Question | Answer |
Automaticity | The cell's ability to spontaneously initiate an impulse |
Excitability | indicates how well a cell responds to an electrical stimulus |
Conductivity | how well the cell contracts after receiving a stimulus |
Electrical activity | precedes mechanical activity |
Mechanical activity | cannot occur without electrical activity |
Electrical activity can occur | without being followed by mechanical activity |
EKG | a graphic recording of the electrical activity generated by the functioning heart. |
EKGs help to identify | Primary conduction abnormalities, dysrhythmias, cardiac hypertrophy, pericarditis, electrolyte imbalances, MI - site & extent |
SA Node | The hearts main pacemaker 60-100 BPM |
SA Node location | right atrium near the superior vena cava |
AV Node location | lower part of right atria near the tricuspid valve |
AV Node delays cardiac impulses for | protection of ventricles against excessively high atrial rates; allows atria to contract and empty blood into ventricle at end of diastole (atrial kick) |
Tissue surrounding AV Node | contains pacemaker cells that fire at 40-60 BPM |
Bundle of HIS | located in septum between the 2 ventricles |
Purkinje Fibers | Terminal portion of the conduction system, third pacemaker 20-40 BPM |
Atria | Low pressure chambers, reservoirs for respective ventricles |
Right ventricle | low pressure chamber, sends deoxygenated blood to lungs |
Left ventricle | high pressure chamber, send oxygenated blood to body |
Tricuspid valve | AV valve between right atrium & right ventricle |
Mitral valve | AV Valve between left atrium & left ventricle |
Atrioventricular (AV) Valves | Tricuspid & Mitral, unidirectional, closure produces S1 (Lub) sound |
Semilunar Valves | Pulmonic & Aortic, unidirectional, closure produces S2 (dub) sound |
Pulmonic valve | Between right ventricle and pulmonary artery |
Aortic valve | Between left ventricle and aorta |
Depolarization | discharge of energy that accompanies the transfer of electricle charges across the cell membrane |
Repolarization | return of electrical charges to their original state of readiness |
Baseline | a starting or resting line of the EKG |
Wave | a deflection from the baseline |
Biphasic | a deflection wtih both positive and negative components |
P Wave | first deflection; represents atrial depolarization |
PR interval | from the beginning of the P wave to the onset of the Q wave; represents conduction of the impulse through the atria to the AV node (0.12 - 0.2 seconds) |
QRS Complex | represents ventriclular depolarization; 0.06 - 0.12 seconds |
ST Segment | End of S wave to beginning of the T wave |
PR interval too long | > 0.2 seconds; indicates AV block |
PR interval too short | <0.12 seconds; junctional rhythm |
T wave | Repolarization of the ventricles |
QRS Complex too long | >0.12 seconds; something slowing conduction; could be caused by bundle branch block, hypertrophied ventricle |
ST Segment depression (below baseline) | hypoxia, ischemia, electrolyte issues, healing MI |
ST segment elevation (above baseline) | Infarction (MI) |
QT Interval | beginning of Q wave to end of T wave; 0.36 - 0.44 seconds |
T wave tall & tented | Hyperkalemia |
T wave shape | should be upright and slightly rounded |
QT Interval >0.44 seconds | BAD; puts pt at risk of developing V-tach or toursades |
Normal heart rate | 60-100 BPM |
Tachycardia | >100 BPM |
Bradycardia | <60 BPM |
Cardiac Output | Stroke volume X Heart Rate |
Sinus Tachycardia Interventions | Treat the cause; rest, oxygen, analgesics, fluids, diuretics, beta-blockers, digoxin |
Causes of Sinus Tachycardia | CHF, hypovolemia, hypotension, anemia, exercise, fever, hypoxia, pain, anxiety, hyperthyroidism, pulmonary embolism, AWMI, response to drugs that stimulate heart, alcohol, caffeine, nicotine |
Causes of Sinus Bradycardia | Athletes with well conditioned hearts, digitalis, beta blockers, calcium channel blockers, sleep, elevated ICP, inferior wall MI, vagal stimulation caused by vomitting or severe pain, hypothyroidism, hypothermia |
Sinus Bradycardia Interventions | Identify underlying cause; If symptomatic - Atropine, pacemaker, dopamine |
Causes of PACs | Coronary and valvular heart disease, dig toxicity, hyperthyroidism, elevated catecholamine levels, acute respiratory failure, COPD, fatigue, anxiety, electrolyte imbalances, ischemia, MI, early CHF, alcohol, nicotine, caffeine |
PAC interventions | If symptomatic, focus on eliminating the cause or may treat with antiarrhythmics |
Causes of Atrial Fibrillation | Valvular disorders, hypertension, CAD, MI, cardiomyopathy, COPD, CHF, rheumatic heart disease, hyperthyroid, dig intoxication |
Interventions for Atrial Fibrillation | Control (slow) rate and improve cardiac output. If symptomatic - syncronized cardioversion. Diltiazem, Verampamil, Digoxin, beta blockers to slow conduction through AV node. Other anti-arrhythmic drugs once ventricular response controlled. |
Danger of Atrial Fibrillation | Stroke - clot forms and breaks loose, anticoagulant therapy unless contraindicated (heparin/coumadin) |
Interventions for Ventricular Tachycardia in consious stable patient | order 12 lead EKG to determine type of tachycardia |
Interventions for Ventricular Tachycardia in unstable patient | Call for help, Start CRP, Immediate synchronized cardioversion followed by drug therapy |
Interventions for Ventricular Tachycardia in pulseless patient | ACLS - shock, CPR for 2 minutes, shock & vasopressors, shock and antiarrhythmic (amiodarone, lidocane, magnesium) |
Ventricular Tachycardia | Lethal dysrhythmia - Assess pt, call for help, start CPR |
Ventricular Fibrillation (V Fib) Interventions | Assess Pt, call for help, start CPR, Code Cart/ACLS |
Causes of V Fib | MI, Myocardial ischemia, hypokalemia, hyperkalemia, hypercalcemia, cocain toxicity, hypoxia, hypothermia, acid-base imbalance, electric shock |
Asystole Interventions | Assess, call code, CPR, intubate, O2, Vasopressin, epinephrine, atropine, pacemaker (confirm in more than 1 lead) |
Causes of asystole | Severe metabolic deficit, acute respiratory failure, MI, severe electrolyte disturbances, massive pulmonary embolism, electric shock, cocaine OD |
Asystole | Flatline - ventricular standstill - no electrical activity, no contraction, no cardiac output |
Ventricular Fibrillation | Lethal Rhythm - rapid disorganized depolarizations of the ventricles characterized by a lack of organized electrical impulse, conduction and ventricular contraction. |