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General Medicine

General Medicine. The Cardiovascular System. Anatomy of the Heart. Structure Separate pumps Left & right heart Deoxygenated & oxygenated blood flow Atrium & ventricles Major vessels & valves Coronary Circulation Left & right coronary arteries Left anterior descending (LAD)

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General Medicine

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  1. General Medicine The Cardiovascular System

  2. Anatomy of the Heart • Structure • Separate pumps • Left & right heart • Deoxygenated & oxygenated blood flow • Atrium & ventricles • Major vessels & valves • Coronary Circulation • Left & right coronary arteries • Left anterior descending (LAD) • Circumflex (CX) • Right coronary artery (RCA) • Nerve supply • Sympathetic nervous supply • Parasympathetic nervous supply • β1 & β2-adenoreceptors  inotropic & chronotropic effects • Muscarinic receptors (M2)

  3. Physiology of the Heart • Myocardial Contraction • Factors Influencing Cardiac Output • Factors Influencing Resistance to Systemic Blood Flow • Factors Influencing Resistance to Coronary Blood Flow • The Haemodynamic Effects of Respiration

  4. The Cardiac Cycle

  5. Investigations of Cardiovascular Disease

  6. Electrocardiography (ECG) • Non-invasive transthoracic graphic produced by an electrocardiograph, which records the electrical activity of the heart over time. • Uses: • Detect cardiac arrhythmias & conduction defects • Diagnosis & location of myocardial hypertrophy, ischaemia or infarction • Possible information on electrolyte imbalances & drug toxicity • Electrodes measure & amplify electrical activity of the heart. • The components of an ECG correspond to depolarisation & repolarisation according to the electrical conduction of the heart. • Electrodes on different sides of the heart measure the activity of different parts of the heart muscle. • An ECG displays the voltage between pairs of these electrodes, and the muscle activity that they measure, from different directions (vectors). • This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.

  7. Normal Electrical Conduction & ECG

  8. ECG Conventions & Intervals • Depolarisation towards electrode  positive deflection • Depolarisation away from electrode  negative deflection • Sensitivity  10mm = 1mV • Paperspeed  25mm per second • Square size • Large = 5mm = 0.2sec • Small = 1mm = 0.04sec • Heart rate • 1500/R-R interval (mm) • 300/number of large squares

  9. Standard 12-Lead ECG

  10. Limb Leads • Electrodes placed on all 4 limbs • Designated leads I, II and III  first three leads of the modern 12 lead ECG. • Leads are bipolar • Lead I  left arm minus right arm (0°) • the negative (white) electrode on the right arm • the positive (black) electrode on the left arm • Lead II  left leg minus right arm (60°) • the negative (white) electrode on the right arm • the positive (red) electrode on the left leg. • Lead III  left leg minus left arm (120°) • the negative (black) electrode on the left arm • the positive (red) electrode on the left leg.

  11. Augmented Limb Leads • Leads aVR, aVL, and aVF are augmented limb leads. • They are derived from the same three electrodes as leads I, II, and III  augmented reletive to central (neutral) terminal  they view the heart from different angles (vectors)  "exploring electrode" • Together with leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of the hexaxial reference system, which is used to calculate the heart's electrical axis in the frontal plane. • Lead aVR (augmented vector right  210°) • positive electrode (white) on the right arm • negative electrode is a combination of the left arm (black) electrode and the left leg (red) electrode,  augments the signal strength of the positive electrode on the right arm. • Lead aVL (augmented vector left  -30°) • positive (black) electrode on the left arm • negative electrode is a combination of the right arm (white) electrode and the left leg (red) electrode  augments the signal strength of the positive electrode on the left arm. • Lead aVF (augmented vector foot  90°) • positive (red) electrode on the left leg. • negative electrode is a combination of the right arm (white) electrode and the left arm (black) electrode  augments the signal of the positive electrode on the left leg.

