Cardiovascular Flashcards
Main structural components of the circulatory/cardiovascular system
- heart - peripheral vascular system - haematological system (blood and components)
Function of the circulatory / cardiovascular system
- delivers oxygen, nutrients and other requirements to the cell - removes and transports waste eg carbon dioxide to be excreted
Three types of circulation
- pulmonary (to/from the lungs) - systemic (to/from the body tissues) - coronary (supplying blood to the heart tissue)
What is the main influence on coronary circulation flow
the pressure in the aorta
Valves within the heart
- atrioventricular valves (open when ventricles are relaxed) * tricuspid valve * mitral valve - semilunar valves (open when ventricles are contracting) * pulmonary semilunar valve * aortic semilunar valve
Layers of the blood vessel from inside out
- Lumen - Tunica intima (simple squamous epithelial cells) - Tunica media - Tinuca adventitia
Differences between the structure of veins and arteries
- Veins lumens are wider - Arteriers tunica media is wider - Veins have valves - arteries closer to the heart have more elastic fibres i the tunica media - veins have more smooth muscle to assist in returning blood to the heart against gravity - some capilliaries (eg those in the lungs) are only 1 epithelial cell wide
Blood flow resistance is impacted by:
- vessel length - vessel diameter - blood viscosity - blood turbulence
3 main components of blood
- erythrocytes (red blood cells) - leukocytes (white blood cells) - thrombocytes (platelets)
The 4 stations of the conductive pathway of the heart
- SA node (aka pacemaker) - located in the right atria and starts the spark - AV node - located on the back wall of the heart between the right atria and right ventricle - Bundle of HIS - located in the septum - the Pirjinke Fibres - spread the electrical charge throughout the myocardium
Blood flow through the entire circulatory system
Right atrium > right AV valve > right ventricle > pulmonary SL valve > pulmonary artery > arterioles > capillaries > venuoles > veins > pulmonary vein > left atrium > left AV valve > left ventricle > aortic SL valve > aorta > arteries > arterioles > capillaries > venuoles > veins > vena cava > right atrium
Layers of the heart wall from outside in
- pericardium (serous pericardium, aka epicardium) * parietal layer * visceral layer - myocardium - endocardium
What is the serious pericardium and what does it do?
- double walled membranous sac - protects the heart from infection and inflammation - anchors the heart in place - contains nociceptors and mechanoceptors which cause changes in blood pressure and heart rate - the parietal and visceral layers are separated by the fluid-filled pericardial cavity which lubricates and reduces friction as the heart beats
Heart sounds
S1 - occurs when the atrioventricular valves close, during ventricular contraction S2 - occurs when the semilunar valves close, ventricular relaxation
Where is it easiest to hear each of the valves?
• aortic valve: second intercostal space on the right-hand side of the sternum • pulmonary valve: second intercostal space on the left-hand side of the sternum • tricuspid valve: fourth intercostal space on the left-hand side of the sternum • mitral valve: fifth intercostal space in the midclavicular line (apex)
What are diastole and systole?
- diastole - relaxation, blood fills the ventricles - systole - contraction, propels blood from the ventricles
What is the cardiac cycle?
- atrial systole 2. isovolumetric ventricular contraction 3. ejection 4. isovolumetric ventricular relaxation 5 passive ventricular filling
Main branches of the coronary arteries
- left coronary artery - left anterior descending artery (aka anterior interventricular artery) - circumflex artery - right coronary artery
What is angiogenesis?
growth of new blood vessels
What are the 5 key phases to the cardiac action potential?
0 depolarisation 1 early rapid repolarisation 2 plateau phase 3 final rapid repolarisation 4 resting membrane phase
What do the different sections of an ECG show?
- P wave - right and left atrial depolarisation - PR interval - time from the onset of atrial activation to the onset of ventricular activation (~0.12 to 0.2 seconds) - QRS complex - ventricular depolarisation - ST segment - ventricular myocardium is depolarised, ventricles are contracting - QT interval - electrical systole of the ventricles - T wave - ventricular repolarisation - TP segment - ventricular relaxation and filling
What is cardiovascular disease?
Disorders of the heart and blood vessels.
What is coronary heart disease (aka ischemic heart disease, coronary artery disease, heart disease)?
Disorders of the coronary arteries, eg. angina, myocardial infarction
What is arteriosclerosis?
chronic abnormal thickening and hardening of artery walls
What is atherosclerosis?
