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55 Cards in this Set
- Front
- Back
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Phases of action potential: Phase 0
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Rapid sodium entry (depolarization)
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Phases of action potential: Phase 1
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Transient potassium efflux, some chloride entry (repolarization)
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Phases of action potential: Phase 2
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Calcium entry (plateau)
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Phases of action potential: Phase 3
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Potassium efflux (rapid repolarization)
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Phases of action potential: Phase 4
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Resting membrane potential
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Absolute refractory period
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No action potential can occur no matter how great the impulse
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Relative refractory period
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Action potential can occur if impulse is of certain magnitude
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What is the relationship of the ventricular action potential to the ECG?
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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.
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What are the mechanisms of arrhythmias?
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1. altered automaticity
2. reentry |
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What are the mechanisms of altered automaticity?
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1. slowed diastolic depolarization
2. production of diastolic hyperpolarization 3. increased threshold level 4. dominance of ectopic pacemaker |
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What are the characteristics required for reentry?
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1. loop
2. unidirectional block 3. slow conduction 4. different refractory periods |
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What are the signs and symptoms of arrhythmias?
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1. palpitations
2. cardiac awareness 3. syncope/presyncope 4. hemodynamic compromise |
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What is sinus tachycardia?
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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.
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What is sinus bradycardia?
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Slow heartbeat <60 bpm. Often happens in runners. Hemodynamic consequences: usually asymptomatic, may cause lightheadedness.
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What are the types of premature atrial depolarizations?
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1. Abberent conduction (irregular)
2. Atrial flutter 3. Atrial fibrillation 4. Paroxysmal AV nodal reentry |
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What is abberant conduction?
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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.
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What is atrial flutter?
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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
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What is atrial fibrillation?
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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.
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What is paroxysmal AV nodal reentry (SVT)?
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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.
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What are premature ventricular contractions (PVC)?
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Contractions which begin in the ventricle and result in skipped (or added) beats.
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What is ventricular tachycardia?
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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).
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What is ventricular fibrillation?
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Lethal rhythm of total electrical disorder in ventricle.
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Heartblock
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See notes
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What is a disjunctional rhythm?
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Heartbeat where pacemaker is in AV node or bundle of His.
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What are the 3 coronary arteries?
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1. Right coronary artery
2. left anterior descending (LAD) artery 3. left circumflex artery. All 3 come from aorta. |
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What vessels supply the anterior wall of the left ventricle (its major pumping wall)?
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The large branches of the Left Anterior Descending artery.
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What vessels supply the lateral wall of the left ventricle?
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The marginal branches of the Left Circumflex artery.
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The left atrium, sinus node, and AV node are supplied by what artery?
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Left Circumflex
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What are the layers of arterioles in the heart?
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1. Intima - contains endothelium, basement membrane, and internal elastic membrane
2. Media - smooth muscle 3. Adventitia - fibrous connective tissue |
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What pressure is most important for coronary profusion pressure?
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Aortic diastole pressure
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What changes in coronary blood flow occur in the Left Ventricle during systole and diastole?
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Systole - contraction of ventricle restricts coronary blood flow.
Diastole - relaxation of coronary arteries, increased coronary profusion |
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What changes in coronary blood flow occur in the Right Ventricle during systole and diastole?
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Similar to Left Ventricle, but much less degree of difference.
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Why are subendocardial arterioles larger than those in the middle layer?
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During systole, they are squeezed tightly from all sides, so they have hardly any blood flow and need to receive more blood.
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At what level is myocardial blood flow regulated?
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Almost entire at the local level, and depends on metabolic and blood flow demands of local myocardium.
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How does oxygen demand affect blood flow?
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Nearly all of oxygen is extracted during normal myocardial state, so exercise that increases oxygen demand must be met by increased coronary blood flow.
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What are determinants of oxygen consumption?
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1. Heart rate
2. Increased myocardial contractility 3. Ventricular wall tension 4. Peripheral ventricular resistance 5. Venous return 6. Systolic blood pressure |
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What are the effects of sympathetic stimulation?
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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. |
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What are the effects of parasympathetic stimulation?
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Direct: minimal effects
Indirect: decrease heart rate, decreased oxygen consumption leading to reduction of coronary blood flow. |
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What area of the heart do leads II, III, and aVF correspond to?
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'contiguous leads' correspond to the inferior wall of the left ventricle (supplied by right coronary artery)
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What area of the heart do leads V1 and V2 correspond to?
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'septal leads' correspond to septum, which is supplied by septal perforators, from LAD
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What area of the heart do leads V3 and V4 correspond to?
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anterior wall of LV
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What areas of the heart do leads V5, V6, I, and aVL correspond to?
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lateral wall of LV
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What is the definition of sinus rhythm on an EKG?
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The P-wave precipitates a QRS complex.
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STEMI (ST-segment elevated MI) is usually what kind of MI?
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AMI, where thrombus totally blocks vessel.
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NSTEMI (non-ST-segment elevated MI) is usually what kind of MI?
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can be ischemia or MI. Determination is made based on levels of troponin in blood.
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What does ST-segment depression on ECG indicate?
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NSTEMI or unstable angina (check for troponins in MI)
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What is the significance of T-wave inversions on an ECG?
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MI or ischemia (look at troponins)
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What coronary artery supplies the right atrium?
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Right Coronary Artery
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What coronary artery supplies the right ventricle?
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Right Coronary Artery
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What coronary artery supplies the inferior wall of the left ventricle?
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Right Coronary Artery
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What coronary artery supplies the posterior wall of the left ventricle?
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Right Coronary Artery
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What coronary artery supplies the anterior wall of the left ventricle?
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Left Anterior Decending (diagonal branches)
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What coronary artery supplies the ventricular septum?
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Left Anterior Descending (septal perforators)
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What coronary artery supplies the lateral wall of the left ventricle?
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Left Circumflex (obtuse marginals)
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What coronary artery supplies the left atrium?
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Left Circumflex
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