Heart Arteries, Veins, Action Potential Phases, Pacemaker Cell Properties, Interval Times, Myocardial Infarctions, and Axis Deviation

Right Coronary Artery

emerges from the aorta, descends through the AV groove

descends downward and towards the posterior surface of the heart

supplies oxygenated blood from the aorta to the right atrium / right ventricle and SA / AV nodes

Left Main Coronary Artery

emerges from the aorta

passes between the pulmonary trunk and the left atrial appendage, part of the left atrium

divides into Left Anterior Descending (LAD) and Left Circumflex

supples oxygenated blood from the aorta to left atrium / left atrial appendage, pulmonary artery, and aortic root

Left Anterior Descending (LAD)

direct continuation of the Left Main

supplies oxygenated from the aorta to the interventricular septum, anterior / lateral / apical wall of the left ventricle, some of the right ventricle, most of the bundle branches

Left Circumflex

direct continuation of Left Main

supplies oxygenated blood from aorta to most of the left atrium, posterior / lateral walls of the left ventricle, and sometimes SA node

Coronary Sinus Vein

lies on the posterior surface of the heart runs along coronary sulcus before emptying directly into the right atrium

runs along the AV groove

Great Cardiac Vein

arises from the apex of the heart, course up anterior surface along anterior interventricular groove, turns and courses around left side along coronary sulcus before emptying into coronary sinus on posterior surface

runs along side of the Left Anterior Descending (LAD)

Small Cardiac Vein

arises from right margin of heart and courses along coronary sulcus before emptying into the coronary sinus

Middle Cardiac Vein

arises from apex and courses up posterior surface along posterior interventricular groove before emptying into the coronary sinus

Automaticity

is the ability of cardiac cells to generate their own impulses spontaneously

Excitability

is the ability of cardiac cells to respond to an electrical stimulus

Conductivity

is the ability of cardiac cells to transfer or propagate an electrical stimulus

Contractility

is the ability of cardiac cells to shorten and cause myocardial contractions in response to an electrical stimulus

calcium is the main driver

Action Potential Phase 0 Depolarization

rapid influx of Na+

K+ moves out of cell

sharp rise in action potential curve

onset of QRS on the ECG

Action Potential Phase 1 Initial Rapid Repolarization

closure of fast Na+ channels

Phase 0 & 1 corresponds to QRS

corresponds to systole in cardiac cycle

Action Potential Phase 2 Plateau Phase

inward movement of Ca++

outward movement of K+

longer duration than phase 1

corresponds to ST segment on the ECG

Action Potential Phase 3 Repolarization

K+ builds up outside cell, causing repolarization

C++ channels close

corresponds to T wave on ECG

Action Potential Phase 4 Resting Phase

resting membrane potential

polarized state cell maintains until next stimulation

associated with diastole in the cardiac cycle

corresponds to isoelectric line or baseline in ECG

PR Interval

120 - 200 ms is 3 - 5 small boxes

measured from onset of the P wave to the onset of the first deflection of the QRS

QRS Interval

40 - 100 ms is 1 - 3 small boxes

measured from the first deviation from the baseline to the return of the waveform to the baseline

QT Interval

<400 ms

measured from the beginning of the QRS to the end of the T wave

Inferior Wall MI

involves diaphragmatic surface of the heart

often result of occluded RCA or its descending branch

view in lead II, III, aVF

STEMI

Anterior Wall MI

involves the anterior surface of the left ventricle

often due to occlusion of the LAD

views in V1 - V6

STEMI

Posterior Wall MI

large area of the myocardium is on the posterior side

views in V1 - V3

ST depression

N-STEMI

Subendocardial MI

STEMI

Transmural MI

Left Axis Deviation

left ventricular hypertrophy

left bundle branch block

previous inferior wall MI

Right Axis Deviation

right ventricular hypertrophy

left posterior fascicular block

previous lateral wall MI

Right Bundle Branch Block

V1 is rSR’

V6 is sure or widened S also qRs

Left Bundle Branch Block

V1 is deep S wave

V6 is notched R wave