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LEARNING OBJECTIVES

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LEARNING OBJECTIVES

Upon completion of the chapter, the reader will be able to:

  1. Describe the phases of cardiac action potential, compare and contrast cardiac myocyte ion currents corresponding to each phase, and explain the relationship between the cardiac action potential and the electrocardiogram (ECG).

  2. Describe the modified Vaughan Williams classification of antiarrhythmic drugs, and compare and contrast the effects of available antiarrhythmic drugs on ventricular conduction velocity, refractory period, automaticity, and inhibition of ion flux through specific myocyte ion channels.

  3. Compare and contrast risk factors for and features, mechanisms, etiologies, symptoms, and goals of therapy of (a) sinus bradycardia, (b) atrioventricular (AV) block, (c) atrial fibrillation (AF), (d) paroxysmal supraventricular tachycardia (PSVT), (e) premature ventricular complexes (PVCs), (f) ventricular tachycardia (VT, including torsades de pointes [TdP]), and (g) ventricular fibrillation (VF).

  4. Compare and contrast appropriate treatment options for sinus bradycardia and AV block.

  5. Compare and contrast mechanisms of action of drugs used for ventricular rate control, conversion to sinus rhythm and maintenance of sinus rhythm in patients with AF.

  6. Compare and contrast the advantages and disadvantages of warfarin and the non-vitamin K antagonist oral anticoagulants (NOACs) for prevention of stroke and systemic embolism in patients with AF.

  7. Discuss nonpharmacologic methods for termination of PSVT, compare and contrast mechanisms of action of drugs used for acute termination of PSVT, and compare and contrast appropriate treatment options for long-term prevention of PSVT recurrence.

  8. Describe the role of drug therapy for management of asymptomatic and symptomatic PVCs.

  9. Compare and contrast mechanisms of action of drugs used for treatment of acute episodes of VT, and describe options and indications for nonpharmacologic treatment of VT and VF.

  10. Design individualized drug therapy treatment plans for patients with (a) sinus bradycardia, (b) AV block, (c) AF, (d) PSVT, (e) PVCs, (f) VT (including TdP), and (g) VF.

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NORMAL AND ABNORMAL CARDIAC CONDUCTION AND ELECTROPHYSIOLOGY

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The heart functions via mechanical and electrical activity. Mechanical activity refers to atrial and ventricular contraction, the mechanism by which blood is delivered to tissues. When deoxygenated blood returns to the heart via venous circulation, the blood enters the right atrium. Right atrial contraction and right ventricular pressure changes result in delivery of blood to the right ventricle through the tricuspid valve. Right ventricular contraction pumps blood through the pulmonic valve and through the pulmonary arteries to the lungs, where blood becomes oxygenated. The oxygenated blood then flows through the pulmonary veins into the left atrium. Left atrial contraction and left ventricle (LV) pressure changes result in delivery of blood through the mitral valve into the LV, contraction of which results in pumping of blood through the aortic valve and to the tissues of the body.

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Mechanical activity is stimulated by the electrical activity of the heart. The heart possesses an intrinsic electrical conduction system (Figure 9–1). Normal myocardial contraction cannot occur without normal function of the heart’s electrical conduction system. Depolarization ...

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