[038] Coronary Circulation and Conducting System of Heart
What is chronic coronary artery disease?
Gradual narrowing of vessels
What nerve innervates the pericardium?
Phrenic nerve
What is acute coronary artery disease?
Plaque breaks away and obstructs vessel —> Myocardial infarction
What is a coronary artery bypass?
Surgical graft using donor internal thoracic artery or great saphenous vein to restore blood flow to heart
What makes up the sinoatrial node? (3 features)
1. Nodal tissue 2. Specialised cardiac muscle fibers 3. Connective tissues
What is angina?
1. Sudden crushing substernal pain 2. Myocardial ischaemia caused by narrowing of coronary arteries
What are the coronary arteries? (2 features)
1. Suplies myocardium and epicardium 2. Right and left coronary arteries arise from ascending aorta base just after the aortic valve
What is the lateral anterior descending (LAD) branch of the coronary artery?
Anterior interventricular branch of left coronary artery in anterior interventricular sulcus
Where is the sinoatrial node located?
Anterolaterally just deep to epicardium at junction of SVC and right atrium
Where is the cardiac plexus located?
Between aorta and pulmonary trunk and trachea
What is the pericardium sensitive to?
Pain and temperature
What is coronary artery disease?
Disease that leads to ischaemia of myocardium
What are the anterior cardiac veins?
Drain directly into right atrium on anterior side close to right atrium
What are the coronary veins?
Drain into coronary sinus which drains directly into right atrium
What is the function of an artificial pacemaker?
Electrode passed through SVC to right atrium and through tricuspid valve into right ventricle —> Placed in contact with endocardium —> Initiates ventricular contractions at a predetermined rate —> Treat slow or irregular heart rate
What are the 4 key coronary veins?
Great cardiac vein Middle cardiac vein Small cardiac vein Anterior cardiac veins
What are the 3 cardiac veins that drain into the coronary sinus?
Great, middle and small cardiac veins
What triggers angina?
Heavy meals, stress, cold
Why is anginal pain felt in left arm?
Intercostal nerves that innervate coronary arteries and myocardium also innervate left pectoral region —> Medial cutaneous nerve of arm shares spinal cord segments with those nerves —> Ischaemic pain in heart —> Felt in left arm and left pectoral region
Describe the flow of electrical signals in the right bundle
Interventricular septum muscle —> Septomarginal trabecula (moderator band) —> Anterior papillary muscle —> Right ventricle wall
Describe the flow of electrical signals in the left bundle
Interventricular septum muscle —> anterior and posterior papillary muscles —> Wall of left ventricle
What is atherosclerosis?
Lipid buildup narrowing lumen of an artery
What is the great cardiac vein?
Located in anterior interventricular sulcus goes up and wraps around to back of heart
What is ischaemia?
Loss of blood supply to a tissue due to impeded arterial supply.
Where is the AV node located?
Posteroinferior region of interatrial septum near opening of coronary sinus
What makes up the sympathetic components of the cardiac plexus?
Postsynaptic fibers from superior thoracic paravertebral ganglia of sympathetic trunks
What is the middle cardiac vein?
Provides collateral circulation for anterior and posterior interventricular groove wrapping up and around back
What relieves angina?
Rest
Describe the flow of electrical signals in the heart
SA node generates signal —> Cardiac muscle in walls of right atrium —> AV Node —> AV bundle —> Right and left bundles
What is the only pain the heart itself is sensitive to?
Stimulation of pain endings in myocardium by ischaemia
Where is anginal pain felt?
Substernal and left pectoral regions to left shoulder and left arm
What is the small cardiac vein?
Supplies inferior margin of heart
What is the function of the cardiac plexus?
Supplies innervation to heart
What is the effect of sympathetic and parasympathetic stimulation from the cardiac plexus on the heart?
Sympathetic speeds up conduction of electrical signals Parasympathetic slows it down
What is visceral referred pain?
Transmitted visceral afferent fibers accompany sympathetic fibers —> Pain felt in structures that have afferent fibers with cell bodies in same spinal ganglion
What makes up the parasympathetic components of the cardiac plexus?
Vagus nerves
What is a heart attack?
When straining heart muscle demands more oxygen than the stenotic arteries can provide —> Ischaemic area of myocardium undergoes infarction
What is infarction?
tissue death
