Cardiology Flashcards
What are the causes of acquired long QT?
Antibiotics - macrolides, bactrim, fluoroquinolones
Antifungals - fluconazole, itraconazole, ketoconazole
Antihistamines (non-sedating)
Antipsychotics - haloperidol, risperidone
Tricyclic antidepressant
Class 1A and III anti-arrhythmics
Diuretics - frusemide
Opiates
HYPOcalcaemia/kalaemia/magnesaemia
What is the cut-off in sec for prolonged QT?
> 0.47 sec = highly indicative
>0.44 sec = suggestive
What are the causes of short QT?
Digoxin toxicity
Hypercalcaemia
= due to gain-of-function of cardiac potassium channels
Manifests as atrial or ventricular fibrillation, a/w syncope/sudden death.
Has congenital causes
What is the treatment for long QT syndrome?
- Beta-blocker
- Propanolol > atenolol/metoprolol
- Not effective in LQTS type 3 - Pacemaker
- Implanted cardiac defibrillator
What are the auscultatory findings of ASD?
- Fixed, wide splitting of S2
- Systolic ejection murmur
(Crescendo-decrescendo, loudest left UPPER sternal border) - +/- Early/mid-diastolic murmur
(If shunt large as will have increased flow across tricuspid valve; best heard left LOWER sternal) - +/- Apical holosystolic murmur t
(Tricuspid/mitral regurgitation if ostium primum)
When do you treat ASD?
- Symptomatic
- Asymptomatic with Qp:Qs > 2:1
- Right ventricular enlargement
Done >1 year but before enters school as less mortality/morbidity
What are the auscultatory findings of AV septal defect?
- Low-pitched, mid-diastolic murmur at left lower sternal border (increased pulmonary venous return and diastolic flow across AV valve)
- Pulmonary systolic ejection murmur (large pulmonary flow)
- +/- Harsh apical holosystolic murmur (mitral regurgitation)
- +/- Widely split S2 (if massive pulmonary flow)
What are the auscultatory findings of VSD?
- Holosystolic
(Begins before AV valve closure thus obscures S1
- Intensity depends on size (small = louder); left LOWER sternal border - +/- Mid-diastolic murmur at apex
(Due to extra flow across mitral valve when pulmonary:systemic flow >2:1) - +/- Prominent S2
(If pulmonary HTN develops as more forceful pulmonic valve closure during diastole)
What are the auscultatory findings of PDA?
- Continous, rumbling/machinery-like murmur, increasing in intensity during late systole; BELOW left clavicle
OTHER
1. Bounding pulses
2. Wide pulse pressure
(Both due to pulmonary artery ‘stealing’ blood from aorta during diastole)
What are the auscultatory findings of pulmonary hypertension?
1. Narrowly split or single S2 (Pulmonic valve closes faster as there is higher pulmonary pressure) 2. Loud pulmonic S2 component 3. +/- Diastolic decrescendo murmur (Secondary to pulmonary regurgitation)
What are the auscultatory findings of coarctation of the aorta?
- Systolic murmur to left axilla/back
- +/- Continuous murmur over praecordium
(If collateral vessels develop)
OTHER
- Upper and lower limb BP gradient (>10 mmHg)
- Diminished extremity pulses
- Brachiofemoral delay
When does the ductus arteriosus close?
Functional haemodynamic closure within 10-15 hours after birth
(50% close within 24 hours, 90% in 48 hours, virtually all in 72 hours)
Fully closes anatomically by 3 weeks
When does the foramen ovale close?
Flap fusion complete by age 2 in 70-75% of children
Remaining 25-30% have PFO
What are the auscultatory findings of supravalvular aortic stenosis?
- Systolic murmur WITHOUT click; heard at base of neck
OTHER
1. BP right arm > 15mmHg left arm
As jet directed into the brachiocephalic artery
What are the CXR findings of coarctation of the aorta?
