Cardiac Flashcards
Left coronary artery: origins
Left aortic sinus
Right coronary artery: origins
right aortic sinus
Left coronary artery branches
Left anterior descending (LAD)
Left marginal artery
Left circumflex artery
Right coronary artery branches
Right marginal artery
Posterior interventricular artery
Left anterior descending
Areas: Right ventricle
Left ventricle
Interventricular septum
ECG: V1-V4 (anterior MI)
Left circumflex artery
Areas: Left atrium and ventricle
ECG: I, aVL, V5, V6 (anterolateral)
Left marginal artery
Areas: left ventricle
ECG: lateral (I, aVL), posterior (V7-9, ST depression V1-3), inferior: 10% (II, aVF, III)
Right coronary artery
Areas: right atrium, right ventricle
Sinoatrial node (60%), Atrioventricular node (90%)
ECG: Inferior (II, III, aVF), bradycardia (2nd/3rd degree heart block)
Right marginal artery
Areas: right ventricle and apex
Posterior inter ventricular artery
Areas: right and left ventricles, inter ventricular septum (posterior 1/3)
Venous drainage of the heart
Drains into coronary sinus: Great cardiac vein Small cardiac vein Middle cardiac vein Posterior cardiac vein
Drains directly into right atrium:
Anterior cardiac veins
Cardiac conduction system
Sinoatrial node
Atrioventricular node
Atrioventricular bundle (bundle of His)
Purkinje fibres
Heart conduction
Creates excitation potentials
Wave of excitation spreads across atria causing atrial contraction
Reaches AV node, signal is delayed
Conducted into bundle of His down inter ventricular septum
Purkinje fibres spread wave impulses along ventricles causing them to contract
Sinoatrial node
Specialised cells. Located in upper wall of right atrium. Can spontaneously generate impulses.
Sympathetic: increases firing of SA
Parasympathetic: decreases firing of SA
Atrioventricular node
Delays impulses to ensure full atrial contraction
Atrioventricular bundle (bundle of His)
Continuation of specialised tissue of AV node. Transmits electrical impulse from AV node to Purkinje fibres.
Descends down membranous part of septum before dividing into right bundle branch and left bundle branch
Phases of cardiac action potential
Phase 0 - 4 Phase 0: Na in Phase 1: K/Cl out Phase 2: Ca in Phase 3: K out Phase 4: K rectifies
Drugs and where they act in the cycle
Phase 0: Na in (Na channel blocker: lidocaine, phenytoin, flecanide)
Phase 1: K/Cl out
Phase 2: Ca in (Calcium channel blocker: Diltiazem, verapamil)
Phase 3: K out (K channel blocker: amiodarone)
Phase 4: K rectifies (beta blocker: propanolol)
Foetal circulation adaptations
Umbilical arteries and vein Ductus venosus (left portal vein to IVC) Foramen ovale (right to left atrium) Ductus arteriosus (pulmonary artery to aorta)
Foetal circulation in utero
Gas exchange at placenta
O2 blood travels via umbilical vein to liver. Right umbilical vein provides liver with O2 blood. Left umbilical vein branches into ductus venosus, bypassing straight to IVC.
Mixed blood (O2 from LUV and deO2 from body) enters right atrium.
Pulmonary arterioles are hypoxic causing vasoconstriction increasing vascular resistance. Generates right to left shunt.
Blood preferentially shunts to left via ductus arteriosus and foramen ovale.
Internal iliac arteries given rise to umbilical artery, carrying deO2 blood to placenta.
Foetal circulation after birth
After birth, air flows into lungs. Results in significant rise in O2 levels.
Pulmonary vascular resistance falls after reduction in hypoxic vasoconstriction
Changes in pressure gradients cause closure of foramen ovale and shift in blood flow across ductus arteriosus.
As O2 rises, smooth muscle wall of ductus arteriosus contracts, closing completely.
Umbilical vessels constrict forming round ligament of liver, ligamentum venous, superior vesical arteries.
Ventricular septal defect (VSD)
Acyanotic.
Pansystolic murmur LLSE
L to R shunt, pulmonary HTN, RV hypertrophy, can develop shunt reversal.
Causes: foetal alcohol, Down’s (21), Edward’s (18), Patau’s (13)
Rx: surgical repair
Persistent ductus arteriosus
Acyanotic.
Continuous ULSE “Gibson’s” murmur
Kept patent by Prostaglandin in utero.
Causes left to right shunt, SOB, HF, cyanotic lower extremities (Eisenmenger’s Syndrome)
Patent foramen ovale/Atrial septal defect
Acyanotic.
Split S2 with ejection systolic murmur ULSE
Left to right atrial shunt.
Causes: Down’s (21), foetal alcohol syndrome
HF, SOB, recurrent chest infections, paradoxical embolus.
Rx: surgery w. patch/plug
Tetralogy of Fallot
Cyanotic. (Tet spells)
1. Narrowing of RV outflow tract (PV stenosis)
2. RV hypertrophy
3. Ventricular septal defect
4. Aorta overrides septal defect
Causes: Chromosome 22 deletion, DiGeorge syndrome
Rx: VSD repair, pulmonary stenosis widening
Transposition of great vessels
Cyanotic.
Aorta attached to RV, pulmonary artery attached to LV. 2 parallel circuits created.
Causes: maternal DM.
Rx: maintain ductus arteriosus with prostaglandins. Surgery.
Coarctation of aorta
Acyanotic
Ejection systolic murmur left infraclavicular area. Weak or absent femoral pulses
Rx: conservative or resection if severe.