Clinical Anatomy: Clinical Pathologies of the Heart from Medready.org

Clinical Anatomy: Clinical Pathologies of the Heart

Lecture 12: Clinical Pathologies of the Heart · Dr. Karyn Lumsden BSc, M.Ed., DC · Assistant Professor · Karyn.Lumsden@medready.org Practice Questions are posted on Canvas

Learning Objectives: Fetal Heart Development and Pathologies

1. Describe the embryological development of the fetal heart and blood circulation
2. Compare fetal heart/blood circulation to that after birth
3. Identify embryological remnants observed on adult heart tissue
4. Describe atrial and ventricular septal defects, including pathogenesis, symptoms, and diagnosis
5. Describe the process of arteriosclerosis and how this condition can lead to myocardial infarction
6. Describe the process of referred pain
7. Identify and describe the pathophysiology and symptoms of valvular heart diseases
8. Identify the risk factors and symptoms of abdominal aortic aneurysm (AAA)

Clinical Correlation: Arteriosclerosis and Infarction

Angina - chest pain caused by restricted blood flow to heart. Not a condition, rather a symptom of underlying heart issue.

Myocardial infarction (MI) - heart attack

• Thrombus formed in coronary circulation or embolus from another location
• Resulting in ischemia and finally infarction of myocardial tissue

· Infarction is local death of an organ or tissue Coronary artery disease Plaque builds up in an artery Angina It is harder for blood to get through the artery Heart attack Plaque cracks and a blood clot blocks the artery Myocardial Infarction anterior wall infarct Red thrombus on a ruptured atherosclerotic plaque, causing blood flow blockage

Clinical Correlation: Myocardial Infarction Epidemiology

Myocardial Infarction Risk Factors

Epidemiology /Risk factors:

• Age
• Males
• Cigarette smoking
• Hyperlipidemia

. Post menopausal females · Family history of atherosclerosis - genetic predisposition

Myocardial Infarction Pathogenesis and Symptoms

Pathogenesis (development of disease): . Occlusion of a coronary artery (any artery supplying the heart myocardium) . Ischemia can only be tolerated < 30 minutes, otherwise permanent myocyte death/damage Symptoms (physical indication of disease): . Chest pain - angina aggravated by exertion · Radiating/referred pain to left upper limb or jaw

Myocardial Infarction Diagnosis and Complications

Diagnosis:

• Cardiac markers in blood: Troponin levels elevated (peaks at 24 hours after MI)
• EKG - check electrical activity of heart
• Angiogram of coronary vessels and/or cardiac catheterization

• Most common MI involves left anterior descending artery - LAD (78% of cases )

• Complications:

• Ischemia of heart tissue can lead to damage of muscle and impact muscle function

• Arrhythmias - abnormal heart rhythm · Weakening of heart muscle · Congestive heart failure

Clinical Correlation: Coronary Artery Bypass Graft Surgery

Coronary artery disease is the narrowing of the coronary arteries (any artery that supplies heart muscle) Coronary bypass surgery: graft in one of your healthy blood vessels (often from the leg or chest) to bypass the blockage This will help redirect blood flow to heart tissue and prevent ischemia Graft = surgical procedure where tissue from one location is moved to another Typical choices

• Radial artery graft from arm

. Saphenous vein graft from leg -Internal mammary artery bypass Radial artery bypass Saphenous vein bypass Sites of blockage *ADAM.

Clinical Correlation: Angioplasty with Cardiac Stent

Procedure: Angioplasty uses a tiny balloon catheter that is inserted in a blocked blood vessel to help widen it and improve blood flow to the heart. Often combined with the placement of a small wire mesh tube called a stent. Cardiac stents are expandable wire mesh that helps to prop the artery open, decreasing chance of future narrowing

• Coated with medication to keep artery open and prevent clotting at the site

· Slow release of medication is also to prevent future plaque buildup and re-narrowing of blood vessels in that area . Stents are permanent and require ongoing medical support such as aspirin and blood thinners to prevent future complications A B C

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Clinical Correlation: Bypass vs Stent Outcomes

American College of Cardiology (March 2015)

• Patients who received bypass graft had better overall recovery outcomes compared to those treated with balloon angioplasty
• Patients treated with balloon angioplasty on average had a 47% higher risk of negative outcomes
• Supported guidelines that recommend treatment with bypass graft in clinical situations where patient presents with substantial narrowing of multiple coronary arteries (significant coronary artery disease)

. Most important artery is the LAD - blockage of the LAD is usually best treated with a bypass graft in order to ensure proper perfusion of the interventricular septum References:

• Casteel, B. (2015) Heart Bypass Surgery outperforms New Generation Stents. American College of Cardiology. URL: https://www.acc.org/about-acc/press-releases/2015/03/16/15/56/heart-bypass-surgery-outperforms-new-generation-stents

. https://www.health.harvard.edu/heart-health/bypass-or-angioplasty-with-stenting-how-do-you-choose

Clinical Correlation: Referred Pain

Referred pain - pain felt at a site other than where the actual injured or diseased organ

• Pain from internal organs is often referred to other sites on the skin
• When painful stimuli originate in visceral receptors, they travel to the spinal cord via the dorsal root (GVA fibers)

. Once in the spinal cord, the signals converge (meet) with GSA signals on a single ascending tract · Signals can travel to brain via spinothalamic tract To thalamus GSA Skin GVA Viscera (heart) Specific to Myocardial infarction: This phenomenon occurs at levels T1 - T5 in the spinal cord