  12. Hexaxonal Reference System • Based on the first six leads of the 12 lead ECG. • Determine the heart's electrical axis in the frontal plane. • Process: • locate the most isoelectric lead • find the corresponding spoke on the hexaxial reference system. • the perpendicular spoke will point to the heart's electrical axis. • Normal axis: -30o to +90o • Left axis deviation: -30o to -90o • Right axis deviation: +90o to +180o • Extreme axis deviation: -90o to -180o

  13. Axis • The heart's electrical axis refers to the general direction of the heart's depolarization wavefront (or mean electrical vector) in the frontal plane. • It is usually oriented in a right shoulder to left leg direction, which corresponds to the left inferior quadrant of the hexaxial reference system, although -30o to +90o is considered to be normal. • Left axis deviation (-30o to -90o) may indicate • left anterior fascicular block • Q waves from inferior MI • considered normal in pregnant women and those with emphysema • Right axis deviation (+90o to +180o) may indicate: • left posterior fascicular block • Q waves from high lateral MI • right ventricular strain pattern. • considered normal in children • Extreme right axis deviation (+180o to -90o) is rare, and considered an 'electrical no-man's land'.

  14. ECG appearance from various recording positions on frontal plane • Principle direction of depolarisation  main vector/axis • If vector at right angles to lead  isoelectric (equally positive & negative) • Normal Cardiac Axis = -30° - +90 ° • e.g. QRS complex (picture) • Isoelectric in aVL • Negative in aVR • Positive in aVF, I, II & III • Most positive  lead II • Main vector or axis of depolarisation  60°

  15. Precordial Leads • V1, V2, V3, V4, V5, and V6  unipolar leads placed directly on the chest. • Do not require augmentation. • View the heart's electrical activity in the so-called horizontal plane  Z axis. • Leads V1, V2, and V3  right precordial leads • Leads V4, V5, and V6  left precordial leads. • QRS Complex • negative in lead V1 • positive in lead V6 • should show a gradual transition from negative to positive between leads V2 and V4. • the equiphasic lead is referred to as the transition lead. • When the transition occurs earlier than lead V3, it is referred to as an early transition. • When it occurs later than lead V3, it is referred to as a late transition. • R-wave • should also be a gradual increase in the amplitude of the R wave between leads V1 and V4  R wave progression.

  16. Lead V1 is placed in the fourth intercostal space to the right of the sternum • Lead V2 is placed in the fourth intercostal space to the left of the sternum. • Lead V3 is placed directly between leads V2 and V4. • Lead V4 is placed in the fifth intercostal space in the midclavicular line (even if the apex beat is displaced). • Lead V5 is placed horizontally with V4 in the anterior axillary line • Lead V6 is placed horizontally with V4 and V5 in the midaxillary line.

  17. Stress (Exercise) ECG • 12-lead ECG recorded during exercise on a treadmill or bicycle • Limb leads placed on shoulders and hips • Blood pressure & symptoms assessed throughout test • Not always conclusive  false negatives & positives are possible • Indications & uses • Confirmation of angina diagnosis • Evaluation of stable angina • Assess prognosis following myocardial infarction • Assess outcome after coronary revascularisation • Diagnose & evaluate treatment of exercise induced arrhythmias

  18. Echocardiography (ECHO) • Ultrasound technique used for diagnosing CVS disorders • Uses standard ultrasound techniques to image two-dimensional slices (cross-sectional echo) of the heart. • Also produce accurate assessment of the velocity of blood and cardiac tissue at any arbitrary point using pulsed or continuous wave Doppler ultrasound  allows assessment of • cardiac valve areas and function • any abnormal communications between the left and right side of the heart, • any leaking of blood through the valves (valvular regurgitation) • calculation of the cardiac output as well as the Ejection fraction • Echocardiography is usually performed by cardiac sonographers and interpreted by a cardiologist.

  19. Ejection Fraction • Fraction of blood pumped out of a ventricle with each heart beat. • Commonly measured by echocardiograpy  volumes of the heart's chambers are measured during the cardiac cycle. • In a healthy 70-kg (154-lb) man • the SV is approximately 70 ml • left ventricular EDV is 120 ml • giving an ejection fraction of 70/120, or 0.58 (58%). • Right ventricular volumes being roughly equal to those of the left ventricle, the ejection fraction of the right ventricle is normally equal to that of the left ventricle within narrow limits. • Healthy individuals typically have ejection fractions greater than 0.55. • Damage to the myocardium (e.g. myocardial infarction;cardiomyopathy) impairs the heart's ability to eject blood  reduces ejection fraction  manifest itself clinically as heart failure. • The ejection fraction is one of the most important predictors of prognosis; those with significantly reduced ejection fractions typically have poorer prognoses.

