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55 Cards in this Set

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Phases of action potential: Phase 0
Rapid sodium entry (depolarization)
Phases of action potential: Phase 1
Transient potassium efflux, some chloride entry (repolarization)
Phases of action potential: Phase 2
Calcium entry (plateau)
Phases of action potential: Phase 3
Potassium efflux (rapid repolarization)
Phases of action potential: Phase 4
Resting membrane potential
Absolute refractory period
No action potential can occur no matter how great the impulse
Relative refractory period
Action potential can occur if impulse is of certain magnitude
What is the relationship of the ventricular action potential to the ECG?
Influx of sodium into perkinje cells (Phase 0) corresponds to QRS complex. Slow phase 0 means wide QRS complex, whereas fast conductance means narrow QRS complex. T-wave depends on speed of ventricular repolarization. The longer the refracatory period, the longer the distance between QRS and T-wave.
What are the mechanisms of arrhythmias?
1. altered automaticity
2. reentry
What are the mechanisms of altered automaticity?
1. slowed diastolic depolarization
2. production of diastolic hyperpolarization
3. increased threshold level
4. dominance of ectopic pacemaker
What are the characteristics required for reentry?
1. loop
2. unidirectional block
3. slow conduction
4. different refractory periods
What are the signs and symptoms of arrhythmias?
1. palpitations
2. cardiac awareness
3. syncope/presyncope
4. hemodynamic compromise
What is sinus tachycardia?
Rapid heartbeat <100 bpm. (disorder of AV node.) T and P waves are closer together. Hemodynamic consequences: nothing in normal people, angina in people with coronary disease.
What is sinus bradycardia?
Slow heartbeat <60 bpm. Often happens in runners. Hemodynamic consequences: usually asymptomatic, may cause lightheadedness.
What are the types of premature atrial depolarizations?
1. Abberent conduction (irregular)
2. Atrial flutter
3. Atrial fibrillation
4. Paroxysmal AV nodal reentry
What is abberant conduction?
Irregular premature atrial depolarization where the next P-wave occurs too soon. Usually due to ectopic pacemaker in atria. Often occurs normally ("skipped beat"), no hemodynamic consequences.
What is atrial flutter?
Irregular premature atrial depolarizations caused by a series of reentry circuits in atrium. Saw-tooth pattern, P-waves do not all produce QRS complexes. Hemodynamic consequences depend on ventricular rate that is produced; may have no symptoms
What is atrial fibrillation?
Most common rhythmic disturbance. Irregularly irregular b/c no underlying rhythm. No organized depolarization of atria, so no P-waves. Refractoryness of AV node determines how and when QRS complexes occur. Re-entry circuits compete to cause depolarization. Hemodynamic response depends on how dependant you are on atrial kick (nonexistant in this case) and what is resultant ventricular response.
What is paroxysmal AV nodal reentry (SVT)?
Re-entry of AV node causes AV depolarizations. P-wave occurs during QRS complex, so it is not visible. Hemodynamic consequences: not dangerous in healthy people, but very symptomatic (lightheadedness). Dangerous w/ underlying coronary disease.
What are premature ventricular contractions (PVC)?
Contractions which begin in the ventricle and result in skipped (or added) beats.
What is ventricular tachycardia?
Condition in which SA node is functioning normally, but not contributing to ventricular depolarization (AV dissociation). Dangerous b/c atria and ventricles are not functioning together so beats are not normal. Degenerates to ventricular fibrillation (fatal).
What is ventricular fibrillation?
Lethal rhythm of total electrical disorder in ventricle.
Heartblock
See notes
What is a disjunctional rhythm?
Heartbeat where pacemaker is in AV node or bundle of His.
What are the 3 coronary arteries?
1. Right coronary artery
2. left anterior descending (LAD) artery
3. left circumflex artery.
All 3 come from aorta.
What vessels supply the anterior wall of the left ventricle (its major pumping wall)?
The large branches of the Left Anterior Descending artery.
What vessels supply the lateral wall of the left ventricle?
The marginal branches of the Left Circumflex artery.
The left atrium, sinus node, and AV node are supplied by what artery?
Left Circumflex
What are the layers of arterioles in the heart?
1. Intima - contains endothelium, basement membrane, and internal elastic membrane
2. Media - smooth muscle
3. Adventitia - fibrous connective tissue
What pressure is most important for coronary profusion pressure?
Aortic diastole pressure
What changes in coronary blood flow occur in the Left Ventricle during systole and diastole?
Systole - contraction of ventricle restricts coronary blood flow.
Diastole - relaxation of coronary arteries, increased coronary profusion
What changes in coronary blood flow occur in the Right Ventricle during systole and diastole?
Similar to Left Ventricle, but much less degree of difference.
Why are subendocardial arterioles larger than those in the middle layer?
During systole, they are squeezed tightly from all sides, so they have hardly any blood flow and need to receive more blood.
At what level is myocardial blood flow regulated?
Almost entire at the local level, and depends on metabolic and blood flow demands of local myocardium.
How does oxygen demand affect blood flow?
Nearly all of oxygen is extracted during normal myocardial state, so exercise that increases oxygen demand must be met by increased coronary blood flow.
What are determinants of oxygen consumption?
1. Heart rate
2. Increased myocardial contractility
3. Ventricular wall tension
4. Peripheral ventricular resistance
5. Venous return
6. Systolic blood pressure
What are the effects of sympathetic stimulation?
Direct effects: Usually results in slight vasodilation
Indirect effects: Increased heart rate, myocardial contractility, and metabolism cause increased oxygen demand leading to increased coronary flow.
What are the effects of parasympathetic stimulation?
Direct: minimal effects
Indirect: decrease heart rate, decreased oxygen consumption leading to reduction of coronary blood flow.
What area of the heart do leads II, III, and aVF correspond to?
'contiguous leads' correspond to the inferior wall of the left ventricle (supplied by right coronary artery)
What area of the heart do leads V1 and V2 correspond to?
'septal leads' correspond to septum, which is supplied by septal perforators, from LAD
What area of the heart do leads V3 and V4 correspond to?
anterior wall of LV
What areas of the heart do leads V5, V6, I, and aVL correspond to?
lateral wall of LV
What is the definition of sinus rhythm on an EKG?
The P-wave precipitates a QRS complex.
STEMI (ST-segment elevated MI) is usually what kind of MI?
AMI, where thrombus totally blocks vessel.
NSTEMI (non-ST-segment elevated MI) is usually what kind of MI?
can be ischemia or MI. Determination is made based on levels of troponin in blood.
What does ST-segment depression on ECG indicate?
NSTEMI or unstable angina (check for troponins in MI)
What is the significance of T-wave inversions on an ECG?
MI or ischemia (look at troponins)
What coronary artery supplies the right atrium?
Right Coronary Artery
What coronary artery supplies the right ventricle?
Right Coronary Artery
What coronary artery supplies the inferior wall of the left ventricle?
Right Coronary Artery
What coronary artery supplies the posterior wall of the left ventricle?
Right Coronary Artery
What coronary artery supplies the anterior wall of the left ventricle?
Left Anterior Decending (diagonal branches)
What coronary artery supplies the ventricular septum?
Left Anterior Descending (septal perforators)
What coronary artery supplies the lateral wall of the left ventricle?
Left Circumflex (obtuse marginals)
What coronary artery supplies the left atrium?
Left Circumflex