Myocardial perfusion imaging

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Myocardial perfusion imaging
Nl mpi2.jpg
Myocardial perfusion scan with thallium-201 for the rest images (bottom rows) and Tc-Sestamibi for the stress images (top rows)
Synonyms Myocardial perfusion scintigraphy
ICD-10-PCS C22G
MeSH D055414
OPS-301 code 3-704, 3-721
eMedicine 2114292

Myocardial perfusion imaging or scanning (also referred to as MPI or MPS) is a nuclear medicine procedure that illustrates the function of the heart muscle (myocardium). [1]

Contents

It evaluates many heart conditions, such as coronary artery disease (CAD), [2] hypertrophic cardiomyopathy and heart wall motion abnormalities. It can also detect regions of myocardial infarction by showing areas of decreased resting perfusion. The function of the myocardium is also evaluated by calculating the left ventricular ejection fraction (LVEF) of the heart. This scan is done in conjunction with a cardiac stress test. The diagnostic information is generated by provoking controlled regional ischemia in the heart with variable perfusion.

Planar techniques, such as conventional scintigraphy, are rarely used. Rather, single-photon emission computed tomography (SPECT) is more common in the US. With multihead SPECT systems, imaging can often be completed in less than 10 minutes. With SPECT, inferior and posterior abnormalities and small areas of infarction can be identified, as well as the occluded blood vessels and the mass of infarcted and viable myocardium. [3] The usual isotopes for such studies are either thallium-201 or technetium-99m.

History

The history of nuclear cardiology began in 1927 when Dr. Herrmann Blumgart developed the first method for measuring cardiac strength by injecting subjects with a radioactive compound known as Radium C (214Bi). [4] [5] The substance was injected into the venous system and travelled through the right heart into the lungs, then into the left heart and out into the arterial system where it was then detected through a Wilson chamber. The Wilson chamber represented a primitive scintillation counter which could measure radioactivity. Measured over time, this sequential acquisition of radioactivity produced what was known as "circulation time". The longer the "circulation time", the weaker the heart. Blumgart's emphasis was twofold. First, radioactive substances could be used to determine cardiac physiology (function) and should be done so with the least amount of radioactivity necessary to do so. Secondly, to accomplish this task, one needs to obtain multiple counts over time.[ citation needed ]

For decades no substantial work was done, until 1959. Dr. Richard Gorlin's work on "resting" studies of the heart and nitroglycerin emphasized several points. [6] First, like Blumgart, he emphasized that evaluation of cardiac function required multiple measurements of change over time and these measurements must be performed under same state conditions, without changing the function of the heart in between measurements. If one is to evaluate ischemia (reductions in coronary blood flow resulting from coronary artery disease) then individuals must be studied under "stress" conditions and comparisons require "stress-stress" comparisons. Similarly, if tissue damage (heart attack, myocardial infarction, cardiac stunning or hibernation) is to be determined, this is done under "resting" conditions. Rest-stress comparisons do not yield adequate determination of either ischemia or infarction. By 1963, Dr. William Bruce, aware of the tendency of people with coronary artery disease to experience angina (cardiac chest discomfort) during exercise, developed the first standardized method of "stressing" the heart, where serial measurements of changes in blood pressure, heart rate and electrocardiographic (ECG/EKG) changes could be measured under "stress-stress" conditions. By 1965 Dr. William Love demonstrated that the cumbersome cloud chamber could be replaced by a Geiger counter, which was more practical to use. However, Love had expressed the same concern as many of his colleagues, namely that there were no suitable radioisotopes available for human use in the clinical setting. [7]

Use of thallium-201

By the mid-1970s, scientists and clinicians alike began using thallium-201 as the radioisotope of choice for human studies. [8] Individuals could be placed on a treadmill and be "stressed" by the "Bruce protocol" and when near peak performance, could be injected with thallium-201. The isotope required exercise for an additional minute to enhance circulation of the isotope. Using nuclear cameras of the day and given the limitations of Tl-201, the first "stress" image could not be taken until 1 hour after "stress". In keeping with the concept of comparison images, the second "stress" image was taken 4 hours after "stress" and compared with the first. The movement of Tl-201 reflected differences in tissue delivery (blood flow) and function (mitochondrial activity). The relatively long half-life of Tl-201 (73 hours) forced doctors to use relatively small (74–111 MBq or 2–3 mCi) doses of Tl-201, albeit with relatively large dose exposure and tissue effects (20 mSv). The poor quality images resulted in the search for isotopes which would produce better results. [9]

The introduction of technetium-99m isotopes

By the late 1980s, two different compounds containing technetium-99m were introduced: teboroxime [10] and sestamibi. The utilization of Tc-99m would allow higher doses (up to 1,100 MBq or 30 mCi) due to the shorter physical (6 hours) half life of Tc-99m. This would result in more decay, more scintillation and more information for the nuclear cameras to measure and turn into better pictures for the clinician to interpret.[ citation needed ]