  20. Radiology • Determines size & shape of heart • Assess structure of pulmonary blood vessels & lung fields • Postero-anterior (PA) projection of full inspiration • Estimate heart size by comparing maximum width of cardiac outline with maximum internal transverse diameter or thoracic cavity  cardiothoracic ration  should be less than 0.5

  21. Cardiac Catheterisation • Catheter inserted  vein or artery  heart • Left heart catheterisation • Assess CAD • Evaluate disease of mitral valve, aortic valve & aorta • Determine size & function of left ventricle • Right heart catheterisation • Assess pulmonary artery pressure • Detection of intra-cardiac shunts (measure oxygen saturation) • Coronary angiography • Detect stenoses • Guide revascularisation procedures (e.g. stenting; angioplasty)

  22. Manifestations of Cardiovascular Disease

  23. Chest Pain • Common presentation: • Cardiac disorders • Anxiety • Pulmonary disorders • Musculoskeletal disorders • Gastrointestinal disorders • Categorization of cardiac pain • Ischaemic • Pericardial • Atypical • Physiology of cardiac pain • Transmitted to cerebral cortex via autonomic nerve fibres • Variable referral area  ears to umbilicus

  24. Common Causes of Central Chest Pain Anxiety/emotion Cardiac • Myocardial ischaemia (angina) • Myocardial infarction • Myocarditis • Pericarditis • Mitral valve prolapse syndrome Aortic • Aortic dissection • Aortic aneurysm Oesophageal • Oesophagitis • Oesophageal spasm • Mallory-Weiss syndrome Pulmonary • Massive pulmonary embolus Mediastinal • Tracheitis • Malignancy

  25. Common Causes of Peripheral Chest Pain Lungs & Pleura • Pulmonary infarction • Pneumonia • Pneumothorax • Malignancy • Tuberculosis Neurological • Prolapsed intervertebral disc • Herpes zoster • Thoracic outlet syndrome Musculoskeletal • Osteoarthritis • Rib fracture or injury • Intercostal muscle injury • Costochondritis (Tietze’s syndrome) • Coxsachie virus (epidemic myalgia; Bornholm disease) • Soft tissue injury  related to every day activity

  26. Myocardial Ischaemic Pain • Typically described • pressing; squeezing; crushing • N.B. hand gestures often used (e.g. clenched fist) • Pain usually greatest in central precordium • Radiates  distribution of lower cervical nerves • Neck • Lower jaw • Shoulder/arm (left side most common; usually ulnar side) • Autonomic nervous response  e.g. N/V; sweating; palpitations • Relieved by nitroglycerin • Angina pain (coronary arteriosclerosis) • Precipitated by exertion (N.B. unstable angina  may occur any time) • Relieved by rest (5 minutes) • Emotion may cause pain • Myocardial infarction • Typically occurs suddenly while patient at rest • Not relieved by rest • Arterial spasm • Tends to occur at rest or nocturnally

  27. Diagram depicting distribution of typical ischamic chest pain

  28. Pericardial Pain • Caused by inflammation of parietal pericardium • Sensation  sharp; stabbing; burning; cutting • Aggravated by: • Coughing • Swallowing • Deep breathing • Lying down • Relieved by • Leaning forward • Remaining still • Can last for hours or days • Not relieved by nitroglycerin • Differentials  pleural pain; musculoskeletal

  29. Atypical Chest Pain • Tends to be stabbing or burning • Variable in position & intensity between episodes • Unrelated to physical exertion & unresponsive to nitroglycerin • Duration  seconds to hours or days (persistant) • No objective evidence that atypical chest pain indicates serious heart disease • Associated with • Mitral valve prolapse (syndrome) • Atrial tachycardia • Anxiety

  30. Some Differentials of Chest Pain Psychological • Emotional distress  atypical chest pain • Features of anxiety and/or neurosis • Pain lacks predictable association with exercise • N.B. psychological features can co-exist with organic heart disease Myocarditis & Pericarditis • Left retrosternal chest pain • May be in left or right shoulder • Varies in intensity with movement and respiration • Sharp pain  ‘catches’ during inspiration or coughing • May be history of prodromal viral illness Mitral Valve Prolapse • Sharp left sided chest pain (N.B. M/S disorder) • Atypical chest pain • Associated with typical benign arrhythmias