Clinical Correlation: Convergence-Projection Theory of Referred Pain

. Most accepted explanation for referred pain . The referred pain is caused by a 'convergence' of afferent information of the visceral organs and those of somatic origin on the same segment of the spinal cord (GVA & GSA convergence) . This convergence causes hyperreactivity of the dorsal horn neurons · Signals travel/ascend via spinothalamic tract . The brain may incorrectly distinguish visceral signals from the more common somatic signals and transmit them as such Sensory pathway to brain GSA Dorsal root ganglion Spinal cord Pain receptor Sympathetic ganglion Skin GVA Heart Sensory nerve fiber Figure 7.17 Convergence of visceral and somatic afferent neurons onto ascending pathways produces the phenomenon of referred pain.

Clinical Correlation: Common Referred Pain Patterns

Esophagus Gallbladder, diaphragm Diaphragm Gallbladder Heart Stomach Liver, Gallbladder Gallbladder Pancreas Kidney Appendix Ureter Ovary Urinary bladder

Polling Question 1: Pain Signal Tracts

POLLING QUESTION 1: Which of the following tracts is responsible for carrying pain signals to the cortex? A B C -Pre-central gyrus D Ventral nuclel in thalamus Cerebral peduncle Midbrain Midbrain Cerebellum Medulla Modial lamniseus Nucleus gracilis and nucleus cuneatus Modula oblongata Spinocerebe tracts Decussation of pyramids Fasciculus cuneatus and fasciculus gracilis Spinal cord Posterior spinocerebel tract Anterior corticospinal trách Anterior spinothalamic tract Upper motor neuron To skeletal muscles Spinal cord Midbrain Pyramids Medulla oblongata Medulla oblongata Anterior spinocerebellar tract Lateral corticospinal tract Dorsal root ganglion PONS

Fetal Circulation Overview

Fetus receives all needed nutrition and oxygen from mom via the placenta Major connections of vasculature between mom (placenta) and baby : · Umbilical vein - Oxygen rich blood and nutrients from mom to baby · Two umbilical arteries - Oxygen poor blood and waste products from baby back to mom Placenta Foramen Ovale Lung Pulmonary Artery Ductus Venosus Lung Liver Left Kidney Umbilical Cord Umbilical Vein Oxygen-rich Blood Umbilical Arteries Oxygen-poor Blood Mixed Blood Ductus Arteriosus Aorta

Fetal Circulation: Shunts and Bypasses

· Fetal circulation uses 3 shunts to bypass the lungs & liver since these organs aren't fully functional until birth

1. Foramen ovale - shunt from R atria to L atria, bypassing lungs
2. Ductus arteriosus - shunt from pulmonary trunk to aorta, bypassing lungs
3. Ductus venosus - shunt allowing oxygenated blood from the placenta to bypass the liver before birth

2 1 3

Fetal Circulation Pathways

Returns blood back to placenta for reoxygenation PLACENTA Umbilical arteries Pulmonary trunk Umbilical vein Systemic circulation Right Ventricle LUNGS Ductus Arteriosus Î - Ductus venous BYPASSES LIVER BYPASSES LUNGS AORTA Pulmonary veins Inferior vena cava Right Atrium Foramen Ovale SIMULATES ADULT PATHWAY Left Atrium Left Ventricle BYPASSES LUNGS

Fetal Circulation Scheme

Pulmonary trunk Lungs Ductus arteriosus Right ventricle Pulmonary veins .7 Right atrium Foramen ovale Left atrium Left ventricle Aorta Inferior vena cava Systemic circulation Ductus venosus Liver Umbilical arteries Umbilical vein Placenta Scheme of fetal circulation

Polling Question 2: Fetal Blood Flow Structures

POLLING QUESTION 2: Which of the following embryological structures allows fetal blood to flow from the pulmonary trunk to the aorta?

• A. Foramen Ovale
• B. Umbilical vein
• C. Ductus arteriosus
• D. Umbilical arteries
• E. Ductus venosus

Changes to Fetal Shunts After Birth

With first breaths, L atrial pressure rises above that of R atrium, forcing the valve of foramen ovale closed (in adult, remnant is fossa ovalis) LEFT LEFT ATRIUM LEFT VENTRICLE RIGHT VENTRICLE WICKT VENTRICLE FORAMEN OVALE BEFORE BIRTH POST BIRTH Increase in oxygen concentration mediates closure of the ductus arteriosus; remnant becomes ligamentum arteriosum Before birth Immediately after birth Ductus arteriosus Foramen ovale The ductus arteriosus constricts, allowing all blood leaving the right ventricle to travel to the lungs via the pulmonary arteries. The foramen ovale closes, leaving a small depression called the fossa ovalis. This isolates deoxygenated and oxygenated blood within the heart. ATRIUM VENTRICLE

Ductus Venosus and Umbilical Vessels After Birth

Ductus venosus degenerates and becomes ligamentum venosum Before birth After birth Inferior vena cava The inferior vena cava now carries only deoxygenated blood back to the heart. Ductus venosus Blood arrives via umbilical vein Portal vein The ductus venosus degenerates and becomes the ligamentum venosum. Umbilical arteries Umbilical ligaments Goodbye, umbilical cord. Thanks for everything ... 0 3 0 Umbilical arteries and veins are no longer needed and remain as umbilical/peritoneal folds of the abdomen