John David Spence

Last updated
John David Spence
Born (1944-11-10) November 10, 1944 (age 80)
Peru, Talara
NationalityCanadian
Occupation(s)Neurologist, Internist and Clinical Pharmacologist
Known forFather of carotid plaque measurement

John David Spence CM [1] (born November 10, 1944) is a Canadian medical doctor, medical researcher and Professor Emeritus at the University of Western Ontario. He is affiliated with the University of Western Ontario (where he taught Clinical Neurological Science) and the Robarts Research Institute, one of Canada's leading medical research organizations. Before his retirement from clinical practice in July 2022, he was also affiliated with the London Health Sciences Centre's University Hospital (where he set up and ran stroke prevention clinics). He is a recognized expert in stroke prevention and stroke prevention research, with more than 600 peer-reviewed publications since 1970. He delivered more than 600 lectures on stroke prevention in 42 countries. In 2015, he received the Research Excellence Award from the Canadian Society for Atherosclerosis, Thrombosis and Vascular Biology Archived 2016-10-05 at the Wayback Machine . In 2019, he was appointed a Member of the Order of Canada, and in 2020 he received the William Feinberg Award from the American Heart Association for excellence in clinical stroke research.

Contents

Dr. Spence is the director of the Stroke Prevention & Atherosclerosis Research Centre (SPARC), a unit of the Robarts Research Institute. With Maria Dicicco, RVT, he pioneered the measurement of total plaque area (TPA) in a patient's carotid artery using ultrasound technology. The ability to measure TPA gives doctors the ability to treat, and measure the change in, the amount of plaque in a patient's arteries and has given researchers the ability to measure the effectiveness of new drug treatment therapies for stroke prevention. [2] in high-risk patients with narrowing of the carotid arteries, the process of "Treating Arteries" was associated with a >80% reduction in the 2-year risk of strokes and heart attacks. [3] Dr. Spence is recognized as "The Father of Total Plaque Area Measurement" and the importance of TPA measurement is that, in Dr Spence's words, "We can now treat arteries instead of just treating risk factors".

Spence - Key Research Discoveries

Cerebral consequences of hypertension: treating high blood pressure prevents only arteriolar strokes. (. [4] ) This research led to the understanding that the effects of therapies, designed to reduce hypertension, on blood pressure need to be distinguished from other effects on atherosclerosis.

Effects of antihypertensive drugs on blood velocity and arterial flow disturbances 1976, 1980, 1995: these studies showed that antihypertensive drugs have different effects on blood velocity and arterial flow disturbances, which have implications for how effective they are at fighting the buildup of arterial plaque. (. [5] )

Effects of grapefruit juice on drug metabolism: The discovery with Drs. David Bailey and Malcolm Arnold, that grapefruit juice markedly increases blood levels of a number of drugs that have low bioavailability because of gut wall first-pass metabolism by CYP3A4 made a major contribution to the understanding of pharmacokinetics, and has opened up a new field of pharmacology. ( [6] ).

Ultrasound measurement of plaque: Beginning in 1990, Dr. Spence pioneered the use of carotid plaque measurement (as opposed to intima-media thickness) for research and for management of patients with carotid artery disease. (. [2] ). This has evolved to the use of 3-D plaque volume measurements for evaluation of new therapies. The effect of drug therapies on carotid plaque volume can now be evaluated in a very cost-effective way.

Development of quantitative traits for human atherosclerosis: Spence developed a number of quantitative traits that will advance the search for new genetic causes of atherosclerosis, and thus new therapeutic targets and new therapies for atherosclerosis. These are unexplained atherosclerosis and its progression, unexplained protection from atherosclerosis and unexplained regression of atherosclerosis. (;. [7] [8] [9] [10] [11] )

Appropriate carotid endarterectomy: Showed in 2005 ( [12] ) that with intensive medical therapy most patients with asymptomatic carotid stenosis cannot benefit from endarterectomy or stenting, and that the very small proportion (10%) who may benefit can be identified by microembolus detection on transcranial Doppler. Showed in 2010 ( [13] ) that the proportion who could benefit had declined with more intensive therapy to less than 5%. SPARC's work was confirmed in 2010 by an international multicenter study, the ACES study. Dr. Spence led a study in the Canadian Atherosclerosis Imaging Network Archived 2011-06-26 at the Wayback Machine , on histological validation of imaging features of vulnerable plaque that will also serve to identify high-risk carotid plaques.