- Figure of 3 sign
(Formed by pre-stenotic dilatation of aortic arch and left subclavian artery, indentation at coarctation site and post-stenotic dilation of descending aorta) - Inferior rib notching
(Dilated intercostal vessels which form to bypass erode inferior margin of ribs)
What are the auscultatory findings of pulmonary stenosis?
- Systolic ejection click (varies with respiration) along LEFT UPPER sternal border
- Harsh, systolic crescendo-decrescendo murmur; LEFT UPPER sternal border
- Radiation to below left clavicle and often to back
What are the ECG findings in right vs. left atrial hypertrophy?
P wave -> look at leads II, V1
aVR will be negative
Depolarises in RA first -> LA
RIGHT atrial enlargement = P pulmonale
(‘T’ricuspid) -> ‘T’all, peak P wave
> 2.5mm (inferior leads II, III, aVF)
> 1.5mm V1 and V2
LEFT atrial enlargement (‘M’itral) -> ‘M’-like notched P wave in II (specific sign); and enlarges terminal negative portion of P wave in V1 (sensitive sign)
What are the auscultatory findings of mitral valve stenosis?
- Apical diastolic murmur
- +/- Apical systolic murmur (if mitral insufficiency present)
- Loud pulmonic S2
(From pulmonary hypertension)
ECG
1. LA enlargement
(notched P waves lead II and enlarged negative terminal portion of P wave in V1)
2. RVH (rather than LVH; due to pulmonary HTN)
What effects does the Valsava maneauver have on HOCM vs. AS?
Valsalva maneauver -> REDUCES venous return (as increased intrathoracic pressure)
(Note: Squatting INCREASES venous return)
HOCM
Decreased venous return -> decreased LV volume -> increase effect of obstruction -> LOUDER murmur
AS
Decreased venous return -> decreased LV volume -> less flow through AS -> SOFTER murmur
What does the degree of cyanosis in TOF depend on?
Degree of right ventricular outflow obstruction
What are the auscultatory findings of hypertrophic cardiomyopathy?
- Systolic murmur, grade 3-4 crescendo-decrescendo at MIDDLE LEFT to UPPER RIGHT sternal border
- Gets louder with Valsalva or rising to erect position
- +/- Thrill over praecordium
(No thrill over suprasternal notch)
What are the auscultatory findings of ToF?
- Systolic ejection at LEFT UPPER sternal border
- +/- Aortic click (in older patients; due to aortic dilation)
If RVOT obstruction severe, very little flow hence murmur can disappear
What condition(s) is ToF associated with?
DiGeorge (22q11.2 deletion) - especially if right aortic arch present
Also: T21/18/13, Alagille syndrome, CHARGE
What is the most common cause of sudden death in young athletes?
Hypertrophic cardiomyopathy = most common cause in competitive athletes
Aortic stenosis = congenital defect most commonly associated with sudden death in children
Other:
Coronary artery anomalies, commotio cordis (blow to chest -> V.fib), aortic rupture, long QT, WPW, myocarditis
What are the two most common infective causes of myocarditis?
Enterovirus (coxsackie B)
Adenovirus
How do you treat atrial fibrillation/flutter in WPW?
IV procainamide
For cardioversion if haemodynamic instability
NEVER treat with digxoin and digoxin: although increases AV refractory period, it DECREASES refractory period in accessory pathway -> V-fib
Why is IV verapamil contraindicated in infants (<1 year)?
Haemodynamic collapse with hypotension and bradycardia
What is the difference between class 1a, 1b and 1c antiarrhythmics?
1a - lengthens action potential (right shift); i.e. depresses phase 0, prolongs repolarisation
Examples: procainamide, quinidine
1b - shortens action potential (left shift); i.e. depresses phase 0 selectively in abnormal/ischaemic tissue, shortens repolarisation
Examples: lignocaine, phenytoin
Ic - does not affect action potential (no shift); i.e. markedly depresses phase 0, minimal effect on repolarisation
Examples: flecainide
Which class of antiarrhythmic drug prolonged QT?
Class III (K+ channel blockers)