  31. Aortic dissection • Abrupt onset  collapse common • Severe, sharp & tearing pain  central chest pain • Often felt in or radiating to back (between scapulae) • Asymmetry of pulses (brachial; carotid; femoral) Oesophageal Pain • Closely mimics angina pain • s/t precipitated by exercise & relieved by nitrates • Hx  pain related to eating, drinking or reflux Muskuloskeltal Pain • Variable in site and intensity • Does not usually fall into other chest pain patterns • Pain may vary with posture or movement of the upper body • May have local tenderness  rib; costal cartilage

  32. Investigations of Chest Pain • ECG (resting & stess) • Troponin • Creatinine kinase • FBC; ESR; CRP • D-dimer • U&E

  33. DyspnoeaBreathlessness; Shortness of breath; Difficulty breathing • Perception of uncomfortable, distressful or laboured breathing • Variable intensity • Uncomfortable awareness in breathing • Unable to breath (‘fighting’ for breath) • Physiological aspects of dyspnoea • Cardiac output inadequate for body’s metabolic demands (without pulmonary oedema) • Oedema in bronchial walls & stiffening of the lung d.t. parenchymal or alveolar oedema (cardiac dyspnoea) • Sensation originates in cerebral cortex  stimuli arising in lungs, upper airways & respiratory muscles

  34. Clinical Types of Dyspnoea Physiologic dyspnoea • Physical exertion • Acute hypoxia; hypoxaemia (e.g. high altitude) • Hypercapnia • Minimal in carbon monoxide poisoning Pulmonary dyspnoea • Restrictive defect  low compliance of lungs or chest wall • Obstructive defect  airflow resistance Cardiac dyspnoea • Heart failure • Left ventricular failure  cardiac asthma  bronchospasm; wheezing; hyperventilation • Generally worsened by exercise & relieved by rest • Forms of cardiac dyspnoea • Acute pulmonary oedema • Chronic heart failure • Angina equivalent

  35. Orthopnoea • Respiratory discomfort that occurs while the patient is supine  must sit up • Precipitated by increased venous return of blood to a failing left ventricle (can’t handle increased preload) • Increased effort of breathing in supine position • May occur in other cardiovascular disorders (e.g. pericardial effusion) Paroxysmal nocturnal dyspnoea • Patient wakes up gasping for air  must sit or stand • Produce by same factors that cause orthopnoea • Severe heart failure  fluid from interstitial tissue in peripheries moves into circulation with in 2 hours of sleep  pulmonary oedema  ‘fighting for breath’ • Other causes  mitral stenosis; aortic insufficiency; hypertension Cheyne-Stokes respiration • Regularly alternating periods • slowly diminishing respiration & apnoea • Progressivly increased respiration (hyperpnoea) & hyperventilation • Sensation of breathlessness & panic during hyperventilation phase • Causes • Cardiologic malfunction  slowing of circulation • Diffuse cerebral atherosclerosis, stroke or head trauma  medullary respiratory centre impairment • Drugs  narcotics; barbituates

  36. Chemical; Metabolic • Diabetic acidosis  deep, slow breaths (Kussmaul respiration) • Uraemia  combination of acidosis, heart failure, pulmonary oedema & anaemia  severe panting Central causes • Cerebral lesions (e.g. trauma) • Biot’s respiration  irregular periods of apnea alternate with periods of 4 or 5 breaths • Hyperventilation commonly seen after head injury ( PaCO2  reflex CNS vasoconstriction   cerebral perfusion  beneficial ICP) Psychogenic • Anxiety  sensation of inadequate breathing  responds by over-breathing • Hyperventilation by be obvious & continuous  blowing off excess CO2  acute alkalosis • Patinets overtly anxious  altered awareness & paraesthesiaes • May develop positiv Trousseau’s & Chvostek’s signs (serum Ca 2+) • Overbreathing may be subtle  deep, subtle respirations  may cause respiratory alkalosis (repeated frequently)

