USMLE (Fach) / Cardiovascular (Lektion)

USMLE First Aid

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• Separation of the atria 1. Septum primum grows toward endocardial cushions (narrowing foramen primum) 2. Foramen secundum forms in septum primum (formamen primum disappears) 3. Septum secundum develops as foramen secundum maintains ...
• Patent foramen ovale - caused by failure of septum primum and septum secundum to fuse after birth - most are left untreated - can lead to paradoxical emboli (venous thromboemboli that enter systemic arterial circulation)
• Fetal-postnatal derivatives Allantois → urachus → Median umbilical ligament- Urachus is part of allantoic duct between bladder and umbilicus Ductus arteriosus → Ligamentum arteriosum Ductus venosus (bypasses hepatic circulation) ...
• Splitting Normal splitting:- Inspiration → drop in intrathoracic pressure → ↑ venous return → ↑ RV filling → ↑ RV stroke volume → ↑ RV ejection time → delayed closure of pulmonic valve. ↓ ...
• Aortic stenosis Crescendo-decrescendo systolic ejection murmur and soft S2 (ejection click may be present). - LV >> aortic pressure during systole. Loudest at heart base; radiates to carotids.- Murmur louder with ↑ ...
• Mitral/tricuspid regurgitation - Holosystolic, high-pitched "blowing murmur."- Severity is indicated by an audible S3 gallop. Mitral - loudest at apex and radiates toward axilla.- MR is often due to ischemic heart disease (post-MI), ...
• Mitral valve prolapse Late systolic crescendo murmur with midsystolic click (MC; due to sudden tensing of chordae tendineae). - Most frequent valvular lesion, usually benign.- Best heard over apex. Loudest just before S2.- ...
• Ventricular septal defect Holosystolic, harsh-sounding murmor.- Loudest at tricuspid area. Most common congenital cardiac defect.- Asymptomatic at birth, may manifest weeks later or remain asymptomatic throughout life.- Most self ...
• Aortic regurgitation Etiologies:- Congenital bicuspid aortic valve- Postinflammatory (eg, rheumatic heart disease, endocarditis)- Aortic root dilation (eg, Marfan syndrome, syphilis) Clinical findings:- High-pitched "blowing" ...
• Mitral stenosis - Follows opening snap (OS; due to abrupt halt in leaflet motion in diastole, after rapid opening due to fusion at leaflet tips). - Delayed rumbling mid-to-late diastolic murmur (↓ interval between ...
• Patent ductus arteriosus In fetal period, shunt is right to left (normal). In neonatal period, ↓ pulmonary vascular resistance → shunt becomes left to right → progressive RVH and/or LVH and HF. - Continuous, "machine-like" ...
• Torsades de pointes Polymorphic ventricular tachycardia, characterized by shifting sinusoidal waveforms on ECG- Can progress to ventricular fibrillation (VF). Cause:- Long QT interval predisposes to torsades de pointes- ...
• Congenital long QT syndrome Inherited disorder of myocardial repolarization, typically due to ion channel defects.- Most common forms are due to genetic mutations in K+ channel proteins that contribute to the outward-rectifying ...
• Brugada syndrome - Autosomal dominant disorder most common in Asian males.- Affects sodium channels and disturbs repolarization. - ECG pattern of pseudo-right bundle branch block and ST elevations in V1-V3. - ↑ risk ...
• Wolff-Parkinson-White syndrome - Most common type of ventricular pre-excitation syndrome. - Abnormal fast accessory conduction pathway from atria to ventricle (bundle of Kent) bypasses the rate-slowing AV node → ventricles begin ...
• Atrial fibrillation - Chaotic and erratic baseline with no discrete P waves in between irregularly spaced QRS complexes.- Ventricular response is dependent on the transmission through the AV node, and thus, the AV node refractory ...
