Diastolic function

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In clinical cardiology the term "diastolic function" is most commonly referred as how the heart fills. [1] Parallel to "diastolic function", the term "systolic function" is usually referenced in terms of the left ventricular ejection fraction (LVEF), which is the ratio of stroke volume and end-diastolic volume. [2] Due to the epidemic of heart failure, [3] particularly the cases determined as diastolic heart failure, it is increasingly urgent and crucial to understand the meaning of “diastolic function”. Unlike "systolic function", which can be simply evaluated by LVEF, there are no established dimensionless parameters for "diastolic function" assessment. [4] Hence to further study "diastolic function" the complicated and speculative physiology must be taken into consideration.

How the heart works during its filling period still has many misconceptions remaining. To better understand diastolic function, it is crucial to realize that the left ventricle is a mechanical suction pump at, and for a little while after, the mitral valve opening. [5] In other words, when mitral valve opens, the atrium does not push blood into the ventricle, instead, it is the ventricle that mechanically "sucks" in blood from the atrium. [6] [7] The energy that drives the suction process is generated from phase of systole. During systole, to overcome the peripheral arterial load at ejection, ventricle contracts, which also compresses elastic tissues internal to and external to the myocardium. Then, when cardiac muscle relaxes, the energy captured by compressed elements releases, driving the recoil of ventricular wall until a new balanced equilibrium state is reached. [8]

During diastole, the ventricle of heart must remain elastic or compliant enough and have capacity to hold incoming blood to guarantee effectiveness of the filling phase. Hence stiffness and relaxation are ventricle's intrinsic feature parameters that are practical in evaluating and quantifying diastolic function. [9] In addition, volumetric load [10] serves as an extrinsic indicating parameter that modulates diastolic function.

Measurement

The most established index to describe left ventricular diastolic function is Tau, left ventricular diastolic time constant. Measurement of Tau is traditionally delivered in a catheter lab by an invasive method. Recently, non-invasive measurement of Tau is available for mitral regurgitation or aortic regurgitation patients in an Echo lab. [11]

There have been many attempts intending for extracting both intrinsic and extrinsic properties. Early attempts concentrated on pulse-wave Doppler-echo measured trans-mitral flow velocity contours.[ citation needed ]

In terms of filling, diastolic intervals consist of early rapid filling E-waves followed by diastasis and followed by atrial systole-generated A-waves. Empirically, E- and A- wave contours were simplified as triangles. Nowadays, triangle-based indexes, such as the peak velocities of the E- and A-waves and ratio of them, the deceleration time and time duration of the E-wave, and the velocity time integral of both E- and A- waves, are usually measured and evaluated.[ citation needed ]

The triangular approach applies to E-wave shape conveniently, especially in the past when the images rendered by technology back in days are of poor resolution quality. Nevertheless, with rapidly improving temporal resolution and image processing capabilities, the curvature of E-wave contours can be clearly identified with detailed information revealed.

Due to advancement of modern medical imaging technology, the measurement of even smaller (i.e. tissue) velocities are possible to be made, which even leads to capability to measure the longitudinal displacements of the mitral annulus. The shapes of mitral annular velocity contours used to be approximated to be triangles, whose peak height is label to be E’. E’ proved useful in selected patient populations for estimation of end-diastolic pressure (EDP). [9]

Other innovative imaging modalities consist of techniques such as speckle tracking. Speckle tracking enables strain and strain-rate measurements. It is a relatively recent instance of technological progress, due to the fact that it relies on the information content inherent in the seemingly random arrangement of bright speckles present in all echocardiographic images. [12] Even though a variety of echo-based imaging technologies represent multiple levels of research innovation, much remains to be studied in relation to how to interpret the recorded data embedded in images.

Related Research Articles

<span class="mw-page-title-main">Aortic valve</span> Valve in the human heart between the left ventricle and the aorta

The aortic valve is a valve in the heart of humans and most other animals, located between the left ventricle and the aorta. It is one of the four valves of the heart and one of the two semilunar valves, the other being the pulmonary valve. The aortic valve normally has three cusps or leaflets, although in 1–2% of the population it is found to congenitally have two leaflets. The aortic valve is the last structure in the heart the blood travels through before stopping the flow through the systemic circulation.