  37. Causes of Acute Dyspnoea at Rest Cardiovascular system • Acute pulmonary oedema Respiratory System • Acute severe asthma • Acute COPD exacerbation • Pneumothorax • Pneumonia • Pulmonary embolus • ARDS • Inhaled foreign body • Lobar collapse • Laryngeal oedema Other • Metabolic acidisis (e.g. ketoacidosis; lactic acidosis; uraemia) • Anxiety; Hysterical hyperventilation (respiratory alkalosis)

  38. Causes of Chronic Exertional Dyspnoea Cardiovascular system • Chronic congestive cardiac failure • Myocardial ischaemia Respiratory System • COPD • Chronic asthma • Chronic pulmonary thromboembolism • Bronchial Ca • Interstitial lung dx (e.g. sarcoidosis; fibrosingalveolitis) • Large pleural effusions Other • Severe anaemia • Obesity

  39. Palpitationsperception or conscious awareness of heart activity by the patient • Cardiac activity controlled by autonomic nervous system • Sensed: • With increased stroke volume or heart rate (e.g. exercise) • Increased awareness of body functions (e.g. anxiety) • Very common complaint  source of major concern • May be used to describe range of disorders • Unusually fast & erratic heart rate • Unusually slow or forceful heart beat • Chest pain or breathlessness • History most important • Determine what is meant by patient • Assess likely mechanism of sensation • Assess possibility of underlying cardiac disease

  40. Usually benign with good outlook (unless evidence of underlying structural disease) • Triggers of awareness of heart beat, sinus tachycardia or benign extrasystoles • Stress • Intercurrent illness • Caffeine • Alcohol • Nicotine • Careful explanations required  reassurance • Further investigations if evidence of underlying causes  ECG

  41. Evaluation of Palpitation • Continuous or intermittent? • Regular or irregular heart beat? • Heart rate? • Do symptoms occur in discreet attacks? • Abrupt onset? • How do attacks terminate? • Are there any associated symptoms? • E.g. chest pain; lightheadedness; polyuria; etc • Any precipitating factors? • E.g. exercise; alcohol • History of structural heart disease? • E.g. CAD; valvular heart disease

  42. Differential Diagnoses • Anxiety • Poorly defined attacks  pounding; forceful • Relatively fast (90-120/min) • Hyperdynamic circulation • Similar presentation as anxiety • E.g. anaemia; pregnancy; thyrotoxicosis (most common cause) • Atrial or ventricular extrasystoles (ectopic beats) • Recurrent, short-lived bouts of an irregular beat • ‘flip’ of ‘jolt’ in chest; missed or skipped beats • More frequent during stress or debility • May be triggered by alcohol, chocolate or strong cheese

  43. Tachycardia • Discrete bouts of very rapid heart beat (>120/min)  e.g. atrial, junctional or ventricular tachycardias • Percieved as rapid & regular  sudden onset & termination (supraventricular or ventricular tachycardia) • Onset of atrial tachyarythmia  increased atrial natriuretic factor  need to urinate increased • Atrial fibrillation • Typically present with characteristic irregular & chaotic tachycardia • CAD • Palpitation accompanied by cardiac type ischaemic chest pain • Decreased diastolic coronary artery blood flow & ischaemia result from tachycardia

  44. Approach to Diagnosis of Palpitation

  45. TachycardiaPulse rate of > 100bpm in an adult • Sinus tachycardia • Exercise • Pain • Fever • Excitement • Anxiety • Hyperthyroidism • Pregnancy • Anaemia • Heart failure • Medications  e.g. sympathomimetics; vasodiators • Tachyarythmia • Atrial fibrillation • Atrial flutter • Supraventricular tachycardia • Ventricular tachycardia

  46. Narrow Complex TachycardiaECG rate > 120bpm with QRS complex duration of <120ms • Sinus tachycardia • Normal P wave followed by normal QRS complex • Supraventricular tachycardia (SVT) • P-wave absent or inverted after QRS • Atrial Fibrillation(AF) • Absent P-wave; irregular QRS complex • Atrial flutter • Atrial rate 300bpm with flutter (saw-tooth) base-line • Ventricular rate a proportion of this (e.g. 150 = 2:1 flutter) • Atrial tachycardia • Abnormal shaped P-waves; may out number QRS complex • Junctional tachycardia • Rate 150-250 bpm • P-wave buried in QRS complex or occurring after QRS complex

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