Cardiology Flashcards
Define acute rheumatic fever
Systemic illness that occurs 2-4 weeks after pharyngitis in some people
- due to cross-reactivity to group A beta-haemolytic streptococcus (GAS)
- also called streptococcus pyogenes
Epidemiology of acute rheumatic fever
4 million children worldwide
94% of cases in developing countries
Most common in tropical countries
Most common in females
Pathophysiology of acute rheumatic fever
Streptococcus pyogenes is a gram-positive cocci
- produces two cytolytic toxins - streptolysin O and S
Rheumatogenic strains contain M proteins in cell wall
- B cells stimulated to produce anti-M protein antibodies
- also cross-react with other tissues - heart, brain, joints and skin
- exacerbated by production of activated cross reactive T cells
Risk factors for acute rheumatic fever
Children and young people Poverty Overcrowded and poor hygiene Family history of rheumatic fever D8/17 B cell antigen positivity
Clinical features of acute rheumatic fever
Revised Jones Diagnostic Criteria
- positive throat culture for group A strep or elevated anti-streptolysin O or anti-deoxyribonuclease B
- 2 major criteria or 1 major criteria and 2 minor criteria
Major criteria for acute rheumatic fever
Sydenham's chorea Polyarthritis Erythema marginatum Carditis Subcutaneous nodules
Minor criteria for rheumatic fever
CRP or ESR raised
Arthralgia
Pyrexia/fever
Prolonged PR interval
Differential diagnosis of acute rheumatic fever
Septic arthritis - usually only one joint - positive gram stain, culture and elevated WCC of aspirated synovial fluid Reactive arthropathy - commonly males - a/w urethritis and conjunctivitis Infective endocarditis - positive blood culture - vegetation on valves on echocardiogram - janeway lesions, osler nodes, splinter haemorrhages Myocarditis - troponin and CK elevated - saddle ST segments or T wave changes on ECG
Investigations for acute rheumatic fever
Bloods - ESR, CRP, FBC Blood cultures - exclude sepsis Rapid antigen detection test Throat culture - may be negative by time rheumatic symptoms Anti-streptococcal serology - ASO and anti-DNASE B titres ECG - prolonged PR interval CXR - if carditis suspected Echo cardiology
Management of acute rheumatic fever
Initial
- abx - benzathine benzylpenicillin
- aspirin or NSAIDs
- assess for emergency valve replacement
- glucocorticosteroids and diuretics in severe carditis
Definitive
- secondary prophylaxis with IM benzathine benzylpenicillin every 3-4 weeks
- oral phenoxymethylpenicillin twice daily
- oral sulfadiazine daily
- oral azithromycin in penicillin allergy
Complications of acute rheumatic fever
Permanent damage to heart valves
Chronic rheumatic heart disease
Define infective endocarditis
Infectious disease of heart and surrounding vessels
Pathophysiology of infective endocarditis
Triad of
- endothelial damage
- platelet adhesion
- microbial adherence
Structural abnormalities cause significant pressure gradient -> endothelial damage through sheer stress forces
Prosthetic material -> endothelial damage and promote sterile platelet-fibrin deposition
Bacteremia then occurs - adhere to lesion and invade underlying tissue
Common causative organism of infective endocarditis
Have specific surface receptors to fibronectin - allow microbe to adhere to thrombus at outset
- staphylococcus aureus
- streptococcus viridans
- streptococcus pneumoniae
- alpha-haemolytic streptococci (S.viridans) - a/w dental procedures
- enterococci - post genitourinary or gastrointestinal surgery
Clinical features of infective endocarditis
Persistent low grade fever Heart murmur - changing Splenomegaly Cutaneous manifestations uncommon in paediatric population - petechiae - osler's nodes - janeway lesions - splinter haemorrhages
Investigations for IE
Blood cultures Echocardiography Anaemia Leukocytosis Raised ESR Microscopic haematuria
Modified Duke criteria for IE
MAJOR Positive blood culture - typical microorganism from 2 separate cultures Evidence of endocardial involvement MINOR Predisposition - heart condition of IV drug use Fever - temp > 38 Vascular phenomena - major arterial emboli, septic pulmonary infarcts, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions Immunologic phenomena - Glomerulonephritis, Osler's nodes, rheumatoid factors Microbiological evidence - positive blood culture ECHO findings
Diagnosis of IE
2 major criteria OR 1 major and 3 minor OR 5 minor
Aims of management of IE
Systemic embolisation Abscess formation Pseudoaneurysms Valvular perforation Heart failure
Indications for surgical management of IE
Vegetation
- highly mobile vegetation
- persistent vegetation after systemic embolisation
- > 1 embolic event in first 2 weeks of medical management
Increase in vegetation size
Valvular dysfunction