• Atrial flutter A rapid succession of identical, back-to-back atrial depolarization waves - "Sawtooth" appearance of the flutter waves. - Treat like atrial fibrillation. Definitve treatment is catheter ablation.
• Right-to-left shunts Early cyanosis ("blue babies"). Often diagnosed prenatally or become evident immediately after birth. Usually require surgical treatment and/or maintenance of a PDA. 1. Truncus arteriosus2. Transposition ...
• Persistent truncus arteriosus Truncus arteriosus fails to divide into pulmonary trunk and aorta due to lack of aorticopulmonary septum formation. Most patients have accompanying VSD.
• Transposition of great vessels Aorta leaves RV (anterior) and pulmonary trunk leaves LV (posterior) → separation of systemic and pulmonary circulations.- Due to failure of the aorticopulmonary septum to spiral. - Not compatible ...
• Tricuspid atresia Absence of tricuspid valve and hypoplastic RV. Requires both ASD and VSD for viability.
• Tetrology of Fallot Caused by anterosuperior displacement of the infundibular septum.- Most common cause of early childhood cyanosis. 1. Pulmonary infundibular stenosis (most important determinant for prognosis)2. Right ...
• Ebstein anomaly Characterized by the displacement of tricuspid valve leaflets downward into RV, artificially "atrializing" the ventricle. - Associated with tricuspid regurgitation, accessory conduction pathways, and ...
• Eisenmenger syndrome Uncorrected left-to-right shunt (VSD, ASD, PDA) → ↑ pulmonary blood flow → pathologic remodeling of vasculature → pulmonary arterial hypertension. - RVH occurs to compensate → shunt becomes ...
• Coarctation of the aorta Aortic narrowing near insertion of ductus arteriosus ("juxtaductal").- Associated with bicuspid aortic valve, other heart defects, and Turner syndrome. - Hypertension in upper extremities and weak, delayed ...
• Congenital cardiac defect associations Alcoholic exposure in utero → VSD, PDA, ASD, tetralogy of Fallot Congenital rubella → PDA, pulmonary artery stenosis, septal defects Down syndrome → AV septal defect (endocardial cushion defect), ...
• Hypertension Defined as persistent systolic ≥140 mmHg and/or diastolic BP ≥90 mmHg. Risk factors: ↑ age, obesity, diabetes, physical inactivity, excess salt intake, excess alcohol intake, cigarette smoking, ...
• Diagnosis of myocardial infarction - In the first 6 hours, ECG is the gold standard. - Troponin I rises after 4 hours (peaks at 24 hr) and is ↑ for 7-10 days; more specific than other protein markers. - CK-MB rises after 6-12 hours ...
• Myocardial infarction complications Cardiac arrhythmia: Important cause of death before reaching hospital and within the first 24 hours post-MI. Postinfarction fibrinous pericarditis: Occurs 1-3 days after MI. Friction rub. Papillary muscle ...
• Dilated cardiomyopathy Most common cardiomyopathy (90% of cases). - Most often idiopathic or familial (50%).- Coronary or valvular heart disease- Chronic alcohol abuse- Wet beriberi (thiamine deficiency)- Coxsackie B viral ...
• Hypertrophic obstructive cardiomyopathy 60-70% of cases are familial, autosomal dominant (commonly due to mutations in genes encoding sarcomeric proteins, such as myosin binding protein C and β-myosin heavy chain).- Can be associated with ...
• Restrictive/infiltrative cardiomyopathy Major causes include:- Sarcoidosis- Amyloidosis- Postradiation fibrosis- Endocardial fibroelastosis (thick fibroelastic tissue in endocardium of young children)- Hemochromatosis (although dilated cardiomyopathy ...
• Heart failure Clinical syndrome of cardiac pump dysfunction → congestion and low perfusion.- Symptoms include dyspnea, orthopnea, fatigue.- Signs include S3 heart sound, rales, jugular venous distention (JVD), pitting ...