<span class="mw-page-title-main">Mitral valve</span> Valve in the heart connecting the left atrium and left ventricle

The mitral valve, also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two cusps or flaps and lies between the left atrium and the left ventricle of the heart. The heart valves are all one-way valves allowing blood flow in just one direction. The mitral valve and the tricuspid valve are known as the atrioventricular valves because they lie between the atria and the ventricles.

<span class="mw-page-title-main">Ventricle (heart)</span> Chamber of the heart

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 heart that is smaller than a ventricle. Interventricular means between the ventricles, while intraventricular means within one ventricle.

<span class="mw-page-title-main">Echocardiography</span> Medical imaging technique of the heart

Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging, using standard ultrasound or Doppler ultrasound. The visual image formed using this technique is called an echocardiogram, a cardiac echo, or simply an echo.

An ejection fraction (EF) is the volumetric fraction of fluid ejected from a chamber with each contraction. It can refer to the cardiac atrium, ventricle, gall bladder, or leg veins, although if unspecified it usually refers to the left ventricle of the heart. EF is widely used as a measure of the pumping efficiency of the heart and is used to classify heart failure types. It is also used as an indicator of the severity of heart failure, although it has recognized limitations.

End-systolic volume (ESV) is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.

<span class="mw-page-title-main">Afterload</span> Pressure in the wall of the left ventricle during ejection

Afterload is the pressure that the heart must work against to eject blood during systole. Afterload is proportional to the average arterial pressure. As aortic and pulmonary pressures increase, the afterload increases on the left and right ventricles respectively. Afterload changes to adapt to the continually changing demands on an animal's cardiovascular system. Afterload is proportional to mean systolic blood pressure and is measured in millimeters of mercury.

<span class="mw-page-title-main">Diastole</span> Part of the cardiac cycle

Diastole is the relaxed phase of the cardiac cycle when the chambers of the heart are re-filling with blood. The contrasting phase is systole when the heart chambers are contracting. Atrial diastole is the relaxing of the atria, and ventricular diastole the relaxing of the ventricles.

<span class="mw-page-title-main">Aortic regurgitation</span> Medical condition

Aortic regurgitation (AR), also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a consequence, the cardiac muscle is forced to work harder than normal.

<span class="mw-page-title-main">Mitral regurgitation</span> Form of valvular heart disease

Mitral regurgitation(MR), also known as mitral insufficiency or mitral incompetence, is a form of valvular heart disease in which the mitral valve is insufficient and does not close properly when the heart pumps out blood. It is the abnormal leaking of blood backwards – regurgitation from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Mitral regurgitation is the most common form of valvular heart disease.

<span class="mw-page-title-main">Preload (cardiology)</span>

In cardiac physiology, preload is the amount of sarcomere stretch experienced by cardiac muscle cells, called cardiomyocytes, at the end of ventricular filling during diastole. Preload is directly related to ventricular filling. As the relaxed ventricle fills during diastole, the walls are stretched and the length of sarcomeres increases. Sarcomere length can be approximated by the volume of the ventricle because each shape has a conserved surface-area-to-volume ratio. This is useful clinically because measuring the sarcomere length is destructive to heart tissue. It requires cutting out a piece of cardiac muscle to look at the sarcomeres under a microscope. It is currently not possible to directly measure preload in the beating heart of a living animal. Preload is estimated from end-diastolic ventricular pressure and is measured in millimeters of mercury (mmHg).

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 is placed on the chest or abdomen of the subject to get various views of the heart. It is used as a non-invasive assessment of the overall health of the heart, including a patient's heart valves and degree of heart muscle contraction. The images are displayed on a monitor for real-time viewing and then recorded.

