical ~120mmHg pressure (around 16.3 kPa) in the aorta during each heartbeat. (The pressures stated are resting values and stated as relative to surrounding atmospheric which is the typical "0" reference pressure used in medicine.)
Duringsystole, the ventricles contract, pumping blood through the body. Duringdiastole, the ventricles relax and fill with blood again.
The left ventricle receives oxygenated blood from theleft atrium via themitral valve and pumps it through theaorta via theaortic valve, into the systemic circulation. The left ventricular muscle must relax and contract quickly and be able to increase or lower its pumping capacity under the control of the nervous system. In the diastolic phase, it has to relax very quickly after each contraction so as to quickly fill with the oxygenated blood flowing from thepulmonary veins. Likewise in the systolic phase, the left ventricle must contract rapidly and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure. The extra pressure exerted is also needed to stretch the aorta and other arteries to accommodate the increase in blood volume.
The right ventricle receives deoxygenated blood from the right atrium via thetricuspid valve and pumps it into the pulmonary artery via thepulmonary valve, into the pulmonary circulation.
The typical healthy adult heart pumping volume is ~5 liters/min, resting. Maximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes.
Incardiology, the performance of the ventricles are measured with several volumetric parameters, includingend-diastolic volume (EDV),end-systolic volume (ESV),stroke volume (SV) andejection fraction (Ef).
| Ventricular volumes | ||
|---|---|---|
| Measure | Right ventricle | Left ventricle |
| End-diastolic volume | 144 mL (± 23 mL)[7] | 142 mL (± 21 mL)[8] |
| End-diastolic volume / body surface area (mL/m2) | 78 mL/m2 (± 11 mL/m2)[7] | 78 mL/m2 (± 8.8 mL/m2)[8] |
| End-systolic volume | 50 mL (± 14 mL)[7] | 47 mL (± 10 mL)[8] |
| End-systolic volume / body surface area (mL/m2) | 27 mL/m2 (± 7 mL/m2)[7] | 26 mL/m2 (± 5.1 mL/m2)[8] |
| Stroke volume | 94 mL (± 15 mL)[7] | 95 mL (± 14 mL)[8] |
| Stroke volume / body surface area (mL/m2) | 51 mL/m2 (± 7 mL/m2)[7] | 52 mL/m2 (± 6.2 mL/m2)[8] |
| Ejection fraction | 66% (± 6%)[7] | 67% (± 4.6%)[8] |
| Heart rate | 60–100bpm[9] | 60–100bpm[9] |
| Cardiac output | 4.0–8.0L/minute[10] | 4.0–8.0L/minute[10] |
| Site | Normal pressure range (inmmHg)[11] | |
|---|---|---|
| Central venous pressure | 3–8 | |
| Right ventricular pressure | systolic | 15–30 |
| diastolic | 3–8 | |
| Pulmonary artery pressure | systolic | 15–30 |
| diastolic | 4–12 | |
| Pulmonary vein/ | 2–15 | |
| Left ventricular pressure | systolic | 100–140 |
| diastolic | 3–12 | |
Ventricular pressure is a measure ofblood pressure within the ventricles of theheart.[12]
During most of thecardiac cycle, ventricular pressure is less than the pressure in theaorta, but duringsystole, the ventricular pressure rapidly increases, and the two pressures become equal to each other (represented by the junction of the blue and red lines on the diagram on this page), theaortic valve opens, and blood is pumped to the body.
Elevated left ventricular end-diastolic pressure has been described as a risk factor in cardiac surgery.[13]
Noninvasive approximations have been described.[14]
An elevated pressure difference between theaortic pressure and the left ventricular pressure may be indicative ofaortic stenosis.[15]
Right ventricular pressure demonstrates a different pressure-volume loop than left ventricular pressure.[16]
The heart and its performance are also commonly measured in terms ofdimensions, which in this case meansone-dimensional distances, usually measured in millimeters. This is not as informative as volumes but may be much easier to estimate with (e.g.,M-Mode echocardiography[17] or withsonomicrometry, which is mostly used for animal model research). Optimally, it is specified with which plane the distance is measured in, e.g. the dimension of thelongitudinal plane.[18]
| Dimension | Abbreviation | Definition | Normally |
|---|---|---|---|
| End-diastolic dimension | EDD | The diameter across a ventricle at the end ofdiastole, if not else specified then usually referring to the transverse[19] (left-to-right) internal (luminal) distance, excluding thickness of walls, although it can also be measured as the external distance. | |
| LVEDD or sometimes LVDD | The end-diastolic dimension of the left ventricle. | 48 mm,[20] Range 36 – 56 mm[21] |
| RVEDD or sometimes RVDD | The end-diastolic dimension of the right ventricle. | Range 10 – 26 mm[21] |
| End-systolic dimension | ESD | ESD is similar to the end-diastolic dimension, but is measured at the end ofsystole (after the ventricles have pumped out blood) rather than at the end ofdiastole. | |
| LVESD or sometimes LVSD | The end-systolic dimension of the left ventricle. | Range 20 – 40 mm[21] |
| RVESD or sometimes RVSD | The end-systolic dimension of the right ventricle. | Range 10 – 26 mm[21] |
| Interventricular septal end diastolic dimension | IVSd | The thickness of theinterventricular septum. | 8.3 mm,[20] Range 7 – 11 mm[21] |
| Left ventricular end diastolic posterior wall dimension | LVPWd | The thickness of the posterior left ventricular wall. | 8.3 mm,[20] Range 7 – 11 mm[21] |
| Meanleft ventricular myocardial thickness | Mean LVMT | Average thickness of the left ventricle, with numbers given as 95%prediction interval for the short axis images at the mid-cavity level[22] | Women: 4 - 8 mm[22] Men: 5 - 9 mm[22] |
| Meanright ventricular myocardial thickness | Mean RVMT | Average thickness of the right ventricle, with numbers given as 95%prediction interval.[23] | 4 - 7 mm[23] |
| Left ventricular end systolic dimension | As above but measured during systole. This measurement is not commonly used clinically. | 16 mm[24] | |
| Left atrial dimension | LA | Range 24 – 40 mm[21] |
Fractional shortening (FS) is thefraction of any diastolic dimension that is lost in systole. When referring to endocardialluminal distances, it is EDD minus ESD divided by EDD (times 100 when measured in percentage).[25] Normal values may differ somewhat dependent on whichanatomical plane is used to measure the distances. Normal range is 25–45%, Mild is 20–25%, Moderate is 15–20%, and Severe is <15%.[26] Cardiology Diagnostic Tests Midwall fractional shortening may also be used to measure diastolic/systolic changes for inter-ventricular septal dimensions[27] and posterior wall dimensions. However, both endocardial and midwall fractional shortening are dependent on myocardial wall thickness, and thereby dependent on long-axis function.[28] By comparison, a measure of short-axis function termed epicardial volume change (EVC) is independent of myocardial wall thickness and represents isolated short-axis function.[28]
Anarrhythmia is anirregular heartbeat that can occur in the ventricles or atria. Normally the heartbeat is initiated in theSA node of the atrium but initiation can also occur in thePurkinje fibres of the ventricles, giving rise topremature ventricular contractions, also called ventricular extra beats. When these beats become grouped the condition is known asventricular tachycardia.[citation needed]
Another form of arrhythmia is that of theventricular escape beat. This can happen as a compensatory mechanism when there is a problem in the conduction system from the SA node.[citation needed]
The most severe form of arrhythmia isventricular fibrillation which is the most common cause ofcardiac arrest and subsequentsudden death.