- acute aortic or mitral insufficiency with signs of ventricular failure
- heart failure unresponsive to medical management
- valve perforation or rupture
Perivalvular extension
- valvular dehiscence, rupture or fistula formation
- new onset heart block
- large abscess or extention of abscess
Antibiotic choice for IE
Aerobic cover usually sufficient
- IV penicillin or IV ceftriaxone for 4 weeks
- add gentamicin if penicillin resistant organisms
Methicillin-susceptible staphylococcus = beta-lactamase resistant penicillin for 6 weeks
Methicillin-resistant = vancomycin for 6 weeks
Enterococcus = 4-6 weeks IV penicillin with gentamicin
HACEK = ceftriaxone with gentamicin for 4 weeks
Prophylaxis for IE
No longer routinely offered to at risk groups
Those at higher risk for IE
Acquired valvular heart disease with stenosis or regurgitation Hypertrophic cardiomyopathy Previous IE Structural congenital heart disease Valve replacement
Define Tetralogy of Fallot
Most common cyanotic congenital heart disease Tetrad of - Ventricular Septal Defect (VSD) - Pulmonary Stenosis (PS) - Right Ventricular Hypertrophy (RVH) - Overriding aorta
Epidemiology of Tetralogy of Fallot
Up to 10% of all congenital heart disease
Prevalence of 3-6 per 10,000 births
Risk factors for TOF
Males 1st degree family history of CHD Teratogens - alcohol - foetal alcohol syndrome - warfarin - foetal warfarin syndrome - trimethadione - antiepileptic drug used in treatment resistant epilepsy Genetics - CHARGE syndrome - coloboma, heart defects, atresia choanae, retardation of growth/development, genitourinary anomalies, ear anomalies - Di George Syndrome - VACTERL association - vertebral abnormalities, anorectal malformation, cardiac defects, tracheo-oesophageal fistula, renal anomalies, limb abnormalities Associated congenital defects - right aortic arch - congenital diaphragmatic hernia
Pathophysiology of TOF
VSD
- perimembranous, muscular or doubly committed (located near pulmonary and aortic valves)
- left-to-right shunt = acyanotic
- in severe disease due to increased right ventricular pressure -> right-to-left shunt = cyanotic
PS
- classified by location - infundibular septum, septum or combination
- impaired flow of deoxygenated blood in main pulmonary artery
- severe leads to intermittent RVOT obstruction -> hypoxic episodes (tet spells)
RVH
- due to high pressure to overcome PS
- develops in utero
- boot sign on CXR
Overriding aorta
- dilated and displaced over intraventricular septum
- in severe disease multiple aorto-pulmonary collateral arteries may form to increase pulmonary blood flow
Clinical features of TOF
Mild
- usually asymptomatic
- develop cyanosis at age 1-3
Moderate-severe
- present in first few weeks of life with cyanosis and respiratory distress
- prone to recurrent chest infections or fail to thrive
Extreme
- TOF with pulmonary atresia or with absent pulmonary valves
- duct dependent lesions - deoxygenated blood can only flow through lungs via patent ductus arteriosus
- often detected on antenatal scans
- if undetected present within first few hours of life with marked resp distress and cyanosis
Features of hypoxic (Tet) spells
Peak incidence months 2-4 months
Paroxysm of hyperpnoea
- rapid deep respirations
- due to increased right-to-left shunting, CO2 accumulates stimulating central respiratory centre
- causes further right-to-left shunting perpetuating hypoxia
Irritability - manifested by prolonged, unsettled crying
Increasing cyanosis
May be precipitated by dehydration, anaemia or prolonged crying (induces tachycardia and reduced systemic vascular resistance)
Features of examination for TOF
General - central cyanosis - clubbing Palpation - thrill or heave Auscultation - loud single S2 - closure of aortic valve in diastole with absent pulmonary valve closure due to stenosis - pansystolic murmur - VSD, mid or upper left sternal edge - ejection click - dilated aorta, immediately after S1 - continuous, machinery murmur - PDA, upper LSE or left infraclavicular area Signs of congestive heart failure - sweating - pallor - tachycardia - hepatosplenomegaly - generalised oedema - bilateral basal crackles - gallop rhythm
Differential diagnosis of TOF
Other cyanotic CHD - critical PS - transposition of the great arteries - totally anomalous pulmonary venous drainage - hypoplastic left heart syndrome Isolated VSD Sepsis - resp distress and hypoxia
Investigations for TOF
ECG - right axis deviation and RVH
Microarray - if genetic syndromes suspected
CXR - boot shaped heart (RVH) and reduced pulmonary vascular marking (decreased pulmonary blood flow)
Echocardiogram - gold standard for diagnosis confirmation
Cardiac CT angiogram - delineate anatomy if coronary abnormalities suspected
Cardiac MRI
Cardiac catheter