<span class="mw-page-title-main">Cardiac cycle</span> Performance of the human heart

The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole. After emptying, the heart relaxes and expands to receive another influx of blood returning from the lungs and other systems of the body, before again contracting to pump blood to the lungs and those systems. A normally performing heart must be fully expanded before it can efficiently pump again. Assuming a healthy heart and a typical rate of 70 to 75 beats per minute, each cardiac cycle, or heartbeat, takes about 0.8 second to complete the cycle. There are two atrial and two ventricle chambers of the heart; they are paired as the left heart and the right heart—that is, the left atrium with the left ventricle, the right atrium with the right ventricle—and they work in concert to repeat the cardiac cycle continuously. At the start of the cycle, during ventricular diastole–early, the heart relaxes and expands while receiving blood into both ventricles through both atria; then, near the end of ventricular diastole–late, the two atria begin to contract, and each atrium pumps blood into the ventricle below it. During ventricular systole the ventricles are contracting and vigorously pulsing two separated blood supplies from the heart—one to the lungs and one to all other body organs and systems—while the two atria are relaxed. This precise coordination ensures that blood is efficiently collected and circulated throughout the body.

<span class="mw-page-title-main">Valvular heart disease</span> Disease in the valves of the heart

Valvular heart disease is any cardiovascular disease process involving one or more of the four valves of the heart. These conditions occur largely as a consequence of aging, but may also be the result of congenital (inborn) abnormalities or specific disease or physiologic processes including rheumatic heart disease and pregnancy.

The E/A ratio is a marker of the function of the left ventricle of the heart. It represents the ratio of peak velocity blood flow from left ventricular relaxation in early diastole to peak velocity flow in late diastole caused by atrial contraction. It is calculated using Doppler echocardiography, an ultrasound-based cardiac imaging modality. Abnormalities in the E/A ratio suggest that the left ventricle, which pumps blood into the systemic circulation, cannot fill with blood properly in the period between contractions. This phenomenon is referred to as diastolic dysfunction and can eventually lead to the symptoms of heart failure.

A plot of a system's pressure versus volume has long been used to measure the work done by the system and its efficiency. This analysis can be applied to heat engines and pumps, including the heart. A considerable amount of information on cardiac performance can be determined from the pressure vs. volume plot. A number of methods have been determined for measuring PV-loop values experimentally.

Mitral valve annuloplasty is a surgical technique for the repair of leaking mitral valves. Due to various factors, the two leaflets normally involved in sealing the mitral valve to retrograde flow may not coapt properly. Surgical repair typically involves the implantation of a device surrounding the mitral valve, called an annuloplasty device, which pulls the leaflets together to facilitate coaptation and aids to re-establish mitral valve function.

<span class="mw-page-title-main">Heart failure with preserved ejection fraction</span> Medical condition

Heart failure with preserved ejection fraction (HFpEF) is a form of heart failure in which the ejection fraction – the percentage of the volume of blood ejected from the left ventricle with each heartbeat divided by the volume of blood when the left ventricle is maximally filled – is normal, defined as greater than 50%; this may be measured by echocardiography or cardiac catheterization. Approximately half of people with heart failure have preserved ejection fraction, while the other half have a reduction in ejection fraction, called heart failure with reduced ejection fraction (HFrEF).

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 of the reflected ultrasound. The technique is the same as for flow Doppler echocardiography measuring flow velocities. Tissue signals, however, have higher amplitude and lower velocities, and the signals are extracted by using different filter and gain settings. The terms tissue Doppler imaging (TDI) and tissue velocity imaging (TVI) are usually synonymous with TDE because echocardiography is the main use of tissue Doppler.

<span class="mw-page-title-main">Sándor J. Kovács</span>

Sándor J. Kovács is a Hungarian-American academic cardiologist and cardiovascular physiologist, best known for his work on the physiological dynamics of the human heart. He is a professor of medicine, physics, physiology, and biomedical engineering at Washington University in St. Louis.