• Left heart failure Orthopnea – Shortness of breath when supine: ↑ venous return from redistribution of blood (immediate gravity effect) exacerbates pulmonary vascular congestion. Paroxysmal nocturnal dyspnea – Breathless ...
• Right heart failure Hepatomegaly (nutmeg liver): ↑ central venous pressure → ↑ resistance to portal flow. Rarely, leads to "cardiac cirrhosis." Jugular venous distention: ↑ venous pressure. Peripheral edema: ↑ ...
• Bacterial endocarditis Acute – S aureus (high virulence). Large vegetations on normal valves. Rapid onset.Subacute – viridans streptococci (low virulence). Smaller vegetations on congenitally abnormal or diseased valves. Sequelae ...
• Rheumatic fever A consequence of pharyngeal infection with group A β-hemolytic streptococci.- Late sequelae include rheumatic heart disease, which affects heart valves – mitral > aortic >> tricuspid (high-pressure ...
• Acute pericarditis Inflammation of the pericardium Etiologies:- Infectious: Most commonly viral (eg, coxsackie), bacterial (eg, tuberculosis), toxoplasmosis- Myocardial infarction: within 1-3 days → post-infarction fibrinous ...
• Kussmaul sign - ↑ in JVP on inspiration instead of a normal ↓. - Inspiration → negative intrathoracic pressure not transmitted to heart → impaired filling of right ventricle → blood backs up into venae ...
• Cardiac tamponade Compression of the heart by fluid (eg, blood, effusions in pericardial space) → ↓ CO.- Equilibration of diastolic pressures in all 4 chambers. Findings:- Beck triad: Hypotension, distended neck veins, ...
• Pulsus paradoxus ↓ in amplitude of systolic BP by > 10 mm Hg during inspiration Seen in:- cardiac tamponade- asthma- obstructive sleep apnea- pericarditis- croup
• Heart embryology Truncus arteriosus → Ascending aorta and pulmonary trunk Bulbus cordis → Smooth parts (outflow tract) of left and right ventricles Endocardial cushion → Atrial septum, membranous intraventricular ...
• Heart morphogenesis First functional organ in vertebrate embryos; beats spontaneously by 4 weeks of development. Cardiac looping: Primary heart tube loops to establish left-right polarity; begins in week 4.- Defect in left-right ...
• Fetal circulation Blood in umbilial vein has a PO2 of ~30 mmHg and is ~80% saturated with O2. Umbilical arteries have low O2 saturation. 3 important shunts:1. Blood entering fetus through the umbilical vein is conducted ...
• Anatomy of the heart SA node is commonly supplied by right coronary artery (RCA); AV node supplied by PDA. Infarct may cause nodal dysfunction (bradycardia or heart block). Right-dominant circulation (85%): Posterior descending ...
• Cardiac output CO = stroke volume (SV) x heart rate (HR) Fick principle:CO = rate of O2 consumption/(arterial O2 content - venous O2 content) - During the early stages of exercise, CO is maintained by ↑ HR and ↑ ...
• Cardiac output variables Stroke volume ↑ with: ↑ contractility, ↑ preload, ↓ afterload Preload: approximated by ventricular end-diastolic volume (EDV)- Depends on venous tone and circulating blood volume.- Venous ...
• Contractility Contractility (and SV) ↑ with:- Catecholamine stimulation via β1 receptor: → Ca2+ channels phosphorylated → ↑ Ca2+ entry → Ca2+ induced Ca2+ release and ↑ Ca2+ storage in sarcoplasmic ...
• Starling curve Force of contraction is proportional to end-diastolic length of cardiac muscle fiber (preload). ↑ contractility with catecholamines, positives inotropes (eg, digoxin). ↓ contractility with loss of ...
• Heart sounds S1 – mitral and tricuspid valve closure. Loudest at mitral area. S2 – aortic and pulmonary valve closure. Loudest at upper sternal border. S3 – in early diastole during rapid ventricular filling ...

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