Major indications

Radiation dose

From 1993 to 2001, myocardial perfusion scans in the US increased >6%/y with "no justification". [12] Myocardial perfusion imaging scans are "powerful predictors of future clinical events", and in theory may identify patients for whom aggressive therapies should improve outcome. But this is "only a hypothesis, not a proof". [12] However, several trials have indicated the high sensitivity (90%) of the test, regardless of tracer, outweighing any potential detrimental effect of the ionising radiation. [13] [14] In the UK, NICE guidance recommends myocardial perfusion scans following myocardial infarction or reperfusion interventions. [15] The power of prognosis from a myocardial perfusion scan is excellent and has been well tested, and this is "perhaps the area of nuclear cardiology where the evidence is most strong". [13] [16]

Many radionuclides used for myocardial perfusion imaging, including rubidium-82, technetium-99m and thallium-201 have similar typical effective doses (15-35 mSv). [17] The Cardiac PET tracer nitrogen-13 ammonia, though less widely available, may offer significantly reduced doses (2 mSv). [17] [18] [19] [20] Stress-only protocols may also prove to be effective at reducing costs and patient exposure. [21]

Related Research Articles

<span class="mw-page-title-main">Angina</span> Chest discomfort due to not enough blood flow to heart muscle

Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease.

<span class="mw-page-title-main">Coronary circulation</span> Circulation of blood in the blood vessels of the heart muscle (myocardium)

Coronary circulation is the circulation of blood in the arteries and veins that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle. Cardiac veins then drain away the blood after it has been deoxygenated. Because the rest of the body, and most especially the brain, needs a steady supply of oxygenated blood that is free of all but the slightest interruptions, the heart is required to function continuously. Therefore its circulation is of major importance not only to its own tissues but to the entire body and even the level of consciousness of the brain from moment to moment. Interruptions of coronary circulation quickly cause heart attacks, in which the heart muscle is damaged by oxygen starvation. Such interruptions are usually caused by coronary ischemia linked to coronary artery disease, and sometimes to embolism from other causes like obstruction in blood flow through vessels.

<span class="mw-page-title-main">Single-photon emission computed tomography</span> Nuclear medicine tomographic imaging technique

Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera, but is able to provide true 3D information. This information is typically presented as cross-sectional slices through the patient, but can be freely reformatted or manipulated as required.

<span class="mw-page-title-main">Cardiac stress test</span> Measures the hearts ability to respond to external stress in a controlled clinical environment

A cardiac stress test is a cardiological test that measures the heart's ability to respond to external stress in a controlled clinical environment. The stress response is induced by exercise or by intravenous pharmacological stimulation.

Technetium (<sup>99m</sup>Tc) sestamibi Pharmaceutical drug

Technetium (99mTc) sestamibi (INN) is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex consisting of the radioisotope technetium-99m bound to six (sesta=6) methoxyisobutylisonitrile (MIBI) ligands. The anion is not defined. The generic drug became available late September 2008. A scan of a patient using MIBI is commonly known as a "MIBI scan".

<span class="mw-page-title-main">Scintigraphy</span> Diagnostic imaging test in nuclear medicine

Scintigraphy, also known as a gamma scan, is a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue (radiopharmaceuticals) are taken internally and the emitted gamma radiation is captured by external detectors to form two-dimensional images in a similar process to the capture of x-ray images. In contrast, SPECT and positron emission tomography (PET) form 3-dimensional images and are therefore classified as separate techniques from scintigraphy, although they also use gamma cameras to detect internal radiation. Scintigraphy is unlike a diagnostic X-ray where external radiation is passed through the body to form an image.

<span class="mw-page-title-main">Isotopes of thallium</span> Nuclides with atomic number of 81 but with different mass numbers

Thallium (81Tl) has 41 isotopes with atomic masses that range from 176 to 216. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years. 207Tl, with a half-life of 4.77 minutes, has the longest half-life of naturally occurring Tl radioisotopes. All isotopes of thallium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

In medicine, collateralization, also vessel collateralization and blood vessel collateralization, is the growth of a blood vessel or several blood vessels that serve the same end organ or vascular bed as another blood vessel that cannot adequately supply that end organ or vascular bed sufficiently.

Myocardial stunning or transient post-ischemic myocardial dysfunction is a state of mechanical cardiac dysfunction that can occur in a portion of myocardium without necrosis after a brief interruption in perfusion, despite the timely restoration of normal coronary blood flow. In this situation, even after ischemia has been relieved and myocardial blood flow (MBF) returns to normal, myocardial function is still depressed for a variable period of time, usually days to weeks. This reversible reduction of function of heart contraction after reperfusion is not accounted for by tissue damage or reduced blood flow, but rather, its thought to represent a perfusion-contraction "mismatch". Myocardial stunning was first described in laboratory canine experiments in the 1970s where LV wall abnormalities were observed following coronary artery occlusion and subsequent reperfusion.