Physiologically individualized therapy for resistant hypertension. Reported in 2017 that in patients in three hypertension clinics in Africa, measuring plasma renin activity and aldosterone markedly improved blood pressure control, but permitting selection of the treatment that is appropriate to that patient, by identifying the physiological cause of the hypertension. [14]

Effects of the intestinal microbiome on atherosclerosis He reported with colleagues in 2018 that patients with carotid atherosclerosis not explained by traditional risk factors had higher blood levels of toxic metabolites produced by intestinal bacteria from foods such as red meat and egg yolk. [15] His group also found that blood levels of those toxic products are elevated with even moderate impairment of kidney function, such as seen in elderly patients. [16] This has important implications for diet, and offers the possibility of an entirely new way of treating atherosclerosis: repopulation of the intestinal microbiome.

Special Projects

  1. Member of the "Joint Stroke Working Group" set up by the Ministry of Health and the Heart and Stroke Foundation.
  2. Member of the Shape Task Force II which is recognized in the U.S. Centers of Excellence program in their work for heart attack prevention and eradication.
  3. National stroke prevention program of the Argentina health organization training Argentinean physicians in vascular prevention.

Education and Training

  1. Ridley College.
  2. M.D. University of Western Ontario.
  3. Clinical Pharmacology training at the Cardiovascular Research Institute of the University of California at San Francisco.
  4. M.B.A. from the University of Toronto.
  5. Trained with Henry J. M. Barnett at University Hospital in London Ontario. Dr. Barnett is a leading stroke researcher who pioneered the use of aspirin in stroke prevention therapy.

Personal life

Spence is the great-grandson of David Spence (Canadian Politician) and trained with Henry J. M. Barnett

Related Research Articles

<span class="mw-page-title-main">Cardiology</span> Branch of medicine dealing with the heart

Cardiology is the study of the heart. 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 disease, and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a sub-specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.

A transient ischemic attack (TIA), commonly known as a mini-stroke, is a temporary (transient) stroke with noticeable symptoms that end within 24 hours. A TIA causes the same symptoms associated with a stroke, such as weakness or numbness on one side of the body, sudden dimming or loss of vision, difficulty speaking or understanding language or slurred speech.

<span class="mw-page-title-main">Atherosclerosis</span> Inflammatory disease involving buildup of lesions in the walls of arteries

Atherosclerosis is a pattern of the disease arteriosclerosis, characterized by development of abnormalities called lesions in walls of arteries. This is a chronic inflammatory disease involving many different cell types, and driven by elevated levels of cholesterol in the blood. These lesions may lead to narrowing of the arterial walls due to buildup of atheromatous plaques. At onset there are usually no symptoms, but if they develop, symptoms generally begin around middle age. In severe cases, it can result in coronary artery disease, stroke, peripheral artery disease, or kidney disorders, depending on which body part(s) the affected arteries are located in the body.

<span class="mw-page-title-main">Peripheral artery disease</span> Abnormal narrowing of arteries other than those that supply the heart or brain

Peripheral artery disease (PAD) is a vascular disorder that causes abnormal narrowing of arteries other than those that supply the heart or brain. PAD can happen in any blood vessel, but it is more common in the legs than the arms.

<span class="mw-page-title-main">Stroke</span> Death of a region of brain cells due to poor blood flow

Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functioning properly.

<span class="mw-page-title-main">Atheroma</span> Accumulation of degenerative material in the inner layer of artery walls

An atheroma, or atheromatous plaque, is an abnormal accumulation of material in the inner layer of an arterial wall.