A form of arteriosclerosis, with soft deposits of intra-arterial fat and other variations depending on the severity of the inflammatory condition - the main cause of coronary heart disease
Clinical manifestations of atherosclerosis
- maybe none - transient ischaemic events (stable angina - infarction with manifestations - peripheral artery obstruction leading to pain, neurovascular changes, disability
Risk factors for coronary artery disease
- higher age - male or postmenopausal female - family history - dyslipidaema and atherosclerosis-promoting diet - hypertension - smoking - diabetes mellitus and insulin resistance - obesity - sedentary lifestyle - inflammatory factors
What is metabolic syndrome (syndrome x)
- abdominal obesity, insulin resistance,
Pathophysiology of coronary heart disease
- narrowing of a major coronary artery by > 50%, leading to ischaemia, especially during exercise - commonly from atherosclerosis - can also be from (less commonly) spasm, hypotension, arrhythmias, anaemia)
Causes of cardiovascular cardiac-type pain
- myocardial ischaemia - myocardial infarction - pericarditis - heart valve disorders - cancer - sickle cell occlusion
Causes of non-cardiovascular cardiac type pain (chest pain)
- dissecting aortic aneurysm - herpes zoster (shingles) - oesophageal reflux / spasm - pneumonia - pneumothorax - pleurisy - peptic ulceration - gallbladder disease - musculoskeletal / costochondral - pulmonary embolism
Clinical manifestations of stable angina pectoris
- 3 - 5 minutes with no permanent damage - usually substernal, from heaviness or pressure to severe pain - may radiate to neck, lower jaw, left arm, left shoulder, occasionally to back or down right arm - likely due to lactic acid or abnormal stretching of myocardial nerve fibres - pallor or diaphoresis - dyspnoea, nausea and vomiting - Prinzmetal’s angina from coronary artery spasm is unpredictable, maybe at rest - silent ischaemia is mainly in older adults with vague symptoms of fatigue, mild dyspnoea, a feeling of unease
Clinical manifestations of unstable angina
- pain occurs at rest and is increasing in severity / frequency - pain increasing with coronary artery spasm or unstable plaque / thrombus blockage - pain lasts 10mins or longer and radiates to neck and/or left shoulder/arm
What is myocardial infarction?
- when ischaemia becomes infarction - irreversible cell death and tissue necrosis - numerous electrolyte and chemical changes - two types: subendocardial MI, where thrombus break up before distal necrosis occurs (usually non-STEMI) and transmural MI where the thrombus remain and distal necrosis occurs (usually STEMI, “full thickness” infarction, results in severe cardiac dysfunction if survived.
What is “good” cholesterol?
- High density lipoproteins - transport excess cholesterol away from tissues and back to the liver for metabolism
What is “bad” cholesterol?
- low density lipoproteins - transport cholesterol from the liver to the tissues and organs where it is used to build plasma membranes - contributes significantly to plaque deposits and coronary artery disease
Indications of different lipid-lowering drugs
- to lower LDL-C (hypercholesterolaemia) - to lower triglyceride (hypertriglyceridaemia) - both (hyperlipidaemia)
Drug types to lower hypercholesterolaemia
- statins - bile acid-binding resin - nicotinic acid - ezetimibe - fibrate
Drug types to lower hypertriglyceridaemia
- fibrate - fish oil - nicotinic acid
Drug types to lower mixed hyperlipidaemia
- guided by predominant disorder including: - statins - fibrate - nicotinic acid
Statins care considerations
- administer at bedtime - child-bearing-age women should use condoms to avoid pregnancy - multiple drug interactions including some antbioltics and antihypertensives - avoid grapefruit juice which alters metabolism of the drug - regular ophthalmic examinations as can increase risk of cataracts
In relation to the specialised properties of the conduction cells of the heart cells, what is automaticity?
inherent ability to spontaneously initiate an electrical impulse -normally only by pacemaker cells - affected by potassium and calcium levels
In relation to the specialised properties of the conduction cells of the heart cells, what is conductivity?
- ability of a cell to transmit an action potential along its membrane - all cardiac muscle tissue - affected by potassium and calcium levels
In relation to the specialised properties of the conduction cells of the heart cells, what is refractoriness?
- tissue is un-responsive to stimulation during initial phase of contraction, allowing for regular contraction and relaxation
How is cardiac output (CO) determined
CO = stroke volume (SV) x heart rate (HR)
What is stroke volume regulated by:
- preload - degree of stretch of heart fibres before contraction - afterload - force ventricles must overcome to eject their blood volume - contractility - inherent capability of the cardiac muscle fibres to shorten
Main drug types affecting cardiac function
- positive inotrophic (eg adrenaline, dobutamine) - increase force of myocardial contraction - negative inotrophic (eg propanolol) - decreases force of myocardial contraction - positive chronotrophic (eg adrenaline) - accelerate heart rate by increase rate of impulse formation in SA node - Negative Chronotropic (eg digoxin) - slows HR down by decreasing impulse formation = Positive Dromotropic (eg phenytoin) - increase conduction velocity through specialised conducting tissues Negative Dromotopic (verapamil) delays conduction velocity through specialised conducting tissues
What is digoxin?
- Cardiac glycoside - Mechanisms of action: - Inhibits active transport of Na⁺ and K⁺ across myocardial cell membrane by interrupting the Na⁺- K⁺ pump - Alters the electrophysiological properties of cardiac tissue – decreases automaticity and increases resting membrane potential of atrial tissue and AV node. - Effects on the heart: - Increased contractile force - Decreased conduction through AV node - Decreased heart rate - Stabilises rhythm disturbances
Indications and pharmacokinetics of digoxin
- Cardiac arrhythmias - Atrial fibrillation - Atrial flutter - Paroxysmal atrial tachycardia - Heart Failure - Available in oral or parenteral form - Rapid onset of action and rapid absorption - 30-120mins orally and 5-30mins IV - Primarily excreted unchanged in urine (don’t prescribe for patients with renal disease)
Potential adverse reactions of digoxin?
- GI disturbances – Nausea and vomiting, diarrhoea - CNS effects – visual disturbances, confusion, nightmares, agitation and drowsiness - Cardiac arrhythmias (with digitalis toxicity) -premature ventricular beats, AV block disorders, ventricular arrhythmias