ECG and AFib

atrial fibrillation

arrhythmia of the atria

AFib complications

blood clots, stroke, heart failure

AFib prevalence

2\.7 million in U.S.

AFib symptoms

irregular heartbeat, general fatigue, syncope, “fluttering”, shortness of breath, anxiety, and diaphoresis

AFib etiology

atrial fibrosis (accumulation of tissue in atrium) leading to loss of muscle mass

AFib risk factors

valve disease (AV valve); pulmonary embolism; heart failure; myocarditis and pericarditis; stroke; myocardial infarction

bipolar lead

measuring voltage difference b/w two leads

dipole in heart is caused by…

partial depolarization

Einthoven’s triangle

right hand, left hand, left leg (right leg is ground)

what increases ECG magnitude

electrically contiguous tissue an large masses

P Wave

atrial depolarization

Q Wave

ebund branches and septum depolarize

in Q wave, depolarization proceeds from…

left ventricle to septum to right ventricle

R wave

ventricles depolarize; atria repolarize

S wave

final ventricular depolarization

T wave

ventricular repolarization

the ventricle repolarizes from the…

epicardium to the endocardium

ECG lead number

12

ventricular leads

V1-V6; measures voltage diff. on transverse plane

augmented leads

aVL, R, F

QRS complex

ventricular depolarization

P-R interval

transit time from SA node through the AV node

R-R interval

1/heart rate

S-T segment

entire ventricle is depolarized

Q-T interval

beginning to end of ventricular depolarization

the P wave is followed by…

atrial contraction

the QRS complex is followed by…

ventricular contraction

the T wave is followed by…

ventricular relaxation

closure of AV valves is followed by…

a hollow sound (“lub”)

closure of SL waves is followed by…

a small, sharp tap (“dub”)

fibrillation

cardiac muscle re-excites itself after refractory period in neighboring tissue

ectopic focus

AP begins somewhere besides nodes

ectopic beats happen from…

ischemia, calcified heart valves, injuries, and fibrosis

ischemia

lack of blood flow

result of calcified heart valves

irritates myocardium surrounding heart valves

atrial fibrillation

random depolarization of atrial muscle; QRS complexes are random; tachycardia

ventricular fibrillation

random depolarization of ventricles; ventricle quivering; hear unable to pump

defibrillation

large electric field for complete myocardium depolarization so that rhythm resumes from SA node, not ectopic focus

drugs that control HR

propranolol, diltiazem

anti-coagulant therapy

reduces likelihood of blood clots developing around valves

implantable cardiac defibrillators

only used with high risk of VFib; can increase risk of death