Avijit Lahiri is a researcher in cardiology in the UK.

Perfusion is the passage of fluid through the lymphatic system or blood vessels to an organ or a tissue. The practice of perfusion scanning is the process by which this perfusion can be observed, recorded and quantified. The term perfusion scanning encompasses a wide range of medical imaging modalities.

<span class="mw-page-title-main">Coronary ischemia</span> Medical condition

Coronary ischemia, myocardial ischemia, or cardiac ischemia, is a medical term for a reduced blood flow in the coronary circulation through the coronary arteries. Coronary ischemia is linked to heart disease, and heart attacks. Coronary arteries deliver oxygen-rich blood to the heart muscle. Reduced blood flow to the heart associated with coronary ischemia can result in inadequate oxygen supply to the heart muscle. When oxygen supply to the heart is unable to keep up with oxygen demand from the muscle, the result is the characteristic symptoms of coronary ischemia, the most common of which is chest pain. Chest pain due to coronary ischemia commonly radiates to the arm or neck. Certain individuals such as women, diabetics, and the elderly may present with more varied symptoms. If blood flow through the coronary arteries is stopped completely, cardiac muscle cells may die, known as a myocardial infarction, or heart attack.

<span class="mw-page-title-main">Myocardial infarction</span> Interruption of blood supply to a part of the heart

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops in the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat or feeling tired. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause heart failure, an irregular heartbeat, cardiogenic shock or cardiac arrest.

Technetium (<sup>99m</sup>Tc) tetrofosmin Chemical compound

Technetium (99mTc) tetrofosmin is a drug used in nuclear medicine cardiac imaging. It is sold under the brand name Myoview. The radioisotope, technetium-99m, is chelated by two 1,2-bis[di-(2-ethoxyethyl)phosphino]ethane ligands which belong to the group of diphosphines and which are referred to as tetrofosmin.

Rubidium-82 (82Rb) is a radioactive isotope of rubidium. 82Rb is widely used in myocardial perfusion imaging. This isotope undergoes rapid uptake by myocardiocytes, which makes it a valuable tool for identifying myocardial ischemia in Positron Emission Tomography (PET) imaging. 82Rb is used in the pharmaceutical industry and is marketed as Rubidium-82 chloride under the trade names RUBY-FILL and CardioGen-82.

<span class="mw-page-title-main">Myocardial scarring</span>

Myocardial scarring is the accumulation of fibrous tissue resulting after some form of trauma to the cardiac tissue. Fibrosis is the formation of excess tissue in replacement of necrotic or extensively damaged tissue. Fibrosis in the heart is often hard to detect because fibromas, scar tissue or small tumors formed in one cell line, are often formed. Because they are so small, they can be hard to detect by methods such as magnetic resonance imaging. A cell line is a path of fibrosis that follow only a line of cells.

<span class="mw-page-title-main">Coronary perfusion pressure</span>

Coronary perfusion pressure (CPP) refers to the pressure gradient that drives coronary blood pressure. The heart's function is to perfuse blood to the body; however, the heart's own myocardium must, itself, be supplied for its own muscle function. The heart is supplied by coronary vessels, and therefore CPP is the blood pressure within those vessels. If pressures are too low in the coronary vasculature, then the myocardium risks ischemia with subsequent myocardial infarction or cardiogenic shock.

A diagnosis of myocardial infarction is created by integrating the history of the presenting illness and physical examination with electrocardiogram findings and cardiac markers. A coronary angiogram allows visualization of narrowings or obstructions on the heart vessels, and therapeutic measures can follow immediately. At autopsy, a pathologist can diagnose a myocardial infarction based on anatomopathological findings.

<span class="mw-page-title-main">Cardiac magnetic resonance imaging perfusion</span>

Cardiac magnetic resonance imaging perfusion, also known as stress CMR perfusion, is a clinical magnetic resonance imaging test performed on patients with known or suspected coronary artery disease to determine if there are perfusion defects in the myocardium of the left ventricle that are caused by narrowing of one or more of the coronary arteries.

<span class="mw-page-title-main">Cardiac imaging</span>

Cardiac imaging refers to minimally invasive imaging of the heart using ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), or nuclear medicine (NM) imaging with PET or SPECT. These cardiac techniques are otherwise referred to as echocardiography, Cardiac MRI, Cardiac CT, Cardiac PET and Cardiac SPECT including myocardial perfusion imaging.

