UWorld Targeted Review: Cardio Flashcards
primary cause of morbidity in acute rheumatic fever?
heart failure from severe pancarditis
[mitral stenosis develops years/decades later]
what 2 features will ECG of patients with WPW show?
WPW = Wolff-Parkinson-White triad
- shorted PR interval
- delta wave: slope in beginning of QRS (—> widened QRS complex)
caused by accessory bypass tract (bundle of Kent) connecting atria and ventricles
ECG shows narrow QRS complex tachycardia with regular rhythm and non-visible P waves
paroxysmal supra-ventricular tachycardia (PSVT): episodic arrhythmia originating at/above the AV node (why QRS are narrow)
most common type is AV nodal reentrant tachycardia (AVNRT) - due to 2 distinct AV nodal conduction pathways (fast + slow)
describe the cause of AVNRT
AVNRT = AV nodal reentrant tachycardia: affects otherwise healthy young patients
due to 2 distinct AV nodal condition pathways: fast pathway (long refractory period) and slow pathway (short refractory period)
normally works fine because they meet and cancel out, but if there is a premature atrial contraction (PAC) while the fast tract is still refractory, the impulse may reach the bottom but then be carried upwards by the fast pathway (now not refractory) —> reentrant circuit with rapid conduction is created
cause of WPW vs AVNRT
WPW = accessory bypass tract (bundle of Kent) connects atria and ventricles, triggered by reentry of impulses through accessory pathway
AVNRT = fast + slow dual conduction pathways, triggered by premature atrial contraction (PAC) allowing fast pathway to creating a reentrant circuit
[most common type of supraventricular tachycardia]
which of the following describes the effect of clonidine?
a. decreased presynaptic release of ACh
b. decreased presynaptic release of NE
c. blockage of beta1 receptors in SA node
d. blockage of Ca2+ channels in AV node
e. blockage of K+ channels in AV node
clonidine = alpha2 agonist, stimulates presynaptic receptors in the rostral ventrolateral medulla (area responsible for basal and reflex control of SNS activity) —> decreased NE release, subsequent bradycardia and decreased vascular resistance
b. decreased presynaptic release of NE
where does atrial fibrillation most often arise?
near the pulmonary veins
what is the greatest determinant of the severity of Tetralogy of Fallot?
degree of RV outflow tract obstruction
TOF: RV outflow tract obstruction + large VSD + overriding aorta + RV hypertrophy
[VSD size isn’t determinant because it is always large]
how does Tetralogy of Fallot affect the following?
a. RV pressure
b. pulmonary artery pressure
c. LA pressure
a. RV pressure - INCREASE (due to RVOT obstruction)
b. pulmonary artery pressure - DECREASE (blood is obstructed from entering, so there’s a lower volume)
c. LA pressure - DECREASE (receiving less blood from lungs)
how would bicuspid aortic valve vs pulmonic stenosis affect cardiac auscultation?
bicuspid aortic valve —> narrowed/paradoxical split of S2
pulmonic stenosis —> widely split S2
[it goes A2, then P2 - like the alphabet]
pt experiencing palpitations is given rapid IV administration of a drug that causes short-lived flushing, burning in the chest, and SOB - what is the dx and what was the drug given?
paroxysmal supraventricular tachycardia (PSVT) - treated with adenosine
adverse effects include flushing, hypotension, bronchospasm, high-grade AV block
what are the phases and ions being moved in each phase for pacemakers vs non-pacemaker cardiomyocytes?
pacemakers:
4: Na+ in
0: Ca2+ in
3: K+ out
non-pacemakers:
4: resting
0: Na+ in
1: K+ out
2: Ca2+ in / K+ out
3. K+ out
QRS complex duration is typically reduced during exercise. However, a patient’s QRS duration is measured normal at rest and prolonged at near-maximal heart rate. They take a drug to treat their atrial fibrillation. What drug are they taking?
flecainide: class Ic anti-arrhythmic used to treat supraventricular tachycardias (such as a-fib)
Class Ic have strong use dependence (slowest to dissociate) and therefore prolong the QRS complex (Na+ blocking effects intensify as HR increases)
Class Ic bind fast Na+ channels responsible for phase 0 depolarization, blocking inwards Na+ current
which medications should be avoided in patients with hypertrophic cardiomyopathy?
HCM severity is determined by degree of LV outflow tract obstruction, which is lessened by more volume in the heart (puts pressure on the walls to open up the chambers)
therefore, drugs that decrease LV blood volume should be avoided, including:
1. nitrates, diuretics - reduce preload
2. hydralazine (arterial dilator) - reduces afterload
3. dihydropyridine Ca2+ channel blockers, ACEi - combined venous/arterial dilators
instead, tx w/ beta blockers and non-dihydropyridine Ca2+ channel blockers (verapamil)
what is the most common congenital cardiac anomaly associated with Down syndrome?
complete atrioventricular (AV) canal defect: compromised of atrial septal defect + ventricular septal defect + common AV valve
due to failure of endocardial cushion fusion —> ostium primum ASD + VSD + common AV valve
L to R shunting and AV valve regurgitation cause excessive pulmonary blood flow and heart failure —> auscultation will reveal hyperdynamic precordium + mid-diastolic rumble at LSB (increased pulmonary venous return) + holosytolic murmur in apex that radiates to the axilla (AV valve regurgitation)