References

  1. ↑ Nagueh, S. F.; Appleton, C. P.; Gillebert, T. C.; Marino, P. N.; Oh, J. K.; Smiseth, O. A.; Waggoner, A. D.; Flachskampf, F. A.; Pellikka, P. A. (2009-03-01). "Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography". European Journal of Echocardiography. 10 (2): 165–193. doi: 10.1093/ejechocard/jep007 . hdl: 1854/LU-631868 . ISSN   1525-2167. PMID   19270053.
  2. ↑ "Ejection Fraction | Cleveland Clinic". Cleveland Clinic. Retrieved 2017-01-26.
  3. ↑ Dunlay, Shannon M.; Roger, Véronique L. (2017-01-26). "Understanding the Epidemic of Heart Failure: Past, Present, and Future". Current Heart Failure Reports. 11 (4): 404–415. doi:10.1007/s11897-014-0220-x. ISSN   1546-9530. PMC   4224604 . PMID   25182014.
  4. ↑ Wei Zhang; Shmuylovich, L.; Kovacs, S.J. (2009). "The pressure recovery ratio: The invasive index of LV relaxation during filling. Model-based prediction with in-vivo validation". 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society. pp. 3940–3943. doi:10.1109/IEMBS.2009.5333092. ISSN   1557-170X. PMID   19963805. S2CID   23928657.{{cite book}}: |journal= ignored (help)
  5. ↑ Forouhar, Arian S.; Liebling, Michael; Hickerson, Anna; Nasiraei-Moghaddam, Abbas; Tsai, Huai-Jen; Hove, Jay R.; Fraser, Scott E.; Dickinson, Mary E.; Gharib, Morteza (2006-05-05). "The embryonic vertebrate heart tube is a dynamic suction pump" (PDF). Science. 312 (5774): 751–753. Bibcode:2006Sci...312..751F. doi:10.1126/science.1123775. ISSN   1095-9203. PMID   16675702. S2CID   12453342.
  6. ↑ Katz, Louis N. (1930-12-01). "The Rôle Played by the Ventricular Relaxation Process in Filling the Ventricle". American Journal of Physiology. Legacy Content. 95 (3): 542–553. doi:10.1152/ajplegacy.1930.95.3.542. ISSN   0002-9513.
  7. ↑ Robinson, T. F.; Factor, S. M.; Sonnenblick, E. H. (1986-06-01). "The heart as a suction pump". Scientific American. 254 (6): 84–91. Bibcode:1986SciAm.254f..84R. doi:10.1038/scientificamerican0686-84. ISSN   0036-8733. PMID   3704622.
  8. ↑ Brutsaert, D. L.; Sys, S. U. (1989-10-01). "Relaxation and diastole of the heart". Physiological Reviews. 69 (4): 1228–1315. doi:10.1152/physrev.1989.69.4.1228. ISSN   0031-9333. PMID   2678168.
  9. 1 2 Burkhoff, Daniel (2002). "MECHANICAL PROPERTIES OF THE HEART AND ITS INTERACTION WITH THE VASCULAR SYSTEM" (PDF). Cardiac Physiology: 1–23 – via Columbia University.
  10. ↑ Batyraliev, T. A.; Samko, A. N.; Grudtsyn, G. V.; Gorgaslidze, A. G.; Zinkin, A. V. (1988-03-01). "Volumetric load in the diagnosis of early right-ventricular heart failure in patients with alcoholic heart damage". Kardiologiia. 28 (3): 83–86. ISSN   0022-9040. PMID   2454344.
  11. ↑ Wen, Chaoyang; Sun, Jing; Fan, Chunzhi; Dou, Jianping (August 2018). "Calculation of Left Ventricular Diastolic Time Constant (TAU) in Dogs with Mitral Regurgitation Using Continuous-Wave Doppler". Ultrasound in Medicine & Biology. 44 (8): 1778–1785. doi:10.1016/j.ultrasmedbio.2018.03.023. PMID   29735313. S2CID   205539634.
  12. ↑ Helle-Valle, Thomas; Crosby, Jonas; Edvardsen, Thor; Lyseggen, Erik; Amundsen, Brage H.; Smith, Hans-Jørgen; Rosen, Boaz D.; Lima, João A. C.; Torp, Hans (2005-11-15). "New noninvasive method for assessment of left ventricular rotation: speckle tracking echocardiography". Circulation. 112 (20): 3149–3156. doi: 10.1161/CIRCULATIONAHA.104.531558 . hdl: 10852/37505 . ISSN   1524-4539. PMID   16286606.
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