Cardiology Flashcards
what key event directly initiated myocardial contraction
release of stored calcium from sarcoplasmic reticulum (calcium induced calcium release)
most common congenital cardiac defect in t21
AVSD
Management of VSD/AVSD
In the neonatal period, pulmonary vascular resistance is high which limits the degree of left to right shunting. This shunting increases with age as the PVR and RV compliance decreases resulting in pulmonary vascular engorgement and symptoms of CCF.
Medical treatment is indicated for symptomatic CCF. This commonly involves a combination of captopril (for afterload reduction), frusemide (reduces pulmonary congestion) and digoxin (inotropic and deactivating effects).
Surgical management involves patch closure of the septal defects as well as valvular repair. It is usually performed in the first six months of life. In the setting of AVSDs, medical management is only indicated for symptomatic congestive cardiac failure, otherwise the treatment is surgery (and should be urgent once there are signs of pulmunary hypertension)
In small infants, pulmunary artery banding may be performed as this protects the pulmunary circuit from HTN until surgery can be performed
In babies with T21, surgery should be done before 6 months, as they are at risk of pulmunary hypertension
Cardiac embryology
Angiogenic cell clusters arise in the mesoderm
At 20 days, paired heart tubes fuse to form a single heart tube
By 24 days the cardiac loop is formed
The bulbus cordis becomes the right ventricle while the primitive ventricle becomes the left ventricle.
BMI weight criteria
Underweight: BMI <5th percentile for age
Normal weight: BMI 5th to <85th percentile
Overweight: BMI 85th to <95th percentile
Obesity: BMI ≥95th percentile
Epoprostenol
Prostaglandin analogue
Vasodilator
Treatment of pulmunary hypertension
Last line therapy while awaiting transplant
Epoprostenol is too unstable to be given orally. Its intravenous half-life is less than six minutes so it has to be given by continuous infusion.
Can be unstable at room temp so needs to be carried around on a backpack on ice.
The infusion should not be stopped suddenly as the patient can deteriorate within minutes- acute pulmunary hypertensive crisis (acute rise in pulmunary vascular resistance, resulting in R heart faiure and death) Adjustments to the infusion rate must be done under observation so that heart rate and blood pressure can be monitored for several hours.
Should use 2 + medications with differing mechanisms of action eg with endothelin receptor antagonist; thus less risk to child if infusion is suddenly ceased
Electrolyte abnormalities which cause prolonged QT interval
Hypokalemia
Hypocalcemia
Hypomagnesemia
Hypothermia
Major criteria of Rheumatic fever
Carditis
Polyarthritis (or monoarthritis if high risk)
Chorea
Erythema marginatum
Subcutaneous nodules
Minor criteria of rheumatic fever
Fever
Raised ESR/CRP
Polyarthralgia (oe monoarthralgia if high risk)
Prolonged PR interval on ECG
Pulsus paradoxus can be caused by ..
Cardiac tamponade
In healthy individuals, inspiration causes the systolic blood pressure to fall slightly as a result of the greater volume of blood accommodated by the pulmonary vascular bed. This occurs despite inspiratory increase in venous return to the right heart. In cardiac tamponade, right ventricular filling is maintained at the expense of restricted left ventricular filling, and the systolic blood pressure falls further (>10 mm Hg). This exaggerated fall in systolic blood pressure with inspiration is referred to as pulsus paradoxus.
Cardiac complication most likely with DMD
dilated cardiomyopathy
Qp Qs equation
(Aortic sat- MV sat)/ (pulmonary vein sat - pulmonary artery sat)
Cardiac anomalies associated with Noonans syndrome
Pulmunary artery stenosis
Hypertrophic cardiomyopathy
ASD
Superior axis on ECG
Drugs which cause QT prolongation
ntiarrhythmics e.g. amiodarone, TCAs, antipsychotics (haloperidol, quetiapine), anti-infectives (clarithromycin, fluconazole, erythromycin).
which anti arrythmics contraindicated in WPW
verapamil and digoxin
increase anterograde conduction
Class Ia antiarrythmics
Na channel blocker
Which drugs are effective in supraventricular arrythmias?
Adenosine
Digoxin
Verapamil (dont use in neonates!)
Both ventricular and supraventricular:
amiodorone
Quinidine
Flecanide
Class Ia antiarrythmics
Class 1- all sodium channel blockers
Procainamide
Quinidine
Lengthens the action potential
ECG effect: prolongs QT and QRS
Class Ib anti arrythmics
Lidocaine
only used for ventricular tachyarrythmias
shortens the action potential
Class Ic anti arrythmics
Flecanide
Strongest Na channel blocker
Causes widening of QRS
Prolongs slope of phase 0, doesnt affect the duration of the action potential
Pro arrythmic
Used for severe SVT and VT
Class II anti arrythmics
Beta blockers
Block the effects of catecholamines at B 1 adrenergic receptors and reduce conduction through the AV node
Selective: atenolol, metoprolol
Non selective: propranolol
Class III anti arrythmics
Potassium channel blockers
Prolong repolarisation/refractory period – prevents re entrant arrythmias
Amiodorone (also has class 1, 2, and 4 actions, lots of systemic side effects)
Sotalol (also non selective beta blocker)
Can cause QT prolongation
Class IV anti arrhythmic
Calcium channel blockers
Reduce condition through AV node, shorten the plateau and thus reduce the contractility of the heart
Verapamil
Diltiazam
Class V anti arrhythmic
Digoxin
- decreases condiction of impluses through the AV node –> reduces HR, extending the time of contraction
- increases contractility and stroke volume
Adenosine
-used to terminated SVT
which anti arrhythmic is contraindicated in WPW and infants
verapamil
class 4 anti arrythmic (ca channel blocker)
depresses contractility -> reduces cardiac output
management of SVT in infants
sotolol (class III)
flecanide (class Ic)