Perfusion Flashcards
Electrical Conduction of the Heart
"action potential"=electrical impulse SA (sinoatrial) node (P wave) Internodal Tract Right and Left Atria (contract) AV (atrioventricular) Node Bundle of HIS Bundle Branches Purkinje Fibers Ventricle (Contract)
Absolute Refractory Period
Cardiac muscle does not respond to any stimuli during ventricular contraction
Relative refractory period
After absolute refractory when cardiac muscle gradually recovers its excitability (by early distole)
ECG Waves
P-1st, firing of SA node, depolarization of the atria
QRS-2nd, depolarization from AV throughout ventricles
T-3rd, repolarization of the ventricles
U-4th repolarization of Purkinje fibers, or hypokalemia
Intervals between each wave reflect the time it takes for the impulse to travel from one area to another.
ECG lead placement
5 Lead
RA-right arm, on cx where arm/torso meet RL-Left arm, on cx where arm/torso meet RL-Right leg, on abd near hip LL-Left leg, on abd near hip C1-(for V1) 4th IC, rt sternal border
P wave normal
0.06-0.12
firing of SA node, depolarization of atria (contract)
longer: conduction problem within atria or SA node
QRS wave normal
0.04-0.12
depolarization of AV through ventricles (contract)
longer-conduction problem in branches
T wave normal
0.16
repolarization of ventricles
longer: MI or ischemia
inverted: old MI injury
MAP formula
MAP = (SBP + 2(DBP)) / 3
depolarization
contraction
repolarization
rest
ST interval
0.12
MI
elevated = STEMI
PR interval
0.12-0.20
conduction problem AV, bundle of his, bundle of branches, atria
QT interval
0.34-0.44
ventricular Repolarization disturbances
Sinus Bradycardia
Sinus Tachycardia
> 100 bpm
Causes: normal response to increased activity, anxiety, pain, stress, fear, fever, anemia, hypoxemia, hyperthyroidism, pulmonary embolism, decrease cardiac ouput/hypotension, hypovolemic shock, MI, heart failure
caffeine, drugs, alcohol, nicotine
Sx: Decreased blood pressure, Decreased Cerebral perfusion=restlessness, anxiety, confusion, Decreased oxygen saturation, Weakness, Fatigue, Shortness of breath, Decreased urine output, Pain, Palpitations, Orthopnea
Tx: fix the cause!
Sinus Arrhythmia
Ps and Rs irregular
breathing and meds: Morphine, digoxin
asymptomatic
Cardiac output formula
HR x stroke volume = CO
Pathophysiology of PVD
leading cause is atherosclerosis, gradual thickening of intima (innermost layer) and media (middle layer) of the arterial wall from deposit of cholesterol and lipids. also: inflammation and endothelial injury.
collateral circulation develops
mostly affects parts of arterial tree and lower extremity arteries
Plaque develops arterial bifurcations
Symptoms develop when the vessel is occluded by 60% or more
PVD risk factors
tobacco, DM, hyperlipidemia, elevated C-reactive protein, uncontrolled HTN
other factors: family hx, age, gender, hypertriglyceridemia, obesity, sedentary lifestyle, stress, men, cholesterol >240
S/Sx of PVD
Intermittent pain/ cramping with activity [claudication] Rest pain – burning sensation in legs Numbness, decreased sensation Diminished or absent peripheral pulses Extremity pallor with elevation Extremity dark red when dependent Thin, shiny and lack of hair on skin Thickened toenails Skin areas of discoloration Skin breakdown
Treatment for PVD
Clinical therapies: Smoking cessation Meticulous foot care Support hose Exercise [walk 30-60m, 3-5x week; walk until pain, rest, then walk again until pain for 30min] Rest for pain BMI
2 priority education topics for PVD
Smoking cessation
DM control, foot care
lipid mgt -statins [lipid-lowering agent; lowers LDL & triglycerides]
HTN [thiazides, ACE-inhibitors, lifestyle changes]
two priority nursing diagnoses for PVD
ineffective tissue perfusion
impaired skin integrity
risk for falls
atropine
–
beta blockers
-olol slows HR, reduces workload angina, BP, HF, heart attack drowsy, fainting, swelling, bradycardia blocks negative effects of SNS watch BP
Ca channel blockers
-VND (vera nifed dilti)
decreases demand for O2 by lowering contractility and conductivity of the heart//relaxes blood vessels
bradycardia, constipation, edema
lipid-lowering agents
–
muscle pain, soreness, GI upset
complications with PVD
gangrene, limb amputation, infection, sepsis
Types of PVD
asymptomatic [found at dr]
intermittent claudication [pain upon activity]
critical limb ischemia [rest pain, tissue loss]
anticoagulants
warfarin, heparin
antihypertensives
–
orthostatic hypoTN, don’t stop abruptly!
antiplatelets
aspirin, clopidogrel
segmented BP
used to check peripheral pulses with doppler
thigh, below knee, ankle
drop in segBP >30 suggests PVD
Ankle Brachial Index
ABI
uses doppler
divides the ankle Systolic BP by the higher of the Lt and Rt brachial Systolic BPs
NOTE: elderly and DM pts-falsely elevated ABIs due to calcification of arteries
DON’T do immediately after revascularization or on distall bypass grafts [risk of graft thrombosis]