Cardiovascular Physiology and Pharmacology 1

Cardiac Conduction System

• sinoatrial node
• arterio-ventricular node
• His (L and R) bundle branches
• Perkinje fibers (depolarize ventricle from base to apex)

Coronary Anatomy

• RCA supplies RA, RV, portion of LV inferior wall
• “Right dominant circulation” = RCA giving rise to Posterior Descending Artery (PDA)
• PDA supplies posterior-superior interventricular septum and inferior wall of LV
• Left Main Coronary Arter (LMCA) supplies left atrium, most IV septum, LV (except posterior) walls
• LMCA divides into Left Anterior Descending (LAD) and Left Circumflex Artery
• SA node supplied by RCA (60%)
• SA node supplied by LAD (40%)
• AV node supplied by RCA (90%)
• AV node supplied by circumflex (10%)
• Bundle of His supplied by both PDA and LAD
• Coronary blood flow = 250cc/min (5% of CO)
• Mycardium extracts >65% of oxygen from blood

Detecting Cardiac Ischemia

• Inferior = II, III, aVF
• Lateral = I, aVL, V5, V6
• Anterior = V3, V4
• Lead most sensitive to MI = V5 (75%)
• Best TEE view to see ischemia = transgastric short-axis view because it visualizes all 3 major coronary territories
  • RCA = mid-septal and inferior
  • Circumflex = posterior and lateral
  • LAD = anteroseptal and anterior

Cardiac Innvervation

• Sympathetic input from brainstem to SA/AV nodes via stellate ganglion
• Cardioaccelerators T1-T4
• Parasympathetic (vagal) input from nucleus ambiguous in medulla
• R-sided autonomics to SA node
• L-sided autonomics to AV node

Transplanted Heart

• transplanted heart has no parasympathetic connections
• transplanted hears have no T1-T4 sympathetic connections
• norepinephrine in transplanted heart lacks reflex decrease in HR
• changes in CO can thus only occur via change in SV (not HR)

Cellular Anatomy of the Heart

• T-tubules: membrane invaginations allow depolarization of deep cell interior
• Sarcoplasmic reticulum: Ca reservoir
• Gap junctions: cells in electrical continuity

Cardiac Electrophysiology

Random Facts

• infarcted right coronary leads to bradycardia
• ligamentum arteriosum is the adult remnant of ductus arteriosus