Intravascular ultrasound (IVUS) or intravascular echocardiography is a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter. The proximal end of the catheter is attached to computerized ultrasound equipment. It allows the application of ultrasound technology, such as piezoelectric transducer or CMUT, to see from inside blood vessels out through the surrounding blood column, visualizing the endothelium of blood vessels.

<span class="mw-page-title-main">Endarterectomy</span> Surgical removal of plaque within arteries

Endarterectomy is a surgical procedure to remove the atheromatous plaque material, or blockage, in the lining of an artery constricted by the buildup of deposits. It is carried out by separating the plaque from the arterial wall.

<span class="mw-page-title-main">Carotid endarterectomy</span> Surgical procedure

Carotid endarterectomy is a surgical procedure used to reduce the risk of stroke from carotid artery stenosis. In endarterectomy, the surgeon opens the artery and removes the plaque. The plaque forms and thickens the inner layer of the artery, or intima, hence the name of the procedure which simply means removal of part of the internal layers of the artery.

<span class="mw-page-title-main">Carotid artery stenosis</span> Narrowing of the carotid arteries

Carotid artery stenosis is a narrowing or constriction of any part of the carotid arteries, usually caused by atherosclerosis.

<span class="mw-page-title-main">Cerebral infarction</span> Stroke resulting from lack of blood flow

Cerebral infarction, also known as an ischemic stroke, is the pathologic process that results in an area of necrotic tissue in the brain. In mid to high income countries, a stroke is the main reason for disability among people and the 2nd cause of death. It is caused by disrupted blood supply (ischemia) and restricted oxygen supply (hypoxia). This is most commonly due to a thrombotic occlusion, or an embolic occlusion of major vessels which leads to a cerebral infarct. In response to ischemia, the brain degenerates by the process of liquefactive necrosis.

Vertebrobasilar insufficiency (VBI) describes a temporary set of symptoms due to decreased blood flow (ischemia) in the posterior circulation of the brain. The posterior circulation supplies the medulla, pons, midbrain, cerebellum and supplies the posterior cerebellar artery to the thalamus and occipital cortex. As a result, symptoms vary widely depending which brain region is predominantly affected.

<span class="mw-page-title-main">Watershed stroke</span> Medical condition

A watershed stroke is defined as a brain ischemia that is localized to the vulnerable border zones between the tissues supplied by the anterior, posterior and middle cerebral arteries. The actual blood stream blockage/restriction site can be located far away from the infarcts. Watershed locations are those border-zone regions in the brain supplied by the major cerebral arteries where blood supply is decreased. Watershed strokes are a concern because they comprise approximately 10% of all ischemic stroke cases. The watershed zones themselves are particularly susceptible to infarction from global ischemia as the distal nature of the vasculature predisposes these areas to be most sensitive to profound hypoperfusion.

<span class="mw-page-title-main">Fibromuscular dysplasia</span> Human arterial disease

Fibromuscular dysplasia (FMD) is a non-atherosclerotic, non-inflammatory disease of the blood vessels that causes abnormal growth within the wall of an artery. FMD has been found in nearly every arterial bed in the body, although the most commonly affected are the renal and carotid arteries.

<span class="mw-page-title-main">Hollenhorst plaque</span> Medical condition

A Hollenhorst plaque is a cholesterol embolus that is seen in a blood vessel of the retina. It is usually found when a physician performs ophthalmoscopy, during which a plaque will appear as a small, bright crystal that is refractile and yellow. This is a medical exam finding, and is not a medical condition, though it may be related to cardiovascular conditions such as atherosclerosis of the internal carotid artery. It was first described by American ophthalmologist Robert Hollenhorst in 1961.

Arterial stiffness occurs as a consequence of biological aging and arteriosclerosis. Inflammation plays a major role in arteriosclerosis development, and consequently it is a major contributor in large arteries stiffening. Increased arterial stiffness is associated with an increased risk of cardiovascular events such as myocardial infarction, hypertension, heart failure, and stroke, two of the leading causes of death in the developed world. The World Health Organization predicts that in 2010, cardiovascular disease will also be the leading killer in the developing world and represents a major global health problem.