References

  1. ↑ Myocardial+Perfusion+Imaging at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  2. ↑ Lee, J. C.; West, M. J.; Khafagi, F. A. (2013). "Myocardial perfusion scans". Australian Family Physician. 42 (8): 564–7. PMID   23971065.
  3. ↑ Merck manuals > Radionuclide Imaging Last full review/revision May 2009 by Michael J. Shea, MD. Content last modified May 2009
  4. ↑ Blumgart HL, Yens OC. Studies on the velocity of blood flow: I. The method utilized. J Clin Investigation 1927;4:1-13.
  5. ↑ Love, William D. (1965). "Isotope Technics in Clinical Cardiology" (PDF). Circulation. 32 (2): 309–315. doi: 10.1161/01.CIR.32.2.309 . PMID   14340959 . Retrieved 27 April 2012.
  6. ↑ Gorlin R, Brachfeld N, MacLeod C. and Bopp P. Effect of nitroglycerin on the coronary circulation in patients with coronary artery disease or increased left ventricular work. Circulation 1959;19:705-18.
  7. ↑ Love WD. (1965) Isotope Technics in Clinical Cardiology. Circulation 32:309-15.
  8. ↑ DePuey, E. Gordon; Garcia, Ernest V.; Berman, Daniel Sholom (2001). Cardiac SPECT Imaging. Lippincott Williams & Wilkins. p. 117. ISBN   9780781720076.
  9. ↑ Strauss, H. William; Bailey, Dale (March 2009). "Resurrection of Thallium-201 for Myocardial Perfusion Imaging". JACC: Cardiovascular Imaging. 2 (3): 283–285. doi: 10.1016/j.jcmg.2009.01.002 . PMID   19356572.
  10. ↑ Bisi, G; Sciagrà, R; Santoro, GM; Cerisano, G; Vella, A; Zerauschek, F; Fazzini, PF (July 1992). "Myocardial scintigraphy with Tc-99m-teboroxime: its feasibility and the evaluation of its diagnostic reliability. A comparison with thallium-201 and coronary angiography". Giornale Italiano di Cardiologia. 22 (7): 795–805. PMID   1473653.
  11. ↑ Multimodality Writing Group for Stable Ischemic Heart Disease; et al. (February 2014). "ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease: a report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons". Journal of Cardiac Failure. 20 (2): 65–90. doi:10.1016/j.cardfail.2013.12.002. PMID   24556531.
  12. 1 2 Lauer, Michael S. (27 August 2009). "Elements of Danger — The Case of Medical Imaging". New England Journal of Medicine. 361 (9): 841–843. doi:10.1056/NEJMp0904735. PMID   19710480.
  13. 1 2 Underwood, S. R.; Anagnostopoulos, C.; Cerqueira, M.; Ell, P. J.; Flint, E. J.; Harbinson, M.; Kelion, A. D.; Al-Mohammad, A.; Prvulovich, E. M.; Shaw, L. J.; Tweddel, A. C. (1 February 2004). "Myocardial perfusion scintigraphy: the evidence". European Journal of Nuclear Medicine and Molecular Imaging. 31 (2): 261–291. doi:10.1007/s00259-003-1344-5. PMC   2562441 . PMID   15129710.
  14. ↑ Applegate, K. E.; Amis Jr, E. S.; Schauer, D. A. (3 December 2009). "Radiation Exposure from Medical Imaging Procedures". New England Journal of Medicine. 361 (23): 2289–2292. doi:10.1056/NEJMc0909579. PMID   19955531.
  15. ↑ "Myocardial perfusion scintigraphy for the diagnosis and management of angina and myocardial infarction". NICE. Retrieved 14 December 2017.
  16. ↑ Shaw, L (April 2004). "Prognostic value of gated myocardial perfusion SPECT". Journal of Nuclear Cardiology. 11 (2): 171–185. doi:10.1016/j.nuclcard.2003.12.004. PMID   15052249. S2CID   31369868.
  17. 1 2 Berrington de Gonzalez, A.; Kim, K.-P.; Smith-Bindman, R.; McAreavey, D. (22 November 2010). "Myocardial Perfusion Scans: Projected Population Cancer Risks From Current Levels of Use in the United States". Circulation. 122 (23): 2403–2410. doi:10.1161/CIRCULATIONAHA.110.941625. PMC   3548424 . PMID   21098448.
  18. ↑ "Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and use of sealed Radioactive Sources" (pdf). Department of Health. Public Health England. 22 February 2017.
  19. ↑ A revised effective dose estimate for the PET perfusion tracer Rb-82, deKemp et al, J NUCL MED MEETING ABSTRACTS, 2008. 49(MeetingAbstracts_1): p. 183P-b-.
  20. ↑ Radiopharmaceuticals for nuclear cardiology: radiation dosimetry, uncertainties, and risk., Stabin et al, J Nucl Med, 2008. 49(9): p. 1555-63.
  21. ↑ Stress-only Nuclear Myocardial Perfusion Imaging [ permanent dead link ], Heston TF, Internet Med J, accessed 17-Feb-2012.
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