<span class="mw-page-title-main">Intima–media thickness</span>

Intima–media thickness (IMT), also called intimal medial thickness, is a measurement of the thickness of tunica intima and tunica media, the innermost two layers of the wall of an artery. The measurement is usually made by external ultrasound and occasionally by internal, invasive ultrasound catheters. Measurements of the total wall thickness of blood vessels can also be done using other imaging modalities.

<span class="mw-page-title-main">Carotid ultrasonography</span> Ultrasound-based diagnostic imaging technique

Carotid ultrasonography is an ultrasound-based diagnostic imaging technique to evaluate structural details of the carotid arteries. Carotid ultrasound is used to diagnose carotid artery stenosis (CAS) and can assess atherosclerotic plaque morphology and characteristics. Carotid duplex and contrast-enhanced ultrasound are two of the most common imaging techniques used to evaluate carotid artery disease.

Embolic stroke of undetermined source (ESUS) is an embolic stroke, a type of ischemic stroke, with an unknown origin, defined as a non-lacunar brain infarct without proximal arterial stenosis or cardioembolic sources. As such, it forms a subset of cryptogenic stroke, which is part of the TOAST-classification. The following diagnostic criteria define an ESUS:

The BaleDoneen Method is a risk assessment and treatment protocol aimed at preventing heart attack and stroke. The method also seeks to prevent or reduce the effects of type 2 diabetes. The method was developed by Bradley Field Bale and Amy Doneen.

References

  1. ↑ "Order of Canada appointees - May 2022". 29 April 2022.
  2. 1 2 Spence, J. David; Eliasziw, Michael; DiCicco, Maria; Hackam, Daniel G.; Galil, Ramzy; Lohmann, Tara (December 2002). "Carotid Plaque Area". Stroke. 33 (12): 2916–2922. doi: 10.1161/01.str.0000042207.16156.b9 . PMID   12468791. S2CID   2028909.
  3. ↑ Spence, J. David; Coates, Victoria; Li, Hector; Tamayo, Arturo; Muñoz, Claudio; Hackam, Daniel G.; DiCicco, Maria; DesRoches, Janine; Bogiatzi, Chrysi; Klein, Jonathan; Madrenas, Joaquim (February 2010). "Effects of intensive medical therapy on microemboli and cardiovascular risk in asymptomatic carotid stenosis". Archives of Neurology. 67 (2): 180–186. doi:10.1001/archneurol.2009.289. PMID   20008646.
  4. ↑ Spence, J D (September 1986). "Antihypertensive drugs and prevention of atherosclerotic stroke". Stroke. 17 (5): 808–810. doi: 10.1161/01.str.17.5.808 . PMID   3764950.
  5. ↑ Steinman, David A.; Thomas, Jonathan B.; Ladak, Hanif M.; Milner, Jaques S.; Rutt, Brian K.; Spence, J. David (January 2002). "Reconstruction of carotid bifurcation hemodynamics and wall thickness using computational fluid dynamics and MRI". Magnetic Resonance in Medicine. 47 (1): 149–159. doi: 10.1002/mrm.10025 . PMID   11754454. S2CID   15980836.
  6. ↑ Bailey, D. G.; Spence, J. D.; Munoz, C.; Arnold, J. M. (1991-02-02). "Interaction of citrus juices with felodipine and nifedipine". Lancet. 337 (8736): 268–269. doi:10.1016/0140-6736(91)90872-m. PMID   1671113. S2CID   37137655.
  7. ↑ Spence, J. D.; Malinow, M. R.; Barnett, P. A.; Marian, A. J.; Freeman, D.; Hegele, R. A. (May 1999). "Plasma homocyst(e)ine concentration, but not MTHFR genotype, is associated with variation in carotid plaque area". Stroke. 30 (5): 969–973. doi: 10.1161/01.str.30.5.969 . PMID   10229729. S2CID   11062637.
  8. ↑ Spence, J. D.; Barnett, P. A.; Bulman, D. E.; Hegele, R. A. (1999). "An approach to ascertain probands with a non-traditional risk factor for carotid atherosclerosis". Atherosclerosis. 144 (2): 429–340. doi:10.1016/S0021-9150(99)00003-9. PMID   10407504.
  9. ↑ Stroke. 34: 1178–1182. 2003.{{cite journal}}: Missing or empty |title= (help)
  10. ↑ Spence, J. David (November 2006). "Technology Insight: ultrasound measurement of carotid plaque--patient management, genetic research, and therapy evaluation". Nature Clinical Practice. Neurology. 2 (11): 611–619. doi:10.1038/ncpneuro0324. PMID   17057748. S2CID   26077254.
  11. ↑ Lanktree, Matthew B.; Hegele, Robert A.; Schork, Nicholas J.; Spence, J. David (April 2010). "Extremes of unexplained variation as a phenotype: an efficient approach for genome-wide association studies of cardiovascular disease". Circulation: Cardiovascular Genetics. 3 (2): 215–221. doi:10.1161/CIRCGENETICS.109.934505. PMC   3084495 . PMID   20407100.
  12. ↑ Spence, J. David; Tamayo, Arturo; Lownie, Stephen P.; Ng, Wai P.; Ferguson, Gary G. (November 2005). "Absence of microemboli on transcranial Doppler identifies low-risk patients with asymptomatic carotid stenosis". Stroke. 36 (11): 2373–2378. doi: 10.1161/01.STR.0000185922.49809.46 . PMID   16224084. S2CID   14634533.
  13. ↑ Spence, J. David; Coates, Victoria; Li, Hector; Tamayo, Arturo; Muñoz, Claudio; Hackam, Daniel G.; DiCicco, Maria; DesRoches, Janine; Bogiatzi, Chrysi; Klein, Jonathan; Madrenas, Joaquim (February 2010). "Effects of intensive medical therapy on microemboli and cardiovascular risk in asymptomatic carotid stenosis". Archives of Neurology. 67 (2): 180–186. doi:10.1001/archneurol.2009.289. PMID   20008646.
  14. ↑ Akintunde, Adeseye; Nondi, Justus; Gogo, Kennedy; Jones, Erika S. W.; Rayner, Brian L.; Hackam, Daniel G.; Spence, J. David (2017-09-01). "Physiological Phenotyping for Personalized Therapy of Uncontrolled Hypertension in Africa". American Journal of Hypertension. 30 (9): 923–930. doi: 10.1093/ajh/hpx066 . PMID   28472315.
  15. ↑ Pignanelli, Michael; Just, Caroline; Bogiatzi, Chrysi; Dinculescu, Vincent; Gloor, Gregory B.; Allen-Vercoe, Emma; Reid, Gregor; Urquhart, Bradley L.; Ruetz, Kelsey N.; Velenosi, Thomas J.; Spence, J. David (2018-06-16). "Mediterranean Diet Score: Associations with Metabolic Products of the Intestinal Microbiome, Carotid Plaque Burden, and Renal Function". Nutrients. 10 (6): E779. doi: 10.3390/nu10060779 . PMC   6024790 . PMID   29914158.
  16. ↑ Pignanelli, Michael; Bogiatzi, Chrysi; Gloor, Gregory; Allen-Vercoe, Emma; Reid, Gregor; Urquhart, Bradley L.; Ruetz, Kelsey N.; Velenosi, Thomas J.; Spence, J. David (January 2019). "Moderate Renal Impairment and Toxic Metabolites Produced by the Intestinal Microbiome: Dietary Implications". Journal of Renal Nutrition. 29 (1): 55–64. doi:10.1053/j.jrn.2018.05.007. PMID   30100156. S2CID   51969228.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.